Circulating levels of matrix metalloproteinases MMP-3 and MMP-2 in renal transplant recipients with chronic transplant nephropathy

Clinical value of serum MMP-3 in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is defined as the progressive deterioration of renal parenchyma and decline in renal unit function. In the early stages of CKD(G1 + G2), symptoms are usually not obvious and cannot be effectively recognized on the basis of available clinical markers. Progression to the middle and late stages of CKD results in severe kidney damage with multiple complications causing adverse outcomes, including death. Therefore, the early diagnosis and monitoring of CKD is critical. Matrix metalloproteinase-3 (MMP-3), an extracellular matrix-degrading enzyme, plays an important role in kidney diseases. However, the clinical significance of serum MMP-3 levels in CKD has rarely been reported.

METHODS

We quantified the serum MMP-3 levels of 237 patients with CKD and 96 healthy individuals by using a highly sensitive time-resolved fluorescence immunoassay and analyzed differences in MMP-3 levels among the stages of CKD and the correlations of these changes with clinical indicators.

RESULTS

The serum MMP-3 concentrations of patients with CKD (171.76 ± 165.22 ng/mL) were significantly higher than those of healthy controls (34.05 ± 22.93 ng/mL; P < 0.0001). In CKD, serum MMP-3 levels were significantly correlated with estimated glomerular filtration rate (eGFR) (r =  - 0.5804, P < 0.0001), serum creatinine (CREA) (r = 0.5823, P < 0.0001), blood urea nitrogen (BUN) (r = 0.6106, P < 0.0001), and protein-to-creatinine ratio (r = 0.4992, P < 0.0001). Randomized forest analysis finds CREA, BUN, and MMP-3 most significant influences on CKD disease severity. The critical value of MMP-3 concentration of 40.39 ng/mL combined with eGFR was effective in diagnosing positive patients in the early (G1 + G2) stage of CKD and showed a positivity rate of 73.45 %. Moreover, in the early stages of CKD, patients with CKD who had serum MMP-3 concentration > 100 ng/mL had more severe renal impairment and inflammation than those with CKD who have lower serum MMP-3 concentrations.

CONCLUSION

Elevated serum MMP-3 levels are correlated with decreased kidney function in CKD progression, and patients with concomitant inflammation may express high levels of serum MMP-3. Serum MMP-3 may assist eGFR in improving the diagnosis of patients with early CKD.

Updated Pathways in Cardiorenal Continuum after Kidney Transplantation

Cardiovascular disease (CVD) remains one of the leading causes for increased morbidity and mortality in chronic kidney disease (CKD). Kidney transplantation is the preferred treatment option for CKD G5. Improved perioperative and postoperative care, personalized immunosuppressive regimes, and refined matching procedures of kidney transplants improves cardiovascular health in the early posttransplant period. However, the long-term burden of CVD is considerable. Previously underrecognized, the role of the complement system alongside innate immunity, inflammaging, structural changes in the glomerular filtration barrier and early vascular ageing also seem to play an important role in the posttransplant management. This review provides up-to-date knowledge on these pathways that may influence the cardiovascular and renal continuum and identifies potential targets for future therapies. Arterial destiffening strategies and the applicability of sodium-glucose cotransporter 2 inhibitors and their role in cardiovascular health after kidney transplantation are also addressed.

MMP3 Is a Non-invasive Biomarker of Rejection in Skin-Bearing Vascularized Composite Allotransplantation: A Multicenter Validation Study

Background: There is unmet need for non-invasive immunomonitoring to improve diagnosis and treatment of acute rejection in vascularized composite allotransplantation (VCA). Circulating matrix metalloproteinase 3 (MMP3) was described as a candidate non-invasive biomarker to predict treatment response to acute rejection in clinical VCA. However, larger validation studies are yet to be reported to allow for more definitive conclusions.

Methods: We retrospectively measured MMP3 levels using ELISA in a total of 140 longitudinal serum samples from six internal and three external face transplant recipients, as well as three internal and seven external upper extremity transplant recipients. The control groups comprised serum samples from 36 kidney transplant recipients, 14 healthy controls, and 38 patients with autoimmune skin disease. A linear mixed model was used to study the effect of rejection state (pre-transplant, no-rejection, non-severe rejection (NSR), and severe rejection) on MMP3 levels.

Results: In VCA, MMP3 levels increased significantly (p < 0.001) between pre- and post-transplant no-rejection states. A further increase occurred during severe rejection (p < 0.001), while there was no difference in MMP3 levels between non-severe and no-rejection episodes. A threshold of 5-fold increase from pre-transplant levels could discriminate severe from NSR with 76% sensitivity and 81% specificity (AUC = 0.79, 95% CI = 0.65–0.92, p < 0.001). In kidney transplantation, the MMP3 levels were significantly (p < 0.001) elevated during antibody-mediated rejection but not during T-cell mediated rejection (TCMR) (p = 0.547). MMP3 levels in healthy controls and autoimmune skin disease patients were comparable with either pre-transplant or no-rejection/NSR episodes of VCA patients.

Conclusion: The results of this study suggest that serum MMP3 protein is a promising marker for stratifying patients according to severity of rejection, complementary to biopsy findings.

Matrix Metalloproteinases in Renal Diseases: A Critical Appraisal

Matrix metalloproteinases (MMPs) are endopeptidases within the metzincin protein family that not only cleave extracellular matrix (ECM) components, but also process the non-ECM molecules, including various growth factors and their binding proteins. MMPs participate in cell to ECM interactions, and MMPs are known to be involved in cell proliferation mechanisms and most probably apoptosis. These proteinases are grouped into six classes: collagenases, gelatinases, stromelysins, matrilysins, membrane type MMPs, and other MMPs. Various mechanisms regulate the activity of MMPs, inhibition by tissue inhibitors of metalloproteinases being the most important. In the kidney, intrinsic glomerular cells and tubular epithelial cells synthesize several MMPs. The measurement of circulating MMPs can provide valuable information in patients with kidney diseases. They play an important role in many renal diseases, both acute and chronic. This review attempts to summarize the current knowledge of MMPs in the kidney and discusses recent data from patient and animal studies with reference to specific diseases. A better understanding of the MMPs' role in renal remodeling may open the way to new interventions favoring deleterious renal changes in a number of kidney diseases.

