Impact of Polystyrene Microplastics and Bisphenol A Co-Exposure on Epididymal Sperm Maturation, Fertility, and Apoptotic Alterations in Rats

Abstract Exposure to polystyrene microplastics (PS-MPs) and Bisphenol A (BPA) has emerged as a major concern for male reproductive health; however, their combined effects on epididymal function remain poorly understood. The present study investigated the impact of PS-MPs and BPA, individually and in combination, on epididymal structure, biochemistry, sperm maturation, and fertility in adult Wistar rats. Animals were exposed orally to PS-MPs (10 or 40 mg/kg/day) with or without BPA (2 µg/kg/day) for 45 consecutive days. Co-exposure significantly reduced epididymal weight and fertility compared with individual exposures. Marked declines in sperm count, motility, and viability, accompanied by increased sperm abnormalities, were observed particularly in co-exposed groups. Histological analysis revealed degeneration of the pseudostratified epididymal epithelium, basal cell damage, epithelial sloughing, and disruption of smooth muscle and connective tissue integrity. Biochemical analysis demonstrated significant depletion of sialic acid, L-carnitine, and neutral α-glucosidase, indicating severe impairment of epididymal secretory and maturational functions. Enhanced Annexin V and Caspase-3 expression further suggested activation of apoptotic pathways in spermatozoa and epididymal epithelial cells. Pearson’s correlation analysis revealed strong associations between epididymal biochemical alterations and sperm dysfunction. Collectively, these findings demonstrate that BPA potentiates PS-MP-induced epididymal toxicity, resulting in impaired sperm maturation and compromised male fertility.