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

Abstract

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 ϭ 9), moderate (grade II; n ϭ 10), and severe (grade III; n ϭ 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.

Glomerular expression of platelet-derived growth factor (PDGF)-A, -B chain and PDGF receptor-?, -? in human diabetic nephropathy

“…However, it has been reported that several cytokines are produced by mesangial cells and epithelial cells in glomeruli with DN. 23,27,28 Therefore, PDGF-A and PDGFR-α may be synthesized mainly by glomerular mesangial and epithelial cells in DN. Infiltrating monocytes are frequently observed in DN.…”

Connective Tissue Growth Factor Expressed in Tubular Epithelium Plays a Pivotal Role in Renal Fibrogenesis

“…Several downstream mediators of the profibrotic action of TGF-␤ have been proposed (4,24). One such mediator is CTGF, which was detected at the mRNA level not only in glomerular cells but also in tubular epithelial cells and interstitial cells in a variety of chronic renal diseases (5,6). We previously reported that a high dose of hepatocyte growth factor (HGF) attenuated the induction of CTGF by TGF-␤1 in tubular epithelial cells and that this was at least partially responsible for the significant suppression of renal interstitial fibrosis seen in the remnant kidney of SNx model under HGF treatment (7,10).…”

“…Their findings, coupled with ours, support the notion that CTGF acts as an important profibrotic mediator of TGF-␤'s effects in the renal tubulointerstitium while not eliminating the possibility that it plays a similar role in the glomerulus. In fact, a number of studies have shown that mesangial CTGF expression plays a role in the pathogenesis of glomerulosclerosis, especially in diabetic nephropathy (5,6,11,25,36). Because intravenously injected antisense ODN is not appreciably absorbed by glomerular cells, it cannot significantly block their expression of the target genes (14,15).…”

“…CTGF expression has been shown to increase in a variety of human diseases and experimental disease models that are characterized by fibrosis, including those that affect the kidney, skin, blood vessels, lung, and liver (1,2). In the case of the kidney, CTGF mRNA was shown to be expressed primarily in glomerular mesangial, epithelial, and endothelial cells in IgA nephropathy, focal and segmental glomerulosclerosis, and diabetic nephropathy (5,6). Moreover, CTGF mRNA overexpression was found in tubular epithelial cells and interstitial cells at sites of chronic interstitial damage (5,6).…”

“…In the case of the kidney, CTGF mRNA was shown to be expressed primarily in glomerular mesangial, epithelial, and endothelial cells in IgA nephropathy, focal and segmental glomerulosclerosis, and diabetic nephropathy (5,6). Moreover, CTGF mRNA overexpression was found in tubular epithelial cells and interstitial cells at sites of chronic interstitial damage (5,6). In the remnant kidney of the subtotal nephrectomy (SNx) model and in the kidneys with ureteral obstruction, tubular CTGF was shown to be expressed in response to renal interstitial fibrosis (7,8).…”