Recommendations for pathological diagnosis on biopsy samples from peritoneal dialysis patients

Application of algorithmic cytomorphological assessment and immunocytochemistry with the international system for reporting serous fluid cytopathology on pericardial fluid cytology

AIMS

The international system for reporting serous fluid cytopathology (ISRSFC) set forth a five-tiered reporting system with comprehensive validation on pleural and peritoneal fluid cytology. An algorithmic approach for cytomorphological assessment and immunocytochemistry was also described in ISRSFC. Limited data on pericardial fluid are supportive but would benefit from further investigation.

METHODS

Consecutive pericardial fluid cytology over a 4-year period was reviewed by multiple board-certified pathologists according to the ISRSFC. Cytomorphology and immunocytochemistry were assessed sequentially, with respective diagnostic performances computed and compared. Literature review was performed.

RESULTS

In total 358 specimens, including 53 with immunocytochemistry available, were reviewed. There were 137 benign and 221 malignant (MAL) cases. The risks of malignancy were 23.5% non-diagnostic (ND), 29.2% negative for malignancy (NFM), 56.0% atypia of undetermined significance (AUS), 82.6% suspicious for malignancy (SFM) and 99.2% (MAL) for cytomorphological assessment, improving to 23.5% (ND), 29.1% (NFM), 56.8% (AUS), 78.9% (SFM) and 99.3% (MAL) incorporating immunocytochemistry. Ten cases (2.8%) received a change in diagnosis after review of immunocytochemistry. All revisions of diagnostic category were appropriate upgrades/downgrades referenced against clinical information. Cytomorphological typing was accurate for adenocarcinoma (n=81/83, 97.6%), while other carcinomas and lymphomas required immunocytochemistry. Certain subcategories within AUS and SFM pertaining to bland indeterminate epithelial cells or mucinous material were not seen for pericardial fluid.

CONCLUSIONS

The ISRSFC shows robust diagnostic performance for pericardial fluid cytology. For pericardial effusion, disease composition and applicable cytological subcategories differ from its peritoneal and pleural counterparts. Incorporating immunocytochemistry by an algorithmic approach improves diagnostic accuracy. Cytomorphology is accurate for identifying adenocarcinomas, but further typing necessitates immunocytochemistry is necessary.

Pathophysiology of encapsulating peritoneal sclerosis: lessons from findings of the past three decades in Japan

Encapsulating peritoneal sclerosis (EPS), a condition with a high mortality rate, is a serious complication of peritoneal dialysis (PD). In Japan, EPS became a central issue in the clinical setting during the mid-90s and the beginning of this century. However, following the introduction of biocompatible neutral PD solutions containing lower levels of glucose degradation products, the incidence and clinical severity of EPS has been greatly lessened. During the past three decades, the etiology of EPS has been elucidated by findings obtained by peritoneal biopsy, laparoscopy, and surgical intervention. Accumulating findings suggest the need for a paradigm change on the nature of EPS pathophysiology; notably, EPS appears not to reflect peritoneal sclerosis per se, but rather the formation of a neo-membrane as a biological reaction to peritoneal injury. This narrative review looks back on the history of EPS in Japan, and discusses EPS pathophysiology, the impact of neutral PD solution on peritoneal protection, and a future novel diagnostic approach, ultra-fine endoscope, for the identification of patients at high risk of EPS.

Differentially Expressed microRNAs in Peritoneal Dialysis Effluent-Derived Exosomes from the Patients with Ultrafiltration Failure

Background

Ultrafiltration failure remains one of the most severe complications of long-term peritoneal dialysis (PD), which results in death. This study aimed to characterize the circulating exosomal microRNA (miRNA) profiles associated with ultrafiltration failure and explore its underlying mechanisms.

Methods

Exosomes were isolated from the peritoneal dialysis effluent (PDE) of patients with ultrafiltration failure or success using the ultracentrifugation method, and then transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blot were used for exosome characterization. After that, the isolated exosomes were sent for small RNA sequencing, and eight differentially expressed miRNAs (DE-miRNAs) were chosen for RT-qPCR validation.

