OA preclinical studies using BMMSCs.
Osteoarthritis (OA) is one of the most common chronic, inflammatory, and degenerative diseases affecting the synovial joints, the hip, and the knee. OA is commonly managed clinically by treating pain with anti-inflammatory medicines using nonsteroidal anti-inflammatory drugs (NSAIDS) or analgesics. In severe OA patients, invasive knee replacement surgery is the last option. Treatment of OA using mesenchymal stromal cells (MSCs) has been widely explored due to their anti-inflammatory properties and chondrogenic differentiation potential. In this chapter, we comprehensively discuss in detail the in vitro OA potency development, OA preclinical studies, and clinical trials conducted using MSCs.
- pooled human bone marrow-derived mesenchymal stromal cells
- potency assay
- preclinical studies
- clinical studies
Common factors linked to osteoarthritis (OA) occurrence are increasing age (>55 years) and obesity . The gender also seems to play a major role, where the majority of OA patients are women and higher prevalence has been liked to menopause. Radiological evidence suggests that about 70% of women above the age of 65 years are affected by OA [2, 3]. Other factors such as genetic predisposition, extrinsic environmental factors, nutrition, and lack of exercise are reasons for the increased prevalence of OA. It has been reported by the World Health Organization (WHO) that 10–15% of the populations aged >60 years exhibit a certain degree of OA . It has been reported by the National Health Portal of India that 22–39% of the Indian population are affected by OA. As reported by the United Nations Organization (UNO), 130 million people will be affected by OA with over 40 million people with severe disability due to disease progression .
The etiology of OA is believed to be multifactorial. Some of the main reasons include the biomechanical disease progression due to the narrowing of space in the joints, bone hypertrophy, and formation of new osteophytes in the articular margins causing stiffness and pain in the joints. In addition, an imbalance in the synthesis and release of cytokines by chondrocytes in the disease state could be the main reason for the continual inflammatory state in the joint. During the initial stages of OA, catabolic interleukins (IL) such as IL-1α and IL-1β and tumor necrosis factor α (TNFα) increase inflammation affecting cartilage metabolism and homeostasis. TNFα is a proinflammatory cytokine implicated in the degradation of matrix proteins synthesized by chondrocytes and synoviocytes . Further, increase in the levels of interferon γ (IFNγ) in the joint worsens the inflammatory state and structure of the joint leading to degradation of proteoglycans such as sulfated glycosaminoglycans (sGAG) [5, 6].
2. Current treatment options for osteoarthritis
Currently, pain in OA is pharmacologically managed using nonsteroidal anti-inflammatory drugs (NSAIDS), opioids, and analgesics. Corticosteroid injections have also been used for relieving severe pain in OA patients. Recent attempts have been made to use TNFα blockers as recent studies have proven the significant role of TNFα in contribution to the pathogenesis of OA . Research by several groups has implicated the role of nerve growth factor (NGF) and its binding to tropomyosin receptor kinase A (trk A) which leads to downstream signaling and activation of peripheral and central pain molecules causing severe pain. The therapeutic efficiency of anti-NGF antibodies to block NGF or its antagonists has been studied by several groups for relieving pain. The pain-relieving effects of anti-NGF antibodies fasinumab and fulranumab manufactured by Regeneron Pharmaceuticals and Janssen Pharmaceutica, respectively, have been evaluated in phase III clinical trials . In addition to pain relief, efforts have been made to halt further cartilage damage using slow-acting symptomatic drugs such as chondroitin sulfate and glucosamine sulfate. Orally administered chondroitin and glucosamine have shown to relieve joint pain equivalently compared to NSAIDs. These molecules, intact or broken, could be absorbed into the matrix of the joint and prevent cartilage degeneration. Although glucosamine and chondroitin sulfate have been clinically proven to be safe, their therapeutic efficacy in protecting the cartilage matrix was found to the variable . In grade 4 OA (Kellgren and Lawrence classifications), patients are advised to opt for total knee replacement surgery . Alternatively, autologous chondrocyte implantation (ACI) has been suggested and reported to be successful. In the ACI method, the chondrocytes from patients are taken, culture-expanded in vitro, and then implanted back into the knees of patients. This procedure is invasive and has a lesser success rate than total knee replacement surgeries .
Apart from ACI, the efficacy of autologous platelet-rich plasma (PRP) in providing pain relief and promoting cartilage regeneration has been recently investigated by several groups . The PRP is rich in platelets that secrete several growth factors and cytokines such as platelet-derived growth factor (PDGF), hepatocyte growth factor (HGF), insulin-like growth factor 1 (IGF-1), vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE-2) . Several research groups have reported that intra-articular injections of PRP primarily reduced inflammation mediated by PGE-2, HGF, and IGF-1. IGF-1 synthesized and secreted by platelets is shown to prevent leukocyte infiltration into the joint space, thereby reducing the levels of IL-1β and TNFα in the synovial fluid . Overall intra-articular injection of PRP has been shown to maintain joint homeostasis. However, clinical trial data suggest that the effect of PRP seems to last for only 3 weeks and thereafter reduces. The symptoms of OA were seen to relapse after a period of 1 year. Although promising results were observed using PRP in the hydrogel, chitosan, or hyaluronic acid (HA) scaffolds , efficacy is yet to be shown in elaborate randomized clinical trials (RCTs).
3. Mesenchymal stromal cells
The history of mesenchymal stromal/stem cells (MSCs) dates back to 1960 when seminal studies conducted by Friedenstein showed the isolation of MSCs from bone marrow (BM) which were capable of forming ectopic bone in vivo. This was found to be a non-hematopoietic fibroblast-like, colony-forming cell which primarily supported hematopoietic stem cells in the perivascular niche . Owen and Friedenstein discovered that these cells were capable of differentiating into the osteogenic lineage . Subsequently, the multipotent plasticity of that bone marrow MSCs (BMMSCs) was identified and shown that they were capable of differentiating into osteocytes, chondrocytes, and adipocytes in vitro . In addition to the abovementioned three lineages, Caplan and colleagues demonstrated that these cells were capable of differentiating into cells of the muscle, tendons/ligaments, and connective tissue after which he coined the term “mesenchymal stem cells” . Bianco and Gehron Robey deduced that cbfa1 gene was the master regulator for directing the osteogenic fate of MSCs. Because of the ability of MSCs to form osteocytes, they named them skeletal stem cells . In 2006, the International Society for Cellular Therapy (ISCT) proposed the name multipotent mesenchymal stromal cells and defined that MSCs must adhere to the criteria of being plastic adherent; express surface markers CD105, CD73, and CD90; lack the expression of hematopoietic markers CD45, CD34, CD14 or CD11b, CD79α or CD19, and HLA-DR; and differentiate into osteoblasts, chondrocytes, and adipocytes under suitable conditions in vitro . In addition to their differentiation capacity, MSCs have been shown to elicit immunosuppressive and immunomodulatory effects on T lymphocytes, B cells, dendritic cells (DC), and natural killer (NK) cells either by cell-cell interactions or by secretion of anti-inflammatory molecules such as indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE-2), interleukin-4 (IL-4), interleukin-10 (IL-10), and transforming growth factor β (TGFβ) making them ideal cell types for treatment of diseases [21, 22, 23]. Because of their ability to differentiate into chondrocytes in vitro and with their anti-inflammatory and immunomodulatory functions, they were believed to be candidate cell type to treat diseases such as OA. MSCs have been isolated from over 18 different tissue sources. The most commonly used tissue sources for isolating MSCs apart from bone marrow are the adipose tissue, umbilical cord, placenta, and dental pulp. However, autologous or allogeneic BMMSCs are currently the most widely used cell type in clinical trials for various disease indications. They are considered the “gold standard” MSC type because of their extensive characterization that took place for over 5 decades.
