Chronic activation of human cardiac fibroblasts in vitro attenuates the reversibility of the myofibroblast phenotype.

Activation of cardiac fibroblasts and differentiation to myofibroblasts underlies development of pathological cardiac fibrosis, leading to arrhythmias and heart failure. Myofibroblasts are characterised by increased α-smooth muscle actin (α-SMA) fibre expression, secretion of collagens and changes in proliferation. Transforming growth factor-beta (TGF-ß) and increased mechanical stress can initiate myofibroblast activation. Reversibility of the myofibroblast phenotype has been observed in murine cells but has not been explored in human cardiac fibroblasts. In this study, chronically activated adult primary human ventricular cardiac fibroblasts and human induced pluripotent stem cell derived cFbs (hiPSC-cFbs) were used to investigate the potential for reversal of the myofibroblast phenotype using either subculture on soft substrates or TGF-ß receptor inhibition. Culture on softer plates (25 or 2 kPa Young's modulus) did not alter proliferation or reduce expression of α-SMA and collagen 1. Similarly, culture of myofibroblasts in the presence of TGF-ß inhibitor did not reverse myofibroblasts back to a quiescent phenotype. Chronically activated hiPSC-cFbs also showed attenuated response to TGF-ß receptor inhibition and inability to reverse to quiescent fibroblast phenotype. Our data demonstrate substantial loss of TGF-ß signalling plasticity as well as a loss of feedback from the surrounding mechanical environment in chronically activated human myofibroblasts.

Hypertension and cardiomyopathy associated with chronic kidney disease: epidemiology, pathogenesis and treatment considerations.

Chronic kidney disease (CKD) is a complex condition with a prevalence of 10-15% worldwide. An inverse-graded relationship exists between cardiovascular events and mortality with kidney function which is independent of age, sex, and other risk factors. The proportion of deaths due to heart failure and sudden cardiac death increase with progression of chronic kidney disease with relatively fewer deaths from atheromatous, vasculo-occlusive processes. This phenomenon can largely be explained by the increased prevalence of CKD-associated cardiomyopathy with worsening kidney function. The key features of CKD-associated cardiomyopathy are increased left ventricular mass and left ventricular hypertrophy, diastolic and systolic left ventricular dysfunction, and profound cardiac fibrosis on histology. While these features have predominantly been described in patients with advanced kidney disease on dialysis treatment, patients with only mild to moderate renal impairment already exhibit structural and functional changes consistent with CKD-associated cardiomyopathy. In this review we discuss the key drivers of CKD-associated cardiomyopathy and the key role of hypertension in its pathogenesis. We also evaluate existing, as well as developing therapies in the treatment of CKD-associated cardiomyopathy.

Changes in left ventricular structure and function associated with renal transplantation: a systematic review and meta-analysis.

AIMS: This study aimed to examine if the cardiac changes associated with uraemic cardiomyopathy are reversed by renal transplantation. METHODS AND RESULTS: MEDLINE, Embase, OpenGrey, and the Cochrane Library databases were searched from 1950 to March 2020. The primary outcome measure was left ventricular mass index. Secondary outcome measures included left ventricular dimensions and measures of diastolic and systolic function. Studies were included if they used any imaging modality both before and after successful renal transplantation. Data were analysed through meta-analysis approaches. Weight of evidence was assessed through the Grading of Recommendations Assessment, Development and Evaluation system. Twenty-three studies used echocardiography, and three used cardiac magnetic resonance imaging as their imaging modality. The methodological quality of the evidence was generally poor. Four studies followed up control groups, two using cardiac magnetic resonance imaging and two using echocardiography. Meta-analysis of these studies indicated that there was no difference in left ventricular mass index between groups following transplantation {standardized mean difference -0.07 [95% confidence interval (CI) -0.41 to 0.26]; P = 0.67}. There was also no difference observed in left ventricular ejection fraction [mean difference 0.39% (95% CI -4.09% to 4.87%); P = 0.86] or left ventricular end-diastolic volume [standardized mean difference -0.24 (95% CI -0.94 to 0.45); P = 0.49]. Inconsistent reporting of changes in diastolic dysfunction did not allow for any meaningful analysis or interpretation. CONCLUSIONS: The evidence does not support the notion that uraemic cardiomyopathy is reversible by renal transplantation. However, the evidence is limited by methodological weaknesses, which should be considered when interpreting these findings.

Coronary microvascular dysfunction is associated with degree of anaemia in end-stage renal disease.

