Factors increasing quantitative interstitial fibrosis from 0 hr to 1 year in living kidney transplant patients receiving tacrolimus

The pharmacogenetics of tacrolimus in renal transplant patients: association with tremors, new-onset diabetes and other clinical events

Our study is the first study to investigate the effect of SNPs in CYP3A5, CYP3A4, ABCB1 and POR genes on the incidence of tremors, nephrotoxicity, and diabetes mellitus. A total of 223 renal transplant patients receiving tacrolimus and mycophenolate mofetil (MMF) were recruited. Both adults and children patients participated in the study. Genotyping was performed using PROFLEX-PCR followed by RFLP. MPA and tacrolimus plasma concentrations were measured by immunoassay. The AUC0-12h of MMF was estimated by a Bayesian method. We found a statistically significant association between the CYP3A5*3 and CYP3A4*1B genotypes and the tacrolimus exposure. We found a lower occurrence of nephrotoxicity (p = 0.03), tremor (p = 0.01), and new-onset diabetes (p = 0.002) associated with CYP3A5*1 allele. The CYP3A4*1B allele was significantly associated with a lower occurrence of new-onset diabetes (p = 0.026). The CYP3A5*1 allele was significantly associated with an increased risk of acute and chronic rejection (p = 0.03 and p < 0.001, respectively). Our results support the usefulness of tacrolimus pharmacokinetics in pre-kidney transplant assessments.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

One-year Outcome of Everolimus With Standard-dose Tacrolimus Immunosuppression in De Novo ABO-incompatible Living Donor Kidney Transplantation: A Retrospective, Single-center, Propensity Score Matching Comparison With Mycophenolate in 42 Transplants

Background.

Despite improvement in immunosuppressive therapy, long-term kidney allograft survival remains a major challenge. The outcomes of therapy with everolimus (EVR) and standard-dose tacrolimus (Tac) have not been compared with those of mycophenolate mofetil (MMF) and standard-dose Tac in recipients of de novo ABO-incompatible (ABOi) living donor kidney transplantation (LDKT).

Methods.

This retrospective, observational, single-center, propensity score matching (PSM) study compared the outcomes of EVR and standard-dose Tac with those of MMF and standard-dose Tac following de novo ABOi LDKT. In total, 153 recipients of ABOi LDKT between January 2008 and March 2018 were screened for inclusion in the study. The variables considered for PSM were: recipient age/sex, duration of dialysis, cytomegalovirus mismatch (seronegative recipient and seropositive donor), cause of kidney disease, donor age/sex, and numbers of mismatches (HLA-A, HLA-B, and HLA-DR). After PSM, there were 21 patients in each group (n = 42 overall).

Results.

Four patients in the EVR group and 1 patient in the MMF group were withdrawn because of adverse effects. There were no significant differences between the 2 groups in 1-year outcomes regarding patient death, graft loss, delayed graft function, biopsy-proven acute rejection, infection requiring hospital admission, or estimated glomerular filtration rate. The 1-year protocol biopsy showed that the severity of interstitial fibrosis/tubular atrophy was significantly milder in the EVR group than in the MMF group.

Conclusions.

The findings suggest that the renal efficacy and safety of EVR and standard-dose Tac in recipients of de novo ABOi LDKT are comparable with those of MMF and standard-dose Tac.

The Landscape of Digital Pathology in Transplantation: From the Beginning to the Virtual E-Slide

Background

Digital pathology has progressed over the last two decades, with many clinical and nonclinical applications. Transplantation pathology is a highly specialized field in which the majority of practicing pathologists do not have sufficient expertise to handle critical needs. In this context, digital pathology has proven to be useful as it allows for timely access to expert second-opinion teleconsultation. The aim of this study was to review the experience of the application of digital pathology to the field of transplantation.

Methods

Papers on this topic were retrieved using PubMed as a search engine. Inclusion criteria were the presence of transplantation setting and the use of any type of digital image with or without the use of image analysis tools; the search was restricted to English language papers published in the 25 years until December 31, 2018.

