Morphology and distribution of chandelier cell axon terminals in the mouse cerebral cortex and claustroamygdaloid complex

Chandelier cells represent a unique type of cortical --aminobutityricacidergic interneuron whose axon terminals (Ch-terminals) onlyform synapses with the axon initial segments of some pyramidalcells. Here, we have used immunocytochemistry for the high-affinityplasma membrane transporter GAT-1 and the calcium-binding proteinparvalbumin to analyze the morphology and distribution of Ch-terminalsin the mouse cerebral cortex and claustroamygdaloid complex.In general, 2 types of Ch-terminals were distinguished on thebasis of their size and the density of the axonal boutons thatmade up the terminal. Simple Ch-terminals were made up of 1or 2 rows of labeled boutons, each row consisting of only 3–5boutons. In contrast, complex Ch-terminals were tight cylinder-likestructures made up of multiple rows of boutons. Simple Ch-terminalswere detected throughout the cerebral cortex and claustroamygdaloidcomplex, the complex type was only occasionally found in certainregions, whereas in others they were very abundant. These resultsindicate that there are substantial differences in the morphologyand distribution of Ch-terminals between different areas andlayers of the mouse cerebral cortex. Furthermore, we suggestthat the distribution of complex Ch-terminals may be relatedto the developmental origin of the different brain regions analyzed.     

Association between oestrogen receptor alpha gene polymorphism and mortality in female end-stage renal disease patients.

BACKGROUND: In the general population, genetic variations in the oestrogen receptor alpha (ERalpha) gene may influence lipid abnormalities, cardiovascular disease (CVD), and mortality, but this has not previously been studied in end-stage renal disease (ESRD) patients. METHODS: A total of 227 ESRD (141 men and 86 women) patients starting renal replacement therapy (RRT) were genotyped for three ERalpha gene polymorphisms (Ser10Ser, PvuII and XbaI) and the associations between these polymorphisms and clinical and laboratory parameters and survival were analysed. Patients were followed for a median period of 55 months (range 1-126 months). RESULTS: The PvuII and XbaI polymorphisms were not associated with any of the clinical parameters. The ERalpha Ser10Ser CC genotype was present in 24 (28%) of the female and in 37 (26%) of the male patients. When comparing the CC genotype with the CT and TT genotypes, there were significant differences in lipid levels and inflammatory marker levels, especially in female patients. In female patients, the CC genotype was associated with lower prevalence of protein energy wasting (PEW) (17.4% vs 43.1%; P=0.03), lower median serum triglyceride (1.7 vs 2.1 mmol/l; P=0.001), higher median serum albumin (34.0 vs 32.5 g/l; P=0.03) and lower median high sensitivity-CRP (hsCRP) (2.2 vs 5.5 mg/l; P=0.03) levels compared with the CT plus TT genotypes. In male patients only HDL-cholesterol and ApoA levels were associated with this polymorphism. Whereas this polymorphism did not influence survival in males, the mortality was lower in female patients with the CC genotype (Kaplan-Meier; Log-rank 2.2, P=0.02). Moreover, female patients with the CT plus TT genotypes had a borderline significant increased relative risk (Cox hazard model; 6.6, 95% CI: 0.87-49.9 P=0.06) of death as compared with those with the CC genotype, even after adjustment for age and prevalence of CVD. CONCLUSIONS: Female, but not male ESRD patients with the ERalpha Ser10Ser CC genotype had lower prevalence of PEW, lower serum triglyceride, higher serum albumin and lower hsCRP levels. As this genotype was associated with a significantly decreased risk of all-cause death during the initial years of RRT, its protective properties need further study.     

Chronic allograft nephropathy: expression and localization of PAI-1 and PPAR-gamma.

