High Intrapatient Tacrolimus Variability Is Associated With Worse Outcomes in Renal Transplantation Using a Low-Dose Tacrolimus Immunosuppressive Regime.

BACKGROUND: High intrapatient tacrolimus variability has been associated with worse clinical outcomes postrenal transplantation. Theoretically, tacrolimus levels consistently outside the target therapeutic window may result in allograft dysfunction as subtherapeutic tacrolimus levels predispose to episodes of acute rejection, whereas supratherapeutic levels may cause nephrotoxicity. METHODS: We investigated the effect of tacrolimus variability in a "Symphony" style low-dose tacrolimus based regime, by collecting data from 432 patients over a 4-year period.Three hundred seventy-six patients were included, with a mean follow-up of 1495 days. Tacrolimus variability 6 to 12 months after renal transplantation was calculated, and outcomes were compared in low (n = 186) and high variability (n = 190) groups. RESULTS: High variability patients were found to be at increased risk of rejection during the first posttransplant year (P = 0.0054) and to have reduced rejection-free survival (hazard ratio, 1.953; 95% confidence interval, 1.234-3.093; P = 0.0054). High variability patients had significantly worse (P < 0.0001) glomerular filtration rates at 1, 2, 3, and 4 years posttransplant. High variability patients were at increased risk of allograft loss (hazard ratio, 4.928; 95% confidence interval, 2.050-11.85; P = 0.0004). CONCLUSIONS: This suggests that highly variable tacrolimus levels predict worse outcomes postrenal transplantation, although the causal nature of this relationship remains unclear. High tacrolimus variability may identify a subset of patients who warrant increased surveillance and patient education regarding dietary and medication compliance.

A novel rodent model of severe renal ischemia reperfusion injury.

Renal ischemia reperfusion injury (IRI) is a major problem, currently without treatments in clinical use. This reflects the failure of animal models to mimic the severity of IRI observed in clinical practice. Most described models lack both the ability to inflict a permanent reduction in renal function and the sensitivity to demonstrate the protective efficacy of different therapies in vivo. To test novel cell-based therapies, we have developed a model of renal IRI in Fisher 344 rats. Animals were subjected to 120 min of unilateral warm ischemia, during which they underwent an intra-renal artery infusion of therapeutic agents or vehicle. At either 2 or 6 weeks post-surgery, animals underwent terminal glomerular filtration rate (GFR) studies by inulin clearance to most accurately quantify renal function. Harvested kidneys underwent histological analysis. Compared to sham operations, saline treated animals suffered a long-term reduction in GFR of ≈50%. Histology revealed short- and long-term disruption of renal architecture. Despite the injury severity, post-operative animal losses are <5%. This model produces a severe, consistent renal injury that closely replicates the pathological processes encountered in clinical medicine. Renal artery infusion mimics the route likely employed in clinical transplantation, where the renal artery is accessible. Inulin clearance characterizes GFR, allowing full assessment of therapeutic intervention. This model is useful for screening therapeutic agents prior to testing in a transplant model. This reduces animal numbers needed to test drugs for clinical transplantation and allows for refinement of dosing schedules.

Identification of Molecular Markers of Delayed Graft Function Based on the Regulation of Biological Ageing.

INTRODUCTION: Delayed graft function is a prevalent clinical problem in renal transplantation for which there is no objective system to predict occurrence in advance. It can result in a significant increase in the necessity for hospitalisation post-transplant and is a significant risk factor for other post-transplant complications. METHODOLOGY: The importance of microRNAs (miRNAs), a specific subclass of small RNA, have been clearly demonstrated to influence many pathways in health and disease. To investigate the influence of miRNAs on renal allograft performance post-transplant, the expression of a panel of miRNAs in pre-transplant renal biopsies was measured using qPCR. Expression was then related to clinical parameters and outcomes in two independent renal transplant cohorts. RESULTS: Here we demonstrate, in two independent cohorts of pre-implantation human renal allograft biopsies, that a novel pre-transplant renal performance scoring system (GRPSS), can determine the occurrence of DGF with a high sensitivity (>90%) and specificity (>60%) for donor allografts pre-transplant, using just three senescence associated microRNAs combined with donor age and type of organ donation. CONCLUSION: These results demonstrate a relationship between pre-transplant microRNA expression levels, cellular biological ageing pathways and clinical outcomes for renal transplantation. They provide for a simple, rapid quantitative molecular pre-transplant assay to determine post-transplant allograft function and scope for future intervention. Furthermore, these results demonstrate the involvement of senescence pathways in ischaemic injury during the organ transplantation process and an indication of accelerated bio-ageing as a consequence of both warm and cold ischaemia.

Impaired gluconeogenesis in a porcine model of paracetamol induced acute liver failure.

AIM: To investigate glucose homeostasis and in particular gluconeogenesis in a large animal model of acute liver failure (ALF). METHODS: Six pigs with paracetamol induced ALF under general anaesthesia were studied over 25 h. Plasma samples were withdrawn every five hours from a central vein. Three animals were used as controls and were maintained under anaesthesia only. Using (1)H NMR spectroscopy we identified most gluconeogenic amino acids along with lactate and pyruvate in the animal plasma samples. RESULTS: No significant changes were observed in the concentrations of the amino acids studied in the animals maintained under anaesthesia only. If we look at the ALF animals, we observed a statistically significant rise of lactate (P < 0.003) and pyruvate (P < 0.018) at the end of the experiments. We also observed statistically significant rises in the concentrations of alanine (P < 0.002), glycine (P < 0.005), threonine (P < 0.048), tyrosine (P < 0.000), phenylalanine (P < 0.000) and isoleucine (P < 0.01). Valine levels decreased significantly (P < 0.05). CONCLUSION: Our pig model of ALF is characterized by an altered gluconeogenetic capacity, an impaired tricarboxylic acid (TCA) cycle and a glycolytic state.

Endo-biliary stents for benign disease: not always benign after all!

This case report describes the presentation, management and treatment of a patient who suffered small bowel perforation due to the migration of his biliary stent which had been inserted for benign disease.

Aortic valve replacement following coronary artery bypass grafting using bilateral internal mammary arteries.

Aortic valve replacement in patients with a patent internal mammary artery grafts poses two main challenges: Sternal reentry and myocardial protection. Beating heart procedures have been well described in coronary and valve surgery. Herein, we describe a simple reproducible technique of aortic valve replacement that circumvents the main issues highlighted above.