Autosomal-dominant polycystic kidney disease: high prevalence of graft loss for death-related malignancies and cardiovascular risk factors

TRPP2 ion channels: The roles in various subcellular locations

TRPP2 (PC2, PKD2 or Polycytin-2), encoded by PKD2 gene, belongs to the nonselective cation channel TRP family. Recently, the three-dimensional structure of TRPP2 was constructed. TRPP2 mainly functions in three subcellular compartments: endoplasmic reticulum, plasma membrane and primary cilia. TRPP2 can act as a calcium-activated intracellular calcium release channel on the endoplasmic reticulum. TRPP2 also interacts with other Ca²⁺ release channels to regulate calcium release, like IP3R and RyR2. TRPP2 acts as an ion channel regulated by epidermal growth factor through activation of downstream factors in the plasma membrane. TRPP2 binding to TRPC1 in the plasma membrane or endoplasmic reticulum is associated with mechanosensitivity. In cilium, TRPP2 was found to combine with PKD1 and TRPV4 to form a complex related to mechanosensitivity. Because TRPP2 is involved in regulating intracellular ion concentration, TRPP2 mutations often lead to autosomal dominant polycystic kidney disease, which may also be associated with cardiovascular disease. In this paper, we review the molecular structure of TRPP2, the subcellular localization of TRPP2, the related functions and mechanisms of TRPP2 at different sites, and the diseases related to TRPP2.

Pancreatic Cysts and Intraductal Papillary Mucinous Neoplasm in Autosomal Dominant Polycystic Kidney Disease

OBJECTIVES

Pancreatic lesions in autosomal dominant polycystic kidney disease (ADPKD) are primarily cysts. They are increasingly recognized, with isolated reports of intraductal papillary mucinous neoplasia (IPMN).

METHODS

Retrospective study to determine prevalence, number, size, and location of pancreatic abnormalities using abdominal magnetic resonance imaging (MRI) of genotyped ADPKD patients (seen February 1998 to October 2013) and compared with age- and sex-matched non-ADPKD controls. We evaluated presentation, investigation, and management of all IPMNs among individuals with ADPKD (January 1997 to December 2016).

RESULTS

Abdominal MRIs were examined for 271 genotyped ADPKD patients. A pancreatic cyst lesion (PCL) was detected in 52 patients (19%; 95% confidence interval, 15%-23%). Thirty-seven (71%) had a solitary PCL; 15 (28%) had multiple. Pancreatic cyst lesion prevalence did not differ by genotype. Intraductal papillary mucinous neoplasia was detected in 1% of ADPKD cases. Among 12 IPMN patients (7 branch duct; 5 main duct or mixed type) monitored for about 140 months, 2 with main duct IPMNs required Whipple resection, and 1 patient died of complications from small-bowel obstruction after declining surgical intervention.

CONCLUSIONS

With MRI, PCLs were detected in 19% and IPMNs in 1% of 271 ADPKD patients with proven mutations, without difference across genotypes. Pancreatic cyst lesions were asymptomatic and remained stable in size.

The functions of TRPP2 in the vascular system

TRPP2 (polycystin-2, PC2 or PKD2), encoded by the PKD2 gene, is a non-selective cation channel with a large single channel conductance and high Ca(2+) permeability. In cell membrane, TRPP2, along with polycystin-1, TRPV4 and TRPC1, functions as a mechanotransduction channel. In the endoplasmic reticulum, TRPP2 modulates intracellular Ca(2+) release associated with IP3 receptors and the ryanodine receptors. Noteworthily, TRPP2 is widely expressed in vascular endothelial and smooth muscle cells of all major vascular beds, and contributes to the regulation of vessel function. The mutation of the PKD2 gene is a major cause of autosomal dominant polycystic kidney disease (ADPKD), which is not only a common genetic disease of the kidney but also a systemic disorder associated with abnormalities in the vasculature; cardiovascular complications are the leading cause of mortality and morbidity in ADPKD patients. This review provides an overview of the current knowledge regarding the TRPP2 protein and its possible role in cardiovascular function and related diseases.

Risk Factors of Graft Survival After Diagnosis of Post-kidney Transplant Malignancy: Using Cox Proportional Hazard Model

BACKGROUND

All recipients of kidney transplantation, especially those with posttransplant malignancy, are at risk of long-term graft failure.

OBJECTIVES

The purpose of our study was to evaluate the risk factors associated with graft survival after diagnosis of malignancy.