Increased levels of circulating MMP3 correlate with severe rejection in face transplantation

Face transplantation is a viable treatment option for carefully selected patients with devastating injuries to the face. However, acute rejection episodes occur in more than 80% of recipients in the first postoperative year. Unfortunately, neither a correlation between histological grades of rejection and anti-rejection treatment nor systemic surrogate markers of rejection in face transplantation are established in clinical routine. Therefore, we utilized next generation aptamer-based SOMAscan proteomics platform for non-invasive rejection biomarker discovery. Longitudinal serum samples from face transplant recipients with long-term follow-up were included in this study. From the 1,310 proteins analyzed by SOMAscan, a 5-protein signature (MMP3, ACY1, IL1R2, SERPINA4, CPB2) was able to discriminate severe rejection from both no-rejection and nonsevere rejection samples. Technical validation on ELISA platform showed high correlation with the SOMAscan data for the MMP3 protein (r_s = 0.99). Additionally, MMP3 levels were significantly increased during severe rejection as compared to no-rejection (p = 0.0009) and nonsevere rejection (p = 0.0173) episodes. Pathway analyses revealed significant activation of the metallopeptidase activity during severe face transplant rejection. This pilot study demonstrates the feasibility of SOMAscan to identify non-invasive candidate biomarkers of rejection in face transplantation. Further validation in a larger independent patient cohort is needed.

Matrix Metalloproteinases in Kidney Disease: Role in Pathogenesis and Potential as a Therapeutic Target

Matrix metalloproteinases (MMPs) are large family of proteinases. In addition to a fundamental role in the remodeling of the extracellular matrix, they also cleave a number of cell surface proteins and are involved in multiple cellular processes. MMP activity is regulated via numerous mechanisms, including inhibition by endogenous tissue inhibitors of metalloproteinases (TIMPs). Similar to MMPs, a role for TIMPs has been established in multiple cell signaling pathways. Aberrant expression of MMPs and TIMPS in renal pathophysiology has long been recognized, and with the generation of specific knockout mice, the mechanistic role of several MMPs and TIMPs is becoming more understood and has revealed both pathogenic and protective roles. This chapter will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury and chronic kidney disease. In addition, we will summarize studies suggesting that MMPs and TIMPs may be biomarkers of renal dysfunction and represent novel therapeutic targets to attenuate kidney disease.

Renal Fibrosis mRNA Classifier: Validation in Experimental Lithium-Induced Interstitial Fibrosis in the Rat Kidney

Accurate diagnosis of fibrosis is of paramount clinical importance. A human fibrosis classifier based on metzincins and related genes (MARGS) was described previously. In this investigation, expression changes of MARGS genes were explored and evaluated to examine whether the MARGS-based algorithm has any diagnostic value in a rat model of lithium nephropathy. Male Wistar rats (n = 12) were divided into 2 groups (n = 6). One group was given a diet containing lithium (40 mmol/kg food for 7 days, followed by 60mmol/kg food for the rest of the experimental period), while a control group (n = 6) was fed a normal diet. After six months, animals were sacrificed and the renal cortex and medulla of both kidneys removed for analysis. Gene expression changes were analysed using 24 GeneChip^® Affymetrix Rat Exon 1.0 ST arrays. Statistically relevant genes (p-value<0.05, fold change>1.5, t-test) were further examined. Matrix metalloproteinase-2 (MMP2), CD44, and nephroblastoma overexpressed gene (NOV) were overexpressed in the medulla and cortex of lithium-fed rats compared to the control group. TGFβ2 was overrepresented in the cortex of lithium-fed animals 1.5-fold, and 1.3-fold in the medulla of the same animals. In Gene Set Enrichment Analysis (GSEA), both the medulla and cortex of lithium-fed animals showed an enrichment of the MARGS, TGFβ network, and extracellular matrix (ECM) gene sets, while the cortex expression signature was enriched in additional fibrosis-related-genes and the medulla was also enriched in immune response pathways. Importantly, the MARGS-based fibrosis classifier was able to classify all samples correctly. Immunohistochemistry and qPCR confirmed the up-regulation of NOV, CD44, and TGFβ2. The MARGS classifier represents a cross-organ and cross-species classifier of fibrotic conditions and may help to design a test to diagnose and to monitor fibrosis. The results also provide evidence for a common pathway in the pathogenesis of fibrosis.

Increased plasma matrix metalloproteinase-2 (MMP-2), tissue inhibitor of proteinase-1 (TIMP-1), TIMP-2, and urine MMP-2 concentrations correlate with proteinuria in renal transplant recipients

BACKGROUND

The most frequent cause of kidney allograft loss is chronic allograft injury, often with proteinuria as the clinical feature. Occurrence of proteinuria late after kidney transplantation is associated with worse graft function and patient survival.

AIM

The aim of the study was to assess plasma and urine matrix metalloproteinases (MMP-2 and MMP-9) and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) in proteinuric renal transplant recipients (RTRs). The factors were determined by enzyme-linked immunosorbent assay in 150 RTRs (51 women and 99 men), aged 49.2 ± 11.5 years, at mean 73.4 ± 41.2 months after kidney transplantation (range: 12 to 240 months).

