High Macrophage Densities in Native Kidney Biopsies Correlate With Renal Dysfunction and Promote ESRD.

Introduction: Macrophages and monocytes are main players in innate immunity. The relevance of mononuclear phagocyte infiltrates on clinical outcomes remains to be determined in native kidney diseases. Methods: Our cross-sectional study included 324 patients with diagnostic renal biopsies comprising 17 disease entities and normal renal tissues for comparison. All samples were stained for CD68+ macrophages. Selected groups were further subtyped for CD14+ monocytes and CD163+ alternatively activated macrophages. Using precise pixel-based digital measurements, we quantified cell densities as positively stained areas in renal cortex and medulla as well as whole renal tissue. Laboratory and clinical data of all cases at the time of biopsy and additional follow-up data in 158 cases were accessible. Results: Biopsies with renal disease consistently revealed higher CD68+-macrophage densities and CD163+-macrophage densities in cortex and medulla compared to controls. High macrophage densities correlated with impaired renal function at biopsy and at follow-up in all diseases and in diseases analyzed separately. High cortical CD68+-macrophage densities preceded shorter renal survival, defined as requirement of permanent dialysis. CD14+ monocyte densities showed no difference compared to controls and did not correlate with renal function. Conclusion: Precise quantification of macrophage densities in renal biopsies may contribute to risk stratification to identify patients with high risk for end-stage renal disease (ESRD) and might be a promising therapeutic target in renal disease.

Alport syndrome and autosomal dominant tubulointerstitial kidney disease frequently underlie end-stage renal disease of unknown origin-a single-center analysis.

BACKGROUND: The prevalence of end-stage renal disease of unknown etiology in adult patients is globally high and accounts for almost 20% of all dialysis patients. Recent studies have suggested that the percentage of adult patients with a causal genetic variant has been underestimated so far. Despite severe prognostic and therapeutic implications, awareness about prevalence and manifestations of genetic kidney diseases in adult renal patients is still limited. METHODS: We recruited 58 individuals from 39 families at our transplantation center, fulfilling at least one of the following criteria: (i) unclear etiology of kidney disease, (ii) clinically suspected genetic kidney disease and (iii) positive family history for nephropathies. The cohort consisted of patients waitlisted for kidney transplantation and patients in the follow-up after transplantation. Detailed documentation of family history and phenotype was obtained before initiating gene panel sequencing of 479 nephropathy-associated genes. RESULTS: With this study design, a molecular genetic diagnosis was established in one-third of all patients. Mutations in the collagen COL4A genes, and mutations in MUC1 and UMOD were the most frequent among all detected causal variants. Overall, rare genetic variants were detected in more than half of all cases. CONCLUSION: The combination of detailed phenotyping prior to next-generation sequencing diagnostics was highly efficient. Elucidating the underlying genetic causes in a cohort of adult renal patients has considerable clinical impact on medical management.

Renal transplantation after recovery from COVID-19 - a case report with implications for transplant programs in the face of the ongoing corona-pandemic.

BACKGROUND: The ongoing coronavirus pandemic has major impacts on both patients and healthcare systems worldwide, thus creating new realities. Patients on maintenance dialysis listed for renal transplantation are a vulnerable subgroup with many comorbidities and recurring contacts with the healthcare system. Due to the COVID-19 pandemic transplant numbers have dropped considerably, further increasing waiting times in this high-risk population. On the other hand, knowledge of the severity of SARS-CoV-2 infection in immunocompromised patients, development and persistence of neutralising antibodies in such patients is just emerging. It is unclear how best to address the dilemma of postponing the life-saving transplantation. CASE PRESENTATION: We present a case report of a successful kidney transplantation only 65 days after the recipient was hospitalized for treatment of COVID-19 pneumonia. In a follow up of 9 months, we observed no signs of recurrent disease and transplant function is excellent. Monitoring SARS-CoV-2 antibody response demonstrates stable IgG levels. CONCLUSION: This reassuring case provides guidance to transplant centers how to proceed with kidney transplantation safely during the pandemic. Careful consideration of risks and benefits of the organ offer, full recovery from COVID-19 symptoms and the presence of a positive SARS-CoV-2 IgG antibody test, qualifies for kidney transplantation.

