Sergio Dellepiane

Interaction between systemic inflammation and renal tubular epithelial cells

Systemic inflammation is known to target tubular epithelial cells (TECs), leading to acute kidney injury. Tubular cells have been implicated in the response to inflammatory mediators in ischaemic and septic renal damage. Moreover, loss of tubular cells by apoptosis or epithelial-to-mesenchymal transition may ingenerate conditions that lead to progression towards chronic kidney disease. On the other hand, TECs may actively contribute to the production of inflammatory mediators that may propagate the injury locally or in distant organs. In the present review, we discuss the tubular cell response and its contribution to systemic inflammation.

Endothelial progenitor cell-derived extracellular vesicles protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis

BACKGROUND Endothelial progenitor cells (EPCs) are known to induce tissue repair by paracrine mechanisms including the release of growth factors and extracellular vesicles (EVs), nanoparticles able to carry proteins and genetic information to target cells. The aim of this study was to evaluate whether EVs derived from EPCs may protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis. METHODS EVs were isolated by serial ultracentrifugation from supernatants of cultured human EPCs and characterized for their protein and RNA content. In vivo, EVs were injected i.v. in the experimental rat model of mesangiolytic anti-Thy1.1 glomerulonephritis evaluating renal function, proteinuria, complement activity and histological lesions. In vitro, the biological effects of EPC-derived EVs were studied in cultured rat mesangial cells incubated with anti-Thy1.1 antibody and rat or human serum as complement source. RESULTS After i.v. injection in Thy1.1-treated rats, EVs localized within injured glomeruli and inhibited mesangial cell activation, leucocyte infiltration and apoptosis, decreased proteinuria, increased serum complement haemolytic activity (CH50) and ameliorated renal function. EV treatment decreased intraglomerular deposition of the membrane attack complex (MAC or C5b-9) and expression of smooth muscle cell actin and preserved the endothelial antigen RECA-1 and the podocyte marker synaptopodin. The protective effect of EVs was significantly reduced by pre-treatment with a high dose of RNase (1 U/mL), suggesting a key role for EV-carried RNAs in these mechanisms. Indeed, EPC-derived EVs contained different mRNAs coding for several anti-apoptotic molecules and for the complement inhibitors Factor H, CD55 and CD59 and the related proteins. The in vitro experiments aimed to investigate the mechanisms of EV protection indicated that EVs transferred to mesangial cell mRNAs coding for Factor H, CD55 and CD59 and inhibited anti-Thy1.1 antibody/complement-induced apoptosis and C5b-9/C3 mesangial cell deposition. CONCLUSIONS EVs derived from EPCs exert a protective effect in Thy1.1 glomerulonephritis by inhibition of antibody- and complement-mediated injury of mesangial cells.

Detrimental cross-talk between sepsis and acute kidney injury: new pathogenic mechanisms, early biomarkers and targeted therapies

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Neutrophil Gelatinase Associated Lipocalin Is an Early and Accurate Biomarker of Graft Function and Tissue Regeneration in Kidney Transplantation from Extended Criteria Donors

Background Delayed graft function (DGF) is an early complication of kidney transplantation (KT) associated with increased risk of early loss of graft function. DGF increases using kidneys from extended criteria donors (ECD). NGAL is a 25KDa protein proposed as biomarker of acute kidney injury. The aim of this study was to investigate the role of NGAL as an early and accurate indicator of DGF and Tacrolimus (Tac) toxicity and as a mediator of tissue regeneration in KT from ECD. Methods We evaluated plasma levels of NGAL in 50 KT patients from ECD in the first 4 days after surgery or after Tac introduction. Results Plasma levels of NGAL at day 1 were significantly higher in DGF group. In the non DGF group, NGAL discriminated between slow or immediate graft function and decreased more rapidly than serum creatinine. NGAL increased after Tac introduction, suggesting a role as marker of drug toxicity. In vitro, hypoxia and Tac induced NGAL release from tubular epithelial cells (TEC) favoring an autocrine loop that sustains proliferation and inhibits apoptosis (decrease of caspases and Bax/Bcl-2 ratio). Conclusions NGAL is an early and accurate biomarker of graft function in KT from ECD favoring TEC regeneration after ischemic and nephrotoxic injury.