RESULTS

Proteinuric RTRs compared with non-proteinuric RTRs had higher median plasma MMP-2 (P = .012), TIMP-1 (P = .0003), and TIMP-2 (P = .0021) concentrations, as well as higher urine MMP-2 (P < .0001) excretion. The presence of proteinuria had no impact on plasma MMP-9 and urine MMP-9, TIMP-1, and TIMP-2. Proteinuria and estimated daily proteinuria (uPr:uCr) correlated positively with plasma MMP-2 (rs = 0.226, P = .0054 and rs = 0.241, P = .003), TIMP-1 (rs = 0.305, P = .00015 and rs = 0.323, P = .000055), TIMP-2 (rs = 0.273, P = .0007 and rs = 0.269, P = .001) and urine MMP-2 (rs = 0.464, P < .0001 and rs = 0.487, P < .0001), respectively. Proteinuric RTRs had impaired graft function with higher median serum creatinine concentrations (1.91 [1.60-2.43] mg/dL versus 1.41 [1.20-1.65] mg/dL, P < .00001) and lower estimated glomerular filtration rate (36 [28-45] mL/min/1.73 m(2) versus 53 [43-61] mL/min/1.73 m(2), P < .00001) than RTRs without proteinuria.

CONCLUSIONS

Our research revealed that in RTRs, proteinuria was significantly associated with increased concentrations of enzymes involved in extracellular matrix (ECM) degradation: plasma MMP-2, TIMP-1, TIMP-2, and urine MMP-2. Findings strongly emphasize increased plasma TIMPs in proteinuric RTRs that inhibit degradation of ECM by MMPs and favor excessive deposition of ECM proteins.

Renal dysfunction and intragraft proMMP9 activity in renal transplant recipients with interstitial fibrosis and tubular atrophy

Chronic renal allograft injury is reflected by interstitial fibrosis and tubular atrophy (IF/TA) and by the accumulation of extracellular matrix (ECM). Metalloproteinases (MMPs) are renal physiologic regulators of ECM degradation. Changes in MMPs expression or activity may disturb ECM turnover leading to glomerular scarring and worsening renal function. Our goal was to investigate intragraft MMP2 and MMP9 activities and their correlation with renal dysfunction. Plasma MMP2 and MMP9 activities were analyzed as noninvasive markers of renal allograft deterioration. Transplanted patients were biopsied and histopathologically characterized as IF/TA+ or IF/TA-. Renal function was evaluated by serum creatinine, glomerular filtration rate (GFR) estimated by Modification of Diet in Renal Disease equation and urinary protein/creatinine ratio. Kidney and plasma MMP2 and MMP9 activities were analyzed by zymography. A significant renal dysfunction was observed in IF/TA+ patients. Intragraft proMMP9 showed a significant higher activity in IF/TA+ than in IF/TA- samples and was inversely correlated with the GFR. Intragraft proMMP2 activity tended to increase in IF/TA+ samples, although no statistic significance was reached. Circulating proMMP2 and proMMP9 activities did not show significant differences between groups. Our data provide evidence that correlates intragraft proMMP9 activity with the fibrotic changes and renal dysfunction observed in IF/TA.

Array-based methods for diagnosis and prevention of transplant rejection

DNA microarray is a microhybridization-based assay that is used to simultaneously study the expression of thousands of genes, thus providing a global view of gene expression in a tissue sample. This powerful technique has been adopted by many biomedical disciplines and will likely have a profound impact on the diagnosis, treatment and prognosis of human diseases. This review article presents an overview of the application of microarray technology to the field of solid-organ transplantation.

Distinct role of matrix metalloproteinase-3 in kidney injury molecule-1 shedding by kidney proximal tubular epithelial cells

Tubulointerstitial injury is a common pathway in progressive renal impairment and human proximal tubular epithelial cells (PTEC) play a crucial role in this process. Kidney injury molecule-1 (KIM-1) has received increasing attention due to its potential utility as the therapeutic target and biomarker for kidney injury. This study aims to explore the underlying mechanism regulating the release of KIM-1. Cultured primary human PTEC expressed and released KIM-1 from the apical surface through an ectodomain shedding process mediated by matrix metalloproteinase (MMP), independent of gene expression and protein synthesis. The constitutive KIM-1 shedding by PTEC was enhanced in a dose- and time-dependent manner by human serum albumin (HSA) or tumor necrosis factor-α (TNF-α), two important physiological stimuli found during kidney injury. Data from PCR array screening of MMPs gene expression in PTEC following activation by HSA or TNF-α, and from blocking experiments using either synthetic MMP inhibitors or MMP gene knockdown by siRNA, revealed that the constitutive and accelerated shedding of KIM-1 in cultured PTEC was mediated by MMP-3. Furthermore, the up-regulation of MMP-3 and KIM-1 release by PTEC was associated with generation of reactive oxygen species. In a mouse model of acute kidney injury induced by ischemia and reperfusion, increased expression of MMP-3 and KIM-1 as well as their co-localization were observed in kidney from ischemic but not in sham-operated mice. Taken together, these in vitro and in vivo evidences suggest that MMP-3 plays an inductive role in KIM-1 shedding by PTEC.

A key role for matrix metalloproteinases and neutral sphingomyelinase-2 in transplant vasculopathy triggered by anti-HLA antibody

BACKGROUND

Outcomes for organ transplantation are constantly improving because of advances in organ preservation, surgical techniques, immune clinical monitoring, and immunosuppressive treatment preventing acute transplant rejection. However, chronic rejection including transplant vasculopathy still limits long-term patient survival. Transplant vasculopathy is characterized by progressive neointimal hyperplasia leading to arterial stenosis and ischemic failure of the allograft. This work sought to decipher the manner in which the humoral immune response, mimicked by W6/32 anti-HLA antibody, contributes to transplant vasculopathy.

