Peritubular Capillary Endothelium Research Articles

398-P: Renal Proximal Tubular Metallothionein 3 Contributes to Diabetic Kidney Lesion

Metallothionein (MT) is a cysteine-rich protein with an antioxidant. MT3, one isoform of the four MTs, is upregulated in the renal proximal tubular cells in type 2 diabetic subjects. To investigate the role of human MT3, we used the mouse sglt2 promoter for targeting human MT3 gene to renal proximal tubular cells in transgenic mice (MT3TG). MT3TG showed nodular glomerulosclerosis without hyperglycemia. Electron microscopy presented thickened glomerular basement membranes, numerous endoplasmic reticulum in proximal tubules and cytoplasmic swelling of the endothelium of peritubular capillaries accompanied with abnormal capillary formation around the glomerulus, suggesting proximal tubular MT3 induces retrogradely glomerular hypertension. Affymetrix Human Gene 1.0 ST arrays identified 43 upregulated and 81 downregulated genes between control and MT3-knockdown human renal proximal tubular epithelial cells (HRPTECs, Lonza) under hypoxia, an early event in diabetic kidney. Among them, ceruloplasmin (CP) and cytochrome b reductase 1 (CYBRD), the crucial players in the cooper and iron metabolism, were downregulated. In fact, MT3TG presented cytoplasmic co-expression of MT3, CP and CYBRD1 in renal proximal tubules. Hypoxia induced a remarkable increase in MT3 in HRPTECs, and the HIF-1alpha siRNAs abolished that. Despite of no antioxidant response element in the human MT3 promoter, Nrf2 siRNA significantly decreased hypoxia-induced MT3 expression. Moreover, MT3 and Nrf2 siRNAs inhibited hypoxia-induced CP and CYBRD1, but not HIF-1 alpha siRNA. Together with the inhibitory effects of mitochondrial inhibitors, NOX4 inhibitors and antioxidant NAC on hypoxia-induced MT3 expression, hypoxia-induced oxidative stress might be involved in the inductions of CP and CYBRD1. Of note, empagliflozin decreased hypoxia-induced MT3, CP and CYBRD1. Our study suggests that MT3 might contributes to diabetic kidney lesion via CP and CYBRD1against hypoxia-induced oxidative stress. Disclosure Y.Takiyama: None. T.Takiyama: None. R.Bessho: None. H.Kitsunai: None. Y.Takiyama: Research Support; Boehringer Ingelheim Japan, Inc., Taisho Pharmaceutical Holdings Co., Ltd., Ono Pharmaceutical Co., Ltd., Abbott Japan Co., Ltd., Roche Diabetes Care, MSD Life Science Foundation, Japan Society for the Promotion of Science, Teijin Pharma Limited, Kyowa Kirin Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Eli Lilly Japan K.K.

MO056: Alteration of Glycocalyx on Endothelium of Peritubular Capillaries in CKD

Abstract BACKGROUND AND AIMS The glycocalyx is a carbohydrate-rich gel-like mesh, which covers the luminal surface of cells, including the endothelium. The glycocalyx is involved in many regulatory functions of the endothelium, including vascular permeability. In chronic kidney disease (CKD), peritubular capillaries undergo anatomical, structural and functional alterations such as rarefaction, increased tortuosity and increased permeability. Here, we hypothesized that the glycocalyx of peritubular capillaries might be affected in CKD and investigated morphological and ultrastructural pathological alterations of the glycocalyx in different murine CKD models and human kidney tissue. METHOD We stained the glycocalyx of peritubular capillaries in kidney tissue of murine and human CKD specimen using different fluorescently labeled plant-derived lectins. Next, we established the Lanthanum Dysprosium Glycosamino Glycan adhesion (LaDy GAGa) staining technique to visualize the ultrastructure of the glycocalyx using transmission electron microscopy and to perform quantitative analyses. Finally, we analyzed the expression and regulation of glycocalyx components in primary murine endothelial cells. RESULTS Fluorescence stainings using different lectins with high affinity to components of the renal glycocalyx revealed a reduced binding to the endothelium in CKD. We found a similar change in a human kidney tissue. The LaDy GAGa staining technique visualized the ultrastructure of the glycocalyx and enabled quantitive analyses. We found a significant reduction of the glycocalyx thickness and density in two different models of renal fibrosis and CKD, i.e. unilateral ureteral obstruction and ischemia–reperfusion injury. Additionally, mRNA expression of proteins involved in glycocalyx biology, synthesis and turnover, i.e. syndecan 1 and glypican 1, which are main components of the glycocalyx, and exostosin 2, involved in the synthesis of the glycocalyx, were significantly upregulated in endothelial cells isolated from murine CKD models. CONCLUSION Visualization of glycocalyx using specific ultrastructural analyses allows qualitative and quantitative analyses, revealing significant pathological alterations in the glycocalyx of peritubular capillaries in CKD.

