Smooth Muscle Enriched Long Noncoding RNA (SMILR) Regulates Cell Proliferation.

BACKGROUND: Phenotypic switching of vascular smooth muscle cells from a contractile to a synthetic state is implicated in diverse vascular pathologies, including atherogenesis, plaque stabilization, and neointimal hyperplasia. However, very little is known about the role of long noncoding RNA (lncRNA) during this process. Here, we investigated a role for lncRNAs in vascular smooth muscle cell biology and pathology. METHODS AND RESULTS: Using RNA sequencing, we identified >300 lncRNAs whose expression was altered in human saphenous vein vascular smooth muscle cells following stimulation with interleukin-1α and platelet-derived growth factor. We focused on a novel lncRNA (Ensembl: RP11-94A24.1), which we termed smooth muscle-induced lncRNA enhances replication (SMILR). Following stimulation, SMILR expression was increased in both the nucleus and cytoplasm, and was detected in conditioned media. Furthermore, knockdown of SMILR markedly reduced cell proliferation. Mechanistically, we noted that expression of genes proximal to SMILR was also altered by interleukin-1α/platelet-derived growth factor treatment, and HAS2 expression was reduced by SMILR knockdown. In human samples, we observed increased expression of SMILR in unstable atherosclerotic plaques and detected increased levels in plasma from patients with high plasma C-reactive protein. CONCLUSIONS: These results identify SMILR as a driver of vascular smooth muscle cell proliferation and suggest that modulation of SMILR may be a novel therapeutic strategy to reduce vascular pathologies.

Clinical outcomes and adverse events of bariatric surgery in adults with severe obesity in Scotland: the SCOTS observational cohort study.

Background: Bariatric surgery is a common procedure worldwide for the treatment of severe obesity and associated comorbid conditions but there is a lack of evidence as to medium-term safety and effectiveness outcomes in a United Kingdom setting. Objective: To establish the clinical outcomes and adverse events of different bariatric surgical procedures, their impact on quality of life and the effect on comorbidities. Design: Prospective observational cohort study. Setting: National Health Service secondary care and private practice in Scotland, United Kingdom. Participants: Adults (age >16 years) undergoing their first bariatric surgery procedure. Main outcome measures: Change in weight, hospital length of stay, readmission and reoperation rate, mortality, diabetes outcomes (HbA1c, medications), quality of life, anxiety, depression. Data sources: Patient-reported outcome measures, hospital records, national electronic health records (Scottish Morbidity Record 01, Scottish Care Information Diabetes, National Records Scotland, Prescription Information System). Results: Between December 2013 and February 2017, 548 eligible patients were approached and 445 participants were enrolled in the study. Of those, 335 had bariatric surgery and 1 withdrew from the study. Mean age was 46.0 (9.2) years, 74.7% were female and the median body mass index was 46.4 (42.4; 52.0) kg/m2. Weight was available for 128 participants at 3 years: mean change was -19.0% (±14.1) from the operation and -24.2% (±12.8) from the start of the preoperative weight-management programme. One hundred and thirty-nine (41.4%) participants were readmitted to hospital in the same or subsequent 35 months post surgery, 18 (5.4% of the operated cohort) had a reoperation or procedure considered to be related to bariatric surgery gastrointestinal complications or revisions. Fewer than five participants (<2%) died during follow-up. HbA1c was available for 93/182 and diabetes medications for 139/182 participants who had type 2 diabetes prior to surgery; HbA1c mean change was -5.72 (±16.71) (p = 0.001) mmol/mol and 65.5% required no diabetes medications (p < 0.001) at 3 years post surgery. Physical quality of life, available for 101/335 participants, improved in the 3 years post surgery, mean change in Rand 12-item Short Form Survey physical component score 8.32 (±8.95) (p < 0.001); however, there was no change in the prevalence of anxiety or depression. Limitations: Due to low numbers of bariatric surgery procedures in Scotland, recruitment was stopped before achieving the intended 2000 participants and follow-up was reduced from 10 years to 3 years. Conclusions: Bariatric surgery is a safe and effective treatment for obesity. Patients in Scotland, UK, appear to be older and have higher body mass than international comparators, which may be due to the small number of procedures performed. Future work: Intervention studies are required to identify the optimal pre- and post surgery pathway to maximise safety and cost-effectiveness. Study registration: This study is registered as ISRCTN47072588. Funding details: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 10/42/02) and is published in full in Health Technology Assessment; Vol. 28, No. 7. See the NIHR Funding and Awards website for further award information.