BACKGROUND: Coronary microvascular dysfunction (CMD) is common in end-stage renal disease (ESRD) and is an adverse prognostic marker. Coronary flow velocity reserve (CFVR) is a measure of coronary microvascular function and can be assessed using Doppler echocardiography. Reduced CFVR in ESRD has been attributed to factors such as diabetes, hypertension and left ventricular hypertrophy. The contributory role of other mediators important in the development of cardiovascular disease in ESRD has not been studied. The aim of this study was to examine the prevalence of CMD in a cohort of kidney transplant candidates and to look for associations of CMD with markers of anaemia, bone mineral metabolism and chronic inflammation. METHODS: Twenty-two kidney transplant candidates with ESRD were studied with myocardial contrast echocardiography, Doppler CFVR assessment and serum multiplex immunoassay analysis. Individuals with diabetes, uncontrolled hypertension or ischaemic heart disease were excluded. RESULTS: 7/22 subjects had CMD (defined as CFVR < 2). Demographic, laboratory and echocardiographic parameters and serum biomarkers were similar between subjects with and without CMD. Subjects with CMD had significantly lower haemoglobin than subjects without CMD (102 g/L ± 12 vs. 117 g/L ± 11, p = 0.008). There was a positive correlation between haemoglobin and CFVR (r = 0.7, p = 0.001). Similar results were seen for haematocrit. In regression analyses, haemoglobin was an independent predictor of CFVR (ß = 0.041 95% confidence interval 0.012-0.071, p = 0.009) and of CFVR < 2 (odds ratio 0.85 95% confidence interval 0.74-0.98, p = 0.022). CONCLUSIONS: Among kidney transplant candidates with ESRD, there is a high prevalence of CMD, despite the absence of traditional risk factors. Anaemia may be a potential driver of microvascular dysfunction in this population and requires further investigation.

Acute kidney injury is more common in men than women after accounting for socioeconomic status, ethnicity, alcohol intake and smoking history.

BACKGROUND: The association of several comorbidities, including diabetes mellitus, hypertension, cardiovascular disease, heart failure and chronic kidney or liver disease, with acute kidney injury (AKI) is well established. Evidence on the effect of sex and socioeconomic factors are scarce. This study was designed to examine the association of sex and socioeconomic factors with AKI and AKI-related mortality and further to evaluate the additional relationship with other possible risk factors for AKI occurrence. METHODS: We included 3534 patients (1878 males with mean age 61.1 ± 17.7 and 1656 females 1656 with mean age 60.3 ± 20.0 years) admitted to Queen Elizabeth or Heartlands Hospitals, Birmingham, between October 2013 and January 2016. Patients were prospectively followed-up for a median 47.70 [IQR, 18.20] months. Study-endpoints were incidence of AKI, based on KDIGO-AKI Guidelines, and all-cause mortality. Data acquisition was automated, and information on mortality was collected from the Hospital Episode Statistics and Office of National Statistics. Socioeconomic status was evaluated with the Index of Multiple Deprivation (IMD). RESULTS: Incidence of AKI was higher in men compared to women (11.3% vs 7.1%; P < 0.001). Model regression analysis revealed significant association of male sex with higher AKI risk (OR, 1.659; 95% CI, 1.311-2.099; P < 0.001); this association remained significant after adjustment for age, eGFR, IMD, smoking, alcohol consumption, ethnicity, existing comorbidities and treatment (OR, 1.599; 95% CI, 1.215-2.103; P = 0.001). All-cause mortality was higher in patients with compared to those without AKI. Males with AKI had higher mortality rates in the first 6-month and 1-year periods after the index AKI event. The association of male sex with mortality was independent of socioeconomic factors but was not statistically significant after adjustment for existing comorbidities. CONCLUSIONS: Men are at higher risk of AKI and this association is independent from existing risk factors for AKI. The association between male sex and AKI-related mortality was not independent from existing comorbidities. A better understanding of factors associated with AKI may help accurately identify high-risk patients.

Early renal function trajectories, cytomegalovirus serostatus and long-term graft outcomes in kidney transplant recipients.

