Revised Arterial Anastomosis for Improving Murine Kidney Transplant Outcomes

Deletion of TLR4 reduces apoptosis and improves histology in a murine kidney transplant model

Acute kidney injury (AKI) after transplantation of human deceased donor kidneys is associated with upregulation of tubular toll like receptor 4 (TLR4), but whether TLR4 is required for AKI is unknown. We hypothesized that TLR4 knockout mice (TLR4KO) subjected to cold ischemia followed by kidney transplant (CI + Txp) would be protected from AKI. C57Bl/6J wild type or TLR4KO kidneys were subjected to CI + Txp into wild type recipients. Tubular cell apoptosis, tubular injury and cast formation were significantly improved in recipients of TLR4KO kidneys. TLR4KO kidneys also demonstrated significantly decreased expression of the effector caspase 8. Brush border injury scores and serum creatinine were not different in recipients of TLR4KO versus wild type kidneys. Phosphorylated RIP3 and MLKL through which TLR4 signals programmed necrosis were expressed in both recipient groups. In addition, TNF-α and TNFR1 expression were significantly increased in recipient serum and TLR4KO kidneys respectively after CI + Txp, suggesting continued activation of programmed necrosis despite TLR4 deletion. Our results suggest that TLR4 deletion decreases apoptosis via inhibition of the death receptor pathway and decreases tubular injury and cast formation.

The impact of Caspase-1 deletion on apoptosis and acute kidney injury in a murine transplant model

BACKGROUND

Caspase-1 knockout mice (Casp1KO) are protected from Acute Kidney Injury (AKI) after warm ischemia/reperfusion injury in non-transplant models. Since Caspase-1 plays a central role as an inflammatory response initiator, we hypothesized that Casp1KO mice would be protected from AKI following transplant.

METHODS

Renal tubular cells (RTECs) were subjected to cold storage and rewarming (CS/REW). C57Bl/6 J wild type or Casp1KO kidneys were subjected to CI for 30 min and then transplanted into wild type recipients (CI + Txp). The recipients underwent bilateral native nephrectomy at the time of transplant. Serum creatinine (sCr) was measured 24 h after native nephrectomy to assess transplant function.

RESULTS

We found that RTECs subjected to CS/REW had significantly increased expression of the Caspase-1 and inflammasome protein NLRP1. Wild type kidneys subjected to CI + Txp into wild type recipients also demonstrated significantly increased Caspase-1 and NLRP1 protein expression compared to kidneys transplanted from Casp1KO donors into wild type recipients. Caspase-1 deletion results in significantly decreased RTEC apoptosis in transplanted Casp1KO vs WT kidneys. Surprisingly, however, renal function, ATN scores including brush border injury, cast formation and tubular simplification were similar in both groups and not significantly different.

CONCLUSIONS

Our data suggest that other triggers of inflammation and programmed necrosis may need to be inhibited in addition to attenuating Caspase-1 to fully prevent AKI after kidney transplant. Importantly, requirements may be distinct for AKI induced by transplantation as opposed to other transient models such as the clamp model of AKI.

A Standardized Warm Ischemia Time for the Induction of Injury in Murine Kidney Transplants

One of the cornerstone research models used in our laboratories is the induction of ischemic injury through cold ischemia followed by warm ischemia to donor kidneys to mimic the clinical realities of transplantation. The experimental design of the present study included bilateral nephrectomies on the day of syngeneic kidney transplant, with serum creatinine measured 24 hours postoperatively to measure acute function. Cold ischemia time in these experiments was always 30 minutes, and warm ischemia time was not standardized but always recorded. It became apparent that some transplanted kidneys that should have displayed injury were producing close to normal serum creatinine levels on postoperative day 1. In reviewing our data, we found a potential correlation between warm ischemia time and serum creatinine, in particular a significant proportion of low serum creatinine results (0.48 ± 0.26 mg/dL vs 1.99 ± 1.11 mg/dL; P < .05) was associated with warm ischemia times that were significantly shorter than our historical average (29.2 ± 2.7 min vs 35.7 ± 2.2 min; P < .05). The kidneys with lower serum creatinine also displayed lower apoptosis and brush border injury scores and fewer tubular casts. Therefore, we concluded that establishing a minimum warm ischemia time was just as important as standardized cold ischemia time to ensure consistent injury in this model.

Injury Pathways That Lead to AKI in a Mouse Kidney Transplant Model

BACKGROUND

Prolonged cold ischemia (CI) is a risk factor for acute kidney injury after kidney transplantation. We endeavored to determine the pathways involved in the development of tubular cell injury and death before and after transplantation. We hypothesized that ex vivo cold storage before transplant would produce a different injury phenotype to that seen after engraftment in kidney transplants with or without CI.