Bariatric surgery is performed on the stomach and small bowel to help people living with obesity lose weight. Our research study has looked at who is getting bariatric surgery, if they are having problems afterwards, how much weight they lose and if their medical conditions improve. A total of 444 people who were attending bariatric surgery services in Scotland, UK, agreed to take part and 336 had surgery. One hundred and eighty-nine of them completed a questionnaire before their surgery and 85 of them after 3 years, to tell us about how they were feeling physically and mentally. We looked at their computer hospital records to see how long they spent in hospital, any medical problems and changes to diabetes medicines and tests. One in five people taking part did not have surgery after all; they changed their mind or the hospital teams did not think it would be safe or work well for the patient. Those who had surgery lost 19% of their body weight and those with type 2 diabetes needed less or no medication 3 years after the surgery. The effect of physical symptoms on day-to-day activities improved but mental health did not. Compared to other countries, the people taking part were older, heavier and sicker. They spent longer in hospital after surgery and were more likely to be readmitted to hospital. How many appointments they had or what type of health professional they saw before or after surgery did not change these results. We had hoped to have far more people in this study and be able to answer more questions, but not enough people were getting bariatric surgery in Scotland for us to ask them to take part. Further research is needed to find the best ways to care for people living with obesity who would benefit from bariatric surgery.

Role of microRNAs 99b, 181a, and 181b in the differentiation of human embryonic stem cells to vascular endothelial cells.

MicroRNAs (miRNAs) are short noncoding RNAs, which post-transcriptionally regulate gene expression. miRNAs are transcribed as precursors and matured to active forms by a series of enzymes, including Dicer. miRNAs are important in governing cell differentiation, development, and disease. We have recently developed a feeder- and serum-free protocol for direct derivation of endothelial cells (ECs) from human embryonic stem cells (hESCs) and provided evidence of increases in angiogenesis-associated miRNAs (miR-126 and -210) during the process. However, the functional role of miRNAs in hESC differentiation to vascular EC remains to be fully interrogated. Here, we show that the reduction of miRNA maturation induced by Dicer knockdown suppressed hES-EC differentiation. A miRNA microarray was performed to quantify hES-EC miRNA profiles during defined stages of endothelial differentiation. miR-99b, -181a, and -181b were identified as increasing in a time- and differentiation-dependent manner to peak in mature hESC-ECs and adult ECs. Augmentation of miR-99b, -181a, and -181b levels by lentiviral-mediated transfer potentiated the mRNA and protein expression of EC-specific markers, Pecam1 and VE Cadherin, increased nitric oxide production, and improved hES-EC-induced therapeutic neovascularization in vivo. Conversely, knockdown did not impact endothelial differentiation. Our results suggest that miR-99b, -181a, and -181b comprise a component of an endothelial-miRNA signature and are capable of potentiating EC differentiation from pluripotent hESCs.

Mitochondrial reactive oxygen species enhance AMP-activated protein kinase activation in the endothelium of patients with coronary artery disease and diabetes.

