VASCULAR ADVENTITIAL CELL EXPRESSION OF COLLAGEN-I MESSENGER-RIBONUCLEIC-ACID IN ANTIGLOMERULAR BASEMENT-MEMBRANE ANTIBODY-INDUCED CRESCENTIC NEPHRITIS IN THE RABBIT - A CELLULAR SOURCE FOR INTERSTITIAL COLLAGEN-SYNTHESIS IN INFLAMMATORY RENAL-DISEASE

BACKGROUND: Scarring in the interstitial compartment of the renal cort ex heralds a poor prognosis in many forms of renal injury, however, th e mechanism through which glomerular inflammation leads to interstitia l scarring is not understood. In a model of anti-GBM disease in the ra bbit, development of crescentic glomerulonephritis is associated with marked interstitial fibrosis and decreased renal function. We previous ly demonstrated that collagen accumulation in the model was preceded b y increases in collagen I and IV mRNA and that these changes were prim arily extraglomerular at early time points when inflammation was predo minantly intraglomerular. In order to identify the cellular origins of extraglomerular collagen synthesis in this model, in situ hybridizati on using an alpha2(1) procollagen probe was performed. EXPERIMENTAL DE SIGN: A 602 bp rabbit alpha2(1) procollagen cDNA was cloned using a PC R strategy and sequenced. The nucleotide sequence of the coding region was 94% identical with the human alpha2(1) procollagen sequence. Nort hern blots were performed to define conditions of specific hybridizati on of the anti-sense riboprobe. Tissue sections from normal rabbit kid neys and from kidneys 4, 5, 7, 10 and 14 days after injection of anti- GBM antibody were hybridized with S-35-labeled sense and anti-sense ri boprobes. Cells containing alpha2(1) mRNA were identified by autoradio graphy and mRNA abundance was quantitated by grain density. RESULTS: N o specific hybridization was detected with the sense probe at any time . Alpha2(I) mRNA was undetectable with the anti-sense probe in normal kidney sections. In contrast, the anti-sense probe hybridized specific ally at all time points after induction of anti-GBM disease. In agreem ent with previous filter hybridization studies, on day 4, when inflamm ation was predominantly intraglomerular, cells in the periarterial adv entitial compartment of renal cortex hybridized strongly. At later tim e points, labeling was also present in the interstitial spaces, the pe riglomerular region, in Bowman's space and in the glomerular tuft itse lf. CONCLUSIONS: We conclude that perivascular adventitial cells are a mong the first to respond to glomerular inflammation and represent a p ool of cells that subsequently contribute to interstitial and glomerul ar scarring.