Evaluation of gene panel mRNAs in urine samples of kidney transplant recipients as a non-invasive tool of graft function

The role of CD47 in pathogenesis and treatment of renal ischemia reperfusion injury

Ischemia reperfusion (IR) injury is a process defined by the temporary loss of blood flow and tissue perfusion followed later by restoration of the same. Brief periods of IR can be tolerated with little permanent deficit, but sensitivity varies for different target cells and tissues. Ischemia reperfusion injuries have multiple causes including peripheral vascular disease and surgical interventions that disrupt soft tissue and organ perfusion as occurs in general and reconstructive surgery. Ischemia reperfusion injury is especially prominent in organ transplantation where substantial effort has been focused on protecting the transplanted organ from the consequences of IR. A number of factors mediate IR injury including the production of reactive oxygen species and inflammatory cell infiltration and activation. In the kidney, IR injury is a major cause of acute injury and secondary loss of renal function. Transplant-initiated renal IR is also a stimulus for innate and adaptive immune-mediated transplant dysfunction. The cell surface molecule CD47 negatively modulates cell and tissue responses to stress through limitation of specific homeostatic pathways and initiation of cell death pathways. Herein, a summary of the maladaptive activities of renal CD47 will be considered as well as the possible therapeutic benefit of interfering with CD47 to limit renal IR.

Human expression patterns: qualitative and quantitative analysis of thrombospondin-1 under physiological and pathological conditions

Thrombospondin-1 (TSP-1), a matricellular protein and one of the first endogenous anti-angiogenic molecules identified, has long been considered a potent modulator of human diseases. While the therapeutic effect of TSP-1 to suppress cancer was investigated in both research and clinical settings, the mechanisms of how TSP-1 is regulated in cancer remain elusive, and the scientific answers to the question of whether TSP-1 expressions can be utilized as diagnostic or prognostic marker for patients with cancer are largely inconsistent. Moreover, TSP-1 plays crucial functions in angiogenesis, inflammation and tissue remodelling, which are essential biological processes in the progression of many cardiovascular diseases, and therefore, its dysregulated expressions in such conditions may have therapeutic significance. Herein, we critically analysed the literature pertaining to TSP-1 expression in circulating blood and pathological tissues in various types of cancer as well as cardiovascular and inflammation-related diseases in humans. We compare the secretion rates of TSP-1 by different cancer and non-cancer cells and discuss the potential connection between the expression changes of TSP-1 and vascular endothelial growth factor (VEGF) observed in patients with cancer. Moreover, the pattern and emerging significance of TSP-1 profiles in cardiovascular disease, such as peripheral arterial disease, diabetes and other related non-cancer disorders, are highlighted. The analysis of published TSP-1 data presented in this review may have implications for the future exploration of novel TSP-1-based treatment strategies for cancer and cardiovascular-related diseases.

A New Data Analysis System to Quantify Associations between Biochemical Parameters of Chronic Kidney Disease-Mineral Bone Disease

BACKGROUND

In hemodialysis patients, deviations from KDIGO recommended values of individual parameters, phosphate, calcium or parathyroid hormone (PTH), are associated with increased mortality. However, it is widely accepted that these parameters are not regulated independently of each other and that therapy aimed to correct one parameter often modifies the others. The aim of the present study is to quantify the degree of association between parameters of chronic kidney disease and mineral bone disease (CKD-MBD).

METHODS

Data was extracted from a cohort of 1758 adult HD patients between January 2000 and June 2013 obtaining a total of 46.141 records (10 year follow-up). We used an advanced data analysis system called Random Forest (RF) which is based on self-learning procedure with similar axioms to those utilized for the development of artificial intelligence. This new approach is particularly useful when the variables analyzed are closely dependent to each other.

RESULTS

The analysis revealed a strong association between PTH and phosphate that was superior to that of PTH and Calcium. The classical linear regression analysis between PTH and phosphate shows a correlation coefficient is 0.27, p<0.001, the possibility to predict PTH changes from phosphate modification is marginal. Alternatively, RF assumes that changes in phosphate will cause modifications in other associated variables (calcium and others) that may also affect PTH values. Using RF the correlation coefficient between changes in serum PTH and phosphate is 0.77, p<0.001; thus, the power of prediction is markedly increased. The effect of therapy on biochemical variables was also analyzed using this RF.

CONCLUSION

Our results suggest that the analysis of the complex interactions between mineral metabolism parameters in CKD-MBD may demand a more advanced data analysis system such as RF.

The urine microRNA profile may help monitor post-transplant renal graft function

Noninvasive, cost-effective biomarkers that allow accurate monitoring of graft function are needed in kidney transplantation. Since microRNAs (miRNAs) have emerged as promising disease biomarkers, we sought to establish an miRNA signature in urinary cell pellets comparing kidney transplant patients diagnosed with chronic allograft dysfunction (CAD) with interstitial fibrosis and tubular atrophy and those recipients with normal graft function. Overall, we evaluated 191 samples from 125 deceased donor primary kidney transplant recipients in the discovery, initial validation, and the longitudinal validation studies for noninvasive monitoring of graft function. Of 1733 mature miRNAs studied using microarrays, 22 were found to be differentially expressed between groups. Ontology and pathway analyses showed inflammation as the principal biological function associated with these miRNAs. Twelve selected miRNAs were longitudinally evaluated in urine samples of an independent set of 66 patients, at two time points after kidney transplant. A subset of these miRNAs was found to be differentially expressed between groups early after kidney transplant before histological allograft injury was evident. Thus, a panel of urine miRNAs was identified as potential biomarkers for monitoring graft function and anticipating progression to CAD in kidney transplant patients.