4. Possible mechanism of action (MoA) of BMMSCs for treatment of osteoarthritis
The pathophysiology of OA is characterized by degradation of hyaline cartilage causing narrowing of joint space leading to subchondral sclerosis, subchondral cysts, hypertrophic chondrocytes, and formation of osteophytes. The friction caused by the rubbing of joints results in chronic pain in OA patients . Degeneration of cartilage extracellular matrix (ECM) may be caused due to the increase in the levels of proteolytic enzymes such as matrix metalloproteases (MMPs) and aggrecanases mediated by IL-1β and TNFα . BMMSCs express a wide range of properties that are anticipated to be beneficial for treating genetic, mechanical, and age-related degeneration in diseases such as OA. In our previous publication, we have in detail attempted to deduce the possible mechanism of action (MoA) of allogeneic pooled BMMSC population . Briefly, BMMSCs are known to be immunomodulatory in nature, primarily because of their potential to significantly suppress the proliferation of inflammatory T cells, monocytes, and dendritic cells either by direct cell-to-cell contact. In addition, they secrete a wide range of anti-inflammatory molecules such as PGE-2, IDO, IL1Ra, and IL-10 [26, 27]. BMMSCs influence the local osteoarthritic microenvironment by stimulating resident chondrogenic progenitor cells and promote their differentiation into mature chondrocytes mediated by secretion of bone morphogenetic proteins (BMPs) and TGFβ1 . BMMSCs are known to differentiate into chondrocytes in vitro using differentiation cues such as BMP-7 and TGFβ1. A similar mechanism could be involved in the differentiation of BMMSCs in vivo. With the increase in the levels of BMP-7 and TGFβ1 in the local joint milieu, mediated by a change in expression of master regulatory genes such as Sox9, HoxA, HoxD, and Gli3, BMMSCs could differentiate into chondrogenic progenitor cells (CPCs) in vivo. The CPCs further differentiate into chondroblasts characterized by definitive upregulation of collagen types II B, IX, and XI. Subsequently, the CPCs differentiate into mature chondrocytes regulated by balanced expression of collagen X (Col X) and synthesize the secretion of collagen II which is made of sGAG building blocks which maintain the structural integrity of hyaline cartilage . Very high expression of collagen X has been linked to hypertrophy of chondrocytes and formation of fibrous cartilage, and thus a regulated expression of Col X would likely result in deposition of hyaline cartilage . From the above-described multimodal MoA, it is clear that BMMSCs are an ideal cell population which could contribute significantly for an effective treatment of OA.
5. Advantages of using a pooled human BMMSC (phBMMSC, Stempeucel®) product for treating osteoarthritis
In the current therapeutic scenario, the common practice is to screen several individual donors, isolate MSCs, and characterize them based on their key characteristics such as their surface marker expression, tri-lineage differentiation potential, and immunomodulatory and paracrine properties [30, 31, 32]. It is inevitable that a product that is manufactured using a master cell bank (MCB) made from a single donor will result in exhaustion. Successively, a product that is made using another single donor MSC bank, although presumably similar in basic characteristics qualifying the identity and safety criteria, may not have the same functional attributes which may lead to varied therapeutic outcomes. Eminent scientific groups have demonstrated donor-to-donor variability in properties of MSCs such as their clonogenicity, growth kinetics, and differentiation potential . A comparative analysis of five different BMMSC populations showed significant variation in the proteomic profile of these cells. Only 13% similarity in the proteomic profile which included transcriptional and translational regulators, kinases, receptor proteins, and cytokines between the five BMMSC populations was found. A maximum of 72% similarity in the proteome was observed between two of the five analyzed cell populations . Disparities in clinical trial outcomes have been reported where BMMSCs derived from single donors have been used. A steroid-refractory acute graft-versus-host disease (SR-aGvHD) clinical trial conducted in both children (n = 25) and adults (n = 30) using BMMSC products derived from 92 HLA-matched and HLA-mismatched donors resulted in only 50% overall durable complete response, while the remaining patients did not respond or partially responded to the treatment . Similar variations with limited response rates were observed in a phase III GvHD trial conducted by Osiris Therapeutics using Prochymal® with only 35% complete response rate compared to 30% in the placebo arm . It has been suggested that improper selection of a BM donor and making a single donor-derived cell product could lead to substantial variations in therapeutic outcomes . In order to challenge this issue, some scientific groups have suggested pooling of BMMSCs from two or more donors in order to compensate for the variation and balance the properties between different donor cell populations. Samuelsson et al. showed that a two- or three-donor pooled BMMSC product could optimize the immunosuppressive properties of these cells in vitro . Later, Kuçi et al. showed substantial variability in the immunosuppressive properties of individual donor-derived BMMSCs (n = 8). On the contrary, a mesenchymal end product (MEP) made by pooling BMMNCs from eight donors resulted in a cell population that consistently suppressed an MLR in vitro . Subsequently, they went on to conduct a multicentric SR-aGvHD clinical trial in 51 children and 18 adults using MEP/MSC Frankfurt am Main (MSC-FFM, Obnitix®) cells and observed 83% overall response (complete response, 32%; partial response, 51%) . At Stempeutics Research Pvt. Ltd., we were the first group to develop an allogeneic pooled human BMMSC product called Stempeucel® using an established, robust pooling protocol and a two-tier manufacturing and banking system as previously described [41, 42]. Recently, we have published our comprehensive studies including in vitro chondrogenic properties and preclinical and clinical findings establishing the efficacy and safety of using Stempeucel® for the treatment of OA of the knee joint . In this study, we found that several manufactured batches of Stempeucel®, when differentiated into the chondrocyte lineage, downregulated the expression of the gene Sox9 and upregulated the expression of collagen type 2A (Col2A) gene confirming their differentiation into the chondrogenic lineage. The same Stempeucel® batches synthesized substantial levels of sGAG (30 ± 1.8 μg/μg GAG/DNA) which were estimated using a dimethylmethylene blue-based biochemical assay kit (Figure 1). These properties indicate that Stempeucel® could be a potential treatment option for treating OA.
