Anke Jurisch

Identification of a microRNA signature of renal ischemia reperfusion injury

Renal ischemia reperfusion injury (IRI) is associated with significant morbidity and mortality. Given the importance of microRNAs (miRNAs) in regulating gene expression, we examined expression profiles of miRNAs following renal IRI. Global miRNA expression profiling on samples prepared from the kidneys of C57BL/6 mice that underwent unilateral warm ischemia revealed nine miRNAs (miR-21, miR-20a, miR-146a, miR-199a-3p, miR-214, miR-192, miR-187, miR-805, and miR-194) that are differentially expressed following IRI when compared with sham controls. These miRNAs were also differently expressed following IRI in immunodeficient RAG-2/common γ-chain double-knockout mice, suggesting that the changes in expression observed are not significantly influenced by lymphocyte infiltration and therefore define a lymphocyte-independent signature of renal IRI. In vitro studies revealed that miR-21 is expressed in proliferating tubular epithelial cells (TEC) and up-regulated by both cell-intrinsic and -extrinsic mechanisms resulting from ischemia and TGF-β signaling, respectively. In vitro, knockdown of miR-21 in TEC resulted in increased cell death, whereas overexpression prevented cell death. However, overexpression of miR-21 alone was not sufficient to prevent TEC death following ischemia. Our findings therefore define a molecular fingerprint of renal injury and suggest miR-21 may play a role in protecting TEC from death.

Machine perfusion or cold storage in organ transplantation: indication, mechanisms, and future perspectives

Most organs are currently preserved by cold storage (CS) prior to transplantation. However, as more so called marginal donor organs are utilized, machine perfusion has regained clinical interest. Recent studies have demonstrated advantages of pulsatile perfusion over CS preservation for kidney transplantation. However, it remains unclear whether there is a significant benefit of one preservation method over the other in general, or, whether the utilization of particular preservation approaches needs to be linked to organ characteristics. Proposed protective mechanisms of pulsatile perfusion remain largely obscure. It can be speculated that pulsatile perfusion may not only provide nutrition and facilitate the elimination of toxins but also trigger protective mechanisms leading to the amelioration of innate immune responses. Those aspects may be of particular relevance when utilizing grafts with suboptimal quality which may have an increased vulnerability to ischemia/reperfusion injury and compromised repair mechanisms. This review aims to enunciate the principles of organ perfusion and preservation as they relate to indication, aspects of organ protection and to highlight future developments.

TIM-3: A Novel Regulatory Molecule of Alloimmune Activation

T cell Ig domain and mucin domain (TIM)-3 has previously been established as a central regulator of Th1 responses and immune tolerance. In this study, we examined its functions in allograft rejection in a murine model of vascularized cardiac transplantation. TIM-3 was constitutively expressed on dendritic cells and natural regulatory T cells (Tregs) but only detected on CD4+FoxP3− and CD8+ T cells in acutely rejecting graft recipients. A blocking anti–TIM-3 mAb accelerated allograft rejection only in the presence of host CD4+ T cells. Accelerated rejection was accompanied by increased frequencies of alloreactive IFN-γ–, IL-6–, and IL-17–producing splenocytes, enhanced CD8+ cytotoxicity against alloantigen, increased alloantibody production, and a decline in peripheral and intragraft Treg/effector T cell ratio. Enhanced IL-6 production by CD4+ T cells after TIM-3 blockade plays a central role in acceleration of rejection. Using an established alloreactivity TCR transgenic model, blockade of TIM-3 increased allospecific effector T cells, enhanced Th1 and Th17 polarization, and resulted in a decreased frequency of overall number of allospecific Tregs. The latter is due to inhibition in induction of adaptive Tregs rather than prevention of expansion of allospecific natural Tregs. In vitro, targeting TIM-3 did not inhibit nTreg-mediated suppression of Th1 alloreactive cells but increased IL-17 production by effector T cells. In summary, TIM-3 is a key regulatory molecule of alloimmunity through its ability to broadly modulate CD4+ T cell differentiation, thus recalibrating the effector and regulatory arms of the alloimmune response.