Effects of low versus standard pressure pneumoperitoneum on renal syndecan-1 shedding and VEGF receptor-2 expression in living-donor nephrectomy: a randomized controlled study

BackgroundLaparoscopic nephrectomy is a preferred technique for living kidney donation. However, positive-pressure pneumoperitoneum may have an unfavorable effect on the remaining kidney and other distant organs due to inflamed vascular endothelium and renal tubular cell injury in response to increased systemic inflammation. Early detection of vascular endothelial and renal tubular response is needed to prevent further kidney injury due to increased intraabdominal pressure induced by pneumoperitoneum. Transperitoneal laparoscopic living donor nephrectomy represented a human model of mild increasing intraabdominal pressure. This study aimed to assess the effect of increased intraabdominal pressure on vascular endothelium and renal tubular cells by comparing the effects of low and standard pressure pneumoperitoneum on vascular endothelial growth factor receptor-2 (VEGFR-2) expression and the shedding of syndecan-1 as the early markers to a systemic inflammation.MethodsWe conducted a prospective randomized study on 44 patients undergoing laparoscopic donor nephrectomy. Subjects were assigned to standard (12 mmHg) or low pressure (8 mmHg) groups. Baseline, intraoperative, and postoperative plasma interleukin-6, syndecan-1, and sVEGFR-2 were quantified by ELISA. Syndecan-1 and VEGFR-2 expression were assessed immunohistochemically in renal cortex tissue. Renal tubule and peritubular capillary ultrastructures were examined using electron microscopy. Perioperative hemodynamic changes, end-tidal CO2, serum creatinine, blood urea nitrogen, and urinary KIM-1 were recorded.ResultsThe low pressure group showed lower intra- and postoperative heart rate, intraoperative plasma IL-6, sVEGFR-2 levels and plasma syndecan-1 than standard pressure group. Proximal tubule syndecan-1 expression was higher in the low pressure group. Proximal-distal tubules and peritubular capillary endothelium VEGFR-2 expression were lower in low pressure group. The low pressure group showed renal tubule and peritubular capillary ultrastructure with intact cell membranes, clear cell boundaries, and intact brush borders, while standard pressure group showed swollen nuclei, tenuous cell membrane, distant boundaries, vacuolizations, and detached brush borders.ConclusionThe low pressure pneumoperitoneum attenuated the inflammatory response and resulted in reduction of syndecan-1 shedding and VEGFR-2 expression as the renal tubular and vascular endothelial proinflammatory markers to injury due to a systemic inflammation in laparoscopic nephrectomy.Trial registrationClinicalTrials.gov NCT:03219398, prospectively registered on July 17th, 2017.

Induced expression of Toll-like receptor 9 in peritubular capillary endothelium correlates with the progression of tubulointerstitial lesions in autoimmune disease-prone mice.

Toll-like receptor (Tlr) 9 is capable of recognizing exogenous and/or endogenous nucleic acids and plays a crucial role in innate and adaptive immunity. Recently, we showed that Tlr9 is overexpressed in podocytes, a component of the blood-urine barrier (BUB), in glomeruli of autoimmune glomerulonephritis (AGN) model mice. This study investigated the activation of peritubular capillary (PTC) endothelial cells (ECs), a component of the BUB in the tubulointerstitium, through overexpressing Tlr9, and the subsequent development of tubulointerstitial lesions (TILs) in AGN model mice. Lupus-prone BXSB/MpJ-Yaa (Yaa) and BXSB/MpJ (BXSB) mice were used as an AGN model and control, respectively. In addition to histopathological and ultrastructural techniques, protein and mRNA levels were also evaluated. The relationship between Tlr9 and TIL indices was analyzed by statistical correlation analysis. Yaa mice developed TILs and showed strong Tlr9 mRNA expression in PTC ECs at 24 weeks (wks) of age. However, BXSB mice showed no TIL but faint expression of Tlr9 mRNA at 8 and 24 wks of age. Tlr9 protein localization on PTC was almost absent in BXSB mice at both ages but intense expression was found in Yaa mice only at 24 wks of age. Relative mRNA expression of Tlr9 and its putative downstream cytokines, including interleukin 1 beta ( Il1b), Il6, interferon gamma ( Ifng), and tumor necrosis factor alpha ( Tnf) was markedly increased in isolated tubulointerstitium from Yaa mice at 24 wks of age. Furthermore, electron microscopy examination revealed PTC injury and TIL in Yaa mice at 24 wks. The expression level of Tlr9 in the tubulointerstitium was correlated with inflammatory cells in TILs, injured PTC, Ilb and Tnf expression, and damaged tubules ( P < 0.05 and 0.01). Induced expression of Tlr9 in ECs correlates with PTC injury and the development of TILs in lupus-prone AGN model mice.