6. Development of a potency assay for Stempeucel® intended to treat osteoarthritis
The US Food and Drug Administration (USFDA) describes potency assays as “The specific ability or capacity of the product, as indicated by appropriate laboratory tests or by adequately controlled clinical data obtained through the administration of the product in the manner intended, to effect a given result” (US-FDA, 21 CFR 600). For any cell therapy product (CTP) intended to be used for a particular indication, a specific, quantifiable, potency test or array must be developed. The development of a potency assay must begin with in vitro and preclinical studies based on the MoA of the CTP. The confirmation of the assay or the identified marker must be evaluated in every large-scale manufactured batch of the CTP during the progress of the phase I and phase II clinical studies. A quantifiable range for the potency test must be defined and implemented during the course of phase III clinical trial . In order to predict the efficacy of a CTP, either in vitro biochemical assays or biological assays or in vivo biological assessment could be implemented. For example, a company called TiGenix (Leuven, Belgium) has developed and adopted an assay matrix where an ex vivo polymerase chain reaction (PCR) array for autologous chondrocytes (ChondroCelect) is performed and ectopic cartilage formation is correlated to the histology sections of an orthotopic goat model where ChondroCelect is implanted [45, 46]. Jeong et al. have demonstrated that thrombospondin-2 (TSP-2) could be an effective marker to predict the chondrogenic efficiency of umbilical cord-derived MSCs (UC-MSCs). They demonstrated that UC-MSCs, through the TSP-2 secretion, can promote chondrogenesis via PKCa, ERK, P38/MAPK, and Notch signaling pathways . Recently, another group estimated the levels of TSP-2 to evaluate the chondrogenic potency of a UC-MSC product (Cellistem®OA, Cells for Cells, Brazil) intended to be used in phase I/phase II RCT for knee OA . Other scientific groups have shown that autologous culture-expanded chondrocytes could be embedded in collagen-1 and injected subcutaneously in nude mice to predict the potency of several bioactive molecules in promoting chondrogenesis . For the first time, we have developed a chondrogenic potency assay for an allogeneic pooled bone marrow-derived MSC product (phBMMSCs, Stempeucel®). Preliminarily, we culture-expanded and differentiated several Stempeucel® batches into the chondrogenic lineage using commercially available differentiation assay kits (Thermo Fisher Scientific, USA). To confirm the differentiation, we evaluated the Col2A mRNA expression in differentiated cells and compared them with the undifferentiated control cells. After observing a significant increase in the Col2A expression of differentiated cells, we enzymatically digested both the differentiated and undifferentiated cells to quantify the levels of sGAG synthesized by these cells using a 1,9-dimethylmethylene blue (DMMB)-based assay kit (Blyscan, Biocolor, UK). We further normalized the levels of sGAG with the amount of DNA from the same number of cells. We evaluated the sGAG levels in 20 batches of Stempeucel® of which 16 batches were cryopreserved in our older formulation (10% dimethyl sulfoxide (DMSO), 5% human serum albumin (HSA) and PlasmaLyte A) and also four batches of Stempeucel® cryopreserved in a new cGMP grade CryoStor 5 solution (CS5, BioLife Solutions). We observed a significant and consistent increase in the levels of sGAG in the differentiated cells compared to the undifferentiated cells (undifferentiated, 11.9 ± 4.6 GAG/DNA (μg/μg); differentiated, 31 ± 8.6 GAG/DNA (μg/μg; P < 0.0001; n = 20)) (Figure 1). Based on our results, we propose that the sGAG assay is a simple, quantifiable, and robust potency assay which could also be a part of a bigger potency assay matrix to predict the chondrogenic potency of therapeutic cells intended to treat cartilage defects.
7. Preclinical efficacy studies in OA
Many studies have demonstrated that MSCs are nontoxic and non-tumorigenic when tested in various animal models [50, 51]. Prior to evaluating the efficacy of Stempeucel® in an appropriate preclinical model of OA, we had earlier evaluated the preclinical safety and toxicity of Stempeucel® in rodent and non-rodent models. In the same study, we evaluated the feasibility of multiple routes of cell injection. Tumorigenic analysis in severe combined immunodeficient (SCID) mice showed that Stempeucel® is non-tumorigenic. In addition, the biodistribution kinetics of CM-DiI labeled Stempeucel® in the systemic circulation and also in muscle tissue were studied in both rats and mice .
It is important to demonstrate the efficacy of any cell therapy product in an animal model of disease before administrating the product in humans with the same disease. It is imperative to determine the suitability of using animal stem cells in animals or human stem cells in immunocompromised/immunocompetent animals. A common regulatory requirement is to have animal data for the same test product that is intended to be tested in humans. In our recently published work, we evaluated the efficacy of Stempeucel® in a monosodium iodoacetate (MIA)-induced OA model in Wistar rats. We demonstrated the dose-dependent efficacy of two Stempeucel® doses of 0.65 × 106 (25 × 106 human equivalent dose, HED) and 1.3 × 106 (50 × 106 HED) followed by an injection of hyaluronic acid (HA). A significant dose-dependent reduction in pain scores was observed in both low and high Stempeucel® doses compared to the HA alone and disease control group. Histological evaluation of joint tissue sections in all study groups showed significant improvement in proteoglycan staining in both low and high Stempeucel® administered groups indicating significant regeneration of the cartilage in both groups compared to the HA alone and disease control groups .
Similar to the animal model we used, other scientific groups have created articular cartilage defects in small animals, such as mice , rats [43, 53, 54], and rabbits [55, 56]. Smaller animal models are cost-effective and easy to house, and rodents are available in a variety of genetically modified strains with minimal biological variability [57, 58]. However, the small joint size, thin cartilage, altered biomechanics, and increased spontaneous intrinsic healing hamper the study of the regenerative capacity of stem cells and these mechanisms of healing which cannot be fully extrapolated to human cartilage repair [59, 60]. Rodents have mainly been used to assess the chondrogenesis of cell-based therapies by subcutaneous, intramuscular, and intra-articular implantations of cells . Of all small animals, the rabbit model is the most utilized model in cartilage regeneration studies because of the slightly larger knee joint size than rodents [55, 56]. Despite their limited translational capacity, small animals can be very useful as a proof-of-principle study and to assess therapy safety before moving on to preclinical studies using larger animals .
