University of Tehran Iranian Journal of Veterinary Medicine 2251-8894 20 2 2026 03 01 Inflammation and Apoptosis Factors in Mares’ Follicular Fluid Regarding Seasonal Cyclicity 233 242 106047 10.32598/ijvm.20.2.1005897 EN Lyudmila Fedorovna Lebedeva Department of Physiology, The All-Russian Research Institute for Horse Breeding Named After Academy Member V.V. Kalashnikov, Divovo, Russia. 0000-0001-6960-5233 Olga Victorovna Bakovetskaya Department of Biology, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. & Department of Вiochemistry, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. Anna Alexandrovna Terekhina Department of Biology, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. & Department of Вiochemistry, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. 0000-0002-4824-5918 Elena Vladimirovna Solodova Department of Physiology, The All-Russian Research Institute for Horse Breeding Named After Academy Member V.V. Kalashnikov, Divovo, Russia. Yulia Vladimirovna Abalenikhina Department of Biology, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. & Department of Вiochemistry, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. Alexey Vladimirovich Shchulkin Department of Biology, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. & Department of Вiochemistry, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. Svetlana Sergeevna Balashova Department of Biology, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. & Department of Вiochemistry, Ryazan State Medical University Named After Academician I.P. Pavlov, Ryazan, Russia. Journal Article 2025 09 05 <strong>Background</strong>: The in vitro production of human and animal embryos rapidly has been developed in recent years. The year-round practice of obtaining oocytes from valuable mares does not account for seasonal changes in the oocyte microenvironment or their potential impact on oocyte quality.<br /><strong>Objectives</strong>: This study aimed to assess levels of inflammation and apoptosis markers in the follicular fluid (FF) of mares during the transitional anovulatory period and the breeding season with normal estrous cycles.<br /><strong>Methods</strong>: The experimental samples included clinically healthy crossbred mares aged 6-12 years. The expression of inflammation and apoptosis factors (interleukin [IL]-1α, IL-1β, Tumor necrosis factor alpha (TNF-α), nuclear factor kappa B [NF-kB], B-cell lymphoma-2 [BCL2], FAS, Bcl-2–associated X protein (Bax), caspase 3) in FF samples from the transitional and ovulatory phases was assessed by Western Blotting.<br /><strong>Results</strong>: The inflammation and apoptosis developed in large FFs (≥31-35 mm) in both periods, evidenced by an increase in the levels of IL-1α, IL-1β, TNFα, FAS, and caspase-3. In luteinizing follicles during the transitional period, anti-apoptotic markers NF-kB and BCL2 reached their peak level, while in large estrous follicles, the level of these markers significantly decreased. This indicated that apoptosis in large FFs is not triggered by TNFα. In hormonally stimulated preovulatory follicles, the level of all inflammation and apoptosis markers decreased except for NF-kB and TNFα. On the contrary, the TNFa reached a maximum level, which could indicate preparation for follicle rupture and the release of a mature oocyte (ovulation).<br /><strong>Conclusion</strong>: The findings indicate the presence of specific regulatory pro- and antiapoptotic mechanisms involved in the preparation of mature follicles for ovulation.  https://ijvm.ut.ac.ir/article_106047_181a9fa6610438a6bf1cfc643a16f648.pdf