The aim of the present study was to determine whether the endothelial dysfunction associated with CAD (coronary artery disease) and T2D (Type 2 diabetes mellitus) is concomitant with elevated mtROS (mitochondrial reactive oxygen species) production in the endothelium and establish if this, in turn, regulates the activity of endothelial AMPK (AMP-activated protein kinase). We investigated endothelial function, mtROS production and AMPK activation in saphenous veins from patients with advanced CAD. Endothelium-dependent vasodilation was impaired in patients with CAD and T2D relative to those with CAD alone. Levels of mitochondrial H(2)O(2) and activity of AMPK were significantly elevated in primary HSVECs (human saphenous vein endothelial cells) from patients with CAD and T2D compared with those from patients with CAD alone. Incubation with the mitochondria-targeted antioxidant, MitoQ(10) significantly reduced AMPK activity in HSVECs from patients with CAD and T2D but not in cells from patients with CAD alone. Elevated mtROS production in the endothelium of patients with CAD and T2D increases AMPK activation, supporting a role for the kinase in defence against oxidative stress. Further investigation is required to determine whether pharmacological activators of AMPK will prove beneficial in the attenuation of endothelial dysfunction in patients with CAD and T2D.

Impaired renal function impacts negatively on vascular stiffness in patients with coronary artery disease.

BACKGROUND: Chronic kidney disease (CKD) and coronary artery disease (CAD) are independently associated with increased vascular stiffness. We examined whether renal function contributes to vascular stiffness independently of CAD status. METHODS: We studied 160 patients with CAD and 169 subjects without CAD. The 4-variable MDRD formula was used to estimate glomerular filtration rate (eGFR); impaired renal function was defined as eGFR <60 mL/min. Carotid-femoral pulse wave velocity (PWV) was measured with the SphygmoCor® device. Circulating biomarkers were assessed in plasma using xMAP® multiplexing technology. RESULTS: Patients with CAD and impaired renal function had greater PWV compared to those with CAD and normal renal function (10.2 [9.1;11.2] vs 7.3 [6.9;7.7] m/s; P < 0.001). In all patients, PWV was a function of eGFR (ß = -0.293; P < 0.001) even after adjustment for age, sex, systolic blood pressure, body mass index and presence or absence of CAD. Patients with CAD and impaired renal function had higher levels of adhesion and inflammatory molecules including E-selectin and osteopontin (all P < 0.05) compared to those with CAD alone, but had similar levels of markers of oxidative stress. CONCLUSIONS: Renal function is a determinant of vascular stiffness even in patients with severe atherosclerotic disease. This was paralleled by differences in markers of cell adhesion and inflammation. Increased vascular stiffness may therefore be linked to inflammatory remodeling of the vasculature in people with impaired renal function, irrespective of concomitant atherosclerotic disease.

SurgiCal Obesity Treatment Study (SCOTS): a prospective, observational cohort study on health and socioeconomic burden in treatment-seeking individuals with severe obesity in Scotland, UK.

OBJECTIVES: There is a lack of evidence to inform the delivery and follow-up of bariatric surgery for people with severe obesity. The SurgiCal Obesity Treatment Study (SCOTS) is a national longitudinal cohort of people undergoing bariatric surgery. Here, we describe characteristics of the recruited SCOTS cohort, and the relationship between health and socioeconomic status with body mass index (BMI) and age. PARTICIPANTS/METHODS: 445 participants scheduled for bariatric surgery at any of 14 centres in Scotland, UK, were recruited between 2013 and 2016 for this longitudinal cohort study (1 withdrawal); 249 completed health-related preoperative patient-reported outcome measures. Regression models were used to estimate the effect of a 10-unit increase in age or BMI, adjusting for sex, smoking and socioeconomic status. RESULTS: Mean age was 46 years and median BMI was 47 kg/m2. For each 10 kg/m2 higher BMI, there was a change of -5.2 (95% CI -6.9 to -3.5; p<0.0001) in Rand 12-item Short Form Survey Physical Component Summary (SF-12 PCS), -0.1 (95% CI -0.2 to -0.1; p<0.0001) in EuroQoL 5-level EQ-5D version index score and 14.2 (95% CI 10.7 to 17.7; p<0.0001) in Impact of Weight on Quality of Life-Lite Physical Function Score. We observed a 3.1 times higher use of specialist aids and equipment at home (OR: 3.1, 95% CI 1.9 to 5.0; p<0.0001). Broadly, similar results were seen for each 10-year higher age, including a change of -2.1 (95% CI -3.7 to -0.5; p<0.01) in SF-12 PCS. CONCLUSIONS: A higher BMI combined with older age is associated with poor physical functioning and quality of life in people seeking bariatric surgery treatment. Policy-makers must consider the health and care needs of these individuals and invest to provide increased access to effective weight management. TRIAL REGISTRATION NUMBER: ISRCTN47072588.