Association of Soluble TNFR-1 Concentrations with Long-Term Decline in Kidney Function: The Multi-Ethnic Study of Atherosclerosis.

TNF receptor-1 (TNFR-1), which plays a causative role in endothelial cell dysfunction and inflammation, is expressed on the cell surface in glomerular and peritubular capillary endothelium of the kidneys. Higher soluble TNF receptor-1 (sTNFR-1) concentrations are associated with kidney disease progression among persons with established diabetic kidney disease. However, no studies have assessed sTNFR-1's role in long-term kidney function changes in a multiethnic population without cardiovascular disease at baseline. We tested associations between baseline sTNFR-1 concentrations and 10-year decline in eGFR (incident ≥40% decline and annual proportional decline) among 2548 participants in the Multi-Ethnic Study of Atherosclerosis (MESA), a prospective cohort study. Serum creatinine concentrations were determined at enrollment and study years 3, 5, and 10. Mean age of participants was 61 years old, 53% were women, and mean baseline eGFR was 79 ml/min per 1.73 m2. Serum sTNFR-1 was inversely associated with baseline eGFR. Over median follow-up of 9.3 years, 110 participants developed ≥40% decline in eGFR; each SD higher concentration of sTNFR1 was associated with higher risk of 40% eGFR decline (adjusted hazard ratio, 1.43; 95% confidence interval [95% CI], 1.16 to 1.77; P<0.001). The highest sTNFR-1 tertile was associated with adjusted annualized decline in eGFR of 1.94% (95% CI, 1.79 to 2.09). Associations persisted across subgroups defined by demographics, hypertension, diabetes, and baseline CKD status. Elevated serum sTNFR-1 concentrations are associated with faster declines in eGFR over the course of a decade in a multiethnic population, independent of previously known risk factors for kidney disease progression.

Protective effect of Salvianolic acid A on ischaemia-reperfusion acute kidney injury in rats through protecting against peritubular capillary endothelium damages.

Renal ischaemia-reperfusion (I/R) injury is the most common cause of acute kidney injury (AKI). Peritubular capillary (PTC) endothelium damages are an important pathogenesis during I/R AKI. Salvianolic acid A (SAA) possesses various pharmacological activities. The study investigated whether SAA ameliorated I/R AKI through protecting against PTC endothelium damages. Male Sprague-Dawley rats were divided into 6 groups: control, sham, I/R, and I/R plus SAA (2.5, 5, 10mg/kg) groups. Rats were subjected to bilateral renal pedicle clamping for 60min, and killed at 24hr after reperfusion. Kidney injury, PTC endothelium damages and factors affecting PTC endothelium were evaluated. SAA significantly decreased blood urea nitrogen and serum creatinine levels, and reduced urine kidney injury molecule-1 concentration. Simultaneously, SAA alleviated histological damages, prevented PTC endothelium damages, preserved the density of PTC and improved renal hypoxia. Furthermore, SAA inhibited platelet activation, elevated Klotho protein expression and up-regulated vascular endothelial growth factor A expression. Overall, SAA has protective effects on AKI induced by I/R. Preventing PTC endothelium damages and preserving PTC integrity to improve the renal hypoxia may be the ways for SAA to ameliorate AKI. All these indicate that SAA is likely to be a promising agent for AKI.

Endothelial Marker Expressing Stromal Cells Play a Critical Role in Recovery Following Acute Kidney Injury

