Collagen XIII Induced in Vascular Endothelium Mediates α1β1 Integrin-Dependent Transmigration of Monocytes in Renal Fibrosis

Alport syndrome is a common hereditary basement membrane disorder caused by mutations in the collagen IV alpha 3, alpha 4, or alpha 5 genes that results in progressive glomerular and interstitial renal disease. Interstitial monocytes that accumulate in the renal cortex from Alport mice are immunopositive for integrin alpha 1 beta 1, while only a small fraction of circulating monocytes are immunopositive for this integrin. We surmised that such a disparity might be due to the selective recruitment of a-OIL-positive monocytes. In this study, we report the identification of collagen XIII as a ligand that facilitates this selective recruitment of alpha 1 beta 1 integrin-positive monocytes. Collagen XIII is absent in the vascular endothelium from normal renal cortex and abundant in Alport renal cortex. Neutralizing antibodies against the binding site in collagen XIII for alpha 1 beta 1 integrin selectively block VLA1-positive monocyte migration in transwell assays. Injection of these antibodies into Alport mice slows monocyte recruitment and protects against renal fibrosis. Thus, the induction of collagen XIII in endothelial cells of Alport kidneys mediates the selective recruitment of alpha 1 beta 1 integrin-positive monocytes and may potentially serve as a therapeutic target for inflammatory diseases in which lymphocyte/monocyte recruitment involves the interaction with alpha 1 beta 1 integrin. (Am J Pathol 2010, 177:2527-2540; DOI: 10.2353/ajpath.2010.100017)