Tackling reporting issues and variation in behavioural weight management interventions: Design and piloting of the standardized reporting of adult behavioural weight management interventions to aid evaluation (STAR-LITE) template.

In the United Kingdom, the National Institute for Health and Care Excellence make recommendations to guide the local-level selection and implementation of adult behavioural weight management interventions (BWMIs) which lack specificity. The reporting of BWMIs is generally poorly detailed, resulting in difficulties when comparing effectiveness, quality and appropriateness for participants. This non-standardized reporting makes meta-analysis of intervention data impossible, resulting in vague guidance based on weak evidence, reinforcing the urgent need for consistency and detail within BWMI description. STAR-LITE - a 4-section, 119-item standardized adult BWMI reporting template - was developed and tested using a two-phase process. After initial design, the template was piloted using adult behavioural weight management RCTs and currently implemented UK BWMI mapping information to further refine the template and examine current reporting and variance. Overall, reporting quality of weight management RCTs was poor, and large variance across different components of real-world BWMIs was observed. Non-specific guidance and wide variation in adult BWMIs are likely linked to inadequate RCT reporting quality and the inability to perform reliable comparisons of data. Future use of STAR-LITE would facilitate the consistent, detailed reporting of adult BWMIs, supporting their evaluation and comparison, to ultimately inform effective policy and improve weight management practice.

Core outcome set for behavioural weight management interventions for adults with overweight and obesity: Standardised reporting of lifestyle weight management interventions to aid evaluation (STAR-LITE).

Behavioural weight management interventions in research studies and clinical practice differ in length, advice, frequency of meetings, staff, and cost. Few real-world programmes have published patient outcomes and those that have used different ways of reporting information, making it impossible to compare interventions and develop the evidence base. To address this issue, we have developed a core outcome set for behavioural weight management intervention programmes for adults with overweight and obesity. Outcomes were identified via systematic review of the literature. A representative expert group was formed comprising people with experience of adult weight management services. An online Delphi process was employed to reach consensus as to which outcomes should be measured and reported and which definitions/instruments should be utilised. The expert group identified eight core outcomes and 12 core processes for reporting by weight management services. Eleven outcomes and five processes were identified as optional. The most appropriate definitions/instruments for measuring each outcome/process were also agreed. Our core outcome set will ensure consistency of reporting. This will allow behavioural weight management interventions to be compared, revealing which interventions work best for which members of the population and helping inform development of adult behavioural weight management interventions.

Development of a core outcome set for behavioural weight management programmes for adults with overweight and obesity: protocol for obtaining expert consensus using Delphi methodology.

