Expression of genes involved in the NF-kB-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-kB (NF-kB)
dependent activation pathway. This study aimed to determine whether mRNA expression of MCP-1, IL-6,
HASs, and proteins of canonical (RelA/NK-kb1) and noncanonical (NK-kb2) 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 ¼ 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 mRNAwas
observed in III, whereas of NK-kb1 and NK-kb2 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-kB 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-kB-dependent fibrosis pathway.