PATIENTS AND METHODS

To reach this purpose, we conducted a historical cohort study in Iran and 266 cases with posttransplant malignancy were followed up from diagnosis of malignancy until long-term graft loss or the date of last visit. These patients were taken as a census from 16 Transplant Centers in Iran during 22 years follow-up period since October 1984 to December 2008. A Cox proportional hazards model was performed to determine the important independent predictors of graft survival after malignancy.

RESULTS

At the end of the study, long-term graft failure was seen in 27 (10.2%) cases. One-year and 2-year graft survival after diagnosis of cancer were 93.6% and 91.7%, respectively. The univariate analysis showed that the incidence of chronic graft loss was significantly higher in male patients with solid cancers, withdrawal of immunosuppressant regimen, no response to treatment, and tumor metastasis. In continuation, the Cox model indicated that the significant risk factors associated with graft survival were type of cancer (P < 0.0001), response to treatment (P < 0.0001, HR = 0.14, 95% CI: 0.06 - 0.32), metastasis (P < 0.0001, HR = 5.68, 95% CI: 2.24 - 14.42), and treatment modality (P = 0.0001).

CONCLUSIONS

By controlling the modifiable risk factors and modality of treatment in our study, physicians can reach more effective treatment.

Current management of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD), the most frequent cause of genetic renal disease affecting approximately 4 to 7 million individuals worldwide and accounting for 7%-15% of patients on renal replacement therapy, is a systemic disorder mainly involving the kidney but cysts can also occur in other organs such as the liver, pancreas, arachnoid membrane and seminal vesicles. Though computed tomography and magnetic resonance imaging (MRI) were similar in evaluating 81% of cystic lesions of the kidney, MRI may depict septa, wall thickening or enhancement leading to upgrade in cyst classification that can affect management. A screening strategy for intracranial aneurysms would provide 1.0 additional year of life without neurological disability to a 20-year-old patient with ADPKD and reduce the financial impact on society of the disease. Current treatment strategies include reducing: cyclic adenosine monophosphate levels, cell proliferation and fluid secretion. Several randomised clinical trials (RCT) including mammalian target of rapamycin inhibitors, somatostatin analogues and a vasopressin V2 receptor antagonist have been performed to study the effect of diverse drugs on growth of renal and hepatic cysts, and on deterioration of renal function. Prophylactic native nephrectomy is indicated in patients with a history of cyst infection or recurrent haemorrhage or to those in whom space must be made to implant the graft. The absence of large RCT on various aspects of the disease and its treatment leaves considerable uncertainty and ambiguity in many aspects of ADPKD patient care as it relates to end stage renal disease (ESRD). The outlook of patients with ADPKD is improving and is in fact much better than that for patients in ESRD due to other causes. This review highlights the need for well-structured RCTs as a first step towards trying newer interventions so as to develop updated clinical management guidelines.

Renal cancer in kidney transplanted patients

Renal cancer occurs more frequently in renal transplanted patients than in the general population, affecting native kidneys in 90% of cases and the graft in 10 %. In addition to general risk factors, malignancy susceptibility may be influenced by immunosuppressive therapy, the use of calcineurin inhibitors (CNI) as compared with mammalian target of rapamycin inhibitors, and the length of dialysis treatment. Acquired cystic kidney disease may increase the risk for renal cancer after transplantation, while autosomal dominant polycystic kidney disease does not seem to predispose to cancer development. Annual ultrasound evaluation seems appropriate in patients with congenital or acquired cystic disease or even a single cyst in native kidneys, and every 2 years in patients older than 60 years if they were on dialysis for more than 5 years before transplantation. Immunosuppression should be lowered in patients who develop renal cancer, by reduction or withdrawal of CNI. Although more evidence is still needed, it seems reasonable to shift patients from CNI to everolimus or sirolimus if not already treated with one of these drugs, with due caution in subjects with chronic allograft nephropathy.

Serum uric acid levels and endothelial dysfunction in patients with autosomal dominant polycystic kidney disease

BACKGROUND/AIMS

Patients with autosomal dominant polycystic kidney disease (ADPKD) exhibit endothelial dysfunction (ED) despite normal levels of renal function. Hyperuricemia occurs in these patients and has been postulated to affect ED through the generation of oxidative stress. We therefore investigated the prevalence of ED and its association with serum uric acid levels in early-stage ADPKD.

METHODS

A cross-sectional design was used for the assessment of prevalent patients with early-stage (normal renal function) ADPKD (n = 91) from two academic medical centers. ED was assessed using ischemia-induced forearm flow-mediated vasodilation (FMD). Serum uric acid levels were evaluated using an Olympus AU2700 autoanalyzer.

