Basement membrane heparan sulfate proteoglycan is the main proteoglycan synthesized by glomerular epithelial cells in culture.

The production and distribution of basement membrane-type heparan sulfate proteoglycans (BM HSPG) were investigated in a mouse glomerular epithelial cell line. Confluent cell monolayers were radiolabeled with [35S]sulfate or [35S]cysteine. Proteoglycans were isolated from the medium and cell layers by ion exchange chromatography and their nature determined by enzyme digestion (chondroitinase ABC) or degradative treatment (nitrous acid). It was found that more than 80% of the proteoglycans in both the cell layer and medium were heparan sulfate proteoglycans (HSPG) based on their susceptibility to nitrous acid degradation. More than half of the HSPG in the cell layer could be precipitated with an antiserum that specifically recognizes BM HSPG; only 10% of those released into the medium were precipitated with this antiserum. When immunoprecipitates of [35S] sulfate-labeled proteoglycans were analyzed by SDS-PAGE, the mature proteoglycans ran as a broad band at the top of the gel. When immunoprecipitates of [35S]cysteine-labeled proteoglycans were similarly analyzed, a 250 kd precursor core protein band was seen in addition to the mature proteoglycan. When BM HSPG were localized by immunofluorescence and immunoelectron microscopy (immunoperoxidase), they were found intracellularly in biosynthetic compartments (ER and Golgi cisternae) and extracellularly in deposits of basement membrane-like matrix located beneath and between the cells. These results indicate that l) BM HSPG are the predominant type of proteoglycans made by glomerular epithelial cells in culture; 2) these HSPG are assembled into a loosely organized matrix that is deposited beneath and between the cells; and 3) this cell type produces a higher proportion of BM HSPG than other cultured epithelial cells studied previously.     

Glomerular lesions in mice transgenic for growth hormone and insulinlike growth factor-I. I. Relationship between increased glomerular size and mesangial sclerosis.

The glomeruli of mice transgenic for bovine growth hormone (GH mice) were disproportionately enlarged as a function of either kidney or body weight. Glomerular size correlated with mesangial sclerosis and the urine albumin/creatinine ratio. The glomerular lesions consisted of mesangial proliferation (4 to 5 weeks) followed by progressive mesangial sclerosis (19 weeks), resulting in complete glomerulosclerosis at 30 to 37 weeks. Albuminuria paralleled the glomerulosclerosis. In contrast, mice transgenic for insulinlike growth factor-I (IGF-I mice) did not develop glomerulosclerosis, even though glomerular size significantly increased. Glomerular hypertrophy, however, did not reach that in GH mice. These data suggest that high levels of circulating GH lead to a disproportionate increase in glomerular cellularity and volume, as well as glomerulosclerosis. This does not appear to be the result of high levels of circulating IGF-I stimulated by GH, as the serum IGF-I level in GH mice was lower than that in IGF-I mice.     

Pentosan polysulfate treatment reduces cyclosporine-induced nephropathy in salt-depleted rats

BACKGROUND: Long-term cyclosporine (CsA) treatment leads to a decreased glomerular filtration rate, hyalinosis of afferent arterioles, and striped cortical tubulo-interstitial fibrosis. We showed previously that pentosan polysulfate (SP54) prevented the development of microvascular and interstitial lesions in mouse models of progressive glomerulosclerosis. In this study, we examined the effect of pentosan polysulfate on the development of CsA nephropathy. METHODS: Pair-fed Sprague-Dawley rats were fed a low-sodium (0.03%) diet and received CsA (15 mg/kg, subcutaneously, in olive oil)/5% glucose, pentosan polysulfate (10 mg/kg, subcutaneously in 5% glucose) plus CsA, olive oil/pentosan polysulfate, or olive oil/5% glucose for 30 days. Creatinine clearance (CrCl) was determined at three time points. Afferent arteriolar lesions, glomerular volume, and tubulo-interstitial lesions were quantitated. RNA was extracted from cortex. RESULTS: Severe lesions were found in the CsA group. A reduction in the number of affected arterioles (32%) and the degree of chronic tubulo-interstitial lesions (44%) was found in pentosan polysulfate/CsA-treated rats. A 20% decrease in glomerular volume was found in CsA rats, but not in pentosan polysulfate/CsA-treated rats. Pentosan polysulfate treatment did not prevent the CsA-induced decrease in CrCl (approximately 30%) at 4 weeks. CsA did not affect cortical endothelial or neuronal nitric-oxide synthase or mRNA levels, but there was small increase in neuronal nitric-oxide synthase mRNA levels in the pentosan polysulfate/CsA-treated group. CONCLUSIONS: Pentosan polysulfate reduced structural renal lesions in CsA-treated, salt-depleted Sprague-Dawley rats.     

Glomerulosclerosis in mice transgenic for human insulin-like growth factor-binding protein-1

BACKGROUND: The growth hormone (GH)/insulin-like growth factor (IGF) system is thought to participate in the glomerulosclerosis process. Because IGF-binding proteins (IGFBPs) modulate IGF actions and hence GH secretion, this study assessed whether mice transgenic for human IGFBP-1 have altered susceptibility to glomerulosclerosis. METHODS: A line of transgenic mice that express human IGFBP-1 mRNA in the liver under the control of the alpha1-antitrypsin promoter has been obtained, and morphological changes in the kidney tissue were assessed. Glomerulosclerosis was identified using light microscopy, light microscopic morphometry, and electron microscopy. Extracellular matrix components were analyzed by immunohistochemistry. RESULTS: There was a marked increase in mesangial extracellular matrix area in homozygous transgenic mice at three months of age as compared with heterozygous transgenic mice and nontransgenic littermates. These changes were not associated with alterations in glomerular volume or cellularity. The expansion of extracellular matrix area was related to a marked increase in laminin and type IV collagen and to the appearance of type I collagen. CONCLUSIONS: These observations indicate that the enhanced expression of IGFBP-1 may result in the development of glomerulosclerosis without glomerular hypertrophy. The changes are potentially related to a decrease in IGF-I availability and/or to an IGF-I-independent role of IGFBP-1.