Differentiation of rodent bone marrow mesenchymal stem cells into intervertebral disc-like cells following coculture with rat disc tissue

This study aimed to evaluate whether rat mesenchymal stem cells (rMSCs) could be differentiated in vitro into disc-like cells by coculturing with intervertebral disc tissue. rMSCs were cultured with rodent intervertebral disc for up to 30 days in transwell plates. The differentiation of rMSCs was evaluated by immunostaining, Western blot, real-time RT-PCR, Northern blot, and electron microscopy. The potentials of multilineage differentiation and proteoglycan and collagen synthesis were also investigated. rMSCs underwent morphological changes to form three-dimensional micromasses and expressed collagen-2, aggrecan, and sox-9 at RNA and protein levels after 14 days of coculture. These changes were not detected in the samples of rMSCs cultured alone. Cocultured rMSCs also showed other characteristic features of disc-like cells, including the extracellular matrix formation, and proteoglycan and collagen synthesis. In addition, cellular contact between cocultured rMSCs and disc tissue was observed by electron microscopy. Committed rMSCs still retained their differentiation ability into mesoderm lineages of adipocytes or osteocytes when the local environment was altered. This study supports that MSCs are a promising source for cell therapy and tissue engineering in disc regeneration, and highlights that rMSCs can be induced into nucleus pulposus-like cells in vitro under the direct influence of intact disc tissue.