Skip to main content
NCBI home page
Scientific Reports logoLink to Scientific Reports
. 2015 Mar 30;5:9497. doi: 10.1038/srep09497

Association of PEDF polymorphisms with age-related macular degeneration and polypoidal choroidal vasculopathy: a systematic review and meta-analysis

Li Ma 1, Shu Min Tang 1, Shi Song Rong 1, Haoyu Chen 3, Alvin L Young 1,2, Govindasamy Kumaramanickavel 4, Chi Pui Pang 1,2,3, Li Jia Chen 1,2,a
PMCID: PMC4377572  PMID: 25820866

Abstract

This study assesses the association of the pigment epithelium-derived factor (PEDF) gene with age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV). Publications in MEDLINE and EMBASE up to 21/08/2014 were searched for case-control association studies of PEDF with AMD and/or PCV. Reported studies giving adequate genotype and/or allele information were included. Pooled odds ratios (OR) and 95% confidence intervals (CI) of each polymorphism were estimated. Our literature search yielded 297 records. After excluding duplicates and reports with incomplete information, 8 studies were eligible for meta-analysis, involving 2284 AMD patients versus 3416 controls, and 317 PCV patients versus 371 controls. Four PEDF polymorphisms were meta-analyzed: rs1136287, rs12150053, rs12948385 and rs9913583, but none was significantly associated with AMD or PCV. The most-investigated polymorphism, rs1136287, had a pooled-OR of 1.02 (95% CI: 0.94–1.11, P = 0.64) for AMD. In subgroup analysis by ethnicity, no significant association was identified. Polymorphisms present in single report showed no association. Therefore, existing data in literature does not support the role of PEDF in the genetic susceptibility of AMD and PCV, although replication in specific populations is warranted. Since the pooled-sample size for PCV was small, there is a need of PEDF genotyping in larger samples of PCV.

Age-related macular degeneration (AMD) is a degenerative disease at the central region of the retina - the macula, leading to distorted central vision in the early stage and severe visual loss in the late stage. AMD is a leading cause of irreversible visual disability and blindness among elderly in developed countries1. The prevalence of early AMD is approximately 8.01% and late AMD (including geographic atrophy and neovascular AMD [nAMD]) 0.37%2. The etiology of AMD is multifactorial, with genetic risk factors contributing to the disease development and progression3. Genes in the complement pathway, such as complement factor H (CFH)3,4, angiogenesis pathway, such as vascular endothelial growth factor (VEGF)5, the high-density lipoprotein metabolic pathway, such as cholesteryl ester transfer protein (CETP)6, and the HtrA serine peptidase 1 (HTRA1) gene7, have been associated with AMD.

Polypoidal choroidal vasculopathy (PCV), which is considered as a subtype of AMD, could also cause profound loss of central vision. Its prevalence is higher in Asians than in Caucasians8. PCV exhibits commonalities with nAMD in that both are choroidal vasculopathy associated with subretinal hemorrhage, scars and fibrosis8. However, PCV is characterized by inner choroidal vascular networks ending in polypoidal lesions, while nAMD is characterized by choroidal neovascularization (CNV)9,10. Moreover, PCV patients are relatively younger, usually lack drusen, and respond well to combined anti-VEGF and photodynamic therapy, while nAMD patients respond well to anti-VEGF monotherapy11,12. PCV is also a multifactorial disease with genetic susceptibility. Major genes of AMD, such as CFH, HTRA1 and CETP, also showed significant associations with PCV6. These aspects lead to a question whether PCV is a subtype of, or a distant phenotype from nAMD.

It has been assumed that abnormal vessels are caused by unbalanced stimulators and inhibitors of angiogenesis13. An imbalance between VEGF and pigment epithelial derived factor (PEDF) has been demonstrated in the progress of CNV in AMD14,15. The vascular endothelial growth factor A (VEGF-A) plays an important role in inducing the growth of choroidal new vessels16,17,18, which triggers proliferation and migration of vascular endothelial cells19. Anti-VEGF therapies have been widely used to treat both nAMD and PCV. Also, variants in the VEGF-A gene have been implicated in the genetic mechanism of AMD and PCV20,21. A recent meta-analysis of 9 articles with 2281 AMD cases versus 2820 controls revealed that VEGF-A rs1413711 and rs833061 increased the risk of AMD21.

In contrast to VEGF, the PEDF, a member of the serine proteinase inhibitor family, potently inhibits angiogenesis and regulates choroidal neovascularization in humans22,23,24,25. PEDF has been detected in the aqueous humor, vitreous, retina and choroid26,27. In the retina, PEDF inhibits the proliferation and migration of retinal endothelial cells and vascular permeability induced by VEGF, promotes the apoptosis of endothelial cells and down-regulates the pro-angiogenic factors23,28,29. PEDF is also a highly effective inhibitor of angiogenesis in cell culture and animal models25,30,31,32. Decreased vitreous level of PEDF had been associated with the CNV in AMD33. PEDF as a potential therapeutic agent has been investigated in animal models of CNV, and it was found that periocular or intravitreal introduction of PEDF could inhibit CNV22,34,35,36. Moreover, patients with nAMD were found to have reduced CNV size after a single intravitreal injection of PEDF-expressing adenoviral vector in a phase I clinical trial37. These studies altogether suggest that PEDF is an important factor for CNV, and hypothetically the PEDF gene is an excellent candidate gene for nAMD.

In 2005, Yamagishi et al. hypothesized that a single nucleotide polymorphism (SNP) in PEDF, rs1136287 (c.C215T, p.Met72Thr), might be a genetic marker for AMD38. This amino acid substitution is located at the end of a helix domain of the PEDF protein and leads to a BsstSI restriction site39, suggesting it could have functional impact. Later, rs1136287 was found to be associated with AMD in the Taiwanese and Korean populations40,41, providing initial evidences to support PEDF as a susceptibility gene for AMD. Subsequent studies in Caucasians and other Asian cohorts, including Japanese and Chinese, did not identify a significant association between rs1136287 and AMD, but the effects of the SNP, represented by the odds ratio (OR), were variable across study cohorts42,43,44,45,46. As such, whether PEDF rs1136287 is a genuine genetic marker for AMD remains inconclusive. Also, whether there is population-specific association of this SNP with AMD needs further confirmation. Moreover, SNPs other than rs1136287, such as rs12150053, rs12948385 and rs9913583 in PEDF had also been reported in AMD or PCV41,43,44,45,46, but their associations remains inconclusive.

