细胞砖构建“软骨发育模板”再生血管化下颌骨及其体内重塑的机理研究

Engineering artificial bone grafts provides important alternative to autologous bone grafts which has long been limited by donor shortage.However, conventional synthetic bone grafts or tissue engineering grafts always rely on tough, slowly degrading biomaterials or dense extracellular matrices produced in vitro, which greatly impeded their in vivo remodeling as well as integration with host vasculature and bone, thereafter abrogated their clinical success, especially for large, segmental bone defects. Our project proposed to harness the bone remodeling potential of hypertrophic carftilage template, and engineering such a cartilage intermediate by using “Cell Bricks” technology, such an artificial graft simulates the cartilaginous structure while owns in vivo cell recruiting ability. We believe fast cell recruitment and appropriate mechanical loading are the critical factors that influence the host remodeling and cell differentiation of tissue engineering grafts, as well as opening structure for cell infiltration, scaffolding materials with adequate degrading rate as well as flexible material which could sense the environmental forces would be essential to graft design. We have fabricated porous tubular scaffolds by using elastomeric polymer poly glycerol-sebacate (PGS), via salt-leaching route, in addition, the electrospinning polycaprolactone (PCL) fibrous sheath wrapped outside of the grafts and PCL rings significantly stabilized the mechanical strength of the tubular inner support, so that the PRP gel solidified cell bricks constructs could be resistant to surgical implantation and compression from bone defect site. In our proposals, we will further rationalize structural parameters of cartilaginous template so that cell recruiting efficiency including vascularization and ossification could be promoted. Furthermore, we will explore the spatiotemporal distribution of recruiting cells, and tissue sources of these cells. Additionally, the relationship between cartilage template structure and differentiation of recruiting cells will be unraveled. Based on above research experience, vascularized bone grafts with optimized structure and biomaterials will pave the road for their remodeling in situ, which also will crack the bottle neck of the present regenerative medicine.

传统组织工程骨移植体中，慢降解材料以及难以快速血管化的内部结构，制约其在体内的功能性重塑以及与宿主的融合，限制了大范围骨缺损修复上的成功率。本项目从促进体内细胞募集、充分利用宿主自身重塑能力出发，构建具有开放结构及稳定颌骨形态的软骨发育模板。以细胞砖技术构建的脱细胞幼稚软骨基质提供了内皮细胞的快速募集通道，其梯度降解为组织基质沉积创造了空间;贴附于其表面生长且诱导分化的肥大软骨细胞聚集体提供骨性重塑的生化因素;采用快速降解弹性内支撑体赋予形态和力学稳定性，最终再生出具有高度细胞化及基质的血管化骨组织。本项目旨在优化软骨发育模板结构，提高血管化以及成骨效率，获得软骨内成骨的新策略。深入研究细胞募集的时空规律以及组织来源，明确细胞分化与移植体结构以及软骨基质之间的关系。本研究希望解决传统骨移植体体内融合性差、血管化效率低以及骨再生缓慢等瓶颈问题，为节段性血管化颌骨移植提供新的技术理念。

传统组织工程骨移植体中，慢降解材料以及难以快速血管化的内部结构，制约其在体内的功能性重塑以及与宿主的融合，限制了大范围骨缺损修复上的成功率。本项目从促进体内细胞募集、充分利用宿主自身重塑能力出发，构建了具有开放结构及稳定颌骨形态的软骨发育模板。以细胞砖技术构建的脱细胞幼稚软骨基质提供了内皮细胞的快速募集通道，其梯度降解为组织基质沉积创造了空间；贴附于其表面生长且诱导分化的肥大软骨细胞聚集体提供骨性重塑的生化因素；采用快速降解弹性内支撑体赋予形态和力学稳定性，最终再生出具有高度细胞化及基质的血管化骨组织。基于以上思路，本研究团队首次开发了一种可注射的“软骨模板”移植物，该移植物由颗粒脱细胞软骨基质、软骨源性骨髓间充质干细胞砖和富含血小板的血浆凝胶组成，研究证实其可实现血管化的骨再生。接着，通过优化脱细胞技术，研究表明1% SDS脱细胞后的软骨细胞片保持了软骨细胞的完整性和生物活性，有利于细胞的募集，促进了脱细胞软骨基质修复关节缺损，并实现了软骨下骨的血管化，为关节软骨的非细胞移植重建提供了一条新的途径。进一步地，我们构建了具有4D结构的PGS弹性体支架材料，在不额外添加骨替代物的情况下，实现了穹顶型颅骨缺损以及拱形种植体周牙槽骨缺损的完全再生，满足颅面部骨质缺损形态多变的技术要求。在此基础上，采用弹性体负载脱细胞软骨基质并融入干细胞囊泡，发现可显著促进组织血管化、提高缺损修复效率。以上研究成果在Advanced Science（IF=16.806）、Biomaterials（IF=12.479）、Acta Biomaterialia（IF=8.947）、Scientific Reports（IF=4.379）著名期刊发表SCI论文共5篇，申请国家发明专利2项。综上，本项目优化了软骨发育模板结构，提高了血管化以及成骨效率，获得了软骨内成骨的新策略。深入研究了细胞募集的时空规律以及组织来源，明确了细胞分化与移植体结构以及软骨基质之间的关系。本研究成果有助于解决传统骨移植体体内融合性差、血管化效率低以及骨再生缓慢等瓶颈问题，为节段性血管化颌骨移植提供了新的技术理念。