Stem Cells

Stem cells are those which, given the right genetic signals, will divide and differentiate to, or develop into, the many different mature cells in the human body. These mature cells include, for instance, blood, bone skin together with some 200 other types that comprise the complete person.

The fertilized egg is said to be totipotential, from Latin totus, entire. It is able to generate by division and differentiation into a mature organisms.

Pluripotent cells (Plures is Latin for many) are those that can differentiate to all cells of the body.

A single cell is formed when a sperm fertilizes an egg. The cell divides into two after a few hours, the two cells divide again and so on. About four days later such division has created, in humans, 60 or so cells. The cells then begin to differentiate forming a hollow sphere called a blastocyst. The blastocyst has an outer layer of cells that will develop to create the placenta. The inner cell mass, consisting of pluripotent cells, will continue to differentiate to form virtually all the body’s tissues.

While the inner cell mass is able to produce many cell types, it is not able to create the cells necessary for fetal development.

Current research is examining the possibility of “stem cell therapies” for diseases, conditions and disabilities such as Parkinson’s and Alzheimer’s diseases, stroke and heart disease. There is considerable work to be done in overcoming the associated technological and ethical challenges.