Transforming growth factor β mediates communication of co-cultured human nucleus pulposus cells and mesenchymal stem cells.

Intervertebral disc (IVD) consists of surrounding tissue annulus fibrosus and central nucleus pulposus, which are partially degenerative in scoliotic IVDs. Successful regeneration of scoliotic alterations requires cognition of critical paracrine mediators of cell-to-cell contact in the IVD. In this work, we hypothesized that transforming growth factor β (TGF-β) is involved in the intercellular communication of nucleus pulposus cells (NPCs) and mesenchymal stem cells (MSCs). We observed that in cultured NPCs TGF-β1 stimulated COL1A1 expression, encoding collagen I, and in MSCs stimulated COL1A1 and SOX9 expressions. We subsequently co-cultured NPCs and MSCs together using direct and indirect transwell systems. The expression of miR-140 and miR-145 were decreased in co-cultured NPCs. We observed that direct co-culture system stronger than the indirect system decreased expression of three miRNA. The expression of COL1A1, ACAN, encoding aggrecan, and SOX9 genes was increased in MSCs co-cultured with NPCs. Co-cultures were incubated with two inhibitors of TGF-β type I receptor: SB-431542 and SB-525334. In co-cultured NPCs, SB-431542 and SB-525334 annulated downregulation of miR-140 and miR-145. In MSCs these inhibitors diminished stimulation of COL1A1, ACAN, and SOX9. We concluded that stimulation of COL1A1, ACAN, and SOX9 in co-cultured MSCs and regulation of miR-140 and miR-145 in NPCs were TGF-β-dependent and TGF-β is involved in the communication of NPCs and MSCs in co-culture.