Regulation Of An Osteon-like Concentric Microgrooved Surface On Osteogenesis And Osteoclastogenesis

As one of the significant physical characteristics of the surface properties of scaffolds,topological structure has been demonstrated to play a crucial role in regulating various behaviors of cells,including adhesion,proliferation,migration and differentiation.With the development of micro-nano processing technology,it is possible to construct controllable specific micro-topological structures(micro-patterns)on the surface of materials,which has become an important technical strategy to study the interaction between surface topological structures and cells.However,most of the existing studies are focused on the basic topological structures such as micro-nano-grooved,micro-islands and micro-pillar,and ignore the bionics of the key topological structure characteristics of natural bone tissue.Osteon is called Haversian system,which is the structural unit of natural cortical bone.It is composed of multiple concentric circles of haversian bone spiraling around the haversian canal and the bone cells are distributed along the interlamellar.Considering that the final goal of bone healing is to restore the original cortical bone configuration,an osteon-like micropatterned surface comprising concentric circular microgrooves that induces a corresponding cellular arrangement may change the behaviors of cells relevant to the repair process.In the present study,a micropatterned polycaprolactone(PCL)surface comprising a series of concentric circular microgrooves was fabricated by combining photolithography with the melt-casting method to mimic the concentric structure of an osteon on a two-dimensional setting.Bionic construction of concentric circles,one of the key topological features of osteon,was realized on a two-dimensional plane.By culturing mouse mesenchymal stem cells(MSCs)and osteoclast progenitor cells(RAW264.7 cells)on the osteon-like concentric microgrooved surface,the effects of this micropatterned surface on the osteogenesis of MSCs and the osteoclastogenesis of RAW264.7 cells were systematically investigated.Osteoclastogenic differentiation was significantly inhibited in RAW264.7 cells on the fabricated osteon-like concentric microgrooved surface compared to that on the parallel linear microgrooved and flat surfaces,as indicated by the downregulated expression of key osteoclast-specific function genes(TRAP,CATK and MMP9).The lower activity of TRAP and less formation of TRAP-positive multinucleated giant osteoclasts.Further investigation indicated that RANK-NF?B signaling pathway may have been involved in mediating the inhibited osteoclastogenesis of RAW264.7 cells by the osteon-like concentric microgrooved surface.In addition,the osteon-like concentric microgrooved surface greatly modulated the osteoclastogenic-related paracrine secretion of mMSCs(RANKL,M-CSF and OPG),despite its small effect on the osteogenesis of mMSCs.In the proposed research,we successfully construct prepared the osteon-like concentric microgrooved structure on two-dimensional setting.We also demonstrate it can promote the osteogenic differentiation of MSCs,effectively inhibit osteoclastogenesis in RAW264.7 cells,regulate the expression of paracrine factors related to osteoclast differentiation of mesenchymal stem cells,as well as further inhibit the osteoclast differentiation of RAW264.7 cells.These results illustrate crucial functions and the broadened application prospects of the osteon-like concentric microgrooved structure in the surface construction of bone repair scaffold materials.