ABSTRACT
[ABSTRACT]AIM:Toexploretheeffectoftheelasticmodulusandsizesofliquidcrystal(LC)phasesonosteo-genic differentiation based on OPC/PU composite substrate by mimicking the microenvironment in rat bone mesenchymal stem cells (rBMSCs).METHODS: A series of composite substrates with different elastic modulus were constructed via modulation of LC content in the composites .The surface phase structure was observed by polarized microscopy , and the mechanical property was measured by a universal material testing machine .Furthermore, the laser confocal microscope was employed to observe the spreading , polarization and the cytoskeleton arrangement of the rBMSCs .The proliferation of rBM-SCs was evaluated by CCK-8 assay.The specific mRNA expression of osteogenic differentiation such as collagen Ⅰ, and osteopontin on the composite membranes was detected by real-time PCR.RESULTS:The size and number of LC phase in-creased and the elastic modulus of the composite substrates decreased with the increase of the LC content .The rBMSCs ex-hibited better characteristics of initial adhesion , spreading and proliferation on the OPC 10-PU and OPC30-PU in the early and medium culturing .The rBMSCs displayed higher expression of collagen Ⅰ and osteopontin on the OPC10-PU in the early and medium osteogenic induction , while the high expression of these osteogenic genes occured on the OPC 30-PU and OPC50-PU in later osteogenic induction .The emphasis of genetic expression was switched from collagen Ⅰin the early and medium osteogenic induction to osteopontin in the later stage .CONCLUSION:When the content of LC remained low in the composite substrates , rBMSCs mainly responded to the mechanical stimuli induced by substrate stiffness and exhibited distinguished cellular behaviors;with the increase in the LC content , rBMSCs had strong interactions with LC by sensing the viscoelasticity of LC , probably resulted from the contribution of both substrate stiffness and the viscoelasticity of LC phase .