Targeting of Macrophage Activity by Adenovirus-Mediated Intragraft Overexpression of TNFRp55-Ig, IL-12p40, and vIL-10 Ameliorates Adenovirus-Mediated Chronic Graft Injury, whereas Stimulation of Macrophages by Overexpression of IFN-γ Accelerates Chronic Graft Injury in a Rat Renal Allograft Model

Adenovirus (Ad)-mediated gene transfer of immunoregulatory molecules prevents acute allograft rejection. It is here analyzed for the first time whether this approach may prevent the development of chronic renal allograft injury in rats. Renal allografts (F344-->Lewis rat) were ex vivo transduced in group I with control Ad-construct, group II with three different therapeutic Ad-constructs expressing the immunoregulatory molecules vIL-10, TNFRp55-Ig, and IL-12p40, and group III with AdIFN-gamma. Group IV served as untreated controls. Control grafts (IV) showed increasing proteinuria during the 24-wk follow-up. Chronic graft injury was accelerated by Ad-control (I) and even more by AdIFN-gamma (III). All rats carrying the AdIFN-gamma-transduced grafts died within 12 to 13 wk by advanced chronic renal failure associated with strong immune cell infiltration and immune gene expression. By contrast, the Ad-therapy group II showed less inflammation and improved graft histology and function if compared with the groups I and III. Moreover, significantly less infiltrating ED-1(+) macrophages and an improved histologic score even if compared with untreated controls (IV) was observed. However, after disappearance of therapeutic gene expression, group II showed increasing proteinuria probably as result of late T cell activation to the Ad-encoded proteins. Ex vivo transduction of allografts with Ad-control or even more AdIFN-gamma expression promotes intragraft inflammation and chronic graft injury. Targeting macrophage activation by a cocktail of therapeutic genes improved the results. These data support the pathogenetic role of cytokines in chronic graft injury; however, they also show the limitations of the Ad-mediated gene transfer.

Induction of carbon monoxide in donor animals prior to organ procurement reduces graft immunogenicity and inhibits chronic allograft dysfunction.

Background. Nonspecific inflammatory damages occurring prior to organ transplantation reduce long-term graft survival. Here, we tested the beneficial effects of carbon monoxide (CO) induction by methylene chloride (MC). Methods. Fischer-344 (F-344 Rat) or Dark Agouti (DA Rat) donor animals were either treated with MC four hours prior to organ removal or remained untreated. Kidneys were transplanted into Lewis (LEW) recipients. The low responder strain combination (F-344→LEW) was studied for long-term graft changes. Dendritic cells (DCs) migration and early changes were followed in additional groups of a high responding donor/recipient strain combination (DA→LEW). Native kidneys of uninephrectomized, age-matched normal animals served as controls. Results. Following MC application COHb peaked within two hours in donor animals. Renal function and morphology improved significantly in renal allografts of CO induced donor animals and were comparable to native controls long-term (24 wks). Early after transplantation (24 hr) donor-derived DCs, CD4+ T-cells and alloreactive T-cells were significantly reduced following the engraftment of organs from treated donors. In addition, a trend towards a Th1/Th2 shift and a significant intragraft reduction of CD3 mRNA expression was observed. Conclusion. Donor treatment for the induction of CO reduced graft immunogenicity and inhibited chronic allograft nephropathy.