Multicenter evaluation of a standardized protocol for noninvasive gene expression profiling

Gene expression profiling of transplant recipient blood and urine can potentially be used to monitor graft function, but the multitude of protocols in use make sharing data and comparing results from different laboratories difficult. The goal of this study was to evaluate the performance of current methods of RNA isolation, reverse transcription and quantitative polymerase chain reaction (qPCR) and to test whether multiple centers using a standardized protocol can obtain the same results. Samples, reagents and detailed instructions were distributed to six participating sites that performed RNA isolation, reverse transcription and qPCR for 18S, PRF, GZB, IL8, CXCL9 and CXCL10 as instructed. All data were analyzed at a single site. All sites demonstrated proficiency in RNA isolation and qPCR analysis. Gene expression measurements for all targets and samples had correlations >0.938. The coefficient of variation of fold-changes between pairs of samples was less than 40%. All sites were able to accurately quantify a control sample of known concentration within a factor of 1.5. Collectively, we have formulated and validated detailed methods for measuring gene expression in blood and urine that can yield consistent results in multiple laboratories.

Kidney transplantation: analysis of the expression and T cell-mediated activation of latent TGF-β

T cells activate latent TGF-β by an LSKL peptide-sensitive mechanism, suggesting a role for thrombospondin-1 in T cell differentiation after kidney transplantation.

Activated T cells infiltrate a renal allograft during rejection and can respond to TGF-β within the tubules, causing local differentiation and expression of the αE(CD103)β7 integrin. This study was performed to examine the expression of latent TGF-β within renal allograft tissues and to define a mechanism by which T cells can activate and respond to this latent factor. Rejecting renal allograft biopsy tissues showed increased expression of the latent TGF-β complex, which was localized around the tubules by a mechanism that might involve interaction with heparan sulfate in the basement membrane. A cultured renal TEC line also expressed the latent complex, but these cells did not respond to this form of TGF-β by pSmad 3. However, coculture of these cells with activated T cells induced the expression of CD103, suggesting that T cells can activate and respond to the latent TGF-β associated with TEC. Although activated T cells expressed little cell-surface TSP-1, this was increased by culture with fibronectin or fibronectin-expressing renal TEC. Blockade of TSP-1 using LSKL peptides reduced the potential of activated T cells to differentiate in response to latent TGF-β. This study suggests that penetration of renal tubules by activated T cells leads to increased expression of T cell-surface TSP-1, allowing activation of latent TGF-β sequestered on heparan sulfate within the microenvironment. This mechanism may be important for localized phenotypic maturation of T cells that have infiltrated the kidney during allograft rejection.

Identifying biomarkers as diagnostic tools in kidney transplantation

There is a critical need for biomarkers for early diagnosis, treatment response, and surrogate end point and outcome prediction in organ transplantation, leading to a tailored and individualized treatment. Genomic and proteomic platforms have provided multiple promising new biomarkers during the last few years. However, there is still no routine application of any of these markers in clinical transplantation. This article will discuss the existing gap between biomarker discovery and clinical application in the kidney transplant setting. Approaches to implementing biomarker monitoring into clinical practice will also be discussed.

Molecular pathways involved in loss of graft function in kidney transplant recipients

Interstitial fibrosis (IF) and tubular atrophy (TA) are integral parts of chronic allograft dysfunction and represent in the new classification a separate entity with or without the identification of a specific etiology. Loss of kidney graft function with IF/TA is one of the causes of most kidney allograft losses. Despite progress in immunosuppression, chronic allograft dysfunction remains the main clinical challenge for improving long-term graft survival. The sustained damage to the allograft does not represent a single entity but the summated effects of tissue injury from several pathogenic insults, as well as the kidney's healing response, modified by alloimmunity and immunosuppression. A major challenge in the future of kidney transplantation includes the study of chronic allograft dysfunction pathogenesis to identify early markers of disease progression, as well as potential therapeutics pathways.

Noninvasive prediction of organ graft rejection and outcome using gene expression patterns

Development of predictive, diagnostic, and prognostic biomarkers of allograft status and outcome is important and challenging, and may be rewarded with individualized therapy for the organ graft recipient. Herein, we summarize noninvasive messenger RNA profiling studies for ascertaining allograft status and outcome. Nucleic acid-based biomarkers of allograft status have been developed by several laboratories, but the studies have primarily been single center investigations. Ongoing multicenter trials including the Clinical Trials in Organ Transplantation (https://www.ctotstudies.org) should help further to define the clinical utility of noninvasively developed messenger RNA profiles as biomarkers of allograft status and outcome.