Study of medianism for the cell growth inhibition by HB-EGF in cardiac valve development

HB-EGF是EGF家族的一员，对肝素和硫酸乙酰肝素（HS）具有高亲和力，已知参与心脏瓣膜发育。HB-EGF在此过程中抑制间充质细胞的增殖。本研究探讨了HB-EGF抑制细胞生长的调控机制。1）HB-EGF与HS-蛋白聚糖（HSPGs）相互作用在心脏瓣膜发育中的意义。我们产生了表达肝素结合结构域截短形式（HB^<Δbb>）的分子的敲入小鼠，其缺乏HS结合活性。HB^<Δbb/Δbb>小鼠在瓣膜形成过程中出现了增大的心脏瓣膜，伴有间充质细胞的异常过度增殖，表型与HB-EGF null（HB^<dcl/del>）小鼠相似。使用内皮细胞垫外植体培养的体外研究证明HB-EGF-HSPGs相互作用对HB-EGF-EGFR信号介导的生长抑制是必需的 ...更多信息 间充质细胞。这些结果表明，HB-EGF与HSPGs的相互作用促进了心脏瓣膜发育中分化的间充质细胞的生长抑制。2）HB-EGF和Snail信号传导在瓣膜发生期间负调节间充质细胞的增殖。我们发现，在HB^<del/del>突变瓣膜中，Snail的表达在瓣膜发生的重构过程中显著降低。将Snail和HB-EGF外源性引入HB^<del/del>突变瓣膜能够拯救间充质细胞的过度增殖。这些结果表明，HB-EGF抑制间充质细胞增殖通过蜗牛在瓣膜重塑。3）围产期远端肺发育：HB-EGF诱导细胞生长抑制的另一个生理过程。HB^<del/del>新生儿表现出异常厚的肺泡壁，发生在E18.5，其减少了末端囊状空间面积，细胞增殖增加，表明HB-EGF抑制远端肺细胞增殖。此外，对HB-EGF和TGFα双突变新生儿的肺泡形态和增殖的分析显示，HB-EGF和TGF α在这种抑制中协同作用。HB^<del/del>小鼠和wave 2小鼠（一种亚型EGFR突变株）之间的杂交表明，HB-EGF和EGFR在此过程中协同作用。因此，HB-EGF具有抑制功能，其有助于在围产期远端肺发育中通过EGFR与TGF α协同减缓远端肺细胞增殖。（Dev.动力学2008，237，247-258）减

HB-EGF is a member of the EGF family of growth factors that has a high affinity for heparin and heparan sulfate (HS), and is known to be involved in cardiac valve development. HB-EGF suppresses proliferation of mesenchymal cells in this process. In this research, we investigated the regulatory mechanisms involved in the HB-EGF-induced cell growth inhibition in cardiac valve development (valvulogenesis).1) Significance of the interaction of HB-EGF with HS-proteoglycans (HSPGs) in valvulogenesis. We generated the knock-in mice expressing a heparin-binding domain-truncated form (HB^<Δbb>) of the molecule, which lacks HS-binding activity. HB^<Δbb/Δbb> mice developed enlarged cardiac valves with abnormal hyperproliferation of the mesenchymal cells during valvulogenesis, phenotypes similar to that in HB-EGF null (HB^<dcl/del>) mice. In vitro study using endocardial cushion explants culture demonstrated requirement of HB-EGF-HSPGs interaction for HB-EGF-EGFR signal-mediated growth-inhibition … More of mesenchymal cells. These results indicate that interaction of HB-EGF with HSPGs promotes growth-inhibition of differentiated mesenchymal cells in developing cardiac valve. (Manuscript in preparation)2) HB-EGF and Snail signaling negatively regulates proliferation of mesenchymal cells during valvulogenesis. We found that the expression of Snail was dramatically decreased in HB^<del/del> mutant valves during remodeling process in valvulogenesis. Exogenously introduced Snail and HB-EGF into the HB^<del/del> mutant valves were able to rescue the overproliferation of mesenchymal cells. These results demonstrate that HB-EGF inhibits proliferation of mesenchymal cells via Snail during valve remodeling. (Manuscript in preparation)3) Perinatal distal lung development: another physiological process in which HB-EGF induces cell growth inhibition. HB^<del/del> newborns displayed abnormally thick alveolar walls, occurring from E18.5, that reduced the terminal saccular space area, with a increase in cell proliferation, indicating that HB-EGF suppresses distal lung cell proliferation. Furthermore, an analysis of alveolar morphology and proliferation in HB-EGF and TGFα double mutant newborns revealed that HB-EGF and TGFa function synergistically in this suppression. Crosses between HB^<del/del> mice and waved 2 mice, a hypomorphic EGFR mutant strain, suggest that HB-EGF and EGFR cooperate in this process. Thus, HB-EGF has a suppressive function that contributes to decelerating distal lung cell proliferation synergistically with TGFa through EGFR in perinatal distal lung development. (Dev. Dyn. 2008, 237, 247-258) Less