METHODS AND RESULTS

Studies were performed in vitro on cultured human smooth muscle cells, ex vivo on human arterial segments, and in vivo in a model consisting of human arterial segments grafted into severe combined immunodeficiency/beige mice injected weekly with anti-HLA antibodies. We report that anti-HLA antibodies are mitogenic for smooth muscle cells through a signaling mechanism implicating matrix metalloproteinases (MMPs) (membrane type 1 MMP and MMP2) and neutral sphingomyelinase-2. This mitogenic signaling and subsequent DNA synthesis are blocked in smooth muscle cells silenced for MMP2 or for neutral sphingomyelinase-2 by small interfering RNAs, in smooth muscle cells transfected with a vector coding for a dominant-negative form of membrane type 1 MMP, and after treatment by pharmacological inhibitors of MMPs (Ro28-2653) or neutral sphingomyelinase-2 (GW4869). In vivo, Ro28-2653 and GW4869 reduced the intimal thickening induced by anti-HLA antibodies in human mesenteric arteries grafted into severe combined immunodeficiency/beige mice.

CONCLUSIONS

These data highlight a crucial role for MMP2 and neutral sphingomyelinase-2 in vasculopathy triggered by a humoral immune response and open new perspectives for preventing transplant vasculopathy with the use of MMP and neutral sphingomyelinase inhibitors, in addition to conventional immunosuppression.

Deficient degradation of homotrimeric type I collagen, α1(I)3 glomerulopathy in oim mice

Col1a2-deficient (oim) mice synthesize homotrimeric type I collagen due to nonfunctional proα2(I) collagen chains. Our previous studies revealed a postnatal, progressive type I collagen glomerulopathy in this mouse model, but the mechanism of the sclerotic collagen accumulation within the renal mesangium remains unclear. The recent demonstration of the resistance of homotrimeric type I collagen to cleavage by matrix metalloproteinases (MMPs), led us to investigate the role of MMP-resistance in the glomerulosclerosis of Col1a2-deficient mice. We measured the pre- and post-translational expression of type I collagen and MMPs in glomeruli from heterozygous and homozygous animals. Both the heterotrimeric and homotrimeric isotypes of type I collagen were equally present in whole kidneys of heterozygous mice by immunohistochemistry and biochemical analysis, but the sclerotic glomerular collagen was at least 95-98% homotrimeric, suggesting homotrimeric type I collagen is the pathogenic isotype of type I collagen in glomerular disease. Although steady-state MMP and Col1a1 mRNA levels increased with the disease progression, we found these changes to be a secondary response to the deficient clearance of MMP-resistant homotrimers. Increased renal MMP expression was not sufficient to prevent homotrimeric type I collagen accumulation.

Evaluation of metalloprotease inhibitors on hypertension and diabetic nephropathy

This study examined the effects of two new selective metalloprotease (MMP) inhibitors, XL081 and XL784, on the development of renal injury in rat models of hypertension, Dahl salt-sensitive (Dahl S) and type 2 diabetic nephropathy (T2DN). Protein excretion rose from 20 to 120 mg/day in Dahl S rats fed a high-salt diet (8.0% NaCl) for 4 wk to induce hypertension. Chronic treatment with XL081 markedly reduced proteinuria and glomerulosclerosis, but it also attenuated the development of hypertension. To determine whether an MMP inhibitor could oppose the progression of renal damage in the absence of changes in blood pressure, Dahl S rats were fed a high-salt diet (4.0% NaCl) for 5 wks to induce renal injury and then were treated with the more potent and bioavailable MMP inhibitor XL784 either given alone or in combination with lisinopril and losartan. Treatment with XL784 or the ANG II blockers reduced proteinuria and glomerulosclerosis by ~30% and had no effect on blood pressure. Proteinuria fell from 150 to 30 mg/day in the rats receiving both XL784 and the ANG II blockers, and the degree of renal injury fell to levels seen in normotensive Dahl S rats maintained from birth on a low-salt diet. In other studies, albumin excretion rose from 125 to >200 mg/day over a 4-mo period in 12-mo-old uninephrectomized T2DN rats. In contrast, albumin excretion fell by >50% in T2DN rats treated with XL784, lisinopril, or combined therapy. XL784 reduced the degree of glomerulosclerosis in the T2DN rats to a greater extent than lisinopril, and combined therapy was more effective than either drug alone. These results indicate that chronic administration of a selective MMP inhibitor delays the progression, and may even reverse hypertension and diabetic nephropathy.

Human cytomegalovirus induces TGF-β1 activation in renal tubular epithelial cells after epithelial-to-mesenchymal transition

Human cytomegalovirus (HCMV) infection is associated epidemiologically with poor outcome of renal allografts due to mechanisms which remain largely undefined. Transforming growth factor-β1 (TGF-β1), a potent fibrogenic cytokine, is more abundant in rejecting renal allografts that are infected with either HCMV or rat CMV as compared to uninfected, rejecting grafts. TGF-β1 induces renal fibrosis via epithelial-to-mesenchymal transition (EMT) of renal epithelial cells, a process by which epithelial cells acquire mesenchymal characteristics and a migratory phenotype, and secrete molecules associated with extracellular matrix deposition and remodeling. We report that human renal tubular epithelial cells infected in vitro with HCMV and exposed to TGF-β1 underwent morphologic and transcriptional changes of EMT, similar to uninfected cells. HCMV infected cells after EMT also activated extracellular latent TGF-β1 via induction of MMP-2. Renal epithelial cells transiently transfected with only the HCMV IE1 or IE2 open reading frames and stimulated to undergo EMT also induced TGF-β1 activation associated with MMP-2 production, suggesting a role for these viral gene products in MMP-2 production. Consistent with the function of these immediate early gene products, the antiviral agents ganciclovir and foscarnet did not inhibit TGF-β1 production after EMT by HCMV infected cells. These results indicate that HCMV infected renal tubular epithelial cells can undergo EMT after exposure to TGF-β1, similar to uninfected renal epithelial cells, but that HCMV infection by inducing active TGF-β1 may potentiate renal fibrosis. Our findings provide in vitro evidence for a pathogenic mechanism that could explain the clinical association between HCMV infection, TGF-β1, and adverse renal allograft outcome.

