Cartilage is a highly differentiated connective tissue that forms mechanical support to soft tissues and is important for bone development from fetal period to puberty. It is conformed by chondrocytes and extracellular matrix. It is generally believed that adult cartilage has no capacity to renewal. A delicate balance between cell proliferation and cell death ensures the maintenance of normal tissue morphology and function. Stem cells play essential roles in this process. Mesenchymal stem cells (MSCs) can give rise to multiple lineages including bone, adipose and cartilage. Nestin protein was initially identified as a marker for neural stem cells, but its expression has also been detected in many types of cells, including MSCs. In vivo, chondrocyte turnover has been almost exclusively studied in articular cartilage. In this chapter we will review the findings about the chondrocyte turnover in lung cartilage. We have presented evidence that there exist nestin-positive MSCs in healthy adulthood that participates in the turnover of lung cartilage and in lung airway epithelium renewal. These findings may improve our knowledge about the biology of the cartilage and of the stem cells, and could provide new cell candidates for cartilage tissue engineering and for therapy for devastating pulmonary diseases.
Part of the book: Cartilage Repair and Regeneration
Modern life implies a constant exposure of living organisms to many sources of radiation, especially electromagnetic fields (EMFs) generated by our technological devices. The question of whether or not EMFs in the non-ionizing extremely low frequency (ELF) range can induce genotoxic effects is currently a subject of interest. People of industrialized societies are commonly exposed to EMFs and waves in a very broad range of frequencies, including power lines, telecommunications, and domestic and industrial equipment. In this review, we present controversial evidence from our research group and others of genotoxicity induced by ELF-EMFs, since scientific community consider EMF devices produce marginal amounts of energy, which does not justify any DNA alterations, together with conflicting laboratory results and few epidemiological studies. However, in 2002 the International Agency for Research on Cancer (IARC) categorized ELF-EMFs as being potential carcinogenic and genotoxic agents to humans. The aim of the present chapter is to discuss the role of ELM-EMFs on human genotoxicity.
Part of the book: Genotoxicity