Results

Literature regarding digital transplant pathology is mostly about the digital interpretation of posttransplant biopsies (75 vs. 19), with 15/75 (20%) articles focusing on agreement/reproducibility. Several papers concentrated on the correlation between biopsy features assessed by digital image analysis (DIA) and clinical outcome (45/75, 60%). Whole-slide imaging (WSI) only appeared in recent publications, starting from 2011 (13/75, 17.3%). Papers dealing with preimplantation biopsy are less numerous, the majority (13/19, 68.4%) of which focus on diagnostic agreement between digital microscopy and light microscopy (LM), with WSI technology being used in only a small quota of papers (4/19, 21.1%).

Conclusions

Overall, published studies show good concordance between digital microscopy and LM modalities for diagnosis. DIA has the potential to increase diagnostic reproducibility and facilitate the identification and quantification of histological parameters. Thus, with advancing technology such as faster scanning times, better image resolution, and novel image algorithms, it is likely that WSI will eventually replace LM.

Influence of CYP3A5 genetic differences in tacrolimus on quantitative interstitial fibrosis and long-term graft function in kidney transplant recipients

The impact of CYP3A5 polymorphisms on clinical outcomes is controversial. The present study investigated the impact of CYP3A5 genetic differences on the development of interstitial fibrosis (IF) from 0 h to 1 year post-transplantation in biopsy sections from 96 living kidney recipients under the same target trough regimen of tacrolimus. The relationships between CYP3A5 polymorphisms and long-term graft function and death-censored graft survival were also examined. A quantitative analysis of IF was performed using computer-assisted imaging on virtual slides. Percent IF (%IF) in the cortical region at 0 h was defined as the baseline, and increases in the ratio of %IF 1 year post-transplantation were calculated. The relationships between CYP3A5 genetic differences and the development of IF, the incidence of clinical events, and the long-term function and death-censored survival of grafts were assessed. The mean increase in the ratio of %IF from 0 h to 1 year was 1.38 ± 0.74-fold. Despite therapeutic drug monitoring (TDM), trough levels of tacrolimus were lower in carriers with the CYP3A5*1 allele (expressers) than in those with the CTP3A5*3/*3 genotype (non-expressers) throughout the 1-year post-transplantation period. However, CYP3A5 genetic differences were not associated with the development of IF, any clinical events, or the long-term function and survival of grafts. The clinical impact of CYP3A5 genetic differences may be small under the current immunosuppressive regimen consisting of mycophenolate mofetil, steroids, basiliximab, and lower target trough levels of tacrolimus with suitable TDM in a low immunological risk population.

Quantification of Interstitial Fibrosis in Renal Allografts and Clinical Correlates of Long-Term Graft Function

BACKGROUND

The present study investigated interstitial fibrosis (IF) in 144 kidney recipients 0 h and 1 year post transplantation and assessed relationships with Banff code scores, clinical parameters, and long-term graft function.

METHODS

A quantitative analysis of IF was performed using the computer-assisted imaging of Sirius red-stained biopsy samples. Percent IF (%IF) in the cortical region was assessed at 0 h and 1 year, and an increase in the ratio of %IF from 0 h to 1 year was calculated. The relationship between %IF and Banff code scores was analyzed. Demographics and trough concentrations of tacrolimus were tested as risk factors in the top 20 patients with increases in %IF. The influence of increases in the ratio of %IF at 1 year on long-term graft function and survival was also assessed in these 20 patients.

RESULTS

Median %IF at 0 h and 1 year were 1.55 and 2.80%, respectively. No correlation was found between %IF and Banff code scores. The mean increase in the ratio of %IF from 0 h to 1 year was 4.31-fold. The increase in %IF in the top 20 patients correlated with diabetes mellitus. Graft function, but not graft survival, was lower in the top 20 patients for 10 years post transplantation.

