Neural cell adhesion molecule expression on renal interstitial cells

Background. At early stages of kidney development, the neural cell adhesion molecule (NCAM) is highly expressed on cells of the metanephrogenic mesenchyme. During maturation of the fetal kidney, NCAM gradually disappears. So far, it has been widely accepted that NCAM in the adult kidney is only expressed by nerves, and not by other cell types. Methods. NCAM expression was analysed in human adult healthy and diseased kidneys by immunohistochemistry and western blot analysis. NCAM+ renal interstitial cells were further characterized by double immunofluorescent staining using antibodies against neurofilaments, a smooth muscle actin, vimentin, alpha 5 beta 1 integrin, CD68, CD11c, HLA-DR and the potential progenitor cell markers CD34, CD117, CD133, CD24, nestin and cadherin-11. Results. In adult human kidneys, NCAM expression is restricted to rare interstitial cells with dendritic morphology, which are neurofilament-negative and predominantly localized on the corticomedullary junction. They are also negative for fibroblast cell markers, but co-express the haematopoietic stem cell markers CD34 and CD133. The number of NCAM+ interstitial cells increased in the initial phases of interstitial fibrosis. Western blot analysis of renal tissues with incipient interstitial fibrosis tissues showed the expression of the 140 kDa NCAM isoform. Conclusions. These data indicate that a rare subpopulation of NCAM+ interstitial cells could represent renal progenitors, and that NCAM+ interstitial cells can participate in the initial phase of interstitial fibrosis.