The influence of donor brain death on long-term function of renal allotransplants in rats

Treatment with tetrahydrobiopterin overcomes brain death-associated injury in a murine model of pancreas transplantation

Brain death (BD) has been associated with an immunological priming of donor organs and is thought to exacerbate ischemia reperfusion injury (IRI). Recently, we showed that the essential nitric oxide synthase co-factor tetrahydrobiopterin (BH4) abrogates IRI following experimental pancreas transplantation. We therefore studied the effects of BD in a murine model of syngeneic pancreas transplantation and tested the therapeutic potential of BH4 treatment. Compared with sham-operated controls, donor BD resulted in intragraft inflammation reflected by induced IL-1ß, IL-6, VCAM-1, and P-selectin mRNA expression levels and impaired microcirculation after reperfusion (p < 0.05), whereas pretreatment of the BD donor with BH4 significantly improved microcirculation after reperfusion (p < 0.05). Moreover, BD had a devastating impact on cell viability, whereas BH4-treated grafts showed a significantly higher percentage of viable cells (p < 0.001). Early parenchymal damage in pancreatic grafts was significantly more pronounced in organs from BD donors than from sham or non-BD donors (p < 0.05), but BH4 pretreatment significantly ameliorated necrotic lesions in BD organs (p < 0.05). Pretreatment of the BD donor with BH4 resulted in significant recipient survival (p < 0.05). Our data provide novel insights into the impact of BD on pancreatic isografts, further demonstrating the potential of donor pretreatment strategies including BH4 for preventing BD-associated injury after transplantation.

Amniotic Fluid Derived Stem Cells with a Renal Progenitor Phenotype Inhibit Interstitial Fibrosis in Renal Ischemia and Reperfusion Injury in Rats

Objectives

Mesenchymal stem cells derived from human amniotic fluid (hAFSCs) are a promising source for cellular therapy, especially for renal disorders, as a subpopulation is derived from the fetal urinary tract. The purpose of this study was to evaluate if hAFSCs with a renal progenitor phenotype demonstrate a nephroprotective effect in acute ischemia reperfusion (I/R) model and prevent late stage fibrosis.

Methods

A total of 45 male 12-wk-old Wistar rats were divided into three equal groups;: rats subjected to I/R injury and treated with Chang Medium, rats subjected to I/R injury and treated with hAFSCs and sham-operated animals. In the first part of this study, hAFSCs that highly expressed CD24, CD117, SIX2 and PAX2 were isolated and characterized. In the second part, renal I/R injury was induced in male rats and cellular treatment was performed 6 hours later via arterial injection. Functional and histological analyses were performed 24 hours, 48 hours and 2 months after treatment using serum creatinine, urine protein to creatinine ratio, inflammatory and regeneration markers and histomorphometric analysis of the kidney. Statistical analysis was performed by analysis of variance followed by the Tukey’s test for multiple comparisons or by nonparametric Kruskal-Wallis followed by Dunn. Statistical significance level was defined as p <0.05.

Results

hAFSCs treatment resulted in significantly reduced serum creatinine level at 24 hours, less tubular necrosis, less hyaline cast formation, higher proliferation index, less inflammatory cell infiltration and less myofibroblasts at 48h. The treated group had less fibrosis and proteinuria at 2 months after injury.

Conclusion

hAFSCs contain a renal progenitor cell subpopulation that has a nephroprotective effect when delivered intra-arterially in rats with renal I/R injury, and reduces interstitial fibrosis on long term follow-up.

Inflammatory immune responses in a reproducible mouse brain death model

BACKGROUND

Brain death impairs donor organ quality and accelerates immune responses after transplantation. Detailed aspects of immune activation following brain death remain unclear. We have established a mouse model and investigated the immediate consequences of brain death and anesthesia on immune responses.

METHODS

C57JBl/6 mice (n=6/group) were anesthetized with isoflurane (ISF) or ketamine/xylazine (KX); subsequently, animals underwent brain death induction and were followed for 3h under continuous ventilation. Blood pressure was monitored continuously and animals were resuscitated with normal saline to achieve normotension. Immune activation in brain dead animals was analyzed by IFNγ-ELispot, MLR, and flow-cytometry. Sham-operated and naïve animals served as controls.

RESULTS

Blood pressure remained stable in both BD/KX and BD/ISF animals during the 3h observation time. Brain death was linked to systemic immune activation: IFNγ-expression of splenocytes and lymphocyte proliferation rates was significantly elevated subsequent to brain death (p<0.02, <0.01); T-cell activation markers CD28 and CD69 had increased in brain dead animals (p<0.03, <0.02). Isoflurane treatment in sham controls throughout the observation period (3.5h) revealed anesthesia associated IFNγ-expression and lymphocyte activation which were not observed when animals were treated with ketamine/xylazine (p<0.04, <0.009).

