October 31, 2004
American Society of Nephrology (ASN) Renal Week 2004, St. Louis, Missouri
Abstract SU-PO912
Poster: Pathology, Growth Factors and Extracellular Matrix II

Upregulation of Connective Tissue Growth Factor (CTGF) in Glomerular Epithelial Cells of Mice with STZ-Induced Diabetes Mellitus. P. Roestenberg, P. Martens, Jaap A. Joles, C. Trischberger, N. Oliver, W. Usinger, F.A. van Nieuwenhoven, R. Goldschmeding. Pathology, UMCU, Utrecht, Netherlands; Nephrology Hypertension, UMCU, Utrecht, Netherlands; Fibrogen Inc., South San Francisco, CA.

CTGF is a 36-38 kDa secreted protein which is strongly upregulated in fibrotic disorders and has been suggested as a pathogenic factor in the development of diabetic nephropathy (DN). The objective of the present study was to determine the relation between plasma, urinary and renal CTGF levels and development of DN in mice. In addition we investigated the localization of renal CTGF overexpression. Diabetes (DM) was induced in C57Bl6/J mice by STZ (200 mg/kg i.p.). DM mice as well as age-matched controls were sacrificed 9 weeks later. CTGF levels in plasma and urine as well as urinary albumin were determined by ELISA. CTGF gene expression levels in renal cortex were determined by Q-PCR. CTGF IHC was performed and glomerular CTGF protein expression as well as mesangial matrix (MM) and glomerular tuft area were quantified using morphometry (Optimas).

DM mice were proteinuric, and showed increased glomerular tuft area (27%, p=0.01) and MM score (p=0.02). Plasma CTGF levels were increased 3-fold in DM mice (p=0.01) and urinary CTGF levels ranged from 12-186 mg/g creatinine, while urinary CTGF levels in control mice were below 2 mg/g creatinine. Moreover, in DM mice, albuminuria correlated with urinary CTGF excretion (r=0.82, p<0.001). Q-PCR showed that CTGF gene expression levels were upregulated in renal cortex of DM mice as compared to controls. Morphometry showed a 5-fold increase of CTGF positive surface area in glomeruli of DM mice (p=0.038). CTGF positive staining was mainly localized in visceral and parietal epithelial cells of the glomeruli, and less prominent in mesangial cells.

In STZ-induced DM mice, CTGF levels were increased in plasma, urine and renal tissue. Urinary CTGF excretion correlated with albuminuria, the main characteristic of DN. Overexpression of CTGF was localized in the kidney, in particular in glomerular epithelial cells. In the context of the known profibrotic activity of CTGF, these findings suggest a role for CTGF in the development of DN.

Disclosure - Grant/Research Support: Fibrogen Inc.