Mesenchymal Stem Cells and the Microenvironment

描述（由申请人提供）：人间充质干细胞（MSCs）是一种多能干细胞，可分化为人体肌肉骨骼和基质组织中的许多细胞，包括成纤维细胞、软骨细胞、成骨细胞、肌细胞和脂肪细胞。虽然MSCs分化成适当的谱系可以促进损伤组织的愈合，但不适当的谱系规范可能导致许多病理生理过程，包括骨质疏松的骨骼减少和脂肪增加，以及动脉粥样硬化血管壁的钙化。因此，通过局部微环境线索调节MSCs的谱系承诺可能对我们对许多退行性和愈合过程的基本理解至关重要。本研究的长期目标是表征局部周围微环境中驱动人间充质干细胞（MSCs）谱系规范和分化的线索，以及所涉及的分子途径。研究者发现，通过RhoA信号传导和细胞骨架张力的机制，MSCs与纤维连接蛋白的粘附调节了MSCs在成脂和成骨谱系规范之间的承诺开关。在过去的资助期间，他已经证明了这些粘附和机械线索特异性地调节SMAD和PPARgamma，这两个关键的转录因子对骨生成和脂肪生成至关重要。具体目的1将是研究整合素激活如何调节BMP-SMAD信号和成骨。具体目标2将研究RhoA如何调节SMAD活性。具体目标3将研究粘附和机械线索如何调节PPARgamma信号。总之，这些研究将确定细胞粘附，RhoA和细胞骨架张力在MSC谱系承诺中的作用，并通过微环境线索建立MSC分化调节的分子基础。

DESCRIPTION (provided by applicant): Human mesenchymal stem cells (MSCs) are multipotent stem cells that differentiate into many of the cells resident in musculoskeletal and stromal tissues of the human body, including fibroblasts, chondrocytes, osteoblasts, myocytes, and adipocytes. While differentiation of the MSCs into appropriate lineages may enhance healing of injured tissues, inappropriate lineage specification may be responsible for numerous pathophysiologic processes, including the decreased bone and increased fat in osteoporotic bones, and the calcification of atherosclerotic vessel walls. Regulation of the lineage commitment of MSCs by local microenvironmental cues therefore may be critical to our fundamental understanding of numerous degenerative as well as healing processes. The long term objective of this research is to characterize the cues within the local surrounding microenvironment that drive the lineage specification and differentiation of human mesenchymal stem cells (MSCs), and the molecular pathways involved. The investigator has discovered that adhesion of MSCs to fibronectin regulates a commitment switch in the MSCs between adipogenic and osteogenic lineage specification, through a mechanism involving RhoA signaling and cytoskeletal tension. During the past grant period, he has demonstrated that these adhesive and mechanical cues specifically regulate SMAD and PPARgamma, two key transcription factors critical to osteogenesis and adipogenesis. Specific Aim 1 will be to investigate the how integrin activation regulates BMP-SMAD signaling and osteogenesis. Specific Aim 2 will be to investigate how RhoA regulates SMAD activity. Specific Aim 3 will be to investigate how adhesive and mechanical cues regulate PPARgamma signaling. Together, these studies will define roles of cell adhesion, RhoA, and cytoskeletal tension in MSC lineage commitment, and establish a molecular basis for the regulation of MSC differentiation by microenvironmental cues. PUBLIC HEALTH RELEVANCE: Human mesenchymal stem cells contribute to the maintenance and healing of many musculoskeletal tissues, but they also can produce inappropriate cell lineages to exacerbate disease, such as occurs with calcification of atherosclerotic vessels. They are now being isolated as a promising source of stem cells for regenerative therapies, but again their utility rests upon predictable control of their differentiation potential. This project is designed to develop a better understanding of how adhesive and mechanical cues direct these stem cells to differentiate into specific lineages, such that we may better design future approaches to treat or prevent degenerative diseases.