Uncovering the influence of niche biomechanics on satellite stem cell fate

骨骼肌包含在发育过程中由细胞融合形成的对齐的圆柱形肌纤维。成人骨骼肌具有自我修复的特性，这是由于少量的微小细胞散布在组织中，这些细胞位于每个肌纤维的顶部，并被称为基底膜的蛋白质薄片覆盖。凭借这种解剖学定位或生态位，这些“卫星”干细胞（SC）驻留在三维环境中，其中纤维和基底膜表面的蛋白质环境是不同的。其他人正在进行的研究表明，SC生态位中生物分子的极化性质对于调节它们的行为很重要。与此同时，我们的实验室与多学科合作者一起定义和提供生态位生物力学应力作为生态位的额外极化特征，与生物分子一起调节SC行为。 骨骼肌会动。我们预计，当肌肉纤维收缩和放松时，SC的纤维相关表面会受到推力和拉力。由于肌纤维的紧密堆积和排列的性质，预计SC的基底膜相关表面会受到挤压力。我们假设，打破这种机械稳态（就像肌肉受伤时发生的那样）是通过物理接合细胞表面蛋白来调用SC采取修复行动的直接且局部的手段。 在本地和国际合作和实验室交流中，我们的学员将与生物物理学，显微镜，基于FRET的张力传感器和膜蛋白生物学的专家密切合作，以验证我们的假设。我们将量化工程二维培养微环境中的肌原细胞拉力，以定义当细胞不受第三维束缚时的力产生最大值。我们将量化SC粘附到其小生境的程度，并确定有助于这种附着的关键膜蛋白。最后，我们将证明，打破机械稳态在活的肌肉组织直接从事膜蛋白，推动SC的睡眠开始修复组织损伤。 这项研究将通过一个新的透镜来观察生态位，从而推进SC生物学的基础知识。我们的学员将获得利基压力的物理和数学，高分辨率显微镜和干细胞生物学方面的技能，同时建立一个庞大的科学网络，从而使他们在学术界，医学或工业界的职业生涯中保持平衡。

A skeletal muscle contains aligned, cylindrical muscle fibres formed by the fusion of cells during development. Adult skeletal muscles possess self-healing properties due to a small number of tiny cells sprinkled within the tissue that sit atop each muscle fibre and are covered by a thin sheet of proteins known as the basement membrane. By virtue of this anatomical positioning, or niche, these `satellite' stem cells (SCs) reside in a three-dimensional environment where the protein milieu at their fibre and basement membrane surfaces are distinct. Ongoing studies by others show that the polarized nature of biomolecules in the SC niche is important for regulating their behavior. In parallel, our lab engages multidisciplinary collaborators to define and offer niche biomechanical stress as an additional polarized feature of the niche that, together with biomolecules, regulates SC behavior. Skeletal muscles move. We expect that when the muscle fibres contract and relax, that the fibre-associated surface of an SC experiences pushing and pulling forces. By virtue of the closely packed and aligned nature of muscle fibres, the basement membrane-associated surface of an SC is expected to experience squishing forces. We hypothesize that breaking this mechanical homeostasis, as would occur when a muscle is injured, is a direct and localized means to call SCs to reparative action by physically engaging cell surface proteins. In local and international collaborations and lab exchanges, our trainees will work closely with experts in biophysics, microscopy, FRET-based tension sensors, and membrane protein biology to test our hypothesis. We will quantify myogenic cell pulling forces in engineered two-dimensional culture microenvironments to define force generation maxima when the cells are unfettered by a third dimension. We will quantify the degree to which SCs are adhered to their niche and identify key membrane proteins contributing to this attachment. Lastly, we will demonstrate that breaking mechanical homeostasis in a living muscle tissue directly engages membrane proteins that push SCs out of slumber to begin repairing tissue damage. This research will advance fundamental knowledge about SC biology by gazing at the niche through a new lens. Our trainees will gain skillsets in the physics and mathematics of niche stresses, in hi-resolution microscopy, and in stem cell biology, while building a vast scientific network, and thereby poising them for careers in academia, medicine, or industry.