Association of donor hypertension and recipient renal function in living donor kidney transplantation: A single-center retrospective study.

Transplant centers now accept living donors with well-controlled hypertension. Little is known whether hypertension in living donors affects recipient's kidney function. We aimed to examine potential differences in kidneys from hypertensive donors compared to normotensive donors with respect to renal function over 36 months and histologic findings at transplantation (T0) and 12 months after transplantation (T1). Retrospective single-center analysis of 174 living donor-recipient pairs (age > 18; transplantation date 1/2008-3/2016). Hypertension in donors was defined as being on antihypertensive medication. All biopsies were assessed by the same blinded, experienced renal pathologist. Biopsies were scored for glomerulosclerosis, IFTA, and arteriosclerosis. Regression models were used to examine the relationship of donor hypertension with renal function and histologic changes. Hypertensive donors were significantly older than normotensive donors. Chronic changes such as tubular atrophy and atherosclerosis were more evident in kidneys from hypertensive donors at T0 as well as T1. Donor hypertension was independently associated with histologic changes at T0 and T1 but not with renal function over the follow period. Despite more pronounced histologic changes in kidneys from hypertensive living donors, these grafts exhibited a similar functional outcome. However, they subsequently might be at a greater risk and warrant thorough follow-up care.

Mononuclear phagocytes orchestrate prolyl hydroxylase inhibition-mediated renoprotection in chronic tubulointerstitial nephritis.

Prolyl hydroxylase domain enzyme inhibitors (PHDIs) stabilize hypoxia-inducible factors (HIFs), and are protective in models of acute ischemic and inflammatory kidney disease. Whether PHDIs also confer protection in chronic inflammatory kidney disease models remains unknown. Here we investigated long-term effects of PHDI treatment in adenine-induced nephropathy as a model for chronic tubulointerstitial nephritis. After three weeks, renal dysfunction and tubulointerstitial damage, including proximal and distal tubular injury, tubular dilation and renal crystal deposition were significantly attenuated in PHDI-treated (the isoquinoline derivative ICA and Roxadustat) compared to vehicle-treated mice with adenine-induced nephropathy. Crystal-induced renal fibrosis was only partially diminished by treatment with ICA. Renoprotective effects of ICA treatment could not be attributed to changes in adenine metabolism or urinary excretion of the metabolite 2,8-dihydroxyadenine. ICA treatment reduced inflammatory infiltrates of F4/80+ mononuclear phagocytes in the kidneys and supported a regulatory, anti-inflammatory immune response. Furthermore, interstitial deposition of complement C1q was decreased in ICA-treated mice fed an adenine-enriched diet. Tubular cell-specific HIF-1α and myeloid cell-specific HIF-1α and HIF-2α expression were not required for the renoprotective effects of ICA. In contrast, depletion of mononuclear phagocytes with clodronate largely abolished the nephroprotective effects of PHD inhibition. Thus, our findings indicate novel and potent systemic anti-inflammatory properties of PHDIs that confer preservation of kidney function and structure in chronic tubulointerstitial inflammation and might counteract kidney disease progression.

Peritoneal dialysis catheter leakage following intermittent vacuum therapy.

Peripheral arterial disease and diabetic foot syndrome are common comorbidities in dialysis patients. These conditions are treated with intermittent vacuum therapy in order to increase angiogenesis and perfusion. Some devices encase the lower extremities up to the abdomen. Here we report the case of a patient who had performed peritoneal dialysis for 2 years without complications. Following postoperative intermittent vacuum therapy, he presented with extensive catheter leakage. Ultimately the patient had to be switched to haemodialysis and the catheter had to be removed. This case exemplifies that peritoneal dialysis patients have a substantial risk for noninfectious catheter-related complications using vacuum therapy.

