Localization and roles of CD44, hyaluronic acid and osteopontin in IgA nephropathy

An important function of CD44 is to act as a cellular receptor for hyaluron ic acid and osteopontin. Cell-matrix interactions mediated by the CD44/hyal uronic acid receptor-ligand pair are involved in the regulation of leukocyt e migration and activation. Osteopontin is a molecule associated with cell adhesion and migration and functions through binding to CD44. This study ex amined whether CD44, hyaluronic acid and osteopontin participate in the pro gression of IgA nephropathy. CD44 was expressed in mesangial cells, crescen ts, tubular cells and interstitial infiltrating cells in areas of tubuloint erstitial injury. Hyaluronic acid was deposited in the capillary tuft of ad hesion, crescents and the periglomerular area, and around damaged tubules. Osteopontin was expressed in tubular cells and interstitial infiltrating ce lls in areas of tubulointerstitial injury. The glomerular and interstitial deposition of hyaluronic acid correlated with the glomerular and interstiti al expression of CD44. The interstitial expression of CD44 correlated with the interstitial expression of osteopontin. The expression of both CD44 and osteopontin in the interstitium correlated with the extent of tubulointers titial damage. The expression of CD44 in the interstitium correlated with t he severity of chronic glomerular lesions. The glomerular and interstitial CD44 and hyaluronic acid expression correlated with proteinuria, and inters titial CD44 and hyaluronic acid expression correlated with creatinine clear ance rate. In summary, this study suggests that CD44 participates in the pr ogression of IgA nephropathy by binding hyaluronic acid and osteopontin. Co pyright (C) 2001 S. Karger AG, Basel.