Cellular senescence and renal transplantation

With the current crisis of organ shortage and an increasing number of dialysis patients,studies directed at ameliorating such a substantial organ discrepancy are of considerable importance to the transplant community. The use of extended criteria donation has helped to compensate the disparity of organs however, we are still a long way from achieving satisfactory targets. Still there are many organs from older donors that are discarded primarily on the basis of chronological age. It is here that biological age may display a crucial role in allowing the transplant team to characterize donor organs with greater accuracy. Indeed both biological and chronological age are very closely related and ECD criteria are based very much on the latter, albeit with other clinical variables. However the biomarker of ageing CDKN2A which is suitably represented by Baker and Sprott’s criteria, displays closer variabilities with post-operative transplant function, at least up to one year. Telomere length known as the “Gold standard” biomarker of ageing does not display as robust a role in predicting organ function as CDKN2A. The classification of organs represented in this text from category I-IV serves merely as a guide to future studies and is yet to be validated in larger clinical trials. It is however a simple and rapid assessment tool (Gingell-Littlejohn et al PLOS One 2013). Relatively advanced cellular senescence was displayed in the mutant AS/AGU rat kidney when compared to the parent AS strain. This was exploited in a unique animal model to study the effects of ischaemia reperfusion injury on the mutant kidney, hence mimicking to a certain degree the transplant related injuries in ECD kidneys. Although ischaemic times in the model were moderate in nature, there was nonetheless a difference in the tolerance to IR injury between parent and mutant strain as evidenced by increased p16 and p21 staining in AS/AGU rats. Such a model therefore is exclusive in that interventions to improve ECD renal function post-transplantation can accurately and conveniently be represented and studied at a pre-clinical level. Anti-ischaemic compounds have been the subject of much debate over the years, however a single “Holy Grail” compound able to completely abolish the injurious effects of IR injury has never been elicited. mTOR inhibitors however, display several cellular effects and act as potent immunosuppressants. They (AZ-6) have also been shown to partially mediate the detrimental effects of IR injury on the native kidneys of AS rats in a specifically designed animal model as shown. Further studies encompassing transplanted kidneys from mutant AS/AGU rats exposed to such a promising agent would be of undoubted importance to the clinical field of transplantation, potentially leading to immeasurable economic and patient benefits

Antegrade coeliac axis reconstruction for Chronic Mesenteric Ischaemia : a case series

The management of chronic mesenteric ischaemia remains a compelling challenge for many vascular surgeons. Over the past four decades, several reports have demonstrated encouraging results following revascularisation of the splanchnic arteries. To this date, due to limited numbers, there have been no randomized trials on which we can base our current practise. In this series, we have demonstrated the benefits of a left thoracoabdominal approach for performing an antegrade bypass graft to the coeliac axis, in patients with severe mesenteric angina. Its low complication rate and excellent aortic vessel exposure make it a procedure of choice in expert centres.peer-reviewe

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

Pre-transplant CDKN2A expression in kidney biopsies predicts renal function and is a future component of donor scoring criteria

CDKN2A is a proven and validated biomarker of ageing which acts as an off switch for cell proliferation. We have demonstrated previously that CDKN2A is the most robust and the strongest pre-transplant predictor of post- transplant serum creatinine when compared to “Gold Standard” clinical factors, such as cold ischaemic time and donor chronological age. This report shows that CDKN2A is better than telomere length, the most celebrated biomarker of ageing, as a predictor of post-transplant renal function. It also shows that CDKN2A is as strong a determinant of post-transplant organ function when compared to extended criteria (ECD) kidneys. A multivariate analysis model was able to predict up to 27.1% of eGFR at one year post-transplant (p = 0.008). Significantly, CDKN2A was also able to strongly predict delayed graft function. A pre-transplant donor risk classification system based on CDKN2A and ECD criteria is shown to be feasible and commendable for implementation in the near future

Two Stage Complex Embolization of an Arteriovenous Fistula between the Right Common Iliac Artery and the Inferior Vena Cava

<p>We  present an interesting case of a symptomatic high flow AV fistula between the right common iliac artery (CIA) and the inferior vena cava (IVC), successfully treated by endovascular coil embolization. The patient was found to have a right lower polar renal artery crossing the ipsilateral ureter arising from the CIA, causing pelvi-ureteric junction (PUJ) obstruction and recurrent pyelonephritis.  It is hypothesized that this fistula arising from the lower polar renal artery and entering the IVC, may have occurred as a result of trauma during a previous pyeloplasty, or a pathologically induced process of angiogenesis stemming from recurrent pyelonephritis.</p&gt

