Development of renal basement membrane glycoproteins in metanephric organ culture

Because of the importance of renal basement membrane glycoproteins in normal and abnormal tubular and glomerular morphogenesis, structure, and function, the sequential development of fibronectin, GP-2, and entactin was studied in vivo and in a newly developed, serum-free mouse metanephric organ culture system. The organ culture system permits advanced tubular differentiation and glomerular epithelial development of whole metanephros without perfusion or urine formation. Affinity-purified antibodies and immunohistologic techniques were used, and the ontogeny of basement membrane glycoproteins was characterized in vivo and in vitro. It was thus possible to characterize the pattern of normal renal basement membrane glycoprotein production and to comparatively study renal glomerular and tubular basement membrane formation in the presence and the absence of endothelial and/or mesangial influences. Both in vivo and in vitro undifferentiated mesenchyme expressed fibronectin but not GP-2 or entactin. Further, both in vivo and in vitro, all three glycoproteins developed in the basement membranes of the earliest recognizable tubular and glomerular forms. Because of the sharp parallel between in vivo and in vitro basement membrane glycoprotein production we conclude that the whole organ metanephric culture system is a useful model for the study of renal basement membrane development. Further, based on the pattern of in vitro basement membrane production, it may be concluded that tubular and glomerular epithelial cells are capable of producing basement membrane glycoproteins in the absence of endothelial or recognizable mesangial cells following initial embryonic induction.