Embryonic stem (ES) cells were first derived from pluripotent cells present in the inner cell mass of mouse blastocysts. They are characterized by their ability to differentiate into multiple cell types representative of all three embryonic germ layers in vivo or in vitro and by the ability to form chimeras when introduced into embryos. The ES cell progeny contribute to all somatic cell lineages and to the germ lines in chimeric mice, and they can be propagated indefinitely without loss of euploid chromosomal complements. Thus, they have potential as a suitable cell source for replacement therapy in human cellular degenerative diseases. endep tablets
Recently, ES cell lines were established from primate embryos, including rhesus, marmoset, and cyno-molgus monkeys as well as humans. The derivation of human ES (hES) cells, together with recent developments in hES cell culture, such as embryoid body (EB) formation and differentiation in vitro, demonstrate that hES cells, like their mouse counterparts, can differentiate into cells of multiple lineages in vitro, including neurons and glial cells. Whereas the potential application of hES cells for transplantation in patients with neurodegenerative diseases or spinal injuries is clearly recognized, clinical application of ES cell-based therapy should be preceded by a thorough understanding of the growth and developmental fate of ES cells and their derivatives in vivo. Questions regarding the potential of transplanted primate ES cells to become neoplastic, their functional capacity, and the potential for immune rejection must be answered first in a nonhuman primate model. In this regard, rhesus macaques resemble humans closely in anatomy, physiology, and genetic makeup, and monkey ES cell lines are available.