Chronic renal allograft damage after transplantation: what are the reasons, what can we do?

Regulatory B Cells Profile in Kidney Transplant Recipients With Chronic-Active Antibody-Mediated Rejection

This study aims to reveal the relationship between regulatory B cell (Breg) subsets and chronic-active antibody-mediated rejection (c-aABMR) in renal transplant recipients. Our study involved 3 groups of participants: renal transplant recipients with biopsy-proven c-aABMR as the chronic rejection group (c-aABMR, n = 23), recipients with stable graft functions as the patient control group (PC; n = 11), and healthy volunteers (HV; n = 11). Breg subsets, immature/transitional B cells, plasmablastic cells, B10 cells, and BR1 cells were isolated from venous blood samples by flow cytometry. The median values of Breg frequencies in the total lymphocyte population were analyzed. There were no significant differences between the study groups for immature and/or transitional B cell frequencies. Plasmablastic cell frequencies of the c-aABMR group (7.80 [2.10-27.40]) and the PC group (6.00 [1.80-55.50]) were similar, but both of these values were significantly higher than the HVs' (3.40 [1.20-8.50]), (respectively, P = .005 and P = .039). B10 cell frequencies were also similar, comparing the c-aABMR (4.20 [0.10-7.40]) and the PC groups (4.10 [0.10-5.90]), whereas the HVs (5.90 [2.90-8.50]) had the highest B10 cell frequency with an only statistical significance against the PC group (respectively, P = .09 and P = .028). The c-aABMR and the PC groups were similar regarding BR1 cell frequencies. However, the HV group significantly had the highest frequency of BR1 cells (5.50 [2.80-10.80]) than the other groups (P < .001 for both). We demonstrated that frequencies of B10 and BR1 cells were higher in HVs than in transplant recipients, regardless of rejection state. However, there was no significant relation between Breg frequencies and the c-aABMR state.

Classic and Current Opinions in Human Organ and Tissue Transplantation

Graft tolerance is a pathophysiological condition heavily reliant on the dynamic interaction of the innate and adaptive immune systems. Genetic polymorphism determines immune responses to tissue/organ transplantation, and intricate humoral and cell-mediated mechanisms control these responses. In transplantation, the clinician's goal is to achieve a delicate equilibrium between the allogeneic immune response, undesired effects of the immunosuppressive drugs, and the existing morbidities that are potentially life-threatening. Transplant immunopathology involves sensitization, effector, and apoptosis phases which recruit and engages immunological cells like natural killer cells, lymphocytes, neutrophils, and monocytes. Similarly, these cells are involved in the transfer of normal or genetically engineered T cells. Advances in tissue transplantation would involve a profound knowledge of the molecular mechanisms that underpin the respective immunopathology involved and the design of precision medicines that are safe and effective.

Ficolin-2 Gene rs7851696 Polymorphism is Associated with Delayed Graft Function and Acute Rejection in Kidney Allograft Recipients

Ficolin-2 is an activator of the complement system that acts via the lectin pathway. Complement activation plays a substantial role in the renal injury inherent to kidney transplantation. In this study, we examined the associations between ficolin-2 gene polymorphisms in exon 8 and kidney allograft function. This study comprised 270 Caucasian deceased-donor renal transplant recipients. The following parameters were recorded in each case: delayed graft function (DGF), acute rejection (AR), and chronic allograft dysfunction. Among patients with DGF, we observed a significantly increased frequency of rs7851696 GT and TT genotypes as well as T allele (TT + GT vs GG OR 1.98, 95% CI 1.12-3.48, p = 0.02; T vs G OR 2.08, 95% CI 1.27-3.41, p = 0.005). There was also an increased frequency of rs4521835 GG and TG genotypes as well as G alleles; however, these differences were on the borderline of statistical significance (GG + TG vs TT, OR 1.75, 95% CI 0.98-3.12, p = 0.07; G vs T OR 1.45, 95% CI 1.00-2.09, p = 0.050). In addition, we observed an increased frequency of acute allograft rejection in carriers of ficolin-2 rs7851696 T alleles on the borderline of statistical significance (TT + GT vs GG OR 1.75, 95% CI 0.97-3.16, p = 0.08), but the frequency of T allele was significantly higher in patients with AR (T vs G OR 1.71, 95% CI 1.02-2.87, p = 0.048). The results of our study suggest that ficolin-2 rs7851696 gene polymorphism influences kidney allograft functions, with T allele increasing the risk of DGF and AR.

