Mechanical Control of Mesenchymal Stem Cell Lineage Allocation

间充质干细胞谱系分配的机械控制

• 批准号: 8067137
• 负责人: Janet E Rubin
• 金额: $ 28.77万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8067137
• 关键词: Adipocytes; Affect; Aging; Applications Grants; Bed rest; Binding; Bone Marrow; CCAAT-Enhancer-Binding Proteins; Cell Lineage; Cells; Consensus; Data; Disinhibition; Environment; Estrogens; Event; Evolution; Exercise; Fatty acid glycerol esters; Food; Functional disorder; Goals; Grant; Health; Individual; Intracellular Accumulation of Lipids; Investigation; Laboratories; Link; Lipids; Locomotion; Marrow; Mechanical Stimulation; Mechanics; Mesenchymal Stem Cells; Morphology; Mus; Muscle Cells; Nature; Nuclear; Osteoblasts; Osteogenesis; Output; Pathologic; Pathway interactions; Peroxisome Proliferator-Activated Receptors; Phenotype; Phosphorylation; Production; Proteins; Proto-Oncogene Proteins c-akt; Regimen; Regulation; Reporter; Repression; Resistance; Signal Transduction; Skeleton; Source; Stimulus; TSC2 gene; Testing; Time; Transactivation; Work; adipokines; adiponectin; aged; aging population; bone; bone mass; human FRAP1 protein; insight; integrin-linked kinase; lipid biosynthesis; osteogenic; osteoprogenitor cell; prevent; progenitor; public health relevance; receptor; response; sedentary; senescence; skeletal; stem cell differentiation; transcription factor

DESCRIPTION (provided by applicant): Mesenchymal stem cells (MSCs) in bone marrow provide progenitors for both adipocyte and osteoblast cells and the output of the MSC pool reflects a reciprocal relationship between these two lineages. The ability of mechanical signals to promote osteogenic lineage has raised the exciting possibility that exercise might be able to regulate MSC lineage. Our work indicates that mechanical input can inhibit adipogenesis, exerting a significant control over MSC reciprocity through control of ¿-catenin signaling. Signals which promote MSC adipogenesis involve diminution in ¿-catenin signaling, followed by a rise in PPAR?, adiponectin and lipid content. We have compelling data showing that mechanical strain induces persistent ¿-catenin activation in MSC through alteration of GSK3¿ phosphorylation via AKT in MSCs. Repetitive loading bouts increase the ¿-catenin signal duration such that downstream events such as the rise in adiponectin and lipid droplets are inhibited. Our results suggest that even a strongly adipogenic microenvironment can be counteracted in this way by repetitive bouts of mechanical input. This allows us to hypothesize that "mechanical stimulation represses adipogenic conversion through ¿-catenin inhibition of PPAR? action". With this grant proposal we propose to test this hypothesis, fully characterizing the mechanisms by which mechanical input prevents adipogenesis and controls MSC lineage selection. We will investigate the temporal nature of the signal: how much and how many repetitions are required to regulate adipogenesis, and we will ask if mechanical input induces an alternate lineage selection, e.g., osteoprogenitor or myocyte with the help of unique reporter mice from which we make MSC clones for study. Interactions between local cells will be probed asking whether soluble factors secreted from strained cells can act on unstrained cells (SA1). We will ascertain the mechanisms by which mechanical strain activates ¿-catenin (via AKT and GSK32), as well consider other mechanical targets (Wnts and BMPs) that could exert local control. We will consider alternative targets of GSK3¿ such as NFATc1 and mTOR (SA2). We will define how mechanical activation perturbs PPAR? promotion of adipogenesis directly and indirectly in SA3. Our proposal has significance for understanding the fate of MSC in a sedentary and aging population. It will be critically important to characterize the cascade of signals involved in mechanical regulation of MSC lineage selection, as this should identify modifiable steps in pathways that suppress adipogenesis and stimulate osteogenesis. PUBLIC HEALTH RELEVANCE: Evolution has led to interrelationships between bone and fat together to allow individuals to move to food sources (skeleton necessary for locomotion), and store energy (as fat). Clearly our nation's health is impacted by counterproductive "activities" -lack of exercise and caloric excess. Indeed, as the presence of mechanical information prevents emergence of adipocytes from the marrow, exercise may be considered a way to prevent bone marrow senescence as "old" bone marrow mimics unloading with increased fat. As such, understanding the mechanisms by which mechanical input controls lineage selection is highly relevant to an aging population, and should have high importance for understanding the pathophysiology behind the decreased osteoprogenitor pool and how to reverse it. Consensus building now needs to be a targeted goal, examining the basics of how exercise impacts these relationships by defining the fate of mesenchymal stem cells. We propose here a focused investigation of how loading cells can affect lineage selection when that lineage is already directed toward fat (as would be seen in non-exercising individuals, or aged individuals). We seek insights into the type of mechanical input (how much and for how long), and the targets, beginning with ¿-catenin, but considering other factors which determine lineage selection, and what strained cells become. We will examine proximal nodes in strain activation of ¿-catenin and investigate alternative effectors of mechanical strain. We will look at direct effects to prevent adipogenesis (inhibition of PPAR? expression) and indirect ¿- catenin inhibition of PPAR? responses.