BackgroundAcute Kidney Injury (AKI) is characterized by an abrupt decrease in renal function that can lead to renal failure, thus contributing to high percentages of morbidity and mortality. The kidney contains a complex and high degree of vascularization making it susceptible to ischemic injury, particularly the peritubular capillaries. We have identified a subset of endothelial marker expressing stromal (EMES) cells that contribute to the peritubular capillary endothelium. Subsequently, we hypothesize that EMES cells are important contributors to kidney recovery after AKI.MethodsWe confirmed the importance of EMES following ischemia reperfusion injury (IRI) via lineage tracing, using a TdTomato reporter (permanently labeling all EMES cells) and interrogated the percentage of EMES cells that were present in the IRI and contralateral control kidneys. Furthermore, we generated mice with a conditional deletion of Flk1 (Vegfr2, essential for vascular development) in the Foxd1cre positive renal stroma (Flk1ST−/−), and evaluated the tissue after both blood flow dependent AKI, utilizing ischemia reperfusion injury (IRI), and blood flow independent or nephrotoxic AKI utilizing the chemotherapy agent cisplatin and focused on the recovery phase (7, or 28 days) post injury.ResultsWe determined in control mice following IRI that developmental stromal genes were re‐expressed suggesting that the stroma may be undergoing de‐differentiation and subsequently driving EMES proliferation. Furthermore, using lineage tracing we found that EMES preferentially increase during the repair phase (7 days) of IRI. To evaluate the role of EMES cells following AKI, we used Flk1ST−/− animals subjected to IRI, and found that mutants had less perfusion and an increase in hypoxia and increased expression of hypoxia inducible factor 1a (HIF1a) at 7 days. The hypoxic environment caused exasperated kidney damage in the mutant animals. Furthermore, when animals were allowed to recover for 28 days, there was significant fibrosis, and damage in the injured kidney compared to the contralateral control. When these animals were subjected to cisplatin injections we found that while perfusion of the kidneys appeared unaffected, HIF1a was similarly increased and the stromal genes were re‐expressed.ConclusionsTaken together we determined that for repair after AKI the renal stroma requires de‐differentiation and re‐expression of developmental markers prior to proliferation and re‐differentiation. This cellular reprogramming event also requires EMES cell proliferation, which play an important role in mediating vascular perfusion, reestablishing normal oxygen concentrations and regulating HIF signaling to modulate repair and recovery.Support or Funding InformationF32 DK111165‐01K01 DK096996

All-Trans Retinoic Acid Attenuates Hypoxia-Induced Injury in NRK52E Cells via Inhibiting NF-κB/VEGF and TGF-β2/VEGF Pathway

Background/Aims: Hypoxia has recently been proposed as one of the most important factors in progressive renal injury. Hypoxia-induced vascular endothelial growth factor (VEGF) expression may play a critical role in maintaining peritubular capillary endothelium in renal disease. This study was designed to investigate the effect and underlying mechanism of all-trans retinoic acid (ATRA) on hypoxia-induced injury in NRK52E cells. Methods: For mimicking hypoxia, cells were treated with 100 µM of cobalt chloride (CoCl2). The cell viability, expression of VEGF, p65, transforming growth factor-β2 (TGF-β2) and serine carboxypeptidase 1 (Scpep1), and nuclear factor of kappaB (NF-κB) activities after ATRA treatment were determined by MTT, western blot and electrophoretic mobility shift assay. Co-immunoprecipitation analysis was performed to demonstrate whether Scpep1 interacted with TGF-β2. Results: It was found that CoCl2 triggered hypoxia injury and significantly reduced cell viability. ATRA pretreatment increased the cell survival rate. Under hypoxic conditions, the expression of VEGF, p65 and TGF-β2 increased. Addition of ATRA significantly attenuated the expression of VEGF, p65 and TGF-β2. There was a corresponding variation of NF-κB/DNA binding activities. In addition, ATRA stimulated Scpep1 expression under normoxic and hypoxia condition. Furthermore, TGF-β2 interacted with Scpep1. Conclusions: This study indicated that ATRA may attenuate hypoxia-induced injury in NRK52E cells via inhibiting NF-κB/VEGF and TGF-β2/VEGF pathway.

Failed Tubule Recovery, AKI-CKD Transition, and Kidney Disease Progression.

The transition of AKI to CKD has major clinical significance. As reviewed here, recent studies show that a subpopulation of dedifferentiated, proliferating tubules recovering from AKI undergo pathologic growth arrest, fail to redifferentiate, and become atrophic. These abnormal tubules exhibit persistent, unregulated, and progressively increasing profibrotic signaling along multiple pathways. Paracrine products derived therefrom perturb normal interactions between peritubular capillary endothelium and pericyte-like fibroblasts, leading to myofibroblast transformation, proliferation, and fibrosis as well as capillary disintegration and rarefaction. Although signals from injured endothelium and inflammatory/immune cells also contribute, tubule injury alone is sufficient to produce the interstitial pathology required for fibrosis. Localized hypoxia produced by microvascular pathology may also prevent tubule recovery. However, fibrosis is not intrinsically progressive, and microvascular pathology develops strictly around damaged tubules; thus, additional deterioration of kidney structure after the transition of AKI to CKD requires new acute injury or other mechanisms of progression. Indeed, experiments using an acute-on-chronic injury model suggest that additional loss of parenchyma caused by failed repair of AKI in kidneys with prior renal mass reduction triggers hemodynamically mediated processes that damage glomeruli to cause progression. Continued investigation of these pathologic mechanisms should reveal options for preventing renal disease progression after AKI.

