Proliferation and tenogenic differentiation of bone marrow mesenchymal stem cells in a porous collagen sponge scaffold

BACKGROUND Collagen is one of the most commonly used natural biomaterials for tendon tissue engineering. One of the possible practical ways to further enhance tendon repair is to combine a porous collagen sponge scaffold with a suitable growth factor or cytokine that has an inherent ability to promote the recruitment, proliferation, and tenogenic differentiation of cells. However, there is an incomplete understanding of which growth factors are sufficient and optimal for the tenogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs) in a collagen sponge-based 3D culture system. AIM To identify one or more ideal growth factors that benefit the proliferation and tenogenic differentiation of rat BMSCs in a porous collagen sponge scaffold. METHODS We constructed a 3D culture system based on a type I collagen sponge scaffold. The surface topography of the collagen sponge scaffold was observed by scanning electron microscopy. Primary BMSCs were isolated from Sprague-Dawley rats. Cell survival on the surfaces of the scaffolds with different growth factors was assessed by live/dead assay and CCK-8 assay. The mRNA and protein expression levels were confirmed by quantitative real-time polymerase chain reaction and Western blot, respectively. The deposited collagen was assessed by Sirius Red staining. RESULTS Transforming growth factor beta 1 (TGF-beta 1) showed great promise in the tenogenic differentiation of BMSCs compared to growth differentiation factor 7 (GDF-7) and insulin-like growth factor 1 (IGF-1) in both the 2D and 3D cultures, and the 3D culture enhanced the differentiation of BMSCs into tenocytes well beyond the level of induction in the 2D culture after TGF-beta 1 treatment. In the 2D culture, the proliferation of the BMSCs showed no significant changes compared to the control group after TGF-beta 1, IGF-1, or GDF-7 treatment. However, TGF-beta 1 and GDF-7 could increase the cell proliferation in the 3D culture. Strangely, we also found more dead cells in the BMSC-collagen sponge constructs that were treated with TGF-beta 1. Moreover, TGF-beta 1 promoted more collagen deposition in both the 2D and 3D cultures. CONCLUSION Collagen sponge-based 3D culture with TGF-beta 1 enhances the responsiveness of the proliferation and tenogenic differentiation of rat BMSCs.

Automated summary

By adding TGF-beta 1 in a collagen sponge-based 3D culture system, the proliferation and tenogenic differentiation of rat BMSCs can be enhanced. The 3D culture significantly improved the differentiation of BMSCs into tenocytes compared to 2D culture, with TGF-beta 1 playing a crucial role in this process.