BACKGROUND: Improved recognition of factors influencing graft survival has led to better short-term kidney transplant outcomes. However, efforts to prevent long-term graft decline and improve graft survival have seen more modest improvements. The adoption of electronic health records has enabled better recording and identification of donor-recipient factors through the use of modern statistical techniques. We have previously shown in a prevalent renal transplant population that episodes of rapid deterioration are associated with graft loss. METHODS: Estimated glomerular filtration rates (eGFR) between 3 and 27 months after transplantation were collected from 310 kidney transplant recipients. We utilised a Bayesian approach to estimate the most likely eGFR trajectory as a smooth curve from an average of 10,000 Monte Carlo samples. The probability of having an episode of rapid deterioration (decline greater than 5 ml/min/1.73 m2 per year in any 1-month period) was calculated. Graft loss and mortality data was collected over a median follow-up period of 8 years. Factors associated with having an episode of rapid deterioration and associations with long-term graft loss were explored. RESULTS: In multivariable Cox Proportional Hazard analysis, a probability greater than 0.8 of rapid deterioration was associated with long-term death-censored graft loss (Hazard ratio 2.17; 95% Confidence intervals [CI] 1.04-4.55). In separate multivariable logistic regression models, cytomegalovirus (CMV) serostatus donor positive to recipient positive (Odds ratio [OR] 3.82; 95%CI 1.63-8.97), CMV donor positive (OR 2.06; 95%CI 1.15-3.68), and CMV recipient positive (OR 2.03; 95%CI 1.14-3.60) were associated with having a greater than 0.8 probability of an episode of rapid deterioration. CONCLUSIONS: Early episodes of rapid deterioration are associated with long-term death-censored graft loss and are associated with cytomegalovirus seropositivity. Further study is required to better manage these potentially modifiable risks factors and improve long-term graft survival.

Quantification of fibroblast growth factor 23 and N-terminal pro-B-type natriuretic peptide to identify patients with atrial fibrillation using a high-throughput platform: A validation study.

BACKGROUND: Large-scale screening for atrial fibrillation (AF) requires reliable methods to identify at-risk populations. Using an experimental semi-quantitative biomarker assay, B-type natriuretic peptide (BNP) and fibroblast growth factor 23 (FGF23) were recently identified as the most suitable biomarkers for detecting AF in combination with simple morphometric parameters (age, sex, and body mass index [BMI]). In this study, we validated the AF model using standardised, high-throughput, high-sensitivity biomarker assays. METHODS AND FINDINGS: For this study, 1,625 consecutive patients with either (1) diagnosed AF or (2) sinus rhythm with CHA2DS2-VASc score of 2 or more were recruited from a large teaching hospital in Birmingham, West Midlands, UK, between September 2014 and February 2018. Seven-day ambulatory ECG monitoring excluded silent AF. Patients with tachyarrhythmias apart from AF and incomplete cases were excluded. AF was diagnosed according to current clinical guidelines and confirmed by ECG. We developed a high-throughput, high-sensitivity assay for FGF23, quantified plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) and FGF23, and compared results to the previously used multibiomarker research assay. Data were fitted to the previously derived model, adjusting for differences in measurement platforms and known confounders (heart failure and chronic kidney disease). In 1,084 patients (46% with AF; median [Q1, Q3] age 70 [60, 78] years, median [Q1, Q3] BMI 28.8 [25.1, 32.8] kg/m2, 59% males), patients with AF had higher concentrations of NT-proBNP (median [Q1, Q3] per 100 pg/ml: with AF 12.00 [4.19, 30.15], without AF 4.25 [1.17, 15.70]; p < 0.001) and FGF23 (median [Q1, Q3] per 100 pg/ml: with AF 1.93 [1.30, 4.16], without AF 1.55 [1.04, 2.62]; p < 0.001). Univariate associations remained after adjusting for heart failure and estimated glomerular filtration rate, known confounders of NT-proBNP and FGF23. The fitted model yielded a C-statistic of 0.688 (95% CI 0.656, 0.719), almost identical to that of the derived model (C-statistic 0.691; 95% CI 0.638, 0.744). The key limitation is that this validation was performed in a cohort that is very similar demographically to the one used in model development, calling for further external validation. CONCLUSIONS: Age, sex, and BMI combined with elevated NT-proBNP and elevated FGF23, quantified on a high-throughput platform, reliably identify patients with AF. TRIAL REGISTRATION: Registry IRAS ID 97753 Health Research Authority (HRA), United Kingdom.

Cardiovascular Effects of Unilateral Nephrectomy in Living Kidney Donors at 5 Years.

[Figure: see text].

The effect of admission and pre-admission serum creatinine as baseline to assess incidence and outcomes of acute kidney injury in acute medical admissions.