CDKN2A Expression in Pre-Implantation Kidney Biopsies is the Single, Strongest Predictive Factor for Post-Transplant Renal Function at 1 Year

Introduction: CDKN2A is a proven and validated biomarker of ageing (McGlynn LM et al, Aging Cell 2009 Feb;8(1):45-51; Koppelstaetter C et al, Aging Cell 2008 Aug;7(4):491-7) . It is responsible for inducing cell cycle arrest and as such can act as a tumour suppressor. In effect, it acts as an off switch for cell proliferation. We have demonstrated previously that CDKN2A is the most robust and the strongest predictor of post transplant renal function when compared to “Gold Standard” clinical factors such as ECD kidney status, DCD vs DBD kidneys and donor chronological age. We have sought to determine if CDKN2A is better than telomere length, the original biomarker of ageing, as predictor of post transplant renal function Methods: The Maxwell® 16 DNA purification robot kits by Promega were used for for DNA isolation and RNA was extracted using the TRIzol® technique. Real time qPCR was used for the expression of CDKN2A and to determine telomere length. Demographic and clinical data was collected prospectively in an electronic database (SERPR) and supplemented by clinical record review. Data was analysed for associations with renal function – MDRD4 eGFR and Urinary Protein/Creatinine Ratio (UPCR) using univariate and multiple linear regression analysis. Results: Univariate linear regression analysis showed that CDKN2A predicts 16.9% of eGFR (n=32, p=0.011) and 15.1% of the UPCR (n=25, p=0.031) at 1 year. ECD kidney status predicted 17.4% of eGFR (n=103, p=<0.001) but only 4.6% of the UPCR (n=85, p=0.027). Univariate linear regression between telomere length and renal function was not significant. A multivariate regression model comprising CDKN2A, ECD kidney status, donor chronological age and cold ischaemic time predicted 35.6% of the eGFR (n=31, p=0.003) and 44.4% of the UPCR (n=24, p=0.004) at 1 year. Discussion: This study confirms that measurement of CDKN2A is the strongest predictor of post transplant function when compared to current organ selection criteria. It indicates that telomere length is inferior to both CDKN2A and ECD kidney status. The model provides a valuable pre-transplant prognostic score on organ quality, allowing improved and objective patient counselling and providing the possibility for targeted intervention strategies to preserve graft function

MicroRNA Regulation of Cellular Bio-age Provides a Novel Pre-Transplant Prognostic and Predictive Assessment of Post Transplant Allograft Function

Background: Pre-transplant prediction of post-transplant renal function and outcome is extremely challenging, particularly when applied to older and marginal donor organs. We and others have demonstrated previously that allograft bio-age, as determined by CDKN2A expression level, is a superior prognostic and predictive marker for post transplant function. The CDKN2 locus is complex, comprising a series of developmentally and epigenetically regulated transcript isoforms. Transcriptional regulation of these isoforms incorporates a broad range of MicroRNAs (miRNA), non-coding, single-stranded RNA molecules that are involved in the regulation of a variety of biological processes, including embryogenesis, differentiation, and senescence. We have sought to investigate whether CDKN2 associated miRNAs expression profile in „zero hour‟ pre-transplant renal allograft biopsies are linked to clinico-pathological and functional characteristics post-transplant. Methods: MicroRNA profiles were determined in „zero hour‟ allograft biopsies using microfluidic TaqMan® MicroRNA arrays (Applied Biosystem) and were analysed in relation to clinical data including serum creatinine (SC), cold ischaemia time (CIT), donor age and acute rejection. Data were analysed using StatMiner® (Integromics). Furthermore, MicroRNA data were validated using individual assays. Results: 19miRNAs showed pre transplant expression levels that correlated with levels of SC at 6 months post-transplantation and CIT. Significantly, linear regression analyses in the cohort (n=43) revealed that pre-transplant expression of five miRNAs (hsa-miR-125b, hsa-miR-505, hsa-miR-125a-5p, hsa-miR-96 and hsa-miR-1275) were associated with acute rejection episodes (p<0.01).With the exception of hsa-miR-505, these miRNAs also demonstrated an association with CIT. Conclusions: This data indicates that miRNA profiling has clear potential to be used for pre transplant assessment of post transplant allograft function. It offers the potential for prediction of rejection episodes or other complications. Furthermore, there are also clear links with donor bio-age, which may further enhance the diagnostic possibilities

