Influence of seminal plasma, spermatozoa and semen extender on cytokine expression in the porcine endometrium after insemination

The effects of semen components or extender alone on the expression of selected cytokines [interleukine (IL)-1β, IL-6, granulocyte-macrophage colony stimulating factor (GM-CSF), IL-10 and transforming growth factor (TGF)-β1] on the porcine endometrium were studied, as well as the presence of polymorphonuclear neutrophilic granulocytes (PMNs). In experiment (Exp) I, groups of gilts were sampled at 5-6 h after insemination with fresh semen in extender (Beltsville thawing solution, BTS), spermatozoa in extender (Spz), seminal plasma (SP), or only BTS (control). In Exp II, gilts were sampled 35-40 h after insemination with Spz, SP, BTS or only catheter inserted (as control). Immunohistochemical (IHC) labelling of IL-6, IL-10 and TGF-β1 was evident, especially in surface and glandular epithelia of the porcine endometrium. There were no consistent differences in IHC-labelling of the cytokines in relation to different treatments. However, the scores for IL-6 and IL-10 in surface epithelium and sub-epithelial connective tissue compartments were higher at 35-40 h than shortly (5-6 h) after treatment. Cytoplasmic labelling in the sub-epithelial connective tissue was observed in scattered individual cells but not in PMNs. Shortly (5-6 h) after insemination, there were no differences between animals inseminated with BTS (control) and the semen components for any of the cytokine mRNAs. Later however, at 35-40 h, lower endometrial expression of TGF-β1 mRNA was observed in the Spz and BTS groups compared with the control (catheter only). The same pattern was found for IL-10 (NS). The mRNA expression of IL-6 in the BTS inseminated group was higher compared to the control group. Insemination with SP resulted in significantly lower PMN cell infiltration in the sub-epithelial connective tissue compared with Spz or BTS groups shortly (5-6 h) after insemination. Later (35-40 h), a significant difference was found between SP (lower) and the control group (only catheter). To conclude, our results show that insemination and/or inseminated components modulated cytokine expression in the gilt endometrium. The semen extender BTS stimulated immune reactivity, as shown by down-regulation of the suppressive cytokine TGF-β1. Insemination with solely SP clearly decreased PMN cell infiltration of the gilt endometrium. However, no clear relation between the cytokines studied and PMN cell presence was found.