Mesenchymal stem cells arrest intervertebral disc degeneration through chondrocytic differentiation and stimulation of endogenous cells.

Degenerative disc disease (DDD) is a common disease which affects millions of people. Autograft of the bone marrow derived mesenchymal stem cells (BMSCs) have been shown to have the ability to arrest degeneration in rabbit and canine intervertebral discs. In this study, we have used the mouse model to investigate the mechanism of degeneration arrest. BMSC from Egfp transgenic mice were injected into the degenerated murine intervertebral discs induced by annular puncture. We found that BMSC could arrest the progressive degeneration of the discs with significant regeneration of the nucleus pulposus (NP). In the regeneration, expression of proteoglycan genes were upregulated and extracellular matrix (ECM) progressively accumulated in the NP after BMSC injection. Combined in situ hybridization and immunohistochemistry revealed that BMSC underwent chondrocytic differentiation in the regeneration process. Interestingly, BMSC-induced an increase of endogenous notochordal cells in NP and expression of chondrocytic markers. In this study, we have firstly shown that the BMSC could arrest the degeneration of the murine notochordal NP and contribute to the augmentation of the ECM in the NP by both autonomous differentiation and stimulatory action on endogenous cells.