STUDY OF MICE IN WHICH THE TGF-BETA1 GENE HAS BEEN DISRUPTED

在转化生长因子-β的三种亚型中，转化生长因子-β1在损伤、修复和疾病发病机制中含量最丰富，也是最受调控的。尽管没有任何明显的发育缺陷，但通过靶向干扰而敲除了转化生长因子-β1基因的小鼠，在大约3周大的时候死于多灶性炎症性疾病和自身免疫症状。我们已经使用创伤愈合来确定特定的细胞功能和细胞间的相互作用，这些功能和细胞间的相互作用会因失去转化生长因子-β1而改变。与基于外源性转化生长因子-β1的脆弱效应的预测相反，缺乏内源性蛋白可以促进皮肤伤口的愈合，提高再上皮化的速度，减少肉芽组织的数量，并改善结缔组织的重建。我们还与楚霞邓(NIDDK)合作，研究转化生长因子-β信号通路中细胞质中间体Smads 2和3缺失或杂合的小鼠伤口愈合。这些研究允许确定参与伤口愈合的特定途径，并表明Smad3而不是Smad2介导了转化生长因子-β对再上皮化的抑制作用。其他在转化生长因子-β1缺失的小鼠身上的研究表明，电子传递链的几个线粒体编码成分的mRNAs表达受到抑制，这与观察到转化生长因子-β1缺失的小鼠肝脏、心脏和肺细胞的高尔基体和线粒体的超微结构异常相一致，提示能量不足和水泡运输受损。鉴于本实验室以前对细胞内转化生长因子-β1定位到线粒体的发现，这一点特别有趣。功能研究表明，尽管缺失小鼠的单个电子链成分的最大容量没有改变，但心脏组织的氧化能力显著下降。此外，对来自这些小鼠的肝细胞系的研究表明，与野生型细胞相比，零细胞减少了氧气消耗。无论是空白细胞还是野生型细胞，在体外用转化生长因子-β处理都能迅速上调线粒体基因的表达，并部分恢复氧化代谢的缺陷。目前的研究旨在确定转化生长因子-β1调节细胞能量和线粒体基因表达的机制。-细胞能量学、生长因子、炎症、线粒体、转化生长因子-β、

Of the three isoforms of TGF-beta, TGF-beta1 is both the most abundant and the most acutely regulated in injury, repair, and disease pathogenesis. Although they lack any obvious developmental defects, mice in which the TGF-beta1 gene has been knocked out by targeted disruption die at about 3 weeks of age of multifocal inflammatory disease and autoimmune symptomatology. We have used wound healing to identify specific cellular functions and cell-cell interactions which are altered by the loss of TGF-beta1. In contrast to predictions based on the vulnerary effects of exogenous TGF-beta1, lack of the endogenous protein improves healing of cutaneous wounds, enhancing the rate of re- epithelialization, reducing the amount of granulation tissue, and improving connective tissue remodeling. We are also collaborating with Chuxia Deng (NIDDK) to study wound healing in mice null or heterozygous for Smads 2 and 3, cytoplasmic intermediates in TGF-beta signaling pathways. These studies are permitting identification of specific pathways involved in wound healing and show that Smad3 and not Smad2 mediates suppressive effects of TGF-beta on re-epithelialization.Other studies in TGF-beta1 null mice have shown suppressed expression of the mRNAs for several mitochondrially encoded components of the electron- transport chain, consistent with observations of ultrastructural abnormalities in Golgi and mitochondria of cells of liver, heart, and lung of TGF-beta1 null mice suggestive of an energy deficit and impaired vesicular transport. This is particularly intriguing in light of previous findings from this laboratory of localization of intracellular TGF-beta1 to mitochondria. Functional studies have shown that whereas maximal capacity of individual electron chain components is not altered in the null mice, there is a significant decrease in the oxidative capacity of heart tissue. Moreover, studies with hepatocyte cell lines derived from these mice show that null cells have reduced oxygen consumption compared to wildtype cells. Treatment of either null or wildtype cells with TGF-beta in vitro results in rapid upregulation of expression of mitochondrial genes and restores, in part, the deficit in oxidative metabolism. Present investigations are aimed at determining the mechanism whereby TGF-beta1 regulates cellular energetics and expression of mitochondrial genes. - cell energetics, growth factors, Inflammation, mitochondria, TGF-beta,