Since PEDF is functionally important in AMD pathogenesis and could be a new target for AMD treatment, the identification of disease-associated gene variants could provide useful targets for studying the roles of PEDF in AMD pathogenesis and pharmacogenetics. To confirm the role of PEDF as a candidate gene for AMD and PCV, we conducted a systematic review and meta-analysis to evaluate the associations of all reported PEDF SNPs with AMD and PCV. This report is about the results of the meta-analysis.

Results

Characteristics of eligible studies on PEDF in AMD and/or PCV

Figure 1 showed the study inclusion of this meta-analysis. A total of 297 articles published between January 1, 1980 and August 21, 2014 were identified in the EMBASE and MEDLINE databases. By excluding duplicated and unrelated records, we got 13 relevant reports for further assessment. However, 6 of them were excluded because 2 articles are about PEDF and the treatment response in AMD and PCV47,48, 1 is not a case-control study38, and the other 3 are reviews49,50,51. By searching the reference lists of relevant studies and genome-wide association studies (GWAS) of AMD, we identified another 2 relevant articles52,53. However, one GWA study did not provide genotype or allele data in controls and was excluded from further analysis52. Therefore, a total of 8 case-control studies were finally included for the meta-analysis40,41,42,43,44,45,46,53, involving 2284 AMD cases versus 3416 controls, and 317 PCV cases versus 371 controls. The main characteristics of the included studies were summarized in Table 1. The sample sizes of AMD groups ranged from 109 to 893, PCV groups 140 to 177, and control groups 90 to 2199. The mean age ranged from 70.9 to 78.6 years in the AMD groups, 65 to 73 years in the PCV groups, and 44 to 77.4 years in the control groups. The gender ratios (male/female) varied from 0.51 to 3.46 in the AMD groups, 1.95 to 3.38 in the PCV groups, and 0.80 to 1.63 in the control groups. The subjects in 6 studies were Asians and 2 were Caucasians. Of the six studies on nAMD, 2 involved both nAMD and PCV, and 1 involved combined nAMD, non-neovascular AMD and PCV.

Figure 1. Flow diagram and results of literature review.

Figure 1

Open in a new tab

The flow diagram depicts the screening process of retrieved articles, including the number and reason of exclusion. AMD: age-related macular degeneration; GWAS: genome-wide association study; PCV: polypoidal choroidal vasculopathy.

Table 1. Characteristics of studies included in the meta-analysis.

Study Ethnicity Sample size Gender (male/female) Age (mean ± SD, years) Subtype
Case Control Case Control Case Control
AMD                
Bessho H 2009 Japanese 116 189 90/26 113/76 75.0 ± 7.2 72.0 ± 5.8 nAMD
Kim HS 2013 Korean 109 229 NA NA NA NA nAMD
Lin JM 2008 Chinese 190 90 108/82 49/41 71.1 ± 7.5 71.5 ± 6.9 nAMD and atrophic AMD
Mattes D 2009 Caucasian 269 155 91/178 69/86 71.4 ± 6.4 71.5 ± 6.9 nAMD
Mori K 2010 Japanese 408 142 313/95 74/68 78.4 ± 7.0 77.4 ± 6.5 nAMD, PCV and nnAMDa
Qu Y 2011 Chinese 168 230 95/73 134/96 71.9 ± 8.5 68.4 ± 9.8 nAMD
Wu K 2012 Chinese 131 182 84/57 113/69 70.9 ± 11.3 74.4 ± 9.6 nAMD
Cipriani V 2012b Caucasian 893 2199 399/494 1082/1117 78.6 ± 7.5 44–45b Advanced AMD
PCV                
Bessho H 2009 Japanese 140 189 108/32 113/76 73.0 ± 6.9 72.0 ± 5.8 PCV
Wu K 2012 Chinese 177 182 117/60 113/69 65.0 ± 8.45 74.4 ± 9.6 PCV
Open in a new tab

aCombined subtypes.

bData extracted from a genome-wide association study; for the control subjects only age range was given in the study.

nAMD: neovascular AMD; nnAMD: non-neovascular AMD; PCV: polypoidal choroidal vasculopathy; NA: not available from the initial report; SD: standard deviation.

Risk of bias assessment in eligible studies

As shown in Table 2, risk of ascertainment bias in the diagnostic criteria for AMD and PCV was present in 3 studies, in which subjects were not defined based on fundus fluorescein angiography (FFA) and indocyanine green angiography (ICGA)40,41,53. One paper did not mention the ascertainment of control subjects41. Risk of population stratification presented in 1 study, which used spouses and friends as control subjects53. There was risk of confounding bias in 5 studies, in which results were not adjusted for confounding variables40,41,45,46,53. All the studies reported Hardy-Weinberg equilibrium (HWE) in controls.

Table 2. Risk of bias assessment of included studies in the meta-analysis.

Study Ascertainment of AMD and PCV Ascertainment of controls Population stratification Confounding bias HWE in controls
Bessho H 2009 Yes Yes Yes Yes Yes
Kim HS 2013 Unclear Unclear Yes No Yes
Lin JM 2008 No Yes Yes No Yes
Mattes D 2009 Yes Yes Yes Yes Yes
Mori K 2010 Yes Yes Yes Yes Yes
Qu Y 2011 Yes Yes Yes No Yes
Wu K 2012 Yes Yes Yes No Yes
Cipriani V 2012 No Yes No No Yes
Open in a new tab

Yes, no and unclear presented low risk of bias, high risk of bias and insufficient information, respectively.

AMD: age-related macular degeneration; PCV: polypoidal choroidal vasculopathy; HWE: Hardy-Weinberg equilibrium.

