Angiogenesis in the field of tissue engineering has attracted significant attention. Graphene oxide has become a promising nanomaterial in tissue engineering for its unique biochemical properties. Therefore, herein, a series of chitosan (CS)/graphene oxide (GO) hydrogel scaffolds were synthesized by crosslinking CS and GO at different concentrations (0.1, 0.5, and 1.0 wt.%) using genipin. Compared with the CS hydrogel scaffolds, the CS/GO hydrogel scaffolds have a better network structure and mechanical strength. Then, we used endothelial progenitor cells (EPCs) extracted from human umbilical cord blood and cocultured these EPCs with the as-prepared scaffolds. The scaffolds with 0.1 and 0.5 wt.%GO showed no considerable cytotoxicity, could promote the proliferation of EPCs and tube formation, and upregulated the expressions of CD34, VEGF, MMP9, and SDF-1 in EPCs compared to the case of the scaffold with 1.0 wt.%GO. This study shows that the addition of graphene oxide improves the structure of chitosan hydrogel and enhances the proliferation activity and angiogenic capacity of EPCs.

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Objectives: Insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein 2 (BMP-2) both promote osteogenesis of bone marrow mesenchymal stem cells (BMSCs). IGF-1C, the C domain peptide of IGF-1, and P24, a BMP-2-derived peptide, both have similar biological activities as their parent growth factors. This study aimed to investigate the effects and their mechanisms of polypeptides IGF-1C and P24 on the osteogenic differentiation of BMSCs. Methods: The optimum concentrations of IGF-IC and P24 were explored. The effects of the two polypeptides on the proliferation and osteogenic differentiation of BMSCs were examined using the Cell Counting Kit-8 (CCK-8), Alkaline phosphatase (ALP) staining, ALP activity assay, alizarin red S staining, qPCR, and western blotting. In addition, specific pathway inhibitors were utilized to explore whether p38 and JNK pathways were involved in this process. Results: The optimal concentrations of action were both 50 g/ml. IGF-1C and P24 synergistically promoted the proliferation of BMSCs, increased ALP activity and the formation of calcified nodules and upregulated the mRNA and protein levels of osterix (Osx), runt-related transcription factor 2 (Runx2), and osteocalcin (Ocn), phosphorylation level of p38 and JNK proteins also improved. Inhibition of the pathways significantly reduced the activation of p38 and JNK, blocked the expression of Runx2 while inhibiting ALP activity and the formation of calcified nodules. Conclusions: These findings suggest IGF-1C and P24 synergistically promote the osteogenesis of BMSCs through activation of p38 and JNK signal pathways.