Human cytomegalovirus (HCMV) is a common virus that establishes lifelong persistence in the host. Although asymptomatic in healthy people, HCMV can reactivate and cause disease in immunosuppressed patients, such as those undergoing kidney transplantation. HCMV infection is associated with inferior renal allograft survival compared to transplants without HCMV infection. HCMV infected allografts also contain higher levels of the fibrogenic cytokine, transforming growth factor-β1 (TGF-β1), compared to uninfected allografts. TGF-β1 is a potent inducer of renal fibrosis and causes epithelial-to-mesenchymal transition (EMT), whereby epithelial cells acquire characteristics of cells of mesenchymal origin and express molecules associated with fibrosis. Our work shows that renal epithelial cells infected in vitro with HCMV can undergo EMT, but that HCMV infected cells produce greater amounts of the fibrogenic molecule TGF-β1, compared to uninfected cells after EMT. We have shown that this effect is likely due to specific HCMV genes (IE1, IE2), and cannot be prevented by administration of antivirals such as ganciclovir or foscarnet. These data suggest that HCMV may contribute to adverse renal allograft outcome by exacerbating TGF-β1 induced renal fibrosis. Understanding such mechanisms will permit the development of treatments that could improve long-term renal allograft survival in HCMV infected patients.

Chronic humoral rejection of human kidney allografts is associated with MMP-2 accumulation in podocytes and its release in the urine

Chronic humoral rejection (CHR) is an important cause of late graft failures following kidney transplantation. Overall, the pathophysiology of CHR is poorly understood. Matrix metalloproteinase-2 (MMP-2), a type IV collagenase, has been implicated in chronic kidney disease and allograft rejection in previous studies. We examined the presence of MMP-2 in allograft biopsies and in the urine of kidney transplant recipients with CHR. MMP-2 staining was detected by immunohistochemistry in podocytes for all CHR patients but less frequently in patients with other renal complications. Urinary MMP-2 levels were also significantly higher in CHR patients (median 4942 pg/mL, N = 27) compared to non-CHR patients (median 598 pg/mL, N = 65; p < 0.001). Elevated urinary MMP-2 correlated with higher levels of proteinuria in both CHR and non-CHR patients. Longitudinal analysis indicated that increase in urine MMP-2 coincided with initial diagnosis of CHR as documented by the biopsies. Using an enzymatic assay, we demonstrated that MMP-2 was present in its active form in the urine of patients with CHR. Overall, our findings associate MMP-2 with glomerular injury as well as interstitial fibrosis and tubular atrophy observed in patients with CHR.

Circulating matrix metalloproteinase-2 is associated with cystatin C level, posttransplant duration, and diabetes mellitus in kidney transplant recipients

Studies have indicated that matrix metalloproteinase-2 (MMP-2) is vital for the patient's condition after renal transplantation. Although the allograft survival rate has been improved, the relationships between various clinical parameters in stable graft function and serum MMP-2 still need to be clarified. In this study, gelatin zymography and enzyme-linked immunosorbent assay were employed to measure MMP-2 level in the plasma of 152 kidney transplant recipients, 41 chronic kidney disease patients, and 50 healthy control subjects. The creatinine and the MMP-2 levels in the transplant recipients were significantly greater (P < 0.001) than those of control subjects. Univariate and stepwise regression analysis demonstrated the MMP-2 level was associated with cystatin C level (P < 0.001), creatinine level (P = 0.036), proteinuria (P = 0.043), posttransplant days (P = 0.025), and posttransplant diabetes mellitus (P = 0.03). We conclude that circulating MMP-2 is associated with cystatin C, posttransplant duration, and diabetes mellitus in kidney transplant recipients and suggest that MMP-2 may be critical for graft survival.

Enhanced allograft survival and modulation of T-cell alloreactivity induced by inhibition of MMP/ADAM enzymatic activity

Recent studies have shown significantly increased expression of matrix metalloproteinases (MMP) and disintegrin-type metalloproteinases (ADAM) during allograft rejection. In this regard, our previous studies have demonstrated contrasting roles for MMP-2 and MMP-9 during allograft rejection: MMP-2-deficiency enhanced allograft survival while MMP-9-deficiency decreased allograft survival. The aim of this study was to determine the effect of broad-spectrum MMP/ADAM inhibition on the pathogenesis of allograft rejection. Toward this, heterotopic BALB/c cardiac allografts were transplanted into C57BL/6 recipients treated with MMP/ADAM inhibitors, GM6001 or doxycycline. Systemic MMP/ADAM inhibition significantly enhanced allograft survival. Functioning allografts recovered from MMP/ADAM inhibitor-treated recipients showed lower cellular infiltration and tissue remodeling than rejected allografts recovered from control recipients. In addition, decreased chemotaxis of CD4+ and CD8+ T cells, B cells and macrophages was observed in vitro in the presence of MMP/ADAM inhibitors. Enhanced T-cell alloreactivity was also observed ex vivo in MMP/ADAM inhibitor-treated recipients and in vitro in the presence of MMP/ADAM inhibitors. These observations were associated with enhanced cytokine, chemokine and growth factor production. These results indicate that MMPs and ADAMs play a critical role in the pathogenesis of allograft rejection and may represent novel therapeutic targets for the treatment and/or prevention of this disease.

Role of matrix metalloproteinases in renal pathophysiologies

Matrix metalloproteinases (MMPs) are a large family of proteinases that remodel extracellular matrix (ECM) components and cleave a number of cell surface proteins. MMP activity is regulated via a number of mechanisms, including inhibition by tissue inhibitors of metalloproteinases (TIMPs). Originally thought to cleave only ECM proteins, MMP substrates are now known to include signaling molecules (growth factor receptors) and cell adhesion molecules. Recent data suggest a role for MMPs in a number of renal pathophysiologies, both acute and chronic. This review will focus on the expression and localization of MMPs and TIMPs in the kidney, as well as summarizing the current information linking these proteins to acute kidney injury, glomerulosclerosis/tubulointerstitial fibrosis, chronic allograft nephropathy, diabetic nephropathy, polycystic kidney disease, and renal cell carcinoma.

