Cells isolated from the human cortical interstitium resemble myofibroblasts and bind neutrophils in an ICAM-1-dependent manner

Progressive renal disease is frequently accompanied by renal interstitial inflammation and fibrosis in which the activity of resident fibroblasts may be of central importance. Because there are relatively few fibroblasts in the normal cortical interstitium and there is no specific marker to permit their identification, these cells have proved difficult to characterize in vitro. In this study, these cells were isolated and established in culture, using CD90 as a positive selection marker. Antibodies to CD90 bound to tubular epithelial cells and fibroblasts, but not to glomerular cells in kidney sections. In culture, only fibroblasts were CD90-positive. These normal renal cortical fibroblasts (RCF) were alpha-smooth muscle actin- and vimentin-positive, but desmin-, cytokeratin-, and factor VIII-negative, identifying them as myofibroblasts. They expressed platelet-derived growth factor alpha and beta receptors; CD44; and alpha 2(1), beta(1), and beta 3 integrin chains: this combination of markers was also characteristic of fibroblasts in sections of normal cortex. These cells were positive for ICAM-1 but negative for VCAM-1. Similarly, proliferating or growth-arrested renal cortical fibroblasts (RCF) in culture expressed ICAM-1 but not VCAM-1. The expression of VCAM-1 was detected, however, and that of ICAM-1 was increased on fibroblasts associated with inflammatory infiltrates in sections from fibrotic kidneys, and ICAM-1 and VCAM-1 were upregulated on RCF in culture after incubation with increasing doses of interleukin-1 beta or tumor necrosis factor alpha (maximum between 24 and 48 h). These adhesion molecules were functional, and neutrophils adhered to resting and cytokine-activated RCF. Binding was maximal between 24 and 48 h after cytokine treatment and was inhibited by anti-CD18 antibodies. ICAM-1 is the principal adhesion molecule controlling inflammatory cell infiltration of the interstitium. The study presented here suggests that cortical fibroblasts may be central to the control of this infiltration.