INTRODUCTION: Weight management interventions in research studies and in clinical practice differ in length, advice, frequency of meetings, staff and cost. Very few real-world programmes have published patient-related outcomes, and those that have published used different ways of reporting the information, making it impossible to compare interventions and further develop the evidence base. Developing a core outcome set for behavioural weight management programmes (BWMPs) for adults with overweight and obesity will allow different BWMPs to be compared and reveal which interventions work best for which members of the population. METHODS AND ANALYSIS: An expert group, comprised of 40 people who work in, refer to, or attend BWMPs for adults with overweight and obesity, will be asked to decide which outcomes services should report. An online Delphi process will be employed to help the group reach consensus as to which outcomes should be measured and reported, and which definitions/instruments should be used in order to do so. The first stage of the Delphi process (three rounds of questionnaires) will focus on outcomes while the second stage (three additional rounds of questionnaires) will focus on definition/instrument selection. ETHICS AND DISSEMINATION: Ethical approval for this study has been received from the University of Glasgow College of Medical, Veterinary and Life Sciences Ethics Committee. With regard to disseminating results, a report will be submitted to our funding body, the Chief Scientist Office of the Scottish Government Health Department. In addition, early findings will be shared with Public Health England and Health Scotland, and results communicated via conference presentations, peer review publication and our institutions' social media platforms.

Variations in bariatric surgical care pathways: a national costing study on the variability of services and impact on costs.

BACKGROUND: We undertook a survey of all bariatric centres in Scotland in order to describe current pre- and post-operative care, to estimate their costs and explore differences in financial impact. METHODS: A questionnaire was distributed to each health centre. Descriptive statistics were used to present average cost per patient along with 95% confidence intervals, and the range of costs. RESULTS: Results show nearly a five-fold difference in costs per patient for pre-operative services (range £226 - £1071) and more than a three-fold difference for post-operative services (range £259 - £896). CONCLUSIONS: There is a lack of evidence base and a clear requirement for the evaluation of bariatric surgical services to identify the care pathways pre- and post-surgery which lead to largest improvements in health outcomes and remain cost-effective.

Clinical indices of in vivo biocompatibility: the role of ex vivo cell function studies and effluent markers in peritoneal dialysis patients.

Clinical indices of in vivo biocompatibility: The role of ex vivo cell function studies and effluent markers in peritoneal dialysis patients. Over the past 20 years, studies of the biocompatibility profile of peritoneal dialysis solutions (PDF) have evolved from initial in vitro studies assessing the impact of solutions on leukocyte function to evaluations of mesothelial cell behavior. More recent biocompatibility evaluations have involved assessments of the impact of PDF on membrane integrity and cell function in peritoneal dialysis (PD) patients. The development of ex vivo systems for the evaluation of in vivo cell function, and effluent markers of membrane integrity and inflammation in patients exposed both acutely and chronically to conventional and new PDF will be interpreted in the context of our current understanding of the biology of the dialyzed peritoneum. The available data indicate that exposure of the peritoneal environment to more biocompatible PDF is associated with improvements in peritoneal cell function, alterations in markers of membrane integrity, and reduced local inflammation. These data suggest that more biocompatible PDF will have a positive impact on host defense, peritoneal homeostasis, and the long-term preservation of peritoneal membrane function in PD patients.

Profiling of transcriptional and epigenetic changes during directed endothelial differentiation of human embryonic stem cells identifies FOXA2 as a marker of early mesoderm commitment.

INTRODUCTION: Differentiation of vascular endothelial cells (ECs) in clinically relevant numbers for injection into ischaemic areas could offer therapeutic potential in the treatment of cardiovascular conditions, including myocardial infarction, peripheral vascular disease and stroke. While we and others have demonstrated successful generation of functional endothelial-like cells from human embryonic stem cells (hESCs), little is understood regarding the complex transcriptional and epigenetic changes that occur during differentiation, in particular during early commitment to a mesodermal lineage. METHODS: We performed the first gene expression microarray study of hESCs undergoing directed differentiation to ECs using a monolayer-based, feeder-free and serum-free protocol. Microarray results were confirmed by quantitative RT-PCR and immunocytochemistry, and chromatin immunoprecipitation (ChIP)-PCR analysis was utilised to determine the bivalent status of differentially expressed genes. RESULTS: We identified 22 transcription factors specific to early mesoderm commitment. Among these factors, FOXA2 was observed to be the most significantly differentially expressed at the hESC-EC day 2 timepoint. ChIP-PCR analysis revealed that the FOXA2 transcription start site is bivalently marked with histone modifications for both gene activation (H3K4me3) and repression (H3K27me3) in hESCs, suggesting the transcription factor may be a key regulator of hESC differentiation. CONCLUSION: This enhanced knowledge of the lineage commitment process will help improve the design of directed differentiation protocols, increasing the yield of endothelial-like cells for regenerative medicine therapies in cardiovascular disease.