BACKGROUND: Acute kidney injury (AKI) in hospital-admitted patients is a common complication associated with increased mortality. The diagnosis of AKI relies on the ascertainment of peak increase in serum creatinine (SCr). This study evaluated the incidence of AKI using the increase from mean 7-365 days pre-admission (AKIpre) and admission (AKIadm) SCr levels, and examined the associations of AKI and changes in SCr levels with all-cause mortality. METHODS: A total of 2436 patients admitted to a tertiary hospital were recruited and followed-up for a median of 47.70 (interquartile range 18.20) months. AKI incidence and severity were defined according to the Kidney Disease: Improving Global Outcomes-AKI Guidelines. Follow-up data were collected from the Hospital Episode Statistics and Office of National Statistics. Mortality was evaluated during a short- (30 days), mid- (1 year) and long-term (4 years) period. RESULTS: No difference in the AKI rates using AKIpre and AKIadm (12.5% versus 12.2%; P = 0.695) or in the AKI severity (P = 0.261) was evident. Agreement between the two definitions was modest (Kappa-statistic = 0.596, P < 0.001). Patients with AKIpre or AKIadm had increased all-cause mortality compared with those without AKI during all follow-up periods. In fully adjusted regression analysis, AKIpre [hazard ratio (HR) = 2.226, 95% confidence interval (CI) 1.140-4.347; P = 0.027] and AKIadm (HR = 2.105, 95% CI 1.090-4.064; P = 0.027) remained associated with 30-day mortality. Results for the 1- and 4-year periods were similar. Increases of >4.00 µmol/L and >6.06% from pre-admission or >6.00 µmol/L and >17.24% from admission SCr levels presented increased mortality risk during follow-up. CONCLUSIONS: Use of admission or pre-admission SCr provides similar incidence rates, but they diagnose different sets of patients. Even minor increases in SCr, below those required for the classification of AKI, were associated with increased mortality. These findings can help the clinicians to identify patients at higher risk for adverse outcomes.

Changes in Blood Pressure and Arterial Hemodynamics following Living Kidney Donation.

BACKGROUND AND OBJECTIVES: The Effect of a Reduction in GFR after Nephrectomy on Arterial Stiffness and Central Hemodynamics (EARNEST) study was a multicenter, prospective, controlled study designed to investigate the associations of an isolated reduction in kidney function on BP and arterial hemodynamics. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Prospective living kidney donors and healthy controls who fulfilled criteria for donation were recruited from centers with expertise in vascular research. Participants underwent office and ambulatory BP measurement, assessment of arterial stiffness, and biochemical tests at baseline and 12 months. RESULTS: A total of 469 participants were recruited, and 306 (168 donors and 138 controls) were followed up at 12 months. In the donor group, mean eGFR was 27 ml/min per 1.73 m2 lower than baseline at 12 months. Compared with baseline, at 12 months the mean within-group difference in ambulatory day systolic BP in donors was 0.1 mm Hg (95% confidence interval, -1.7 to 1.9) and 0.6 mm Hg (95% confidence interval, -0.7 to 2.0) in controls. The between-group difference was -0.5 mm Hg (95% confidence interval, -2.8 to 1.7; P=0.62). The mean within-group difference in pulse wave velocity in donors was 0.3 m/s (95% confidence interval, 0.1 to 0.4) and 0.2 m/s (95% confidence interval, -0.0 to 0.4) in controls. The between-group difference was 0.1 m/s (95% confidence interval, -0.2 to 0.3; P=0.49). CONCLUSIONS: Changes in ambulatory peripheral BP and pulse wave velocity in kidney donors at 12 months after nephrectomy were small and not different from controls. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: NCT01769924 (https://clinicaltrials.gov/ct2/show/NCT01769924).

Coronary flow velocity reserve and inflammatory markers in living kidney donors.

BACKGROUND: Coronary microvascular dysfunction is prevalent in chronic kidney disease (CKD), and may contribute to the development of myocardial dysfunction in CKD. Coronary flow velocity reserve (CFVR) is a marker of coronary microvascular function and falls with increasing CKD stage. Living kidney donors have renal function consistent with early stage CKD and concern has been raised about their cardiovascular risk. No studies to date have investigated the presence of coronary microvascular dysfunction in living kidney donors. METHODS: 25 healthy controls and 23 living kidney donors were recruited and underwent assessment with transthoracic echocardiography, Doppler CFVR, myocardial contrast echocardiography and serum multiplex immunoassay panels. RESULTS: Doppler CFVR was significantly reduced in living kidney donors compared to controls (mean CFVR 3.4 ± 0.7 vs 3.8 ± 0.6, mean difference 0.4 95% confidence interval 0.03-0.8, p =.036). Quantitative myocardial contrast echocardiography showed a trend towards reduced coronary flow reserve in living kidney donors. Compared to controls, living kidney donors had higher serum high sensitivity C reactive peptide (hsCRP) and lower levels of uromodulin. CONCLUSIONS: This is the first study of CFVR in living kidney donors. We have shown that the modest drop in estimated glomerular filtration rate in living kidney donors is associated with lower values of Doppler CFVR compared to controls, suggesting that isolated reductions in renal function may lead to altered microvascular function. The increase in hsCRP and reduction in uromodulin suggests that chronic subclinical inflammation may contribute to altered microvascular function in this population.

