Selenium Attenuates LPS-Induced Injury in Ovine Granulosa Cells by Protecting Mitochondrial Ultrastructure and Cellular Homeostasis

Lipopolysaccharide (LPS) impairs the function of ovine follicular granulosa cells (GCs), representing a primary cause of follicular atresia. Selenium (Se), an essential trace element, possesses anti-inflammatory and cytoprotective properties; however, its effects on GC ultrastructure remain largely unknown. In this study, primary ovine GCs were exposed to LPS (10 µg/mL) and treated with sodium selenite (25 nM). Transmission electron microscopy (TEM), JC-1 staining, enzyme-linked immunosorbent assay (ELISA), reactive oxygen species (ROS) detection, flow cytometry, and quantitative real-time PCR (qRT-PCR) were employed to evaluate cellular ultrastructure, mitochondrial membrane potential (ΔΨm), and downstream physiological processes. LPS induced severe mitochondrial pyknosis, cristae loss, and reduced ΔΨm, accompanied by inflammation, oxidative stress, apoptosis, and impaired steroidogenesis. Se intervention markedly ameliorated these ultrastructural injuries, preserving mitochondrial morphology and ΔΨm. Functionally, Se suppressed the release of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β); enhanced the activities of antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) while attenuating ROS accumulation; inhibited apoptosis by upregulating BCL-2 and downregulating BAX and CASPASE-3; and restored E2 and P4 secretion via upregulation of STAR and NR5A1. This study provides direct morphological evidence that Se protects ovine GCs from LPS-induced damage by repairing mitochondrial ultrastructure. This structural restoration is central to its integrated anti-inflammatory, antioxidant, anti-apoptotic, and steroidogenic effects. These in vitro findings suggest that Se may serve as a promising nutritional strategy for mitigating inflammation-driven follicular atresia, pending further in vivo validation.