Meta-analysis of PEDF polymorphisms in AMD

Totally 9 SNPs had been tested in AMD and/or PCV in the literature. However, only 4 SNPs (rs1136287, rs12150053, rs12948385 and rs9913583) in AMD and 1 SNP (rs1136287) in PCV were reported in at least two studies and thus eligible for meta-analysis. Summary of the allelic associations of these four PEDF polymorphisms are shown in Table 3. The other 5 SNPs, i.e., rs11658342, rs1894286, rs2269344, rs9889773 and rs3786136, appeared in single report but showed no association with AMD45,54. We also searched for SNP IDs that were merged with PEDF SNPs and found that rs1804144, rs3199567, rs16951641, rs17352972, rs17845405, rs17858264 and rs58553017 have been merged into rs1136287 in the dbSNP database. However, none of these SNP IDs except rs1136287 was adopted in the studies.

Table 3. Meta-analyses of allelic association of PEDF polymorphisms with AMD or PCV.

Polymorphism Ethnicity Alleles Number of cohorts Sample size (case/control) OR (95% CI) Z score P-value I2 (%)
rs1136287 All ancestries T vs C 8 2284/3416 1.02 (0.94–1.11) 0.47 0.64 19
(c.C215T, p.Met72Thr) Asian   6 1122/1062 1.06 (0.93–1.20) 0.87 0.39 38
Caucasian 2 1162/2354 0.99 (0.89–1.11) 0.11 0.91 0
  Asian PCVa T vs C 2 317/371 0.99 (0.80–1.22) 0.11 0.91 25
rs12150053 All ancestries C vs T 4 954/756 1.07 (0.91–1.27) 0.85 0.40 0
  Asian   3 685/601 1.09 (0.89–1.34) 0.83 0.41 0
rs12948385 All ancestries A vs G 3 786/526 1.05 (0.87–1.28) 0.53 0.60 0
  Asian   2 517/371 1.06 (0.81–1.39) 0.45 0.65 0
rs9913583 Asian A vs C 2 517/371 0.96 (0.58–1.59) 0.17 0.86 61
Open in a new tab

aOnly one SNP, rs1136287, was reported in PCV; the others were for AMD.

AMD: age-related macular degeneration; PCV: polypoidal choroidal vasculopathy; OR: odds ratio; CI: confidence intervals.

SNP rs1136287 is the most-investigated SNP in AMD, with a total of 2284 cases and 3416 controls included for the meta-analysis40,41,42,43,44,45,46,53. The pooled results showed no statistically significant association between rs1136287 and all forms of AMD (Table 3 and Fig. 2). In the allelic model, the odds ratio for the risk allele T was 1.02 (95% confidence intervals (CI): 0.94–1.11, P = 0.64, I2 = 19%). Also, the associations were not significant under the dominant, recessive, heterozygous and homozygous models (Supplementary Table S1). In the sensitivity analysis, we excluded geographic atrophy and non-neovascular AMD from the meta-analysis40,44,53 because PEDF was reportedly associated only with CNV22,23,24. Still, the pooled allelic OR was not statistically significant (OR = 1.12, 95% CI: 0.87–1.43, P = 0.38, I2 = 71%)40,41,42,43,45,46. Quality assessment showed that the Korean cohort was of higher risk of inducing bias than the other cohorts due to insufficient data of clear diagnostic criteria and confounding factors (e.g. gender, age, and smoking status)41. Therefore, we excluded the Korean cohort in the sensitivity analysis. Still the pooled allelic OR was non-significant (OR = 1.00, 95% CI: 0.92–1.09, P = 0.97, I2 = 0%). We also removed the Korean and Caucasian cohorts to include only Asian studies of high quality, but there was no significant change (OR = 1.01, 95% CI: 0.88–1.15, P = 0.93, I2 = 15%). In the subgroup analysis by ethnicity, still no significant association was detected in Caucasians (OR = 0.99, 95% CI: 0.89–1.11, P = 0.91, I2 = 0%), Japanese (OR = 0.96, 95% CI: 0.78–1.18, P = 0.71, I2 = 0%), or Chinese (OR = 1.04, 95% CI: 0.87–1.25, P = 0.66, I2 = 43%; Supplementary Table S2).

Figure 2. Forest plot of rs1136287(T) in AMD in allelic model.

Figure 2

Open in a new tab

Squares indicate study-specific odds ratios (ORs). The size of the box is proportional to the weight of the study. Horizontal lines indicate 95% confidence intervals (CI). A diamond indicates the summary OR with its corresponding 95% CI. AMD: age-related macular degeneration. The cases in the study of Lin et al. included both nAMD and atrophic AMD.

Regarding the other three SNPs, rs12150053 (c.-5736T>C), rs12948385 (c.-5304G>A) and rs9913583 (c.-86C>A), which are located in the promoter region or 5′-untranslated region of PEDF, the pooled ORs were not statistically significant in AMD in the allelic (Table 3 and Figs. 3, 4, 5) or other genetic models (Supplementary Table S1). Leave-one-out sensitivity analysis indicated that there was no substantial change after excluding any individual study, which manifested stable results (P > 0.1). Also, there was no publication bias for any SNPs according to the funnel plots and Egger's test (P > 0.1).

Figure 3. Forest plot of rs12150053(C) in AMD in allelic model.

Figure 3

Open in a new tab

Squares indicate study-specific odds ratios (ORs). The size of the box is proportional to the weight of the study. Horizontal lines indicate 95% confidence intervals (CI). A diamond indicates the summary OR with its corresponding 95% CI. AMD: age-related macular degeneration.

Figure 4. Forest plot of rs12948385(A) in AMD in allelic model.

Figure 4

Open in a new tab

Squares indicate study-specific odds ratios (ORs). The size of the box is proportional to the weight of the study. Horizontal lines indicate 95% confidence intervals (CI). A diamond indicates the summary OR with its corresponding 95% CI. AMD: age-related macular degeneration.

Figure 5. Forest plot of rs9913583(A) in AMD in allelic model.

Figure 5

Open in a new tab

Squares indicate study-specific odds ratios (ORs). The size of the box is proportional to the weight of the study. Horizontal lines indicate 95% confidence intervals (CI). A diamond indicates the summary OR with its corresponding 95% CI. AMD: age-related macular degeneration.