Clinical Potential of Targeting Fibroblast Growth Factor-23 and αKlotho in the Treatment of Uremic Cardiomyopathy.

Chronic kidney disease is highly prevalent, affecting 10% to 15% of the adult population worldwide and is associated with increased cardiovascular morbidity and mortality. As chronic kidney disease worsens, a unique cardiovascular phenotype develops characterized by heart muscle disease, increased arterial stiffness, atherosclerosis, and hypertension. Cardiovascular risk is multifaceted, but most cardiovascular deaths in patients with advanced chronic kidney disease are caused by heart failure and sudden cardiac death. While the exact drivers of these deaths are unknown, they are believed to be caused by uremic cardiomyopathy: a specific pattern of myocardial hypertrophy, fibrosis, with both diastolic and systolic dysfunction. Although the pathogenesis of uremic cardiomyopathy is likely to be multifactorial, accumulating evidence suggests increased production of fibroblast growth factor-23 and αKlotho deficiency as potential major drivers of cardiac remodeling in patients with uremic cardiomyopathy. In this article we review the increasing understanding of the physiology and clinical aspects of uremic cardiomyopathy and the rapidly increasing knowledge of the biology of both fibroblast growth factor-23 and αKlotho. Finally, we discuss how dissection of these pathological processes is aiding the development of therapeutic options, including small molecules and antibodies, directly aimed at improving the cardiovascular outcomes of patients with chronic kidney disease and end-stage renal disease.

Anticoagulant strategies for the patient with chronic kidney disease.

Chronic kidney disease (CKD) is a global health problem affecting up to 14% of the adult population in developed countries. On the basis of current guidelines, patients with CKD will often fulfil criteria for both short-term and long-term anticoagulation. Paradoxically, patients with CKD are not only at a higher risk of thrombosis, they are also at increased risk of bleeding. Furthermore, the pharmacokinetics and pharmacodynamics of many anticoagulant therapies are significantly affected by renal dysfunction. In addition, patients with advanced CKD are often systematically excluded from major clinical trials. As such, the decision on whether to anticoagulate or not, and if so with what agent, poses significant challenges. A solid understanding of the condition in question and the available treatments is required to make an informed judgement call. An in-depth appreciation of the advantages and disadvantages of the currently available anticoagulants is a key element in the decision-making process.

Coronary microvascular dysfunction: a key step in the development of uraemic cardiomyopathy?

The syndrome of uraemic cardiomyopathy, characterised by left ventricular hypertrophy, diffuse fibrosis and systolic and diastolic dysfunction, is common in chronic kidney disease and is associated with an increased risk of cardiovascular morbidity and mortality. The pathophysiological mechanisms leading to uraemic cardiomyopathy are not fully understood. We suggest that coronary microvascular dysfunction may be a key mediator in the development of uraemic cardiomyopathy, a phenomenon that is prevalent in other myocardial diseases that share phenotypical similarities with uraemic cardiomyopathy such as hypertrophic cardiomyopathy and heart failure with preserved ejection fraction. Here, we review the current understanding of uraemic cardiomyopathy, highlight different methods of assessing coronary microvascular function and evaluate the current evidence for coronary microvascular dysfunction in chronic kidney disease.

Dialysis Following Transcatheter Aortic Valve Replacement: Risk Factors and Outcomes: An Analysis From the UK TAVI (Transcatheter Aortic Valve Implantation) Registry.