Results

TEM, NTA, and western blot revealed that exosomes were successfully isolated. After sequencing, 70 DE-miRNAs involved in ultrafiltration were identified, including 41 upregulated ones and 29 downregulated ones. Functional analyses revealed that these DE-miRNAs were significantly enriched in pathways of cancer, ubiquitin-mediated proteolysis, axon orientation, and the Rap1 and Ras signaling pathways. In addition, the consistency rate of RT-qPCR and sequencing results was 75%, which indicated the relatively high reliability of the sequencing data.

Conclusions

Our findings implied that these DE-miRNAs may be potential biomarkers of ultrafiltration failure, which would help us to discover novel therapeutic targets/pathways for ultrafiltration failure in patients with end-stage renal disease.

Effluent decoy receptor 2 as a novel biomarker of peritoneal fibrosis in peritoneal dialysis patients

BACKGROUND

Peritoneal fibrosis (PF) is a common complication of peritoneal dialysis (PD), but a specific and sensitive biomarker for PF is lacking. The present study aimed to determine the use of effluent decoy receptor 2 (eDcR2) as a biomarker for PF in PD patients.

METHODS

PD patients (n = 248) were recruited, and peritoneal specimens were collected at PD initiation (n = 30) and cessation (n = 33). Enzyme-linked immunoassay was used to measure eDcR2 and the eDcR2 appearance rate (eDcR2-AR) was calculated. The levels of DcR2 mRNA and protein were determined. The correlation of eDcR2 level with peritoneal function, histological parameters and DcR2 expression were analysed. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of eDcR2 for PF, which was defined as a submesothelial thickness 150 µm or more. Co-localisation of DcR2 with a mesothelial marker, fibroblast markers and fibrotic markers were determined.

RESULTS

The eDcR2-AR level correlated with PD duration, D/P Cr values, peritoneal Kt/V and peritoneal injury scores, especially submesothelial thickness (r = 0.638, p < 0.001). DcR2 was primarily expressed in peritoneal fibroblasts, and co-localised with α-SMA, vimentin, collagen I and fibronectin, but not with E-cadherin. Peritoneal DcR2 expression had a positive correlation with eDcR2-AR. ROC analysis indicated eDcR2 had an area under the curve of 0.907 for detection of PF (sensitivity: 78.6%, specificity: 100%) and the best cut-off value was 392.5 pg/min.

CONCLUSION

The eDcR2-AR level is a potential biomarker for assessing PF in PD patients. Effluent DcR2 was mainly derived from peritoneal fibroblasts and DcR2-positive cells may accelerate PF, suggesting that it may be a potential therapeutic target.

Adverse factors on nonenhanced abdominal CT for long-term continuous ambulatory peritoneal dialysis: a comparative study between patients who withdraw from and maintain long-term peritoneal dialysis

Purpose

To investigate the imaging features of patients with long-term continuous ambulatory peritoneal dialysis (CAPD) on nonenhanced abdominal CT and to identify adverse factors for long-term CAPD.

Methods

A total of 109 patients with less than 5 years of CAPD for peritoneal ultrafiltration failure who switched to hemodialysis (withdrawal group) and 23 patients with more than 10 years of CAPD (long-term group) were retrospectively enrolled. Nonenhanced CT manifestations in both groups were compared, including thickening and calcification of the parietal peritoneum, calcification of the mesangial margin and free margin of the small intestine wall, and calcification of the mesentery and abdominal aorta. A risk stratification model was proposed based on CT manifestations with statistically significant differences.

Results

The presence of the following CT findings was significantly different between two groups: extensive thickening of the parietal peritoneum (78.9% vs. 21.7%, P < 0.01); severe calcification of the parietal peritoneum (60.6% vs. 8.7%, P < 0.01); calcification of the mesentery (32.1% vs. 4.3%, P < 0.05); and calcification of the free margin of the small intestine wall (49.5% vs. 13.0%, P < 0.05). However, there was no significant difference in calcification of the mesangial margin of the small intestine wall (40.3% vs. 30.4%) or in abdominal aortic calcification (56.9% vs. 61.1%) (P > 0.05). The area under the receiver operating characteristic curve (AUC) was 0.906 (sensitivity 87.6% and specificity 82.6%).

Conclusion

Extensive thickening of the parietal peritoneum, severe calcification of the parietal peritoneum, and calcification of the mesentery and the free margin of the small intestine wall are adverse factors for long-term CAPD.

