OBJECTIVETo explore the effects of bone mesenchymal stem cells (BMSCs) in restoring the functions of degenerative nucleus pulposus cells (dNPCs).

METHODSThe animal models of degenerative nucleus pulposus were established by means of acupuncture and aspiration. The BMSCs as well as the normal and degeneratived nucleus pulposus cells of SD rats were isolated and cultured. The BMSCs/alginate gel complex and dNPCs/alginate gel complex were used for indirect co-culture in vitro, which was set as experiment group. The NPCs and dNPCs cultured alone as positive and negative controls. The cell growth conditions were observed by light microscopy, and suitable cells were selected to combine alginate gel stents and cultured in transwell plate. Seven days later, nucleus pulposus cells of each group were recycled, and the mRNA expressions of Collagen2, SOX 9, and Aggrecan were detected by RT-PCR, and the Collagen1, 2, and Aggrecan were detected by Western blotting and immunofluorescence.

RESULTSAfter non-contact co-culture for 7 days, the mRNA levels of Collagen2, SOX 9, and Aggrecan increased apparently in BMSCs+dNPCs group, while it was significantly lower in dNPCs sample (all P<0.05). The content of Collagen2 and Aggrecan detected by Western blotting in BMSCs+dNPCs group got close to NPCs sample, but it was significantly higher than dNPCs samples (all P<0.05), while the content of Collagen1in BMSCs+dNPCs group got close to NPCs samples, but it was significantly lower than dNPCs sample (P<0.05). Immunofluorescence results showed that cytoplasm was dyed red and the color near the caryon became dark in BMSCs+dNPCs group and dNPCs group;however, the colored scope of cytoplasm and the dark colored scope surrounding the caryon in BMSCs+dNPCs group was obviously larger than dNPCs group.

CONCLUSIONUnder a 3D non-contact co-culture system, BMSCs can promote the expression of epimatrix of the dNPCs, which shows that BMSCs can restore the functions of dNPCs of intervertebral disc to certain extent.