CONCLUSIONS

A correlation was not found between %IF and Banff code scores. Greater increases in %IF within 1 year post transplantation may influence long-term graft survival. Computer-analyzed increases in %IF at 1 year may be a surrogate marker for long-term graft function.

Circulating TNF receptors 1 and 2 are associated with the severity of renal interstitial fibrosis in IgA nephropathy

The current study aimed to examine whether the levels of TNF receptors 1 and 2 (TNFR1 and TNFR2) in serum and urine were associated with other markers of kidney injury and renal histological findings, including TNFR expression, in IgA nephropathy (IgAN). The levels of the parameters of interest were measured by immunoassay in 106 biopsy-proven IgAN patients using samples obtained immediately before renal biopsy and in 34 healthy subjects. Renal histological findings were evaluated using immunohistochemistry. The levels of serum TNFRs were higher in IgAN patients than in healthy subjects. The levels of both TNFRs in serum or urine were strongly correlated with each other (r > 0.9). Serum TNFR levels were positively correlated with the urinary protein to creatinine ratio (UPCR) and four markers of tubular damage of interest (N-acetyl-β-D-glucosaminidase [NAG], β2 microglobulin [β2m], liver-type fatty acid-binding protein [L-FABP], and kidney injury molecule-1 [KIM-1]) and negatively correlated with estimated glomerular filtration rate (eGFR). Patients in the highest tertile of serum TNFR levels showed more severe renal interstitial fibrosis than did those in the lowest or second tertiles. The tubulointerstitial TNFR2-, but not TNFR1-, positive area was significantly correlated with the serum levels of TNFRs and eGFR. Stepwise multiple regression analysis revealed that elevated serum TNFR1 or TNFR2 levels were a significant determinant of renal interstitial fibrosis after adjusting for eGFR, UPCR, and other markers of tubular damage. In conclusion, elevated serum TNFR levels were significantly associated with the severity of renal interstitial fibrosis in IgAN patients. However, the source of TNFRs in serum and urine remains unclear.

Characterization of clinical and genetic risk factors associated with dyslipidemia after kidney transplantation

We determined the prevalence of dyslipidemia in a Japanese cohort of renal allograft recipients and investigated clinical and genetic characteristics associated with having the disease. In total, 126 patients that received renal allograft transplants between February 2002 and August 2011 were studied, of which 44 recipients (34.9%) were diagnosed with dyslipidemia at 1 year after transplantation. Three clinical factors were associated with a risk of having dyslipidemia: a higher prevalence of disease observed among female than male patients (P = 0.021) and treatment with high mycophenolate mofetil (P = 0.012) and prednisolone (P = 0.023) doses per body weight at 28 days after transplantation. The genetic association between dyslipidemia and 60 previously described genetic polymorphisms in 38 putative disease-associated genes was analyzed. The frequency of dyslipidemia was significantly higher in patients with the glucocorticoid receptor (NR3C1) Bcl1 G allele than in those with the CC genotype (P = 0.001). A multivariate analysis revealed that the NR3C1 Bcl1 G allele was a significant risk factor for the prevalence of dyslipidemia (odds ratio = 4.6; 95% confidence interval = 1.8–12.2). These findings may aid in predicting a patient's risk of developing dyslipidemia.

What is the best way to measure renal fibrosis?: A pathologist's perspective

Interstitial fibrosis is a hallmark structural correlate of progressive and chronic kidney disease. There remain many uncertainties about how to best measure interstitial fibrosis both in research settings and in evaluations of renal biopsies performed for management of individual patients. Areas of uncertainty include determination of the composition of the matrix in a fibrotic parenchyma, the definition of how the interstitium is involved by fibrosing injuries, the choice of histologic stains for evaluation of renal fibrosis, and the reproducibility and robustness of measures currently employed by pathologists, both with and without the assistance of computerized imaging and assessments. In this review, we address some of these issues while citing the key studies that illustrate these difficulties. We point to future approaches that may allow a more accurate and meaningful assessment of renal interstitial fibrosis.

