Gamma-cross-linked nonfibrillar collagen gel as a scaffold for osteogenic differentiation of mesenchymal stem cells

• We prepared gamma-cross-linked nonfibrillar collagen gels and unirradiated fibrillar gels.
• The mesenchymal stem cells (MSCs) differentiated into osteoblasts on both collagen gels.
• The MSC-derived osteoblasts deposited calcium on both collagen gels.
• Bone formation by osteoblasts was more efficient in the nonfibrillar gels than the fibrillar gels.
• The MSCs had a unique elongated shape and adhered to each other on the nonfibrillar gels.

We fabricated a transparent nonfibrillar collagen gel using gamma irradiation (5 kGy) and cultured rat mesenchymal stem cells (MSCs) on both the gamma-irradiated collagen gel and on unirradiated fibrillar collagen gel. Cells attached well and proliferated with high viability on the surface of both gels. The cells cultured on the gamma-irradiated nonfibrillar gel had a unique elongated shape and adhered to each other in culture. After 21 days of culture in dexamethasone-containing culture medium, the contents of bone-specific osteocalcin and calcium on the gamma-irradiated nonfibrillar gel were 1.4 and 1.9 times higher than those on fibrillar collagen gel, respectively. These data show that osteogenic differentiation of MSCs was promoted more efficiently on the gamma-cross-linked nonfibrillar gel than on the fibrillar gel and demonstrate the potential of the gamma-irradiated collagen gel for use in bone tissue engineering.