PEDF expression affects the oxidative and inflammatory state of choroidal endothelial cells

Neutrophil extracellular traps boost laser-induced mouse choroidal neovascularization through the activation of the choroidal endothelial cell TLR4/HIF-1α pathway

Choroidal neovascularization (CNV) is characterized by the infiltration of immune cells, particularly neutrophils. Neutrophil extracellular trap (NET) facilitates the angiogenesis of pulmonary endothelial cells via activating Toll-like receptor 4 (TLR4). TLR4 promotes the expression of transcription factor hypoxia inducible factor-1α (HIF-1α), which promotes inflammation and angiogenesis via the up-regulation of metalloproteinase-9 (MMP-9) and interleukin-1β (IL-1β). In the present study, we aimed to identify the formation of NET and its role in CNV. Our results showed that NET levels were increased in a mouse laser-induced CNV model via oxidative stress, whereas the inhibition of NET alleviated CNV. In vitro, NET activated the TLR4/HIF-1α pathway in human choroidal endothelial cells (HCECs). Additionally, NET increased the transcription and expression of MMP-9 and IL-1β in HCECs via activating the TLR4/HIF-1α pathway. Meanwhile, NET promoted the inflammatory response accompanied by the proliferation, migration and tube formation of HCECs in a MMP-9- and IL-1β-dependent manner. In conclusion, NET was up-regulated in CNV and promoted the formation of CNV via activating the TLR4/HIF-1α pathway in choroidal endothelial cells. Our data uncovered the novel role of NET in promoting the formation of CNV. The underlying mechanism of NET could be targeted to delay the process of CNV.

Chimpanzee adenovirus-mediated multiple gene therapy for age-related macular degeneration

Neovascular age-related macular degeneration AMD (nAMD) is characterized by choroidal neovascularization (CNV) and could lead to irreversible blindness. However, anti-vascular endothelial growth factor (VEGF) therapy has limited efficacy. Therefore, we generated a chimpanzee adenoviral vector (AdC68-PFC) containing three genes, pigment endothelial-derived factor (PEDF), soluble fms-like tyrosine kinase-1 (sFlt-1), and soluble forms of CD59 (sCD59), to treat nAMD. The results showed that AdC68-PFC mediated a strong onset of PEDF, sFlt-1, and sCD59 expression both in vivo and in vitro. AdC68-PFC showed preventive and therapeutic effects following intravitreal (IVT) injection in the laser-induced CNV model and very low-density lipoprotein receptor-deficient (Vldlr-/-) mouse model. In vitro assessment indicated that AdC68-PFC had a strong inhibitory effect on endothelial cells. Importantly, the safety test showed no evidence of in vivo toxicity of adenovirus in murine eyes. Our findings suggest that AdC68-PFC may be a long-acting and safe gene therapy vector for future nAMD treatments.

Protective Effect of Vaccinium myrtillus Extract on X-Ray Irradiation-Induced Retinal Toxicity via eNOS and 8-OHdG expression

Every year, hundreds of thousands of cancer patients receive radiotherapy treatment. Oxidative stress is observed in healthy tissues due to irradiation exposure. The present study is the first to address the effects of Vaccinium myrtillus (whortleberry, WB) against the effects of X-ray irradiation on retinal tissue. Twenty-four Sprague-Dawley rats were randomly allocated into 4 groups: (1) control group: rats without any treatment, (2) X-ray irradiation group: 8 Gray (Gy) RT for 2 days, (3) 100 mg WB extract + X-ray irradiation group: 8 Gy irradiation for 2 days and followed by intraperitoneal (IP) WB extract (100 mg/kg) supplementation for 10 days, (4) 200 mg WB extract + X-ray irradiation group: 8 Gy irradiation for 2 days and followed by IP WB extract (200 mg/kg) supplementation for 10 days. Eyes were enucleated on the 10th day after RT for histopathological, immunohistochemical (8-hydroxy-2'-deoxyguanosine [8-OHdG], endothelial nitric oxide synthase [eNOS]), and biochemical analyses (glutathione peroxidase [GSH], and malondialdehyde [MDA]). The GSH levels significantly decreased and MDA levels and 8-OHdG staining increased after X-ray irradiation compared to the control group. Combined X-ray irradiation + WB treatment significantly increased GSH levels and significantly decreased MDA production and 8-OHdG staining. However, eNOS staining was not affected in any of the groups. Besides, X-ray irradiation significantly increased cell losses and edematous areas. The WB significantly reversed the cellular damage in ganglion cells, inner nuclear, and outer nuclear layers in quantitative analyses. The X-ray irradiation caused significant retinal impairment, and additional WB therapy provided protective effects against radiation-induced retinopathy. These results may suggest WB extract as an adjuvant therapy to reverse retinal impairments after X-ray irradiation.