METHODS

Four groups of mouse donor kidneys were studied: (1) nontransplanted control kidneys; (2) donor kidneys subjected to ex vivo cold ischemia (CI); (3) donor kidneys subjected to kidney transplant without CI (Txp); and (4) donor kidneys subjected to CI followed by transplantation (CI+Txp).

RESULTS

Acute kidney injury only occurred in the CI+Txp group, which had significantly increased sCr versus the Txp group and the control mice. Histologically, the CI group demonstrated significantly increased tubular cell apoptosis and caspase-9 expression, whereas the Txp group demonstrated only mild brush border injury without apoptosis or necrosis. In contrast, the CI+Txp group had tubular cell apoptosis associated with expression of caspase-8, TNFR1, and increased serum TNF-α. CI+Txp also led to significantly higher ATN scores in association with increased RIP1, RIP3, pMLKL, and TLR4 expression.

CONCLUSIONS

Our results suggest distinct therapies are needed at different times during organ preservation and transplantation. Prevention of apoptosis during cold storage is best achieved by inhibiting intrinsic pathways. In contrast, prevention of cell death and innate immunity after CI+Txp requires inhibition of both the extrinsic death receptor pathway via TNFR1 and caspase-8 and inhibition of programmed necrosis via TLR4 and TNFR1.

Cuff Anastomosis of Both Renal Artery and Vein to Minimize Thrombosis: A Novel Method of Kidney Transplantation in Mice

OBJECTIVES

Anastomosis of renal artery and renal vein in mouse models of kidney transplantation is technically challenging. Conventional technique using suture may result in vascular thrombosis. We developed a simple cuff method to anastomose both renal artery and vein.

MATERIALS AND METHODS

Briefly, the left renal artery was occluded at the junction with abdominal aorta using a small vessel clip, transected at the renal hilum, irrigated with heparinized saline, and passed through the lumen of a seamless tubing made of polyimide. The loose end of the artery was everted over the cuff and secured using an 8-0 silk suture. The cuffed artery was inserted into the donor renal artery and secured with an 8-0 suture. Anastomosis of the renal vein was performed similarly. Isograft transplantation was conducted using BALB/c mice as donor and recipient mice (n = 20). The total operative time was 77 ± 3 min, and the cold ischemic time of the graft kidney was minimized to 20 min. One animal was excluded due to anatomic variant vessels and another one died at three day after surgery without thrombosis.

RESULTS

Serum creatinine increased insignificantly after transplantation and remained stable over 12 weeks posttransplant. Five recipient mice were sacrificed for histologic examination at 12 weeks after transplantation. No vascular thrombosis was observed at the site of anastomosis. The isografts showed no evidence of acute and chronic lesions such as extinctive ischemic sclerosis and interstitial fibrosis.

CONCLUSION

In summary, cuff anastomosis can be used to eliminate thrombosis formation in the mouse model of kidney transplantation.

Caspase Inhibition During Cold Storage Improves Graft Function and Histology in a Murine Kidney Transplant Model

BACKGROUND

Prolonged cold ischemia is a risk factor for delayed graft function of kidney transplants, and is associated with caspase-3-mediated apoptotic tubular cell death. We hypothesized that treatment of tubular cells and donor kidneys during cold storage with a caspase inhibitor before transplant would reduce tubular cell apoptosis and improve kidney function after transplant.

METHODS

Mouse tubular cells were incubated with either dimethyl sulfoxide (DMSO) or Q-VD-OPh during cold storage in saline followed by rewarming in normal media. For in vivo studies, donor kidneys from C57BL/6 mice were perfused with cold saline, DMSO (vehicle), or QVD-OPh. Donor kidneys were then recovered, stored at 4°C for 60 minutes, and transplanted into syngeneic C57BL/6 recipients.

RESULTS

Tubular cells treated with a caspase inhibitor had significantly reduced capsase-3 protein expression, caspase-3 activity, and apoptotic cell death compared with saline or DMSO (vehicle) in a dose-dependent manner. Treatment of donor kidneys with a caspase inhibitor significantly reduced serum creatinine and resulted in significantly less tubular cell apoptosis, BBI, tubular injury, cast formation, and tubule lumen dilation compared with DMSO and saline-treated kidneys.

CONCLUSIONS

Caspase inhibition resulted in decreased tubular cell apoptosis and improved renal function after transplantation. Caspase inhibition may be a useful strategy to prevent cold ischemic injury of donor renal grafts.

