Department of Nephrology and Rheumatology, Gunma University Graduate School of Medicine, Maebashi, Japan.
PLoS One. 2019 Mar 7;14(3):e0212991. doi: 10.1371/journal.pone.0212991. eCollection 2019.
Tubulogenesis, the organization of epithelial cells into tubular structures, is an essential step during renal organogenesis as well as during the regeneration process of renal tubules after injury. In the present study, endothelial cell-derived factors that modulate tubule formation were examined using an in vitro human tubulogenesis system. When human renal proximal tubular epithelial cells (RPTECs) were cultured in gels, tubular structures with lumens were induced in the presence of hepatocyte growth factor (HGF). Aquaporin 1 was localized in the apical membrane of these tubular structures, suggesting that these structures are morphologically equivalent to renal tubules in vivo. HGF-induced tubule formation was significantly enhanced when co-cultured with human umbilical vein endothelial cells (HUVECs) or in the presence of HUVEC-conditioned medium (HUVEC-CM). Co-culture with HUVECs did not induce tubular structures in the absence of HGF. A phospho-receptor tyrosine kinase array revealed that HUVEC-CM markedly enhanced phosphorylation of Ret, glial cell-derived neurotrophic factor (GDNF) receptor, in HGF-induced tubular structures compared to those without HUVEC-CM. HUVECs produced GDNF, and RPTECs expressed both Ret and GDNF family receptor alpha1 (co-receptor). HGF-induced tubule formation was significantly enhanced by addition of GDNF. Interestingly, not only HGF but also GDNF significantly induced phosphorylation of the HGF receptor, Met. These data indicate that endothelial cell-derived GDNF potentiates the tubulogenic properties of HGF and may play a critical role in the epithelial-endothelial crosstalk during renal tubulogenesis as well as tubular regeneration after injury.
管状形成，即将上皮细胞组织成管状结构，是肾脏器官发生以及肾脏小管损伤后再生过程中的一个必要步骤。在本研究中，使用体外人管状形成系统研究了调节管状形成的内皮细胞衍生因子。当人肾近端小管上皮细胞（RPTEC）在凝胶中培养时，在肝细胞生长因子（HGF）存在的情况下诱导具有腔的管状结构。水通道蛋白 1 位于这些管状结构的顶膜上，表明这些结构在形态上与体内的肾小管等效。当与人脐静脉内皮细胞（HUVEC）共培养或存在 HUVEC 条件培养基（HUVEC-CM）时，HGF 诱导的管状形成显著增强。在没有 HGF 的情况下，与 HUVEC 共培养不会诱导管状结构。磷酸化受体酪氨酸激酶阵列显示，与没有 HUVEC-CM 的情况相比，HUVEC-CM 显著增强了 HGF 诱导的管状结构中 Ret 和神经胶质细胞源性神经营养因子（GDNF）受体的磷酸化。HUVEC 产生 GDNF，而 RPTEC 表达 Ret 和 GDNF 家族受体 alpha1（共受体）。添加 GDNF 可显著增强 HGF 诱导的管状形成。有趣的是，不仅 HGF 而且 GDNF 显著诱导了 HGF 受体 Met 的磷酸化。这些数据表明，内皮细胞衍生的 GDNF 增强了 HGF 的管状形成特性，并且可能在肾脏小管形成期间的上皮-内皮细胞串扰以及损伤后管状再生中发挥关键作用。