Transplantology: Challenges for Today

Clinical transplantology in Poland had its 50th anniversary this year. With the early and long results comparable to the best achieved in the world leading centers, we face old and completely new challenges for this medical speciality. Main and growing challenge is insufficient number of available organs. With less than 15 donors/mln population/year Poland stay in the lower row of European countries in this measurement of transplant activity. Donation system is not efficient enough and we lose a big number of potential donors still. Living donation (with the exception for the fragments of the liver) remains low despite of different initiatives made so far on the national and local levels. Donation after cardiac death is possible from the point of Polish juridical regulations, but since last 3 years had not showed real impact on country donation rates (only three procedures done). Methods of tissue typing remain slow and cause relatively long times of cold ischemia for kidney programs. Second main challenge is chronic rejection causing loss of organs in the long-term follow-up and no efficient treatment employed. The emerging possibility of tolerance induction despite of plenty of new protocols proposition in the publications does not show up a clinical everyday practice in work. The same is with xenotransplantation promises; even we were informed recently that till 2030 such genetically modified porcine organs will be available. The next challenge is production of organs and tissues from own recipients cells installed on the different scaffolds or 3D printed. Other challenge is the personnel working in this field. We observe like in the other European countries lack of new candidates for work in this field together with serious problems of nursing staff, being a catastrophic perspective in country medical service in general, not only in transplant centers. The last but not least challenge is financial side of transplant programs.

Small interfering RNA targeting TNF-α gene significantly attenuates renal ischemia-reperfusion injury in mice

Tumor necrosis factor-alpha (TNF-α) has been found to be centrally involved in the development of ischemia-reperfusion injury (IRI)-induced inflammation and apoptosis. Knockdown of TNF-α gene using small interfering RNA (siRNA) may protect renal IRI. Renal IRI was induced in mice by clamping the left renal pedicle for 25 or 35 min. TNF-α siRNA was administered intravenously to silence the expression of TNF-α. The therapeutic effects of siRNA were evaluated in terms of renal function, histological examination, and overall survival following lethal IRI. A single systemic injection of TNF-α siRNA resulted in significant knockdown of TNF-α expression in ischemia-reperfusion injured kidney. In comparison with control mice, levels of BUN and serum creatinine were significantly reduced in mice treated with siRNA. Pathological examination demonstrated that tissue damage caused by IRI was markedly reduced as a result of TNF-α siRNA treatment. Furthermore, survival experiments showed that nearly 90% of control mice died from lethal IRI, whereas more than 50% of siRNApretreated mice survived until the end of the eight-day observation period. We have demonstrated for the first time that silencing TNF-α by specific siRNA can significantly reduce renal IRI and protect mice against lethal kidney ischemia, highlighting the potential for siRNA-based clinical therapy.

Calcineurin-inhibition Results in Upregulation of Local Renin and Subsequent Vascular Endothelial Growth Factor Production in Renal Collecting Ducts

BACKGROUND

Tacrolimus (Tac) and Cyclosporine A (CyA) calcineurin inhibitors (CNIs) are 2 effective immunosuppressants which are essential to prevent allograft rejection. Calcineurin inhibitors are known to be nephrotoxic. However, the precise mechanism of nephrotoxicity is not fully understood. In this study, we investigated the in vivo effects of CNIs on the local renal renin-angiotensin system in the collecting duct (CD).

METHODS

Three-week-old mice were treated with either vehicle, CyA (2 mg/kg per day), Tac (0.075 mg/kg per day), CyA + Aliskiren (25 mg/kg per day), or Tac + Aliskiren for 3 weeks. Serum creatinine was measured. Renin and vascular endothelial growth factor (VEGF) contents in CD were evaluated with flow cytometry and multiphoton microscopy. The diameter of vessels was assessed with multiphoton microscopy, and the amount of renal collagen was determined by real-time polymerase chain reaction and Masson staining.

RESULTS

The elevated level of serum creatinine in CNI groups was abolished by Aliskiren. Flow cytometric analysis found elevated renin content in principal cells, which was prevented by Aliskiren. This result was further confirmed with multiphoton microscopy. The VEGF content in CD correlated with reduced capillary diameter and with the formation of fibrotic islands.