Long-Term Outcomes and Discard Rate of Kidneys by Decade of Extended Criteria Donor Age

BACKGROUND AND OBJECTIVES Extended criteria donors represent nowadays a main resource for kidney transplantation, and recovery criteria are becoming increasingly inclusive. However, the limits of this approach are not clear as well as the effects of extreme donor ages on long-term kidney transplantation outcomes. To address these issues, we performed a retrospective study on extended criteria donor kidney transplantation. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In total, 647 consecutive extended criteria donor kidney transplantations performed over 11 years (2003-2013) were included. Donor, recipient, and procedural variables were classified according to donor age decades (group A, 50-59 years old [n=91]; group B, 60-69 years old [n=264]; group C, 70-79 years old [n=265]; and group D, ≥80 years old [n=27]). Organs were allocated in single- or dual-kidney transplantation after a multistep evaluation including clinical and histologic criteria. Long-term outcomes and main adverse events were analyzed among age groups and in either single- or dual-kidney transplantation. Kidney discard rate incidence and causes were evaluated. RESULTS Median follow-up was 4.9 years (25th; 75th percentiles: 2.7; 7.6 years); patient and graft survival were comparable among age groups (5-year patient survival: group A, 87.8%; group B, 88.1%; group C, 88.0%; and group D, 90.1%; P=0.77; graft survival: group A, 74.0%; group B, 74.2%; group C, 75.2%; and group D, 65.9%; P=0.62) and between dual-kidney transplantation and single-kidney transplantation except for group D, with a better survival for dual-kidney transplantation (P=0.04). No difference was found analyzing complications incidence or graft function over time. Kidney discard rate was similar in groups A, B, and C (15.4%, 17.7%, and 20.1%, respectively) and increased in group D (48.2%; odds ratio, 5.1 with A as the reference group; 95% confidence interval, 2.96 to 8.79). CONCLUSIONS Discard rate and long-term outcomes are similar among extended criteria donor kidney transplantation from donors ages 50-79 years old. Conversely, discard rate was strikingly higher among kidneys from octogenarian donors, but appropriate selection provides comparable long-term outcomes, with better graft survival for dual-kidney transplantation.

Erratum to: The exciting “bench to bedside” journey of cell therapies for acute kidney injury and renal transplantation

Acute kidney injury (AKI) is characterized by an increasing incidence and poor outcomes in both developed and undeveloped countries. AKI is also acquiring importance in the setting of kidney transplantation (KT): besides all the classical forms of AKI that KT patients may undergo, several transplant-specific injuries can also lead to the loss of graft function. The mechanisms of tissue damage in native and grafted kidneys share several common pathogenic elements. Since appropriate therapeutic treatments are still lacking—probably due to the disease complexity—clinicians are forced to provide only supportive care. In this composite scenario, cell therapies represent an evolving frontier for AKI treatment in native and transplanted kidneys: ex-vivo manipulated stem or immune cells are able to counteract renal dysfunction by a wide range of biological mechanisms. In this review, we will discuss the potential applications of cell therapies in AKI and KT by analyzing the available clinical data and the most promising experimental prospects from a “bench to bedside” perspective.

Extracorporeal Treatments in Patients with Acute Kidney Injury and Sepsis

Acute kidney injury (AKI) is one of the most common sepsis complications, and AKI development increases the risk of sepsis episodes by affecting host immune competence. The concomitance of these 2 clinical syndromes is associated with an extremely poor prognosis with mortality rates ranging from 50 to 70%. These unacceptable outcomes reflect the poor knowledge of the underlying pathogenic mechanisms and the lack of appropriate diagnostic and therapeutic methodologies as well as of appropriate experimental models. However, in recent years new insights have revolutionized the scientific and clinical approach to sepsis-induced AKI (S-AKI) leading to encouraging results. The aim of this paper is to review the extracorporeal treatment of S-AKI with a focus on the most promising experimental techniques and the underlying molecular mechanisms.

Detrimental role of humoral signalling in cardio-renal cross-talk

In critically ill patients, any acute organ injury is associated with a sudden change of circulating factors that may play a role in distant organ dysfunction through a complex cross-talk. In this issue, Virzì and colleagues discuss the relevance of humoral signalling between heart and kidney, focusing on type 1 and type 3 cardio-renal syndrome. We herein review the mechanisms of heart-kidney cross-talk, discussing the role of circulating detrimental mediators in the pathogenetic mechanisms of cardio-renal syndrome.