The outcome of renal allograft C4d staining among indicated biopsies in Ramathibodi hospital

C4d is a footprint of complement activation and diffusely stained in endothelium of peritubular capillaries (PTC) of renal allograft significantly associated with antibody mediated rejection (AMR). Association with C4d staining and poor graft outcome has been reported but some show little effects. Kidney transplant patients with indicated kidney biopsies in Ramathibodi hospital (151 patients, 181 specimens) during 2010–2012 with follow up durations of 12–30 months were enrolled in this retrospective cohort study. Graft survival/outcome, demographic, clinical and histological data were recorded and correlated with PTC C4d staining and graft survival. PTC C4d deposition was detected in 38.12% of allograft biopsies. AMR was diagnosed in 47 specimens while 107 specimens show minimal histologic change. Univariate analysis shows that pathological factors associated with graft loss are peritubular capillaritis, interstitial fibrosis, tubular atrophy, transplant glomerulopathy, arteriolar hyalinosis and C4d staining. Multivariate analysis of survival analysis shows that C4d deposition associated with graft loss, HR 11.37 (p = 0.021, 95% CI 1.45–89.15). In patients without rejection, C4d deposition was still associated with worse prognosis (10.21 vs 0.62 events/1000 patient-month, p = 0.012). Our study shows C4d positivity in 38% of indicated renal allograft biopsy and its significant association with poor renal allograft function and graft loss.

Beyond C4d: the ultrastructural appearances of endothelium in ABO-incompatible renal allografts

ABO incompatibility is no longer a barrier in kidney transplantation. C4d is frequently positive in ABO-incompatible (iABO) biopsies without further signs of microcirculation injury. This phenomenon is assumed to represent graft accommodation. However, ultrastructural examination of glomerular and peritubular capillary endothelium might reveal subtle endothelial damage. We studied the ultrastructural appearance of the endothelium in 67 biopsies from 21 patients with iABO allografts and compared it with 20 patients (29 biopsies) with ABO-compatible (cABO) grafts with C4d positivity and 25 ABO-compatible control patients (25 biopsies) without serological or histological evidence of humoral rejection (C4d negative). Ten ultrastructural parameters indicative of chronic and acute glomerular and peritubular capillary damage in transmission electron microscopy (TEM) were semi-quantitatively graded and expressed in a sum score. Clinico-pathological data were compared as well as graft function at the time of biopsy and follow-up. Ultrastructural parameters did not significantly differ between iABO and controls. In contrast, C4d-positive cABO had the highest TEM sum score (P = 0.001 versus iABO, P = 0.002 versus controls). The sum score did not differ between C4d-positive and C4d-negative iABO but did differ between patients with and without anti-HLA donor-specific antibodies (DSA). Graft function in iABO at the time of biopsy and at follow-up was similar to controls. Our ultrastructural observations support the concept of endothelial accommodation in iABO renal transplants. C4d positivity in the ABO-incompatible situation does not indicate injurious activation of the complement cascade and does not seem to impact on the graft function, in contrast to C4d deposition in cABO with antibody-mediated rejection.

Immunohistochemical expressions of adropin and ınducible nitric oxide synthase in renal tissues of rats with streptozotocin-ınduced experimental diabetes

Diabetes is characterized by high blood glucose levels; it occurs in 30–35% of the population. Elevated glucose levels can damage a number of organs, including the kidneys. Several peptide hormones participate in maintaining glucose homeostasis including the recently discovered “adropin,” a 42 amino acid peptide hormone. Adropin also alters inducible nitric oxide synthase (iNOS) expression. Therefore, we studied how adropin and iNOS expression is altered in the renal tissues of streptozotocin (STZ) induced diabetic rats. Seven sham, seven control and seven Wistar albino male rats were fed standard rat pellets and water ad libitum for 10 weeks. The rats in the diabetic group were injected i.p. with a single dose of 60 mg/kg STZ dissolved in 0.1 M phosphate-citrate buffer, pH 4.5. After the 10-week experimental period, the rats in both groups were anesthetized and decapitated. Kidney tissues were excised and placed in 10% formaldehyde solution, taken through routine histological procedures, and embedded in paraffin. Sections 5–6 μm thick were stained immunohistochemically using the avidin-biotin complex (ABC) method. Adropin and iNOS immunoreactivity were co-localized in the glomeruli, peritubular interstitial cells and peritubular capillary endothelium of the cortex; the thin limb of the loop of Henle in the medulla; and medullary peritubular interstitial cells and endothelium of the peritubular capillaries in both the control and diabetic groups. The intensities of adropin and iNOS immunoreactivity increased with the severity of the diabetes. Intense adropin immunoreactivity was detected in both the smooth muscle and human small intestine Paneth cells that were used as positive controls. The elevated levels of adropin and iNOS in the kidney indicates that these substances are involved in the pathophysiology of diabetes; this constitutes a compensatory mechanism against the damage inflicted by the disease.

