Apparent Involvement of Plasmin in Early-Stage Follicle Rupture During Ovulation in Medaka1

Abstract

Until recently, the role of the proteolytic system involving serine proteases in follicle rupture during ovulation in mammalian species has been a subject of controversy. We undertook the present study to examine whether proteases play a role in follicle rupture using the teleost medaka (Oryzias latipes) model. Various serine protease inhibitors, including a specific plasmin inhibitor, drastically reduced the rate of ovulation, as assessed by an in vitro ovulation assay, which was established for the fish. Biochemical, molecular biological, and immunological analyses demonstrated that plasminogen/plasmin was present in large follicles destined to ovulate. The active protease, plasmin, was detected in follicles approximately 3-7 h before the expected time of ovulation. Specific antibodies against the medaka plasmin light chain suppressed the ovulation rate of the follicles when antibodies were added to the medium during the period in which active plasmin was generated. This finding was an indication that a plasmin-like protease similar if not identical to plasmin plays a role in follicle rupture during ovulation in the medaka. Our data also indicate that this serine protease participates in the rupture for only a few hours prior to the activation of matrix metalloproteinase (Mmp)-mediated hydrolysis at ovulation. Based on our previous and current data, we propose a follicle rupture model involving two different proteolytic enzyme systems, serine protease and Mmp, in medaka ovulation. The current study is the first to provide evidence of the indispensable role of plasmin or a plasmin-like protease in the ovulation of a nonmammalian vertebrate species.

Recent Advances in the Understanding of Teleost Medaka Ovulation: The Roles of Proteases and Prostaglandins

“…In our attempts to identify the proteolytic enzymes responsible for follicle rupture during ovulation, various protease inhibitors were tested in preovulatory follicles using the in vitro ovulation system. Serine protease inhibitors, such as aprotinin, leupeptin, antipain and soybean trypsin inhibitor, and MMP inhibitors, such as EDTA, o-phenanthroline and GM6001, strongly inhibited follicle ovulation in vitro (Ogiwara et al, 2005;Ogiwara et al, 2012), suggesting the involvement of two different proteolytic enzyme systems. Our detailed study demonstrated that the serine protease plasmin plays an indispensable role in follicle rupture during medaka ovulation .…”

“…Downloaded From: https://bioone.org/journals/Zoological-Science on 11 Jul 2020 Terms of Use: https://bioone.org/terms-of-use MMPs is required for successful ovulation (Ogiwara et al, 2005;Ogiwara et al, 2012). A significant role of the PA/ plasmin system is unique in fish ovulation because, as described above, recent evidence has argued against an essential role of the proteolytic enzyme system for follicle rupture during ovulation in mammals.…”

Follicle rupture during ovulation with an emphasis on recent progress in fish models

“…In the past decade, the ECM degradation mechanism that regulates follicle rupture has been explored in the medaka (Ogiwara et al 2005(Ogiwara et al , 2012(Ogiwara et al , 2015. The rupture of follicles in the fish is accomplished by the sequential action of two proteolytic enzyme systems, the urokinase-type plasminogen activator-1 (Plau1)/ plasmin system and the matrix metalloproteinase (MMP) system.…”

Oogenesis in Teleost Fish

“…Further studies using advanced methods such as differential display, subtraction cDNA library and cDNA microarray may provide a way to identify new genes and factors that play a pivotal role in piscine ovulation. Few comprehensive studies revealed important roles for hydrolytic enzymes and metalloproteinases in follicular rupture leading to ovulation (Ogiwara et al 2005(Ogiwara et al , 2012.…”