RETRACTED: Pigment epithelium-derived factor inhibits erythropoietin-induced retinal endothelial cell angiogenesis by suppression of PI3K/Akt pathway

Pigment Epithelium-Derived Factor as a Possible Treatment Agent for Choroidal Neovascularization

Choroidal neovascularization (CNV) is a sight-threatening disease and is characterized by the formation of pathological neovascularization in the choroid which extends into the subretinal space. Exudative age-related macular degeneration (AMD) is the formation of CNV in the macular area which leads to irreversible blindness. Continuous leakage and hemorrhage of the CNV lesion may eventually result in scarring or later fibrosis, which could result in photoreceptor cell atrophy. The current strategy for treating CNV is the use of antivascular endothelial growth factor (VEGF) agents. Many studies have demonstrated the efficacy of intravitreal anti-VEGF therapy. Other studies have also reported the side effects of single anti-VEGF treatment. And long-term inhibition of a single system may result in collateral damage to other visual elements. Pigment epithelium-derived factor (PEDF) is a 50 kDa protein that was first isolated from the conditioned medium of human RPE cells. PEDF has both antiangiogenesis and neuroprotective functions for photoreceptor cells. It may be a potential ocular antiangiogenic agent. This review outlines the distribution of PEDF in the eye, the mechanism of antiangiogenesis, the protective effect on the retina, and the relationship between PEDF and VEGF.

Enhanced survival of retinal ganglion cells is mediated by Müller glial cell-derived PEDF

The death of retinal ganglion cells (RGC) leads to visual impairment and blindness in ocular neurodegenerative diseases, primarily in glaucoma and diabetic retinopathy; hence, mechanisms that contribute to protecting RGC from ischemia/hypoxia are of great interest. We here address the role of retinal glial (Müller) cells and of pigment-epithelium-derived factor (PEDF), one of the main neuroprotectants released from the glial cells. We show that the hypoxia-induced loss in the viability of cultured purified RGC is due to apoptosis, but that the number of viable RGC increases when co-cultured with Müller glial cells suggesting that glial soluble mediators attenuate the death of RGC. When PEDF was ablated from Müller cells a significantly lower number of RGC survived in RGC-Müller cell co-cultures indicating that PEDF is a major survival factor allowing RGC to escape cell death. We further found that RGC express a PEDF receptor known as patatin-like phospholipase domain-containing protein 2 (PNPLA2) and that PEDF exposure, as well as the presence of Müller cells, leads to an activation of nuclear factor (NF)-κB in RGC. Furthermore, adding an NF-κB inhibitor (SN50) to PEDF-treated RGC cultures reduced the survival of RGC. These findings strongly suggest that NF-κB activation in RGC is critically involved in the pro-survival action of Müller-cell derived PEDF and plays an important role in maintaining neuronal survival.

Expression of pigment epithelium-derived factor in human cutaneous appendages

BACKGROUND

Pigment epithelium-derived factor (PEDF), a 50-kDa glycoprotein and a member of the serine protease inhibitor gene family, is well known as a potent endogenous inhibitor of angiogenesis. However, the expression of PEDF in human cutaneous appendages has not yet been determined.

AIM

To investigate the expression of PEDF in human cutaneous appendages.

METHODS

Immunohistochemical staining was used to detect the expression of PEDF in human cutaneous appendages. Reverse transcriptase PCR, western blotting and indirect immunofluorescence were used to determine the mRNA and protein expression of PEDF on cells of the outer root sheath (ORS). A wound-healing assay was used to determine the effect of different concentrations of PEDF on the migration of ORS cells.

RESULTS

PEDF was expressed in the hair follicle (including epidermal matrix, inner root sheath, ORS and fibrous root sheath), sebaceous glands and eccrine sweat glands. Both protein and RNA expression of PEDF was detected, and expression was localized to both cytoplasm and nucleus of ORS cells. Both interleukin (IL)-4 and IL-17 at 25 ng/mL upregulated the expression of PEDF of ORS cells, with IL-4 having the greater effect. PEDF 50 ng/mL decreased migration of ORS cells.

