Peritubular Capillary Endothelial Cells Research Articles

The Protective Role of Intermedin in Contrast-Induced Acute Kidney Injury: Enhancing Peritubular Capillary Endothelial Cell Adhesion and Integrity Through the cAMP/Rac1 Pathway.

Contrast-induced acute kidney injury (CIAKI) is a common complication with limited treatments. Intermedin (IMD), a peptide belonging to the calcitonin gene-related peptide family, promotes vasodilation and endothelial stability, but its role in mitigating CIAKI remains unexplored. This study investigates the protective effects of IMD in CIAKI, focusing on its mechanisms, particularly the cAMP/Rac1 signaling pathway. Human umbilical vein endothelial cells (HUVECs) were treated with iohexol to simulate kidney injury in vitro. The protective effects of IMD were assessed using CCK8 assay, flow cytometry, ELISA, and Western blotting. A CIAKI rat model was utilized to evaluate renal peritubular capillary endothelial cell injury and renal function through histopathology, immunohistochemistry, immunofluorescence, Western blotting, and transmission electron microscopy. In vitro, IMD significantly enhanced HUVEC viability and mitigated iohexol-induced toxicity by preserving intercellular adhesion junctions and activating the cAMP/Rac1 pathway, with Rac1 inhibition attenuating these protective effects. In vivo, CIAKI caused severe damage to peritubular capillary endothelial cell junctions, impairing renal function. IMD treatment markedly improved renal function, an effect negated by Rac1 inhibition. IMD protects against renal injury in CIAKI by activating the cAMP/Rac1 pathway, preserving peritubular capillary endothelial integrity and alleviating acute renal injury from contrast media. These findings suggest that IMD has therapeutic potential in CIAKI and highlight the cAMP/Rac1 pathway as a promising target for preventing contrast-induced acute kidney injury in at-risk patients, ultimately improving clinical outcomes.

Quantification of Globotriaosylceramide (GL3) in Peritubular Capillary (PTC) Endothelial Cells (ECs) in Kidney Biopsies from Patients with Fabry Disease (FD) Using Machine Learning

Quantification of Globotriaosylceramide (GL3) in Peritubular Capillary (PTC) Endothelial Cells (ECs) in Kidney Biopsies from Patients with Fabry Disease (FD) Using Machine Learning

Prioritization of Kidney Cell Types Highlights Myofibroblast Cells in Regulating Human Blood Pressure

IntroductionBlood pressure (BP) is a highly heritable trait with over two thousand underlying genomic loci identified to date. While the kidney plays a key role, little is known about specific cell types involved in the genetic regulation of BP. MethodsHere, we applied stratified linkage disequilibrium score (LDSC) regression to connect blood pressure GWAS results to specific cell types of the mature human kidney. We used the largest single-stage BP genome-wide analysis to date, including up to 1,028,980 adults of European ancestry, and single-cell transcriptomic data from 14 mature human kidneys, 41 years mean of age. ResultsOur analyses prioritized myofibroblasts and endothelial cells, among the total of 33 annotated cell type, as specifically involved in BP regulation (p-value < 0.05/33 i.e., 0.001515). Enrichment of heritability for systolic BP was observed in myofibroblast cells in mature human kidney cortex, and enrichment of heritability for diastolic BP was observed in descending vasa recta and peritubular capillary endothelial cells as well as stromal myofibroblast cells. The new finding of myofibroblast, the significant cell type for both BP traits, was consistent in eight replication efforts using seven sets of independent data, including in human fetal kidney, in East Asian ancestry, using mouse scRNA-seq data, and when using another prioritization method. ConclusionsOur findings provide a solid basis for follow up studies to further identify genes and mechanisms in myofibroblast cells that underlie the regulation of BP.

Neutrophil Extracellular Traps Aggravate Contrast-Induced Acute Kidney Injury by Damaging Glomeruli and Peritubular Capillaries.