Pharmacokinetic and CYP3A5 pharmacogenetic differences between once- and twice-daily tacrolimus from the first dosing day to 1 year after renal transplantation

Aim & patients & methods: This study investigated 24-h pharmacokinetic and CYP3A5 pharmacogenetic differences between once-daily tacrolimus (Tac-q.d.) versus twice-daily tacrolimus (Tac-b.i.d.) pretransplantation and at 1 month and 1 year post-transplantaion. Results: The dose-adjusted trough level (Cmin) and area under the blood concentration–time curve from 0 to 24 h (AUC0–24) increased twofold within 1 year post-transplantation with both formulations and the two genotypes. Good correlations were observed between the AUC0–24 and Cmin for both formulations. However, the dose-adjusted Cmin, but not dose-adjusted AUC0–24, was approximately 30% lower for Tac-q.d. than for Tac-b.i.d. Although the dose-adjusted Cmin was lower for Tac-q.d. than for Tac-b.i.d. in both genotypes, the dose-adjusted AUC0–24 was approximately 25% lower for Tac-q.d. than for Tac-b.i.d. in CYP3A5 expressers, but not in nonexpressers during the study period. Conclusion: These results suggested that the approximately 30% lower Cmin for Tac-q.d. than for Tac-b.i.d. may have achieved the same AUC0–24 with both formulations and may be associated with CYP3A5 pharmacogenomic differences, especially in CYP3A5 expressers, between Tac-b.i.d. and Tac-q.d.

Original submitted 3 May 2013; Revision submitted 11 June 2014

Banff fibrosis study: multicenter visual assessment and computerized analysis of interstitial fibrosis in kidney biopsies

Increasing interstitial fibrosis (IF) in native and kidney transplant biopsies is associated with functional decline and serves as a clinical trial end point. A Banff 2009 Conference survey revealed a range in IF assessment practices. Observers from multiple centers were asked to assess 30 renal biopsies with a range of IF and quantitate IF using two approaches on trichrome, Periodic acid-Schiff (PAS) and computer-assisted quantification of collagen III immunohistochemistry (C-IHC) slides, as well as assessing percent of cortical tubular atrophy% (TA%) and Banff total cortical inflammation score (ti-score). C-IHC using whole slide scans was performed. C-IHC assessment showed a higher correlation with organ function (r = -0.48) than did visual assessments (r = -0.32--0.42); computerized and visual C-IHC assessment also correlated (r = 0.64-0.66). Visual assessment of trichrome and C-IHC showed better correlations with organ function and C-IHC, than PAS, TA% and ti-score. However, visual assessment of IF, independent of approach, was variable among observers, and differences in correlations with organ function were not statistically significant among C-IHC image analysis and visual assessment methods. C-IHC image analysis correlated among three centers (r > 0.90, p < 0.0001, between all centers). Given the difficulty of visual IF assessment standardization, C-IHC image could potentially accomplish standardized IF assessment in multicenter settings.

Short-term prognosis of living-donor kidney transplantation from hypertensive donors with high-normal albuminuria

BACKGROUND

High-normal albuminuria (HNA) is an independent predictor of cardiovascular risk in the general population. Although hypertensive donor (HTD) candidates with HNA were considered acceptable donors by the Amsterdam Forum 2004, the transplant prognosis of HTDs with HNA has not been determined. Therefore, we investigated the transplant prognosis of HTDs with HNA.

METHODS

We retrospectively analyzed 52 adult living-donor kidney transplants performed at Kagawa University Hospital. HNA was defined as albuminuria of 15 to 30 mg/g Cr. Changes in kidney function of donors and recipients were assessed up to 2 years after transplantation.

