Integrins are matrix receptors that regulate cell-matrix interactions during development and in adult tissue. In the adult kidney, the ␣8 chain is specifically expressed in glomerular mesangial cells and vascular smooth muscle cells. ␣8deficient (␣8Ϫ/Ϫ) mice demonstrate reductions in renal mass, which can range from complete renal agenesis to the development of kidneys that are only slightly smaller than wild-type kidneys. No histologic abnormalities of these kidneys have been described.

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... , considering the prominent expression of ␣8 in glomeruli and renal vessels, it seemed unlikely that the kidneys of ␣8Ϫ/Ϫ mice would be completely normal. Therefore, the renal phenotype of adult ␣8Ϫ/Ϫ mice was investigated, for assessment of more subtle morphologic alterations in kidney tissue. ␣8Ϫ/Ϫ mice displayed a significant reduction in nephron number and an increase in glomerular volume, compared with wild-type control animals. Albuminuria was not different in wild-type and ␣8Ϫ/Ϫ mice. Quantitative morphologic analyses revealed that the glomeruli of ␣8Ϫ/Ϫ mice were hypercellular, with an increased number of mesangial cells, compared with wild-type mice. Mesangial matrix deposition (as demonstrated for collagen IV and the ␣8