Short-term immunosuppressive treatment of the donor ameliorates consequences of ischemia/ reperfusion injury and long-term graft function in renal allografts from older donors1

Background. Grafts from so-called “marginal donors” are increasingly used for organ transplantation. The combination of reduced organ quality and additional inflammatory damages may be particularly detrimental in these grafts. In a previous study, we showed the beneficial effects on long-term graft outcome of “suboptimal” grafts by the induction of heme oxygenase-1. Here we tested the impact of short-term donor treatment with established immunosuppressants. Methods. Twelve-month-old Fischer 344 donor rats either were treated with prednisolone, mycophenolate mofetil, RAD, or FK506 24 hr and 1 hr before organ harvesting or remained untreated. Renal allografts were perfused with University of Wisconsin solution and kept at 4°C for an ischemic period of 2 hr. Morphologic, immunohistologic, and real time reverse transcriptase-polymerase chain reaction analyses for relevant markers were performed at serial intervals and at the end of the observation period (6 months). Results. All animals survived the observation period, although the ischemic time resulted in accelerated chronic graft dysfunction. Grafts from donors treated with prednisolone or FK506 demonstrated significantly improved graft function and structure by 6 months. Mononuclear infiltrates were significantly reduced by the end of the observation period, whereas intragraft mRNA levels of tumor necrosis factor-&agr; and interleukin-10 were significantly altered during the early period after transplantation. Minor improvements in graft function and histologic alterations of suboptimal grafts were observed after pretreatment with mycophenolate mofetil and RAD. Conclusion. Donor treatment with approved immunosuppressants, in particular prednisolone or FK506, represents a novel therapeutic strategy of clinical relevance, most importantly when using grafts from marginal donors.

Alterations of the immune response with increasing recipient age are associated with reduced long-term organ graft function of rat kidney allografts1

Background. Clinically, an increasing number of older recipients are listed for transplantation. We examined recipient age-associated alterations of the immune response and their effects on graft function. Methods. Three- and 18-month-old Lewis (LEW) rats received kidneys from 3- and 18-month-old Fischer 344 (F344) rats (1.5 mg/kg/d cyclosporine A for 10 days; n=6/group) and were observed for 180 days. In additional groups, double kidney transplantations were performed to determine the impact of nephron mass and recipient age on graft outcome. Results. All young recipients but only 66% of old recipients survived the observation period. Increasing recipient age resulted in a significant decrease in renal allograft function (P <0.001), more advanced morphologic evidence of chronic allograft damage (P <0.001), and greater cellular infiltration (P <0.05) and major histocompatibility complex expression (P <0.01) within grafts. Additional in vitro studies examined age-related changes in the cellular immune response by enzyme-linked immunosorbent assay, fluorescence-activated cell sorter analysis, and alloreactive enzyme-linked immunospot: splenocytes from old LEW rats produced significantly more interleukin (IL)-2 (P <0.0001), IL-4 (P <0.05), interferon (IFN)-&ggr; (P <0.0001), and tumor necrosis factor-&agr; (P <0.05). IFN-&ggr;–producing memory-type T cells were significantly elevated in older rats (P <0.0001). Moreover, they revealed significantly more alloreactive T cells directed against F344 (146±64.2 and 512±277/106 T cells; P <0.05). Double renal allografts from young donors into old recipients confirmed an independent effect of recipient age on the acceleration of chronic graft deterioration. Conclusions. The enhanced cellular immune responsiveness in elderly recipients was associated with advanced chronic graft injury. Clinically, older recipients may need a modified immunosuppression.

Prolonged Graft Survival in Older Recipient Mice Is Determined by Impaired Effector T-Cell but Intact Regulatory T-Cell Responses