BACKGROUND: Chronic allograft nephropathy (CAN) is a major cause of loss of renal allografts. Mechanisms postulated to be involved include sequelae of rejection, warm ischaemia time, drug toxicity, ongoing hypertension and dyslipidaemia. Plasminogen activator inhibitor-1 (PAI-1) is implicated not only in thrombosis, but also in fibrosis, by inhibiting matrix degradation, and is expressed in renal parenchymal cells as well as in macrophages. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the steroid receptor superfamily, and plays a major beneficial role in lipid regulation, insulin sensitivity and macrophage function, factors that may play a role in CAN. We therefore studied the expression of these molecules in CAN. METHODS: All renal biopsy/nephrectomy files from Vanderbilt and Nashville VAMC from a 6 year period were reviewed to identify all renal transplant biopsies or nephrectomies more than 6 months after transplant with CAN. CAN was defined as fibrosis in the graft, vascular, interstitial or glomerular. All cases were scored for severity of fibrosis in vasculature (0-3 scale), glomeruli (% affected with either segmental and/or global sclerosis) and interstitial fibrosis (% of sample affected). PAI-1 and PPAR-gamma immunostaining was assessed on a 0-3 scale in glomeruli, vessels and tubules. RESULTS: Eighty-two patients with a total of 106 samples met entry criteria. The population consisted of 59 Caucasians and 23 African-Americans; 49 males, 33 females with average age 37.9+/-1.7 years. Average time after transplant at time of biopsy was 60.5+/-4.9 months (range 7-229). Glomerulosclerosis extent in CAN was on average 26.5+/-2.4% compared with 3.6+/-1.2% in normal control kidneys from native kidney cancer nephrectomies and 0% in transplanted kidney biopsies from patients obtained > or =6 months after transplantation without CAN. Native control kidneys showed mild interstitial fibrosis (8.0+/-1.2%), whereas transplant controls showed very minimal fibrosis (2.0+/-2.0%). Interstitial fibrosis in CAN kidneys was on average 47.9+/-2.4%. Glomerular PAI-1 and PPAR-gamma staining scores were markedly increased in CAN (1.8+/-0.1, 2.3+/-0.1, respectively) compared with normal control kidneys from native kidney cancer nephrectomies (PAI-1 0.2+/-0.2 and PPAR-gamma 0.4+/-0.2, P<0.001) and transplanted kidney biopsies from patients obtained > or =6 months after transplantation without CAN (PAI-1 0 and PPAR-gamma 0, P<0.001). Tubular PAI-1 and PPAR-gamma staining scores were 1.9+/-0.1 and 1.9+/-0.1, respectively, and also increased over both native and transplant kidney controls (0.8+/-0.2 for both categories for PAI-1, 1.2+/-0.2 for both categories for PPAR-gamma, respectively). Vascular sclerosis in CAN was 1.0+/-0.1 with increased PAI-1 and PPAR-gamma scores (1.7+/-0.1, 1.2+/-0.1, respectively) compared with controls. Infiltrating macrophages were increased in CAN, and were positive for both PAI-1 and PPAR-gamma. Biopsies with less sclerosis overall showed a trend for less PAI-1 and PPAR-gamma staining. CONCLUSION: PAI-1 and PPAR-gamma are both increased in CAN compared with non-scarred native or transplant control kidneys. We speculate that altered matrix metabolism and macrophage function might be involved in the development of CAN.     

T gamma/delta lymphocytes in renal transplant recipients.

T gamma/delta lymphocytes are able to perform allospecific cytotoxicity and natural killer cytotoxicity in vitro. However, very little is known about their function in vivo. To investigate the possible involvement of T gamma/delta lymphocytes in the immune response to renal allografts, fine-needle aspiration biopsies and peripheral blood of 15 renal transplant recipients were studied during the first 4 weeks after transplantation. In addition peripheral blood of patients before transplantation, half a year and one year after transplantation was studied. No increase in the percentage of T gamma/delta lymphocytes in the fine-needle aspiration biopsies, including those taken during acute rejection episodes, was found. A significant decrease in the percentage of T gamma/delta lymphocytes was observed in peripheral blood after transplantation. We conclude that T gamma/delta lymphocytes seem to play no major role in the immune response to renal allografts.     

Rosiglitazone ameliorates cisplatin-induced renal injury in mice.