Variability in Retinal Neuron Populations and Associated Variations in Mass Transport Systems of the Retina in Health and Aging

Aging is associated with a broad range of visual impairments that can have dramatic consequences on the quality of life of those impacted. These changes are driven by a complex series of alterations affecting interactions between multiple cellular and extracellular elements. The resilience of many of these interactions may be key to minimal loss of visual function in aging; yet many of them remain poorly understood. In this review, we focus on the relation between retinal neurons and their respective mass transport systems. These metabolite delivery systems include the retinal vasculature, which lies within the inner portion of the retina, and the choroidal vasculature located externally to the retinal tissue. A framework for investigation is proposed and applied to identify the structures and processes determining retinal mass transport at the cellular and tissue levels. Spatial variability in the structure of the retina and changes observed in aging are then harnessed to explore the relation between variations in neuron populations and those seen among retinal metabolite delivery systems. Existing data demonstrate that the relation between inner retinal neurons and their mass transport systems is different in nature from that observed between the outer retina and choroid. The most prominent structural changes observed across the eye and in aging are seen in Bruch’s membrane, which forms a selective barrier to mass transfers at the interface between the choroidal vasculature and the outer retina.

Osteopontin accumulates in basal deposits of human eyes with age-related macular degeneration and may serve as a biomarker of aging

A common clinical phenotype of several neurodegenerative and systemic disorders including Alzheimer's disease and atherosclerosis is the abnormal accumulation of extracellular material, which interferes with routine cellular functions. Similarly, patients with age-related macular degeneration (AMD), the leading cause of vision loss among the aged population, present with extracellular lipid- and protein-filled basal deposits in the back of the eye. While the exact mechanism of growth and formation of these deposits is poorly understood, much has been learned from investigating their composition, providing critical insights into AMD pathogenesis, prevention, and therapeutics. We identified human osteopontin (OPN), a phosphoprotein expressed in a variety of tissues in the body, as a newly discovered component of basal deposits in AMD patients, with a distinctive punctate staining pattern. OPN expression within these lesions, which are associated with AMD disease progression, were found to co-localize with abnormal calcium deposition. Additionally, OPN puncta colocalized with an AMD risk-associated complement pathway protein, but not with apolipoprotein E or vitronectin, two other well-established basal deposit components. Mechanistically, we found that retinal pigment epithelial cells, cells vulnerable in AMD, will secrete OPN into the extracellular space, under oxidative stress conditions, supporting OPN biosynthesis locally within the outer retina. Finally, we report that OPN levels in plasma of aged (non-AMD) human donors were significantly higher than levels in young (non-AMD) donors, but were not significantly different from donors with the different clinical subtypes of AMD. Collectively, our study defines the expression pattern of OPN in the posterior pole as a function of disease, and its local expression as a potential histopathologic biomarker of AMD.