Meta-analysis of PEDF rs1136287 in PCV

For PCV, rs1136287 was the only SNP that was repeatedly studied. It was reported in 2 studies, involving a total of 317 cases and 371 controls42,46. Meta-analysis showed a lack of significant association between rs1136287 and PCV (OR = 0.99, 95% CI: 0.80–1.22, P = 0.91, I2 = 25%; Table 3 and Supplementary Fig. S1). We combined all AMD and PCV studies with an attempt to increase statistical power. Still no significant association was detected (OR = 1.02, 95% CI: 0.94–1.10, P = 0.61, I2 = 12%).

Discussion

In this systematic review and meta-analysis, we have, for the first time, summarized the association profiles of PEDF in AMD and PCV, and we found no significant association between reported PEDF SNPs and AMD/PCV in overall samples or different ethnic subgroups. Therefore, current literatures do not support the role of PEDF as a susceptibility gene for AMD and PCV, despite the PEDF protein is functionally important in choroidal neovascularization.

PEDF, an antiangiogenic and neurotrophic factor, involves in the neuronal survival and differentiation in the eye and brain. The PEDF gene, also known as SERPINF1, is located on chromosomal region 17p13.1. It contains 8 exons, encoding a polypeptide of 418 amino acids. PEDF was considered as a disease gene for AMD because (1) the PEDF protein is one of the most effective endogenous inhibitors of angiogenesis and neovascularization28,55; (2) decreased PEDF level was found in the vitreous of AMD patients than controls, suggesting that the deficiency of PEDF in the eye could play a role in the pathogenesis of AMD18; (3) intravitreal injection of PEDF-expressing adenoviral vector reduced CNV size in AMD37; and (4) there were studies reporting significant association of PEDF SNPs with AMD and/or PCV.

In the studies of Lin et al., rs1136287 was found to be associated with nAMD in Taiwanese, with an odds ratio of 2.21 (95% CI: 1.43–3.42, P = 0.005) for the T allele, but not with atrophic AMD (OR = 0.94, 95% CI: 0.61–1.45, P = 0.87)40. Also rs1136287 was associated with nAMD in a Korean population (OR = 1.39, 95% CI: 1.01–1.93, P = 0.045)41. However, as summarized in our meta-analysis, in another 6 studies (including 2 in Caucasians43,53, 2 in Japanese42,44 and 2 in Chinese45,46) no significant allelic association was found for rs1136287, although the heterozygous genotype (CT) showed a protective effect for AMD (OR = 0.59, 95% CI: 0.36–0.95, P = 0.03) in the study of Qu et al45. So far the largest sample size for rs1136287 was reported in a GWAS involving 893 cases and 2199 controls of Caucasian origin, in which no association was found with advanced AMD (OR = 1.00, 95% CI: 0.89–1.12, P = 0.97)53. Therefore, together with the stratification analysis in our meta-analysis, we conclude that SNP rs1136287 is not a susceptibility genetic marker for AMD in Caucasians. This leads to a question that whether the association of rs1136287 with AMD is population- or disease subtype-specific. Notably, the criteria for AMD classification for the subjects in all the included studies were consistent, except the Korean cohort, in which no explicit criteria for AMD were described44. Thus, subtype-specific association is less likely, especially for the Taiwanese cohort. Also, in our meta-analysis, we found no significant association of rs1136287 with all forms of AMD in Caucasians or Asians, with the ORs towards different directions in different populations and small heterogeneity among studies (Fig. 2). This suggests the associations detected in the Taiwanese and Korean cohorts might be chance findings from a limited sample size, or there could be population-specific association of this SNP, confirmation of which requires replication among Taiwanese and Korean populations.

In recent years, GWAS, a hypothesis-free approach, has become a predominant method for identifying associated loci for AMD. However, findings across different GWAS had been variable4,7,53,56,57. This could be due to the variation in sample sizes and ethnicities, leading to variable association signals. For example, the association signal at the 4q12 gene cluster, first identified in the Japanese population56, was not detected in a recent large-scale AMD GWAS in Caucasians57, suggesting population-specific effect. Moreover, in GWAS only SNPs reaching a predefined threshold are replicated, thus some disease-associated SNPs might have been missed, resulting in false negatives. Therefore, on the one hand, results from multiple cohorts should be incorporated to validate the initial signals by methods such as meta-analysis; whereas on the other hand, methods other than GWAS should play a role in gene identification. The candidate gene approach, which is hypothesis-based, has been an important method for mapping AMD genes. For example in the complement pathway, while the CFH gene was identified for AMD by GWAS, the complement components 2 and 3 (C2 and C3), and complement factor B (CFB) were identified under the hypothesis that variation in genes encoding proteins of the same pathway with CFH could be associated with AMD58,59. These genes have later been confirmed in genotyping studies57 or meta-analysis60 on AMD and PCV61, suggesting the importance of candidate gene analysis in the discovery of AMD genes. In our present meta-analysis, we aimed to confirm the role of an excellent candidate gene for AMD - PEDF, but we found no significant association of a major SNP rs1136287 with AMD or PCV. Nevertheless, our observation that no replication study has yet been available in Taiwanese and Korean populations may arouse follow-up studies on this SNP in the two populations.

Apart from rs1136287, we also found that another 3 PEDF SNPs, rs12150053, rs12948385 and rs9913583, were not associated with AMD. Notably among the included studies, only one involved haplotype-tagging SNPs in the association analysis45. In the study, 4 tagging SNPs (rs11658342, rs1894286, rs2269344 and rs9889773) with r2 cutoff of 1.0 and minor allele frequency (MAF) cutoff of 5%, and 3 reported SNPs (rs1136287, rs12150053 and rs12948385) were selected. The CT genotype of rs1136287 was found to be associated with AMD (OR = 0.59, 95% CI: 0.36–0.95, P = 0.03), although the allelic associations of all SNPs were non-significant45. Since a r2 cutoff of 1.0 is likely to limit the number of SNPs that capture the major proportion of gene information, we searched for the tagging SNPs of PEDF using a MAF cutoff of 5% and r2 cutoff of 0.8 in the HapMap Genome Browser (release No. 27, http://hapmap.ncbi.nlm.nih.gov/; accessed Oct 27, 2014), and we identified more SNPs (Supplementary Table S3). Among the included studies, one tagging SNP rs1136287 in the CHB (Han Chinese in Beijing) population was included in 3 Chinese cohorts40,45,46, while one tagging SNP rs9913583 in the JPT (Japanese in Tokyo) population was studied in 1 Japanese cohort44. Since haplotype-tagging SNP analysis is useful for identifying the responsible SNP in a genetic locus62, further studies using the tagging SNPs would be warranted to provide a comprehensive evaluation of PEDF in AMD and PCV.