Endothelial Progenitors Exist within the Kidney and Lung Mesenchyme

The renal endothelium has been debated as arising from resident hemangioblast precursors that transdifferentiate from the nephrogenic mesenchyme (vasculogenesis) and/or from invading vessels (angiogenesis). While the Foxd1-positive renal cortical stroma has been shown to differentiate into cells that support the vasculature in the kidney (including vascular smooth muscle and pericytes) it has not been considered as a source of endothelial cell progenitors. In addition, it is unclear if Foxd1-positive mesenchymal cells in other organs such as the lung have the potential to form endothelium. This study examines the potential for Foxd1-positive cells of the kidney and lung to give rise to endothelial progenitors. We utilized immunofluorescence (IF) and fluorescence-activated cell sorting (FACS) to co-label Foxd1-expressing cells (including permanently lineage-tagged cells) with endothelial markers in embryonic and postnatal mice. We also cultured FACsorted Foxd1-positive cells, performed in vitro endothelial cell tubulogenesis assays and examined for endocytosis of acetylated low-density lipoprotein (Ac-LDL), a functional assay for endothelial cells. Immunofluorescence and FACS revealed that a subset of Foxd1-positive cells from kidney and lung co-expressed endothelial cell markers throughout embryogenesis. In vitro, cultured embryonic Foxd1-positive cells were able to differentiate into tubular networks that expressed endothelial cell markers and were able to endocytose Ac-LDL. IF and FACS in both the kidney and lung revealed that lineage-tagged Foxd1-positive cells gave rise to a significant portion of the endothelium in postnatal mice. In the kidney, the stromal-derived cells gave rise to a portion of the peritubular capillary endothelium, but not of the glomerular or large vessel endothelium. These findings reveal the heterogeneity of endothelial cell lineages; moreover, Foxd1-positive mesenchymal cells of the developing kidney and lung are a source of endothelial progenitors that are likely critical to patterning the vasculature.

Endothelialitis without Tubulointerstitial Infiltrates in Renal Transplant Biopsies: Histological Findings, Clinical and Prognostic Relavance

Introduction: In order to avoid unnecessary therapy it is currently debated, whether acute cellular rejection with Banff components v≥1, i0, t0 (v_only) has the same therapeutic and prognostic implications as acute cellular rejections with Banff components v≥1, i≥1, t≥1 (v_plus). We examined this question retrospectively in renal transplant biopsies from a single center. Methods: All 23 renal transplant biopsies (from 23 patients) from our biopsy archive with v_only were retrospectively compared to 23 biopsies from 23 patients with v_plus. All patients, v_only and v_plus, received therapy for acute cellular rejection. They were then followed for 135 weeks ±106 (v_only) or 201 weeks ± 151 (v_plus). Results: No significant difference was found between v_only and v_plus regarding donor sex, donor age, immunosuppressive regimen, recipient age, time between transplantation and biopsy, number of glomeruli in the biopsy, Banff components v, g, mm, ah, cg, cv, ci, ptc, ratio of of preglomerular vessels with endothelialits to sum of preglomerular vessels, C4d-positivity of preglomerular endothelium, of peritubular capillary endothelium (Banff C4d), of glomerular endothelium, eGFR at biopsy, type of anti-rejection therapy, eGFR one week after initiation of anti-rejection therapy, eGFR slope per week between biopsy and end of follow-up.v_only had significantly more HLA-mismatches, a higher Banff ct component and and less cortical tubular interstitial edema. Conclusion: Our data show marginal histological differences between v_only and v_plus (with the exception of the defining Banff components i and t). We could not find a difference regarding response to anti-rejection therapy, transplant function or prognosis between v_plus and v_only. The higher number of HLA-mismatches in v_only might suggest, that this rare diagnosis could be associated with donor specific antibodies. We will examine this possible association further in our cohort.