CONCLUSIONS

PEDF is expressed in human cutaneous appendages and may play a modulatory role in the physiology of ORS cells.

Pigment epithelial-derived factor expression in endometriotic lesions in a rat model of endometriosis

Angiogenesis is a prerequisite for endometriotic lesion formation and development. Pigment epithelium-derived factor (PEDF) is a potential inhibitor of angiogenesis. The objective of this study was to detect PEDF immunolocalization in endometriotic lesions and the correlation with vascular endothelial growth factor (VEGF) and microvascular density (MVD) in a rat model of endometriosis. A subcutaneous endometriosis rat model was established by using auto-transplantation. Expression of PEDF, VEGF and MVD labeled by von Willebrand factor (v-WF) in endometriotic lesions and endometrial tissues was evaluated using immunohistochemical staining. We detected lower PEDF immunostaining and higher VEGF and MVD immunostaining in active lesions in a rat model of endometriosis than that in endometriosis endometrium or control endometrium (P<0.05), but no differences between endometriosis and control endometrium were found (P>0.05). In lesions, PEDF expression was negatively correlated with VEGF expression, MVD or sizes of cysts (P<0.01). On the contrary, both VEGF expression and MVD were positively correlated with lesion sizes (P<0.05). In addition, VEGF expression was positively correlated with MVD (P<0.01). Our results suggest that PEDF might be involved in the pathogenesis of endometriosis and may lead to novel treatment for this disease.

Pigment epithelium derived factor inhibits the growth of human endometrial implants in nude mice and of ovarian endometriotic stromal cells in vitro

Angiogenesis is a prerequisite for the formation and development of endometriosis. Pigment epithelium derived factor (PEDF) is a natural inhibitor of angiogenesis. We previously demonstrated a reduction of PEDF in the peritoneal fluid, serum and endometriotic lesions from women with endometriosis compared with women without endometriosis. Here, we aim to investigate the inhibitory effect of PEDF on human endometriotic cells in vivo and in vitro. We found that PEDF markedly inhibited the growth of human endometrial implants in nude mice and of ovarian endometriotic stromal cells in vitro by up-regulating PEDF expression and down-regulating vascular endothelial growth factor (VEGF) expression. Moreover, apoptotic index was significantly increased in endometriotic lesions in vivo and endometriotic stromal cells in vitro when treated with PEDF. In mice treated with PEDF, decreased microvessel density labeled by Von Willebrand factor but not by α-Smooth Muscle Actin was observed in endometriotic lesions. And it showed no increase in PEDF expression of the ovary and uterus tissues. These findings suggest that PEDF gene therapy may be a new treatment for endometriosis.

Decreased expression of pigment epithelium-derived factor and increased microvascular density in ovarian endometriotic lesions in women with endometriosis

OBJECTIVES

To determine whether women with endometriosis have altered expression of pigment epithelium-derived factor (PEDF) in ovarian endometriotic lesions as compared to women without endometriosis.

STUDY DESIGN

Ectopic and eutopic and normal endometrial tissues were sampled from 40 women with ovarian endometriosis and 20 control women, respectively. Endometrial PEDF expression and microvascular density (MVD) using an antibody to von Willebrand factor (vWF) and alpha-smooth muscle actin (α-SMA) were evaluated by using immunohistochemical staining.

RESULTS

We detected decreased PEDF expression and increased MVD using anti-vWF and -α-SMA in ovarian endometriotic lesions in women with endometriosis compared with the control group. In women with endometriosis, the MVD using anti-vWF and -α-SMA but not PEDF expression in ovarian endometriotic lesions correlated with the size of ovarian endometriotic cysts and the severity of the disease. Moreover, the MVD using anti-vWF was negatively correlated with PEDF expression in control endometrium but not in ovarian endometriotic lesions.

CONCLUSIONS

Our results suggest that decreased PEDF expression and increased MVD in ovarian endometriotic lesions might play an important role in the pathogenesis of ovarian endometriosis.