Upon identifying a lack of association of the PEDF SNPs with AMD and PCV, we searched for possible association of PEDF with other ophthalmic and non-ophthalmic diseases with a view to better understand the role of PEDF. Previously, based on linkage analysis, Koenekoop et al. suggested PEDF as a causative gene for Leber's congenital amaurosis63. In the study of Miyake et al., PEDF rs12603825 was found to have marginal association with myopic CNV, while rs1136287 was found of no association with CNV in Japanese myopic patients64. A meta-analysis is not possible because only one article was found for each SNP. Of note, PEDF was evaluated in diabetic retinopathy in three studies39,65,66. However, three SNPs, rs1136287, rs12150053 and rs12948385, showed no significant association with DR by meta-analysis (Supplementary Fig. S2).

The current systematic review and meta-analysis is an overview of published genetic reports on PEDF in AMD and PCV. Our study revealed several limitations in this topic. First, AMD and PCV are multifactorial diseases involving both environmental and genetic factors. Our results were based on unadjusted assessment and indicated discrepancy even in the same ethnicity, suggesting environmental factors may be involved. Thus, a more rigorous analysis should be performed by stratifying other risk factors if data was available. Second, we found a limited number of studies for this meta-analysis and most cohorts were Asians. In particular, only 2 studies with relatively small sample sizes reported the association of PEDF with PCV. Therefore, a comprehensive association of PEDF with AMD and PCV should be elucidated in more study cohorts. Also, no replication study was available in the Taiwanese and Korean populations, in which significant association of rs1136287 with AMD was detected. Therefore, further studies should be performed in these 2 populations. Third, significant heterogeneity was detected for some SNPs (e.g., rs9913583 in AMD), thus the random-effect model was applied to yield more conservative odds ratio. Fourth, some studies got low score of quality assessment40,41 or did not give the classification of AMD44, which may cause imprecise results when AMD or PCV was evaluated separately. However, since our meta-analysis showed no association of PEDF SNPs with either AMD or PCV, the lack of classification in the initial studies would have no major impact to the final conclusion.

In conclusion, this systematic review and meta-analysis has, for the first time, provided an overview of reported PEDF SNPs in AMD and PCV, and the results suggest that PEDF is not a major susceptibility gene for the diseases in the overall population. However, further studies should be warranted to confirm the association of PEDF SNP rs1136287 with AMD in specific populations such as Taiwanese and Korean. Moreover, since the pooled sample size for PCV was small, further studies of PEDF in large PCV samples are warranted.

Methods

Literature search

Literature search was done in the MEDLINE and EMBASE databases for genetic studies on PEDF in AMD and/or PCV. We used MeSH terms and free words: (Pigment epithelium-derived factor or PEDF or SERPINF1 or serpin peptidase inhibitor, clade F or OI6 or OI12 or EPC-1 or PIG35) and (age-related macular degeneration or AMD or ARMD or age-related macular disease or age-related maculopathy or ARM or PCV or polypoidal choroidal vasculopathy). All related articles published before August 21, 2014 were retrieved without language restriction. To find more papers, we manually screened the reference lists of all eligible articles. Moreover, to maximize the usable data we also searched all reported genome-wide association studies of AMD including their supplementary materials. Details of search strategy were illuminated in Supplementary Table S4.

Inclusion and exclusion criteria

A study was included if it fulfills all the following criteria: (1) case-control study, cohort study or population-based study investigating the association between PEDF and AMD and/or PCV; (2) data of genotype and/or allele counts or frequencies were presented in the papers; (3) unrelated control subjects were free of AMD or PCV; (4) for articles published by the same group of authors on the same gene or markers, only the latest study or the one with the largest sample size was included. Animal researches, case report, reviews, conference report, editorial comment and reports without sufficient data were excluded (Supplementary Table S5).

Literature review and data extraction

Two reviewers (L.M. and S.M.T.) independently reviewed and extracted data from studies on the association between PEDF SNPs and AMD/PCV. Any discrepancies were resolved by another two reviewers (S.S.R. and L.J.C.) after thorough discussion. The following information was extracted from each record: the name of first author, publication year, ethnicity of the study population, study design, sample size, disease subtype, gender composition, mean age, allele and genotype distribution in cases and controls, Hardy-Weinberg equilibrium (HWE) test results in controls. The records were combined into one group if listed allele and/or genotype distribution was stratified by AMD classification40.

Risk of bias assessment

The reviewers appraised the qualities of retrieved records by a modified risk-of-bias score for genetic association studies, based on traditional epidemiologic and genetic considerations (Supplementary Table S6)67,68,69. The assessment consists of 3 domains: (1) information bias: evaluation of diagnostic criteria for AMD, PCV and controls; (2) confounding bias: assessment of population bias and other confounding variables; (3) consideration of HWE in individual study. Each domain contains 3 answers: yes, no or unclear, which presents low risk of bias, high risk of bias and unclear if the included study was assessed based on insufficient information.

Statistical analysis

Meta-analysis for each polymorphism was performed if it had been reported in ≥2 studies or cohorts. The association was assessed using different genetic models, including allelic, dominant, recessive, heterozygous and homozygous models. Pooled odds ratios and 95% confidence intervals of each SNP were estimated for the strength of association, using the fixed-effect (I2 ≤ 50%) or random-effect (I2 > 50%) model based on the heterogeneity test70. The I2 test was used to assess heterogeneity among studies. The I2 value was explained as of no (0–25%), low (25–50%), moderate (50–75%) or high heterogeneity (75–100%)71.

