Chronic allograft nephropathy – a clinical syndrome: early detection and the potential role of proliferation signal inhibitors

The applications of DNA methylation as a biomarker in kidney transplantation: a systematic review

Background

Although kidney transplantation improves patient survival and quality of life, long-term results are hampered by both immune- and non-immune-mediated complications. Current biomarkers of post-transplant complications, such as allograft rejection, chronic renal allograft dysfunction, and cutaneous squamous cell carcinoma, have a suboptimal predictive value. DNA methylation is an epigenetic modification that directly affects gene expression and plays an important role in processes such as ischemia/reperfusion injury, fibrosis, and alloreactive immune response. Novel techniques can quickly assess the DNA methylation status of multiple loci in different cell types, allowing a deep and interesting study of cells’ activity and function. Therefore, DNA methylation has the potential to become an important biomarker for prediction and monitoring in kidney transplantation.

Purpose of the study

The aim of this study was to evaluate the role of DNA methylation as a potential biomarker of graft survival and complications development in kidney transplantation.

Material and Methods

A systematic review of several databases has been conducted. The Newcastle–Ottawa scale and the Jadad scale have been used to assess the risk of bias for observational and randomized studies, respectively.

Results

Twenty articles reporting on DNA methylation as a biomarker for kidney transplantation were included, all using DNA methylation for prediction and monitoring. DNA methylation pattern alterations in cells isolated from different tissues, such as kidney biopsies, urine, and blood, have been associated with ischemia–reperfusion injury and chronic renal allograft dysfunction. These alterations occurred in different and specific loci. DNA methylation status has also proved to be important for immune response modulation, having a crucial role in regulatory T cell definition and activity. Research also focused on a better understanding of the role of this epigenetic modification assessment for regulatory T cells isolation and expansion for future tolerance induction-oriented therapies.

Conclusions

Studies included in this review are heterogeneous in study design, biological samples, and outcome. More coordinated investigations are needed to affirm DNA methylation as a clinically relevant biomarker important for prevention, monitoring, and intervention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01241-7.

Suppression of Allograft Fibrosis by Regulation of Mammalian Target of Rapamycin-Related Protein Expression in Kidney-Transplanted Recipients Treated with Everolimus and Reduced Tacrolimus

Background

Although renoprotective effects of everolimus (EVR) in kidney transplantation (KTx) have been widely reported, its pathophysiological mechanism remains unclear.

Material/Methods

We compared changes in eGFR (ΔGFR, ml/min/1.73 m²) and the ratio of the fibrotic area in biopsy specimens (ΔFI,%) from 3 months to 3 years after KTx between the EVR+ group (EVR addition and Tac reduction early after KTx, n=32), and the EVR− group (normal Tac without EVR, n=28). We also immunohistochemically evaluated mTOR-related protein expression.

Results

ΔGFR and ΔFI in the EVR+ vs. EVR− groups were −0.27±6.8 vs. −9.8±12.8 (p<0.001) and 2.4±4.9 vs. 9.5±10.5 (p<0.001), respectively. Phosphorylated mTOR and phosphorylated 4EBP1 expression at 3 years in the EVR+ group was significantly lower than that in the EVR− group. Moreover, in the subgroup analysis comparing ΔGFR and ΔFI among groups stratified by immunosuppressive regimen and mTOR signal enhancement, the ΔFI in patients with EVR+ with decreased mTOR signal enhancement was significantly milder than that in other patients. In addition, in the multivariate analysis, EVR addition was the only independent predictor for allograft fibrosis, whereas the Tac C₀ concentration at neither 1 nor 3 years proved to be a risk factor.

Conclusions

These results suggested that EVR addition and Tac reduction may attenuate kidney allograft fibrosis, and that the suppression of mTOR signaling process may be involved in the anti-fibrotic effect of this immunosuppressive regimen. These results provide suggestions of how to utilize EVR for patients with KTx and improve graft function.

Unveiling the Role of DNA Methylation in Kidney Transplantation: Novel Perspectives toward Biomarker Identification

The burden of chronic kidney disease is dramatically rising, making it a major public health concern worldwide. Kidney transplantation is now the best treatment for patients with end-stage renal disease. Although kidney transplantation may improve survival and quality of life, its long-term results are hampered by immune- and/or non-immune-mediated complications. Thus, the identification of transplanted patients with a higher risk of posttransplant complications has become a big challenge for public health. However, current biomarkers of posttransplant complications have a poor predictive value, rising the need to explore novel approaches for the management of transplant patient. In this review we summarize the emerging literature about DNA methylation in kidney transplant complications, in order to highlight its perspectives toward biomarker identification. In the forthcoming future the monitoring of DNA methylation in kidney transplant patients could become a plausible strategy toward the prevention and/or treatment of kidney transplant complications.

