Lpar1經由Vegfc/Vegfr-3調控斑馬魚淋巴管新生成

Abstract

水解磷酸酯第一型受體(lysophosphatic acid receptor 1, Lpar1)因其在內皮細胞內之高度表現一直被認為對血管發育有重要影響，然而在其基因剔除小鼠試驗中卻未發現有明顯血管方面的缺陷。本實驗室之前研究中發現弱化lpar1的蛋白質表現會造成斑馬魚胚產生額面軟骨異常，及嚴重的水腫現象。此嚴重的水腫現象來自於淋巴系統發育的異常而導致胸管的消失。因此在本研究中我嘗試分析Lpar1在斑馬魚胚胎發育時的基因表現以及調節淋巴管發育的訊息傳遞路徑。lpar1表現於背大動脈，且與淋巴管發育因子vegfc的表現位置相重疊。抑制lpar1的表現除可抑制胸管形成，還會造成背大動脈與後尾靜脈間的距離短縮。即時聚合酶連鎖反應定量分析顯示vegfc在lpar1表現受抑制的幼魚中有被抑制的現象，而另一可能淋巴管發育因子lyve-1 like則無。Cox2可為LPA所活化，而抑制Cox2之功能亦能發現斑馬魚胸管發育產生缺陷，然而異位表現低劑量的cox2並無法回復此缺陷。綜合以上結果，我認為Lpar1可能經由調控vegfc的表現影響淋巴管新生成，但Lpar1究竟如何調節vegfc的表現有待進一步試驗之證明。

Lysophosphatic acid receptor 1 (Lpar1) has been suggested to have some roles in vascular development because of its high expression in endothelial cells (ECs). However, no significant defect in vascular development was observed in lpar1-knockout mice. We have previously demonstrated that knockdown of lpar1 causes craniofacial cartilage distortion and serious edema in zebrafish. Edema was resulted from the defect in lymphangiogenesis, so I intended to further analyze the expression and regulatory mechanism of Lpar1 in lymphangiogenesis during embryonic development. lpar1 was expressed in dorsal aorta where a lymphatic factor, vegfc, was also expressed. Knockdown of lpar1 caused narrowed space between dorsal aorta and posterior caudal vein. Real-time PCR analysis showed that vegfc but not another lymphatic factor lyve-1 like was reduced in lpar1 morphants. Inhibition of cyclooxygenase-2 (Cox2) caused similar defects in lymphangiogenesis as that in the lpar1 morpholino-injected embryos, but it was unable to be rescued by ectopic expression of cox2 at low dosage. From the results, I suggested that Lpar1 may regulate the expression of vegfc and affect the formation of lymphatic vessels, but its regulatory mechanism remains unclear.