Sensitivity analysis was carried out to examine the influence by removing one study each time69. The potential publication bias was evaluated with funnel plots and the Egger's test72,73. When the p value of the Egger test was <0.05, publication bias was expected to exist. Statistical analyses were conducted using the software Review Manager (RevMan, version 5.2, The Cochrane Collaboration, Copenhagen, Denmark), and Egger's test was performed in R (version 2.15.0, http://cran.r-project.org/). A pooled P value of less than 0.05 was considered statistically significant.

Author Contributions

L.M., S.S.R. and L.J.C. conceived and participated in its design and searched databases. L.M. and S.M.T. reviewed and extracted data. L.M. and S.S.R. carried out the statistical analysis and interpretation of data. L.M. and L.J.C. drafted and revised the article. H.Y.C., A.L.Y., G.K. and C.P.P. read and approved the final manuscript.

Supplementary Material

Supplementary Information

supplementary material

srep09497-s1.pdf (226KB, pdf)

References

  1. Haddad S., Chen C. A., Santangelo S. L. & Seddon J. M. The genetics of age-related macular degeneration: a review of progress to date. Surv Ophthalmol 51, 316–363 (2006). [DOI] [PubMed] [Google Scholar]
  2. Wong W. L. et al. Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis. Lancet Glob Health 2, e106–e116 (2014). [DOI] [PubMed] [Google Scholar]
  3. Seddon J. M. et al. Association of CFH Y402H and LOC387715 A69S with progression of age-related macular degeneration. JAMA 297, 1793–1800 (2007). [DOI] [PubMed] [Google Scholar]
  4. Klein R. J. et al. Complement factor H polymorphism in age-related macular degeneration. Science 308, 385–389 (2005). [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Yu Y. et al. Common variants near FRK/COL10A1 and VEGFA are associated with advanced age-related macular degeneration. Hum Mol Genet 20, 3699–3709 (2011). [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Liu K. et al. Genes in the high-density lipoprotein metabolic pathway in age-related macular degeneration and polypoidal choroidal vasculopathy. Ophthalmology 121, 911–916 (2014). [DOI] [PubMed] [Google Scholar]
  7. Dewan A. et al. HTRA1 promoter polymorphism in wet age-related macular degeneration. Science 314, 989–992 (2006). [DOI] [PubMed] [Google Scholar]
  8. Laude A. et al. Polypoidal choroidal vasculopathy and neovascular age-related macular degeneration: Same or different disease? Prog Retin Eye Res 29, 19–29 (2010). [DOI] [PubMed] [Google Scholar]
  9. Yannuzzi L. A., Sorenson J., Spaide R. F. & Lipson B. Idiopathic polypoidal choroidal vasculopathy (IPCV). Retina 10, 1–8 (1990). [PubMed] [Google Scholar]
  10. Ciardella A. P., Donsoff I. M., Huang S. J., Costa D. L. & Yannuzzi L. A. Polypoidal choroidal vasculopathy. Surv Ophthalmol 49, 25–37 (2004). [DOI] [PubMed] [Google Scholar]
  11. Wong R. L. & Lai T. Y. Polypoidal choroidal vasculopathy: an update on therapeutic approaches. J Ophthalmic Vis Res 8, 359–371 (2013). [PMC free article] [PubMed] [Google Scholar]
  12. Holz F. G., Schmitz-Valckenberg S. & Fleckenstein M. Recent developments in the treatment of age-related macular degeneration. J Clin Invest 124, 1430–1438 (2014). [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Folkman J. Angiogenesis in cancer, vascular, rheumatoid and other disease. Nat Med 1, 27–31 (1995). [DOI] [PubMed] [Google Scholar]
  14. Ohno-Matsui K. et al. Novel mechanism for age-related macular degeneration: an equilibrium shift between the angiogenesis factors VEGF and PEDF. J Cell Physiol 189, 323–333 (2001). [DOI] [PubMed] [Google Scholar]
  15. Holekamp N. M., Bouck N. & Volpert O. Pigment epithelium-derived factor is deficient in the vitreous of patients with choroidal neovascularization due to age-related macular degeneration. Am J Ophthalmol 134, 220–227 (2002). [DOI] [PubMed] [Google Scholar]
  16. Ferrara N., Gerber H. P. & LeCouter J. The biology of VEGF and its receptors. Nat Med 9, 669–676 (2003). [DOI] [PubMed] [Google Scholar]
  17. Matsuoka M. et al. Expression of pigment epithelium derived factor and vascular endothelial growth factor in choroidal neovascular membranes and polypoidal choroidal vasculopathy. Br J Ophthalmol 88, 809–815 (2004). [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Bhutto I. A. et al. Pigment epithelium-derived factor (PEDF) and vascular endothelial growth factor (VEGF) in aged human choroid and eyes with age-related macular degeneration. Exp Eye Res 82, 99–110 (2006). [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Leung D. W., Cachianes G., Kuang W. J., Goeddel D. V. & Ferrara N. Vascular endothelial growth factor is a secreted angiogenic mitogen. Science 246, 1306–1309 (1989). [DOI] [PubMed] [Google Scholar]
  20. Park D. H. & Kim I. T. Polymorphisms in the VEGF-A in polypoidal choroidal vasculopathy in a Korean population. Jpn J Ophthalmol 56, 145–151 (2012). [DOI] [PubMed] [Google Scholar]
  21. Huang C., Xu Y., Li X. & Wang W. Vascular endothelial growth factor A polymorphisms and age-related macular degeneration: a systematic review and meta-analysis. Mol Vis 19, 1211–1221 (2013). [PMC free article] [PubMed] [Google Scholar]
  22. Mori K. et al. AAV-mediated gene transfer of pigment epithelium-derived factor inhibits choroidal neovascularization. Invest Ophthalmol Vis Sci 43, 1994–2000 (2002). [PubMed] [Google Scholar]