RESULTS

ADPKD patients with higher serum uric acid levels had a higher asymmetric dimethylarginine (ADMA) level (1.19 ± 0.2 vs. 1.47 ± 0.3, p < 0.001) and lower FMD rates (8.1 ± 1.3 vs. 6.8 ± 0.7, p < 0.001). In multiple regression analysis for predictors of cohort FMD, uric acid (β = -0.32, p < 0.001), ADMA (β = -0.36, p < 0.001), high-sensitivity C reactive protein (CRP; β = -0.32, p < 0.001) and estimated glomerular filtration rate (eGFR; β = 0.33, p < 0.001) all predicted FMD.

CONCLUSIONS

In early-stage ADPKD patients, uric acid levels, serum ADMA and eGFR all independently predict ED in a similar manner. Future studies are needed to investigate the causes of elevated serum uric acid, ADMA and CRP in these patients.

Myxoid liposarcoma involving the liver, subcutaneous tissue, and epidural space in a polycystic disease patient

We present a case of a myxoid liposarcoma involving the liver, subcutaneous tissue, and epidural space in a polycystic disease patient with minimally increased F-18 FDG activity and review the image findings of myxoid liposarcoma.

Beyond anemia: the clinical impact of the physiologic effects of erythropoietin

Although we have known that oxygen tension affects erythrocyte production since the 19th century, we have only recently begun to understand many subtleties of erythropoietin (EPO) physiology. EPO administration has allowed hundreds of thousands of patients to avoid transfusions. With the beneficial effects so apparent a detailed understanding of the full clinical physiology of this plasma factor seemed less important. However, the unanticipated increase in mortality found in recent randomized studies is prompting a reassessment of this view. We will review what is known about the physiology of this plasma factor that, it is now clear, is more than just an erythrocyte production factor.

Skin cancer in organ transplant recipients: effect of pretransplant end-organ disease

BACKGROUND

Solid organ transplant recipients are at increased risk for posttransplant neoplasms.

OBJECTIVE

Our purpose was to determine whether various diseases causing end-organ failure are associated with different degrees of risk of skin cancer development after transplantation.

METHODS

The Organ Procurement and Transplantation Network/United Network for Organ Sharing Transplant Tumor Registry was searched for the incidence of skin cancer among kidney, liver, and heart transplant recipients in the United States between 1996 and 2001. Multivariate analysis was used to determine the association between disease diagnosis and posttransplant skin cancer.

RESULTS

Transplant recipients with specific pretransplant diseases, such as polycystic kidney disease and cholestatic liver disease, were at increased risk for skin cancer. Patients with diabetes mellitus had a lower incidence of skin cancer after kidney transplantation.

LIMITATIONS

The study had only a brief follow-up period, indirect assessment of photodamage, and possible underreporting.

CONCLUSION

Transplant recipients with a history of certain diseases warrant intensive skin cancer surveillance and strict sun-protective practices.

Therapy and Prognosis of Tumors of the Genitourinary Tract After Kidney Transplantation

There is an increased incidence of tumors of the genitourinary tract among kidney graft recipients. From 1979 to 2001, all patients who received kidney transplants had records of both their underlying diseases and their initial immunosuppression. Patients who developed a genitourinary tract malignancy were evaluated for tumor type, location, stage, tumor therapy and clinical course. During this period, 1804 patients underwent 2068 kidney transplantations. Thirty-four patients had 39 tumors of genitourinary origin. One patient was lost to follow-up. There were 15 patients with 18 renal cell carcinomas (one of them multifocal): six had seven transitional cell carcinomas; six, prostatic carcinoma; six, tumor of the female genital tract (one also had a renal cell carcinoma); and two, a seminoma. Most tumors were diagnosed in their early stages (< or = pT3, N0, M0; n = 31 tumors) and thus accessible to curative therapy, achieving good long-term results: 1- and 5-year survival rates of 100% and 91%, which were better than those obtained in advanced stages (N+, M+; n = 7 tumors), namely both 1- and 5-year survival rates of 38% (P < .05). Death was caused by tumor growth in nine patients (27%) and by other causes in three patients (9%). With appropriate treatment genitourinary tumors at early stage show a good prognosis. New immunosuppressants with supposed antiproliferative effects may help to decrease the incidence of malignancies. The most important factor is risk-adapted screening to identify malignancies early and to initiate appropriate therapy.