Contrast-induced acute kidney injury (CI-AKI) is considered to be the third leading cause of hospital-acquired kidney injury. Current studies mostly suggest that contrast agents mainly harm renal tubular epithelial cells, but we hypothesized that the development of CI-AKI should be the result of the interaction of renal vascular and tubular injury. First we constructed a CI-AKI mouse model and verified the success of the model by pathological injury and serum creatinine level. Immunohistochemistry, protein quantification and qRT-PCR were used to detect the location and level of expression of neutrophil extracellular traps (NETs) in the kidney. Then, we blocked the in vivo accumulation of NETs using GSK484 and DNase I and detected the expression of NETs and the damage of glomerular and peritubular capillaries. We first identified the presence of NETs in CI-AKI mice, and NETs were mainly accumulated in glomeruli and peritubular capillaries. The expression of NETs was positively correlated with the severity of CI-AKI kidney. After inhibition of NETs release or promotion of NETs degradation by drugs, renal vascular endothelial cell injury was reduced and renal pathological changes and creatinine levels were reversed in CI-AKI mice. In addition, inhibition of NETs reduced apoptosis and pyroptosis of renal cells and attenuated inflammation in vivo. These findings suggest that NETs are involved in the development of CI-AKI by damaging glomerular and peritubular capillary endothelial cells. This study will provide a new strategy for clinical prevention and treatment of CI-AKI.

Low-Dose Erythropoietin Amplifies Beneficial Effects of Angiotensin II Blockade on Glomerulosclerosis

Exogenous erythropoietin (EPO) is used to treat anemia in patients with chronic kidney disease (CKD). Concerns about the possible adverse effect of EPO on the progression of CKD have been raised owing to nonerythroid cell effects. We investigated the effects of low-dose EPO, independent of correcting anemia, on existing glomerulosclerosis. Adult mice underwent 5/6 nephrectomy and were randomized into the following 4 groups at week 8 after surgery: vehicle (VEH), losartan (angiotensin II type 1 receptor blocker [ARB]), darbepoetin-α (DA), or combination (DA+ARB). Four weeks later, mice were euthanized, followed by evaluation of renal structure and function. Glomerular endothelial cells and podocytes were cultured to evaluate the effects of DA on cell migration, apoptosis, and Akt signaling. ARB reduced blood pressure, albuminuria, and the level of serum creatinine and increased hematocrit compared with VEH, whereas low-dose DA only reduced the level of serum creatinine. Combination treatment showed a trend to increase hematocrit and survival compared with ARB alone. Combination treatment but not ARB alone significantly reduced the progression of glomerulosclerosis compared with VEH. Low-dose DA resulted in more preserved glomerular and peritubular capillary endothelial cells with increased p-Akt and even further endothelial cell preservation in combination with ARB. In cultured glomerular endothelial cells, angiotensin II induced more apoptosis, reduced migration, and decreased p-Flk1, a receptor for the proangiogenic vascular endothelial growth factor. DA counteracted these injuries and increased p-Akt, a key factor in angiogenesis and cell survival. DA also protected cultured podocytes against transforming growth factor β–induced apoptosis and synaptopodin loss. Low-dose EPO directly protects glomerular and peritubular endothelial cells via Akt phosphorylation. Therefore, treatment using a combination of low-dose EPO and ARB results in less progression of glomerulosclerosis in an experimental CKD model.

The vascular protective effect of matrix Gla protein during kidney injury.

