Stem cells isolated from adult rat muscle differentiate across all three dermal lineages.

Adult stem cells capable of differentiating into phenotypes from all three dermal layers were isolated from adult rat muscle. Stem cells were obtained by enzymatic digestion, followed by primary culture in Eagle's minimum essential medium +10% preselected horse serum. When the cells reached confluence, they were released by trypsin, filtered to remove differentiated myotubes, and then slow frozen in 7.5% dimethylsulfoxide to -80 degrees C. Thawed cells were the stem cells and were induced to differentiate with the nonspecific differentiating agent dexamethasone at concentrations of 10(-10)-10(-6) M. After a 6-week treatment with dexamethasone, the cells were assayed by immunohistochemistry for phenotypes of the mesodermal, ectodermal, and endodermal lineages. Examples of mesodermal phenotypes identified were as follows: bone, cartilage, and skeletal, smooth, and cardiac muscle. Ectodermal phenotypes identified were as follows: neurons and oligodendrocytes. Hepatocyte phenotypes identified represented the endodermal lineage. All the phenotypes were observed only with treatment with dexamethasone. However, nestin was observed in the absence of dexamethasone and may be a marker for uncommitted pluripotent stem cells. The results show that adult muscle contains pluripotent stem cells capable of differentiating across all three dermal lineages. Such cells could be used in the context of tissue engineering.