Dynamic Mineralization and Calcitriol Supplementation Promote Osteogenic Differentiation on Silk Scaffolds In Vitro
摘要
Biomimetic composite materials offer a promising solution for designing tissue engineering approaches for bone reconstruction. Silk fibroin, a natural fibrous polymer, possesses superior mechanical properties and when paired with hydroxyapatite (HA), the mineral component of native bone tissue, is a promising bone scaffold material. In the present study, we design a porous silk scaffold using salt-leaching for interconnected porosity and mineralize the scaffold by depositing HA via a perfusion bioreactor. While mineralized polymeric scaffolds are osteoconductive, we further assess the efficacy of calcitriol (the bioactive form of vitamin D) supplementation instead of supraphysiological doses of morphogenetic growth factors to induce osteogenesis. The combinatorial benefit of calcitriol at two different dosages (15 and 75 µg/ml) in promoting osteogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs) in conjunction with mineralized silk scaffolds is assessed in vitro over 21 days. We demonstrated that the generated mineralization on the silk scaffolds was similar to biological apatite (Ca/P ratio of 1.81 ± 0.13). The present study found that the mineralized silk scaffold enhanced osteogenic commitment of hMSCs compared to both mineralized collagen and non-mineralized silk scaffolds. Calcitriol supplementation had an additive effect on this phenomenon. Osteogenic commitment was enhanced at the lower dosage of calcitriol (15 μg/ml) but limited at the higher concentration (75 μg/ml). These findings suggest that a mineralized silk scaffold system with appropriate calcitriol supplementation could be a model system for tissue regeneration of bone defects with the potential for composite grafts with other silk-based constructs towards multi-tissue musculoskeletal regeneration.