Synovial Stem Cell Biology

关节软骨不表现出内源性修复，部分原因是组织中缺乏干细胞/祖细胞，而邻近的滑膜富含能够在体外和体内分化成软骨的间充质干细胞（MSC）。我们已经证明，关节内的MSC对微环境的变化非常敏感，并且滑液的变化可以调节细胞的软骨形成潜力。此外，我们还发现，来自受伤/关节炎/发炎关节的MSC在特定培养条件下不能完全分化为软骨细胞，而来自正常关节的MSC具有完全功能。我们已经深入研究了这种效应，发现有证据表明CCL 2/MCP-1是从滑膜巨噬细胞分泌的，现在有初步证据表明这些巨噬细胞可能充当滑膜干细胞龛。假设干细胞小生境提供能够指导干细胞活性的微环境。该生态位被认为在干细胞活性随衰老而下降方面特别重要，其中随着常驻干细胞群体被证明在维护和修复方面越来越不足，组织稳态的丧失正在进行。然而，体外实验表明，当这些干细胞从龛中分离出来时，仍然具有功能，这强烈表明干细胞龛可能在衰老和疾病过程中失效。我的项目的目的是阐明人和小鼠膝关节滑膜中巨噬细胞和滑膜间充质干细胞之间存在的调节反馈机制，并了解这些途径如何在体外调节干细胞的命运，离体和体内。这将通过承担以下目标来实现：目标1（体外）：确定巨噬细胞产生的信号分子调节滑膜MSC，并测定这种能力是否通过修饰巨噬细胞活化状态而增强。目的2（离体）：目的3（体内）：当巨噬细胞数量或激活状态在滑膜干细胞龛内实验性改变时，量化滑膜MSC介导的组织修复的变化。这项研究计划将导致细胞生物学和生物工程领域的重大进展，有助于i）理解巨噬细胞在滑膜干细胞生态位中的作用，包括这些细胞如何调节干细胞潜能;和ii）用于潜在开发新的和改进的组织工程/再生医学方法的框架，以恢复和/或改善组织工程/再生医学方法。或在老化或受伤后维持正常的关节功能。

Articular cartilage does not exhibit endogenous repair, in part because of a lack of stem/progenitor cells in the tissue, whereas the adjacent synovial membrane is abundant with mesenchymal stem cells (MSCs) capable of differentiating into cartilage both in vitro and in vivo. We have demonstrated that the MSCs within the joint are very sensitive to changes in the micro-environment and that changes in the synovial fluid can regulate the chondrogenic potential of the cells. In addition, we have also found that MSCs from injured/arthritic/inflamed joints are incapable of fully differentiating into chondrocytes under specific culturing conditions whereas MSCs from normal joints are fully functional. We have explored this effect in great depth and found evidence that suggests CCL2/MCP-1 is being secreted from synovial macrophages and now have preliminary evidence that these macrophage cells may be acting as a synovial stem cell niche. The stem cell niche is hypothesized to provide a micro-environment that is capable of directing stem cell activity. The niche is thought to be particularly important in regards to the decline of stem cell activity with aging, in which a loss of tissue homeostasis progresses as the resident stem cell populations prove to be increasingly inadequate in terms of maintenance and repair. However, in vitro evidence demonstrates that these stem cells when separated from the niche are still functional, strongly suggesting that the stem cell niche maybe failing during aging and disease processes.The objective of my program is to elucidate the regulatory feedback mechanisms that exist between macrophages and synovial MSCs within human and mouse knee joint synovium and understand how these pathways regulate stem cell fate in vitro, ex vivo and in vivo. This will be achieved by undertaking the following aims:Aim 1 (In vitro): Determine which signaling molecules produced by macrophages regulate synovial MSCs, and assay if this ability is augmented through modification of the macrophage activation state. Aim 2 (Ex vivo): Assay for changes in synovial MSC function when macrophages are removed from the synovium using a targeted liposomal based approach.Aim 3 (In vivo): Quantify changes in synovial MSC mediated tissue repair when macrophage number or activation state is experimentally modified within the synovial stem cell niche. This program of research will result in significant advances in the field of cell biology and bioengineering by contributing to i) the understanding of the role of macrophages in the synovial stem cell niche including how these cell regulate stem cell potential; and ii) a framework for the potential development of new and improved tissue engineering / regenerative medicine approaches to restoring and/or maintaining normal joint function with aging or after injury.