BACKGROUND: Inflammatory mechanisms may play an important role in the pathogenesis of cisplatin nephrotoxicity. Agonists of the peroxisome proliferator-activated receptor-gamma (PPARgamma), such as rosiglitazone, have been recently demonstrated to regulate inflammation by modulating the production of inflammatory mediators and adhesion molecules. The purpose of this study was to examine the protective effects of rosiglitazone on cisplatin nephrotoxicity and to explore the mechanism of its renoprotection. METHODS: Mice were treated with cisplatin with or without pre-treatment with rosiglitazone. Renal functions, histological findings, aquaporin 2 (AQP2) and adhesion molecule expression, macrophage infiltration and tumour necrosis factor-alpha (TNF-alpha) levels were investigated. The effect of rosiglitazone on nuclear factor (NF)-kappaB activity and on viability was examined using cultured human kidney (HK-2) cells. RESULTS: Rosiglitazone significantly decreased both the damage to renal function and histological pathology after cisplatin injection. Pre-treatment with rosiglitazone reduced the systemic levels of TNF-alpha and down-regulated adhesion molecule expression in addition to the infiltration of inflammatory cells after cisplatin administration. Rosiglitazone restored the decreased AQP2 expression after cisplatin treatment. Pre-treatment with rosiglitazone blocked the phosphorylation of the p65 subunit of NF-kappaB in cultured HK-2 cells. Rosiglitazone had a protective effect via a PPARgamma-dependent pathway in cisplatin-treated HK-2 cells. CONCLUSION: These results showed that pre-treatment with rosiglitazone attenuates cisplatin-induced renal damage through the suppression of TNF-alpha overproduction and NF-kappaB activation.     

Hypoxia reduces the expression and anti-inflammatory effects of peroxisome proliferator-activated receptor-gamma in human proximal renal tubular cells.

BACKGROUND: Peroxisome proliferator-activated receptor (PPAR)-gamma may counteract tissue fibrosis via its anti-inflammatory actions, while hypoxia, a new pro-fibrotic factor, reportedly modifies PPAR-gamma expression. However, the effects of hypoxia on the expression and anti-inflammatory actions of PPAR-gamma have yet remained to be clarified in renal tubular cells. METHODS: Confluent human proximal renal tubular epithelial cells (HPTECs) were exposed to hypoxia (1% O2) and/or TNF-alpha at 10 ng/ml for up to 48 h. The cells were incubated with PPAR-gamma agonists, 15d-PGJ2 or pioglitazone, for 30 min before stimulation. Precise amounts of PPAR-gamma and MCP-1 mRNA and protein were measured by TaqMan quantitative PCR and immunoblot or ELISA, respectively. RESULTS: A cDNA array analysis identified PPAR-gamma as one of the hypoxia-affected genes in HPTECs. Hypoxia reduced mRNA levels of PPAR-gamma at 24 and 48 h and protein levels at 6 and 48 h. Knockout of hypoxia-inducible factor-1alpha (HIF-1alpha) with its dominant negative form did not block the hypoxia-induced reduction in PPAR-gamma expression. PPAR-gamma's activation with 15d-PGJ2 or pioglitazone reduced basal and TNF-alpha-stimulated MCP-1 expression at mRNA and protein levels at 24 h under normoxia. MCP-1 reduction rates at basal mRNA and protein levels were slightly but significantly lower during hypoxia than normoxia (9 vs 69% and 36 vs 42%, respectively, for 15d-PGJ2, and 0 vs 34% and 12 vs 21%, respectively, for pioglitazone). Finally, a specific inhibitor for PPAR-gamma, GW9662, weakened the MCP-1-decreasing effect of 15d-PGJ2 by about 30%, under basal conditions, while it abolished the effect of pioglitazone almost completely. CONCLUSIONS: Hypoxia-induced loss of function of PPAR-gamma reduces anti-inflammatory effects of PPAR-gamma activation, possibly modulating inflammatory responses in the diseased kidney.     

Alphav integrin regulates TNF-alpha-induced nitric oxide synthesis in rat mesangial cells--possible role of osteopontin.

