Cells for New life
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Types of Stem Cells

Cord Blood Stem Cells

The umbilical cord is the basic life-line support for all newborns. It is the essential tube in which all nutrients and nourishments are transported from the mother to the embryo. The human umbilical cord begins to form in the first 5 weeks of pregnancy. The allantoises, a membrane formed out of the gut, contains umbilical vessels that attach the fetus to the developing placenta. Blood vessels typically develop from the yolk sac, which will then combine with the umbilical vessels. The amnion or the membrane surrounding the amniotic fluid envelops the allantoises and the yolk sac, forming the developing umbilical cord. In the following months leading up to birth, the umbilical cord begins to enter deeper into the abdomen of the fetus. The umbilical cord consists of two arteries and one vein arranged in a helical structure. The two arteries of the umbilical cord spiral around the umbilical vein, making them stiffer and more difficult to rupture. Opposite to the arteries and veins of the human heart (except for the pulmonary arteries), umbilical cord arteries and veins carry deoxygenated blood to the placenta and oxygenated blood from the placenta to the developing fetus, respectively. The three vessels of the umbilical cord are embedded in a connective tissue gelatinous base known as the Wharton‘s Jelly which insulates the umbilical cord. A striking difference between the umbilical arteries and vein is observed in the endothelial cells at 10 weeks gestation. The endothelial cells of the arteries become richer in glycogen. At 15 weeks gestation, venous endothelium contains the most amount of rough endoplasmic reticulum and thereafter decreases until almost none is seen by mid-pregnancy. Arterial endothelium contained rough endoplasmic reticulum that progressively increased over the course of the pregnancy. 

In the late 1980s and early 1990s, physicians began to recognize that blood from the human umbilical cord and placenta was a rich source of hematopoietic stem cells. This tissue supports the developing fetus during pregnancy, is delivered along with the baby, and, is usually discarded. Since the first successful umbilical cord blood transplants in children with Fanconi anemia, the collection and therapeutic use of these cells has grown quickly. Umbilical cord blood recipients – typically children – have now lived in excess of eight years, relying on the HSCs from an umbilical cord blood transplant. There is a substantial amount of research being conducted on umbilical cord blood to search for ways to expand the number of hematopoietic stem cells and compare and contrast the biological properties of cord blood with adult bone marrow stem cells. There have been suggestions that umbilical cord blood contains stem cells that have the capability of developing cells of multiple germ layers (multipotent) or even all germ layers, e.g., endoderm, ectoderm, and mesoderm (pluripotent).

Hematopoietic stem cells are multipotent and have the capability to self-renew and differentiate into all mature blood cells including myeloids such as granulocytes, monocytes, leukocytes, erythrocytes, and megakaryocytes, and lymphoids such as T-lymphocytes and B-lymphocytes. Hematopoietic stem cells in umbilical cord blood are similar to those in bone marrow and peripheral blood in their capacity for differentiation. They can self-renew and they contain erythroid and granulocyte-macrophage progenitor cells when examined in an in vitro colony assay.