Large animal models play a more substantial role in translational research because of a larger joint size and thicker cartilage; however, their preclinical use is often hindered by high costs and difficulties in animal handling. A variety of large animal models have been used to investigate cartilage repair strategies, including horses , dogs , sheep [63, 64], goats , and pigs , each with their own strengths and limitations. We have listed some relevant published studies which have used autologous, allogeneic, or xenogeneic BMMSCs to treat OA induced by various methods (Table 1).
|Author/year||Animal||OA model||Cell type and dose||Vehicle||Study duration time points||Reference|
|Murphy et al. (2003)||Goat||ACLT-meniscectomy||10 × 106 Autologous (goat) BMMSC + HA||HA||12 and 26 weeks|||
|Frisbie et al. (2009)||Horse||Arthroscopic surgery||10.5 × 106 Autologous (horse) BMMSC||Saline||10 weeks|||
|Sato et al. (2012)||Pig||Spontaneous||7 × 106 Xenogeneic (human) BMMSC||HA/PBS||1, 3, and 5 weeks|||
|Song et al. (2014)||Sheep||ACLT-meniscectomy||10 × 106 Autologous (sheep) BMMSC||PBS||8 weeks|||
|Delling et al. (2015)||Sheep||Bilateral meniscectomy||20 × 106 Autologous (sheep) BMMSC||PBS||0, 1, 4, 8, and 12 weeks|||
|Singh et al. (2014)||Rabbit||ACLT||1 × 106 Autologous (rabbit) BMMSC||Culture medium||4 and 6 weeks|||
|Chiang et al. (2016)||Rabbit||ACLT||1 × 106 Allogeneic (rabbit) BMMSC||HA||6 and 12 weeks|||
|Diekman et al. (2013)||Mouse||Closed tibial plateau fracture||1 × 105 Allogeneic (mice) BMMSC||Saline/mouse albumin||8 weeks|||
|Suhaeb et al. (2012)||Rat||MIA injection||3.5 × 106 Allogeneic (rat) BMMSC||HA||3 and 9 weeks|||
|Kim et al. (2014)||Rat||ACLT-meniscectomy||1 × 106 Allogeneic (rat) BMMSC||Culture medium||3 and 6 weeks|||
|Yang et al. (2015)||Rat||ACLT-meniscectomy||0.5 × 106 Autologous (rat) BMMSC||PBS||3 weeks|||
|Gupta et al. (2016)||Rat||MIA injection||0.6 × 106 or 1.3 × 106 Xenogeneic (human) pooled BMMSC||PlasmaLyte A||4, 8, and 12 weeks|||
Based on the positive efficacy outcomes of our preclinical study, subsequently, we demonstrated the safety and optimal dose for efficacy in a phBMMSC product, Stempeucel®, in a randomized, double-blind, placebo-controlled dose-finding phase II clinical trial in Indian patients .
8. Clinical trials in osteoarthritis of the knee joint
8.1 Safety of mesenchymal stromal cells in clinical trials
Lalu MM et al. conducted a systematic review of clinical trials that examined the use of MSCs to evaluate their safety . A total of 36 studies having 1012 participants with different clinical conditions was evaluated. Eight studies were randomized control trials (RCTs) and enrolled 321 participants. Only prospective clinical trials that used the intravenous or intra-arterial route of administration in different age groups were analyzed. Meta-analysis did not detect an association with MSC administration and acute infusional toxicity, organ system complications, infection, and death. There was a significant association between MSCs and transient fever at or shortly after MSC administration which was not associated with long-term sequelae. Most importantly, the meta-analysis showed no serious adverse event due to the administration of MSCs and specifically found no association between MSCs and tumor formation. In another study, Peeters et al.  did a systemic review of the safety of intra-articular administration of culture-expanded stem cells. A total of 844 procedures (mean follow-up of 21 months) was analyzed. Four SAEs were reported—one infection following bone marrow aspiration (BMA) that resolved with antibiotics, one pulmonary embolism after 2 weeks of BMA, and two adverse events not related to the therapy. Other adverse events documented were increased pain/swelling and dehydration after BMA. In another review, a recent analysis of adverse events (AEs) in 2372 orthopedic patients treated with autologous stem cell therapies and followed up for 2.2 years has been published . The common AEs reported included post-procedure pain and pain due to progressive degenerative joint disease in under 4% of the population. Hence, we can conclude that the systemic administration of MSC including intra-articular administration is safe.
8.2 Efficacy of stem cells including mesenchymal stromal cells in clinical trials of osteoarthritis of the knee joint
Several clinical trials have been conducted using bone marrow mononuclear cells, adipose tissue-derived stromal vascular fraction (AD-SVF), adipose tissue-derived mesenchymal stromal cells (AD-MSCs), or bone marrow-derived mesenchymal stromal cells (BMMSCs) in OA of the knee joint. The list of the published clinical trials in chronological order is given in Table 2. Administration of the cells has been fairly standardized, with the cells being administered either directly intra-articularly or under ultrasound guidance. Few trials have been conducted using the arthroscopic method of administration with direct implantation of the cells alone or with a scaffold at the site of cartilage injury.
|Author/year||Sample size||Study design||Grade of OA||Cell type and dose||Control group||Outcome measures||Outcomes||Follow-up period||Reference|
|Wakitani (2002)||24||A single-arm control study||Stage I to stage II Ahlback changes||Auto BMMSC, 13 × 106 cells embedded in soluble collagen (n = 12)||High tibial osteotomy (n = 12)||Hospital for Special Surgery knee rating scale, arthroscopy and histology||No significant difference in clinical evaluations between the two groups, arthroscopy and histology showed partially hyaline cartilage-like tissue||16 months|||
|Centeno et al. (2008)||1||Case study||—||Auto BMMSC, 2.4 × 106 cells + 1 ml NC + 1 ml PRP||Nil||VAS, ROM, and MRI||Decreased VAS pain scores; increased the range of motion; MRI, statistically significant cartilage and meniscus growth||6 months|||
|Haleem et al. (2010)||5||Case series||Outerbridge grade III or grade IV||Auto BMMSC + PR-FG, 15 × 106 cells||Nil||Lysholm and RHSSK scores and X-rays and MRI||Lysholm and RHSSK scores showed statistically significant improvement, MRI of three patients revealed complete defect fill||12 months|||
|Nejadnik et al. (2010)||72||Cohort study||Lesion grade 3 or grade 4||Auto BMMSC||n = 12 each in BMMSC and chondrocyte group||ICRS, SF-36, IKDC, Lysholm knee scale and Tegner activity level scale||SF-36 showed physical role functioning improvement in the BMMSC group, no difference in other outcome measures||24 months|||
|Davatchi et al. (2011)||4||Single-arm study||Moderate to severe OA||Auto BMMSC, 8–9 × 106 cells||Nil||VAS pain score, time to walk and number of stairs to climb to produce pain, the resting time to induce the gelling pain, ROM and patellae crepitus||Walking time for the pain to appear improved for three patient, VAS pain score and number of stairs to climb improved for all patients, improvement in crepitus||6 months|||
