Expression of connective tissue growth factor mRNA in human IgA nephropathy

Background. Connective tissue growth factor (CTGF) is a cysteine-rich member of a new family of growth regulators. Its upregulation is an important factor in the pathogenesis of mesangial matrix accumulation and progressive glomerulosclerosis. Methods. We evaluated the expression and localization of CTGF mRNA in renal tissues of 20 patients with IgA nephropathy (IgA-N) and 5 normal human kidneys (NHK), using high-resolution in situ hybridization with digoxigenin-labeled oligonucleotide. The expression level of CTGF mRNA was quantitated by counting all nuclei, as well as nuclei surrounded by CTGF mRNA-positive cytoplasm in at least ten randomly selected cross-sections of nonsclerotic glomeruli, and expressing the results as percentage of positive cells. Results. In both IgA-N and NHK, CTGF mRNA was mainly expressed in glomerular intrinsic cells, including mainly glomerular mesangial and epithelial cells, and some endothelial cells and cells of Bowman's capsule. CTGF mRNA-positive cells were abundant in tubulointerstitial fibrotic areas, especially in IgA-N with severe tissue damage. CTGF mRNA expression was also increased in vascular cells in IgA-N. The percentage of cells positive for CTGF mRNA was significantly higher in IgA-N than in NHK. Furthermore, the percentage of cells positive for CTGF mRNA was significantly greater in IgA-N with moderate mesangial proliferative lesions than in IgA-N with mild mesangial proliferative lesions and/or sclerotic lesions. Conclusions. Our study indicates that CTGF may play an important role in the development and progression of glomerulosclerosis and tubulointerstitial fibrosis in IgA-N.