The Role of MIB-1 Expression and Apoptosis in Experimental Crescentic Glomerulonephritis

Kim, Nam Hoon; Kim, Wan Seop; Noh, Jung Woo; Park, Moon Hyang

Abstract

It has been postulated that programmed cell death via apoptosis may be critical for remodelling of glomeruli after inflammatory injury. To understand the regulatory mechanism of apoptosis in experimental crescentic glomerulonephritis (CGN), we examined the MIB-1 score (proliferation index, PI) and apoptotic index during the progression of experimental CGN to end-stage renal failure. CGN was induced in New Zealand White rabbits by administration of guinea pig anti-GBM IgG after sensitization with guinea pig IgG and their kidneys were analyzed for the development of crescents through sequential renal biopsies. Serum creatinine levels progressively increased in a time course until day 45. The PI in glomeruli, tubular epithelial cells, and interstitium progressively increased during the progression of experimental CGN. The mean numbers of MIB-1 positive intraglomerular nuclei (PI) were significantly correlated with degrees of crescent formation and the numbers of apoptotic cells in the glomeruli, tubules, and interstitium. Significant apoptosis was present from day 1 (15.8 10.16 cells/glomerular cross section) and increased in number with the proliferative lesions as glomerular inflammation continued. Moreover, apoptosis increased during the resolution of the glomerular inflammation, and many apoptotic cells were present in the sclerotic lesions in day 17 (18.6 12.99 cells/glomerular cross section). As glomerular inflammation subsided, cellular crescents progressed to fibrous crescents with a reduction of cellularity by day 45. On day 45, the glomerular PI and the numbers of apoptotic cells were markedly decreased. The correlations found in CGN between the creatinine level and the percentage of crescents, between the percentage of crescent and PI, and between the PI and number of apoptotic cells support the hypothesis that there is a change in the glomerular and tubulo-interstitial apoptosis under pathologic conditions. These findings indicate that apoptosis plays an essential role in the resolution of intra- and extraglomerular inflammation and in the elimination of glomerular cells within the sclerotic regions for progressive CGN. The regulation of the apoptotic phenomenon and increased PI during CGN may be important in the progression of glomerular inflammation and the development of pathologic glomerular sclerosis.