National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, PR China.
National Engineering Research Center for Biomaterials, Sichuan University, Chengdu 610064, PR China.
Acta Biomater. 2021 Nov;135:304-317. doi: 10.1016/j.actbio.2021.08.029. Epub 2021 Aug 26.
In order to repair an osteochondral defect, it is critical to advance a bi-lineage constructive scaffold with gradient transition. In this study, we developed a simple and straightforward approach for fabricating a multi-domain gel scaffold through the assembly/disassembly of low-molecular-weight gels (LMWGs) inside a stable PEGDA network by photopolymerization. The versatility of this technology enabled to vary biological, topological, and mechanical properties through material selection and to generate a chondrogenic-osteogenic gradient transition. The multi-domain gel exhibited an increasing stiffness gradient along the longitudinal direction from the cartilage layer at approximately 20 kPa to the bone layer at approximately 300 kPa as well as spatial variation at the gradient interface. Moreover, the transitional layer with a condensed structure and intermediate stiffness prevented delamination of the contrasting layers and maintained microenvironmental differences in the upper and lower layers. The in vitro results indicated that each domain had an individual capacity to spatially control the differentiation of MSCs toward osteoblastic lineage and chondrocytic lineage. This was mainly because the mechanical and topographical cues from the respective domains played an important role in modulating the Rho-ROCK signaling pathway, whereas the blockage of ROCK signals significantly impaired domain-modulated osteogenesis and enhanced chondrogenesis. Additionally, the quantity and quality of osteochondral repair were evaluated at 4 and 8 weeks through histological analysis and micro-computed tomography (micro-CT). The results indicated that the multi-domain gels distinctly improved the regeneration of subchondral bone and cartilage tissues. Overall, the outcomes of this study can motivate future bioinspired gradient and heterogeneity strategies for osteochondral tissue regeneration. STATEMENT OF SIGNIFICANCE: The regeneration of osteochondral defects remains a major challenge due to the complexity of osteochondral structure and the limited self-repair capacity of cartilage. The gradient design to mimic the transition between the calcified cartilage and the subchondral bone plate as well as the zones of cartilage is an effective strategy. In this study, controlled multi-domain gels were fabricated through the assembly/disassembly of low-molecular-weight gels inside a stable PEGDA network by photopolymerization. The prepared multi-domain gels showed a chondrogenic-osteogenic gradient transition, which decreased the possibility of delamination and stimulated osteochondral tissue regeneration in vivo. Overall, our study promotes new strategies of bioinspired gradients and heterogeneities for more challenging applications.
为了修复骨软骨缺损，构建具有梯度转变的双谱系构建性支架至关重要。在本研究中，我们通过光聚合在稳定的 PEGDA 网络内组装/拆卸低分子量凝胶 (LMWG) ，开发了一种简单直接的方法来制造多域凝胶支架。该技术的多功能性使通过材料选择来改变生物、拓扑和机械性能，并产生软骨-成骨梯度转变成为可能。多域凝胶在从软骨层的大约 20 kPa 到骨层的大约 300 kPa 的纵向方向上表现出逐渐增加的刚度梯度，并且在梯度界面处具有空间变化。此外，具有凝聚结构和中间刚度的过渡层防止了对比层的分层，并保持了上下层之间的微环境差异。体外结果表明，每个域都具有单独的能力来空间控制 MSCs 向成骨谱系和软骨细胞谱系的分化。这主要是因为各自域的机械和拓扑线索在调节 Rho-ROCK 信号通路方面起着重要作用，而 ROCK 信号的阻断则显著损害了域调制的成骨作用，并增强了软骨形成。此外，通过组织学分析和微计算机断层扫描 (micro-CT) 在 4 周和 8 周时评估了骨软骨修复的数量和质量。结果表明，多域凝胶明显改善了软骨下骨和软骨组织的再生。总体而言，这项研究的结果可以激励未来用于骨软骨组织再生的仿生梯度和异质性策略。
由于骨软骨结构的复杂性和软骨的有限自我修复能力，骨软骨缺损的再生仍然是一个主要挑战。模拟钙化软骨和软骨下骨板以及软骨区域之间转变的梯度设计是一种有效的策略。在这项研究中，通过光聚合在稳定的 PEGDA 网络内组装/拆卸低分子量凝胶，制备了受控的多域凝胶。所制备的多域凝胶表现出软骨-成骨梯度转变，降低了分层的可能性，并刺激了体内骨软骨组织的再生。总体而言，我们的研究促进了更具挑战性应用的仿生梯度和异质性的新策略。