HIF-1α promotes cyst progression in a mouse model of autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by mutations of the PKD1 gene and characterized by growth of bilateral renal cysts. Cyst growth is accompanied by regional hypoxia and induction of hypoxia-inducible factor (HIF)-1α in cyst-lining epithelial cells. To determine the relevance of HIF-1α for cyst growth in vivo we used an inducible kidney epithelium-specific knockout mouse to delete Pkd1 at postnatal day 20 or 35 to induce polycystic kidney disease of different severity and analyzed the effects of Hif-1α co-deletion and HIF-1α stabilization using a prolyl-hydroxylase inhibitor. HIF-1α expression was enhanced in kidneys with progressive cyst growth induced by early Pkd1 deletion, but unchanged in the milder phenotype induced by later Pkd1 deletion. Hif-1α co-deletion significantly attenuated cyst growth in the severe, but not in the mild, phenotype. Application of a prolyl-hydroxylase inhibitor resulted in severe aggravation of the mild phenotype with rapid loss of renal function. HIF-1α expression was associated with induction of genes that mediate calcium-activated chloride secretion. Thus, HIF-1α does not seem to play a role in early cyst formation, but accelerates cyst growth during progressive polycystic kidney disease. This novel mechanism of cyst growth may qualify as a therapeutic target.

Delayed graft function is associated with an increased rate of renal allograft rejection: A retrospective single center analysis.

INTRODUCTION: The association of delayed graft function (DGF) and biopsy proven acute rejection (BPAR) of renal allografts is controversial. Borderline rejections comprise a major portion of biopsy results but the significance of such histologic changes is debated. The present study explores the impact of DGF on BPAR with a special emphasis on discriminating the effects of borderline rejection. METHODS: Single center analysis of 417 deceased donor kidney recipients (age>18; transplantation date 1/2008-2/2015). Patients with primary non-function were excluded. DGF was defined as the need for dialysis within the first week after transplantation. Acute rejection was defined according to Banff criteria. Cox proportional hazards models were used to examine the relationship of DGF with BPAR within the first year. RESULTS: No graft loss was observed during the first year after transplantation. DGF significantly associated with BPAR in the first year, irrespective of whether borderline rejections were included (HR 1.71, 95%CI 1.16,2.53) or excluded (HR 1.79, 95%CI 1.13,2.84). CONCLUSION: DGF is significantly associated with rejection-with or without borderline changes-within the first year.

A randomized, phase 2 study of ASP0113, a DNA-based vaccine, for the prevention of CMV in CMV-seronegative kidney transplant recipients receiving a kidney from a CMV-seropositive donor.

Cytomegalovirus (CMV) is a latent infection in most infected individuals, but can be pathogenic in immunocompromised kidney transplant recipients. ASP0113 is a DNA-based vaccine for the prevention of CMV-related mortality and end-organ disease in transplant recipients. The efficacy, safety, and immunogenicity of ASP0113 was assessed in a phase 2, double-blind, placebo-controlled study in CMV-seronegative kidney transplant recipients receiving a kidney from a CMV-seropositive donor. Transplant recipients were randomized (1:1) to receive 5 doses of ASP0113 (5 mg; n = 75) or placebo (n = 74) on Days 30/60/90/120/180 posttransplant, and they received prophylactic valganciclovir/ganciclovir 10-100 days posttransplant. The primary endpoint was the proportion of transplant recipients with CMV viremia ≥1000 IU/mL from Day 100 through to 1 year after the first study vaccine injection. There was no statistically significant difference in the primary endpoint between the ASP0113 and placebo groups (odds ratio 0.79, 95% confidence interval 0.43-1.47; P = .307). There were similar numbers of transplant recipients with treatment-emergent adverse events between groups; however, more transplant recipients reported injection site pain in the ASP0113 group compared with placebo. ASP0113 did not demonstrate efficacy in the prevention of CMV viremia in this CMV-seronegative kidney transplant population, but demonstrated a safety profile similar to placebo. ClinicalTrials.gov registration number: NCT01974206.

Hypoxia-inducible protein 2 Hig2/Hilpda mediates neutral lipid accumulation in macrophages and contributes to atherosclerosis in apolipoprotein E-deficient mice.