RESULTS

Overall, 38 donors were normotensive and 14 were hypertensive. Nine of 14 HTDs exhibited HNA before donation. More HTDs with HNA had arteriosclerotic vasculopathy or glomerulosclerosis than did normotensive donors (NTDs). Hypertension and the degree of albuminuria did not affect the donors' posttransplantation kidney function. The risk of discompensatory changes in kidney function after donation was significantly higher in HTDs with HNA than in NTDs (odds ratio, 10.5; 95% confidence interval, 1.51-72.9; P=0.02). In multivariate analysis, the coexistence of hypertension and HNA was not significantly associated with discompensatory changes after donation (adjusted odds ratio, 6.04; 95% confidence interval, 0.19-192; P=0.31). Recipients of HTDs with HNA had similar allograft survival rates but lower allograft function compared with recipients of NTDs.

CONCLUSIONS

Although further studies are needed to confirm our results, the short-term prognosis of living-donor kidney transplantation was similar between HTDs with HNA and NTDs.

Pharmacogenetics in solid organ transplantation: genes involved in mechanism of action and pharmacokinetics of immunosuppressive drugs

Allogenic solid organ transplantation has become the routine procedure in patients with end stage organ disease. Although the transplanted organ compensates deficient body functions, its allogenic nature requires institution of immune tolerance, nowadays provided by immunosuppressive drug administration. Both the safety and efficacy of immunosuppressive treatment depend on many factors, and maintaining levels of immunosuppressants within therapeutic range is the essential target for success in graft function preservation. It is obvious that drug and metabolite concentrations depend on efficiency of individual patient metabolism. Recently, many studies were undertaken to investigate the relationship between genetic factors, drug pharmacokinetics and therapy outcome, and interindividual variability apparently can be explained, at least in part, by genetically determined polymorphisms of xenobiotic-metabolizing enzymes, transport proteins and also in some cases, drug targets. This review presents the recent state of knowledge in the field of pharmacogenetics related to solid organ transplantation.

Early changes in scores of chronic damage on transplant kidney protocol biopsies reflect donor characteristics, but not future graft function

The amount of irreversible injury on renal allograft biopsy predicts function, but little is known about the early evolution of this damage. In a single-center cohort, we examined the relationship between donor-, recipient-, and transplantation-associated factors and change in a morphometric index of chronic damage (ICD) between protocol biopsies performed at implantation and at 2-3 months. We then investigated whether early delta ICD predicted subsequent biochemical outcomes. We found little evidence to support differences between the study group, who had undergone serial biopsies, and a contemporaneous control group, who had not. In allografts with serial biopsies (n = 162), there was an increase in ICD between implantation (median: 2%, IQR:0-8) and 2-3 months post-transplant (median 8% IQR:4-15; p < 0.0001). Donation from younger or live donors was independently associated with smaller early post-transplant increases in ICD. There was no evidence for a difference in delta ICD between donation after cardiac death vs. donation after brain death, nor association with length of cold ischemia. After adjustment for GFR at the time of the second biopsy, delta ICD after three months did not predict allograft function at one yr. These findings suggest that graft damage develops shortly after transplantation and reflects donor factors, but does not predict future biochemical outcomes.

Comparison of pharmacokinetics and pharmacogenetics of once- and twice-daily tacrolimus in the early stage after renal transplantation

BACKGROUND

This study investigated pharmacokinetic and pharmacogenetic differences between a modified-release once-daily formulation of tacrolimus (Tac-QD) and the original formulation requiring twice-daily intake (Tac-BID) in de novo renal transplant recipients.

METHODS

Forty-seven and 25 patients who received Tac-BID and Tac-QD, respectively, were enrolled. The pharmacokinetics and CYP3A5 6986A>G and ABCB1 3435C>T pharmacogenetics of each formulation were analyzed on day 28 posttransplantation.

