Stem cell factor and crescentic glomerulonephritis.

BACKGROUND: Numerous cells and cytokines have been implicated in the pathogenesis of crescentic glomerulonephritis (CGN). Recently, there has been growing awareness of the role of mast cells and their growth factor, stem cell factor (SCF), in the process of tissue inflammation and fibrosis. METHODS: In this study, renal biopsy specimens from 28 patients with a histopathologic diagnosis of CGN were evaluated immunohistochemically for the presence of mast cells, SCF, and its receptor (c-kit). In addition, CD34+ hematopoietic cells, monocytes (CD68+ cells), and myofibroblasts (alpha-smooth muscle actin-positive [alpha-SMA+] cells) were counted. Renal biopsy specimens from cadaveric kidney donors and kidneys removed for hypernephroma (n = 6) served as controls. Point counting of positive immunostaining for SCF, alpha-SMA, and collagens III and IV was undertaken. Glomerular and interstitial fibrosis (IF) scores were determined. RESULTS: Patients who developed progressive chronic kidney failure showed a significant increase in percentage of crescents, number of interstitial c-kit+ cells, and glomerular CD68+ cells compared with those with a favorable outcome. Analysis showed a significant elevation of tryptase+ mast cells in the interstitium of renal biopsy specimens of patients with CGN compared with controls. SCF and c-kit+ cells were found in glomeruli and interstitium, with occasional immunostaining of the crescent with SCF. Both glomerular and interstitial SCF immunostaining was significantly higher in biopsy specimens of patients compared with controls. Glomerular and interstitial SCF showed a significant positive correlation with 24-hour urinary protein level. There were a few CD34+ cells in both glomeruli and interstitium, but their numbers did not differ between patients and controls. Colocalization of CD34+ and c-kit+ was seen in some rounded interstitial and spindle-shaped cells. Number of interstitial mast cells proved to be a strong predictor of IF. Glomerular SCF correlated negatively with creatinine clearance and positively with glomerular CD68+ cells. Interstitial immunostainable SCF correlated positively with interstitial CD68+ cells and interstitial collagen III. On double antigen labeling, SCF was shown in the vicinity of alpha-SMA+ cells. CONCLUSION: These results show the potential involvement of mast cells and their growth factor SCF/c-kit in CGN.

Effects of caspase inhibition on the progression of experimental glomerulonephritis.

BACKGROUND: Caspase-3 has a central role in the execution of apoptosis. In a nephrotoxic nephritis (NTN) model, we previously demonstrated an up-regulation of caspase-3 that was associated with inappropriate renal apoptosis, inflammation, tubular atrophy, and renal scarring. METHODS: We applied a pan caspase inhibitor, Boc-Asp (OMe)-fluoro-methyl-ketone (B-D-FMK), directly to rat NTN kidney using an intrarenal cannula fed from an osmotic pump. Animals were treated either for the first 7 days (acutely) to determine the effects on renal inflammation (ED-1 staining) and apoptosis (in situ end labeling of fragmented DNA), or for 28 days commencing 15 days after NTN (chronically) to observe the effects on cell death and renal fibrosis. Changes of caspase-3 and caspase-1 activity were detected by fluorometric substrate cleavage assay. Changes in caspase-3 and caspase-1, interleukin-1 beta (IL-1 beta), and collagen I, III, and IV proteins and mRNA were detected by Western blotting and Northern blotting, respectively. RESULTS: In both treated groups, caspase-3 activity was inhibited, and 17 and 24 kD active caspase-3 proteins were reduced significantly. A compensatory increase of caspase-3 mRNA occurred in the acutely treated group, but decreased in the chronically treated group (P < 0.05). Although there were no significant changes in caspase-1 activity and its active protein, the observed decrease in its precursor in the chronic group was increased by treatment (P < 0.05). Further, IL-1 beta precursor and its mRNA were significantly reduced by treatment only in the chronically treated group. Apoptosis was decreased in the glomeruli of acutely treated rats, and in the tubules and interstitium of chronically treated animals (P < 0.05). Glomerular inflammation was decreased only in the acutely treated group, whereas tubulointerstitial inflammation was lowered in both treated groups (P < 0.05). Glomerulosclerosis was reduced in both inhibitor groups, with a reduction in tubulointerstitial fibrosis and collagen I, III, and IV mRNA restricted to chronically treated animals (P < 0.05). Proteinuria was significantly decreased with caspase inhibition in both treated groups, but not serum creatinine level. CONCLUSION: This study clearly indicates that caspase inhibition reduces renal apoptosis, ameliorates inflammation and fibrosis, and improves proteinuria in experimental glomerulonephritis, which may mainly be related to changes in the caspase enzymatic system.