RI COBRE: ENDOCRINE AND NUTRITIONAL CONTROL OF LONG BONE GROWTH

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 在发展中国家，营养不良仍然是一个世界性问题。在发达国家，许多疾病，从神经性厌食症到克罗恩病，都会导致儿童严重的发育障碍。本研究的目的是确定营养物质的有效性，特别是作为最丰富的必需氨基酸的亮氨酸，影响软骨细胞的增殖、分化、细胞外基质(ECM)的沉积及其相互作用的机制。人们很早就知道营养状况通过调节GH/IGF-I轴来影响线性生长。最近，营养物质通过哺乳动物雷帕霉素靶点(MTOR)直接调节细胞的信号机制已被阐明。我们推测，亮氨酸通过影响软骨细胞的增殖、分化和ECM沉积，直接调控软骨的形成，这是骨生长的三个关键组成部分。我们的假设是基于我们的观察。首先，mTOR直接调节软骨形成。MTOR抑制导致软骨形成的关键调节因子印度刺猬(IHH)的表达减少。IHH减少可能是mTOR作用的中心。MTOR对IHH的调节是一个新的观察结果。第二，亮氨酸限制和mTOR抑制可能通过miRNA调节导致ECM mRNA表达显著降低。最后，我们利用一个体外的跖骨移植系统来证明我们在软骨源性ATDC5细胞系中所观察到的生理学相关性。根据我们的初步发现，我们提出了以下具体目标。具体目标1：确定mTOR抑制和亮氨酸限制对IHH调节的分子机制，从而影响软骨细胞的生长和分化。。特定目的2：确定mTOR抑制和亮氨酸限制对miRNA-29调控导致ECM表达改变的影响及其在软骨细胞生长和分化中的功能作用。特定目的3：利用胎儿跖骨移植模型，我们将研究mTOR抑制和亮氨酸限制对骨生长、生长板动力学和软骨形成标志物，特别是IHH和miRNA-29的影响。我们将研究mTOR抑制和亮氨酸限制对恢复骨中IHH和miRNA-29表达的影响。了解营养物质对骨生长的直接影响可能有助于更好地了解骨骼的长期健康状况，以及在营养限制或相关医疗条件下对生长受损的处理。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Malnutrition remains a worldwide problem in developing countries. In developed countries, many medical conditions, ranging from anorexia nervosa to Crohn's disease, result in severe growth impairment in children. The objective of this study is to identify mechanisms by which nutrient availability, specifically leucine which is the most abundant essential amino acids, affects chondrocyte proliferation, differentiation, deposition of extracellular matrix (ECM) and their interactions. It has long been known that nutritional status effect linear growth by modulating GH/IGF-I axis. Recently signaling mechanism by which nutrients directly regulate cells via mammalian Target Of Rapamycin (mTOR) has been elucidated. We hypothesize that leucine directly regulates chondrogenesis directly by affecting chondrocyte proliferation, differentiation and ECM deposition, 3 key components of bone growth. Our hypothesis is based on our observations. First, mTOR directly regulates chondrogenesis. MTOR inhibition results in decreased expression of Indian hedgehog (Ihh), a key regulator of chondrogenesis. Decreased Ihh could be central to mTOR action. Regulation of Ihh by mTOR is a new observation. Second, leucine restriction and mTOR inhibition result in significant reduction of ECM mRNA expression likely via miRNA regulation. Lastly, we utilized an ex vivo metatarsal explant system to demonstrate the physiological relevance of observations we made in the chondrogenic ATDC5 cell line. Based on our preliminary findings, we propose the following specific aims. Specific Aim 1: Identify the molecular mechanisms that mediate the effect of mTOR inhibition and leucine restriction on Ihh regulation and, as a consequence, chondrocyte growth and differentiation. . Specific Aim 2: Determine the effect of mTOR inhibition and leucine restriction on miRNA-29 regulation resulting in altered ECM expression and functional role in chondrocyte growth and differentiation Specific Aim 3: Utilizing a fetal metatarsal explant model, we will study the effect of mTOR inhibition and leucine restriction on bone growth, growth plate dynamics and chondrogenic markers, in particular Ihh and miRNA-29. We will study the effect of restoring Ihh and miRNA-29 expression in bones subjected to mTOR inhibition and leucine restriction. Understanding the direct effect of nutrients on bone growth may lead to a better understanding of long term bone health as well as management of the impaired growth in nutrient restriction or related medical conditions.