CONCLUSIONS

This study reports on a reproducible and hemodynamically stable brain death mouse model. Hemodynamic stability was not impacted through either isoflurane or ketamine/xylazine induction. Of clinical relevance, prolonged anesthesia with isoflurane had been linked to pro-inflammatory cytokine activation. Brain death caused systemic immune activation in organ donors.

Transplantation using hearts from primary pulmonary hypertensive donors for recipients with a high pulmonary vascular resistance

BACKGROUND

Transplantation for patients with a high pulmonary vascular resistance (PVR) carries an increased risk of mortality and right heart failure following heart transplantation and continues to be a major problem. We evaluated the use of hearts from patients who underwent heart and lung transplantation for primary pulmonary hypertension (PPH) as part of a domino procedure because these hearts have hypertrophied right ventricles used to increased pulmonary pressures, but could have a compromised left ventricle or irreversible damage of the right ventricle.

METHODS

We reviewed 12 patients with PVR >4 Wood units who underwent orthotopic heart transplantation between 1989 and 1998 using hearts from donors with PPH as part of a domino procedure.

RESULTS

We studied 10 men and 2 women, mean age 42.9 years. Mean PVR was 5.3 (range, 4-9) Wood units. Mean ischemia time was 85.3 minutes, and mean donor age was 32 years. Actuarial survival was 75% at 1 year and 75% at 5 years. In the early post-operative period, 3 patients had temporary arrhythmias, 2 required permanent pacemaker implantation, 1 had atrial fibrillation, and 1 had ventricular tachycardia that required defibrillator implantation. At a mean follow-up of 7.8 years, 2 patients had developed asymptomatic transplant coronary disease (both at 8.5 years after transplantation), 1 moderate and 1 very mild; the rest had none. Mean left ventricular ejection fraction at latest follow-up was 70.1% (range, 63%-78%). Right ventricular function assessed clinically and by echocardiography was adequate in the short and long term.

CONCLUSIONS

Our results suggest that heart and lung recipients with PPH can provide useful donor hearts to patients with increased PVR and that these hearts function well in the intermediate and long term.

Donor genomics influence graft events: the effect of donor polymorphisms on acute rejection and chronic allograft nephropathy

BACKGROUND

Organs procured from deceased donors emanate from individuals with diverse genetic backgrounds. Donor organs, therefore, may vary in their response to injury and immune stimuli in a genetically determined manner. We assessed polymorphisms from 244 renal allograft donors to better understand the impact of donor polymorphisms on selected transplant outcomes.

METHODS

Donor genomic DNA restriction fragment length polymorphisms were assayed for evidence of common cytokine [interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-alpha, TGF-beta, interferon (IFN)-gamma] and chemokine (CCR2, CCR5) polymorphisms. Associations between donor polymorphisms and graft events were determined using chi-square, linear regression, and Kaplan-Meier analyses.

RESULTS

Several genotypic polymorphisms demonstrated a modest association with acute rejection, including the transforming growth factor (TGF)-beta T/C codon 10 (P= 0.027) and the CCR5 G/A 59029 (P= 0.039) genes by chi-square analysis. Notably, the presence of the T allele in the IFN-gamma gene (+874) demonstrated a highly significant association with biopsy-proven chronic allograft nephropathy (P < 0.008). This association remained highly significant in a multiple linear regression model that incorporated biopsy-proven acute rejection as a covariate.

CONCLUSION

These data suggest that many of the donor polymorphisms studied in this analysis may influence a recipient's immune response to a renal allograft. However, their greatest impact may be demonstrated in long-term outcomes.

Natural History, Risk Factors, and Impact of Subclinical Rejection in Kidney Transplantation

BACKGROUND

Subclinical rejection (SCR) is defined as histologically proven acute rejection in the absence of immediate functional deterioration.

METHODS

We evaluated the impact of SCR in 961 prospective protocol kidney biopsies from diabetic recipients of a kidney-pancreas transplant (n=119) and one kidney transplant alone taken regularly up to 10 years after transplantation.

