Drug-loaded Hydrogels For Promoting The Directional Differentiation Of Stem Cells And Its Application In Tissue Repair

Biomaterials combined with seed cells are often applied in the regeneration of tissues and organs,and have broad prospects in the field of tissue regenerative medicine.Stem cells need to be guided to differentiate into ideal cell types in the process of tissue regeneration to promote functional tissue recovery.The introduction of special biological or chemical drugs into biomaterials can regulate the growth and differentiation of stem cells.In this study,we construct tissue engineering hydrogels by constructing a tissue engineering hydrogel loaded with chemical small molecules or biomolecular drugs that can promote the directional differentiation of stem cells,to improve the expression of stem cells in osteogenic,chondrogenic,and angiogenic differentiation of stem cells respectively and also study the regulation effect of drugs and the molecular mechanism of differentiation.The drug-loaded hydrogels that can promote the directional differentiation of stem cells are applied to the regeneration and repair of bone,cartilage tissue,and cavernous tissue with rich blood vessels.The main contents are as follows:(1)Study on photo-crosslinked hydrogels hyaluronic acid and gelatin for three-dimensional culture of cellsIn this study,the photo-crosslinked hydrogels based on natural polymer gelatin and hyaluronic acid that can provide an extracellular matrix(ECM)microenvironment were prepared by chemical modification.The hydrogels have similar mechanical and biodegradable properties with soft tissues and show good cytocompatibility in the process of threedimensional cell culture with the survival rate of cells greater than 90%.(2)The host-guest drug-loaded hydrogels inducing stem cells to differentiate into chondrocytes and osteoblasts for repairing full-thickness joint damageIn this study,drug-loaded host-guest supramolecules have been used to construct hydrogels loaded with stem cell differentiation inducers to regulate the differentiation of stem cells into chondrocytes and osteoblasts respectively.In-vitro drug release experiments were conducted to study the sustained release effects of host-guest supramolecules on drug delivery.To explore the effect of chemical small molecule drugs on the gene and protein expression of stem cell osteogenesis and chondrogenic differentiation and its intrinsic signal molecular mechanism.The effects of small chemical molecules on the expression of genes and proteins in osteogenic and chondrogenic differentiation with the intrinsic signaling molecular mechanism have been studied.To simulate the structure of articular cartilage-subchondral bone,combining the above two kinds of stem cell differentiation-inducing hydrogels,a biphasic hydrogel that is tightly bound and can promote phase-specific differentiation of stem cells was prepared to promote the simultaneous regeneration of cartilage and subchondral bone and repair joint full-thickness injuries of rabbits in vivo.(3)3D-printed hydrogel scaffolds loaded with heparin by multi-layer charge self-assembly to promote angiogenic differentiation of stem cells3D printing and multilayer charge self-assembly technologies have been used to construct a hydrogel scaffold loaded with heparin on the surface.Heparin can bind and stabilize vascular endothelial growth factor(VEGF)and protect it from rapid degradation to promote the formation of vascular endothelial cells and vascular smooth muscle cells related to angiogenesis.The in-vitro and in-vivo experiments confirmed that the scaffold has good biocompatibility and histocompatibility.The heparin-loaded hydrogel scaffolds significantly increase the expression levels of angiogenesis-related genes and proteins in the surrounding tissues,reduce the production of surrounding fibrotic tissue and lead to more neovascularization in the implantation experiment in nude mice.(4)The heparin-loaded hydrogel scaffold combined with stem cells to promote the structural regeneration and functional reconstruction of corpus cavernosumThe rapid regeneration of the vascular network is essential for cavernous tissue repair.In this study,HIF-1α over-expressed muscle-derived stem cells(MDSCs)were designed by lentiviral transfection-based gene mutation,and after being seeded on the heparin-coated hydrogel scaffolds and implanted into the defect of rabbit corpus cavernosum for in situ repair.The scaffolds and stem cells have the synergistic effect of accelerating the structural reconstruction of corpus cavernosa and the reconstruction of vascular networks.Finally,the erectile,ejaculation and reproductive function of male rabbits have been recovered successfully.In conclusion,this study constructs tissue engineering hydrogels to promote the directional differentiation of stem cells by loading chemical small molecules or biomolecular drugs.Through the in-vitro cell experiment and in-vivo animal implantation experiment,the effects of these drug-loaded hydrogels in promoting stem cell differentiation and tissue repair have been studied from the levels of genes,proteins,and molecular mechanism.This study provides new guidance for the construction of tissue repair biomaterials that cooperate with stem cells.