Masumi Akita

By Masumi Akita

Part of the book: Approaches to Bronchitis

By Keiko Fujita and Masumi Akita

Angiogenesis is the process of growth of new blood vessels. Tumor angiogenesis plays pivotal roles in tumor development, progression, and metastasis. The conventional notion of tumor vasculature is that new tumor blood vessels sprout from preexisting vasculature near the tumor; hence, tumor endothelial cells are derived from normal endothelial cells. However, recent evidence suggests that CD133‐positive cancer stem cells (CSCs) in glioblastomas generate tumor endothelial progenitor cells, which further differentiate into tumor endothelial cells. This chapter offers an overview of current knowledge on the role of CSCs in tumor angiogenesis. Furthermore, we discuss our recent discoveries related to human hepatoblastoma stem cells. Future efforts to elucidate the characteristics of tumor angiogenesis should enable the development of effective new anti‐angiogenic therapies.

Part of the book: Physiologic and Pathologic Angiogenesis

By Tomoko Takahashi, Keiko Fujita and Masumi Akita

Tissue explants of skeletal muscles, brain, kidney, liver and spleen from mice were cultured using collagen gel. Electron microscopic observation revealed that formation of capillary tubes with pericyte-like cells occurred only from the tissue explant of skeletal muscles. The capillary tubes formed in the collagen gel were positive for tomato lectin and platelet/endothelial cell adhesion molecule (PCAM)-1 antibody. Formation of capillary tubes in the rat was more predominant than in the mouse. Plasmalemmal vesicles were clearly observed in the capillary tubes from rat tissue explant. Muscle fiber-type differences were also observed. In the soleus muscle, the formation of capillary tubes was predominant than the tibialis anterior muscle. Using this culture model from the rat soleus muscle, effects of α-isoproterenol (β-adrenergic receptor agonist) and low-frequency electrical stimulation were examined on the formation of capillary tubes and fine structures of skeletal muscle explant. The formation of capillary tubes was promoted by α-isoproterenol administration. At low-frequency electrical stimulation, the formation of capillary tubes was inhibited. Both α-isoproterenol and electrical stimulation reduced the degeneration of skeletal muscles. This culture method of skeletal muscles may provide a useful model that can examine the effects of various drugs and physical stimulations.

Part of the book: Physiologic and Pathologic Angiogenesis