CONCLUSIONS

Calcineurin inhibitors induce production of renin in the CD that may contribute to decreased renal blood flow. In turn, CD responds with increased VEGF production, resulting in disproportional vessel growth, further worsening the local hypoxia and striped fibrosis surrounding the CDs. Aliskiren, a direct renin inhibitor blocks these effects and improves CNI-induced nephropathy by decreasing renin production in the CDs. Our data suggest that Aliskiren may be used for the prevention of CNI nephrotoxicity.

The need for minimization strategies: current problems of immunosuppression

New immunosuppressants and the better use of immunosuppressant combination therapy have led to significant improvements in renal allograft outcomes over the last decades. Yet, despite dramatic reduction in rejection rates and improvement in 1-year graft survival, long-term graft attrition rates remained rather constant. Current immunosuppressant combinations are frequently leading to overimmunosuppression and are increasing cardiovascular risk. Importantly, calcineurin inhibitors are nephrotoxic, contribute to cardiovascular risk and chronic allograft dysfunction. Furthermore, immunosuppressant-associated toxicities aggravate immune-mediated nephron injury and side effects lead to nonadherence, an identified important reason for late acute and chronic antibody-mediated rejections. The frequent development of a chronic humoral response indicates rather insufficient immunosuppression of current combinations than simple under-immunosuppression. While there is no evidence that increasing immunosuppressive doses will improve outcomes or reduce de novo HLA-antibody formation, there is clear evidence that adequate minimization strategies will reduce side effect burden. Because of low rejection risk, but frequent side effects, drug minimization is particularly relevant for the many maintenance patients. In summary, new therapeutic strategies need to be developed from adequately powered clinical trials for reduction of the many side effects of immunosuppressants. Such evidence-based and time-dependent immunosuppressive minimization strategies are needed to achieve better long-term outcomes in the future.

Requirement of B7-H1 in mesenchymal stem cells for immune tolerance to cardiac allografts in combination therapy with rapamycin

BACKGROUND

The potential of mesenchymal stem cells (MSCs) for immunosuppression has been tested in transplantation, but its mechanisms are not fully understood. This study investigated the role of MSC-expressing B7-H1 in the induction of immune tolerance to cardiac allografts by the combination therapy of MSCs and rapamycin (RAPA).

METHODS

The anti-alloimmunity of donor MSCs in the presence or absence of RAPA was examined in both mouse cardiac allograft model (C57BL/6 to BALB/c mice) and a variety of cultured immune cells. Immunohistochemical staining was used for the measurement of intragraft antibody deposition, and fluorescence-activated cell sorting (FACS) for the determination of serum alloantibodies and leukocyte phenotypes.

RESULTS

B7-H1 expression in cultured MSCs was up-regulated following IFN-γ stimulation. In transplant recipients, combination therapy of MSCs and RAPA induced immune tolerance to allografts, but blockade of B7-H1 on MSCs with monoclonal antibody abrogated the combination therapy-induced immune tolerance as heart allografts were rejected. The negative effect of MSC-expressing B7-H1 neutralization on graft survival was correlated with a reduction of regulatory immune cells (CD4(+)CD25(+)Foxp3(+) T cells, tolerogenic dendritic cells and IL-4(high)IL-10(High)CD83(low) B cells), and also with an increase in alloantibody (IgG and IgM) levels both inside the grafts and in the circulation as compared with un-neutralized controls. In vitro MSC-mediated suppression of antibody production and B cell proliferation depended on B7-H1 function and cell contact between CD19(+) B cells and MSCs.

CONCLUSION

These data suggest that MSC-expressing B7-H1 mediates the immune tolerance to cardiac allografts in recipients receiving MSC and RAPA combination therapy.

Biological pathways and potential targets for prevention and therapy of chronic allograft nephropathy

Renal transplantation (RT) is the best option for patients with end-stage renal disease, but the half-life is limited to a decade due to progressive deterioration of renal function and transplant failure from chronic allograft nephropathy (CAN), which is the leading cause of transplant loss. Extensive research has been done to understand the pathogenesis, the biological pathways of fibrogenesis, and potential therapeutic targets for the prevention and treatment of CAN. Despite the advancements in the immunosuppressive agents and patient care, CAN continues to remain an unresolved problem in renal transplantation. The aim of this paper is to undertake a comprehensive review of the literature on the pathogenesis, biological pathways of RT fibrogenesis, and potential therapeutic targets for the prevention and therapy of CAN.