|Saw et al. (2011)||5||Single-arm study||ICRS grade 3 or grade 4||Auto PBPC (8 ml) + HA/weekly injection × 5||Nil||Arthroscopy and histology||Arthroscopy showed articular cartilage regeneration and histologically showed hyaline cartilage||26 months|||
|Koh et al. (2012)||25||Case–control study||KL grade 3 or grade 4||Arthroscopic debridement + Auto AD-MSC, 1.89 × 106 cells + PRP||Arthroscopic debridement + PRP||Lysholm score, Tegner activity scale, and VAS scores||The clinical scores preoperatively were significantly poorer than those of the control group but at the last follow-up visit were similar and not significantly different between the two groups||18 months|||
|Orozco et al. (2013)||12||Case series||KL grade 2 to grade 4||Auto BMMSC, 40 × 106 cells||Nil||VAS score, Lequesne indexes, WOMAC scores, MRI T2 mapping||All clinical scores decreased significantly, MRI T2 mapping showed improvement of cartilage quality||12 months|||
|Koh et al. (2013)||18||Case series||KL grade 3 or grade 4||Auto AD-MSC, 1.18 × 106 cells + PRP||Nil||WOMAC score, Lysholm score, Tegner activity scale, and VAS scores, MRI (WORMS score)||WOMAC, Lysholm, Tegner, and VAS scores improved significantly, WORMS score in MRI improved significantly||26 months|||
|Van Pham et al. (2014)||21||Case series||KL grade 2 or grade 3||Auto SVF||Nil||VAS, Lysholm score, and MRI||VAS scores improved, Lysholm scores increased, MRI showed increased cartilage thickness||8.5 months|||
|Koh et al. (2014)||37 knees (35 patients)||Case series||KL grade 1 or grade 2||Auto AD-MSC, 3.8 × 106 cells||Nil||IKDC score, Tegner activity scale, and cartilage repair assessed using ICRS grading||IKDC and Tegner activity scale scores significantly improved, ICRS grades showed 2 of the 37 lesions (5%) were grade I (normal) and 7 (19%) were grade II (near normal)||26.5 months|||
|Koh et al. (2015)||30||Case series||KL grade 2 or grade 3||Auto SVF + PRP, 42 × 106 cells||Nil||Lysholm score, KOOS, VAS score, arthroscopic evaluation (n = 16)||Significant improvement in all clinical outcomes, 87.5% of patients (14/16) improved or maintained cartilage status||24 months|||
|Munar et al. (2015)||50||Case series||KL grade 2 to grade 4||Auto BMMSC, 40 × 106 cells||Nil||VAS, Lequesne and WOMAC indices, MRI (T2 mapping)||All clinical scores improved, T2 mapping, PCI decreased significantly||12 months|||
|Davatchi et al. (2016)||4||Case series||Moderate to severe OA||Auto BMMSC, 8–9 × 106 cells||Nil||VAS pain score, time to walk and number of stairs to climb to produce pain, the resting time to induce the gelling pain, ROM and patellae crepitus||All parameters still better than baseline at 5 years follow-up for three patients||60 months|||
|Soler et al. (2016)||15||Single-arm, open-label phase I/phase II trial||KL grade 2 or grade 3||Auto BMMSC, 41 × 106 cells||Nil||VAS score, questionnaire, QOL SF-36 questionnaire, Lequesne functional index and WOMAC score, MRI (T2 mapping)||The clinical scores improved, SF-36 showed improvement of parameters, T2 mapping showed signs of cartilage regeneration||12 months|||
|Sampson et al. (2016)||125||Retrospective case series||KL grade 3 or grade 4||Auto BMC + PRP (8 weeks apart)||Nil||VAS score, patient satisfaction scale||VAS score and patient satisfaction score improved in all patients||4.8 months|||
|Fodor and Paulseth (2016)||6 patients (8 knees)||Case series||KL grade 1 to grade 3||Auto SVF, 14.1 × 106 cells||Nil||VAS score, WOMAC score, ROM, TUG test, and MRI||VAS and WOMAC scores significantly improved, ROM and TUG improved, MRI showed no detectable structural differences||12 months|||
|Kim et al. (2016)||20 patients (24 knees)||Case series||KL grade 1 or grade 2||Auto AD-MSC, 4.4 × 106 cells||Nil||IKDC score, Tegner activity scale, MRI MOAKS and MOCART score||Clinical outcomes significantly improved, MOAKS and MOCART score significantly improved||24 months|||
|Pak et al. (2016)||3||Case reports||KL grade 3||Auto AD-SVF + HA + PRP, PRP repeated weekly × 3||Nil||FRI, ROM and VAS score, MRI||All clinical scores improved in three patients, MRI showed cartilage-like tissue regeneration||4.5 months|||
|Pers et al. (2016)||18||Open-label, phase I study||KL grade 3 or grade 4||Auto AD-MSC, low (2 × 106), medium (10 × 106), and high dose (50x106), 6 patients each||Nil||Safety, WOMAC, VAS, PGA, SAS and KOOS index, MRI, dGEMRIC in 6 patients||Safety established, low dose most effective, and all parameters improved as compared to baseline, dGEMRIC improved in three patients||6 months|||
|Koh et al. (2016)||80||RCT||ICRS grade 3 or grade 4||Auto AD-MSC + fibrin glue + microfracture, 5 × 106 cells (group 1)||n = 40 (group 2) (microfracture)||Lysholm score, KOOS, VAS score, MRI, cartilage repair tissue scoring system, arthroscopy and histology||MRI, better signal intensity for repair tissue in group 1 (80%) as compared to 72.5% in group 2; KOOS pain and symptom subscores, significantly greater for group 1; arthroscopy and histology, no significant difference||24 months|||
|Gupta et al. (2016)||60||Double-blind, phase II, RCT||KL grade 2 or grade 3||Allo BMMSC + HA, four doses (25, 50, 75, 150 × 106 cells)||n = 20 (placebo + HA)||Safety, VAS, ICOAP, WOMAC, MRI, WORMS score||Safety established; AE were predominant in the higher-dose groups; VAS, ICOAP, and WOMAC scores best in the lowest dose; MRI, no significant difference||24 months|||
|Lamo-Espinosa et al. (2016)||30||Phase I/phase II, RCT||KL grade 2 to grade 4||Auto BMMSC + HA, two doses (10 and 100 × 106 cells)||n = 10, (HA)||Safety, VAS score, WOMAC, MRI, WORMS||Safety established. VAS, WOMAC, and WORMS scores significant in high-dose group at 12 months follow-up||12 months|||
|de Windt et al. (2017)||10||Phase I/phase II single-center study||Modified Outerbridge grade 3 or grade 4||Allo BMMSCs +10 or 20% autologous chondrons||Nil||Safety, KOOS, VAS, MRI, second-look arthroscopy, histology||No SUSAR; KOOS and VAS scores improved significantly; MRI, showed complete filling of the defect; arthroscopy, effective defect fill, and integration in the surrounding tissue; histology, positive staining for both type I and type II collagen and proteoglycan||12 months|||
|Turajane et al. (2017)||60||RCT, single-center study||KL grade 1 to grade 3||3 groups, 20 each; first group (AAPBSC + PRP + G-CSF+ HA + MCS); second group (AAPBSC + PRP + HA + MCS); third group (control) (all given weekly × 3 injections)||20 patients, IA, HA alone||Avoidance of TKA intervention and WOMAC scores||TKA done in three patients in the control group but not in the cell group; WOMAC, all groups reached statistically significant improvements within the individual (intra) groups||12 months|||