BACKGROUND: Tumour necrosis factor-alpha (TNF-alpha) induces nitric oxide (NO) synthesis in rat mesangial cells (MCs). We previously demonstrated that osteopontin (OP), a matrix protein that mainly interacts with the alphav integrin family, increased time-dependently by TNF-alpha stimulation at gene and protein levels. The regulation of NO synthesis by integrins or matrix proteins is unclear. METHODS: We examined whether integrin, especially alphav integrin, regulates NO synthesis in rat MCs and whether OP, an alphav integrin ligand, has an effect on TNF-alpha-induced NO synthesis. Furthermore, OP and inducible NO synthase (iNOS) gene expression was examined by Northern blotting. RESULTS: TNF-alpha increased NO synthesis in MCs in a time-dependent manner. Synthetic GRGDSP peptide, which is known to inhibit various integrins that interact with RGD-containing extracellular matrices, increased TNF-alpha-induced NO levels in a dose-dependent manner. Cyclical RGD peptide, the specific inhibitor of alphav integrin, also exhibited a dose-dependent effect of increasing NO levels, while GRGESP peptide, which has very low affinity to integrins, had no effect. In addition, NO synthesis was found to be significantly reduced when MCs were plated on OP-coated dishes compared to type I or IV collagen-coated dishes. Furthermore, anti-OP antibody increased NO synthesis in MCs. iNOS mRNA levels were increased by TNF-alpha, and were abruptly diminished after OP mRNA was significantly induced. CONCLUSIONS: The present study demonstrated the involvement of alphav integrin in TNF-alpha-induced NO synthesis in rat MCs, and the possible role of OP was suggested in the mechanism. TNF-alpha and extracellular matrices can co-operate to regulate the behaviour of MCs at least partly through NO synthesis, which may participate in the course of glomerular diseases.     

p38 MAPK phosphorylation and NF-kappa B activation in human crescentic glomerulonephritis.

BACKGROUND: p38 mitogen-activated protein kinase (p38 MAPK) followed by the activation of NF-kappa B participates in the intracellular signal transduction and production of cytokines and chemokines. The pathophysiological roles of p38 MAPK and NF-kappa B in human glomerulonephritis, however, remain to be investigated. METHODS: We investigated the phosphorylated p38 MAPK (p-p38 MAPK) and activated NF-kappa B immunohistochemically in the kidneys of 34 patients with crescentic glomerulonephritis and 26 control patients with thin basement membrane disease and minimal change nephrotic syndrome. We also explored the co-localization of p-p38 MAPK with CCR5, the signal of which leads to p38 MAPK activation. Furthermore, urinary levels of MIP-1 alpha, the cognate ligand for CCR5, were determined by enzyme-linked immunosorbent assay. RESULTS: p-p38 MAPK-positive cells and activated NF-kappa B-positive cells were mainly detected in crescentic lesions, tubular epithelial cells, and interstitial mononuclear infiltrates. The number of p-p38 MAPK-positive cells in patients with crescentic glomerulonephritis was higher than that in control patients. The number of p-p38 MAPK-positive cells in glomeruli was well correlated with the percentage of cellular crescents, the number of CD68-positive cells, and urinary MIP-1 alpha levels. In addition, the number of activated NF-kappa B-positive cells was well correlated with the number of p-p38 MAPK-positive cells in glomeruli. Dual staining revealed that most of CCR5-positive cells were positive for p-p38 MAPK. Finally, p-p38 MAPK-positive cells and activated NF-kappa B-positive cells decreased during glucocorticoid therapy-induced convalescence. CONCLUSIONS: We conclude that the phosphorylation of p38 MAPK associated with the activation of NF-kappa B may be involved in the upregulation of intrarenal MIP-1 alpha and the utilization of CCR5 signalling, which may result in human crescentic glomerulonephritis.     

Inflammatory mediators in human renal dysplasia.

BACKGROUND: Cytokines regulate many processes in the immune system and have recently been implicated in normal organogenesis. We previously demonstrated that the archetypal inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha) is expressed in the murine metanephros, and exogenous TNF-alpha inhibits nephrogenesis and increases macrophage numbers in vitro (Cale et al., Int J Dev Biol 1998; 42: 663-674). The phenotype seen, with an arrest of ureteric bud branching and failure of mesenchymal to epithelial conversion, is similar to human renal dysplasia. Methods and results. In normal human fetal kidneys we demonstrated the presence of macrophages and T cells and also documented TNF receptor expression on ureteric bud derivatives. In contrast to normal tissues, TNF-alpha protein was detected in dysplastic kidneys. This factor was also detected in the urine of fetuses with obstructive uropathy and TNF receptors were expressed in dysplastic tubules. Furthermore, we noted a fetal distribution of macrophages and T cells in dysplastic tissues and persistent expression of the adhesion molecules neural cell adhesion molecule and intercellular adhesion molecule. CONCLUSIONS: We suggest that abnormal expression of cytokines early in renal development dysregulates normal patterns of adhesion molecule expression and inflammatory cells, and may contribute to the pathogenesis of renal dysplasia.     

