Amandio Rocha-Sousa

New Therapeutic Targets for Intraocular Pressure Lowering

Primary open-angle glaucoma (POAG) is a leading cause of irreversible and preventable blindness and ocular hypertension is the strongest known risk factor. With current classes of drugs, management of the disease focuses on lowering intraocular pressure (IOP). Despite of their use to modify the course of the disease, none of the current medications for POAG is able to reduce the IOP by more than 25%–30%. Also, some glaucoma patients show disease progression despite of the therapeutics. This paper examines the new described physiological targets for reducing the IOP. The main cause of elevated IOP in POAG is thought to be an increased outflow resistance via the pressure-dependent trabecular outflow system, so there is a crescent interest in increasing trabecular meshwork outflow by extracellular matrix remodeling and/or by modulation of contractility/TM cytoskeleton disruption. Modulation of new agents that act mainly on trabecular meshwork outflow may be the future hypotensive treatment for glaucoma patients. There are also other agents in which modulation may decrease aqueous humour production or increase uveoscleral outflow by different mechanisms from those drugs available for glaucoma treatment. Recently, a role for the ghrelin-GHSR system in the pathophysiology modulation of the anterior segment, particularly regarding glaucoma, has been proposed.

A genetic case-control study confirms the implication of SMAD7 and TNF locus in the development of proliferative vitreoretinopathy.

PURPOSE Proliferative vitreoretinopathy (PVR) is still the major cause of failure of retinal detachment (RD) surgery and although the risk for developing this complication is associated with some clinical characteristics, the correlation is far from absolute, raising the possibility of genetic susceptibility. The objective of this study was to analyze the genetic contribution to PVR in patients undergoing RD surgery, the Retina 4 Project. METHODS A candidate gene association study was conducted in 2006 in a Spanish population of 450 patients suffering from primary rhegmatogenous RD. Replication was carried out in a larger population undergoing RD surgery at several European centers among 546 new patients. Single nucleotide polymorphism (SNP) of 30 genes known to be involved with inflammation were analyzed. For replication stage, those genes previously detected as significantly associated with PVR were genotyped. Distribution of allelic and haplotypic frequencies in case and control group were analyzed. Single and haplotypic analysis were assessed. The Rosenberg two-stage method was used to correct for single and multiple analyses. RESULTS After correction for multiple comparisons, four genes were significantly associated with PVR: SMAD7 (P = 0.004), PIK3CG (P = 0.009), TNF locus (P = 0.0005), and TNFR2 (P = 0.019) In the European sample, replication was observed in SMAD7 (P = 0.047) and the TNF locus (P = 0.044). CONCLUSIONS These results confirm the genetic contribution to PVR and the implication of SMAD7 and TNF locus in the development of PVR. This finding may have implications for understanding the mechanisms of PVR and could provide a potential new therapeutic target for PVR prophylaxis.

The p53 codon 72 polymorphism (rs1042522) is associated with proliferative vitreoretinopathy: the Retina 4 Project.

PURPOSE To compare the distribution of a p53 gene polymorphism among European subjects undergoing primary retinal detachment (RD) surgery in relation to the development of proliferative vitreoretinopathy (PVR). DESIGN Case-controlled gene association study conducted as a component of the Retina 4 Project (a European multicenter study). PARTICIPANTS AND CONTROLS Five hundred fifty DNA samples, 134 with PVR secondary to primary RD and 416 with RD without PVR. METHODS The p53 codon 72 polymorphism (rs1042522) was analyzed using allele-specific primer polymerase chain reaction. Proportions of genotypes and the proline (Pro-P) homozygote groups between subsamples from different countries were analyzed in 2 phases. In the first, subsamples from Spain and Portugal were analyzed. After significant results were found, samples from the United Kingdom (UK) and The Netherlands were analyzed (second phase). Genotypic and allelic frequencies were compared between cases and controls in the global sample. MAIN OUTCOME MEASURES Single significant associations with PVR. RESULTS A significant difference (P<0.05, Fisher exact test) was observed regarding the p53 genotype frequencies at codon 72 between the PVR cases and the non-PVR controls in Spain and Portugal (phase I), but not in the UK or The Netherlands (phase II). Analysis of Pro homozygote carriers between cases and controls revealed differences in Spain (29.01-42.18 and 2.29-10.20, respectively), Portugal (10.49-29.50 and 1.35-8.89, respectively), and The Netherlands (16.49-31.70 and 4.51-15.09, respectively), but no differences in the UK (7.68-18.1 and 4.85-13.94, respectively). The odds ratio of Pro carriers from Spain and Portugal together was 8.12 (95% confidence interval [CI], 3.72-17.69; P<0.05), whereas the odds ratio of Pro carriers from the UK and The Netherlands was 2.12 (95% CI, 0.96-4.68; P = 0.07). All control samples were in Hardy-Weinberg equilibrium. Considering the entire sample, significant differences were found in genotype frequencies between cases (RR, 30.59%; RP, 43.28%; PP, 26.11% [R = Arg; P = Pro]) and controls (RR, 39.66%; RP, 52.64%; PP, 7.69%) and in Pro homozygote carriers between controls (Pro homozygote 95% CI, 18.67-33.52) and cases (Pro homozygote 95% CI, 5.1-10.2). CONCLUSIONS Results indicate that the Pro variant of p53 codon 72 polymorphism is associated with a higher risk of PVR developing after a primary RD. Further studies are necessary to understand the role of this polymorphism in the development of PVR.

The T309G MDM2 gene polymorphism is a novel risk factor for proliferative vitreoretinopathy.

