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. Author manuscript; available in PMC: 2012 Jan 1.
Published in final edited form as: Crit Rev Eukaryot Gene Expr. 2011;21(1):29–41. doi: 10.1615/critreveukargeneexpr.v21.i1.30

FIGURE 4.

FIGURE 4

Schematic indicating current theories concerning the origin of cells of the nucleus pulposus (NP). Although it is well established that the notochord (NC) gives rise to large NP cells during embryogenesis, there is discord concerning the origin of small chondrocytic cells in the adult disc. As the NC contains both small spindle-shaped cells as well as large vacuolated cells, we hypothesize that both the large vacuolated cells (LVC) and chondrocyte-like cells (CLC) of the NP are derived from the notochord. These cells then undergo self renewal to maintain cellular homeostasis of the NP tissue. It is possible that LVC may differentiate into CLC. It is known that the perinotochordal sheath (PNS) gives rise to both endplate (EP) chondrocytes and annulus fibrosus (AF) cells. Some researchers are of the opinion that in the adult, endplate chondrocytes and inner annulus fibrosus cells give rise to CLC at the same time replacing LVC. There is debate that loss or replacement of LVC in the nucleus pulposus initiates disc degeneration. Reproduced with permission.23