Elderly organ transplant recipients represent a fast growing segment of patients on the waiting list. We examined age-dependent CD4+ T-cell functions in a wild-type (WT) and a transgenic mouse transplant model and analyzed the suppressive function of old regulatory T-cells. We found that splenocytes of naïve old B6 mice contained significantly higher frequencies of T-cells with an effector/memory phenotype (CD4+CD44highCD62Llow). However, in-vitro proliferation (MLR) and IFNγ-production (ELISPOT) were markedly reduced with increasing age. Likewise, skin graft rejection was significantly delayed in older recipients and fewer graft infiltrating CD4+T-cells were observed. Old CD4+ T-cells demonstrated a significant impaired responsiveness as indicated by diminished proliferation and activation. In contrast, old alloantigen-specific CD4+CD25+FoxP3+ T-cells demonstrated a dose-dependent well-preserved suppressor function. Next, we examined characteristics of 18-month old alloreactive T-cells in a transgenic adoptive transfer model. Adoptively transferred old T-cells proliferated significantly less in response to antigen. Skin graft rejection was significantly delayed in older recipients, and graft infiltrating cells were reduced. In summary, advanced recipient age was associated with delayed acute rejection and impaired CD4+ T-cell function and proliferation while CD4+CD25+FoxP3+ T-cells (Tregs) showed a well-preserved function.

Short-term TNF-alpha inhibition reduces short-term and long-term inflammatory changes post-ischemia/reperfusion in rat intestinal transplantation.

Background Tumor necrosis factor (TNF)-&agr; inhibition was shown to reduce ischemia/reperfusion injury (IRI) after intestinal transplantation (ITX). We studied the effects of different TNF&agr; inhibitors on acute IRI and long-term inflammatory responses in experimental ITX. Methods Orthotopic ITX was performed in an isogenic ischemia/reperfusion model in Lewis rats. The TNF&agr; inhibition groups received infliximab post-reperfusion; etanercept pre-reperfusion and at postoperative days (POD) 1, 3, 5, and 7; or pentoxifylline pre-reperfusion and at POD 1 to 5. Tissue samples were taken from proximal and distal graft sections and mesenteric lymph nodes at 20 min, 12 hr, 7 day, and 6 months post-reperfusion for histopathology, immunohistology, terminal deoxyribosyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and real-time RT-PCR. Lung sections were stained for the myeloperoxidase assay. Results TNF&agr; inhibitors decreased inflammatory changes after IRI in all treatment groups. Infliximab significantly improved 7-day survival and reduced the histological and immunohistochemical signs of IRI, the numbers of graft-infiltrating T cells and ED1+ monocytes and macrophages, and pulmonary neutrophil infiltration, and also enhanced the accumulation of cytoprotective markers. Graft injury was more prominent in the distal graft than in the proximal graft in all groups, regardless of TNF&agr; inhibition. Conclusion Infliximab significantly reduced both acute IRI and, as with other TNF&agr; inhibitors, long-term inflammatory responses after rat ITX. TNF&agr; inhibition may help diminish chronic inflammatory long-term effects and avoid chronic allograft enteropathy.

Synergistic effects of prolonged warm ischemia and donor age on the immune response following donation after cardiac death kidney transplantation.

BACKGROUND Organs from DCD (donation after cardiac death) donors are increasingly used for transplantation. The impact of advanced donor age and warm ischemia on the immune response of the recipient has not been studied. We developed a novel and clinically relevant model of DCD kidney transplantation and investigated the effects of donor age and prolonged warm ischemia on the recipient immune response after following DCD kidney transplantation. METHODS DCD grafts from young and old F-344 donor rats were engrafted into LEW recipients who were nephrectomized bilaterally after a short (20 minutes) or prolonged (45 minutes) warm ischemia time. RESULTS Analysis of the recipients immune response early after transplantation showed an enhanced innate and adaptive immune response when old DCD kidneys were engrafted. Next, we studied DCD recipients with a supportive, contralateral native kidney in place, which allowed the recovery of the transplanted DCD kidney. Old DCD kidneys, demonstrated an impaired renal function associated with pronounced histomorphologic graft deterioration and an enhanced immune response by day 100 after transplantation. Interestingly, young DCD kidneys with a long warm ischemic time recovered from acute tubular necrosis and did not stimulate the long-term immune response. CONCLUSION Our observations emphasize that prolonged warm ischemic time and advanced donor age augment the immune response after transplantation of DCD grafts. These results provide an experimental model and a mechanistic framework of clinically relevant aspects in DCD donation.