Fiber development and matrix production in tissue-engineered menisci using bovine mesenchymal stem cells and fibrochondrocytes

Mesenchymal stem cells (MSCs) have been investigated with promising results for meniscus healing and tissue engineering. While MSCs are known to contribute to extracellular matrix (ECM) production, less is known about how MSCs produce and align large organized fibers for application to tissue engineering the meniscus. The goal of this study was to investigate the capability of MSCs to produce and organize ECM molecules compared to meniscal fibrochondrocytes (FCCs). Bovine FCCs and MSCs were encapsulated in an anatomically accurate collagen meniscus using monoculture and co-culture of each cell type. Each meniscus was mechanically anchored at the horns to mimic the physiological fixation by the meniscal entheses. Mechanical fixation generates a static mechanical boundary condition previously shown to induce formation of oriented fiber by FCCs. Samples were cultured for 4 weeks and then evaluated for biochemical composition and fiber development. MSCs increased the glycosaminoglycan (GAG) and collagen production in both co-culture and monoculture groups compared to FCC monoculture. Collagen organization was greatest in the FCC monoculture group. While MSCs had increased matrix production, they lacked the fiber organization capabilities of FCCs. This study suggests that GAG production and fiber formation are linked. Co-culture can be used as a means of balancing the synthetic properties of MSCs and the matrix remodeling capabilities of FCCs for tissue engineering applications.

间充质干细胞（Mesenchymal stem cells, MSCs）在半月板愈合与组织工程领域的相关研究已取得可喜成果。尽管已知间充质干细胞可促进细胞外基质（extracellular matrix, ECM）的合成，但针对其如何生成并排列大型有序纤维以应用于半月板组织工程的机制，目前仍知之甚少。本研究旨在对比间充质干细胞与半月板纤维软骨细胞（meniscal fibrochondrocytes, FCCs）生成并组装细胞外基质分子的能力。研究人员将牛源半月板纤维软骨细胞与间充质干细胞分别以单培养及共培养的方式，包埋于解剖结构匹配的胶原半月板支架中；并在半月板的两角处实施机械固定，以模拟半月板骨附着处的生理固定状态。此前已有研究证实，机械固定可产生静态力学边界条件，能够诱导半月板纤维软骨细胞形成定向纤维。样本培养4周后，对其生化组成与纤维发育情况进行评估。结果显示，与半月板纤维软骨细胞单培养组相比，共培养组与间充质干细胞单培养组的糖胺聚糖（glycosaminoglycan, GAG）与胶原蛋白合成量均有所提升；而胶原蛋白的组织有序度在半月板纤维软骨细胞单培养组中最为显著。尽管间充质干细胞的基质合成能力更强，但其并不具备半月板纤维软骨细胞的纤维组织能力。本研究提示糖胺聚糖合成与纤维形成之间存在关联；共培养策略可用于平衡间充质干细胞的合成特性与半月板纤维软骨细胞的基质重塑能力，从而适配组织工程的应用需求。