Recently we identified hypoxia-inducible protein 2 (HIG2)/hypoxia-inducible lipid droplet-associated (HILPDA) as lipid droplet (LD) protein. Because HILPDA is highly expressed in atherosclerotic plaques, we examined its regulation and function in murine macrophages, compared it to the LD adipose differentiation-related protein (Adrp)/perilipin 2 (Plin2), and investigated its effects on atherogenesis in apolipoprotein E-deficient (ApoE-/-) mice. Tie2-Cre-driven Hilpda conditional knockout (cKO) did not affect viability, proliferation, and ATP levels in macrophages. Hilpda proved to be a target of hypoxia-inducible factor 1 (Hif-1) and peroxisome proliferator-activated receptors. In contrast, Adrp/Plin2 was not induced by Hif-1. Hilpda localized to the endoplasmic reticulum-LD interface, the site of LD formation. Hypoxic lipid accumulation and storage of oxidized LDL, cholesteryl esters and triglycerides were abolished in Hilpda cKO macrophages, independent of the glycolytic switch, fatty acid or lipoprotein uptake. Hilpda depletion reduced resistance against lipid overload and increased production of reactive oxygen species after reoxygenation. LPS-stimulated prostaglandin-E2 production was dysregulated in macrophages, demonstrating the substrate buffer and reservoir function of LDs for eicosanoid production. In ApoE-/- Hilpda cKO mice, total aortic plaque area, plaque macrophages and vascular Vegf expression were reduced. Thus, macrophage Hilpda is crucial to foam-cell formation and lipid deposition, and to controlled prostaglandin-E2 production. By these means Hilpda promotes lesion formation and progression of atherosclerosis.-Maier, A., Wu, H., Cordasic, N., Oefner, P., Dietel, B., Thiele, C., Weidemann, A., Eckardt, K.-U., Warnecke, C. Hypoxia-inducible protein 2 Hig2/Hilpda mediates neutral lipid accumulation in macrophages and contributes to atherosclerosis in apolipoprotein E-deficient mice.

Transcriptional repressor ZEB2 promotes terminal differentiation of CD8+ effector and memory T cell populations during infection.

ZEB2 is a multi-zinc-finger transcription factor known to play a significant role in early neurogenesis and in epithelial-mesenchymal transition-dependent tumor metastasis. Although the function of ZEB2 in T lymphocytes is unknown, activity of the closely related family member ZEB1 has been implicated in lymphocyte development. Here, we find that ZEB2 expression is up-regulated by activated T cells, specifically in the KLRG1(hi) effector CD8(+) T cell subset. Loss of ZEB2 expression results in a significant loss of antigen-specific CD8(+) T cells after primary and secondary infection with a severe impairment in the generation of the KLRG1(hi) effector memory cell population. We show that ZEB2, which can bind DNA at tandem, consensus E-box sites, regulates gene expression of several E-protein targets and may directly repress Il7r and Il2 in CD8(+) T cells responding to infection. Furthermore, we find that T-bet binds to highly conserved T-box sites in the Zeb2 gene and that T-bet and ZEB2 regulate similar gene expression programs in effector T cells, suggesting that T-bet acts upstream and through regulation of ZEB2. Collectively, we place ZEB2 in a larger transcriptional network that is responsible for the balance between terminal differentiation and formation of memory CD8(+) T cells.

Kidney injury is independent of endothelial HIF-1α.

UNLABELLED: Hypoxia-inducible transcription factors (HIFs) control cellular adaptation to low oxygen. In the kidney, activation of HIF is beneficial during injury; however, the specific contribution of HIF-1α in renal endothelial cells (EC) remains elusive. Since EC display tissue-specific heterogeneity, we investigated how HIF-1α affects key functions of glomerular EC in vitro and its contribution to renal development and pathophysiological adaptation to acute or chronic renal injury in vivo. Loss of HIF-1α in glomerular EC induces hypoxic cell death and reduces hypoxic adhesion of macrophages in vitro. In vivo, HIF-1α expression in EC in mouse kidneys is detectable but limited. Accordingly, EC-specific ablation of HIF-1α does not lead to developmental or phenotypical abnormalities in the kidney. Renal function and expression of adhesion molecules during acute ischemic kidney injury is independent of HIF-1α in EC. Likewise, inflammation and development of fibrosis after unilateral ureteric obstruction is not influenced by endothelial HIF-1α. Taken together, although HIF-1α exerts effects on glomerular EC in vitro, endothelial HIF-1α does not influence renal development and pathophysiological adaptation to kidney injury in vivo. This implies a profound difference of the hypoxic response of the renal vascular bed compared to other organs, such as the heart. This has implications for the development of pharmacological strategies targeting the endothelial hypoxic response pathways. KEY MESSAGE: HIF-1α controls hypoxic survival and adhesion on endothelial cells (EC) in vitro. In vivo, HIF-1α expression in renal EC is low. Deletion of HIF-1α in EC does not affect kidney development and function in mice. Renal function after acute and chronic kidney injury is independent of HIF-1α in EC. Data suggest organ-specific regulation of HIF-1α function in EC.

