Matrix degradation in renal disease

Overexpressed C-type natriuretic peptide serves as an early compensatory response to counteract extracellular matrix remodeling in unilateral ureteral obstruction rats

Although the mechanism underlying C-type natriuretic peptide (CNP) beneficial effects is not entirely understood, modulating the expression of matrix metalloproteinases (MMPs)/tissue inhibitors of metalloproteinases (TIMPs) may play an important role. The study presented herein was designed as a first demonstration of the regulative effects of CNP on MMPs/TIMPs expression in unilateral ureteral obstruction (UUO) rats. The continuous changes of CNP, MMP-2, MMP-9, TIMP-1, TIMP-2 and type IV collagen (Col-IV) expression were determined in the obstructed rat kidneys at 3 days, 1, 2, and 3 months post-UUO respectively. According to the real-time PCR analysis, CNP, MMP-2 and MMP-9 mRNA expression in the obstructed kidneys were significantly higher compared to every time corresponding SOR, and progressively decreased over time. In contrast, in the obstructed kidneys collected 2 and 3 months post-UUO, the higher TIMP-1 and TIMP-2 mRNA expression were observed in comparison to the corresponding SOR group. The above trends of CNP, MMP-2, MMP-9, TIMP-1, and TIMP-2 transcripts were confirmed by their protein expression based on immunohistochemistry and western blot, and finally contributed to the progressive elevated Col-IV expression in the obstructed kidneys throughout the entire study period. Overexpressed CNP may be an early compensatory response to counteract extracellular matrix remodeling in UUO rats.

Renal-protective effect of nicousamide on hypertensive nephropathy in spontaneously hypertensive rats

Previous studies have demonstrated that a novel coumarin-aspirin derivative, nicousamide, has a significant renal-protective effect on diabetic nephropathy. The present study aimed to investigate the beneficial effect of nicousamide on hypertensive nephropathy, as well as the underlying mechanisms in spontaneously hypertensive rats (SHRs). SHRs were treated orally with saline, nicousamide at 15, 30 and 45 mg/kg, and losartan (10 mg/kg) daily for 17 weeks, during which blood pressure (BP) was measured every four weeks. At the end of the 17-week treatment, blood and urine samples were collected for biochemical analysis and kidney tissues were obtained for histopathological and reverse transcription-polymerase chain reaction (RT-PCR) analyses. The concentration of angiotensin (Ang) II in plasma was also examined. Results showed that nicousamide effectively attenuated the progression of hypertensive nephropathy by decreasing urinary albumin excretion (UAE) and blood urea nitrogen (BUN). This could significantly decrease BP (less effectively compared to losartan) and the incidence of glomerulosclerosis and glomerular arteriosclerosis, adequately alleviating tubular impairment. Nicousamide markedly reduced the plasma Ang II level in SHRs and reduced mRNA expression of angiotensin-converting enzyme (ACE) and chymase in the kidneys of SHRs. Thus, nicousamide may retard the progression of hypertensive nephropathy. Although the underlying mechanisms have yet to be fully elucidated, this may involve blocking of the renin-Ang system.

Matrix metalloproteinase levels in the drained dialysate reflect the peritoneal solute transport rate: a multicentre study in Japan

BACKGROUND

Long-term peritoneal dialysis (PD) leads to peritoneal injury with high solute transport of the peritoneal membrane. At worst, peritoneal injury leads to encapsulating peritoneal sclerosis with an extremely high mortality rate. To perform PD safely and adequately, it is necessary to monitor peritoneal injury. The aim of this study was to investigate the potential of matrix metalloproteinases (MMPs) as new indicators of peritoneal injury.

METHODS

The subjects included 215 PD patients with end-stage renal disease at 20 centres in Japan. MMPs or tissue inhibitors of MMP (TIMPs) in the drained dialysate were quantified with enzyme-linked immunosorbent assay. The peritoneal solute transport rate was assessed to estimate peritoneal injury and PD efficiency by the peritoneal equilibration test (PET).

RESULTS

MMP-2, MMP-3 and TIMP-1 levels in the drained dialysate obtained by the PET were correlated with the D/P Cr ratios (ρ = 0.69, ρ = 0.52, ρ = 0.55, respectively) and the D/D0 glucose ratios (ρ = -0.60, ρ = -0.47, ρ = -0.48, respectively). The measured D/S ratios of MMP-2 and TIMP-1 were significantly higher than the expected D/S ratios when MMP-2 and TIMP-1 would have been transported from only the circulation. The measured D/S ratios of MMP-3 nearly corresponded to the expected ratios. MMP-1 and TIMP-2 in the drainage were undetected in most patients.