The aetiology and pathogenesis of chronic allograft nephropathy

Renal transplantation is the ultimate form of renal replacement therapy, and is the treatment of choice for many patients with end-stage renal failure. The advent of calcineurin inhibitor based immunosuppression resulted in the 1-year renal allograft failure rate dropping from around 50% twenty years ago to less than 10% in more recent times. Despite a massive improvement in renal allograft survival in the first year following transplantation 10-year graft survival can be as low as 50%. Chronic allograft nephropathy (CAN) is recognised as the main cause of renal allograft failure following the first year after transplantation. The diagnosis of CAN can only be made histologically. Typically biopsy specimens in grafts with CAN demonstrate an overall fibrotic appearance effecting the vascular endothelium, renal tubules, interstitium, and glomerulus. The risk factors for CAN are divided into alloimmune and alloimmune independent. Alloimmune dependent factors include acute cellular rejection, severity of rejection, subclinical rejection and HLA mismatch. Alloimmune independent factors such as delayed graft function, donor age, Cytomegalovirus infection, donor/recipient co-morbidity and of course calcineurin inhibitor toxicity are important in the development of CAN. The pathogenesis of CAN is complex, multifactorial, and unfortunately incompletely understood. There are a number of pivotal steps in the initiation and propagation of the fibrosis seen in biopsy specimens from kidneys with CAN. Endothelial activation in response to one or more of the aforementioned risk factors stimulates leukocyte activation and recruitment. Recruited leukocytes subsequently infiltrate through the endothelium and induce key effector cells to secrete excessive and abnormal extracellular matrix (ECM). Enhanced deposition of ECM is a histological hallmark of CAN. This paper aims to present a concise yet accurate and up-to-date review of the literature concerning the aetiological factors and pathological processes which are present in the generation of CAN.

Relationships between circulating matrix metalloproteinase-2 and -9 and renal function in patients with chronic kidney disease

BACKGROUND

It has been proven that extracellular matrix turnover is involved in the pathogenesis of various renal fibrosis diseases. Matrix metalloproteinase-2 and -9 (MMP-2 and -9) are the extracellular matrix degrading enzymes that are believed to play important roles in renal diseases. However, the relationship of circulating levels of MMP-2, -9 and serum creatinine in the patients of chronic kidney disease (CKD) has not yet been investigated.

METHODS

Gelatin zymography and ELISA were employed to measure MMP-2 and MMP-9 activities in the plasma samples of 60 CKD patients and 40 control subjects.

RESULTS

Serum creatinine concentrations and MMP-2 activities were significantly higher (p<0.001) while MMP-9 activity and creatinine clearance (CCr) were significantly lower (p<0.05 and p<0.001, respectively) in CKD patients, as compared with those of control subjects. In addition, serum creatinine concentrations correlated with MMP-2 activity (R=0.288, p<0.05) and inversely correlated with that of MMP-9 (R=0.344, p<0.01).

CONCLUSIONS

This study demonstrated a correlation between MMP-2, -9 and serum creatinine in CKD patients to suggest that MMP-2 and MMP-9 might contribute in the pathogenesis of CKD.

Differential regulation of metzincins in experimental chronic renal allograft rejection: Potential markers and novel therapeutic targets

Chronic renal allograft rejection is characterized by alterations in the extracellular matrix compartment and in the proliferation of various cell types. These features are controlled, in part by the metzincin superfamily of metallo-endopeptidases, including matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase (ADAM) and meprin. Therefore, we investigated the regulation of metzincins in the established Fisher to Lewis rat kidney transplant model. Studies were performed using frozen homogenates and paraffin sections of rat kidneys at day 0 (healthy controls) and during periods of chronic rejection at day +60 and day +100 following transplantation. The messenger RNA (mRNA) expression was examined by Affymetrix Rat Expression Array 230A GeneChip and by real-time Taqman polymerase chain reaction analyses. Protein expression was studied by zymography, Western blot analyses, and immunohistology. mRNA levels of MMPs (MMP-2/-11/-12/-14), of their inhibitors (tissue inhibitors of metalloproteinase (TIMP)-1/-2), ADAM-17 and transforming growth factor (TGF)-beta1 significantly increased during chronic renal allograft rejection. MMP-2 activity and immunohistological staining were augmented accordingly. The most important mRNA elevation was observed in the case of MMP-12. As expected, Western blot analyses also demonstrated increased production of MMP-12, MMP-14, and TIMP-2 (in the latter two cases as individual proteins and as complexes). In contrast, mRNA levels of MMP-9/-24 and meprin alpha/beta had decreased. Accordingly, MMP-9 protein levels and meprin alpha/beta synthesis and activity were downregulated significantly. Members of metzincin families (MMP, ADAM, and meprin) and of TIMPs are differentially regulated in chronic renal allograft rejection. Thus, an altered pattern of metzincins may represent novel diagnostic markers and possibly may provide novel targets for future therapeutic interventions.

Chlamydia Pneumoniae Infection: An Additional Factor for Chronic Allograft Rejection

INTRODUCTION

Chronic rejection (CHR) of organ allografts, one of the most significant problems in modern transplantation, is not fully understood. This study sought to evaluate the influence of selected parameters on late kidney transplant function.

PATIENTS AND METHOD

The studied group consisted of eighty-six patients who received allogeneic transplants between 1988 and 1999 for leukocyte Chlamydia pneumoniae-DNA, immunoglobulin (Ig)A/IgG anti-C pneumoniae, blood lipids, ischemic damage in the donor and during organ preservation, HLA mismatch, and acute rejection episodes.

