Gill Sean E, Pape M Cynthia, Leco Kevin J
Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry and Child Health Research Institute, University of Western Ontario, London, Ontario, Canada, N6A 5C1.
Dev Biol. 2006 Oct 15;298(2):540-54. doi: 10.1016/j.ydbio.2006.07.004. Epub 2006 Jul 12.
Tissue inhibitors of metalloproteinases (TIMPs) regulate extracellular matrix (ECM) degradation by matrix metalloproteinases (MMPs) throughout embryogenesis. We examined lungs from TIMP3 null mice and found decreased bronchiole branching, enhanced activity of MMPs and enhanced fibronectin degradation throughout lung development compared to controls. Activation of focal adhesion kinase (FAK) was also reduced from embryonic days 12.5 through 14.5 in TIMP3 null lungs. Treatment with a synthetic MMP inhibitor, GM6001, in utero enhanced the branching pattern in both wild type and null lungs accompanied by a restoration of fibronectin localization, signaling through FAK and epithelial cell proliferation in null lungs. Direct down-regulation of FAK abundance in WT lung organ culture by siRNA targeting resulted in reduced bronchiole branching, phenocopying the TIMP3 defect. We propose that enhanced MMP activity in the absence of TIMP3 interferes with focal ECM proteolysis, perturbing the intracellular signaling necessary for correct pattern formation of the bronchiole tree during bronchiole branching morphogenesis. Thus, TIMP3 can indirectly regulate epithelial cell proliferation via MMP inhibitory activity. While others have demonstrated this function for MMPs, and there is in vitro evidence that TIMP3 controls proliferation, to our knowledge this is the first evidence of TIMP3 regulating proliferation in vivo.
金属蛋白酶组织抑制剂（TIMPs）在整个胚胎发育过程中通过基质金属蛋白酶（MMPs）调节细胞外基质（ECM）的降解。我们检查了TIMP3基因敲除小鼠的肺，发现与对照组相比，在整个肺发育过程中细支气管分支减少、MMPs活性增强以及纤连蛋白降解增强。在TIMP3基因敲除的肺中，从胚胎第12.5天到14.5天，粘着斑激酶（FAK）的激活也减少。在子宫内用合成的MMP抑制剂GM6001处理，增强了野生型和基因敲除型肺的分支模式，同时恢复了纤连蛋白的定位，恢复了基因敲除型肺中通过FAK的信号传导和上皮细胞增殖。通过靶向siRNA直接下调野生型肺器官培养物中FAK的丰度，导致细支气管分支减少，模拟了TIMP3缺陷。我们提出，在没有TIMP3的情况下，MMP活性增强会干扰局部ECM蛋白水解，扰乱细支气管分支形态发生过程中细支气管树正确模式形成所需的细胞内信号传导。因此，TIMP3可以通过MMP抑制活性间接调节上皮细胞增殖。虽然其他人已经证明了MMPs的这种功能，并且有体外证据表明TIMP3控制增殖，但据我们所知，这是TIMP3在体内调节增殖的第一个证据。
