3D Printing Of Stem Cell Biomimetic Scaffolds For Cartilage And Spinal Cord Injury Repair

3D printing technology in combination with biomaterials,cells and other biological factors can be applied to fabricate personalized scaffolds with complex microstructure and biofunctions accurately and efficiently.In recent years,it has attracted widespread interests in the fields of tissue engineering and regenerative medicine due to its distinct advantages.However,some major challenges in 3D printing for tissue engineering still remain unsolved,such as:poor printability of biomaterials,mismatch of mechanical properties with natural tissues/organs,and limited biofunctions.In this PhD thesis,to address the current problems in the repair of cartilage and spinal cord injury,we have developed various 3D scaffolds using 3D printing technology to mimic different tissue microenvironments,which can effectively regulate the proliferation differentiation of stem cells.We also investigated the potential applications of these scaffolds in the repair of cartilage and spinal cord injury.The main contents are as follows:1.To construct dual biomimic scaffolds with biological function and mechanical property for the repair of articular cartilage,the poly(e-caprolactone)(PCL)framework enforced hydtoxybutyl chitosan-nanofiber hydrogel(HBC-NF hydrogel)with internal microchannels were developed to mimic the cartilage microenvironment and mechanical property by 3D printing technology,inducing human mesenchymal stem cells(hMSCs)growth and differentiation for articular cartilage repair.The hMSCs showed good proliferation in the HBC-NF hydrogels.Moreover,the HBC-NF hydrogels with increased surface roughness and area enhanced the pre-cartilaginous condensation of hMSCs,substantially promoting cartilage differentiation.Furthermore,The HBC-NF hydrogels were injected into the 3D printed poly(e-caprolactone)(PCL)framework with internal microchannels for improved mechanical support and substance exchange.The composite scaffold had similar mechanical performance to natural cartilage,and effectively promote cartilage formation in vivo.it holds great promise for potential applications in cartilage tissue engineering.2.Spinal cord injury(SCI)is a severe disabling injury.3D bioprinting in combination with biomaterials and neural stem cells(NSCs)has emerged as a promising approach to fabricate functional neural constructs with anatomically accurate complex geometries of spinal cord and spatial distributions of NSCs for spinal cord injury repair.Based on the above study that HBC had good printability,in this study,a novel biocompatible bioink consisting of functional chitosan,hyaluronic acid derivatives,and matrigel was developed.This bioink shows fast gelation(within 20 s)and spontaneous covalent crosslinking capability,facilitating convenient one-step bioprinting of spinal cord-like constructs.This printing strategy solved the existing limitations of NSC 3D bioprinting,such as cumbersome printing process,poor cell viability,and minimal cell-material interaction.Thus-fabricated scaffolds maintain high NSC viability(above 95%),and offer a benign microenvironment that facilitates cell-material interactions and neuronal differentiation for optimal formation of neural network.The in vivo experiment has further demonstrated that the bioprinted spinal cord-like scaffolds promoted the axon regeneration and decreased glial scar deposition,leading to significant locomotor recovery of the SCI model rats,which may represent a general and versatile strategy for precise engineering of central nervous system and other neural organs/tissues for regenerative medicine application.3.Based on the NSC 3D bioprinting,in the third part,we further explored the regulation of small molecular on differentiation of NSCs,and constructed a functional neural scaffold using 3D bioprinting technology,which mediated sustained release of small molecular,leading to enhanced neuronal differentiation of the encapsulated NSCs.In this study,the effect of O-linked ?-N-acetylglucosamine(O-GlcNAc)transferase inhibitor OSMI-4 on NSC differentiation and the molecular mechanism were studied.It was demonstrated for the first time that OSMI-4 induced a higher neuronal differentiation of NSCs,and it worked through inhibiting Notch signaling pathway.The bioink supramolecular hydrogels consisted of methacryloyl gelatin and acryloyl cyclodextrin for 3D bioprinted scaffold.The bioink had great printability,and the bioprinted scaffolds could improve cell-cell and cell-matrix interactions,facilitating the adhesion and proliferation of the laden NSCs.More importantly,the scaffolds suppled a stable release of hydrophobic OSMI-4,inducing encapsulated NSCs to differentiate into neurons.The in vivo study further showed that the functional bioprinted scaffold peomoted neuron regeneration and axon growth,thus led to significant improvement in hindlimb locomotion recovery of SCI rats.In brief,the current study may provide a new strategy for the effective treatment of spinal cord injury.