Matrix Gla protein (MGP) is a small secreted protein and requires vitamin K dependent γ-carboxylation for its function. MGP has been identified as a local inhibitor of vascular calcification because MGP-deficient mice die due to severe arterial calcification and resulting arterial rupture. Clinical trials revealed that reduction in active MGP predicts poor prognosis in patients due to cardiovascular complications. However, recent studies showed that MGP controls angiogenesis during development. MGP-deficient mice demonstrated abnormal hypervascularization and arteriovenous malformations in kidneys and other organs. This abnormal angiogenesis is largely caused by excessive expression of vascular endothelial growth factor-A (VEGF-A) and VEGF receptor-2 (VEGFR2). However, only a few studies have investigated the roles of MGP in tissue injury. We observed mesangial cell proliferation and mild interstitial fibrosis in addition to increased capillaries in kidneys of MGP-null mice even without injury. We also created a mouse model with kidney injury and found that kidney damage greatly increases MGP expression in peritubular capillary endothelial cells and tubular epithelial cells. Finally, our study showed that impairment of MGP expression aggravates peritubular capillary rarefaction and accumulation of collagen-producing myofibroblasts following kidney injury. Peritubular capillary damage induces capillary loss as well as trans-differentiation of vascular pericytes into myofibroblasts. These results indicate that MGP has the vascular protective effect in the injured kidney. Clinical trials have already started to test the efficacy of MGP activation to repair vascular calcification in patients with chronic kidney diseases. In this "Hypothesis and Theory" article, we discuss possible mechanisms by which MGP protects against vascular damage during tissue injury based on our experimental results and previous results from other research groups.

Retinoic acid receptor responder1 promotes development of glomerular diseases via the Nuclear Factor-κB signaling pathway

Inflammatory pathways are activated in most glomerular diseases but molecular mechanisms driving them in kidney tissue are poorly known. We identified retinoic acid receptor responder 1 (Rarres1) as a highly podocyte-enriched protein in healthy kidneys. Studies in podocyte-specific knockout animals indicated that Rarres1 was not needed for the normal development or maintenance of the glomerulus filtration barrier and did not modulate the outcome of kidney disease in a model of glomerulonephritis. Interestingly, we detected an induction of Rarres1 expression in glomerular and peritubular capillary endothelial cells in IgA and diabetic kidney disease, as well as in ANCA-associated vasculitis. Analysis of publicly available RNA data sets showed that the induction of Rarres1 expression was a common molecular mechanism in chronic kidney diseases. A conditional knock-in mouse line, overexpressing Rarres1 specifically in endothelial cells, did not show any obvious kidney phenotype. However, the overexpression promoted the progression of kidney damage in a model of glomerulonephritis. In line with this, conditional knock-out mice, lacking Rarres1 in endothelial cells, were partially protected in the disease model. Mechanistically, Rarres1 promoted inflammation and fibrosis via transcription factor Nuclear Factor-κB signaling pathway by activating receptor tyrosine kinase Axl. Thus, induction of Rarres1 expression in endothelial cells is a prevalent molecular mechanism in human glomerulopathies and this seems to have a pathogenic role in driving inflammation and fibrosis via the Nuclear Factor-κB signaling pathway.

Percutaneous transluminal renal angioplasty attenuates poststenotic kidney mitochondrial damage in pigs with renal artery stenosis and metabolic syndrome.

Percutaneous transluminal renal angioplasty (PTRA) has been used to treat renovascular disease (RVD), a chronic condition characterized by renal ischemia and metabolic abnormalities. Mitochondrial injury has been implicated as a central pathogenic mechanism in RVD, but whether it can be reversed by PTRA remains uncertain. We hypothesized that PTRA attenuates mitochondrial damage, renal injury, and dysfunction in pigs with coexisting renal artery stenosis (RAS) and metabolic syndrome (MetS). Four groups of pigs (n = 6 each) were studied after 16 weeks of diet-induced MetS and RAS (MetS + RAS), MetS + RAS treated 4 weeks earlier with PTRA, and Lean and MetS Sham controls. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector computed tomography, and renal tubular mitochondrial structure and function and renal injury ex vivo. PTRA successfully restored renal artery patency, but mean arterial pressure remained unchanged. Stenotic kidney RBF and GFR, which fell in MetS + RAS compared to MetS, rose after PTRA. PTRA attenuated MetS + RAS-induced mitochondrial structural abnormalities in tubular cells and peritubular capillary endothelial cells, decreased mitochondrial H2 02 production, and increased renal cytochrome-c oxidase-IV activity and ATP production. PTRA also improved cortical microvascular and peritubular capillary density and ameliorated tubular injury and tubulointerstitial fibrosis in the poststenotic kidney. Importantly, renal mitochondrial damage correlated with poststenotic injury and dysfunction. Renal revascularization attenuated mitochondrial injury and improved renal hemodynamics and function in swine poststenotic kidneys. This study suggests a novel mechanism by which PTRA might be relatively effective in ameliorating mitochondrial damage and improving renal function in coexisting MetS and RAS.