RESULTS

The dose-adjusted trough level (C0) and area under the concentration-time curve (AUC0-24) of tacrolimus were approximately 25% lower for Tac-QD than Tac-BID. However, there was a good correlation between the AUC0-24 and C0 in the Tac-BID and Tac-QD groups (r=0.575, P<0.001; and r=0.638, P<0.001, respectively) and a similar coefficient in each regression equation. The dose-adjusted AUC0-24 was approximately 25% lower in carriers of the CYP3A*1 allele (CYP3A5 expressers), but not individuals with the CYP3A*3/*3 genotype (nonexpressers), for TAC-QD than Tac-BID. In the Tac-QD group, the interpatient variability for dose-adjusted parameters was small, and the interquatile ranges of dose-adjusted parameters differed between CYP3A5 expressers and nonexpressers and did not overlap. The ABCB1 polymorphism was not associated with any pharmacokinetic parameters of Tac-QD.

CONCLUSIONS

C0-guided monitoring may lead to similar AUC0-24 values for both formulations. However, to maintain the same AUC0-24 value, a higher dose of Tac-QD than Tac-BID may be needed, especially for CYP3A5 expressers, in the early stage posttransplantation. The narrow interindividual variability of Tac-QD pharmacokinetics and its difference between CYP3A5 expressers and nonexpressers might contribute to a dosing strategy based on CYP3A5 genotype.

Hyperuricemia at 1 year after renal transplantation, its prevalence, associated factors, and graft survival

BACKGROUND

The present study investigated the prevalence and predictors for the development of hyperuricemia within 1 year after transplantation and their associations with genetic polymorphisms and graft outcome in patients taking tacrolimus and mycophenolate mofetil.

METHODS

One hundred twenty-one renal allograft recipients transplanted between January 2001 and March 2009 were studied. Patients with serum uric acid concentrations above 7.0 mg/dL within 1 year after transplantation were defined as having hyperuricemia, and all were treated with allopurinol. Genetic polymorphisms of nitric oxide synthase, angiotensin-converting enzyme, methylenetetrahydrofolate reductase, and 3 uric acid transporters were examined.

RESULTS

At 1 year after transplantation, 46 (38%) recipients developed hyperuricemia. Male gender, higher body mass index, long-term pretransplantation dialysis, and hypertension were associated with the development of hyperuricemia. The estimated glomerular filtration rate (eGFR) at 1 year after transplantation was lower in the patients with hyperuricemia than in those without. There were no differences in graft survival between the two groups. The pharmacokinetics of tacrolimus and mycophenolic acid and 6 polymorphisms were not associated with hyperuricemia. In the multivariate analysis, male gender, long-term pretransplantation dialysis (>36 months), and eGFR (<60 mL/min) were independently associated with the development of hyperuricemia.

CONCLUSION

The incidence of hyperuricemia in our cohort was 38%. Male gender and long-term pretransplantation dialysis were predictors for the development of hyperuricemia. The eGFR was lower in patients with hyperuricemia, but graft survival did not differ between the patients with hyperuricemia treated with alloprinol and those without hyperuricemia. We could not define the significance of the pharmacokinetics of immunosuppressants and genetic risk factors for hyperuricemia.

Renal interstitial fibrosis: mechanisms and evaluation

PURPOSE OF REVIEW

Tubulointerstitial injury in the kidney is complex, involving a number of independent and overlapping cellular and molecular pathways, with renal interstitial fibrosis and tubular atrophy (IFTA) as the final common pathway. Furthermore, there are multiple ways to assess IFTA.

RECENT FINDINGS

Cells involved include tubular epithelial cells, fibroblasts, fibrocytes, myofibroblasts, monocyte/macrophages, and mast cells with complex and still incompletely characterized cell-molecular interactions. Molecular mediators involved are numerous and involve pathways such as transforming growth factor (TGF)-β, bone morphogenic protein (BMP), platelet-derived growth factor (PDGF), and hepatocyte growth factor (HGF). Recent genomic approaches have shed insight into some of these cellular and molecular pathways. Pathologic evaluation of IFTA is central in assessing the severity of chronic disease; however, there are a variety of methods used to assess IFTA. Most assessment of IFTA relies on pathologist assessment of special stains such as trichrome, Sirius Red, and collagen III immunohistochemistry. Visual pathologist assessment can be prone to intra and interobserver variability, but some methods employ computerized morphometery, without a clear consensus as to the best method.