|Shapiro et al. (2017)||25 patients, 50 knees||RCT, single-blind, placebo-controlled||Bilateral OA, KL grade 1 to grade 3||25 knees; 5 ml of Auto BMAC +10 ml of platelet-poor bone marrow plasma||25 knees; sterile saline, 15 ml||ICOAP, VAS scores, MRI, T2 mapping||No SAE, patients had a similar decrease in scores in VAS and ICOAP scores in both BMAC- and saline-treated arthritic knees||6 months|||
|Park et al. (2017)||7||Open-label, single-arm, phase I/phase II||KL grade 3 and ICRS grade 4||Two doses; Allo hUCB MSCs and HA hydrogel||Nil||ICRS cartilage repair, VAS, IKDC, MRI, histological findings||VAS and IKDC improved at 24 weeks and stable till 7 years; histology at 1 year showed hyaline-like cartilage; MRI at 3 years showed the persistence of regenerated cartilage||7 years|||
|Nguyen et al. (2017)||30||Placebo-controlled trial||KL grade 2 or grade 3||15 patients; AM + Auto AD (SVF + PRP; 107 SVF cells/ml)||15 patients, AM||Safety, WOMAC, Lysholm, and modified VAS scores, MRI||Safety established, WOMAC scores not significant between two arms at 6 and 12 months but significant at 18 months; increased Lysholm and VAS scores in the treatment group compared with the placebo; MRI, MRI demonstrated cartilage layer was thicker in the treatment group||18 months|||
|Pintat et al. (2017)||19||Single-arm study||Patellofemoral OA||IA AD-MSC + PRP||Nil||WOMAC, MRI, T2 mapping||WOMAC scores significantly lower in treatment arm than baseline; MRI, no change||12 months|||
|Russo et al. (2017)||30||Single-arm study||KL grade 1 to grade 3, grade > II (ICRS classification)||Auto microfragmented adipose tissue||Nil||VAS, KOOS, IKCD, subjective, Tegner Lysholm knee||IKDC and KOOS, improvement of 20 points; VAS and Tegner Lysholm score, improvement in 24 and 31 points, respectively||12 months|||
|Yokota et al. (2017)||13||Single-arm study||KL grade 3 or grade 4||IA Auto AD- SVF; 2.5 ml SVF containing 3 × 107 SVF cells/knee||Nil||VAS, JKOM, WOMAC||Scores improved by an average of 35% over baseline for JKOM, 32% improvement in WOMAC, and 40% for pain (VAS)||6 months|||
|Jo et al. (2017)||18||Single-arm study||Knee OA||Auto AD-MSC; 3 doses (10 × 106, 50 × 106, and 100 × 106 AD-MSCs)||Nil||WOMAC, KSS, KOOS, VAS, MRI, size and depth of the cartilage defect, the signal intensity of regenerated cartilage and cartilage volume||No TEAE; WOMAC, KSS, and KOOS, improved knee function; VAS, improved pain (statistical significance in high dose); MRI, improvements in all parameters||24 months|||
|Garay Mendoza et al. (2017)||61||Open-label, phase I/phase II controlled trial||Knee OA||Cell group, BM stimulation with subcutaneous administration of G-CSF (n = 30)||Control group, oral acetaminophen (n = 31)||VAS and WOMAC scores||BM-SC group showed significant improvement in knee pain and quality of life||6 months|||
|Kuah et al. (2018)||20||RCT, double-blind, placebo-controlled||KL grade 1 to grade 3||Randomized 4:1; Progenza (PRG) (Allo AD-MSC + culture supernatant); 2 groups, 8 pts. each, 3.9 or 6.7 million cells||4 patients, placebo administered||Safety, WOMAC, VAS, AQoL-4D, biomarkers (urine, C2C and CTX-II; serum, MIF and CTX-I; MRI, MOAKS score)||All patients experienced at least one TEAE; VAS and WOMAC, statistically significant within-group reduction from baseline in PRG group, no statistically significant differences at any time point between placebo and PRG groups; MRI, no decrease in lateral tibial cartilage volume while the placebo group showed a statistically significant cartilage loss||12 months|||
|Matas et al. (2018)||29||Phase I/phase II RCT, triple-blind trial||KL grade 1 to grade 3||Allo UC-MSC, single (20 × 106) or repeat dose (20 × 106 baseline and 6 months), 10 pts. each||9 patients, HA (baseline and 6 months)||VAS, WOMAC, MRI, WORMS score||No SAEs, repeat dose group had a significant decrease in VAS and WOMAC scores as compared to HA group, no changes in function subscale, SF36, and MRI||12 months|||
|Emadedin et al. (2018)||43||RCT, phase I/phase II, placebo-controlled, triple-blind||KL grade 2 to grade 4||Auto BMMSC, 40 × 106 cells (n = 19)||5 ml normal saline (placebo) (n = 24)||VAS, WOMAC, walking distance, painless walking distance, standing time and knee flexion compared||WOMAC, significant improvements in total score, pain, and physical function subscales and improvement in painless walking distance compared with placebo||6 months|||
|Khalifeh Soltani et al. (2019)||20||RCT, double-blind, placebo-controlled||KL grade 2 to grade 4||Placental-derived MSC, 50–60 x 106 cells (n = 10)||Normal saline (n = 10)||VAS, KOOS, knee flexion range of motion (ROM), MRI||No SAEs; significant knee ROM improvement at 2 and 24 weeks; VAS, no change; KOOS, improvement till 8 weeks; MRI, chondral thickness improved in about 10% of the total knee joint area AT 24 weeks||24 weeks|||
The first clinical study has been published way back in 2002 by Wakitani et al. . In this study of 12 patients who underwent high tibial osteotomy, BMMSCs at a dose of 13 million cells were embedded in collagen gel and transplanted into the cartilage defect and covered with autologous periosteum. The clinical improvement was not significantly different from the control group, but the arthroscopic and histological evidence was better in the transplanted group than the control arm. Since then many studies have been published, but still many contentious issues regarding cell therapy in OA are being discussed. We will try to discuss a few burning issues in this chapter:
Level of evidence regarding the use of MSC therapy in OA: Jevotovsky et al.  did a systemic review of 61 studies to look at the study evidence level, MSC protocol, treatment results, and AEs. The levels of evidence were defined by Marx et al. stating the level of evidence as level 1, randomized controlled trial; level II, prospective cohort study or observational study with dramatic effects; level III, retrospective cohort study or case–control study; level IV, case series; and level V, mechanism-based reasoning . These levels of evidence help physicians to come to clinical decisions. In this review, a total of 2390 patients in 61 studies was identified. Most of the studies used adipose-derived stem cells (ADSCs) (n = 29) or bone marrow-derived stem cells (BMSCs) (n = 30). The majority of the studies (57%) were level IV evidence which consists of therapeutic case series without comparative groups. Only five and nine studies were level I and level II evidence, respectively, in a total of 288 patients. Additionally, 11% were level III retrospective cohort studies, and 8% were level V single-patient case reports. The published data highlights the need for more level I and level II evidence to evaluate the role of MSC treatment in OA patients. However, the majority of the studies have reported positive results and an association between MSC therapy and symptomatic and radiologic improvement in these patients.