Efficient Drug Screening and Nephrotoxicity Assessment on Co-culture Microfluidic Kidney Chip

The function and susceptibility of various drugs are tested with renal proximal tubular epithelial cells; yet, replicating the morphology and kidneys function using the currently available in vitro models remains difficult. To overcome this difficulty, in the study presented in this paper, a device and a three-layer microfluidic chip were developed, which provides a simulated environment for kidney organs. This device includes two parts: (1) microfluidic drug concentration gradient generator and (2) a flow-temperature controlled platform for culturing of kidney cells. In chip study, renal proximal tubular epithelial cells (RPTECs) and peritubular capillary endothelial cells (PCECs) were screened with the drugs to assess the drug-induced nephrotoxicity. Unlike cells cultured in petri dishes, cells cultured in the microfluidic device exhibited higher performance in terms of both cell growth and drug nephrotoxicity evaluation. It is worth mentioning that a significant decrease in cisplatin-induced nephrotoxicity was found because of the intervention of cimetidine in the microfluidic device. In conclusion, the different in the cell performance between the microfluidic device and the petri dishes demonstrates the physiological relevance of the nephrotoxicity screening technology along with the microfluidic device developed in this study. Furthermore, this technology can also facilitate the development of reliable kidney drugs and serve as a useful and efficient test-bed for further investigation of the drug nephrotoxicity evaluation.

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.

Mitoprotection preserves the renal vasculature in porcine metabolic syndrome.

What is the central question of this study? We hypothesized that chronic mitoprotection would decrease renal vascular remodelling and dysfunction in swine metabolic syndrome. What is the main finding and its importance? This study shows that experimental metabolic syndrome exerts renal microvascular and endothelial cell mitochondrial injury, which were attenuated by mitoprotection, underscoring the contribution of mitochondrial injury to the pathogenesis of metabolic syndrome-induced vascular damage. The metabolic syndrome (MetS) induces intrarenal microvascular disease, which may involve mitochondrial injury. The mitochondrial cardiolipin-targeting peptide elamipretide (ELAM) improves the microcirculation in post-stenotic kidneys, but its ability to attenuate MetS-induced renal vascular damage is unknown. We hypothesized that chronic treatment with ELAM would decrease renal vascular remodelling and function in swine MetS. Pigs were studied after 16weeks of diet-induced MetS, MetS treated for the last 4weeks with daily injections of ELAM (0.1mg kg-1 ), and lean control (Lean) animals (n=6 each). Single-kidney regional perfusion, blood flow and glomerular filtration rate were measured with multi-detector computed tomography (CT). Peritubular capillary (PTC) endothelial cell (EC) mitochondrial density and cardiolipin content were assessed in situ, as were PTC-EC apoptosis and oxidative stress. The spatial density of PTCs (Haematoxylin and Eosin staining) and renal microvessels (micro-CT), and renal artery endothelial function (organ bath) were characterized. Regional perfusion and serum creatinine were preserved in MetS pigs, but renal blood flow and glomerular filtration rate were higher compared with Lean. Mitochondrial density and cardiolipin content were diminished in MetS PTC-ECs, but improved in ELAM-treated pigs, as did PTC density. Elamipretide also attenuated PTC-EC oxidative stress and apoptosis. Furthermore, ELAM improved renal microvascular density, decreased microvascular remodelling and restored endothelial nitric oxide expression and endothelium-dependent relaxation of renal artery segments. In conclusion, MetS-induced mitochondrial alterations might contribute to renal PTC and microvascular loss and might impair renal artery endothelial function in pigs. Mitoprotection with ELAM preserved a hierarchy of renal vessels, underscoring its potential to ameliorate renal vascular injury in MetS.