CONCLUSIONS

From these results, most MMP-2 in the drained dialysate may be produced from the peritoneum, and MMP-2 is expected to be a useful marker of peritoneal injury or change in peritoneal solute transport.

Localization of matrix metalloproteinases and their inhibitors in experimental progressive kidney scarring

The extracellular matrix (ECM) is in a continual state of turnover with homeostasis maintained by balancing synthesis and degradation rates. During progressive kidney scarring an imbalance occurs leading to ECM accumulation. Reduced matrix metalloproteinase (MMP) activity is believed to central to this imbalance. However, most of the data relating to MMPs and their natural inhibitors (tissue inhibitors of matrix metalloproteinase (TIMP)) is based on homogenate studies where in situ compartmentalization is lost and thus changes in MMP activity may be artificial. To address this we have developed a sensitive, high-resolution in situ zymography technique and applied it, along with immunohistochemistry, to the 5/6th subtotal nephrectomy model of kidney scarring. ECM proteolytic activity in kidney homogenates progressively declined post-SNx against both gelatin (-82%) and collagen I (-78%) substrates. In situ zymography revealed higher activity with both substrates within the cytoplasm of normal tubular cells compared to the SNx. In contrast, there was 96% greater activity in the SNx glomeruli than normal. Immunohistochemistry confirmed a predominantly intracellular tubular location of all MMPs and TIMPs. Tubules showed reduced MMP-3 and elevated TIMP-2, whereas MMP-1 increased significantly in the glomeruli, especially in the mesangial matrix. TIMP-1 showed a fourfold increase in the remnant kidney by Western blot analysis, but could not be localized. Lowered MMP activity in homogenates results from reduced intracellular activity in the tubules, indicating that reduced MMP activity may not play a direct role in the expansion of the tubular ECM in scarring. However, elevated MMP-1 activity in the glomeruli may play a significant role in initiating glomerular remodelling.

Fibroblast differentiation in wound healing and fibrosis

The contraction of granulation tissue from skin wounds was first described in the 1960s. Later it was discovered that during tissue repair, fibroblasts undergo a change in phenotype from their normal relatively quiescent state in which they are involved in slow turnover of the extracellular matrix, to a proliferative and contractile phenotype termed myofibroblasts. These cells show some of the phenotypic characteristics of smooth muscle cells and have been shown to contract in vitro. In the 1990s, a number of researchers in different fields showed that myofibroblasts are present during tissue repair or response to injury in a variety of other tissues, including the liver, kidney, and lung. During normal repair processes, the myofibroblastic cells are lost as repair resolves to form a scar. This cell loss is via apoptosis. In pathological fibroses, myofibroblasts persist in the tissue and are responsible for fibrosis via increased matrix synthesis and for contraction of the tissue. In many cases this expansion of the extracellular matrix impedes normal function of the organ. For this reason much interest has centered on the derivation of myofibroblasts and the factors that influence their differentiation, proliferation, extracellular matrix synthesis, and survival. Further understanding of how fibroblast differentiation and myofibroblast phenotype is controlled may provide valuable insights into future therapies that can control fibrosis and scarring.

Activation of matrix metalloproteinase-2 causes peritoneal injury during peritoneal dialysis in rats

BACKGROUND

Sclerosing peritonitis (SP) and encapsulating peritoneal sclerosis (EPS) are serious complications of continuous ambulatory peritoneal dialysis. Although we have shown previously that matrix metalloproteinase-2 (MMP-2) is increased in peritoneal injury leading to SP/EPS, most of the MMP-2 in the dialysate drained from the peritoneal cavity was the latent form that was lacking activity. In the present study, we investigated whether MMP-2 causes peritoneal injury.

METHODS

To create an animal model of peritoneal injury, we administered intraperitoneally chlorhexidine gluconate to rats. Dialysate drained from these rats was analysed by gelatin zymography and MMP-2 activity was analysed by an in situ film zymography method. In vitro myofibroblasts were cultured in collagen three-dimensional culture and then MMP-2 in conditioned medium from the culture was analysed by gelatin zymography.

RESULTS

Zymographic analysis revealed that latent form MMP-2 levels were high in the dialysate from peritoneal injury rats, whereas the active form was barely detectable. MMP-2 activity in the peritoneal tissue of the peritoneal injury rats was strongly detected by in situ film zymography. In vitro myofibroblasts were promoted to produce MMP-2 and to activate MMP-2 in collagen three-dimensional culture.

