The growth of ovarian follicle and corpus luteum development is dependent on angiogenesis, the proliferation of new capillaries frompre-existing vessels. The morphological changes driven by angiogenesis ensure the adequate metabolic support to the follicularlutealcomplex and are essential for fertility. However, the morphofunctional relation between neoangiogenesis and fertility are notyet fully understood, especially in the time between the LH surge and ovulation (periovulatory period). In this stage, somatic follicularcells rapidly differentiate in luteal steroidogenic cells. The metabolic switch, from an estrogen-to-steroidogenic activity, is sustainedby extensive blood vessel remodelling. The purpose of this work was to describe the sequence of vascular remodelling events, rapidlyoccurring during the periovulatory period. Preovulatory, early periovulatory and late periovulatory follicles were obtained at aprecise timing from prepubertal gilts stimulated by a validated hormonal protocol (eCG+hCG). The swine model was chosen due toa long periovulatory window (40-44 h, as in human). The three-dimensionality of the blood vessel network, the presence of angiogenesisand the patterns of angiogenic figures (sprouting or non-sprouting angiogenesis), were analysed by means of scanningelectron microscopy of vascular corrosion casts. Results showed the presence of three concentric vascular plexuses (inner, mediumand outer) in all groups. In the inner network, a high angiogenic activity was evidenced in preovulatory follicles, as demonstratedby a dense carpet of capillaries, with sprouting angiogenic figures. In early periovulatory follicles, the layer compactness decreasedin consequence of an elongation of capillaries. The pattern of angiogenic figures was similar to the previous group. Close to the ovulation,in late periovulatory follicles, evident modifications in the vessel architecture were observed. The inner layer became undulated,as several folds were visible on its surface. Many gaps showed the characteristics of the underlying medium layer. Sproutingand non-sprouting angiogenesis, as intussusception, were visible. From the data obtained it is possible to conclude that the follicularangiogenesis in pig is high during the preovulatory phase, while the periovulatory period is constituted by a first step of quiescencefollowed by a second one of active angiogenesis, characterized by sprouting and, interestingly, non-sprouting angiogenesis. The quiescencestatus, in early periovulatory follicles, represents the starting point for the subsequent metamorphosing process, necessaryto transform them into functional corpora lutea.[...]

Microvascular morphodynamics of swine periovulatory ovarian follicles as studied by SEM of vascular corrosion casts

MARTELLI, Alessandra;RUSSO, Valentina;DI GIACINTO, Oriana;BERARDINELLI, Paolo;BARBONI, Barbara;
2010-01-01

Abstract

The growth of ovarian follicle and corpus luteum development is dependent on angiogenesis, the proliferation of new capillaries frompre-existing vessels. The morphological changes driven by angiogenesis ensure the adequate metabolic support to the follicularlutealcomplex and are essential for fertility. However, the morphofunctional relation between neoangiogenesis and fertility are notyet fully understood, especially in the time between the LH surge and ovulation (periovulatory period). In this stage, somatic follicularcells rapidly differentiate in luteal steroidogenic cells. The metabolic switch, from an estrogen-to-steroidogenic activity, is sustainedby extensive blood vessel remodelling. The purpose of this work was to describe the sequence of vascular remodelling events, rapidlyoccurring during the periovulatory period. Preovulatory, early periovulatory and late periovulatory follicles were obtained at aprecise timing from prepubertal gilts stimulated by a validated hormonal protocol (eCG+hCG). The swine model was chosen due toa long periovulatory window (40-44 h, as in human). The three-dimensionality of the blood vessel network, the presence of angiogenesisand the patterns of angiogenic figures (sprouting or non-sprouting angiogenesis), were analysed by means of scanningelectron microscopy of vascular corrosion casts. Results showed the presence of three concentric vascular plexuses (inner, mediumand outer) in all groups. In the inner network, a high angiogenic activity was evidenced in preovulatory follicles, as demonstratedby a dense carpet of capillaries, with sprouting angiogenic figures. In early periovulatory follicles, the layer compactness decreasedin consequence of an elongation of capillaries. The pattern of angiogenic figures was similar to the previous group. Close to the ovulation,in late periovulatory follicles, evident modifications in the vessel architecture were observed. The inner layer became undulated,as several folds were visible on its surface. Many gaps showed the characteristics of the underlying medium layer. Sproutingand non-sprouting angiogenesis, as intussusception, were visible. From the data obtained it is possible to conclude that the follicularangiogenesis in pig is high during the preovulatory phase, while the periovulatory period is constituted by a first step of quiescencefollowed by a second one of active angiogenesis, characterized by sprouting and, interestingly, non-sprouting angiogenesis. The quiescencestatus, in early periovulatory follicles, represents the starting point for the subsequent metamorphosing process, necessaryto transform them into functional corpora lutea.[...]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11575/14206
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