Increased miR-7641 Levels in Peritoneal Hyalinizing Vasculopathy in Long-Term Peritoneal Dialysis Patients

Peritoneal hyalinizing vasculopathy (PHV) represents the cornerstone of long-term peritoneal dialysis (PD), and especially characterizes patients associated with encapsulating peritoneal sclerosis. However, the mechanisms of PHV development remain unknown. A cross sectional study was performed in 100 non-selected peritoneal biopsies of PD patients. Clinical data were collected and lesions were evaluated by immunohistochemistry. In selected biopsies a microRNA (miRNA)-sequencing analysis was performed. Only fifteen patients (15%) showed PHV at different degrees. PHV prevalence was significantly lower among patients using PD fluids containing low glucose degradation products (GDP) (5.9% vs. 24.5%), angiotensin converting enzyme inhibitors (ACEIs) (7.5% vs. 23.4%), statins (6.5% vs. 22.6%) or presenting residual renal function, suggesting the existence of several PHV protective factors. Peritoneal biopsies from PHV samples showed loss of endothelial markers and induction of mesenchymal proteins, associated with collagen IV accumulation and wide reduplication of the basement membrane. Moreover, co-expression of endothelial and mesenchymal markers, as well as TGF-β1/Smad3 signaling activation were found in PHV biopsies. These findings suggest that an endothelial-to-mesenchymal transition (EndMT) process was taking place. Additionally, significantly higher levels of miR-7641 were observed in severe PHV compared to non-PHV peritoneal biopsies. Peritoneal damage by GDPs induce miRNA deregulation and an EndMT process in submesothelial vessels, which could contribute to collagen IV accumulation and PHV.

Hyperspectral evaluation of peritoneal fibrosis in mouse models

Analysis of morphological changes of the peritoneal membrane is an essential part of animal studies when investigating molecular mechanisms involved in the development of peritoneal fibrosis or testing the effects of potential therapeutic agents. Current methods, such as histology and immunohistochemistry, require time consuming sample processing and analysis and result in limited spatial information. In this paper we present a new method to evaluate structural and chemical changes in an animal model of peritoneal fibrosis that is based on hyperspectral imaging and a model of light transport. The method is able to distinguish between healthy and diseased subjects based on morphological as well as physiological parameters such as blood and scattering parameters. Furthermore, it enables evaluation of changes, such as degree of inflammation and fibrosis, that are closely related to histological findings.

Hypoxia, cytokines and stromal recruitment: parallels between pathophysiology of encapsulating peritoneal sclerosis, endometriosis and peritoneal metastasis

Peritoneal response to various kinds of injury involves loss of peritoneal mesothelial cells (PMC), danger signalling, epithelial-mesenchymal transition and mesothelial-mesenchymal transition (MMT). Encapsulating peritoneal sclerosis (EPS), endometriosis (EM) and peritoneal metastasis (PM) are all characterized by hypoxia and formation of a vascularized connective tissue stroma mediated by vascular endothelial growth factor (VEGF). Transforming growth factor-β1 (TGF-β1) is constitutively expressed by the PMC and plays a major role in the maintenance of a transformed, inflammatory micro-environment in PM, but also in EPS and EM. Persistently high levels of TGF-β1 or stimulation by inflammatory cytokines (interleukin-6 (IL-6)) induce peritoneal MMT, adhesion formation and fibrosis. TGF-β1 enhances hypoxia inducible factor-1α expression, which drives cell growth, extracellular matrix production and cell migration. Disruption of the peritoneal glycocalyx and exposure of the basement membrane release low molecular weight hyaluronan, which initiates a cascade of pro-inflammatory mediators, including peritoneal cytokines (TNF-α, IL-1, IL-6, prostaglandins), growth factors (TGF-α, TGF-β, platelet-derived growth factor, VEGF, epidermal growth factor) and the fibrin/coagulation cascade (thrombin, Tissue factor, plasminogen activator inhibitor [PAI]-1/2). Chronic inflammation and cellular transformation are mediated by damage-associated molecular patterns, pattern recognition receptors, AGE-RAGE, extracellular lactate, pro-inflammatory cytokines, reactive oxygen species, increased glycolysis, metabolomic reprogramming and cancer-associated fibroblasts. The pathogenesis of EPS, EM and PM shows similarities to the cellular transformation and stromal recruitment of wound healing.