Human Cord Blood-Derived Stem Cells in Transplantation and Regenerative Medicine

Abstract

Regenerative medicine can be defined as the process of restoring diseased or damaged tissue by replacing it with biological substitutes and this issue represents one of the main concerns of medicine. Stem cells are likely to be used in the future for cardiac, neurologic, hepatic, orthopaedic and other applications. The stem cell populations have proved to be highly proliferative lately as isolated from a variety of embryonic, foetal and adult tissues. Their increased capacity to self-renew and to unlimitedly differentiate into derivates of all germ layers in vitro and in vivo have rendered embryonic stem cells (ESCs) the main concern of tissue engineering research and regenerative medicine (Hyslop et al., 2005). However these cell lines originate from the inner cell mass of human blastocysts. Thus, the relation of ESCs to the human blastocyst will always stir ethical, moral and emotional debate over their use in research. Moreover, besides these ethical and political issues, another drawback concerning their clinical application is their lack of accessibility, technique difficulties in purification and manipulation as well as the risk for teratoma development (Fan et al., 2011). Consequently, though ESC therapy has just come into attention and there still are unknowns, its success might result in it being followed by alternative stem cell therapies (Rogers & Casper, 2004). Adult stem cells (ASCs) originate in a mature organism, including the brain, fat, skin, kidney, peripheral blood and bone marrow and they contribute to maintaining and repairing tissue that contain them. The adult-derived stem cells are also believed to have the ability to differentiate into tissues different from their tissue of origin (Krause et al., 2001; Jiang et al, 2002). Different from ESCs, ASCs can be easily harvested from various tissues, such as skin (Riekstina et al., 2008 as cited in Fan et al., 2011), bone marrow (BM) (Gastens et al., 2007 as cited in Fan et al., 2011) and adipose (Keiser et al., 2007 as cited in Fan et al., 2011), and might be employed in the clinical treatment of disorders of vulnerable vital organs. ASCs have the advantage that allows for small samples of tissues or even the patient’s own cells to be used for implantation, avoiding problems of tissue rejection. Moreover, adult cells do not involve the typical ethical issues of embryonic research. In spite of these advantages, they are not the first choice and this is because of several reasons such