All-trans Retinoic Acid Protects Renal Tubular Epithelial Cells Against Hypoxia Induced Injury In Vitro

BackgroundIt has been reported that the all-trans retinoic acid (atRA)-mediated protective effects in various cells are related to the inhibition of nuclear factor (NF)-κB activities. There exists some evidence that an increase in vascular endothelial growth factor (VEGF), which is expressed by proximal tubular epithelial cells and regulated by NFκB, may play a critical role in maintaining peritubular capillary endothelium in renal disease. By stimulating the production of VEGF, hypoxia is involved in tubulointerstitial fibrosis processes in various renal diseases. MethodsNRK52E cells survival rate was proportional to absorbance in dimethyl-thiazol-diphenyltetrazoliumbromide tests. Quantitative real-time polymerase chain reaction and Western blot were performed to assay the expression of VEGF, p65, and Scpep1. The activation of NFκB was determined by electrophoretic mobility shift assay. Co-immunoprecipitation analysis demonstrates that whether the Scpep1 and NFκB protein interacted. ResultsWe demonstrated that the hypoxia-mimicking agent CoCl2 triggered hypoxia injury of rat proximal tubular epithelial cells and significantly reduced cell viability. Addition of atRA increased the cell survival rate. Under CoCl2-mimicking hypoxic conditions, the expression of VEGF and p65 increased. The addition of atRA significantly attenuated the expression of VEGF and p65. There was a similar variation of NFκB/DNA binding activities. atRA not only activated distinct pathways to stimulate the expression of Scpep1, a retinoid-inducible gene, under normoxic conditions, but also acted as a CoCl2-mimicking hypoxia. ConclusionThe protective effects of atRA against hypoxia-induced injury might be involved in suppression of VEGF expression via stimulating Scpep1 distinct pathways and inhibiting the NFκB pathway.

Protective Effects of Exogenous Interleukin 18–Binding Protein in a Rat Model of Acute Renal Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) renal injury is considered the most common cause of acute kidney injury (AKI). The pathophysiology of I/R AKI involves a complex interplay among tubular epithelial cell injury, microcirculation dysfunction, and inflammation. Interleukin 18-binding protein (IL-18BP) is a natural inhibitor of IL-18 a cytokine that plays an important role in the pathogenesis of AKI. Therefore, we hypothesized that exogenous IL-18BP could protect against renal injuries after kidney I/R. Male Sprague-Dawley rats were divided into three groups: a sham operation group, I/R with vehicle injection, and I/R with IL-18BP injection. Rats underwent bilateral renal pedicle clamping, and IL-18BP or vehicle was administered just before reperfusion. Rats were killed 6, 24, and 72 h after reperfusion. After IL-18BP treatment, renal tubule epithelium showed reduced apoptosis and enhanced proliferation. For peritubular capillary (PTC) endothelium, apoptosis was inhibited, and there was an increase in PTC endothelium density. Macrophage infiltration was inhibited, and inflammatory cytokines were downregulated. Increased expression of vascular endothelial growth factor and decreased expression of thrombospondin 1 were also observed. Exogenous IL-18BP attenuated renal injury caused by I/R via inhibiting inflammation in the renal tissue and protecting tubular epithelium and PTC endothelium.

Enhancement of in vitro human tubulogenesis by endothelial cell-derived factors: implications for in vivo tubular regeneration after injury

Renal proximal tubular epithelium can regenerate after various insults. To examine whether the tubular repair process is regulated by surrounding peritubular capillaries, we established an in vitro human tubulogenesis model that mimics in vivo tubular regeneration after injury. In this model, HGF, a potent renotropic factor, dose dependently induced tubular structures in human renal proximal tubular epithelial cells cultured in gels. Consistent with regenerating tubular cells after injury, HGF-induced tubular structures expressed a developmental gene, Pax-2, and a mesenchymal marker, vimentin, and formed a lumen with aquaporin-1 expression. Electron microscopic analysis showed the presence of microvilli on the apical site of the lumen, suggesting that these structures are morphologically equivalent to renal tubules in vivo. When cocultured with human umbilical vein endothelial cells (HUVEC), HGF-induced tubular formation was significantly enhanced. This could not be reproduced by the addition of VEGF, basic FGF, or PDGF. Protein array revealed that HUVEC produced various matrix metalloproteinases (MMPs). The stimulatory effects of coculture with HUVEC or HUVEC-derived conditional medium were almost completely abolished by addition of the tissue inhibitor of metalloproteinase (TIMP)-1 or TIMP-2. These data suggest that endothelial cell-derived factors including MMPs play a critical role in tubulogenesis and imply a potential role of peritubular capillary endothelium as a source of factor(s) required for tubular recovery after injury.

