MESENCHYMAL STEM-CELLS RESIDE WITHIN THE CONNECTIVE TISSUES OF MANY ORGANS

Previous studies have noted the presence of mesenchymal stem cells loc ated within the connective tissue matrices of avian skeletal muscle, d ermis, and heart. In these studies, clonal analysis coupled with dexam ethasone treatment revealed the presence of multiple populations of st em cells composed of both lineage-committed progenitor mesenchymal ste m cells and lineage-uncommitted pluripotent mesenchymal stem cells. Th e present study was undertaken to assess the distribution of these ste m cells in the connective tissues throughout various regions of the bo dy. Day 11 chick embryos were divided into 26 separate regions. Heart, limb skeletal muscle, and limb dermis were included as control tissue s. Cells were harvested enzymatically and grown using conditions optim al for the isolation, cryopreservation, and propagation of avian mesen chymal stem cells. Cell aliquots were plated, incubated with various c oncentrations of dexamethasone, and examined for differentiated phenot ypes. Four recurring phenotypes appeared in dexamethasone-treated stem cells: skeletal muscle myotubes, fat cells, cartilage nodules, and bo ne nodules. These results suggest that progenitor mesenchymal stem cel ls and putative pluripotent mesenchymal stem cells with the potential to form at least four tissues of mesodermal origin have a widespread d istribution throughout the body, being located within the connective t issue compartments of many organs and organ systems. (C) 1995 Wiley-Li ss, Inc.