Endothelial Progenitor Cell-Derived Extracellular Vesicles Inhibit Kidney Ischemia-Reperfusion Injury through the transfer of Specific Micrornoa and Mrna Coding for the Transcription Factor NRF2: Relevance for Delayed Kidney Graft Function

Background and Aim Activation of the complement cascade and oxidative stress in tubular epithelial and peritubular endothelial cells are hallmarks of delayed kidney graft function (DGF) due to ischemia-reperfusion injury (IRI). Endothelial progenitor cells (EPCs) are bone marrow-derived precursors known to reverse IRI by paracrine mechanisms including the release of extracellular vesicles (EV), small particles playing a role in intercellular communication through the transfer of specific mRNA and microRNA. The aim of this study was to evaluate the regenerative role of EPC-derived EV in kidney IRI through the horizontal transfer of RNA involved in the inhibition of complement activation and of oxidative stress. Methods EPC were isolated from peripheral blood of healthy volouteers and EV obtained by supernatant ultracentrifugation were characterized for size, protein and RNA content. We evaluated the effects of EV in a rat model of kidney IRI and in vitro in human tubular epithelial and endothelial cells cultured in hypoxia in vitro. Results EPC-derived EV sized 60-130 nm and carried different subsets of mRNAs and microRNAs able to modulate cell proliferation, angiogenesis and apoptosis (eNOS, Akt, Bcl-XL, miR-126, miR-296). By RT-PCR, we also found within EV mRNAs coding for the complement inhibitors factor H, DAF (CD55), CD59 and for the anti-oxidant transription factgor nrf2. In experimental kidney IRI, EPC EV localized within peritubular capillaries and tubular cells exerting morphologic and functional protection from by reducing tubular cell apoptosis/senescence, endothelial-to-mesenchymal transition (EndoMT) and leukocyte infiltration. Moreover, EV administration reduced C5b9 deposition and enhanced the expression of factor H, DAF, CD59 and nrf2 in the ischemic kidney. In vitro, EV reduced hypoxia-induced apoptosis/senescence of tubular epithelial (caspase activation, Klotho expression) and endothelial cells (EndoMT) by up-regulating the expression of factor H, DAF, CD59 and nrf2, thus confirming the in vivo data. The role of specific mRNA transfer to hypoxic renal cells was confirmed by experiments using RNase-treated EV, EV released from EPC engineered to knock-down the complement inhibitors or nrf2 by specific siRNA, or EV produced by EPC transfected with siRNA Dicer, the intracellular enzyme essential for microRNA maturation. Conclusions EPC-derived EV protect the kidney from IRI by delivering pro-angiogenic, anti-apoptotic, complement inhibitors and anti-oxidant microRNAs and mRNAs coding for factor H, DAF, CD59 and nrf2 to injured tubular epithelial and endothelial cells. These results suggest the potential use of EPC-derived EVs as therapeutic tool to avoid or at least to limit IRI-associated DGF in kidney transplantation without the potential adverse effects of whole stem cell therapy including maldifferentiation and tumorigenesis.

Humoral Mediators in Sepsis

Abstract Local infection may develop into a systemic inflammatory response syndrome that encompasses a complex mosaic of interconnected events, including the so-called compensatory antiinflammatory response syndrome. A 2002 hypothesis holds that a defective host innate response may render bacteria resistant to host recognition and defense mechanisms, leading to systemic infection and sepsis. In higher organisms, a variety of host defense mechanisms control the resident microflora and, in most cases, effectively prevent invasive microbial disease. Many microbial pathogens avoid host recognition or dampen the subsequent immune activation through sophisticated interactions with host responses, but some pathogens even benefit from the inflammatory reaction. The defective response of the host may depend on a unique genetic makeup of a pathogen that can render it more resistant to antibiotics or on disturbances in the integrated response of the innate arm and the adaptive arm of the immune system. Differences in reactivity of dendritic cells to microbial molecules through Toll-like receptors are associated with susceptibility and resistance to microbes.