October 29, 2004
American Society of Nephrology (ASN) Renal Week 2004, St. Louis, Missouri
Abstract F-PO919
Poster: Diabetes Mellitus: Pathology, Growth Factors and Extracellular Matrix I

Connective Tissue Growth Factor (CTGF) Expression Level in Podocytes Relates to Glomerular Basement Membrane (GBM) Thickening in STZ-Induced Diabetes Mellitus. P. Roestenberg, R. Verheul, K.M. Lyons, P. Martens, Jaap A. Joles, J. Aten, P.W. Mathieson, M.A. Saleem, F.A. van Nieuwenhoven, R. Goldschmeding. Pathology, UMCU, Utrecht, Netherlands; Nephrology & Hypertension, UMCU, Utrecht, Netherlands; Orthopaedic Surgery, UCLA, Los Angeles, CA; Pathology, AMC, Amsterdam, Netherlands; Academic Renal Unit, University of Bristol, United Kingdom.

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 investigate localization and expression levels of CTGF in relation to ECM accumulation in STZ-induced diabetic CTGF +/- and wildtype (CTGF +/+) mice.

CTGF +/- mice (BalbC/129SV) were crossbred with wildtype C57Bl6/J mice. Type 1 diabetes (DM) was induced by STZ (i.p. 200 mg/kg) in the adult female F1 generation. Female littermates served as controls. After 9 weeks of DM, all mice were uninephrectomized to accelerate progression of DN. Mice were sacrificed after 17 weeks of DM. Localization of CTGF was assessed by ISH. CTGF and ECM protein mRNA levels in renal cortex were determined by Q-PCR. GBM thickness was measured by transmission EM. Also, mesangial matrix accumulation was quantified (PAS staining).

Q-PCR showed that CTGF gene expression levels were 3-fold upregulated in renal cortex of DM +/+ mice as compared to controls. In DM +/- mice, CTGF mRNA was also increased, but remained 2-fold lower than in DM +/+ mice. In contrast to DM +/+ mice (17% increase), GBM thickness in DM +/- mice was not increased as compared to normoglycemic controls. ISH revealed that CTGF expression is mainly localized to podocytes. In addition, in vitro studies showed that fibronectin expression in human podocytes was induced dose-dependently by CTGF. However, albuminuria, mesangial matrix and mRNA levels of fibronectin and collagen IV in total renal cortex were all equally increased in both DM +/+ and +/- mice as compared to normoglycemic controls.

These results indicate that the CTGF expression level in podocytes is involved in DM-related GBM thickening, but does not correlate with albuminuria.

Disclosure - Grant/Research Support: Fibrogen Inc., South San Fransisco, CA, USA