Best source of MSC for treatment of OA: Many studies have been published using different sources of MSCs, and there is no consensus as to which MSC type is the most effective in treating OA. Recently few studies have been published using SVF, bone marrow aspirate concentrate, and micro-fragmented adipose tissue, which further adds to the variability of this issue. The most common problem affecting the clinical outcome in OA is the tendency of MSCs to differentiate into fibrous-like tissue instead of hyaline cartilage . To eliminate or reduce chondrogenesis of the injected MSCs, one school of thought is to identify new sources of MSCs for cartilage repair. Recently synovium-derived stem cells have been used for OA study as it is believed that epigenetic memory may play a role and impact the specific lineage differentiation of MSCs . Hence, the use of synovium stem cells predicts a better outcome as chondrogenic differentiation is expected as it belongs to the same lineage. Fetal stem cells have higher plasticity and proliferation ability than adult stem cells. Hence, fetal tissue-derived stem cells, especially derived from the fetal cartilage, may show higher chondrogenic activity  and may be the ideal source of cells for OA. More controlled clinical trials are required to come to a conclusion as to which cell type may be the best choice for the effective treatment of OA.
Autologous or allogeneic source of MSCs: Most of the published trials used autologous MSCs to minimize immune response, which may lead to best clinical outcomes. Six of the studies in Table 2 attempted to investigate the potential application of allogeneic MSCs [43, 48, 93, 96, 103, 105] in OA. Recently in the last 2–3 years, most of the studies have attempted to use an allogeneic source of MSCs due to the ease of application. Further, no observed serious adverse effects indicate the safety of allogeneic cells in OA. Around 3000 patients have been administered allogeneic MSCs for different conditions, and no immune response has been reported to date . In a recently published trial using allogeneic umbilical cord-derived MSCs (UC-MSC) in knee OA, patients were randomized to receive hyaluronic acid at baseline and 6 months (HA, n = 8), single-dose (20 × 106) UC-MSC at baseline (MSC-1, n = 9), or repeated UC-MSC doses at baseline and 6 months (20 × 106 × 2; MSC-2, n = 9). No serious adverse events were reported. At 12 months of follow-up, MSC-2-treated group had significantly lower levels of pain [visual analog score (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), total score, and pain subscale] than HA group . Hence, it can be safely concluded that the use of allogeneic MSCs is safe and may be efficacious in OA.
The optimal dose of MSCs for best efficacy in OA: MSCs have been used in different doses in several clinical trials of OA (Table 2). The dose varied from as low as 1.18 million cells  to as high as 150 million cells . In a study by Koh et al. , 18 patients were given intra-articular injections with adipose tissue-derived MSCs in a mean dose of 1.18 million cells and platelet-rich plasma. At 26 months of follow-up, patients had significant improvement in VAS, Lysholm, and WOMAC scores. Magnetic resonance imaging (MRI) was evaluated using WORMS score and showed statistically significant improvement in the total and cartilage scores. In another dose-finding study, Pers et al.  recruited 18 patients who were treated with autologous AD-MSCs in three different doses: low dose (2 × 106 cells), medium dose (10 × 106 cells), and high dose (50 × 106 cells). After 6 months of follow-up, the procedure was found to be safe, and no serious adverse events were reported. Patients in the low dose had significant improvement in pain levels and functions as compared to baseline. In a dose-finding study conducted by Gupta et al. , four different doses (25, 50, 75 and 150 million cells) of allogeneic BMMSCs were used in a total of 60 patients. At 1 year of follow-up, the lower doses of 25 million had shown improvement in pain levels and function as compared to placebo and baseline. However in a study by Jo et al. , 18 patients were injected with autologous AD-MSCs in three different doses: 10, 50, and 100 million cells. At 2 years of follow-up, significant improvement in the Knee Society clinical rating system (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS), and VAS scores was seen in the highest dose of 100 million cells. As can be seen, most of the studies are single-arm studies without any control arm. Hence, to determine the most efficacious dose in OA, more randomized controlled, dose-finding clinical trials are required.
Selection of endpoints for the conduct of clinical trial: The FDA 2018 draft guidance document for OA regarding the development of structural endpoints for the development of drugs, devices, and biological products for treatment states that approvals for OA to date have been based on patient-reported outcome measures that assess pain and function. For the development of new product in OA, the goal of treatment should be inhibition of structural damage or targeting the underlying pathophysiology associated with OA or significantly delay the complications of joint failure and the need for joint replacement and also to reduce the deterioration of function and worsening of pain. All of the above may be taken into consideration for the development of endpoints for the study in OA .
Recently a meta-analysis was done to evaluate the different endpoints used to see the therapeutic efficacy and safety of MSCs for the treatment of patients with knee osteoarthritis . Five hundred eighty-two patients in 11 randomized controlled trials were included in this meta-analysis. It showed that MSC treatment significantly improved VAS and International Knee Documentation Committee (IKDC) scores after 24 months of follow-up compared to controls. MSC therapy also showed significant improvement in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne algofunctional indices (Lequesne), Lysholm knee scale (Lysholm), and Tegner activity scale (Tegner) at 12 or 24 months of follow-up. Hence, all the endpoints used currently for evaluation of efficacy in OA have shown significant improvement in different clinical trials:
MRI to evaluate cartilage regeneration: MRI has emerged as the leading method of imaging soft tissue structures around joints. An ideal MRI study for the cartilage should provide an accurate assessment of cartilage thickness and volume, show morphologic changes of the cartilage surface, show internal cartilage signal changes, and allow evaluation of the subchondral bone for signal abnormalities. Also, it would be desirable for MRI to provide an evaluation of the underlying cartilage physiology, including providing information about the status of the glycosaminoglycan (GAG) and collagen matrices . But, in actual, there is an absence of a standard system by MRI to evaluate cartilage regeneration. Many studies as given in Table 2 that have used MRI to evaluate cartilage regeneration are only qualitative. It is recommended to use validated imaging outcomes for cartilage regeneration for scientifically validating cell-based therapies, thus advancing the field. The most common parameters used for evaluation of cartilage regeneration by MRI are cartilage thickness in different points in all the compartments of the joint , cartilage volume , whole-organ magnetic resonance imaging score (WORMS) [43, 48], T2 relaxation time mapping [78, 83, 85, 95, 98], MRI Osteoarthritis Knee Score (MOAKS) score [88, 103], magnetic resonance observation of cartilage repair tissue (MOCART) score , and contrast-enhanced imaging technique known as delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) . Among all the parameters, T2 mapping and WORMS seem to be the most commonly used qualitative parameters used for evaluation of cartilage regeneration as it is sensitive to both changes in cartilage hydration and collagen fibril orientation. In a study by Orozco et al. , T2 relaxation measurements demonstrated a highly significant decrease of poor cartilage areas (on average, 27%), with the improvement of cartilage quality in 11 of the 12 patients. In another study by Rich et al. , a total of 50 patients was evaluated by T2 mapping at 12 months of follow-up after administration of autologous BMMSCs. The mean poor cartilage index (PCI) significantly decreased in 37 of 50 patients (74%), 10 remained the same (20%), and 3 worsened between 7 and 10% (6%). Hence, cartilage T2 mapping may be a sensitive marker for monitoring cartilage quality in subjects with knee OA as it allows us to accurately determine the grade of disorganization of the extracellular matrix.
