The most significant (and widely known) example of a multipotential stem cell (plasticity expression) lies in the stem cells of the bone marrow. Bone marrow adult stem cells have been known to be capable of aiding in the regeneration of skeletal muscle, osteoblasts, chondrocytes, adipocytes, liver cells, lung, alimentary canal, skin, and endothelial cells. Therefore, scientists are now thinking that perhaps it is not unique that bone marrow stem cells have this breadth of potential. Perhaps it is the tissue environment in which the stem cells are placed that dictates their potentials.

What are HSC's and what are their potentials?

A major population of bone marrow derived multipotential stem cells is that of Hematopoietic Stem Cells (HSC's). HSC's are evidently capable of regenerating the hematopoietic system, but they have also been shown to have multiple potentials. (Look at the path of an HSC) (4)

Is there any evidence of these potentials?

In one experiment using mice with infarcted cardiac muscle, human HSC's were injected into the mouse's blood stream. As a result, not only did the stem cells develop into erythrocytes, but also into cardiac muscle and endothelial tissue. Further studies show that HSC's possess further plasticity by being able to differentiate into cells that will aid in the regeneration of skeletal muscle. (5)

How do hMSC's fit in?

Another population of stem cells had been identified in the stem cells. They are known as hematpoietic mesenchymal stem cells (hMSC'). hMSC's are closely related to HSC's and mantain close contact with one another. These cells also coexist with other progenitor cells in the bone marrow. Several experiments have shown that in mice, hMSC's have the ability to engraft themselves onto the heart and differentiate into cardiac tissue. (6)

What are side population cells?

Another less significant, but equally interesting population of bone marrow stem cells is that of side population cells (SP's). Some believe that these cells are also present in skeletal muscle, therefore, scientists hypothesize that SP's express plasticity by contributing to hematopoiesis as well as skeletal muscle tissue. (4)

An experiment was perfromed in mice using SP's in which an mdx mouse had duchenne's muscular dystrophy. In this disease, skeletal muscles lack dystrphyn, resulting in the degeneration of skeletal muscle tissue. Scientists used flourescence to track SP's, and when injected into the tail of the mouse, the SP's seemed to restore the previously lacking dystrophyn. (6)