BACKGROUND:Silk fibroin, as a kind of high-performance biomaterial, has been widely used to construct scaffolds in bone tissue engineering. However, whether silk fibroin itself holds osteoinductive ability has not been reported yet. OBJECTIVE:To investigate the impact of different concentrations of silk fibroin solution on the proliferation and differentiation of rat bone marrow mesenchymal stem cel s (BMSCs) in vitro. METHODS:Silk fibroin and BMSCs were respectively isolated from silkworm cocoon and rat tibia, and were identified. Then, BMSCs were cultured in different concentrations of silk fibroin solution (0.01%, 0.05%and 0.1%), and the cell proliferation and the alkaline phosphatase activity were detected at different time points. RESULTS AND CONCLUSION:FTIR spectra of the sample extracted from silkworm cocoon showed distinct absorption peaks at 1 653 (amide I), 1 530.5 (amide II) and 1 212.3 cm-1 (amide III), which could be confirmed to be silk fibroin. Thus generated BMSCs showed long fusiform or astral morphology, positive for representative markers (CD29, CD44 and CD90) relating to mesenchymal stem cells, and could differentiate into osteocytes, chondrocytes and adipocytes under specific induction conditions, which further confirmed the extracted cells were BMSCs. Compared with the control group (without silk fibroin), 0.05% silk fibroin not only significantly promoted the cell adhesion, migration and proliferation, but also enhanced the alkaline phosphatase activity (P<0.01). With the increasing of the silk fibroin concentrations, the osteodifferentiation capacity of the BMSCs was progressively improved within the range of 0-0.05%and then declined at 0.01%of silk fibroin solutions. These results suggest that silk fibroin can promote osteogenesis, thus providing scientific evidence for developing silk fibroin-based tissue-engineered scaffolds.