Stem cells in the umbilical cord

Abstract

Stem cells are the next frontier in medicine. Stem cells are thought to have great therapeutic and biotechnological potential. This will not only to replace damaged or dysfunctional cells, but also rescue them and/or deliver therapeutic proteins after they have been engineered to do so. Currently, ethical and scientific issues surround both embryonic and fetal stem cells and hinder their widespread implementation. In contrast, stem cells recovered postnatally from the umbilical cord, including the umbilical cord blood cells, amnion/placenta, umbilical cord vein, or umbilical cord matrix cells, are a readily available and inexpensive source of cells that are capable of forming many different cell types (i.e., they are "multipotent"). This review will focus on the umbilical cord-derived stem cells and compare those cells with adult bone marrow-derived mesenchymal stem cells.

Fig. 1

Generalized stem cell lineage concept. The lineage is characterized by a self-maintaining “parent” true stem cell population that resides within a specialized niche microenvironment, which aids the regulation of stem cell division or quiescence (nondividing). Derivative cells (called progeny or daughter cells) are of two types: symmetric division produces two identical daughter cells to expand or maintain the stem cell population; asymmetric division produces an identical daughter and a specialized cell (a differentiated cell). The differentiated cell is an intermediate type of precursor cell, termed the transient dividing population. The number of divisions of the intermediate precursor is fairly tightly regulated by microenvironment and inborn regulation factors. The intermediate precursors are thought to have a limited proliferative capacity. Further tissue-specific specialization continues form the intermediate precursors, producing specialized populations with a commitment to a progressively more specialized (differentiated) fate. The end points are fully differentiated cells that are nondividing and that live for various, tissue-specific periods prior to senescence or damage that leads to cell death. In some tissues, the naturally occurring cell loss produces various feedback signals that trigger normal cell replacement via amplification/differentiation of either stem cells or the intermediate precursors.