| In tissue engineering,more and more studies have demonstrated that biomaterials and tissue engineering scaffolds can not only act as the niche for cell growth but also affect cell behaviors and further regulate the tissue repair process with their multiple types of bioactive cues,such as structural signals,chemical signals and mechanical signals.In recent years,with further understanding of the tissue development and regeneration process,researchers have gradually realized that the cell-cell communications between different types of cells also play important roles in tissue regeneration.Our previous studies indicated that various bioactive signals of biomaterials could make significant effects on the intercellular interactions,which further elucidated the potential mechanism of biomaterials affecting tissue regeneration.However,the detailed roles of biomaterial active cues in affecting cell behaviors and intercellular communications,and the mechanism by which biomaterial active cues influence intercellular communications are still unknown.Therefore,in this thesis,different roles of several kinds of typical biomaterial active cues,i.e.two kinds of two-dimension biomaterial structural signals(electrospun nanofiber film and titanium dioxide nanotubes(TNs)arrays),one type of three-dimension biomaterial structural signal(porous scaffold)and one type of biomaterial chemical signal(bioglass(BG)ion products),in affecting cell behaviors were studied.Results showed that the structural signals of the above two two-dimension biomaterials could affect cytoskeleton and further adjust cell differentiation in the main form of surface traction;the porous scaffold could accommodate cell sustained and rapid proliferation and maintain the original properties of cells with the interconnected porous structure;and BG ion products could affect cell proliferation and further adjust cell differentiation in the form of active ions.In addition,the results showed that the structural signals of TNs arrays and porous scaffold and the chemical signals of BG ion products could affect the communications of human bone marrow stem cells(HBMSCs)and human umbilical vein endothelial cells(HUVECs),and further regulate their differentiation.It has been reported that the paracrine effects play crucial roles in cell-cell interactions.During paracrine communications,cells can guide and regulate the growth behaviors of recipient cells by secreting signaling molecules and delivering those molecules to recipient cells via the extracellular environment.Exosomes are a type of nano-scaled vesicles with sufficient signaling substances which are actively secreted and released by living cells,and play vital roles in cell-cell paracrine communications.Therefore,in this thesis,we further verified the crucial roles of exosomes in HBMSCsHUVECs interactions and investigated the effects of BG ion products on the exosome production behaviors of these two types of cells.Results showed that,when the exosome secretion of cells was inhibited,the interactions of HBMSCs-HUVECs were prominently reduced and the enhancement effects of BG ion products acting in the interaction of HBMSCs-HUVECs were obviously weaken,resulting in the significantly decreased differentiation capability of co-cultured HBMSCs and HUVECs.Further studies showed that BG ion products could not only remarkably promote HBMSCs and HUVECs to secrete exosomes,but improve the capability of the two types of cells to capture and internalize exosomes when they acted as recipient cells.In addition,BG ion products could strikingly enhance the capability of HBMSCs-derived exosomes to facilitate vascularization and the capability of HUVECs-derived exosomes to facilitate osteogenic differentiation without affecting the basic vesicular characteristics of the secreted exosomes.Based on these findings,the molecular mechanism of BG ion products in affecting cell exosome secretion was further explored.Results showed that,when BG ion products were enhancing the exosome secretion of HBMSCs,the gene expression and protein synthesis of neutral sphingomyelinase-2(n SMase2)and Rab27 a in HBMSCs were significantly upregulated,followed with enhanced endogenous n SMases and Rab GTPase signal pathways,respectively,which further promoted the formation of intraluminal vesicles(ILVs)and accelerated the transportation,docking and merging of the mature multivesicular bodies with the plasma membrane and eventually resulted in the potentiated exosome release in the extracellular environment.In addition,BG ion products could selectively regulate the levels of various signaling molecules loaded into ILVs,such as downregulating the micro RNA(mi R)-342-5p level and upregulating mi R-1290 level,thus enabling the HBMSCs-derived exosomes to facilitate vascularization with heightened capability.Generally,these results suggest that the chemical signals of BG ion products can significantly promote the exosome release of cells and simultaneously reinforce their biological function by enhancing the endogenous signal pathways which regulate exosome secretion.In addition,the chemical signals of BG ion products can also strikingly heighten the capability of recipient cells for exosome capture and internalization.Based on these,BG ion products enhance the intercellular paracrine effects thus further potentiating the cell-cell interactions.Taken together,the results in this thesis further illustrate the important roles of biomaterial active cues in affecting cell behaviors,and elucidate the mechanism by which BG ion products influence intercellular interactions from the prospective of exosomes,which provide a new thought to study the effects of biomaterial active cues on cell-cell interactions and a simple and feasible engineered strategy to enhance cell exosome production and simultaneously modify their biological function. |
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