Plasma concentrations of alpha-melanocyte-stimulating hormone are elevated in patients on chronic haemodialysis.

BACKGROUND: Clinical and/or laboratory signs of systemic inflammation occur frequently in patients undergoing long-term haemodialysis. It is likely, therefore, that a compensatory release of endogenous anti-inflammatory molecules occurs to limit host reactions. The aim of the present research was to determine if the potent anti-inflammatory peptide alpha-melanocyte-stimulating hormone (alpha-MSH), a pro-opiomelanocortin derivative, is increased in plasma of haemodialysis patients. Because endotoxin and cytokines induce alpha-MSH in vivo and in vitro, we also measured plasma concentrations of endotoxin, interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-alpha), and the two circulating products of activated monocytes, nitric oxide (NO) and neopterin. METHODS: Thirty-five chronic haemodialysis patients, 20 patients with chronic renal failure not yet on dialysis, and 35 normal controls were included in the study. In the haemodialysis group, blood samples were obtained before and at the end of a dialysis session. Plasma alpha-MSH was measured using a double antibody radioimmunoassay, and IL-6, TNF-alpha, and neopterin using specific enzyme-linked immunosorbent assays. Plasma nitrites were determined by a colorimetric method, and endotoxin with the quantitative chromogenic LAL (limulus amoebocyte lysate) method. RESULTS: Mean plasma alpha-MSH was higher in haemodialysis patients than in control subjects, with the peptide concentrations being particularly elevated in dialysed patients with detectable endotoxin. High alpha-MSH concentrations were observed in the pre-dialysis samples, with no substantial change at the end of the dialysis session. Plasma concentrations of IL-6, TNF-alpha, neopterin, and NO were generally elevated in chronic haemodialysis patients and there was a negative correlation between circulating alpha-MSH and IL-6. In patients with renal failure not yet on dialysis, mean plasma alpha-MSH was similar to that of normal subjects. CONCLUSIONS: alpha-MSH is increased in the circulation of chronic haemodialysis patients and particularly so in case of detectable endotoxaemia. Reduction of renal clearance is unlikely to contribute to the observed rise of the peptide because alpha-MSH concentration is not increased in patients with chronic renal failure who are not yet on dialysis. It is likely that dialysis-associated endotoxaemia, directly and/or through cytokine release, enhances the production of the anti-inflammatory mediator alpha-MSH that limits host reactions.     

Pentoxifylline suppresses renal tumour necrosis factor-alpha and ameliorates experimental crescentic glomerulonephritis in rats.

BACKGROUND: Crescentic glomerulonephritis is a rapidly progressive form of glomerulonephritis, but treatment remains non-specific. The methylxanthine derivative pentoxifylline (PTX) is a clinically available phosphodiesterase inhibitor with anti-inflammatory and immunoregulatory activities. This study examined whether PTX has beneficial effects in a rat model of anti-glomerular basement membrane (GBM) crescentic glomerulonephritis. METHODS: Experimental crescentic glomerulonephritis was induced in Wistar rats by intravenous injection of rabbit anti-rat GBM serum and treated with either vehicle (phosphate-buffered saline) or PTX (0.1 g/kg/day) intravenously on a daily basis. Groups of six animals were euthanized at days 3, 7, 14 or 28 after induction of disease. Effects of PTX on renal function, histology and expression of cytokines, chemokines and adhesion molecules were determined. RESULTS: Compared with the vehicle-treated nephritic rats, PTX treatment beginning at the start of the nephritis significantly suppressed mRNA expression of tumour necrosis factor (TNF)-alpha, but not interleukin-1 beta, throughout the course of nephritis. Moreover, PTX decreased renal mRNAs for intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), regulated on activation, normal T-cell expressed and secreted (RANTES) and osteopontin (OPN) at all time points examined. These effects were associated with a significant inhibition of macrophage and T-cell infiltration, a reduction of 24-h urinary protein excretion (50-75%, P<0.05), an improvement of histological damage including glomerular crescent formation (60-70%, P<0.01) and a decrease of cortical mRNAs for type I (alpha 1) collagen and fibronectin. The efficacy of PTX could also be seen, though to a lesser extent, in rats with established nephritis. CONCLUSIONS: PTX is an effective anti-inflammatory and immunomodulatory agent capable of suppressing rat crescentic glomerulonephritis. Inhibition of renal TNF-alpha, ICAM-1, RANTES, MCP-1 and OPN expression may be a mechanism whereby PTX suppresses progressive renal injury in rat crescentic glomerulonephritis.     