Regardless of etiology, progressive renal disease causes ultrastructural and functional alterations of peritubular capillaries

Progressive renal diseases are associated with rarefaction of peritubular capillaries, but the ultrastructural and functional alterations of the microvasculature are not well described. To study this, we analyzed different time points during progressive kidney damage and fibrosis in 3 murine models of different disease etiologies. These models wereunilateral ureteral obstruction, unilateral ischemia-reperfusion injury, and Col4a3-deficient mice, we analyzed ultrastructural alterations in patient biopsy specimens. Compared with kidneys of healthy mice, we found a significant and progressive reduction of peritubular capillaries in all models analyzed. Ultrastructurally, compared with the kidneys of control mice, focal widening of the subendothelial space and higher numbers of endothelial vacuoles and caveolae were found in fibrotic kidneys. Quantitative analysis showed that peritubular capillary endothelial cells in fibrotic kidneys had significantly and progressively reduced numbers of fenestrations and increased thickness of the cell soma and lamina densa of thecapillary basement membrane. Similar ultrastructural changes were also observed in patient's kidney biopsy specimens. Compared with healthy murine kidneys, fibrotic kidneys had significantly increased extravasation of Evans blue dye in all 3 models. The extravasation could be visualized using 2-photon microscopy in real time in living animals and was mainly localized to capillary branching points. Finally, fibrotic kidneys in all models exhibited asignificantly greater degree of interstitial deposition offibrinogen. Thus, peritubular capillaries undergo significant ultrastructural and functional alterations during experimental progressive renal diseases, independent of theunderlying injury. Analyses of these alterations could provide read-outs for the evaluation of therapeutic approaches targeting the renal microvasculature.

Endothelial sirtuin 1 inactivation enhances capillary rarefaction and fibrosis following kidney injury through Notch activation

Peritubular capillary (PTC) rarefaction along with tissue fibrosis is a hallmark of chronic kidney disease (CKD). However, molecular mechanisms of PTC loss have been poorly understood. Previous studies have demonstrated that functional loss of endothelial sirtuin 1 (SIRT1) impairs angiogenesis during development and tissue damage. Here, we found that endothelial SIRT1 dysfunction causes activation of endothelial Notch1 signaling, which leads to PTC rarefaction and fibrosis following kidney injury. In mice lacking functional SIRT1 in the endothelium (Sirt1 mutant), kidney injury enhanced apoptosis and senescence of PTC endothelial cells with impaired endothelial proliferation and expanded myofibroblast population and collagen deposition. Compared to wild-type kidneys, Sirt1 mutant kidneys up-regulated expression of Delta-like 4 (DLL4, a potent Notch1 ligand), Hey1 and Hes1 (Notch target genes), and Notch intracellular domain-1 (NICD1, active form of Notch1) in microvascular endothelial cells (MVECs) post-injury. Sirt1 mutant primary kidney MVECs reduced motility and vascular assembly and enhanced senescence compared to wild-type kidney MVECs. This difference in the phenotype was negated with Notch inhibition. Concurrent stimulation of DLL4 and transforming growth factor (TGF)-β1 increased trans-differentiation of primary kidney pericytes into myofibroblast more than TGF-β1 treatment alone. Collectively, these results indicate that endothelial SIRT1 counteracts PTC rarefaction by repression of Notch1 signaling and antagonizes fibrosis via suppression of endothelial DLL4 expression.

