Gremlin：慢性移植肾肾病中上皮-间质转化和纤维化的新型介质

Gremlin: a novel mediator of epithelial mesenchymal transition and fibrosis in chronic allograft nephropathy.

作者信息

Carvajal G, Droguett A, Burgos M E, Aros C, Ardiles L, Flores C, Carpio D, Ruiz-Ortega M, Egido J, Mezzano S

机构信息

Division of Nephrology, School of Medicine, Universidad Austral, Valdivia, Chile.

出版信息

Transplant Proc. 2008 Apr;40(3):734-9. doi: 10.1016/j.transproceed.2008.02.064.

DOI:10.1016/j.transproceed.2008.02.064

PMID:18455002

Abstract

BACKGROUND

Chronic allograft nephropathy (CAN) is the most frequent cause of chronic dysfunction and late loss of renal allografts. Epithelial mesenchymal transition (EMT) has been identified as responsible for the presence of activated interstitial fibroblasts (myofibroblasts) and transforming growth factor beta (TGF-beta)/Smad is the key signaling mediator. It has been proposed that the bone morphogenetic protein 7 (BMP-7) antagonist, Gremlin, could participate in EMT, as a downstream mediator of TGF-beta.

METHODS

We evaluated 33 renal allograft biopsies, 16 of which showed CAN, versus 17 controls. By in situ hybridization we studied the expression of TGF-beta and Gremlin mRNA. Gremlin, BMP-7, E-cadherin, and alpha-smooth muscle actin (alpha-SMA) proteins were evaluated by immunohistochemistry and Smad3 activation by Southwestern. In cultured human tubuloepithelial cells (HK2 cell line), Gremlin induction by TGF-beta was studied by confocal microscopy.

RESULTS

Among renal biopsies of transplanted patients with CAN, we detected up-regulation of TGF-beta in colocalization with Gremlin (RNA and protein), mainly in areas of tubulointerstitial fibrosis. In the same tubules, we observed decreased expression of E-cadherin and induction of vimentin and alpha-SMA. BMP-7 was significantly decreased in the CAN biopsies. In addition, HK2 stimulated with TGF-beta (1 ng/mL) induced Gremlin production at 72 hours.

CONCLUSION

We postulated that Gremlin is a downstream mediator of TGF-beta, suggesting a role for Gremlin in EMT observed in CAN.

摘要

背景

慢性移植肾肾病（CAN）是移植肾慢性功能障碍和晚期失功最常见的原因。上皮-间质转化（EMT）被认为是活化的间质成纤维细胞（肌成纤维细胞）产生的原因，而转化生长因子β（TGF-β）/Smad是关键信号介质。有人提出，骨形态发生蛋白7（BMP-7）拮抗剂Gremlin可能作为TGF-β的下游介质参与EMT。

方法

我们评估了33例移植肾活检标本，其中16例显示为CAN，17例为对照。通过原位杂交研究TGF-β和Gremlin mRNA的表达。通过免疫组织化学评估Gremlin、BMP-7、E-钙黏蛋白和α-平滑肌肌动蛋白（α-SMA）蛋白，并通过蛋白质免疫印迹法评估Smad3的激活情况。在培养的人肾小管上皮细胞（HK2细胞系）中，通过共聚焦显微镜研究TGF-β诱导的Gremlin表达。

结果

在患有CAN的移植患者的肾活检标本中，我们检测到TGF-β与Gremlin（RNA和蛋白）共定位上调，主要在肾小管间质纤维化区域。在同一肾小管中，我们观察到E-钙黏蛋白表达降低，波形蛋白和α-SMA诱导表达。CAN活检标本中BMP-7显著降低。此外，用TGF-β（1 ng/mL）刺激HK-2细胞72小时可诱导Gremlin产生。