Reduced levels of serum pigment epithelium-derived factor in women with endometriosis

The authors previously demonstrated decreased levels of pigment epithelium-derived factor (PEDF) in peritoneal fluid of women with endometriosis compared to women without endometriosis. Here, the authors determine whether women with endometriosis have altered levels of PEDF in serum. Peripheral blood samples were collected from 71 women with and without endometriosis (n = 43 and 28, respectively) before laparoscopic surgery. Concentrations of serum PEDF were measured by enzyme-linked immunosorbent assay. We detected lower levels of serum PEDF in women with endometriosis (16.3 ± 6.6 ng/mL) than in those without endometriosis (24.5 ± 7.3 ng/mL; P < .001). In women with endometriosis, the concentrations of serum PEDF were significantly lower in women with pain (n = 11, 12.6 ± 7.1 ng/mL) compared to women without pain (n = 32, 17.5 ± 6.0 ng/mL; P < .05). However, the concentrations of serum PEDF did not correlate with disease stage or site or infertility. In addition, the concentrations of serum PEDF did not show any difference in the phase of the cycle in either group. Our results suggest that reduced levels of serum PEDF in women with endometriosis and disease-related pain may play a role in the pathogenesis of this disease.

Mediators involved in retinopathy of prematurity and emerging therapeutic targets

Retinopathy of prematurity (ROP) is a potentially blinding disease of premature infants and despite timely treatment some infants develop retinal detachment and sight loss. Current treatment utilises laser therapy which causes destruction of treated retinal tissue resulting in field loss. There is considerable research work ongoing on neovascular eye disease which is likely to result in antiangiogenic approaches that will arrest the development of ROP by specifically targeting the involved molecular mediators. Some of these new therapeutic interventions have entered clinical trials. This article reviews new information available on the molecular pathogenesis of ROP which may result in novel treatments for ROP; it does not discuss the well-known role of oxygen in the development of ROP.

Erythropoietin induces lymph node lymphangiogenesis and lymph node tumor metastasis

Cancer therapy often produces anemia, which is treated with erthropoietin (EPO) to stimulate erythrocyte production. However, concerns have recently arisen that EPO treatment may promote later tumor metastasis and mortality. The mechanisms underlying such effects are unknown, but it is clear that EPO has pleiotropic effects in cell types other than hematopoietic cells. In this study, we investigated how EPO affects lymphangiogenesis and lymph node tumor metastasis in mouse models of breast cancer and melanoma. In these models, EPO increased lymph node lymphangiogenesis and lymph node tumor metastasis in a manner associated with increased migration, capillary-like tube formation, and dose- and time-dependent proliferation of human lymphatic endothelial cells. EPO increased sprouting of these cells in a thoracic duct lymphatic ring assay. These effects were abrogated by cotreatment with specific inhibitors of phosphoinositide 3-kinase or mitogen-activated protein kinase, under conditions in which EPO increased Akt and extracellular signal-regulated kinase 1/2 phosphorylation. Intraperitoneal administration of EPO stimulated peritoneal lymphangiogenesis, and systemic treatment of EPO increased infiltration of CD11b(+) macrophages in tumor-draining lymph nodes. Finally, EPO increased VEGF-C expression in lymph node-derived CD11b(+) macrophages as well as in bone marrow-derived macrophages in a dose- and time-dependent manner. Our results establish that EPO exerts a powerful lymphangiogenic function and can drive both lymph node lymphangiogenesis and nodal metastasis in tumor-bearing animals.

Decreased concentrations of pigment epithelium-derived factor in peritoneal fluid of patients with endometriosis

To determine whether patients with endometriosis have altered levels of pigment epithelium-derived factor (PEDF) in peritoneal fluid, concentrations of PEDF in peritoneal fluid collected from 42 patients with endometriosis and 30 patients without endometriosis were measured with enzyme-linked immunosorbent assay. We detected significantly lower levels of peritoneal fluid PEDF in patients with endometriosis compared with patients without endometriosis, suggesting that peritoneal fluid PEDF plays a role in the pathogenesis of this disorder.