The porcine endosalpinx at different reproductive stages : morphology, immune cell infiltration and cytokine expression
Abstract: Fertilization takes place in the lower part of the porcine oviduct and to be successful, a balance between immunological tolerance to allogeneic differences and immune reactivity to foreign pathogens is required. The thesis aims to describe immune cells and morphological changes in different segments [isthmus (Isth), ampulla (Amp) and infundibulum (Inf)] of the porcine oviduct at various stages of the oestrous cycle, after artificial insemination (AI, pre- and post-ovulatory) and during early pregnancy. The expression of pro-inflammatory and suppressive cytokines was also determined (RT-PCR and immunohistochemistry, IHC) in oviductal samples collected after AI with different components (fresh semen, spermatozoa in extender or extender alone) or only catheter inserted (control) in gilts. In cyclic sows, the epithelial morphology of Amp and Inf varied during the oestrous cycle. High levels of pseudostratification, mitotic activity and secretory granules were found at pro-oestrus/oestrus indicating influence of ovarian hormones. Lymphocytes were predominant in the epithelium whereas both lymphocytes and plasma cells were the major cell types in the connective tissue (CNT). Higher numbers of these cells were found in the Inf than in the Isth both in the cyclic sows and in sows after AI. Neutrophils were found mainly in the infundibular CNT, in cyclic sows at pro-oestrus and in pre-ovulatory inseminated sows in one group (40h after AI). In post-ovulatory inseminated sows, the numbers of neutrophils were lower but present for a longer period. In gilts, IHC-labelling for TGF-β1, IL-10 and IL-6 was apparent, especially in the epithelial cells. Higher mRNA expressions of these cytokines were found in the Isth compared with the Inf and the TGF-β1 mRNA expression was higher than that of IL-6 and IL-10 in both segments. Shortly after AI, no difference between treatments could be detected for any of these cytokines but 35-40 h after AI, the TGF-β1 mRNA expressions were higher in gilts inseminated with different semen components than in the control animals (only catheter inserted). Thus, endogenous production of TGF-β1, IL-10 and IL-6 was indicated and suggests that these cytokines have a physiological function in the porcine oviduct. The relatively higher expression of TGF-β1 mRNA indicates that this cytokine exerts an immunomodulatory role, mainly in the isthmic part of the oviduct, and this seems to be enhanced by AI. The differences between the upper and lower part of the porcine oviduct regarding presence of immune cells and expression of cytokines are likely to reflect a local immune modulation.
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