Alteration of connexin expression is an early signal for chronic kidney disease

Chronic kidney disease is promoted by a variety of factors that induce chronic inflammation and fibrosis. Inflammation and excessive scaring have been recently associated with disruptions of the gap junction-mediated intercellular communication. Nevertheless, little is known about alterations of the expression of gap junction proteins such as connexin (Cx) 43 and 37 in chronic renal disease. In this study, we investigated the expression of these two Cxs in the hypertensive RenTg mice, the anti-glomerular basement membrane glomerulonephritis, and the unilateral ureteral obstruction models, all leading to the development of chronic kidney disease in mice. Expression of Cx43 was almost negligible in the renal cortex of control mice. In contrast, Cx43 was markedly increased in the endothelium of peritubular and glomerular capillaries of the 3-mo-old RenTg mice, in the glomeruli of mice suffering from glomerulonephritis, and in the tubules after obstructive nephropathy. The Cx43 expression pattern was paralleled closely by that of the adhesion markers such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 as well as the inflammatory biomarker monocyte chemoattractant protein-1. In contrast, Cx37 that was abundantly expressed in the renal cortex of healthy mice was markedly decreased in the three experimental models. Interestingly, Cx43+/- mice showed restricted expression of VCAM-1 after 2 wk of obstructive nephropathy. These findings suggest the importance of Cxs as markers of chronic renal disease and indicate that these proteins may participate in the inflammatory process during the development of this pathology.

Tranilast modulates fibrosis, epithelial-mesenchymal transition and peritubular capillary injury in unilateral ureteral obstruction rats

Tranilast is an anti-allergic compound suppressing transforming growth factor-beta 1 (TGF-β1) induced fibrosis. This study evaluated the efficacy of tranilast to attenuate renal fibrosis induced by unilateral ureteral obstruction (UUO) in rats in relation to epithelial-mesenchymal transition (EMT) and peritubular capillary injury. Rats were divided into four groups: UUO with vehicle or tranilast and sham operation with vehicle or tranilast. Tranilast (400 mg/kg/day) was administrated to rats for 7 and 14 days after UUO. Fibrosis and tubular injuries were attenuated in UUO kidneys with tranilast (Tr-UUO kidneys) compared with UUO kidneys with vehicle (V-UUO kidneys). Decreased E-cadherin and increased vimentin expression in the tubular epithelium and Snail expression in V-UUO kidneys were also attenuated in Tr-UUO kidneys in which heparan sulfate proteoglycan in the tubular basement membrane was preserved and matrix metalloproteinase-2 expression was attenuated. Increased TGF-β1 and phospho-Smad2 expression and increased numbers of myofibroblasts and macrophages in V-UUO kidneys were attenuated by tranilast. Decreased VE-cadherin expression and cytoplasmic swelling of the endothelium of peritubular capillaries that occurred in V-UUO kidneys was prevented by tranilast. Tranilast modulates fibrogenesis by reducing EMT, preventing disintegration of the tubular basement membrane, and reducing peritubular capillary injury in UUO kidneys.

Endothelial injury due to eNOS deficiency accelerates the progression of chronic renal disease in the mouse

The vascular endothelium expresses endothelial nitric oxide synthase (eNOS) that generates nitric oxide (NO) to help maintain vascular integrity due to its anti-inflammatory, antiproliferative, and antithrombogenic effects. Pharmacological blockade of NO production has been shown to exacerbate renal injury in chronic renal disease and induces endothelial cell loss. However, pharmacological inhibition of NO nonspecifically blocks other types of NOS and therefore does not define the specific role of eNOS in kidney disease. We hypothesized that a lack of endothelial eNOS can induce a loss of glomerular and peritubular capillary endothelium and exacerbate renal injury in progressive renal disease. We tested out this hypothesis using remnant kidney (RK) in eNOS knockout (eNOS KO) mice. Systolic blood pressure was significantly higher, and renal function was worse in RK-eNOS KO mice compared with those in RK-C57BL6 mice. eNOS deficiency resulted in more severe glomerulosclerosis, mesangiolysis, and tubular damage. Glomerular and tubular macrophage infiltration and collagen deposition were also greater in RK-eNOS KO mice. Renal injuries in the RK-eNOS KO mice were accompanied by a greater loss of endothelial cells that was shown to be due to both a decrease in endothelial cell proliferation and an increase in apoptosis. A lack of eNOS accelerates both glomerular and tubulointerstitial injury with a loss of glomerular capillaries and peritubular capillaries. Impaired endothelial function is likely a direct risk factor for renal disease.