Caffeine Inhibits Choroidal Neovascularization Through Mitigation of Inflammatory and Angiogenesis Activities

Adenosine receptors (AR) are widely expressed in a variety of tissues including the retina and brain. They are involved in adenosine-mediated immune responses underlying the onset and progression of neurodegenerative diseases. The expression of AR has been previously demonstrated in some retinal cells including endothelial cells and retinal pigment epithelial cells, but their expression in the choroid and choroidal cells remains unknown. Caffeine is a widely consumed AR antagonist that can influence inflammation and vascular cell function. It has established roles in the treatment of neonatal sleep apnea, acute migraine, and post lumbar puncture headache as well as the neurodegenerative diseases such as Parkinson and Alzheimer. More recently, AR antagonism with caffeine has been shown to protect preterm infants from ischemic retinopathy and retinal neovascularization. However, whether caffeine impacts the development and progression of ocular age-related diseases including neovascular age-related macular degermation remains unknown. Here, we examined the expression of AR in retinal and choroidal tissues and cells. We showed that antagonism of AR with caffeine or istradefylline decreased sprouting of thoracic aorta and choroid/retinal pigment epithelium explants in ex vivo cultures, consistent with caffeine's ability to inhibit endothelial cell migration in culture. In vivo studies also demonstrated the efficacy of caffeine in inhibition of choroidal neovascularization and mononuclear phagocyte recruitment to the laser lesion sites. Istradefylline, a specific AR 2A antagonist, also decreased choroidal neovascularization. Collectively, our studies demonstrate an important role for expression of AR in the choroid whose antagonism mitigate choroidal inflammatory and angiogenesis activities.

Factors affecting the response to subthreshold micropulse laser therapy used in center-involved diabetic macular edema

The purpose of this study was to investigate the effect of the status of retinal pigment epithelium (RPE) and HbA1c levels on the efficacy of the subthreshold micropulse laser (SMPL) in the treatment of center-involving diabetic macular edema (DME). A total of 20 eyes of 20 patients (mean age 57.9 ± 9.7 years) who were diagnosed with center-involving DME and treated with SMPL for refusing intravitreal injection and 20 eyes of 20 age- and sex-matched healthy participants were enrolled. All patients were followed up in the 1st and 3rd months after SMPL. For measurement of RPE area central 1000 microns, macular EDI-OCT scans were binarized by using the public domain software ImageJ, with a semi-automated technique. There was a significant increase in BCVA values and a significant decrease in CMT values during follow-up. The area of RPE before SMPL was significantly thinner in the patient group (p: 0.004). When the areas of RPE before and 3 months after SMPL were compared, no significant change was observed (p: 0.437). When the relationship between pre-treatment area of RPE and HbA1c was examined, an inverse correlation was observed (p: 0.018). The patients were evaluated by dividing them into 2 groups as 2nd session SMPL required and not required, and the area of RPE was smaller in the group requiring 2nd session SMPL (p: 0.030). The status of central RPE may be a determining factor on the response to treatment. Additionally, HbA1c levels may have an impact on treatment efficacy.

Retinal tissue develops an inflammatory reaction to tobacco smoke and electronic cigarette vapor in mice

Cigarette smoke has been identified as a major risk factor for the development of age-related macular degeneration (AMD). As an alternative to conventional cigarettes (C-cigarette), electronic cigarettes (E-cigarette) have been globally promoted and are currently widely used. The increasing usage of E-cigarettes raises concerns with regard to short- (2 weeks), medium- (3 months), and long- (8 months) term consequences related to retinal tissue. In this report, a controlled study in mouse models was conducted to probe the comprehensive effects of E-cigarette vapor on retina, retinal pigmented epithelium (RPE), and choroidal tissues by (1) comparing the effects of C-cigarette smoke and E-cigarette vapor on retina separately and (2) determining the effects of E-cigarette vapor on the RPE and analyzing the changes with regard to inflammatory (IL-1β, TNFα, iNOS) and angiogenic (VEGF, PEDF) mediators in retina/RPE/choroid by ELISA assays. The data showed that C-cigarette smoke exposure promoted an inflammatory reaction in the retina in vivo. Mice exposed to E-cigarette (nicotine-free) vapor developed inflammatory and angiogenic reactions more pronounced in RPE and choroid as compared to retinal tissue, while nicotine-containing E-cigarette vapor caused even a more serious reaction. Both inflammatory and pro-angiogenic reactions increased with the extension of exposure time. These results demonstrate that exposure to C-cigarette smoke is harmful to the retina. Likewise, the exposure to E-cigarette vapor (with or without nicotine) increases the occurrence and progression of inflammatory and angiogenic stimuli in the retina, which might also be related to the onset of wet AMD in humans. KEY MESSAGES: C-cigarette smoke exposure promotes an inflammatory reaction in the retina in vivo. Mice exposed to E-cigarette (nicotine-free) vapor develop inflammatory and angiogenic reactions more pronounced in RPE and choroid compared to retinal tissue, while nicotine-containing E-cigarette vapor causes even a more serious reaction. Both inflammatory and pro-angiogenic reactions increase with the extension of E-cigarette vapor exposure time.