Use of MSC alone or MSC with a scaffold for intra-articular injection in OA: When MSCs are injected intra-articularly alone, MSCs scatter widely in the joint, making it impossible to obtain consistent local concentration at the site of cartilage defect. Hence, with a hope to enhance their efficacy in cartilage regeneration, MSC implantation using scaffolds is being attempted in different clinical trials so that the cells are delivered to the site of interest. Compared to direct intra-articular injection, MSC delivery via a scaffold affords more control of proliferation, matrix production, and self-renewal which may help in the regeneration/repair of degenerated or damaged articular cartilage. Different scaffolds have been designed as the delivery system for the repair of articular cartilage. The different scaffolds which can be used are either made of poly-lactic-co-glycolic acids (PLGA) , collagen , gelatin , tricalcium (TCP) , poly-lactic acid (PLA) , hyaluronic acid (HA) , poly-glycolic acid (PGA), or fibrin glue . HA has been used frequently for implantation of MSCs into the joint. Many clinical studies (Table 2) have used HA as scaffold along with MSCs for implantation of the cells. Cartistem®, an approved drug by the Korean FDA for knee OA, is a combination of human umbilical cord blood-derived MSCs and sodium hyaluronate which is directly implanted at the site of cartilage injury into the joint by arthroscopy [96, 121]. Hence, cells with scaffold are the ideal combination for intra-articular delivery for cartilage degeneration. However, further studies are necessary to find optimal implantation vehicles that can result in the regeneration of articular cartilage.
8.3 Clinical trials in India
Few clinical trials using autologous or allogeneic MSCs or mononuclear stem cells in OA have been conducted in India. The trials registered in the Clinical Trials Registry of India are the two trials done by Stempeutics (one phase II trial completed and the other phase III trial ongoing). However, one published trial by Bansal et al.  for the single-arm study was done in India in which a total of 10 patients were treated with AD-MSCs. The patients were evaluated for safety, WOMAC, 6-minute walk test (6MWT), and MRI for cartilage thickness. The patients were followed up for 2 years. The total WOMAC and its subscale scores and 6MWT were significantly improved at all-time points till 2 years of follow-up. Cartilage thickness as determined by MRI improved by at least 0.2 mm in six patients, was unchanged in two patients, and decreased by at least 0.2 mm in two patients. The authors concluded that the procedure demonstrated a strong safety profile with no severe adverse events or complications reported.
8.4 Stempeutics Research experience in osteoarthritis of the knee joint
The off-the-shelf allogeneic, pooled BMMSC product developed by Stempeutics has completed one phase II clinical trial  and currently ongoing phase III trial in knee OA. In our completed phase II trial, we included patients of idiopathic OA in grade 2 or 3 of Kellgren and Lawrence radiographic criteria; patients who had self-reported difficulty in at least one of the following activities attributed to knee pain, lifting and carrying groceries, walking 400 m, getting in and out of a chair, or going up and down stairs; and patients who had been on stable medication, including nonsteroidal anti-inflammatory drugs/opioid analgesics for the past 3 months and in the age group of 40–70 years. All the criteria have to be present before being included in the study .
8.4.1 Phase II study in patients with osteoarthritis of the knee joint
The phase II results of Stempeucel® in OA patients have been published . Briefly, it was a double-blind, randomized, placebo-controlled, dose-finding study. In this study, 60 OA patients were randomized to receive different doses of Stempeucel®, 25, 50, 75, and 150 million cells or placebo. Stempeucel® was administered intra-articularly (IA) to the knee joint followed by 2 ml of hyaluronic acid (20 mg). The subjects were followed up for 2 years and were evaluated for safety parameters including AEs, and for efficacy parameters, VAS for pain, Intermittent and Constant Osteoarthritis Pain (ICOAP), WOMAC (total score and its subscales), and MRI were done to evaluate the WORMS score. The intra-articular administration of Stempeucel® was safe with knee pain and swelling as the most common AEs. Clinically relevant improvement in a persistent manner was seen in 25 million dose group in all subjective parameters (VAS, ICOAP, and WOMAC scores) (Figures 2–4). WORMS of MRI knee did not reveal any difference from the baseline and placebo group. It was concluded that intra-articular administration of Stempeucel® is safe and 25 million dose may be the most effective among the doses tested.
Currently, we are conducting a phase III trial in OA of the knee joint. This is a randomized, double-blind, multicentric, placebo-controlled study assessing the efficacy and safety of intra-articular administration of Stempeucel® in patients with osteoarthritis of the knee joint. One hundred and forty-six patients will be randomized to stem cell and placebo arm in a ratio of 1:1. Seventy-three patients will receive Stempeucel® (25 million) followed by 2 ml of hyaluronan, and 73 patients will receive only intra-articular injection of 2 ml of placebo followed by 2 ml of hyaluronan. The patients will be followed up for a total of 2 years after IMP administration. The details of the study are found in the Clinical Trials Registry of India (CTRI/2018/09/015785).
Osteoarthritis is a common disorder involving damage to synovial joint tissues particularly the cartilage and bone. Current treatments are mostly targeted at end-stage disease, but biological therapies including stem cell therapy show a promise for earlier intervention with a more prolonged benefit. With all the published clinical trial data, it is reasonable to expect that MSCs may prove to be an important therapy for OA. Pooled BMMSCs with their enhanced anti-inflammatory potential, immunomodulatory properties, and secretion of paracrine factors create the optimum environment for a controlled reparative pathway in the affected joint. Pooled BMMSC treatment, perhaps combined with other modalities like a scaffold, would be advantageous in providing treatment in early OA to slow disease progression, thus delaying or avoiding total joint replacement.
We thank Stempeutics Research Pvt. Ltd. and Mr. BN Manohar for proving the required funding for the relevant studies. We would like to thank Dr. Anish S Majumdar and Dr. Sudha Balasubramanian for their critical scientific inputs for potency assay development, preclinical studies, and clinical studies conducted by Stempeutics Research. We also thank Dr. Anoop Chullikana for his valuable inputs in the clinical studies.
Conflict of interest
The authors declare no conflict of interests.