RESULTS

Eighty-six patients were segregated as 26 patients (30%) with histologically proven chronic graft rejection (CHR[+]) and 59 patients (70%) without (CHR[-]). The presence of C pneumoniae-DNA in peripheral blood leukocytes was significantly more frequent in CHR(+) than CHR(-) group (46% vs 20%). Patients with leukocytes positive for C pneumoniae-DNA more frequently (50%) had CHR than patients negative for C pneumoniae-DNA (22%). CHR(+) patients showed significantly lower HDL levels (47 mg/dL vs 58 mg/dL) and higher triglyceride levels (193 mg/dL vs 148 mg/dL). To study the cumulative effect of differences between the CHR(+) and CHR(-) groups, we applied a multiple binary logistic regression analysis. An econometric model enabled us to calculate the probability of CHR for a given patient taking into account covariates chosen by means of stepwise selection: the presence of C pneumoniae-DNA in blood leukocytes, the use of continuous pulsatile perfusion in hypothermia, myocardial infarction occurrence, and triglyceride concentrations.

CONCLUSION

The presence of C pneumoniae-DNA in peripheral blood leukocytes increased the risk of CHR, which may be predicted by a multifactor analysis of chosen parameters.

Fibrosis and matrix metalloproteinases in rat renal allografts

The temporal activity and gene expression of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinase (TIMP) were investigated in a rat model of chronic allograft nephropathy. Gelatinolytic activity of MMP-2 and -9 were demonstrated by zymography, and MMP-2,-9 and TIMP-3 mRNA by in situ hybridization. The generation of fibrosis was determined as total collagen content/DNA. Significantly more latent and active MMP-2, as well as latent MMP-9, were seen in allografts than in autografts. Intense MMP-2 mRNA expression was demonstrated in the allografts during the first 20 days after transplantation, located mainly in the interstitium of the kidney. In addition, some tubular cells expressed MMP-2 mRNA. After day 20, MMP-2 gene expression was faint. MMP-9 mRNA expression in allografts was located mainly in the glomerulus. TIMP-3 mRNA expression was downregulated in allografts. MMP-2, MMP-9 and TIMP-3 seem to play a critical role in the development of fibrosis in the renal allograft.

Inhibition of Matrix Metalloproteinases During Chronic Allograft Nephropathy in Rats

BACKGROUND

Chronic allograft nephropathy (CAN) belongs to the major causes of long-term kidney allograft failure. One of the histologic hallmarks of CAN is interstitial fibrosis, influenced by matrix metalloproteinases (MMPs) that are controlling extracellular matrix (ECM) degradation. Whether MMPs affect the development and progression of CAN is not clear so far. To analyze the role of MMPs in CAN, we investigated the effects of an early and a late application of BAY 12-9566, an inhibitor of MMP-2, -3, and -9 on the development and progression of CAN in a rat kidney-transplantation model.

METHODS

Fisher kidneys were orthotopically transplanted into Lewis recipients that were treated with BAY 12-9566 (15 mg/kg per day) or vehicle either for the first 10 days after transplantation (early treatment) or from week 12 to week 20 after transplantation (late treatment). Proteinuria was analyzed every 4 weeks up to week 20 after transplantation when kidney grafts were removed for further analysis.

RESULTS

Early MMP-inhibition resulted in a significantly reduced 24-hour protein excretion that was paralleled by a lower grade of CAN after 20 weeks. However, late MMP inhibition starting at week 12 after transplantation resulted in significantly higher proteinuria and a higher grade of CAN as compared with controls. Furthermore, transforming growth factor-beta and platelet-derived growth factor-B chain mRNA levels were significantly increased in these animals.

CONCLUSIONS

Inhibition of MMPs early after transplantation reduced the development and progression of CAN but promoted CAN if initiated at later stages. Thus, MMPs are involved in the development and progression of CAN.

The use of extracellular matrix probes and extracellular matrix-related probes for assessing diagnosis and prognosis in renal diseases

PURPOSE OF REVIEW

Scarring in the kidney results from excessive local synthesis and exogenous accumulation of extracellular matrix components. Once chronic damage is present in the biopsy, therapeutic intervention for the renal patient encounters severe limitations. It is therefore essential to determine clinical outcome preferably at a time point before the development of overt scarring. Clinical parameters and morphologic alterations in the biopsy are currently used as tools for the diagnosis of the renal disease entity and for assessment of the patient's prognosis. Expression levels of extracellular matrix and matrix-related components may serve as additive and even superior prognostic indicators to conventional parameters. We will elaborate on studies supporting this concept.

RECENT FINDINGS

Several investigators have shown in experimental models for renal disease that extracellular matrix probes and related probes reflect disease progression and predict outcome. In this review, we will provide an update on the most recent studies of human renal biopsies showing that expression of extracellular matrix components, regulators of matrix degradation, and cytokines affecting matrix deposition may be employed for discrimination of diagnostic groups and predicting prognosis.

SUMMARY

Molecular techniques are expected to be used more and more for diagnostic and prognostic purposes in nephrological practice to supplement the histopathological analysis of the renal biopsy. Assessment of expression of matrix molecules, matrix-regulating cytokines, and metalloproteinases in renal kidney biopsies is helpful to distinguish patients who are at risk of developing progressive renal failure from patients who are likely to recover from renal tissue injury by natural remodeling mechanisms.

Different roles for matrix metalloproteinase-2 and matrix metalloproteinase-9 in the pathogenesis of cardiac allograft rejection

Recent studies have shown an increased expression of several matrix metalloproteinases (MMP) during cardiac, renal and pulmonary allograft rejection. To further define the roles of MMP-2 and MMP-9 in the pathogenesis of cardiac allograft rejection, BALB/c cardiac allografts were transplanted into MMP-2-deficient (-/-) and MMP-9-/- mice. Allografts rejected by wild-type mice revealed a significant increase in MMP-2 and MMP-9 expression. MMP-2-deficiency significantly prolonged allograft survival time. Functioning allografts harvested from MMP-2-/- mice showed lower cellular infiltration and fibrosis than rejected allografts harvested from MMP-2+/+ mice at the same time. In contrast, MMP-9-deficiency significantly decreased allograft survival time. Functioning allografts harvested from MMP-9+/+ mice showed lower cellular infiltration and fibrosis than rejected allografts harvested from MMP-9-/- mice at the same time. MMP-2-/- recipients showed decreased T-cell alloreactivity mediated by a defect in dendritic cell stimulatory and T-cell responsive capacities. In contrast, MMP-9-/- recipients showed increased T-cell alloreactivity mediated by a significant increased in dendritic cell stimulatory and T-cell responsive capacities. These results indicate that MMP2 and MMP-9 play significantly different roles in the process of cardiac allograft rejection.