Inactivation of evenness interrupted (EVI) reduces experimental fibrosis by combined inhibition of canonical and non-canonical Wnt signalling.

OBJECTIVES: Canonical as well as non-canonical Wnt signalling pathways have emerged as core pathways of fibrosis. Their profibrotic effects are mediated via distinct intracellular cascades independently of each other. Thus, inhibition of both pathways may have additive antifibrotic effects. Here, we knocked down evenness interrupted (EVI) to simultaneously target for the first time canonical and non-canonical Wnt signalling in experimental fibrosis. METHODS: The antifibrotic effects of siRNA-mediated knockdown of EVI were evaluated in the mouse models of bleomycin-induced skin fibrosis and in fibrosis induced by adenoviral overexpression of a constitutively active TGF-ß receptor I (AdTBRI). RESULTS: Knockdown of EVI decreased the release of canonical and non-canonical Wnt ligands by fibroblasts and reduced the activation of canonical and non-canonical Wnt cascades in experimental fibrosis with decreased accumulation of ß-catenin and phosphorylated JNK and cJun. Inactivation of EVI exerted potent antifibrotic effects and reduced dermal thickening, myofibroblast differentiation and accumulation of collagen in the mouse models of bleomycin-induced and AdTBR-induced fibrosis. CONCLUSIONS: Inhibition of Wnt secretion by knockdown of EVI inhibits canonical and non-canonical Wnt signalling and effectively reduces experimental fibrosis in different preclinical models. Inhibition of Wnt secretion may thus be an interesting approach for the treatment of fibrosis.

BK viremia and polyomavirus nephropathy in 352 kidney transplants; risk factors and potential role of mTOR inhibition.

BACKGROUND: Polyomavirus BK nephropathy (PyVAN) remains an important cause of early graft dysfunction and graft loss in kidney transplantation. METHODS: In this retrospective, single centre cohort study we studied the incidence and outcome of BK viral infection in 352 patients transplanted in 2008-2011. RESULTS: During follow-up viral replication was detected in 48 patients (13.6%); 22 patients (6.2%) had biopsy proven PyVAN.In multivariate logistic regression analyses risk factors for BK-viremia were lack of enrolment into randomized controlled trials (RCTs), biopsy proven acute rejections, cytomegaly virus (CMV) serostatus of both donor and recipient and previous transplantation.In patients without PyVAN reduction or switch of immunosuppression was associated with rapid viral clearance and stable graft function. In contrast, in most patients with PyVAN graft function deteriorated and 5 patients prematurely lost their allograft. Switch of immunosuppression to a low dose cyclosporine plus mTOR inhibitor based regimen in patients with PyVAN was safe, well tolerated and tended to be associated with a better short-term outcome in terms of graft function compared to reduction of existing immunosuppression alone. CONCLUSIONS: With the lack of licensed anti-polyoma viral drugs reduction or conversion of immunosuppression remains the mainstay of therapy in patients with PyVAN. The combination of low dose cyclosporine plus mTOR inhibition appears to be safe and warrants further investigation.

HIF-1α activation results in actin cytoskeleton reorganization and modulation of Rac-1 signaling in endothelial cells.

