High collagen I gene expression as an independent predictor of adverse renal outcomes in lupus nephritis patients with preserved renal function.

CONTEXT: The deposition of extracellular matrix is a major pathogenic mechanism leading to fibrosis and progressive decline in renal function in patients with lupus nephritis (LN). Currently, available clinicopathologic features cannot predict renal outcome consistently. OBJECTIVE: To test that the expression of renal fibrogenic genes correlates with renal fibrosis at the time of biopsy and is predictive of renal outcomes. DESIGN: Renal gene expression levels of transforming growth factor ß-1 (TGFB1), and collagen I (COL1) were studied by real-time multiplex quantitative polymerase chain reaction in a prospective cohort of patients with LN (n = 39). Extracellular matrix index (ECMI) and collagen I/III matrix index were measured from Picro-Sirius Red-stained slides under normal and polarized light, respectively. RESULTS: After follow-up (median, 43.9 months), renal failure (50% reduction in glomerular filtration rate [GFR] or dialysis) had developed in 13 subjects. The expression levels of renal fibrogenic genes were increased as compared to controls without LN. COL1 correlated with collagen I/III matrix index at baseline. Both high expression of TGFB1 or COL1 tended to predict renal failure by univariate analysis. By multivariate analysis, high ECMI and low GFR were predictive of renal failure. In patients with baseline GFR of 60 mL/min/1.73 m(2) or greater, high renal COL1 expression was an independent (hazard ratio = 4.4, P = .04) predictor of renal failure. CONCLUSIONS: High renal COL1 expression is a strong predictor of adverse renal outcome in patients with LN and preserved baseline GFR. These findings support larger prospective studies to confirm the benefits of COL1 in identifying patients at high risk of progression to renal disease.

Reversibility of structural and functional damage in a model of advanced diabetic nephropathy.

The reversibility of diabetic nephropathy remains controversial. Here, we tested whether replacing leptin could reverse the advanced diabetic nephropathy modeled by the leptin-deficient BTBR ob/ob mouse. Leptin replacement, but not inhibition of the renin-angiotensin-aldosterone system (RAAS), resulted in near-complete reversal of both structural (mesangial matrix expansion, mesangiolysis, basement membrane thickening, podocyte loss) and functional (proteinuria, accumulation of reactive oxygen species) measures of advanced diabetic nephropathy. Immunohistochemical labeling with the podocyte markers Wilms tumor 1 and p57 identified parietal epithelial cells as a possible source of regenerating podocytes. Thus, the leptin-deficient BTBR ob/ob mouse provides a model of advanced but reversible diabetic nephropathy for further study. These results also suggest that restoration of lost podocytes is possible but is not induced by RAAS inhibition, possibly explaining the limited efficacy of RAAS inhibitors in promoting repair of diabetic nephropathy.

Connective tissue growth factor gene expression and decline in renal function in lupus nephritis.

In lupus nephritis (LN), kidney inflammation may be followed by fibrosis and progressive decline in function. Transforming growth factor (TGF)-ß is a notable mediator of fibrosis, but it has other beneficial roles, thus indicating a need for alternate therapeutic targets for inhibition of fibrosis. Connective tissue growth factor (CTGF) acts as a downstream mediator of TGF-ß in promoting fibrosis, without mediating the immunosuppressive effects of TGF-ß. Animal studies show that CTGF may have important roles in renal fibrosis, but data are limited in human subjects. The present study tested the hypothesis that renal CTGF mRNA expression is related to TGF-ß1 and collagen I expression and is predictive of renal function deterioration in patients with LN (n=39). Gene expression was measured using multiplex real-time quantitative RT-PCR and renal function was estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) glomerular filtration rate (GFR) equation. Decline in GFR was assessed by regression of GFR at biopsy to 1 year following biopsy. CTGF mRNA expression was significantly correlated with TGF-ß1 and collagen I. GFR at biopsy was 89.2±39.2 ml/ min. Renal CTGF mRNA expression correlated inversely with baseline GFR. Renal CTGF mRNA was significantly higher in patients with moderate to severe CKD compared to those in the milder CKD group (low GFR 4.92±4.34 vs. high GFR 1.52±1.94, p<0.005). CTGF mRNA was also higher in patients with subsequent decline in GFR [GFR decline (5.19±4.46) vs. no GFR decline (1.79±1.97); P<0.01]. In conclusion, renal expression of CTGF was positively related to TGF-ß1 and collagen I in patients with LN. Furthermore, high CTGF mRNA expression was associated with poor GFR at baseline and subsequent deterioration of kidney function. CTGF expression in the kidney may serve as an early marker for renal disease progression and could be evaluated as a target for therapeutic intervention to prevent renal failure in LN.