Whole-Body Vibration Induces Structural Remodeling of Skeletal Muscle Fibers and Neuromuscular Junctions in Oophorectomized Wistar Female Rats.

Menopause-associated hypoestrogenism promotes structural and functional alterations in skeletal muscle, contributing to muscle structural adaptation and neuromuscular impairment. Whole-body vibration (WBV) has emerged as a potential non-pharmacological intervention to attenuate these alterations; however, its effects on skeletal muscle fibers and neuromuscular junctions (NMJs) under hypoestrogenic conditions remain incompletely understood. This study investigated the effects of WBV on the extensor digitorum longus (EDL) muscle of oophorectomized Wistar rats. Sixty-four female Wistar rats were allocated into four experimental groups: SHAM-SED, SHAM-WBV, OOPHX-SED, and OOPHX-WBV. Sixty days after surgery, animals assigned to WBV groups were subjected to mechanical vibration (60 Hz, 2 mm, 10 min/session, three times weekly) for 8 weeks. Morphological, morphometric, ultrastructural, and NMJ analyses were performed in the EDL muscle. Oophorectomy promoted significant skeletal muscle remodeling, characterized by reduced muscle fiber cross-sectional area, altered fiber-type distribution, reduced NMJ dimensions, and decreased myonuclear parameters. WBV treatment induced additional structural adaptations, including increased NMJ area and altered sarcomere organization. Ultrastructural analysis demonstrated increased Z-line dissolution in WBV-treated animals. Although WBV promoted neuromuscular remodeling, it did not prevent the reduction in muscle fiber size associated with oophorectomy. These findings demonstrate that hypoestrogenism induces significant structural alterations in skeletal muscle and NMJs, while WBV promotes selective neuromuscular and ultrastructural reorganization in oophorectomized animals. The results indicate that WBV induces selective structural and neuromuscular remodeling, although its effects on muscle fiber preservation appear limited under hypoestrogenic conditions.