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.     

Autologous bone marrow-derived mesenchymal stem cells for interstitial fibrosis and tubular atrophy: a pilot study

BackgroundMesenchymal stem cells (MSCs)-based therapy has shown promising results for renal injury. In this study, the efficacy and safety of autologous bone marrow-derived mesenchymal stem cells (BM-MSCs) in treating nonspecific interstitial fibrosis and tubular atrophy (IFTA) were evaluated.MethodsFrom March 2011 to January 2013, 11 renal transplanted patients with IFTA were recruited. At baseline, patients were given one intra-arterial infusion of BM-MSCs; 7 days and 1 month later, another two intravenous infusions of cells were followed. Serum creatinine, creatinine clearance rate, and serum cystatin-C at baseline and 7 days, 1 month, 3 months, 6 months, and 12 months after the intra-arterial infusion of BM-MSCs were used to assess renal function. At baseline and 6 months, histological examination based on hematoxylin-eosin, Masson’s trichrome and periodic acid-Schiff staining and immunohistochemistry for transforming growth factor β1 (TGF-β1) and connective tissue growth factor (CTGF) was performed. Adverse events were recorded to evaluate the safety of BM-MSCs treatment.ResultsAt 12 months, the renal function of 6 patients (54.5%) was improved, 3 (27.3%) were stable and 2 (18.2%) were worsened. At 6 months, the mean IFTA scores of all participators were similar with the baseline (1.73 ± 0.41 vs.1.50 ± 0.0.77, p = 0.242); however, it was significantly decreased when only 6 patients with improved renal function were analyzed (1.67 ± 0.41 vs. 1.08 ± 0.20, p = 0.013). Besides, decreased expression of TGF-β1 and CTGF were also observed at 6 months. During 1 year follow-up period, only two minor complications including infection and allergy were observed.ConclusionOur results demonstrated that autologous BM-MSCs are safe and beneficial for IFTA patients. Abbreviations: MSCs: mesenchymal stem cells; BM-MSCs: marrow-derived mesenchymal stem cells; IFTA: interstitial fibrosis and tubular atrophy; CAN: chronic allograft nephropathy; CNIs: calcineurin inhibitors; Scr: serum creatinine; CCr: creatinine clearance rate; Cys-C: cystatin-C; TGF-β1: transforming growth factor β1; CTGF: connective tissue growth factor     

Distribution of infused umbilical cord mesenchymal stem cells in a rat model of renal interstitial fibrosis

Abstract

Aims: Stem cell transplantation for the treatment of kidney diseases is dependent on choice of transplant pathway. We evaluated the safety of human umbilical cord mesenchymal stem cells through peripheral infusion and their distribution in a rat model of renal interstitial fibrosis (RIF). Method: Cryopreserved umbilical cord mesenchymal stem cells were infused via tail vein injection into rats with unilateral ureteral obstruction and Sham-operated. Blood, kidney, heart, liver, spleen and lung were collected at 14, 21, and 28 days after infusion. Testing included microscopic observation of kidney morphological changes and immunohistochemical testing to identify and count the number of MAB1281 (labeled human cells) positive cells in the heart, liver, spleen, lungs, and kidneys of different treatment groups. Results: There was no significant difference in the Sham-operated group and Sham-operated?+?cell transplantation group at different time points. Human cells were identified mainly in the lungs, spleen, and kidney. The number of human umbilical cord mesenchymal stem cells in the kidney was greater in the unilateral ureteral obstruction?+?cell transplantation group, compared to the Sham-operated?+?cell transplantation group. human umbilical cord mesenchymal stem cells were mainly located in the interstitium of the left kidney. These results suggest that infused mesenchymal stem cells were primed to engraft a damaged kidney, especially damaged renal interstitium. Conclusions: Intravenous infusion of exogenous umbilical cord mesenchymal stem cells is feasible and safe. Infused mesenchymal stem cells can reach damaged kidney tissues with obstructive RIF after a vein graft.     

Kidney tissue elastography and interstitial fibrosis observed in kidney biopsy

IntroductionKidney interstitial fibrosis is an important risk factor for the progression of chronic kidney disease. Kidney elastography is a noninvasive imaging modality that might be used to assess tissue fibrosis. In this study, we aimed to investigate the relationship between tissue stiffness detected in kidney elastography and interstitial fibrosis observed in kidney biopsy.Materials and methodsPatients who were hospitalized in a tertiary care university hospital with a kidney biopsy indication were included in this study. In all patients, the transverse and sagittal elastography measurements were made using a sonoelastography device before the biopsy. The total histological score was calculated.ResultsFifty-seven native kidney patients with proteinuria were included in the study. Patients were divided into two groups according to the presence (n = 6) and absence of fibrosis (n = 51) as detected by kidney biopsy. A significant correlation was found between the presence of fibrosis detected by biopsy and elastography outcomes (p = .046, r = .192). A significant correlation was found between the urea and creatinine levels and transverse elastography measurements (p = .036, r = .240). No correlation was observed between the transverse elastography measurements and total histological score consisting of glomerular, vascular, and tubular scores (r = .006, p = .967)ConclusionThe findings of our study suggest a significant relationship between the elastography measurements and interstitial fibrosis. Because of the high negative predictive value (91%), we suggest that elastography should mainly be used as an exclusion test for the presence of fibrosis. We also believe that elastography may be useful to evaluate the fibrosis status in kidney diseases.     