Assessment of serum matrix metalloproteinases MMP-2 and MMP-9 after human liver transplantation: increased serum MMP-9 level in acute rejection

BACKGROUND

Alterations in synthesis and breakdown of extracellular matrix components play a role in acute rejection after orthotopic liver transplantation (OLT). Matrix metalloproteinases (MMPs) are capable of degrading basement membranes and are involved in the process of tissue remodelling in inflammation and liver fibrosis.

METHODS

We examined MMP-2 and MMP-9 in serum of 33 patients before and during 1 year after OLT, in 60 controls as well as in some specimens of cirrhotic liver and control liver tissue.

RESULTS

Serum MMP-2 levels before OLT were significantly higher compared with controls and decreased approximately 50% after OLT. Also, the MMP-2 content of cirrhotic liver specimens was significantly higher compared with normal liver. MMP-9 in serum and liver tissue of patients were similar to controls, but serum levels showed a peak at 1 week after OLT. At this time-point, total and active/inhibitor-complexed MMP-9 was significantly higher in patients with rejection (n=13) compared with those without rejection (n=20). The relative amount of MMP-9 in the active/inhibitor-complexed form did not differ between each group over time. Immunohistochemical staining at 1 week after OLT showed increased numbers of MMP-9-positive inflammatory cells in the portal triads of patients with rejection.

CONCLUSIONS

Patients with acute allograft rejection have elevated serum levels of MMP-9 1 week after OLT, which was most likely derived from inflammatory cells. An increased MMP-2 serum level and liver tissue content was found in patients with cirrhosis, which decreased after OLT. These observations indicate active involvement of MMP-2 and -9 in end-stage liver disease and OLT.

Extracellular matrix proteins, proteolytic enzymes, and TGF-beta1 in the renal arterial wall of chronically rejected renal allografts

Chronic rejection (CR) is the leading cause of long-term failure of transplanted kidneys. The vascular hallmark is intimal hyperplasia, accompanied by macrophage, foam cell, and T-cell infiltration. Intimal thickening results from the migration and proliferation of smooth muscle cells and increased deposits of extracellular matrix (ECM) proteins, due to release of growth factors and cytokines as well as altered ECM protein turnover. We assessed the content of fibronectin (FN) and transforming growth factor-beta1 (TGF-beta1) as well as the activities of collagenase and cathepsin B and L in renal artery walls of chronically rejected human renal allografts. We investigated renal artery samples from 8 patients with CR undergoing graftectomy, 12 patients undergoing nephrectomy, and 7 organ donors. The results were related to the DNA content of homogenates. Cathepsin B and L activities were significantly higher among those with compared with donors (P =.022). There was a trend toward higher collagenase activity in CR compared with donors and the nephrectomy group. TGF-beta1 was significantly enhanced in CR compared with donors (P =.010), and showed a trend toward higher concentrations in CR compared with the nephrectomy group. The trend was toward lower FN concentrations in CR compared with the nephrectomy group and toward higher concentrations compared with donors. Summarizing, renal CR is accompanied by enhanced proteinase activity, alterations of ECM proteins, and increased TGF-beta1 in the renal artery wall. We conclude that ECM turnover and cytokines play an important role in neointimal formation and CR pathogenesis.

Differential expression of MMP-2/MMP-9 and potential benefit of an MMP inhibitor in experimental acute kidney allograft rejection

Acute cellular allograft rejection is characterized by leukocyte invasion and tissue destruction, associated with qualitative and quantitative alterations in the extracellular matrix (ECM) compartment. Metabolism of ECM proteins is mainly regulated by matrix metalloproteinases (MMP), that are zinc depended endoproteinases. MMP, especially basement membrane degrading MMP-2 and MMP-9, also facilitate tissue invasion of leukocytes. In addition, MMP-2 exerts a direct pro-inflammatory effect upon glomerular mesangial cells. Therefore, the investigation of the role of MMP in transplant rejection may lead to novel approaches in the therapy of rejection processes. To our knowledge, this is the first study of acute allograft rejection, formally addressing expression and activity of MMP, including the effect of a MMP inhibiting agent. For our studies, we used the orthotopic kidney allograft model in the stringent Dark Agouti-to-Lewis rat strain combination. Animals were divided into four groups: group A, healthy untreated Lewis rats (n=3); group B, sham operated Lewis rats (n=3); group C, transplanted Lewis rats treated with vehicle solution only (n=12); group D, transplanted Lewis rats treated with MMP inhibitor BB-94 (n=12). Respective animals were treated once daily intraperitonealy with BB-94 (30 mg/kg) or vehicle solution only. Treatment lasted from the third preoperative day until the end of the experiment, the time of severe rejection at day +7. Acute kidney allograft rejection led to alterations in the expression and activity of MMP. Overall MMP activity slightly increased despite severe destruction of kidney histology. The MMP inhibitor BB-94 successfully inhibited MMP activity to a high extent. MMP expression did not show uniform findings, since acute rejection led to differential expression of MMP-2 and MMP-9. During the rejection process, MMP-9 showed a small but significant increase, whereas MMP-2 production decreased substantially. Interestingly, BB-94 was able to keep proteinuria at a low level in transplanted animals. In conclusion, MMP-especially MMP-9-appear to represent new mediators involved in acute kidney transplant rejection.