Role of endothelial-to-mesenchymal transition induced by TGF-β1 in transplant kidney interstitial fibrosis

Chronic allograft dysfunction (CAD) induced by kidney interstitial fibrosis is the main cause of allograft failure in kidney transplantation. Endothelial‐to‐mesenchymal transition (EndMT) may play an important role in kidney fibrosis. We, therefore, undertook this study to characterize the functions and potential mechanism of EndMT in transplant kidney interstitial fibrosis. Proteins and mRNAs associated with EndMT were examined in human umbilical vein endothelial cells (HUVECs) treated with transforming growth factor‐beta1 (TGF‐β1) at different doses or at different intervals with western blotting, qRT‐PCR and ELISA assays. Cell motility and migration were evaluated with motility and migration assays. The mechanism of EndMT induced by TGF‐β1 was determined by western blotting analysis of factors involved in various canonical and non‐canonical pathways. In addition, human kidney tissues from control and CAD group were also examined for these proteins by HE, Masson's trichrome, immunohistochemical, indirect immunofluorescence double staining and western blotting assays. TGF‐β1 significantly promoted the development of EndMT in a time‐dependent and dose‐dependent manner and promoted the motility and migration ability of HUVECs. The TGF‐β/Smad and Akt/mTOR/p70S6K signalling pathways were found to be associated with the pathogenesis of EndMT induced by TGF‐β1, which was also proven in vivo by the analysis of specimens from the control and CAD groups. EndMT may promote transplant kidney interstitial fibrosis by targetting the TGF‐β/Smad and Akt/mTOR/p70S6K signalling pathways, and hence, result in the development of CAD in kidney transplant recipients.

Expression profile of mammalian target of rapamycin-related proteins in graft biopsy specimens: Significance for predicting interstitial fibrosis after kidney transplantation

OBJECTIVE

To investigate the influence of the expression profile of mammalian target of rapamycin-related proteins on the development of interstitial fibrosis after kidney transplantation.

METHODS

Immunohistochemical staining was carried out to evaluate the expression of five mammalian target of rapamycin-related proteins (phosphorylated-Akt, Ras homolog enriched in brain, phosphorylated-mammalian target of rapamycin, phosphorylated-p70 ribosomal S6 kinase and phosphorylated-4E binding protein 1) in graft biopsy specimens obtained from 77 patients at 3 months after kidney transplantation. The change of the estimated glomerular filtration rate and the change of the fibrosis index (defined as the change in the percent area of fibrosis on Masson's trichrome-stained sections of biopsy specimens) from 3 months to 3 years after kidney transplantation were determined.

RESULTS

There was a significant correlation between change of the estimated glomerular filtration and change of the fibrosis index in the 77 patients. Univariate analysis identified expression of phosphorylated-Akt, phosphorylated-mammalian target of rapamycin and phosphorylated-p70 ribosomal S6 kinase, as well as donor type and pre-transplant dialysis duration, as significant predictors of a change of the fibrosis index >10%. However, only phosphorylated-mammalian target of rapamycin expression, phosphorylated-p70 ribosomal S6 kinase expression and donor type were independently associated with a change of the fibrosis index >10% according to multivariate analysis.

CONCLUSIONS

These findings suggest that mammalian target of rapamycin-related proteins are involved in the development of interstitial fibrosis after kidney transplantation.

Increased Expression of p-Akt correlates with Chronic Allograft Nephropathy in a Rat Kidney Model

Chronic allograft nephropathy (CAN) is the most common cause of chronic graft dysfunction leading to graft failure, our study investigates the expression and significance of p-Akt in the pathogenesis of CAN in rats. Kidneys of Fisher (F344) rats were orthotopically transplanted into Lewis (LEW) rats. The animals were evaluated at 4, 8, 12, 16, and 24 weeks post-transplantation for renal function and histopathology. Phosphorate Akt (p-Akt) protein expression was determined by Western blot and immunohistological assays. Our data show that 24-h urinary protein excretion in CAN rats increased significantly at week 16 as compared with F344/LEW controls. Allografts got severe interstitial infiltration of mononuclear cells at week 4 and week 8, but it was degraded as the time went on after week 16. Allografts markedly presented with severe interstitial fibrosis (IF) and tubular atrophy at 16 and 24 weeks. p-Akt expression was upregulated in rat kidneys with CAN, and the increase became more significant over time after transplantation. p-Akt expression correlated significantly with 24-h urinary protein excretion, serum creatinine levels, tubulointerstitial mononuclear cells infiltration, smooth muscle cells (SMCs) migration in vascular wall, and IF. It was concluded that p-Akt overexpression might be the key event that involved mononuclear cells infiltration and vascular SMCs migration at early stage, and IF and allograft nephroangiosclerosis at the late stage of CAN pathogenesis in rats.