Haploinsufficiency of Pkd2 is associated with increased tubular cell proliferation and interstitial fibrosis in two murine Pkd2 models.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited human kidney disease and is caused by germline mutations in PKD1 (85%) or PKD2 (15%). It has been estimated that around 1% of tubular cells give rise to cysts, and cell hyperproliferation has been noted to be a cardinal feature of cystic epithelium. Nevertheless, it is uncertain whether the increase in proliferative index observed is an early or late feature of the cystic ADPKD kidney. METHODS: Two Pkd2 mouse mutants (WS25 and WS183) have been recently generated as orthologous models of PKD2. To determine the effect of Pkd2 dosage on cell proliferation, cyst formation and renal fibrosis, we studied renal tissue from Pkd2(WS25/WS25) and Pkd2(+/-) mice by histological analysis. We also examined the proliferative index in archival nephrectomy tissue obtained from patients with ADPKD and normal controls. RESULTS: The proliferative index of non-cystic tubules in Pkd2 mutant mice as assessed by proliferating cell nuclear antigen and Ki67-positive nuclei was between 1-2%, values 5-10 times higher than control tissue. Similarly, the proliferative index of non-cystic tubules in human ADPKD kidneys was 40 times higher than corresponding controls. In Pkd2 mutant mice, significant correlations were found between the fibrosis score and the mean cyst area as well as with the proliferative index. Of significance, proliferating tubular cells were uniformly positive for polycystin-2 expression in Pkd2(+/-) kidney. CONCLUSION: These results suggest that an increase in cell proliferation is an early event preceding cyst formation and can result from haploinsufficiency at Pkd2. The possible pathogenic link between tubular cell proliferation, interstitial fibrosis and cyst formation is discussed.     

Sirolimus inhibits lymphangiogenesis in rat renal allografts,a novel mechanism to prevent chronic kidney allograft injury

Lymphangiogenesis occurs in renal allografts and it may be involved in the maintenance of the alloreactive immune response and thus participate in the development of chronic kidney allograft injury. Sirolimus (SRL) has been shown to inhibit lymphangiogenesis. The aim of this study was to describe lymphangiogenesis and its regulation during the development of chronic kidney allograft injury and to investigate the effect of SRL on allograft lymphangiogenesis and chronic kidney allograft injury. A rat renal transplantation model was used. Allografts treated with cyclosporine A or with SRL were analyzed in various time points. Syngenic transplantations were used as controls. Kidney function was followed with serum creatinine. Histology was analyzed by Chronic Allograft Damage Index (CADI). Immunohistochemistry was used to detect lymphatic vessels, VEGF‐C and VEGFR‐3. In cyclosporine‐treated allografts VEGF‐C/VEGFR‐3 pathway was strongly upregulated leading to extensive lymphangiogenesis 60 days after transplantation. Lymphangiogenesis correlated positively with the CADI score. Sirolimus efficiently inhibited lymphangiogenesis, improved graft function and attenuated the development of chronic kidney allograft injury when compared with cyclosporine. In conclusion, lymphangiogenesis is associated with chronic kidney allograft injury and SRL is a potent inhibitor of lymphangiogenesis in renal allografts. Inhibition of lymphatic proliferation could mediate the nephroprotective properties of SRL.     

Arterial stiffness and wave reflections in renal transplant recipients.

BACKGROUND: Arterial stiffness predicts cardiovascular disease (CVD) events and has been well documented in haemodialysis patients. Information in renal transplant recipients (RTR), however, remains limited despite their higher CVD risk compared to the general population. We aimed to assess arterial stiffening and wave reflections in RTR and healthy controls and to evaluate which factors could explain potential differences. METHODS: Carotid augmentation index (AI) and carotid-femoral pulse wave velocity (PWV) were measured in 200 RTR and 44 controls using applanation tonometry. The impact of traditional and non-traditional CVD risk factors was assessed using linear regression analysis. Glomerular filtration rate (GFR) was measured by (51)Cr-EDTA (RTR) and estimated using the abbreviated Modification of Diet in Renal Disease formula (RTR and controls). RESULTS: After correction for age, blood pressure and anthropometry, AI and PWV remained 7.4 +/- 3.6% (P = 0.04) and 0.7 +/- 0.3 m/s (P = 0.01) higher in RTR than controls, corresponding to a difference in vascular age of >10 years. In multivariate analysis, additional independent factors related to AI and PWV were GFR (-1.8% and -0.19 m/s per 10 ml/min) and C-reactive protein (3.2% and 0.21 m/s per logarithm increase). CONCLUSIONS: Increased arterial stiffness and wave reflections in RTR are attributable to incomplete restoration of GFR and the presence of subclinical inflammation.     

Evolution of allograft fibrosis and function in kidney transplant recipients: a retrospective analysis of stable patients under CNI and mTORi

Histological evaluations of renal allograft biopsies are essential for diagnosis, but still show a low predictive value for long‐term allograft function. One limitation relies on the fact that the analysis is usually based on a single biopsy sample, and therefore, no dynamic changes are considered. Using two distinct approaches, we evaluated the evolution of fibrosis and related markers in 36 stable kidney transplant patients under calcineurin inhibitor therapy with two indication biopsies each, prior and at least 6 months after substitution by mTORi (N = 18), or maintenance on CNI (N = 18). In the method comparison, both Banff chronicity score and the digitally assessed fibrosis were correlated with allograft function at biopsy (r = ?0.36 and r = ?0.72, P = 0.002 and P < 0.0001, respectively). However, only the progression of fibrosis digitally assessed was correlated with allograft function loss, not only within the time between biopsies (r = ?0.47, P = 0.004) but also in the 60‐month follow‐up (r = ?0.47, P = 0.006). In the group analysis, despite of a higher incidence of C4d positivity (P = 0.05), progression of fibrosis, TGF‐β1 expression, and allograft function decline were significantly lower after conversion to mTORi compared with maintenance on CNI (P = 0.05, P = 0.02 and P = 0.01, respectively). PDGF, VEGF, b‐FGF, and HIF1A expressions remained stable over time regardless of therapy.