HUMAN SIMPLE RENAL CYST FLUID CONTAINS A CYST FORMATION-PROMOTING ACTIVITY FOR MADIN-DARBY CANINE KIDNEY-CELLS CULTURED IN COLLAGEN GEL

Simple renal cysts are commonly observed in the elderly, but few exami nations have been performed to study the mechanism of this disease. We have previously shown that simple renal cyst fluid contains some grow th factors, including epidermal growth factor (EGF; less than 54 pg mL (-1)) and insulin-like growth factor I (IGF-I; 30-2070 pg mL(-1)) (M. Taide et al. Clin Chim Acta, 1993:217:199-203). In ;his report, the bi ological significance of growth factors or of human simple renal cyst fluid on the formation of renal epithelial cyst was determined using M adin-Darby canine kidney (MDCK) cells cultured in collagen gel. Both E GF (200 pg mL(-1) or more) and IGF-I (100 pg mL(-1) or more) were foun d to stimulate cyst formation in MDCK cells. Additionally, 12/21 human simple renal cyst fluid samples were found to be capable of stimulati ng cyst formation in MDCK cells. This activity was due to a heat- and acid-labile protein and not inhibited by the anti-IGF-I neutralizing a ntibody. These results indicate that in some instances simple renal cy st fluid would thus appear to contain specific activity for cyst forma tion, which may affect cyst formation in vivo.