Reduction of choroidal neovascularization via cleavable VEGF antibodies conjugated to exosomes derived from regulatory T cells

Choroidal neovascularization induced by age-related macular degeneration and retinal neovascularization induced by diabetic retinopathy-two leading causes of blindness-are often treated using antibodies targeting vascular endothelial growth factor (VEGF). Here we report a strong association between inflammation and high VEGF expression in aqueous humour samples from patients with choroidal or retinal neovascularization, and show that intravitreally injected exosomes derived from regulatory T cells and conjugated with an anti-VEGF antibody via a peptide linker that is cleavable by matrix metalloproteinases markedly suppressed ocular neovascularization in mouse and non-human primate models of choroidal neovascularization. The engineered exosomes, which selectively accumulate in the neovascularization lesions, could be adapted for other combination therapies of therapeutic antibodies and anti-inflammatory cargo.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

Human Retinal Pigment Epithelial Cells Overexpressing the Neuroprotective Proteins PEDF and GM-CSF to Treat Degeneration of the Neural Retina

BACKGROUND

Non-viral transposon-mediated gene delivery can overcome viral vectors' limitations. Transposon gene delivery offers the safe and life-long expression of genes such as pigment epithelium-derived factor (PEDF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) to counteract retinal degeneration by reducing oxidative stress damage.

OBJECTIVE

Use Sleeping Beauty transposon to transfect human retinal pigment epithelial (RPE) cells with the neuroprotective factors PEDF and GM-CSF to investigate the effect of these factors on oxidative stress damage.

METHODS

Human RPE cells were transfected with PEDF and GM-CSF by electroporation, using the hyperactive Sleeping Beauty transposon gene delivery system (SB100X). Gene expression was determined by RT-qPCR and protein level by Western Blot as well as ELISA. The cellular stress level and the neuroprotective effect of the proteins were determined by measuring the concentrations of the antioxidant glutathione in human RPE cells and immunohistochemical examination of retinal integrity, inflammation, and apoptosis of rat retina-organotypic cultures (ROC) exposed to H2O2.

RESULTS

Human RPE cells were efficiently transfected, showing a significantly augmented gene expression and protein secretion. Human RPE cells overexpressing PEDF and/or GM-CSF or pre-treated with recombinant proteins presented significantly increased glutathione levels post-H2O2 incubation than non-transfected/untreated controls. rPEDF and/or rGM-CSF-treated ROC exhibited decreased inflammatory reactions and cell degeneration.

CONCLUSION

GM-CSF and/or PEDF could be delivered successfully to RPE cells by combining the use of SB100X and electroporation. PEDF and/or GM-CSF reduced H2O2-mediated oxidative stress damage in RPE cells and ROC offering an encouraging technique to re-establish a cell-protective environment to halt age-related retinal degeneration.

IGFBP‑rP1‑silencing promotes hypoxia‑induced angiogenic potential of choroidal endothelial cells via the RAF/MEK/ERK signaling pathway

Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) has been reported to have various functions in different cellular contexts. Our previous investigation discovered that IGFBP-rP1 inhibited retinal angiogenesis in vitro and in vivo by inhibiting the pro-angiogenic effect of VEGF and downregulating VEGF expression. Recently, IGFBP-rP1 was confirmed to be downregulated in the aqueous humor of patients with neovascular age-related macular degeneration compared with controls; however, its specific role remains unknown. The present study applied the technique of gene silencing, reverse transcription-quantitative PCR, western blotting, cell viability assays, cell motility assays and tube formation assays. Chemical hypoxic conditions and choroidal endothelial (RF/6A) cells were used to explore the effect of IGFBP-rP1-silencing on the phenotype activation of RF/6A cells under hypoxic conditions and to elucidate the underlying mechanisms. siRNA achieved IGFBP-rP1-silencing in RF/6A cells without cytotoxicity. IGFBP-rP1-silencing significantly restored the viability of RF/6A cells in hypoxia and enhanced hypoxia-induced migration and capillary-like tube formation of RF/6A cells. Furthermore, IGFBP-rP1-silencing significantly upregulated the expression of B-RAF, phosphorylated (p)-MEK, p-ERK and VEGF in RF/6A cells under hypoxic conditions; however, these upregulations were inhibited by exogenous IGFBP-rP1. These data indicated that silencing IGFBP-rP1 expression in RF/6A cells effectively promoted the hypoxia-induced angiogenic potential of choroidal endothelial cells by upregulating RAF/MEK/ERK signaling pathway activation and VEGF expression.

The Relationship between Choroidal Thickness and Intracellular Oxidised-reduced Glutathione and Extracellular Thiol-disulfide Homeostasis at Different Stages of Diabetic Retinopathy

Purpose: To evaluate the relationship between diabetic retinopathy and oxidative damage by measuring intracellular and extracellular thiol levels, and to compare intracellular and extracellular thiol levels. Method: In this prospective, cross-sectional, and comparative study, 25 healthy control participants (group 1), a total of 25 diabetic macular edema (DME) patients with non-proliferative diabetic retinopathy (DRP) and without DME (group 2), and 25 DME patients with non-proliferative DRP and with DME (group 3) were included. Choroidal thickness (ChT) and central macular thickness (CMT) were measured by spectral domain optic coherence tomography. For the evaluation of antioxidant/oxidant balance, intracellular GSH (reduced glutathione) and GSSG (oxidized glutathione), extracellular SH (thiol) and SS (disulfide) levels were measured and recorded. Results: Comparing intracellular and extracellular thiol levels between groups, intracellular GSSG level and GSSG/GSH percent ratio, and extracellular disulfide and SS/SH percent ratio values were higher in diabetic patients than healthy participants. Choroidal thicknesses were significantly thinner in DRP groups compared to the healthy population. When the relationship between choroidal thicknesses and thiol levels was investigated, there were significant relationships between choroidal thicknesses and thiol levels in group 3. Conclusion: Oxidative stress and impaired intracellular GSH/GSSG and serum SH/SS balances were observed to have an effect on DRP and DME pathogenesis. In addition, in groups with and without DME, thinning in choroidal thicknesses and the relationship between these thicknesses and intra/extracellular oxidative stress indicators can also be explained.

New frontiers and clinical implications in the pathophysiology of age-related macular degeneration

Age-related macular degeneration (AMD) involves progressive degeneration of the central retina, termed the macula, which provides high-acuity vision needed to recognize faces, drive, etc. AMD is the leading cause of blindness in the aging population. A plethora of paradigm-shifting perspectives regarding AMD's multifaceted pathophysiology is emerging. This review will endeavor to gather novel insights and attempts to identify translational implications and new areas of research. The concept of aberrant inflammation being at the center of age-related diseases, particularly AMD, is being received with increasing credence. Retinal angiogenesis, at the forefront of the neovascular complications of AMD (nAMD), is now being understood as an imbalance between trophic factors released by retinal cells secretome. Additionally, mechanisms involving oxidative stress and inflammatory complement pathways have also been identified, along with genetic and other risk factors that play a key role in AMD's onset and progression. Associations have been drawn with AMD and other degenerative deposit diseases such as Alzheimer's disease, atherosclerosis, and glomerulonephritis, which are providing further insight into this maculopathy.