Immune Monitoring of Trans-endothelial Transport by Kidney-Resident Macrophages

Small immune complexes cause type III hypersensitivity reactions that frequently result in tissue injury. The responsible mechanisms, however, remain unclear and differ depending on target organs. Here, we identify a kidney-specific anatomical and functional unit, formed by resident macrophages and peritubular capillary endothelial cells, which monitors the transport of proteins and particles ranging from 20 to 700kDa or 10 to 200nm into the kidney interstitium. Kidney-resident macrophages detect and scavenge circulating immune complexes "pumped" into the interstitium via trans-endothelial transport and trigger a FcγRIV-dependent inflammatory response and the recruitment of monocytes and neutrophils. In addition, FcγRIV and TLR pathways synergistically "super-activate" kidney macrophages when immune complexes contain a nucleic acid. These data identify a physiological function of tissue-resident kidney macrophages and a basic mechanism by which they initiate the inflammatory response to small immune complexes in the kidney.

A novel mechanism of bacterial toxin transfer within host blood cell-derived microvesicles.

Shiga toxin (Stx) is the main virulence factor of enterohemorrhagic Escherichia coli, which are non-invasive strains that can lead to hemolytic uremic syndrome (HUS), associated with renal failure and death. Although bacteremia does not occur, bacterial virulence factors gain access to the circulation and are thereafter presumed to cause target organ damage. Stx was previously shown to circulate bound to blood cells but the mechanism by which it would potentially transfer to target organ cells has not been elucidated. Here we show that blood cell-derived microvesicles, shed during HUS, contain Stx and are found within patient renal cortical cells. The finding was reproduced in mice infected with Stx-producing Escherichia coli exhibiting Stx-containing blood cell-derived microvesicles in the circulation that reached the kidney where they were transferred into glomerular and peritubular capillary endothelial cells and further through their basement membranes followed by podocytes and tubular epithelial cells, respectively. In vitro studies demonstrated that blood cell-derived microvesicles containing Stx undergo endocytosis in glomerular endothelial cells leading to cell death secondary to inhibited protein synthesis. This study demonstrates a novel virulence mechanism whereby bacterial toxin is transferred within host blood cell-derived microvesicles in which it may evade the host immune system.

Microparticles from Kidney-Derived Mesenchymal Stem Cells Act as Carriers of Proangiogenic Signals and Contribute to Recovery from Acute Kidney Injury

We recently demonstrated the use of in vitro expanded kidney-derived mesenchymal stem cells (KMSC) protected peritubular capillary endothelial cells in acute renal ischemia-reperfusion injury. Herein, we isolated and characterized microparticles (MPs) from KMSC. We investigated their in vitro biologic effects on human endothelial cells and in vivo renoprotective effects in acute ischemia-reperfusion renal injury. MPs were isolated from the supernatants of KMSC cultured in anoxic conditions in serum-deprived media for 24 hours. KMSC-derived MPs demonstrated the presence of several adhesion molecules normally expressed on KMSC membranes, such as CD29, CD44, CD73, α4, 5, and 6 integrins. Quantitative real time PCR confirmed the presence of 3 splicing variants of VEGF-A (120, 164, 188), bFGF and IGF-1 in isolated MPs. MPs labeled with PKH26 red fluorescence dye were incorporated by cultured human umbilical vein endothelial cells (HUVEC) via surface molecules such as CD44, CD29, and α4, 5, and 6 integrins. MP dose dependently improved in vitro HUVEC proliferation and promoted endothelial tube formation on growth factor reduced Matrigel. Moreover, apoptosis of human microvascular endothelial cell was inhibited by MPs. Administration of KMSC-derived MPs into mice with acute renal ischemia was followed by selective engraftment in ischemic kidneys and significant improvement in renal function. This was achieved by improving proliferation, of peritubular capillary endothelial cell and amelioration of peritubular microvascular rarefaction. Our results support the hypothesis that KMSC-derived MPs may act as a source of proangiogenic signals and confer renoprotective effects in ischemic kidneys.

