The effect of lysophosphatidic acid on myometrial contractility and the mRNA transcription of its receptors in the myometrium at different stages of endometrosis in mares.

BACKGROUND: Endometrosis (chronic degenerative endometritis) results in morphological changes in the equine endometrium and impairs its secretory function. However, the effect of this condition on the myometrium remains unclear. Lysophosphatidic acid (LPA) may affect female reproductive function and embryo transport by influencing uterine contractility through its receptors (LPARs). The objective of this study was to determine myometrial LPAR1-6 mRNA transcription, and the effects of LPA on myometrial contractions in mares with endometrosis during the mid-luteal and follicular phases of the estrous cycle. RESULTS: A reduction in myometrial LPAR1 mRNA transcription was observed in mares with endometrosis during the mid-luteal phase, in comparison to those with category I endometria (P < 0.05). While, upregulation of myometrial LPAR3 or LPAR6 mRNA transcription was observed in mares with category III or IIB endometria; respectively (P < 0.05). An increase in myometrial LPAR1, LPAR3 and LPAR5 mRNA transcription was observed during the follicular phase in mares with category IIA endometrium in comparison to their expression in category I endometrium (P < 0.05). During endometrosis progression LPA reduced the force of myometrial contractions in both phases of the estrous cycle (P < 0.05). However, in mares with category IIA endometrium during the follicular phase, LPA was found to increase the force of contraction of myometrial strips in comparison to mares with category I endometrium (P < 0.01). CONCLUSION: In the course of endometrosis in mares, a disruption in the myometrial mRNA transcription of LPARs has been observed. This is the first study to examine the impact of LPA on myometrial contractility at diffrent stage of endometrosis. However, it is essential to consider that multiple factors may contribute to this process. Alternations in contractile activity and changes in myometrial LPARs mRNA transcription may indicate impaired LPA-signaling mechanisms in equine myometrium during endometrosis.