Therapeutic Potential of Pigment Epithelium-derived Factor in Cancer

Pigment epithelium-derived factor (PEDF) is one of the serine protease inhibitors with multifunctional properties, which is produced by various types of organs and tissues. There is an accumulating body of evidence that PEDF plays an important role in the maintenance of tissue homeostasis. Indeed, PEDF not only works as an endogenous inhibitor of angiogenesis, but also suppresses oxidative stress, inflammatory and thrombotic reactions in cell culture systems, animal models, and humans. Furthermore, we, along with others, have found that PEDF inhibits proliferation of, and induces apoptotic cell death in, numerous kinds of tumors. In addition, circulating as well as tumor expression levels of PEDF have been inversely associated with tumor growth and metastasis. These observations suggest that supplementation of PEDF proteins and/or enhancement of endogenous PEDF expression could be a novel therapeutic strategy for the treatment of cancer. Therefore, in this paper, we review the effects of PEDF on diverse types of cancer, and discuss its therapeutic perspectives.

The role of pigment epithelium-derived factor in protecting against cellular stress

Since its discovery as a neurotrophic factor in retinal pigmented epithelium cells in the late 1980s, there has been an increase in understanding of the role that pigment epithelium-derived factor (PEDF) plays in cellular functions. PEDF plays an important role in mediating cellular protection during exposure to oxidative stress and inflammation by preventing stress-induced angiogenesis and apoptosis. PEDF acts to reduce oxidative stress by promoting mitochondrial stability and by regulating the expression of enzymes involved in ROS accumulation and clearance. PEDF protects against the negative effects of oxidative stress by regulating cell survival pathways and the expression of inflammatory and proangiogenic mediators. PEDF-mediated cellular protection may be of clinical importance in diseases characterised by oxidative stress, chronic inflammation and pathological neovascularization, indicating that targeting PEDF may be a potential focus for therapeutic interventions in chronic diseases. In this review, we provide a historical perspective on the discoveries of PEDF interactions and functions, and discuss recent in vitro, in vivo and clinical findings to provide a current summary of the important protective effects following cellular exposure to stress stimuli and future clinical potential of PEDF.

Novel anti-angiogenic PEDF-derived small peptides mitigate choroidal neovascularization

Abnormal migration and proliferation of endothelial cells (EC) drive neovascular retinopathies. While anti-VEGF treatment slows progression, pathology is often supported by decrease in intraocular pigment epithelium-derived factor (PEDF), an endogenous inhibitor of angiogenesis. A surface helical 34-mer peptide of PEDF, comprising this activity, is efficacious in animal models of neovascular retina disease but remains impractically large for therapeutic use. We sought smaller fragments within this sequence that mitigate choroidal neovascularization (CNV). Expecting rapid intravitreal (IVT) clearance, we also developed a method to reversibly attach peptides to nano-carriers for extended delivery. Synthetic fragments of 34-mer yielded smaller anti-angiogenic peptides, and N-terminal capping with dicarboxylic acids did not diminish activity. Charge restoration via substitution of an internal aspartate by asparagine improved potency, achieving low nM apoptotic response in VEGF-activated EC. Two optimized peptides (PEDF 335, 8-mer and PEDF 336, 9-mer) were tested in a mouse model of laser-induced CNV. IVT injection of either peptide, 2-5 days before laser treatment, gave significant CNV decrease at day +14 post laser treatment. The 8-mer also decreased CNV, when administered as eye drops. Also examined was a nanoparticle-conjugate (NPC) prodrug of the 9-mer, having positive zeta potential, expected to display longer intraocular residence. This NPC showed extended efficacy, even when injected 14 days before laser treatment. Neither inflammatory cells nor other histopathologic abnormalities were seen in rabbit eyes harvested 14 days following IVT injection of PEDF 336 (>200 μg). No rabbit or mouse eye irritation was observed over 12-17 days of PEDF 335 eye drops (10 mM). Viability was unaffected in 3 retinal and 2 choroidal cell types by PEDF 335 up to 100 μM, PEDF 336 (100 μM) gave slight growth inhibition only in choroidal EC. A small anti-angiogenic PEDF epitope (G-Y-D-L-Y-R-V) was identified, variants (adipic-Sar-Y-N-L-Y-R-V) mitigate CNV, with clinical potential in treating neovascular retinopathy. Their shared active motif, Y - - - R, is found in laminin (Ln) peptide YIGSR, which binds Ln receptor 67LR, a known high-affinity ligand of PEDF 34-mer.