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

HB-EGF是EGF生长因子家族中的一员，对肝素和硫酸肝素(HS)有很高的亲和力，并已知参与心脏瓣膜的发育。HB-EGF在此过程中抑制间充质细胞的增殖。在本研究中，我们探讨了HB-EGF抑制心脏瓣膜发育(瓣膜形成)细胞生长的调控机制。1)HB-EGF与HS蛋白多糖(HSPGs)相互作用在瓣膜形成中的意义。我们建立了表达肝素结合结构域截断形式(Hb^&lt；ΔBB&gt；)的转基因小鼠，该分子缺乏HS结合活性。Hb^&lt；ΔBB/ΔBB&gt；小鼠在瓣膜形成过程中心脏瓣膜增大，间充质细胞异常过度增殖，表型与HB-EGF基因缺失(Hb^&lt；DCL/del&gt；)小鼠相似。体外心内膜垫块培养研究表明，Hb-EGF-HSPGs相互作用对Hb-EGF-EGFR信号介导的生长抑制…是必需的间充质细胞增多。这些结果表明，HB-EGF与HSPGs的相互作用促进了心脏瓣膜发育过程中分化的间充质细胞的生长抑制。(手稿准备中)2)HB-EGF和Snail信号负性调节瓣膜形成过程中间充质细胞的增殖。我们发现，在瓣膜形成的重塑过程中，Snail在Hb^&lt；del/del&gt；突变瓣膜中的表达显著降低。将Snail和HB-EGF外源导入Hb^&lt；del/del&gt；突变瓣膜，可挽救间充质细胞的过度增殖。这些结果表明HB-EGF在瓣膜重塑过程中通过Snail抑制间充质细胞的增殖。(手稿准备中)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^&lt；del/del&gt；新生儿从E18.5开始出现异常增厚的肺泡壁，使终末囊腔面积缩小，细胞增殖增加，表明HB-EGF抑制远端肺细胞的增殖。此外，对HB-EGF和转化生长因子α双突变新生儿的肺泡形态和增殖情况的分析表明，HB-EGF和TGFa在这种抑制中具有协同作用。HB^&lt；del/del&gt；小鼠与亚型EGFR突变株Waved 2小鼠的杂交表明，HB-EGF和EGFR在这一过程中协同作用。因此，HB-EGF在围产期远端肺发育中与TGFa通过EGFR协同作用有助于减慢远端肺细胞的增殖。(开发人员)戴恩。2008、237、247-258)减少

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