CONCLUSIONS

In the present model, most of the MMP-2 was in the latent form, but activation of MMP-2 was promoted in the peritoneum during peritoneal injury. Activated MMP-2 may be associated with the progression of peritoneal injury.

Ischemic acute renal failure: long-term histology of cell and matrix changes in the rat

BACKGROUND

The cellular infiltration and matrix accumulation accompanying acute renal ischemia and reperfusion have been frequently noted but poorly defined. The long-term consequences of ischemia may irreversibly damage the kidney.

METHODS

Female Sprague-Dawley rats (200 g) underwent unilateral nephrectomy. After five days, the left renal pedicle was occluded for 45 minutes. Animals were sacrificed at 0, 1, 2, 4, 8, 16, 32, 64, and 180 days postischemia (N = 6). Immunohistochemistry for monocytes/macrophages (Mo/Mphi, ED-1), myofibroblasts [alpha-smooth muscle actin (alpha-SMA)], collagen III and IV, matrix metalloproteinase-2 (MMP-2) and proliferating cell nuclear antigen (PCNA) and terminal dUTP nick end labeling (TUNEL) were performed.

RESULTS

Kidney weights of postischemic animals were increased at all time points (postischemic to controls, 1.47 +/- 0.21 to 0.94 +/- 0.12 g at day 8; 1.49 +/- 0.20 to 1.27 +/- 0.13 g at day 64; and 1.86 +/- 0.1 to 1. 24 +/- 0.2 g at day 180). Serum creatinine values increased to 0.42 +/- 0.10 mmol/L at day 2 but returned to control levels by day 8 (0. 05 mmol/L). Glomerular collagen IV was decreased from 2 to 16 days postischemia, which was accompanied by an increase in MMP-2. The fractional area of the interstitium was greatest at day 8 (19.55 +/- 0.91% compared with day 0 at 8.08 +/- 0.27%), with a second increase observed at day 180 (16.61 +/- 0.70%). Interstitial Mo/Mphi increased postischemia from days 2 through 8 (8.84 +/- 2.12 to 133. 32 +/- 14.04 per 0.91 mm2) and then decreased. Myofibroblasts proliferated locally (PCNA double labeling was demonstrated), and increased numbers were found from days 2 through 16 (maximal at day 8, 26.96 +/- 3.04%, compared with day 0, 0.88 +/- 0.11%). In the postischemic groups, collagen IV increased to day 8 (20.84 +/- 1. 30%), but then decreased to below control values at day 64 (2.22 +/- 0.15%) before returning to normal by day 180. Interstitial collagen III increased to 8 days (0.45 +/- 0.07% to 2.55 +/- 0.36%) and then decreased to control levels by day 32, but showed a marked increase to approximately 6% at days 64 and 180. Cellular proliferation (PCNA) was maximal at days 2 and 4 (affecting tubule cells and myofibroblasts but not macrophages). Apoptosis was maximal at day 8 (in both interstitial and tubule cells) in the postischemic groups.

CONCLUSION

Marked changes in the accumulation of Mo/Mphi, MF, and collagen IV were found in this model of ischemic acute renal failure. The reversibility of functional and structural changes is in marked contrast to that found in progressive disease. The increases observed for collagen III at 64 and 180 days postischemia suggest that in the long term, however, further chronic structural changes may be observed.

Localization of transforming growth factors beta1 and beta2 and epidermal growth factor in IgA nephropathy

OBJECTIVE

The localization of transforming growth factor (TGF)-beta1. TGF-beta2 and epidermal growth factor (EGF) was investigated in IgA nephropathy, and was compared with the severity of histological damage (including tubulointerstitial lesions).

MATERIALS AND METHODS

The enzyme antibody method was used to stain paraffin-embedded sections of renal tissue from 42 patients with IgA nephropathy (19 males and 23 females).

RESULTS

There was a significant correlation between glomerular positivity for TGF-beta1 and TGF-beta2 and the severity of histological damage. There was also a significant correlation between positivity for TGF-beta1 and TGF-beta2 in the tubular epithelium and tubulointerstitial lesions. In contrast, there was no relationship between glomerular positivity for EGF and histological damage, although there was a significant correlation between positivity for EGF in the tubular epithelium and tubulointerstitial lesions.

CONCLUSIONS

These findings suggest that TGF-beta1 and TGF-beta2 may be important in the progression of IgA nephropathy, and that the distribution of EGF may also be a useful marker for the progression of renal damage, including tubulointerstitial lesions.