MOLECULAR MECHANISMS OF MATRIX GLA PROTEIN

血管和心脏瓣膜的钙化导致许多临床问题，包括充血性心力衰竭、心肌病、心绞痛以及介入和外科手术中的并发症。目前，还没有能够预防或逆转钙化的医学疗法。对潜在机制的了解将为此类疗法的开发确定新的目标。缺乏基质GLA蛋白(MGP)的小鼠出现广泛的血管钙化，血管壁被典型的软骨细胞取代。这表明MGP在维管细胞分化中起一定作用。我们假设MGP的功能是作为骨形态发生蛋白2(BMP-2)的抑制因子，骨形态发生蛋白2是钙化组织的有效诱导剂。在缺乏MGP的情况下，血管细胞可能被BMP-2诱导分化为软骨和骨细胞，而不是血管平滑肌细胞。我们假设MGP的这种作用发生在血管形成的早期。该提案有四个目标。首先是在组织培养中研究MGP水平升高对BMP-2诱导细胞分化的影响，然后利用该系统通过改变MGP蛋白来鉴定MGP中的关键序列。第二个目的是通过交联和结合研究来表征MGP和BMP-2之间的可能结合。第三个目的是利用平滑肌和软骨细胞的特异性标记物，确定在MGP缺陷小鼠的发育过程中，血管细胞何时失去正常特征并分化为软骨细胞。最后，我们将建立正常MGP缺失但表达MGP关键序列的转基因小鼠，以影响细胞分化，并研究这些序列对体内血管钙化的影响。了解MGP的分子机制将为血管疾病的发展提供广泛适用的信息。

Calcification of vessels and cardiac valves causes a multitude of clinical problems including congestive heart failure, cardiomyopathy, angina, and complications during interventional and surgical procedures. Currently, there are no medical therapies able to prevent or reverse calcification. An understanding of the underlying mechanisms would identify new targets for developments of such therapies. Mice deficient in Matrix GLA Protein (MGP) develop extensive vascular calcification with replacement of the vascular wall by typical cartilage cells. This suggests that MGP plays a role in vascular cell differentiation. We hypothesize that the function of MGP is to act as an inhibitor of bone morphogenetic protein 2 (BMP-2), a potent inducer of calcified tissues. In absence of MGP, vascular cells may be induced by BMP-2, and differentiate into cartilage and bone cells instead of vascular smooth muscle cells. We hypothesize that this effect of MGP occurs early in vessel formation. The proposal has four aims. The first is to study the effect of increased levels of MGP on cell differentiation induced by BMP-2 in tissue culture, and then use this system to identify key sequences in MGP by altering the MGP protein. The second aim is to characterize the putative binding between MGP and BMP-2 by using cross-linking and binding studies. The third aim is to identify when in the development of MGP deficient mice, vascular cells lose their normal characteristics and differentiate into cartilage cells, using specific markers for smooth muscle and cartilage cells. Finally, we will generate transgenic mice deficient in normal MGP but expressing selected key sequences of MGP identified in previous aims to affect cell differentiation, and to study the effect of these sequences on in vascular calcification in vivo. Understanding the molecular mechanisms of MGP will provide information that is widely applicable to the development of vascular disease.