Localization of connective tissue growth factor mRNA in human diabetic nephropathy by in situ hybridization

Background. Progressive expansion of the mesangial matrix is one of the most characteristic histological features of diabetic nephropathy (DN). Connective tissue growth factor (CTGF) is an important factor in the pathogenesis of mesangial matrix expansion and progressive glomerulosclerosis. Methods. To evaluate the expression and localization of CTGF mRNA in the renal tissues of 23 patients with DN and in normal human kidney (NHK), high-resolution in situ hybridization, using a digoxigenin-labeled oligonucleotide, was performed. The patients with DN were classified into three groups based on the histopathological severity of the DN: mild (grade I; n = 9), moderate (grade II; n = 10), and severe (grade III; n = 4). Mesangial expansion and tubulointerstitial injury were evaluated histologically. To quantitate the expression of CTGF mRNA, all nuclei as well as nuclei surrounded by CTGF-positive cytoplasm, in at least ten randomly selected cross-sections of nonsclerotic glomeruli were counted, and the results were expressed as a percentage of the total number of glomerular cells. Results. In both DN and NHK, CTGF mRNA was expressed mainly in intrinsic glomerular cells, including glomerular mesangial cells, epithelial cells and cells of Bowman's capsule. In the tubulointerstitial area, some tubules, particularly atrophic tubules, and some infiltrating cells in DN, were positively stained for CTGF mRNA, especially in DN grade III. The percentage of CTGF mRNA-positive cells was significantly higher in DN than in NHK, and the percentage of these cells was higher in grades I and II DN than in grade III DN. Conclusions. Our results suggest that the expression of CTGF mRNA may be associated with the development and progression of human diabetic nephropathy.