Expression of genes involved in the NF-κB-dependent pathway of the fibrosis in the mare endometrium.

Equine endometrosis is a multifactorial chronic degenerative condition, considered to be one of a major causes of equine infertility. The formation of periglandular fibrosis seems to be linked to chronic inflammation of the mare endometrium in a paracrine way and in a response to numerous forms of inflammatory stimuli elicit the net deposition of extracellular matrix (ECM) around the endometrial glands and stroma. We hypothesized some of these stimuli, such as monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and hyaluronan synthases (HASs), may share the nuclear factor-κB (NF-κB) dependent activation pathway. This study aimed to determine whether mRNA expression of MCP-1, IL-6, HASs, and proteins of canonical (RelA/NK-κβ1) and noncanonical (NK-κβ2) signaling pathways for NF-kB would change in subsequent categories of endometrosis during the estrous cycle. The expression of selected genes was established in mare endometrium (n = 80; Kenney and Doig categories I, IIA, IIB, III), obtained in the follicular phase (FLP) and mid-luteal phase (MLP). The high expression of RelA mRNA was observed in III, whereas of NK-κβ1 and NK-κβ2 also in IIA, and IIA and IIB, respectively. The expression of MCP-1 mRNA occurred constantly, regardless of the category, whereas IL-6 mRNA was low in IIA, IIB, and III. The expression of HAS 1 was high in IIA and HAS 3 in IIA, IIB, and III. All those changes were observed in FLP, but not MLP. Our results suggest that NF-κB may be involved in progression of the chronic degenerative condition of the mare endometrium, on both canonical and noncanonical pathways. The most important changes in target genes expression were observed only in FLP, which may suggest the hormone-dependent activation of the NF-κB-dependent fibrosis pathway.

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Declaration of competing interest The authors declare that there is no conflict of interests regarding the publication of this paper.