Epigenetics in Kidney Transplantation: Current Evidence, Predictions, and Future Research Directions

Epigenetic modifications are changes to the genome that occur without any alteration in DNA sequence. These changes include cytosine methylation of DNA at cytosine-phosphate diester-guanine dinucleotides, histone modifications, microRNA interactions, and chromatin remodeling complexes. Epigenetic modifications may exert their effect independently or complementary to genetic variants and have the potential to modify gene expression. These modifications are dynamic, potentially heritable, and can be induced by environmental stimuli or drugs. There is emerging evidence that epigenetics play an important role in health and disease. However, the impact of epigenetic modifications on the outcomes of kidney transplantation is currently poorly understood and deserves further exploration. Kidney transplantation is the best treatment option for end-stage renal disease, but allograft loss remains a significant challenge that leads to increased morbidity and return to dialysis. Epigenetic modifications may influence the activation, proliferation, and differentiation of the immune cells, and therefore may have a critical role in the host immune response to the allograft and its outcome. The epigenome of the donor may also impact kidney graft survival, especially those epigenetic modifications associated with early transplant stressors (e.g., cold ischemia time) and donor aging. In the present review, we discuss evidence supporting the role of epigenetic modifications in ischemia-reperfusion injury, host immune response to the graft, and graft response to injury as potential new tools for the diagnosis and prediction of graft function, and new therapeutic targets for improving outcomes of kidney transplantation.

Prevalence and risk factors for early chronic allograft nephropathy in a live related renal transplant program

BACKGROUND

Chronic allograft nephropathy (CAN) is a common cause of delayed allograft failure throughout the world. Its prevalence and risk factors vary depending on a number of factors. There is little information on the prevalence and risk factors for early CAN in live related renal transplant patients.

OBJECTIVES

We aimed to determine the prevalence and the risk factors of early CAN in our setup.

PATIENTS AND METHODS

The study was conducted at Sindh Institute of Urology & Transplantation (SIUT), Karachi, from 2002 to 2005 on patients who had live related kidney transplantation and underwent at least one allograft biopsy within 18 months of transplantation. The biopsies were performed and prepared in accordance with established indications and guidelines. The Banff 97 classification and its updates were used to diagnose and categorize the biopsy pathology. Patients were divided into two groups depending on the presence or absence of CAN on biopsies. Following parameters were compared among the groups: age, sex, human leukocyte antigen (HLA) match, immunosuppression used, acute rejection (AR) episodes, urinary tract infections (UTIs), viral infections, cyclosporine levels, early and late graft function monitored by serum creatinine.

RESULTS

A total of 164 patients fulfilled the study inclusion criteria. The mean age of recipients and donors was relatively young. The majority of the donors were siblings. The overall prevalence of CAN was 25.6% (42/164), between 3 and 18 months post transplantation. The median time to the appearance of CAN was 9 months post-transplant. The prevalence of CAN increased as post-transplant duration increased. In 39 (92.8%) subjects, CAN was detected on the second or subsequent graft biopsy. Only 3 (7.2%) patients showed CAN on the first graft biopsy. The majority of cases belonged to moderate degree or grade II CAN. The mean serum creatinine values were higher in the CAN group at the time of discharge and all times post-transplantation.

CONCLUSIONS

In conclusion, the results show that serum creatinine at the time of discharge is a useful predictor of later development of chronic changes in the allograft. Further studies are needed to identify the risk factors for the early development of chronic changes in living related renal transplant program.

Relationship between European mitochondrial haplogroups and chronic renal allograft rejection in patients with kidney transplant

Mitochondrial DNA variants may contribute to differences in mitochondrial function, leading to an altered immune system. The aim of this study was to analyze the relationship between mtDNA haplogroups and the development of chronic allograft dysfunction in patients with kidney transplant. A retrospective observational study was carried out on 261 patients who received kidney transplant (114 had stable transplant and 147 patients developed chronic allograft dysfunction). DNA samples were genotyped for 14 mtDNA polymorphisms by using Sequenom's MassARRAY platform (San Diego, CA, USA). Only European white patients within the N macro-cluster were included. Patients with haplogroups V (odds ratio (OR)=0.32; p=0.037) and J (OR=0.36; p=0.038) showed lower odds for developing CRAD than patients with haplogroup H. After adjusting for the most significant variables, haplogroups V and J tended to statistical significance (p=0.091 and p=0.067 respectively). This is a preliminary study in which mtDNA haplogroups seem to be implicated in susceptibility or protection for developing chronic allograft dysfunction.

Mycophenolate mofetil and FK506 have different effects on kidney allograft fibrosis in rats that underwent chronic allograft nephropathy

Background

Tacrolimus (FK506) is associated with renal fibrosis in long-term use. Mycophenolatemofetil (MMF) can also inhibit or attenuate the progression of renal fibrosis. This study aimed to determine the different effects of FK506 and MMF on fibrosis-associated genes in the kidney in rats that underwent chronic allograft nephropathy (CAN).