CDKN2A Expression in Pre-Implantation Kidney Biopsies is the Single, Strongest Predictive Factor for Post-Transplant Renal Function at 1 Year

Introduction: CDKN2A is a proven and validated biomarker of ageing (McGlynn LM et al, Aging Cell 2009 Feb;8(1):45-51; Koppelstaetter C et al, Aging Cell 2008 Aug;7(4):491-7) . It is responsible for inducing cell cycle arrest and as such can act as a tumour suppressor. In effect, it acts as an off switch for cell proliferation. We have demonstrated previously that CDKN2A is the most robust and the strongest predictor of post transplant renal function when compared to “Gold Standard” clinical factors such as ECD kidney status, DCD vs DBD kidneys and donor chronological age. We have sought to determine if CDKN2A is better than telomere length, the original biomarker of ageing, as predictor of post transplant renal function Methods: The Maxwell® 16 DNA purification robot kits by Promega were used for for DNA isolation and RNA was extracted using the TRIzol® technique. Real time qPCR was used for the expression of CDKN2A and to determine telomere length. Demographic and clinical data was collected prospectively in an electronic database (SERPR) and supplemented by clinical record review. Data was analysed for associations with renal function – MDRD4 eGFR and Urinary Protein/Creatinine Ratio (UPCR) using univariate and multiple linear regression analysis. Results: Univariate linear regression analysis showed that CDKN2A predicts 16.9% of eGFR (n=32, p=0.011) and 15.1% of the UPCR (n=25, p=0.031) at 1 year. ECD kidney status predicted 17.4% of eGFR (n=103, p=<0.001) but only 4.6% of the UPCR (n=85, p=0.027). Univariate linear regression between telomere length and renal function was not significant. A multivariate regression model comprising CDKN2A, ECD kidney status, donor chronological age and cold ischaemic time predicted 35.6% of the eGFR (n=31, p=0.003) and 44.4% of the UPCR (n=24, p=0.004) at 1 year. Discussion: This study confirms that measurement of CDKN2A is the strongest predictor of post transplant function when compared to current organ selection criteria. It indicates that telomere length is inferior to both CDKN2A and ECD kidney status. The model provides a valuable pre-transplant prognostic score on organ quality, allowing improved and objective patient counselling and providing the possibility for targeted intervention strategies to preserve graft function

MicroRNA Regulation of Cellular Bio-age Provides a Novel Pre-Transplant Prognostic and Predictive Assessment of Post Transplant Allograft Function

Background: Pre-transplant prediction of post-transplant renal function and outcome is extremely challenging, particularly when applied to older and marginal donor organs. We and others have demonstrated previously that allograft bio-age, as determined by CDKN2A expression level, is a superior prognostic and predictive marker for post transplant function. The CDKN2 locus is complex, comprising a series of developmentally and epigenetically regulated transcript isoforms. Transcriptional regulation of these isoforms incorporates a broad range of MicroRNAs (miRNA), non-coding, single-stranded RNA molecules that are involved in the regulation of a variety of biological processes, including embryogenesis, differentiation, and senescence. We have sought to investigate whether CDKN2 associated miRNAs expression profile in „zero hour‟ pre-transplant renal allograft biopsies are linked to clinico-pathological and functional characteristics post-transplant. Methods: MicroRNA profiles were determined in „zero hour‟ allograft biopsies using microfluidic TaqMan® MicroRNA arrays (Applied Biosystem) and were analysed in relation to clinical data including serum creatinine (SC), cold ischaemia time (CIT), donor age and acute rejection. Data were analysed using StatMiner® (Integromics). Furthermore, MicroRNA data were validated using individual assays. Results: 19miRNAs showed pre transplant expression levels that correlated with levels of SC at 6 months post-transplantation and CIT. Significantly, linear regression analyses in the cohort (n=43) revealed that pre-transplant expression of five miRNAs (hsa-miR-125b, hsa-miR-505, hsa-miR-125a-5p, hsa-miR-96 and hsa-miR-1275) were associated with acute rejection episodes (p<0.01).With the exception of hsa-miR-505, these miRNAs also demonstrated an association with CIT. Conclusions: This data indicates that miRNA profiling has clear potential to be used for pre transplant assessment of post transplant allograft function. It offers the potential for prediction of rejection episodes or other complications. Furthermore, there are also clear links with donor bio-age, which may further enhance the diagnostic possibilities

Multivariate model outcome for eGFR at 6 months.

<p>The model approaches statistical significance using the strict Bonferroni correction (p = 0.021).</p