SUMMARY

IFTA results from on orchestration of cell types and molecular pathways. Opinions vary on the optimal qualitative and quantitative assessment of IFTA.

Correlations between pretransplant dialysis duration, bladder capacity, and prevalence of vesicoureteral reflux to the graft

BACKGROUND

Urinary bladder capacity is reduced in patients undergoing long-term dialysis, which may increase the risk of vesicoureteral reflux (VUR) to a transplanted kidney. This study investigated the correlations between dialysis duration, pretransplant and posttransplant bladder capacity, and prevalence of VUR to the graft.

METHODS

Voiding cystography was performed in 101 adult renal transplant recipients without neurogenic disorders immediately before and 1 year after transplantation to evaluate bladder capacity and VUR. Nonstented extravesical antireflux ureteroneocystostomy was performed in all patients.

RESULTS

The median dialysis duration and pretransplant bladder capacity were 32 months (range 1-426 months) and 120 mL (range 15-450 mL), and 21 patients (20.8%) underwent dialysis for more than 120 months, and 30 patients (29.7%) had a pretransplant bladder capacity of less than 80 mL. Dialysis duration was correlated with pretransplant bladder capacity (R=0.466, P<0.001). Bladder capacity expanded more than 6-fold from pretransplantation to posttransplantation, and all recipients had a bladder capacity greater than 150 mL at 1 year posttransplantation. Thirty patients had VUR to the graft. Dialysis duration longer than 60 months (P=0.021) and pretransplant bladder capacity of less than 130 mL (P=0.024) were associated with VUR. VUR was associated with lower graft function.

CONCLUSIONS

Although bladder capacity decreased because of long-term dialysis, it exceeded 150 mL at 1 year posttransplantation. A small bladder can be used in renal transplantation, but it may increase the risk of VUR.

Impact of the CYP3A4*1G polymorphism and its combination with CYP3A5 genotypes on tacrolimus pharmacokinetics in renal transplant patients

Aim: Tacrolimus is a substrate of CYP3A4 and CYP3A5. The present study investigated the impact of the CYP3A4*1/*1G polymorphism compared with CYP3A5 genotypes on the dose-adjusted pharmacokinetics of tacrolimus. The effects of the polymorphism on the variability in tacrolimus pharmacokinetics among patients with the CYP3A5*1 allele (CYP3A5 expresser) and among those with CYP3A5*3/*3 genotype (nonexpresser) were also studied. Materials & methods: A total of 136 renal allograft recipients were given repeated doses of tacrolimus every 12 h. On day 28 after the renal transplantation, blood tacrolimus concentrations were measured, and dose-adjusted pharmacokinetics were determined and compared with the corresponding genotype. Results: The dose-adjusted AUC0–12 and C0 of tacrolimus were significantly lower in patients with the CYP3A4*1G allele and CYP3A5 expressers than those with the CYP3A4*1/*1 genotype and nonexpressers, respectively. In a multiple regression analysis, the dose-adjusted AUC0–12 and C0 values were associated with CYP3A4*1/*1 (p = 0.018 and 0.040, respectively) and CYP3A5*3/*3 (p < 0.001 each). The standardized regression coefficient for the AUC0–12 of tacrolimus was approximately twofold less for CYP3A4*1/*1 than CYP3A5*3/*3. The lowest dose-adjusted AUC0–12 was found in CYP3A5 expressers with the CYP3A4*1G allele. Conclusion: The CYP3A4*1/*1G polymorphism was associated with the pharmacokinetics of tacrolimus, however, its contribution to dose-adjusted pharmacokinetics was approximately twofold less than that of the CYP3A5*1/*3 polymorphism. Although its effect on CYP3A4 activity is not clear, CYP3A4*1/*1G may be a candidate for a polymorphism affecting the interindividual variability in tacrolimus pharmacokinetics among CYP3A5 expressers.

Original submitted 5 January 2011; Revision submitted 22 February 2011