RESULTS

SCR was present in 60.8%, 45.7%, 25.8%, and 17.7% of biopsies at 1, 3, 12, and greater than 12 months after transplantation. Banff scores for acute interstitial inflammation and tubulitis declined exponentially with time. SCR was predicted by prior acute cellular rejection and type of immunosuppressive therapy (P<0.05-0.001). Tacrolimus reduced interstitial infiltration (P<0.001), whereas mycophenolate reduced tubulitis (P<0.05), and the combination effectively eliminated SCR (P<0.001). Persistent SCR of less than 2 years duration on sequential biopsies occurred in 29.2% of patients and was associated with prior acute interstitial rejection (P<0.001) and requirement for antilymphocyte therapy (P<0.05). It resolved by 0.49 +/- 0.33 years and resulted in higher grades of chronic allograft nephropathy (CAN, P<0.05). True chronic rejection, defined as persistent SCR of 2 years or more duration and implying continuous immunologic activation was found in only 5.8% of patients. The presence of SCR increased chronic interstitial fibrosis, tubular atrophy, and CAN scores on subsequent biopsies (P<0.05-0.001). SCR preceded and was correlated with CAN (P<0.001) on sequential analysis.

CONCLUSIONS

Histologic evidence of acute rejection in the absence of clinical suspicion resulted in significant tubulointerstitial damage to transplanted kidneys and contributed to CAN.

Brain death induces apoptosis in donor liver of the rat

BACKGROUND

A difference in short- and long-term function between living-related and cadaveric donor organs is consistently shown in kidney- and liver-transplant studies. We hypothesize that this is caused by induction of apoptosis and inflammation of the potential graft because of the phase of brain death (BD) in the cadaveric donor that predisposes for additional transplant injury. Previously, we have shown inflammation in the liver of brain-dead donors by increased expression of cell adhesion molecules and influx of leukocytes. The key inflammatory mediator in inflammation is tumor necrosis factor (TNF)-alpha. In addition to being involved in inflammation, TNF-alpha also activates the potential detrimental process of apoptosis and, on the other hand, activates an antiapoptotic survival pathway by way of NF-kB. The aim of the present study was to investigate whether the inflammatory response in the liver of brain-dead donors is accompanied by changes in apoptosis and in expression of apoptosis-related proteins, in particular those regulated by NF-kB.

METHODS

BD was induced by inflation of an intracranially placed balloon. Apoptosis was assessed by caspase-3 enzyme activity and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay. Changes in expression of proteins involved in pathways leading to apoptosis were studied by determination of mRNA levels using semiquantitative reverse-transcriptase polymerase chain reaction followed by image analysis. TNF-receptor (TNFR), Fas, and Fas-ligand (FasL) were used as indicators for activation of the death receptor mediated pathway. Bcl-2, Bax, Bak, Bid, and A1 were used as indicators for activation of the mitochondrial pathway.

RESULTS

After 6 hours of normotensive BD, the number of apoptotic cells and caspase-3 activity were significantly increased compared with non-brain-dead control rats. TUNEL staining revealed that the apoptotic cells were primarily hepatocytes. mRNA levels of all NF-kappaB induced activators (Fas, bid) and inhibitors (A1, BCl-xl, cIAP2) of both apoptotic pathways were significantly increased in liver tissue of BD donors versus non-BD controls.

CONCLUSIONS

The phase of BD in the donor induces increased apoptosis of hepatocytes despite an enhanced expression of NF-kB-dependent antiapoptotic genes.

Brain death significantly reduces isolated pancreatic islet yields and functionality in vitro and in vivo after transplantation in rats

Although approximately 1 million islets exist in the adult human pancreas, current pancreas preservation and islet isolation techniques recover <50%. Presently, cadaveric donors remain the sole source of pancreatic tissue for transplantation. Brain death is characterized by activation of proinflammatory cytokines and organ injury during preservation and reperfusion. In this study, we assessed the effects of brain death on islet isolation yields and functionality. Brain death was induced in male 250- to 350-g Lewis rats by inflation of a Fogarty catheter placed intracranially. The rats were mechanically ventilated for 2, 4, and 6 h before removal of the pancreas (n = 6). In controls, the catheter was not inflated (n = 6). Shortly after brain death induction, a significant increase in serum tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 was demonstrated in a time-dependent manner. Upregulation of TNF-alpha, IL-1beta, and IL-6 mRNA was noted in the pancreas. Brain death donors presented lower insulin release after glucose stimulation assessed by in situ perfusion of the pancreas. Islet recovery was reduced in brain death donors compared with controls (at 6 h 602.3 +/- 233.4 vs. 1,792.5 +/- 325.4 islet equivalents, respectively; P < 0.05). Islet viability assessed in dissociated islet cells and in intact cultured islets was reduced in islets recovered from brain death donors, an effect associated with higher nuclear activities of NF-kappaB p50, c-Jun, and ATF-2. Islet functionality evaluated in vitro by static incubation and in vivo after intraportal transplantation in syngeneic streptozotocin-induced diabetic rats was significantly reduced in preparations obtained from brain death donors. In conclusion, brain death significantly reduced islet yields and functionality. These observations may lead to strategies to reduce the effects of brain death on pancreatic islets and improve the results in clinical transplantation.