Methods

Fisher (F344) kidneys were orthotopically transplanted into Lewis rat recipients. All recipients were given Cyclosporin A (CsA) 10 mg/kg^-1.d^-1 × 10 day and were then randomly divided into three oral treatment groups (n = 9 in each group): (1) the vehicle group was given vehicle orally; (2) the FK506 group was given 0.15 mg/kg^-1.d^-1 FK506; and (3) the MMF group was given 20 mg/kg^-1.d^-1 MMF. At 4, 8, and 12 weeks post-transplantation, serum creatinine (SCr), collagen deposition, Connective tissue growth factor (CTGF), alpha smooth muscle actin (α-SMA) and E-cadherin expressions were determined and hematoxylin-eosin (HE) and Periodic acid-Schiff (PAS) stains were performed.

Results

Renal function progressively deteriorated and showed typical CAN morphology in the vehicle and FK506 groups, while SCr and inflammatory infiltration (Banff score) showed a significant decrease in the MMF group after 8 weeks post-transplantation compared with those in the other groups (p < 0.05). Furthermore, expression levels of CTGF and α-SMA in the MMF group were significantly reduced, and the down-regulated expression of E-cadherin was abated (p < 0.05).

Conclusions

MMF showed favorable effects on renal interstitial fibrosis, thus efficiently retarding the progression of CAN.

Genetic polymorphisms located in TGFB1, AGTR1, and VEGFA genes are associated to chronic renal allograft dysfunction

BACKGROUND

Persistent inflammation and fibrosis have been related to active progression of renal deterioration and reduced survival of kidney transplant. The aim of this study was to determine the impact of single-nucleotide polymorphisms (SNPs) located in regions related to inflammatory and immune processes on the development of chronic renal allograft dysfunction (CRAD).

METHODS

A retrospective study was carried out on 276 patients who received kidney transplant (KT). SNPs were genotyped via the SNPlex platform. Statistical analysis was performed with SNPstat and regression logistic analyses were adjusted by age and gender of recipients and donors, cold ischemia time and the number of human leukocyte antigen (HLA) mismatches.

RESULTS

From 276 patients with KT, 118 were non-CRAD and 158 were CRAD. Three SNPs showed significant associations with CRAD development: rs1800471 in transforming growth factor beta 1 (TGFB1), rs5186 in angiotensin II receptor type 1 (AGTR1), and rs699947 in vascular endothelial growth factor A (VEGFA). GC genotype of rs1800471 was associated with increased odds of CRAD compared to GG genotype (OR=2.65 (95% confidence interval (CI)=1.09; 6.47), p=0.025), as well as AC and AA genotype of rs699947 assuming a dominant model (OR=1.80 (95% CI=1.02; 3.20), p=0.044). Besides, AC and CC genotypes of rs5186 were associated with reduced odds of CRAD assuming a dominant model (OR=0.56 (95% CI=0.33; 0.96), p=0.033).

CONCLUSION

Our findings suggest that three genes related to immunity and inflammation (rs1800471, rs5186 and rs699947) are associated to susceptibility or protection to CRAD, and might have diagnostic utility in predicting the likelihood of developing CRAD.

Protective effects of SP600125 on renal ischemia-reperfusion injury in rats

BACKGROUND

Ischemia/reperfusion injury (IRI) has a negative effect on renal allograft survival. Using a rat model of kidney IRI in this study, we investigated the overall effect of selective c-Jun N-terminal kinase (JNK) inhibitor SP600125 on renal IRI events.

METHODS

All 45 Fisher rats were anesthetized and renal IRI model was established by 45 min clamp of bilateral renal pedicles and 24 h reperfusion. Vehicle solution or SP600125 solution was intraperitoneally injected 45 min before ischemia, respectively. Analysis of renal histology, function, reactive oxygen species (ROS) expression, JNK phosphorylation status, as well as intra-renal pro-inflammatory cytokines expression was evaluated in this study.

RESULTS

After IRI, the levels of blood urea nitrogen, creatinine, tissue malondialdehyde, TNF-α, IL-1β, IL-6 were all elevated significantly, while superoxide dismutase, catalase activity were decreased. Histologic findings showed severe devastating lesions and increased rodent cell apoptosis; SP600125 effectively improved morphologic features, reversed above-mentioned parameters, and significantly attenuated c-Jun phosphorylation, as well as intra-renal pro-inflammatory cytokines expression compared with vehicle-treated group.

CONCLUSION

These data demonstrate that inhibition of c-Jun with SP600125 is capable of attenuating renal IRI, which might be a novel therapy target.