Expression of adropin in rat brain, cerebellum, kidneys, heart, liver, and pancreas in streptozotocin-induced diabetes

We have investigated how diabetes affects the expression of adropin (ADR) in rat brain, cerebellum, kidneys, heart, liver, and pancreas tissues. The rats in the diabetic group were administered an intraperitoneal (i.p.) injection of a single dose of 60 mg/kg streptozotocin (STZ) dissolved in a 0.1 M phosphate-citrate buffer (pH 4.5). The rats were maintained in standard laboratory conditions in a temperature between 21 and 23 °C and a relative humidity of 70 %, under a 12-h light/dark cycle. The animals were fed a standard commercial pellet diet. After 10 weeks, the animals were sacrified. ADR concentrations in the serum and tissue supernatants were measured by ELISA, and immunohistochemical staining was used to follow the expression of the hormones in the brain, cerebellum, kidneys, heart, liver, and pancreas tissues. The quantities were then compared. Increased ADR immunoreaction was seen in the brain, cerebellum, kidneys, heart, liver, and pancreas in the diabetes-induced rats compared to control subjects. ADR was detected in the brain (vascular area, pia mater, neuroglial cell, and neurons), cerebellum (neuroglial cells, Purkinje cells, vascular areas, and granular layer), kidneys (glomerulus, peritubular interstitial cells, and peritubular capillary endothelial cells), heart (endocardium, myocardium, and epicardium), liver (sinusoidal cells), and pancreas (serous acini). Its concentrations (based on mg/wet weight tissues) in these tissues were measured by using ELISA showed that the levels of ADR were higher in the diabetic rats compared to the control rats. Tissue ADR levels based on mg/wet weight tissues were as follows: Pancreas > liver > kidney > heart > brain > cerebellar tissues. Evidence is presented that shows ADR is expressed in various tissues in the rats and its levels increased in STZ-induced diabetes; however, this effect on the pathophysiology of the disorder remains to be understood.

High-risk anaemic Jehovah's Witness patients should be managed in the intensive care unit.

Severely anaemic Jehovah’s Witness (JW) patients who refuse blood transfusion on religious grounds have high mortality and morbidity1,2. Carson et al. have shown that the odds of death increase 2.5 times for every 10 g/L postoperative haemoglobin (Hb) decrease below 70 g/L3. The latest study4 demonstrated that an unadjusted nadir Hb concentration is a poor predictor of mortality of anaemic JW patients (Figure 1). Early risk factors including age ≥45 years of age, weight ≥90 kg, hypertension, cardiac arrhythmia, angina, previous myocardial infarction, valvular heart disease, heart failure, being on haemodialysis, acute admission and Hb ≤80 g/L on admission to hospital are associated with mortality of anaemic JW patients5. It was shown that an Auckland Anaemia Mortality Risk Score (Auckland AMRS), which is a composite score of the number of early risk factors each anaemic JW patient had, was associated with mortality. JW patients with Auckland AMRS of 0 to 3 had 4% mortality, Auckland AMRS 4 to 5, 32%, Auckland AMRS 6 to 7, 50% and Auckland AMRS ≥8, 83%5. During their hospital stay JW patients can develop anaemia-related (late) mortality risk factors including shock, acute gastro-intestinal bleeding, pneumonia, nadir Hb concentration ≤70 g/L, septicaemia, worsened congestive heart failure and neurologic complications4. Among these late risk factors, shock was the strongest predictor of mortality followed by acute gastro-intestinal bleeding and pneumonia. Figure 1 ROC curve: Nadir haemoglobin concentration as a predictor of Jehovah’s Witness patients mortality. When weights of individual statistically significant anaemia-related risk factors of mortality were combined and a composite mortality risk score, the Hamilton Anaemia Mortality Risk Score (Hamilton AMRS), was calculated, it was shown that JW patients with Hamilton AMRS of 0 to 2 had 4% mortality, Hamilton AMRS of 3 to 4, 29%, Hamilton AMRS of 5, 40%, and Hamilton AMRS of ≥6, 67%. On admission to hospital the trauma patient described by Lorentzen et al.6 had an Auckland AMRS of 3 (age, acute admission and Hb ≤80 g/L on admission to hospital) and a Hamilton AMRS of 6 (shock, ischaemic bowel perforation and the nadir Hb concentration ≤70 g/L) that estimated the patient’s mortality risk exceeding 70%. The patient underwent an open bowel resection and was managed in an intensive care unit (ICU) with physiologic parameters monitoring, ventilatory support, fluid resuscitation and an administration of vasopressors. The patient’s infective complications were treated with broad spectrum intravenous antibiotics, collection drainage, and wounds debridement and washout. Also the patient was treated with intravenous iron, B12 supplementation and subcutaneous administration of erythropoetin (EPO) in the dose of 10,000 units every second day. JW patients accept EPO, which is an erythropoiesis stimulating agent, as an alternative to blood transfusion. EPO is a 165 amino-acid glycoprotein, which is mainly produced by renal peritubular capillary endothelial cells in response to hypoxia7. As a haematopoietic cytokine, EPO promotes proliferation, differentiation and survival of erythroid progenitor cells8. In addition, EPO exerts a potent protective effect against hypoxia through its anti-apoptotic action9. After binding to its receptor on the cell surface, EPO initiates a JAK2 signalling cascade leading to NF-kB- and STAT5-dependent transcription of anti-apoptotic genes, including Bcl-xL, Bcl-210. Furthermore, EPO exerts a potent vascular protection and induces neoangiogenesis11–13.