  23. Liu H. et al. Identification of the antivasopermeability effect of pigment epithelium-derived factor and its active site. Proc Natl Acad Sci U S A 101, 6605–6610 (2004). [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Imai D., Yoneya S., Gehlbach P. L., Wei L. L. & Mori K. Intraocular gene transfer of pigment epithelium-derived factor rescues photoreceptors from light-induced cell death. J Cell Physiol 202, 570–578 (2005). [DOI] [PubMed] [Google Scholar]
  25. Dawson D. W. et al. Pigment epithelium-derived factor: a potent inhibitor of angiogenesis. Science 285, 245–248 (1999). [DOI] [PubMed] [Google Scholar]
  26. Nakashizuka H. et al. Clinicopathologic findings in polypoidal choroidal vasculopathy. Invest Ophthalmol Vis Sci 49, 4729–4737 (2008). [DOI] [PubMed] [Google Scholar]
  27. Gomi F. & Tano Y. Polypoidal choroidal vasculopathy and treatments. Curr Opin Ophthalmol 19, 208–212 (2008). [DOI] [PubMed] [Google Scholar]
  28. Duh E. J. et al. Pigment epithelium-derived factor suppresses ischemia-induced retinal neovascularization and VEGF-induced migration and growth. Invest Ophthalmol Vis Sci 43, 821–829 (2002). [PubMed] [Google Scholar]
  29. Askou A. L. Development of gene therapy for treatment of age-related macular degeneration. Acta Ophthalmol 92 Thesis 3, 1–38 (2014). [DOI] [PubMed] [Google Scholar]
  30. Yamagishi S. et al. Pigment epithelium-derived factor protects cultured retinal pericytes from advanced glycation end product-induced injury through its antioxidative properties. Biochem Biophys Res Commun 296, 877–882 (2002). [DOI] [PubMed] [Google Scholar]
  31. Yamagishi S., Inagaki Y., Amano S., Okamoto T. & Takeuchi M. Up-regulation of vascular endothelial growth factor and down-regulation of pigment epithelium-derived factor messenger ribonucleic acid levels in leptin-exposed cultured retinal pericytes. Int J Tissue React 24, 137–142 (2002). [PubMed] [Google Scholar]
  32. Yamagishi S. et al. Pigment epithelium-derived factor inhibits leptin-induced angiogenesis by suppressing vascular endothelial growth factor gene expression through anti-oxidative properties. Microvasc Res 65, 186–190 (2003). [DOI] [PubMed] [Google Scholar]
  33. Holekamp N. M., Bouck N. & Volpert O. Pigment epithelium-derived factor is deficient in the vitreous of patients with choroidal neovascularization due to age-related macular degeneration. Am J Ophthalmol 134, 220–227 (2002). [DOI] [PubMed] [Google Scholar]
  34. Mori K. et al. Pigment epithelium-derived factor inhibits retinal and choroidal neovascularization. J Cell Physiol 188, 253–263 (2001). [DOI] [PubMed] [Google Scholar]
  35. Gehlbach P. et al. Periocular injection of an adenoviral vector encoding pigment epithelium-derived factor inhibits choroidal neovascularization. Gene Ther 10, 637–646 (2003). [DOI] [PubMed] [Google Scholar]
  36. Saishin Y. et al. Periocular gene transfer of pigment epithelium-derived factor inhibits choroidal neovascularization in a human-sized eye. Hum Gene Ther 16, 473–478 (2005). [DOI] [PubMed] [Google Scholar]
  37. Campochiaro P. A. et al. Adenoviral vector-delivered pigment epithelium-derived factor for neovascular age-related macular degeneration: results of a phase I clinical trial. Hum Gene Ther 17, 167–176 (2006). [DOI] [PubMed] [Google Scholar]
  38. Yamagishi S., Nakamura K., Inoue H. & Takeuchi M. Met72Thr polymorphism of pigment epithelium-derived factor gene and susceptibility to age-related macular degeneration. Med Hypotheses 64, 1202–1204 (2005). [DOI] [PubMed] [Google Scholar]
  39. Yamagishi S. et al. Pigment epithelium-derived factor Met72Thr polymorphism in patients with diabetic microangiopathy. Int J Clin Pharmacol Res 22, 67–71 (2002). [PubMed] [Google Scholar]
  40. Lin J. M. et al. Pigment Epithelium-Derived Factor Gene Met72Thr Polymorphism Is Associated With Increased Risk of Wet Age-related Macular Degeneration. Am J Ophthalmol 145, 716–721 (2008). [DOI] [PubMed] [Google Scholar]
  41. Kim H. S., Kim Y. H., Mok J. W. & Joo C. K. Genetic association of VEGF and PEDF polymorphisms with age-related macular degeneration in Korean. Genes Genom 35, 335–342 (2013). [Google Scholar]
  42. Bessho H., Kondo N., Honda S., Kuno S.-I. & Negi A. Coding variant Met72Thr in the PEDF gene and risk of neovascular age-related macular degeneration and polypoidal choroidal vasculopathy. Mol Vis 15, 1107–1114 (2009). [PMC free article] [PubMed] [Google Scholar]
  43. Mattes D. et al. Analysis of three pigment epithelium-derived factor gene polymorphisms in patients with exudative age-related macular degeneration. Mol Vis 15, 343–348 (2009). [PMC free article] [PubMed] [Google Scholar]
  44. Mori K. et al. Phenotype and Genotype Characteristics of Age-related Macular Degeneration in a Japanese Population. Ophthalmology 117, 928–938 (2010). [DOI] [PubMed] [Google Scholar]
  45. Qu Y. et al. Pigment epithelium-derived factor gene polymorphisms in exudative age-related degeneration in a Chinese cohort. Curr Eye Res 36, 60–65 (2011). [DOI] [PubMed] [Google Scholar]
  46. Wu K. et al. Lack of association with PEDF Met72Thr variant in neovascular age-related macular degeneration and polypoidal choroidal vasculopathy in a Han Chinese population. Curr Eye Res 37, 68–72 (2012). [DOI] [PubMed] [Google Scholar]
  47. Imai D. et al. CFH, VEGF, and PEDF genotypes and the response to intravitreous injection of bevacizumab for the treatment of age-related macular degeneration. J Ocul Biol Dis Infor 3, 53–59 (2010). [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Nakata I. et al. Genetic variants in pigment epithelium-derived factor influence response of polypoidal choroidal vasculopathy to photodynamic therapy. Ophthalmology 118, 1408–1415 (2011). [DOI] [PubMed] [Google Scholar]