OBJECTIVES: This study sought to determine the risk factors for post-transcatheter aortic valve replacement (TAVR) dialysis and to determine the impact of pre-TAVR or post-TAVR dialysis on mortality. BACKGROUND: TAVR is now established as an alternative treatment to surgical aortic valve replacement. Data examining the impact of dialysis on outcomes after TAVR are lacking. METHODS: The UK TAVI (Transcatheter Aortic Valve Implantation) Registry was established to report outcomes on all TAVR procedures performed within the United Kingdom (2007 to 2014). Data were collected prospectively on 6,464 patients with a median follow-up of 625 days. RESULTS: The proportion of patients on dialysis before TAVR has remained constant at 1.8%. After TAVR, the proportion of patients newly needing dialysis after TAVR has fallen from 6.1% (2007 to 2008) to 2.3% (2013 to 2014). The risk of new dialysis requirement after TAVR was independently associated with lower baseline renal function, year of procedure, impaired left ventricular function, diabetes, use of an Edwards valve, a nontransfemoral approach, need for open surgery, and moderate-to-severe aortic regurgitation after the procedure. Requirement for new dialysis after TAVR was associated with higher mortality at 30 days (hazard ratio: 6.44; 95% confidence interval: 4.87 to 8.53) and at 4 years (hazard ratio: 3.54; 95% confidence interval: 2.99 to 4.19; p < 0.001 for all) compared with patients without dialysis requirement. CONCLUSIONS: The proportion of patients needing dialysis after TAVR has decreased over time. Post-TAVR dialysis is associated with increased mortality. Factors identified with dialysis requirement after TAVR require further investigation.

Impact of socioeconomic deprivation on the development of diabetic retinopathy: a population-based, cross-sectional and longitudinal study over 12 years.

OBJECTIVE: To study the association between socioeconomic deprivation and prevalence of diabetic retinopathy (DR). DESIGN: Population-based, cross-sectional observational study and retrospective longitudinal analysis over 12 years. SETTING: Primary care, East of Scotland. METHODS: Outcome data from DR screening examinations (digital retinal photography) were collected from the Scottish regional diabetes electronic record from inception of database to December 2012. The overall Scottish Index of Multiple Deprivation (SIMD) 2012 score for each patient was obtained using their residential postcode. Multiple binary logistic regression was used to analyse the relationship between overall SIMD score and prevalence of DR, adjusting for other variables: age, gender, glycated haemoglobin, cholesterol levels and duration of disease. PRIMARY OUTCOME: Any retinopathy (R1 and above) in either eye. RESULTS: A total of 1861 patients with type 1 diabetes mellitus (DM) and 18,197 patients with type 2 DM were included in the study. Prevalence of DR in type 1 and type 2 DM were 56.3% and 25.5%, respectively. Increased prevalence of DR in type 1 DM was associated with higher overall SIMD score (p=0.002), with an OR for the most deprived relative to the least deprived of 2.40 (95% CI 1.36 to 4.27). In type 2 DM, the overall SIMD score was not significantly associated with increased prevalence of DR, with an OR for the most deprived relative to the least deprived of 0.85 (95% CI 0.71 to 1.02, p=0.07). CONCLUSIONS: Socioeconomic deprivation is associated with increased prevalence of DR in patients with type 1 DM and this occurs earlier. This highlights the need for targeted interventions to address inequalities in eye healthcare.

Differential pattern of RP1 mutations in retinitis pigmentosa.

PURPOSE: Retinitis pigmentosa 1 (RP1) is a major gene responsible for both autosomal dominant and autosomal recessive retinitis pigmentosa (RP). We have previously identified three disease-causing mutations out of 174 RP patients. In this study, we investigated a new cohort of Chinese RP patients to further evaluate the contribution of RP1 mutations to cause RP. METHODS: A group of 55 nonsyndromic RP patients, the majority of them isolated cases or without information on family history, were screened for mutations in the entire coding sequences of RP1, using direct DNA sequencing. All detected variants were genotyped in 190 controls, while the three putative mutations were additionally genotyped in 362 controls subjects. Web-based programs, including PolyPhen, Sorting Intolerant from Tolerant (SIFT), Prediction of Pathological Mutations (PMUT), Single Amino Acid Polymorphism Disease-Association Predictor (SAP), ScanProsite, and ClustalW2, were used to predict the potential functional and structural impacts of the missense variants on RP1. RESULTS: A total of 14 sequence changes were identified. Among them, five were novel and found only in the RP patients. Two missense variants (p.K1370E and p.R1652L), which are conserved in primates, were predicted to have functional and structural impacts on the RP1 protein. The other three variants (c.787+34T>C, p.I408L and p.L2015L) were considered benign. CONCLUSIONS: If these two novel missense variants are in fact pathogenic, then RP1 mutations account for approximately 2.18% (5/229) of RP cases in our Chinese cohort; this is similar to other ethnic groups. However, a relatively higher frequency of missense mutations found in the Chinese patients may suggest an ethnic diversity in the RP1 mutation patterns.