α_vβ₆ integrin expression in diseased and transplanted kidneys.

Integrins have been implicated in the pathogenesis of a diverse range of kidney diseases. Herein, we provide the first detailed description of an epithelial restricted integrin, α_vβ₆, in kidney biopsies from patients suffering acute and chronic renal diseases and after transplantation.

Immunoperoxidase staining for β₆ was performed on 267 selected biopsy specimens from native (N = 126) and transplanted kidneys (N = 141) and scored semiquantitatively. The site of β₆ expression in tubules was determined using haematoxylin counterstaining and by colocalization with Tamm-Horsfall protein. Comparisons were made between subcategories of diseases of native kidneys and between “service” and “protocol” biopsies of transplanted kidneys.

β₆, when present, is largely confined to the distal tubules and collecting ducts, colocated with Tamm-Horsfall protein. When sparsely present, it was often restricted to the tubular segment associated with the juxtaglomerular apparatus. It was found in tubular cells shed into the urine. β₆ was not expressed in thin membrane nephropathy, or in nonproliferative forms of glomerulonephritis, with the exception of focal and segmental glomerulosclerosis (FSGS). It was diffusely expressed where there was glomerular necrosis or thrombosis and in most forms of acute or chronic tubulointerstitial disease. β₆ was diffusely up-regulated in allografts biopsied for delayed function, in almost all kidneys that have clinical or subclinical rejection episodes and was prominent in chronic allograft nephropathy.

β₆ integrin is not normally expressed in adult native or transplanted kidneys but is commonly up-regulated in the distal tubule in disease. Our descriptive study suggests that it is a molecule worthy of further study.