  49. Klein M. L. & Francis P. J. Genetics of age-related macular degeneration. Ophthalmol Clin North Am 16, 567–574 (2003). [DOI] [PubMed] [Google Scholar]
  50. Patricia Becerra S. Focus on molecules: Pigment epithelium-derived factor (PEDF). Exp Eye Res 82, 739–740 (2006). [DOI] [PubMed] [Google Scholar]
  51. Wen F. & Wu K. F. Current researches and existing problems of molecular biology in neovascular age-related macular degeneration and polypoidal choroidal vasculopathy. [Chinese]. Zhonghua Shiyan Yanke Zazhi/Chin J Exp Ophthalmol 29, 289–292 (2011). [Google Scholar]
  52. Neale B. M. et al. Genome-wide association study of advanced age-related macular degeneration identifies a role of the hepatic lipase gene (LIPC). Proc Natl Acad Sci U S A 107, 7395–7400 (2010). [DOI] [PMC free article] [PubMed] [Google Scholar]
  53. Cipriani V. et al. Genome-wide association study of age-related macular degeneration identifies associated variants in the TNXB–FKBPL–NOTCH4 region of chromosome 6p21.3. Hum Mol Genet 21, 4138–4150 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
  54. Strunnikova N. V. et al. Transcriptome analysis and molecular signature of human retinal pigment epithelium. Hum Mol Genet 19, 2468–2486 (2010). [DOI] [PMC free article] [PubMed] [Google Scholar]
  55. Subramanian P. et al. Pigment epithelium-derived factor (PEDF) prevents retinal cell death via PEDF receptor (PEDF-R): Identification of a functional ligand binding site. J Biol Chem 288, 23928–23942 (2013). [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Arakawa S. et al. Genome-wide association study identifies two susceptibility loci for exudative age-related macular degeneration in the Japanese population. Nat Genet 43, 1001–1004 (2011). [DOI] [PubMed] [Google Scholar]
  57. Fritsche L. G. et al. Seven new loci associated with age-related macular degeneration. Nat Genet 45, 433–439 (2013). [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Gold B. et al. Variation in factor B (BF) and complement component 2 (C2) genes is associated with age-related macular degeneration. Nat Genet 38, 458–462 (2006). [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Yates J. R. et al. Complement C3 variant and the risk of age-related macular degeneration. N Engl J Med 357, 553–561 (2007). [DOI] [PubMed] [Google Scholar]
  60. Thakkinstian A. et al. The association between complement component 2/complement factor B polymorphisms and age-related macular degeneration: a HuGE review and meta-analysis. Am J Epidemiol 176, 361–372 (2012). [DOI] [PMC free article] [PubMed] [Google Scholar]
  61. Liu K. et al. Gender specific association of a complement component 3 polymorphism with polypoidal choroidal vasculopathy. Sci Rep 4, 7018 (2014). [DOI] [PMC free article] [PubMed] [Google Scholar]
  62. Liu K. et al. Associations of the C2-CFB-RDBP-SKIV2L locus with age-related macular degeneration and polypoidal choroidal vasculopathy. Ophthalmology 120, 837–843 (2013). [DOI] [PubMed] [Google Scholar]
  63. Koenekoop R. et al. Four polymorphic variations in the PEDF gene identified during the mutation screening of patients with Leber congenital amaurosis. Mol Vis 5, 10 (1999). [PubMed] [Google Scholar]
  64. Miyake M. et al. Evaluation of pigment epithelium-derived factor and complement factor I polymorphisms as a cause of choroidal neovascularization in highly myopic eyes. Invest Ophthalmol Vis Sci 54, 4208–4212 (2013). [DOI] [PubMed] [Google Scholar]
  65. Iizuka H. et al. Promoter polymorphisms of the pigment epithelium-derived factor gene are associated with diabetic retinopathy. Biochem Biophys Res Commun 361, 421–426 (2007). [DOI] [PubMed] [Google Scholar]
  66. Balasubbu S. et al. Association analysis of nine candidate gene polymorphisms in Indian patients with type 2 diabetic retinopathy. BMC Med Genet 11, 158 (2010). [DOI] [PMC free article] [PubMed] [Google Scholar]
  67. Attia J., Thakkinstian A. & D'Este C. Meta-analyses of molecular association studies: Methodologic lessons for genetic epidemiology. J Clin Epidemiol 56, 297–303 (2003). [DOI] [PubMed] [Google Scholar]
  68. Ioannidis J. P. A. et al. Assessment of cumulative evidence on genetic associations: Interim guidelines. Int J Epidemiol 37, 120–132 (2008). [DOI] [PubMed] [Google Scholar]
  69. Thakkinstian A. et al. Systematic review and meta-analysis of the association between complement component 3 and age-related macular degeneration: A HuGE review and meta-analysis. Am J Epidemiol 173, 1365–1369 (2011). [DOI] [PubMed] [Google Scholar]
  70. Lau J., Ioannidis J. P. & Schmid C. H. Quantitative synthesis in systematic reviews. Ann Intern Med 127, 820–826 (1997). [DOI] [PubMed] [Google Scholar]
  71. Higgins J. P., Thompson S. G., Deeks J. J. & Altman D. G. Measuring inconsistency in meta-analyses. BMJ 327, 557–560 (2003). [DOI] [PMC free article] [PubMed] [Google Scholar]
  72. Copas J. & Shi J. Q. Meta-analysis, funnel plots and sensitivity analysis. Biostatistics 1, 247–262 (2000). [DOI] [PubMed] [Google Scholar]
  73. Harbord R. M., Egger M. & Sterne J. A. A modified test for small-study effects in meta-analyses of controlled trials with binary endpoints. Stat Med 25, 3443–3457 (2006). [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary Information

supplementary material

srep09497-s1.pdf (226KB, pdf)

Articles from Scientific Reports are provided here courtesy of Nature Publishing Group

RESOURCES