The Euro-Balance Trial: the effect of a new biocompatible peritoneal dialysis fluid (balance) on the peritoneal membrane.

BACKGROUND: Although peritoneal dialysis (PD) is a widely accepted form of renal replacement therapy (RRT), concerns remain regarding the bioincompatible nature of standard PD fluid. In order to evaluate whether a newly formulated fluid of neutral pH, and containing low levels of glucose degradation products (GDP), resulted in improved in vivo biocompatibility, it was compared in a clinical study to a standard PD fluid. METHODS: In a multicenter, open, randomized, prospective study with a crossover design and parallel arms, a conventional, acidic, lactate-buffered fluid (SPDF) was compared with a pH neutral, lactate-buffered, low GDP fluid (balance). Overnight effluent was collected and assayed for cancer antigen 125 (CA125), hyaluronic acid (HA), procollagen peptide (PICP), vascular endothelial growth factor (VEGF), and tumor necrosis factor alpha (TNFalpha). Serum samples were assayed for circulating advanced glycosylation end products (AGE), N(epsilon)-(carboxymethyl)lysine (CML), and imidazolone. Clinical end points were residual renal function (RRF), adequacy of dialysis, ultrafiltration, and peritoneal membrane function. Eighty-six patients were randomized to either group I starting with SPDF for 12 weeks (Phase I), then switching to "balance" for 12 weeks (Phase II), or group II, which was treated vice versa. Seventy-one patients completed the study with data suitable for entry into the per protocol analysis. Effluent and serum samples, together with peritoneal function tests and adequacy measurements, were undertaken at study centers on three occasions during the study: after the four-week run-in period, after Phase I, and again after Phase II. RESULTS: In patients treated with balance there were significantly higher effluent levels of CA125 and PICP in both arms of the study. Conversely, levels of HA were lower in patients exposed to balance, while there was no change in the levels of either VEGF or TNFalpha. Serum CML and imidazolone levels fell significantly in balance-treated patients. Renal urea and creatinine clearances were higher in both treatment arms after patients were exposed to balance. Urine volume was higher in patients exposed to balance. In contrast, peritoneal ultrafiltration was higher in patients on SPDF. When anuric patients were analyzed as a subgroup, there was no significant difference in peritoneal transport characteristics or in ultrafiltration on either fluid. There were no changes in peritonitis incidence on either solution. CONCLUSION: This study indicates that the use of balance, a neutral pH, low GDP fluid, is accompanied by a significant improvement in effluent markers of peritoneal membrane integrity and significantly decreased circulating AGE levels. Clinical parameters suggest an improvement in residual renal function on balance, with an accompanying decrease in peritoneal ultrafiltration. It would appear that balance solution results in an improvement in local peritoneal homeostasis, as well as having a positive impact on systemic parameters, including circulating AGE and residual renal function.

Continuous dialysis with bicarbonate/lactate-buffered peritoneal dialysis fluids results in a long-term improvement in ex vivo peritoneal macrophage function.

