Spinal Cord-Derived Progenitor Cells are Prevalent and Active

Horner, P.J., A.E.Power, G.Kempermann, H.G.Kuhn, T.D.Palmer, J. Winkler, L.J.Thal, and F.H. Gage. 2000. Existence of progenitor cells throughout the intact adult rat spinal cord. J.Neurosci. 20(6): 2218-2228.

Adult spinal cord contains NG2-expressing glial progenitor cells that continue to divide after the period of post-natal gliagenesis. NG2 is a surface proteoglycan that thought to be expressed on progenitor cells that are bi-potent, giving rise to astrocytes and oligodendrocytes. Progenitor cells are derived from stem cells but typically have reduced self renewal capacity and differentiation capability. Unlike stem cells, progenitor cells are rapidly dividing. In the adult spinal cord, glial replacement is thought to slow down or end shortly after birth. In the above experiments we analyzed the number of dividing cells in the adult spinal cord and found there to be significant cell division even in older age groups. Perhaps most surprising is the finding that these cells are likely glial progenitor cells because they express NG2 (A). During cell division these progenitor cells have short uni- or bipolar processes (C). By 1 day these processes extend and the cells assume a bipolar shape (B above). By 4 weeks, NG2-expressing progenitor cells exhibit a complex multipolar morphology reminiscent of an oligodendrocyte (B below). These findings suggest that the adult spinal cord harbors highly active progenitor cells that may be used as a resource for spinal cord repair. In the future, we must better understand the physiological role for these cells and how they are altered by injury or degeneration.