An alternative technique of arterial anastomosis in mouse heart transplantation

OBJECTIVE

To investigate the characters and feasibility of continuous-interrupted suture (CIS) method for arterial anastomosis in mouse heart transplantation (MHT).

METHODS

A MHT model was adopted. End-to-end anastomosis of donor ascending aorta to recipient abdominal aorta was achieved by CIS or continuous suture (CS) method. In both groups, end-to-end anastomosis of pulmonary vein to inferior vena cava (IVC) was achieved by CS. Technical indexes and histological examination were analyzed between 2 groups.

RESULTS

The total operative time in CIS group was 92.83 ± 2.13 minutes, and in CS group was 92.40 ± 3.85 minutes. In CS group, artery anastomosis time was 20.13 ± 1.89 minutes; in CIS group, it was 20.36 ± 1.09 minutes. Additionally, venous anastomosis time in CS group was 14.80 ± 0.84 minutes, and in CIS group was 15.03 ± 0.85 minutes. Operation success rate in CIS group was 100%, and in CS group was 80%. There were no significant histological findings differences in graft between 2 groups. However, cell arrangement of anastomosis site was lightly irregular and the vascular alignment was poor in CS group. In CIS group, cell arrangement of anastomosis site was well arranged and vessels were well aligned.

CONCLUSIONS

CIS method could avoid arterial anastomosis-related complications induced by CS and improve the success rate.

Novel Therapeutics Identification for Fibrosis in Renal Allograft Using Integrative Informatics Approach

Chronic allograft damage, defined by interstitial fibrosis and tubular atrophy (IF/TA), is a leading cause of allograft failure. Few effective therapeutic options are available to prevent the progression of IF/TA. We applied a meta-analysis approach on IF/TA molecular datasets in Gene Expression Omnibus to identify a robust 85-gene signature, which was used for computational drug repurposing analysis. Among the top ranked compounds predicted to be therapeutic for IF/TA were azathioprine, a drug to prevent acute rejection in renal transplantation, and kaempferol and esculetin, two drugs not previously described to have efficacy for IF/TA. We experimentally validated the anti-fibrosis effects of kaempferol and esculetin using renal tubular cells in vitro and in vivo in a mouse Unilateral Ureteric Obstruction (UUO) model. Kaempferol significantly attenuated TGF-β1-mediated profibrotic pathways in vitro and in vivo, while esculetin significantly inhibited Wnt/β-catenin pathway in vitro and in vivo. Histology confirmed significantly abrogated fibrosis by kaempferol and esculetin in vivo. We developed an integrative computational framework to identify kaempferol and esculetin as putatively novel therapies for IF/TA and provided experimental evidence for their therapeutic activities in vitro and in vivo using preclinical models. The findings suggest that both drugs might serve as therapeutic options for IF/TA.

Therapy Modalities for Antibody Mediated Rejection in Renal Transplant Patients

INTRODUCTION

The aim of our study was to determine the effectiveness of immunoglobulin, rituximab and plasmapheresis in renal transplant patients with antibody mediated rejection (AMR).

PATIENTS AND METHODS

Fourteen renal transplant patients with AMR were included in this study. The mean age of the patients was 33.9 ± 10.3 years and 10 (71.4%) of them were male. Lymphocyte cross match was negative for all patients and 10 (71.4%) of them were living donor transplants. Six patients were administered tacrolimus, three patients cyclosporine, two patients everolimus, and three patients sirolimus for immunosuppression. The patients with AMR were administered IVIG, rituximab and plasmapheresis.

RESULTS

Patient survival rate was 100%, graft survival rate after AMR was 50% in the first year and 33% in the 2nd and third years. AMR developed 31.9 ± 25.9 months after transplantation. Seven (50%) patients lost their grafts. Delayed graft function was observed in 28.6%, chronic allograft dysfunction in 78.5%, diabetes after transplantation in 14.3%, and cytomegalovirus infection in 7.1% of the patients. At the last follow-up, the mean blood creatinine was 3.1 ± 1.4, the mean proteinuria was 2300 (1300-3300) mg/day and the mean GFR was 34.5 ± 17.6 ml/min. C4d was positive in peritubullar capillaries in all patients, while neutrophil accumulation in peritubular and glomerular capillaries was observed in 8 patients. Chronic allograft vasculopathy was observed in 12 patients.

CONCLUSION

AMR leads to progressive loss of renal function and has low graft survival. More effective treatment alternatives are needed for this clinical issue.