To circumvent the potentially negative consequences of long-term exposure to unphysiologic acidic lactate-buffered peritoneal dialysis fluids (PDF), neutral pH solutions buffered with bicarbonate/lactate have recently been introduced in phase 2 and 3 clinical trials. This study examines the longitudinal changes in peritoneal macrophage (PMØ) function in patients dialyzed continuously with either lactate (LPD; 40 mM lactate, pH 5.2)-buffered or bicarbonate/lactate (TBL; 25 mM/15 mM bicarbonate/lactate, pH 7.3)-buffered PDF. Before the study, during the run in period of a phase 3 clinical trial, all patients had been taking LPD for at least the previous 18 wk. At the beginning of the study (day 0), both constitutive and serum-treated zymosan (STZ) stimulated tumor necrosis factor alpha (TNF-alpha) synthesis were assessed in PMØ isolated from 12-h dwell effluent (with 1.36% glucose) in all patients. The patients were subsequently randomized to either continuous TBL or LPD therapy and PMØ function was assessed after further 3- and 6-mo periods in all patients. At all time points measured STZ induced a dose-dependent increase in PMØ TNF-alpha secretion (P = 0.043 versus control for doses greater than 100 microg/ml). In patients continuously dialyzed with LPD, constitutive PMØ TNF-alpha synthesis levels (mean +/- SEM, pg/10(6) PMØ per18 h, n = 5 patients) were 154 +/- 65, 261 +/- 60, and 101 +/- 99 at 0, 3, and 6 mo, respectively. Stimulated STZ (1000 microg/ml) levels were 1340 +/- 519, 1046 +/- 586, and 758 +/- 250 at 0, 3, and 6 mo, respectively. In patients dialyzed with TBL, constitutive PMØ TNF-alpha synthesis levels (pg/10(6) PMØ per 18 h, n = 5 patients) were 300 +/- 136, 106 +/- 35, and 213 +/- 62 at 0, 3, and 6 mo, respectively. Stimulated STZ (1000 microg/ml) levels were 1969 +/- 751, 1541 +/- 330, and 2670 +/- 671 at 0, 3, and 6 mo, respectively. At 6 mo, STZ-stimulated PMØ TNF-alpha synthesis was significantly higher in patients treated with TBL compared with those treated with LPD (P = 0.0035). These data suggest that in patients continuously dialyzed with a neutral pH solution, there is a long-term improvement in PMØ function compared with patients on conventional therapy. Better PMØ function suggests improved host defense status and may affect the peritoneum's susceptibility to infection and potentially reduce the negative consequences of repeated intraperitoneal inflammation on long-term membrane function.

Morphologic changes in the peritoneal membrane of patients with renal disease.

This study examined the morphologic features of the parietal peritoneal membranes of 130 patients undergoing peritoneal dialysis (PD) and compared them with the features of the peritoneal membranes of normal individuals, uremic predialysis patients, and patients undergoing hemodialysis. The median thickness of the submesothelial compact collagenous zone was 50 microm for normal subjects, 140 microm for uremic patients, 150 microm for patients undergoing hemodialysis, and 270 microm for patients undergoing PD (P < 0.001 for all versus normal subjects). Compact zone thickness increased significantly with the duration of PD therapy [0 to 24 mo, 180 microm (n = 58); 25 to 48 mo, 240 microm (n = 24); 49 to 72 mo, 300 microm (n = 13); 73 to 96 mo, 750 microm (n = 16); >97 mo, 700 microm (n = 19)]. Vascular changes included progressive subendothelial hyalinization, with luminal narrowing or obliteration. These changes were absent in samples from normal subjects but were present in 28% of samples from uremic patients and 56% of biopsies from patients undergoing PD. In the PD group, the prevalence of vasculopathy increased significantly with therapy duration (P = 0.0001). The density of blood vessels per unit length of peritoneum was significantly higher for patients with membrane failure and was correlated with the degree of fibrosis (P = 0.01). For the first time, a comprehensive cross-sectional analysis of the morphologic changes in the peritoneal membranes of patients undergoing PD is provided. The infrequency of fibrosis in the absence of vasculopathy suggests that vasculopathy may predispose patients to the development of fibrosis. This study provides a sufficiently large cohort of samples to allow structure-function relationships to be established, as well as providing a repository of tissue for further studies.