Perivascular ancestors of adult multipotent stem cells.

Independent studies by numerous investigators have shown that it is possible to harvest multipotent progenitor cells from diverse dissociated and cultured fetal, perinatal, and principally adult developed tissues. Despite the increasingly recognized medical value of these progenitor cells, the archetype of which remains the mesenchymal stem cell, this indirect extraction method has precluded the understanding of their native identity, tissue distribution, and frequency. Consistent with other researchers, we have hypothesized that blood vessels in virtually all organs harbor ubiquitous stem cells. We have identified, marked, and sorted to homogeneity by flow cytometry endothelial and perivascular cells in a large selection of human fetal, perinatal, and adult organs. Perivascular cells, including pericytes in the smallest blood vessels and adventitial cells around larger ones, natively express mesenchymal stem cell markers and produce in culture a long-lasting progeny of multilineage mesodermal progenitor cells. Herein, we review results from our and other laboratories that suggest a perivascular origin for mesenchymal stem cells and other adult progenitor cells. Recent experiments illustrate the therapeutic potential of human pericytes to regenerate skeletal muscle and promote functional recovery in the diseased heart and kidney.