Enhanced tenogenic differentiation and tendon-like tissue formation by tenomodulin overexpression in murine mesenchymal stem cells.

As a highly specific marker of tenocytes, tenomodulin (Tnmd) functions remain largely unexplored. We investigated the effect of Tnmd overexpression on tenogenic differentiation of murine mesenchymal stem cells (mMSCs) via plasmid-mediated overexpression in the C3H10T1/2 cell line. The results showed that overexpressed Tnmd could significantly enhance cell proliferation (p < 0.05) and the gene expressions of tenogenic-related molecules, including Tnmd, Scleraxis (Scx), collagens I, III and VI and decorin (p < 0.05), and significantly inhibit mMSCs differentiation towards the adipogenic, chondrogenic and osteogenic lineages (p < 0.05). Upon in vivo implantation with rat tail collagen gel subcutaneously in nude mice, Tnmd-overexpressed C3H10T1/2 cells formed neotendon-like tissue, which revealed a histological feature of wave-like dense collagen fibres and cells aligned in parallel. By contrast, a disorganized connective tissue structure with randomly distributed cells was observed in the control group. To further confirm this finding, a conditional Tnmd-overexpressing mouse model was established and the derived primary mMSCs could be induced to overexpress Tnmd with > two-fold upregulated gene expression (p < 0.05) by the treatment of doxycycline (Dox). Similarly, conditional overexpression of Tnmd in primary mMSCs also led to faster proliferation (p < 0.05), enhanced gene expression of tenogenic markers (p < 0.05) and the inhibited expressions of adipogenic and osteogenic markers (p < 0.05). The results of enhanced tenogenic differentiation and neotendon formation indicated that Tnmd may serve not only as a tenogenic marker but also as a positive regulator of MSCs tenogenic differentiation, which might be applied to MSCs-mediated tendon regeneration. Copyright © 2016 John Wiley & Sons, Ltd.