A Study on the Occurrence of Polyovular Follicles in Porcine Ovaries with Particular Reference to Intrafollicular Hormone Concentrations, Quality of Oocytes and their in vitro Fertilization

Abstract

The aim of this study was to identify the occurrence of polyovular follicles in porcine ovaries. We investigated the presence of such follicles in relation to age, and compared the intrafollicular concentrations of steroid hormones between poly- and uniovular follicles. Then we measured the size, viability and the in vitro fertilizing ability of the oocytes from polyovular follicles. Histological examinations documented the occurrence of polyovular follicles in pigs at various stages of follicular growth. Within antral follicles, the number of polyovular follicles was higher in the ovaries of gilts than in sows (P < 0.01). We noticed differences in the viability and size of oocytes recovered from the same follicles. We noted a higher concentration of oestradiol-17beta and a lower concentration of progesterone in polyovular follicles as compared with uniovular follicles (P < 0.01). The amount of embryos after in vitro-fertilization of oocytes from polyovular follicles was significantly lower than that from uniovular ones. Nevertheless, we found that some oocytes from polyovular follicles also have the capacity to be fertilized in vitro and be developed to the blastocyst stage.

The morphology of porcine oocytes is associated with zona pellucida glycoprotein 3 and integrin beta 2 protein levels--

“…Direct correlations between follicular size and quality of the resulting oocytes have previously been described by several authors (Humblot et al, 2005;Mourot et al, 2006;Feng et al, 2007). However, Stankiewicz et al (2009) found several differences in the viability and size of oocytes isolated from the same polyovular follicles, indicating that even the same follicle can contain a highly heterogeneous group of oocytes. On the other hand, Antosik et al (2009) demonstrated that porcine follicular size is highly associated with the expression of genes encoding proteins responsible for the fertilization ability of oocytes.…”

Concentrations of bone morphogenetic protein-15 (BMP-15) and growth differentiation factor-9 (GDF-9) in follicular cysts, mono - and polyoocyte follicles in gilts

“…This might be the result of a diversifi ed secretory activity of oocytes from polyooocyte follicles. This suggestion found its confi rmation in the studies conducted by Stankiewicz et al [18], who demonstrated the varied quality of oocytes from polyoocyte follicles. On the other hand, regardless of the number of oocytes and their secretory activity within a follicle, there might be mechanisms responsible for the maintenance of an optimal BMP-15 and GDF-9 concentration to provide for folliculogenesis.…”

“…Research into the role of BMP-15 and GDF-9 in the ovarian follicle prove that the mentioned factors are secreted mainly by oocytes. The majority of ovarian follicles contains only one oocyte; however, in some mammal species, there are follicles containing a higher number of oocytes [16][17][18]. The presence of polyoocyte follicles has been recorded, amongst others, in the ovaries of the pig [18].…”

“…Follicular fl uid was aspired from same-sized follicles (7-10 mm in diameter). To determine the number of oocytes, follicular fl uid was aspired with the use of a separate syringe with a fi tted needle, and then transferred into individual wells, according to the method by Stankiewicz et al [18]. In order to minimise errors related to the possibility of oocyte loss, after each aspiration of a single follicle the syringe was rinsed out several time and its contents were transferred to another well.…”

“…The majority of ovarian follicles contains only one oocyte; however, in some mammal species, there are follicles containing a higher number of oocytes [16][17][18]. The presence of polyoocyte follicles has been recorded, amongst others, in the ovaries of the pig [18]. Determining BMP-15 and GDF-9 concentrations in polyoocyte follicle fl uid perhaps may indirectly indicate the level of oocyte secretion activity in the follicles, especially as there has been no explicit common standpoint regarding the quality of such oocytes.…”