FcgammaRIIa-131R allele and FcgammaRIIIa-176V/V genotype are risk factors for progression of IgA nephropathy.

BACKGROUND: Fcgamma receptors (FcgammaRs) may play an important role in positive and negative regulation of immune cell responses and immune complex (IC) clearance. Mesangial IgG deposition and circulating IgG/IgA-IC in sera are observed in patients with IgA nephropathy (IgAN). Therefore, the pathological roles of IgG-IC in IgAN have been discussed. On the other hand, several studies have identified FcgammaR polymorphisms (FcgammaRIIa, FcgammaRIIIa and FcgammaRIIIb) that determine susceptibility to autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. The objective of the present study was to clarify whether FcgammaR polymorphisms influence susceptibility to IgAN, clinical features or severity in patients with IgAN. METHODS: Japanese patients with IgAN (n = 124) and healthy controls (n = 100) were genotyped for FcgammaR polymorphisms (FcgammaRIIa-131H or R, FcgammaRIIIa-176F or V and FcgammaRIIIb-NA1 or -NA2). The genotyping of these polymorphisms was performed using allele-specific polymerase chain reaction (PCR) methods. Associations among FcgammaR polymorphisms and susceptibility, age of onset, levels of serum immunoglobulins, intensity of glomerular IgG deposition and pathological severity were analysed. RESULTS: These three FcgammaR polymorphisms showed no significant differences in genotype and allele frequencies between the IgAN patients and healthy controls. Each FcgammaR polymorphism had no influence on age of onset, serum levels of IgG and glomerular IgG deposition in IgAN. However, FcgammaRIIa-131R (R/R or H/R) or FcgammaRIIIa-176V homozygous carriers (V/V) showed significantly more severe injury than FcgammaRIIa-131H homozygous (H/H) (P < 0.03) or FcgammaRIIIa-176F carriers (F/F or F/V) (P < 0.03), respectively. CONCLUSION: The present study shows that polymorphisms of FcgammaRIIa and FcgammaRIIIa influence the severity of IgAN in Japanese patients but not the incidence, suggesting that IgG-IC may play important roles in the progression and prognosis of this disease via FcgammaRs.     

Role of atrophic changes in proximal tubular cells in the peritubular deposition of type IV collagen in a rat renal ablation model.

BACKGROUND: Tubular atrophy, dilation and interstitial fibrosis are common in tubulointerstitial lesions, but the precise roles and inter-relationships of these components in the development of interstitial lesions have not been determined. This study focused on the origin and roles of atrophic tubules in the peritubular deposition of type IV collagen in a rat renal ablation model. METHODS: Male Wistar rats underwent 5/6 nephrectomy or sham operation, and then were sacrificed at 4, 8 or 12 weeks, their remaining kidneys removed for histological and immuno-histochemical studies as well as in situ hybridization for type IV collagen mRNA. RESULTS: Immuno-histochemistry demonstrated the positive staining of atrophic tubules to vimentin, platelet-derived growth factor-B chain (PDGF) and heat shock protein 47 (HSP47). Cells positive to one or more of PDGF receptor beta, alpha-smooth muscle actin (alpha-SMA), and HSP47 accumulated around atrophic tubules. Type IV collagen was also increased in the proximity of the atrophic tubules. These intimate relationships were more clearly demonstrated in 'mosaic tubules', which are composed of both intact and atrophic proximal tubular epithelial cells, and which had a mixed pattern of staining with vimentin, PDGF and HSP47. The interstitial cells positive to alpha-SMA or HSP47, or both, were in close contact with atrophic but not with intact epithelial cells. Type IV collagen was exclusively deposited between atrophic tubules and HSP47-positive interstitial cells. In situ hybridization of type IV collagen mRNA demonstrated predominant expression in atrophic tubular epithelial cells, but not in surrounding interstitial cells. CONCLUSIONS: These findings suggest that atrophic proximal tubular cells are active in the development of collagen deposition in the peritubular space, i.e. in this model type IV collagen in the interstitial fibrotic area may be produced mainly by atrophic proximal tubules.