描述(申请人提供)：骨髓中的间充质干细胞(MSCs)为脂肪细胞和成骨细胞提供祖细胞，MSC池的输出反映了这两种血统之间的相互关系。机械信号促进成骨细胞谱系的能力增加了运动可能调节MSC谱系的令人兴奋的可能性。我们的工作表明，机械输入可以抑制脂肪生成，通过控制连环蛋白信号对MSC的相互作用发挥显著控制作用。促进MSC脂肪生成的信号包括-连环蛋白信号的减少，随后是PPAR？、脂联素和脂质含量的上升。我们有令人信服的数据表明，机械应变通过改变MSCs中AKT的GSK3磷酸化来诱导MSC中持续的连环蛋白激活。重复的负荷增加了连环蛋白信号的持续时间，从而抑制了下游事件，如脂联素和脂滴的上升。我们的结果表明，即使是一个强烈的成脂微环境，也可以通过重复的机械输入来抵消。这使得我们可以假设“机械刺激通过连环蛋白抑制PPAR？作用来抑制成脂转化”。通过这项拨款提案，我们建议检验这一假设，充分描述机械输入阻止脂肪生成和控制MSC谱系选择的机制。我们将研究信号的时间性质：需要多少和多少重复来调控脂肪生成，我们将询问机械输入是否诱导了另一种谱系选择，例如，借助独特的报告小鼠，我们制作了MSC克隆用于研究的成骨细胞或肌细胞。将探讨局部细胞之间的相互作用，询问从应变细胞分泌的可溶性因子是否能作用于非应变细胞(SA1)。我们将确定机械应变激活连环蛋白的机制(通过AKT和GSK32)，以及考虑其他可以施加局部控制的机械靶标(WNTS和BMPs)。我们将考虑GSK3的替代目标，如NFATc1和mTOR(SA2)。我们将定义机械激活如何扰乱PPAR？直接和间接促进SA3细胞的成脂作用。我们的建议对于理解MSC在久坐和老龄化人口中的命运具有重要意义。至关重要的是，确定参与MSC谱系选择的机械调控的信号级联，因为这应该识别抑制脂肪生成和刺激成骨的通路中的可修改步骤。 与公共健康相关：进化导致了骨骼和脂肪之间的相互关系，使个体能够移动到食物来源(运动所需的骨骼)，并储存能量(作为脂肪)。显然，我们国家的健康受到了适得其反的“活动”的影响--缺乏锻炼和卡路里过量。事实上，由于机械信息的存在阻止了脂肪细胞从骨髓中出现，运动可能被认为是防止骨髓衰老的一种方法，因为“老”的骨髓会随着脂肪的增加而模拟卸载。因此，了解机械输入控制谱系选择的机制与老龄化人口高度相关，对于理解骨祖细胞池减少背后的病理生理学以及如何逆转它具有重要意义。建立共识现在需要成为一个有针对性的目标，研究运动如何通过定义间充质干细胞的命运来影响这些关系的基础。在这里，我们建议对加载细胞如何影响谱系选择进行重点研究，当谱系已经指向脂肪时(就像在不锻炼的人或老年人中看到的那样)。我们寻求对机械输入的类型(多少和多长时间)和目标的洞察，从连环蛋白开始，但考虑到决定谱系选择的其他因素，以及紧张的细胞变成什么。我们将研究连环蛋白应变激活的近端结节，并研究机械应变的替代效应。我们将着眼于预防脂肪生成的直接影响(抑制PPAR？表达)和间接连环蛋白抑制PPAR？回应。