Proliferative vitreoretinopathy (PVR) is still the major cause of failure in retinal detachment (RD) surgery. It is believed that down-regulation in the p53 pathway could be an important key in PVR pathogenesis. The purpose was to evaluate the impact of T309G MDM2 polymorphism (rs2279744) in PVR. Distribution of T309G MDM2 genotypes among European subjects undergoing RD surgery was evaluated. Proportions of genotypes between subsamples from different countries were analyzed. Also, a genetic interaction between rs2279744 in MDM2 and rs1042522 in p53 gene was analyzed. Significant differences were observed comparing MDM2 genotype frequencies at position 309 of intron 1 between cases (GG: 21.6%, TG: 54.5%, TT: 23.8%) and controls (GG: 7.3%, TG: 43.9%, TT: 48.7%). The proportions of genotypes between sub-samples from different countries showed a significant difference. Distribution of GG genotype revealed differences in Spain (35.1–53.0)/(22.6–32.9), Portugal (39.0–74.4)/(21.4–38.9), Netherlands (40.6–66.3)/(25.3–38.8) and UK (37.5–62.4)/(23.3–34.2). The OR of G carriers in the global sample was 5.9 (95% CI: 3.2 to 11.2). The OR of G carriers from Spain and Portugal was 5.4 (95% CI: 2.2–12.7), whereas in the UK and the Netherlands was 7.3 (95% CI: 2.8–19.1). Results indicate that the G allele of rs2279744 is associated with a higher risk of developing PVR in patients undergoing a RD surgery. Further studies are necessary to understand the role of this SNP in the development of PVR.

Predicting proliferative vitreoretinopathy: temporal and external validation of models based on genetic and clinical variables

Purpose To validate three models for predicting proliferative vitreoretinopathy (PVR) based on the analysis of genotypic data and relevant clinical characteristics. Methods The validation series consisted of data from 546 patients operated on from primary rhegmatogenous retinal detachment (RRD) coming from centres in the Netherlands, Portugal, Spain and the UK. Temporal and geographical validation was performed. The discrimination capability of each model was analysed and compared with the original series, using a receiver operating curve. Then, clinical variables were combined in order to improve the predictive capability. A risk reclassification analysis was performed with and without each one of the variables. Reclassification of patients was compared and models were readjusted in the original series. Readjusted models were further validated. Results One of the models showed good predictability in the temporal sample as well as in the original series (area under the curve (AUC) original=0.7352; AUC temporal=0.6457, 95% CI 50.17 to 78.97). When clinical variables were included, only pre-existent PVR improves the predictability of this model in the validation series (temporal and geographical samples) (AUC original=0.7940 vs AUC temporal=0.7744 and AUC geographical=0.7152). The other models showed acceptable AUC values when clinical variables were included although they were less accurate than in the original series. Conclusions Genetic profiling of patients with RRD can improve the predictability of PVR in addition to the well-known clinical biomarkers. This validated formula could be a new tool in our current clinical practice in order to identify those patients at high risk of developing PVR.

BAX and BCL-2 polymorphisms, as predictors of proliferative vitreoretinopathy development in patients suffering retinal detachment: the Retina 4 project.

To compare the distribution of BCL‐2 ‐938C>A (rs2279115) and BAX ‐248G>A (rs4645878) genotypes among European subjects undergoing rhegmatogenous retinal detachment (RRD) surgery in relation to the further development of proliferative vitreoretinopathy (PVR).

Diabetes, Ghrelin And Related Peptides: From Pathophysiology To Vasculopathy

Ghrelin and obestatin are two different peptides originated from the same gene isolated in the stomach. Numer- ous actions have been described where these two peptides are implicated in metabolism, appetite regulation, glucose lev- els regulation, and a wide range of systemic effects. In this article, we summarize (1) the cellular receptors implicated in ghrelin and obestatin effects; (2) the role of ghrelin and obestatin in metabolism and appetite regulation; (3) their role in the glucose homeostasis regulation and its implication in diabetes patho-physiology; (5) the effects of ghrelin and obes- tatin in regulation of normal angiogenesis and (6) their possible role in the regulation of diabetes-induced pathologic angi- ogenesis.

Predicting participation of people with impaired vision in epidemiological studies

BackgroundThe characteristics of the target group and the design of an epidemiologic study, in particular the recruiting methods, can influence participation. People with vision impairment have unique characteristics because those invited are often elderly and totally or partially dependent on help to complete daily activities such as travelling to study sites. Therefore, participation of people with impaired vision in studies is less predictable than predicting participation for the general population.MethodsParticipants were recruited in the context of a study of prevalence and costs of visual impairment in Portugal (PCVIP-study). Participants were recruited from 4 Portuguese public hospitals. Inclusion criteria were: acuity in the better eye from 0.5 decimal (0.30logMAR) or worse and/or visual field of less than 20 degrees. Recruitment involved sending invitation letters and follow-up phone calls. A multiple logistic regression model was used to assess determinants of participation. The J48 classifier, chi-square and Fisher’s exact tests were applied to investigate the possible differences between subjects in our sample.ResultsIndividual cases were divided into 3 groups: immediate, late and non-participants. A participation rate of 20% was obtained (15% immediate, 5% late). Factors positively associated with participation included years of education, annual hospital attendance, and intermediate visual acuity. Females and greater distance to the hospital were inversely associated with participation.ConclusionIn our study, a letter followed by a phone call was efficient to recruit a significant number of participants from a larger group of people with impaired vision. However, the improvement in participation observed after the phone call might not be cost-effective. People with low levels of education and women were more difficult to recruit. These findings need to be considered to avoid studies whose results are biased by gender or socio-economic inequalities of their participants. Young subjects and those at intermediate stages of vision impairment, or equivalent conditions, may need more persuasion than other profiles.