Effects Of PDMS Base Elasticity On Bone - Induced Differentiation Of Rat Bone Marrow Mesenchymal Stem Cells

BACKGROUNDBone marrow-derived mesenchymal stem cells (BMSCs) are multipotent adult stem cells with the potential to differentiate into a variety of cell types, including neural cells, vascular smooth muscle cells, osteoblasts, chondrocytes and adipocytes. Therefore, BMSCs are an important cell source for tissue repair and regeneration. Currently, study shows that physical characteristics of biomaterial and microenvironment around cells could direct the differentiation of BMSCs, especially matrix elasticity. Based on these findings, we suppose that alter the elasticity of bone substitute materials, could induce the BMSCs to differentiate to osteoblast, and enhance the therapy effects of bone grafts ultimately.OBJECTIVEIn this study, we aim to observe the role of different matrix elasticity in the differentiation of BMSCs on Polydimethylsiloxane(PDMS), and to make sure whether the stiff matrix is more suitable to induce BMSCs to osteogenic differentiation than soft matrix, and find the ideal range of elasticity.METHODS AND RESULTSTo investigate the role of different matrix elasticity in the differentiation of BMSCs, we utilize tunable elasticity PDMS which can be manipulated by adjusting the relative concentrations of cross-linking agent:1:10,1:20,1:35,1:60,1:80. The Young’s modulus was used to describe the elasticity of PDMS after measured by Atomic Force Microscope (AFM), that are 2170±340KPa、354±40KPa,50±12KPa,14±1KPa,4±0.1KPa. After surface modification, BMSCs was seeded on PDMS matrix, and 7 days after BMSCs cultured on the five different Young’s moduli matrix, we observed the differences of osteogenic differentiation of BMSCs by the method of Real-time PCR, Western blot, Immunofluorescence and Alkaline Phosphatase Assay. The osteogenic differentiation markers were Type I collagen, alphal (Col-I), osteocalcin(OCN), osteopontin(OPN) and bone morphogenetic protein 2(BMP2).The results show that PDMS is suitable for cell culture after surface modification, and by the means of altering the concentration of cross-linking agent, PDMS could mimic the majority of the tissues’　elasticity in human body. The cells cultured on PDMS were extended well, and related osteogenic differentiation markers shows differences between five matrixes. Among the five different elasticity, there is a significant difference of osteogenic marker expression on the group of 1:20, which the Young’s modulus is 354±40 KPa(P<0.05).CONCLUSIONIn summary, this study utilized PDMS, whose physical elasticity can be controlled, to investigate the BMSCs osteogenesis on five different Young’s moduli matrixes. We found that in the group of 354±40KPa, BMSCs show the higher expression of osteogenic markers. This may suggest that we can alter elasticity of bone substitute materials to the range of 354±40KPa, and enhance the therapy effects of bone grafts in the future.