BACKGROUND: Hypoxia is a major driving force in vascularization and vascular remodeling. Pharmacological inhibition of prolyl hydroxylases (PHDs) leads to an oxygen-independent and long-lasting activation of hypoxia-inducible factors (HIFs). Whereas effects of HIF-stabilization on transcriptional responses have been thoroughly investigated in endothelial cells, the molecular details of cytoskeletal changes elicited by PHD-inhibition remain largely unknown. To investigate this important aspect of PHD-inhibition, we used a spheroid-on-matrix cell culture model. RESULTS: Microvascular endothelial cells (glEND.2) were organized into spheroids. Migration of cells from the spheroids was quantified and analyzed by immunocytochemistry. The PHD inhibitor dimethyloxalyl glycine (DMOG) induced F-actin stress fiber formation in migrating cells, but only weakly affected microvascular endothelial cells firmly attached in a monolayer. Compared to control spheroids, the residual spheroids were larger upon PHD inhibition and contained more cells with tight VE-cadherin positive cell-cell contacts. Morphological alterations were dependent on stabilization of HIF-1α and not HIF-2α as shown in cells with stable knockdown of HIF-α isoforms. DMOG-treated endothelial cells exhibited a reduction of immunoreactive Rac-1 at the migrating front, concomitant with a diminished Rac-1 activity, whereas total Rac-1 protein remained unchanged. Two chemically distinct Rac-1 inhibitors mimicked the effects of DMOG in terms of F-actin fiber formation and orientation, as well as stabilization of residual spheroids. Furthermore, phosphorylation of p21-activated kinase PAK downstream of Rac-1 was reduced by DMOG in a HIF-1α-dependent manner. Stabilization of cell-cell contacts associated with decreased Rac-1 activity was also confirmed in human umbilical vein endothelial cells. CONCLUSIONS: Our data demonstrates that PHD inhibition induces HIF-1α-dependent cytoskeletal remodeling in endothelial cells, which is mediated essentially by a reduction in Rac-1 signaling.

Loss of epithelial hypoxia-inducible factor prolyl hydroxylase 2 accelerates skin wound healing in mice.

Skin wound healing in mammals is a complex, multicellular process that depends on the precise supply of oxygen. Hypoxia-inducible factor (HIF) prolyl hydroxylase 2 (PHD2) serves as a crucial oxygen sensor and may therefore play an important role during reepithelialization. Hence, this study was aimed at understanding the role of PHD2 in cutaneous wound healing using different lines of conditionally deficient mice specifically lacking PHD2 in inflammatory, vascular, or epidermal cells. Interestingly, PHD2 deficiency only in keratinocytes and not in myeloid or endothelial cells was found to lead to faster wound closure, which involved enhanced migration of the hyperproliferating epithelium. We demonstrate that this effect relies on the unique expression of ß3-integrin in the keratinocytes around the tip of the migrating tongue in an HIF1α-dependent manner. Furthermore, we show enhanced proliferation of these cells in the stratum basale, which is directly related to their attenuated transforming growth factor ß signaling. Thus, loss of the central oxygen sensor PHD2 in keratinocytes stimulates wound closure by prompting skin epithelial cells to migrate and proliferate. Inhibition of PHD2 could therefore offer novel therapeutic opportunities for the local treatment of cutaneous wounds.

Inactivation of tankyrases reduces experimental fibrosis by inhibiting canonical Wnt signalling.

OBJECTIVES: Canonical Wnt signalling has recently emerged as a key mediator of fibroblast activation and tissue fibrosis in systemic sclerosis. Here, we investigated tankyrases as novel molecular targets for inhibition of canonical Wnt signalling in fibrotic diseases. METHODS: The antifibrotic effects of the tankyrase inhibitor XAV-939 or of siRNA-mediated knockdown of tankyrases were evaluated in the mouse models of bleomycin-induced dermal fibrosis and in experimental fibrosis induced by adenoviral overexpression of a constitutively active TGF-ß receptor I (Ad-TBRI). RESULTS: Inactivation of tankyrases prevented the activation of canonical Wnt signalling in experimental fibrosis and reduced the nuclear accumulation of ß-catenin and the mRNA levels of the target gene c-myc. Treatment with XAV-939 or siRNA-mediated knockdown of tankyrases in the skin effectively reduced bleomycin-induced dermal thickening, differentiation of resting fibroblasts into myofibroblasts and accumulation of collagen. Potent antifibrotic effects were also observed in Ad-TBRI driven skin fibrosis. Inhibition of tankyrases was not limited by local or systemic toxicity. CONCLUSIONS: Inactivation of tankyrases effectively abrogated the activation of canonical Wnt signalling and demonstrated potent antifibrotic effects in well-tolerated doses. Thus, tankyrases might be candidates for targeted therapies in fibrotic diseases.