Pigment epithelium‐derived factor negates oxidative stress in mouse oocytes

Abstract

Molecular changes, caused by various environmental factors, affect the quality and developmental potential of oocytes. Oxidative stress (OS) is a major factor involved in various gynecologic disorders and/or in aging. Recent studies suggest that elevated reactive oxygen species (ROS) hamper oocyte quality and future embryonic development. Pigment epithelium‐derived factor (PEDF) is a pleiotropic protein, known for its antiangiogenic, anti‐inflammatory, and antioxidative properties. Our previous findings demonstrate the antioxidative role of rPEDF in maintaining granulosa cell viability. In the current study, we examined the ability of PEDF to negate the adverse impact of OS on oocytes. Maturation rate of oocytes exposed to OS was significantly lower than that of control oocytes. The number of mtDNA copies in OS‐exposed oocytes was significantly higher than in control oocytes (>3 times), whereas ATP concentration was significantly lower. Oocytes exposed to OS demonstrated impaired chromosome arrangement at the metaphase plate. PEDF significantly improved maturation rate of untreated OS‐exposed oocytes. Moreover, mtDNA copy number, ATP concentration, and chromosome arrangement at the metaphase plate in rPEDF‐treated OS‐exposed oocytes were restored to the level of control oocytes. Our findings demonstrate that OS hampers the ability of oocytes to undergo proper in vitro maturation. The energetic balance of OS‐exposed oocyte is characterized by excessive mtDNA replication and reduced ATP concentration; it hampers the ability of oocytes to perform high fidelity chromosome segregation. PEDF alleviates this damage, improves the rate of oocyte maturation, and preserves mtDNA level and ATP content, thus enabling oocytes to form proper metaphase plate and improve oocyte competence.

The Role of PEDF in Reproductive Aging of the Ovary

“…We have characterized its expression and demonstrated its importance in maintaining the physiologic ovarian activity [ 19 , 26 , 27 ]. Our latest study points at PEDF’s ability to alleviate oxidative damage in oocytes [ 21 ].…”

“…We have previously demonstrated the ability of rPEDF to overcome the inflicted damage caused by H 2 O 2 [ 20 , 21 ]. Because aging is characterized by elevated OS, we tested the therapeutic potential of rPEDF on the oocytes from the ovaries of RA mice by challenging the oocytes of young and RA mice to undergo IVM, and determined their PBE rate.…”

“…We have previously characterized the role of PEDF in the ovary, and have shown that the GCs of both rodents and humans produce and secrete PEDF in a hormonally-dependent manner, inversely to the upregulation of vascular endothelial growth factor (VEGF); estradiol, luteinizing hormone (LH), and progesterone downregulate the GCs’ PEDF expression and secretion [ 17 , 18 ]. Moreover, our findings demonstrate its anti-angiogenic, anti-inflammatory [ 19 ], and anti-oxidative [ 20 , 21 ] traits, and suggest that several pathologies, such as ovarian hyper-stimulation syndrome (OHSS; [ 17 , 19 ]) and polycystic ovary syndrome (PCOS; [ 22 ]), are associated with a low endogenic ovarian level of PEDF. Our latest study points to the ability of PEDF to attenuate oxidative stress (OS) in oocytes, reflected by improved GVBD and PBE rates, as well as by ATP concentration and mitochondrial DNA (mtDNA) copy number [ 21 ].…”

“…Moreover, our findings demonstrate its anti-angiogenic, anti-inflammatory [ 19 ], and anti-oxidative [ 20 , 21 ] traits, and suggest that several pathologies, such as ovarian hyper-stimulation syndrome (OHSS; [ 17 , 19 ]) and polycystic ovary syndrome (PCOS; [ 22 ]), are associated with a low endogenic ovarian level of PEDF. Our latest study points to the ability of PEDF to attenuate oxidative stress (OS) in oocytes, reflected by improved GVBD and PBE rates, as well as by ATP concentration and mitochondrial DNA (mtDNA) copy number [ 21 ]. Our work, so far, places PEDF as a central factor in the ovary, and an attractive therapeutic agent.…”

“…Young and RA mice were subcutaneously administered with pregnant mare serum gonadotropin (PMSG; Syncro-part, Sanofi, Paris, France; 5 IU and 7.5 IU, respectively). Forty-eight hours later, GV oocytes from each mouse were collected, as previously published [ 21 ]. Briefly, using a 21G needle, whole ovaries were gently punctured, and GV oocytes were released into pre-warmed (37 °C) L-15 culture medium (Biological Industries, Beit-Haemek, Israel), supplemented with penicillin (100 IU/mL); streptomycin (100 mg/mL) (Biological Industries); and milrinone (1 μM; M-4659; Sigma-Aldrich, St. Louis, MO, USA), a phosphodiesterase III inhibitor that prevents spontaneous resumption of the first meiotic division, keeping the oocytes at the GV stage.…”