Peritubular capillary rarefaction: a new therapeutic target in chronic kidney disease

Chronic kidney disease (CKD) has reached worldwide epidemic proportions and desperately needs new therapies. Peritubular capillary (PTC) rarefaction, together with interstitial fibrosis and tubular atrophy, is one of the major hallmarks of CKD and predicts renal outcome in patients with CKD. PTC endothelial cells (ECs) undergo apoptosis during CKD, leading to capillary loss, tissue hypoxia, and oxidative stress. Although the mechanisms of PTC rarefaction are not well understood, the process of PTC rarefaction depends on multiple events that occur during CKD. These events, which lead to an antiangiogenic environment, include deprivation of EC survival factors, increased production of vascular growth inhibitors, malfunction of ECs, dysfunction of endothelial progenitor cells, and loss of EC integrity via pericyte detachment from the vasculature. In this review, we focus on major factors regulating angiogenesis and EC survival and describe the roles of these factors in PTC rarefaction during CKD and possible therapeutic applications.

Distinct sites of renal fibrosis in Crim1 mutant mice arise from multiple cellular origins

Crim1 is a transmembrane protein that regulates the bioavailability of growth factors such as VEGFA. Crim1(KST264)(/)(KST264) hypomorphic mice develop renal disease characterized by glomerular cysts and loss of endothelial integrity, progressing to peritubular and pericystic fibrosis. Peritubular capillary endothelial cells display morphological changes as well as detachment from the basement membrane. In this study, gene expression profiling of CD31(+) endothelial cells isolated from Crim1(KST264)(/)(KST264) kidneys showed up-regulation of transcripts associated with fibrosis (Col3a1, Loxl1), endothelial dysfunction (Abp1, Dcn, Lcn2), biomarkers of renal damage (Lcn2, Havcr1/Kim1) as well as evidence for a TGFβ1/TNF-associated inflammatory process. To determine whether the aberrant endothelium may in part contribute to the fibrogenic process, Tie2Cre-DsRed lineage tracing was undertaken in Crim1(KST264/KST264) mice. Approximately 31% of de novo αSMA(+) myofibroblasts detected within the tubulointerstitium were Tie2(+) DsRed(+) . However, 5.3% were F4/80(+) DsRed(+) , indicating a small population of myofibroblasts of monocytic rather than endothelial origin. In contrast, only 12% of myofibroblasts located around glomerular cysts were Tie2(+) DsRed(+) , with 7.7% being monocyte-derived (F4/80(+) DsRed(+) ). Collectively, this model supports the involvement of endothelial cells/monocytes in fibrosis within the tubulointerstitium, but also the heterogeneity of the fibrotic process even within distinct regions of the same kidney.