Cellular differentiation, collagen fibrillogenesis, and apoptosis during myodural bridge development in SD rats

The myodural bridge (MDB) is a conserved vertebrate connective tissue structure linking the suboccipital muscles to the spinal dura mater. Furthermore, multiple experiments have demonstrated that the MDB provides a myogenic driving force for cerebrospinal fluid circulation. It is well established that cell differentiation and apoptosis regulate early tissue development; however, how these processes manifest during MDB development remains unclear. This study investigates the developmental chronology, cellular composition, and ultrastructural changes of the MDB in SD rats, focusing on cell apoptosis METHODS: The study utilized SD rat embryos and newborns. Histological analysis was performed on paraffin-embedded sections using Hematoxylin and Eosin (H&E) and TUNEL staining. Transmission electron microscopy (TEM) was additionally used to evaluate ultrastructural details in a subset of fetal rats.

Histological analysis demonstrated that during rat embryonic development, mesenchymal cells in the atlanto-occipital junction differentiate into fibroblasts and fibrocytes, accompanied by increasing collagen fiber deposition. Apoptosis in this region peaked during mid-gestation (E12-E16) and subsequently declined. Transmission electron microscopy (TEM) corroborated these findings, revealing that fibroblasts begin synthesizing sparse collagen fibers by E16, which progressively organize into parallel bundles during development.

This study demonstrates that MDB development in SD rats involves coordinated cell differentiation, collagen production, and fiber assembly, with apoptosis playing an integral role. Key developmental milestones occur at E14, E16, E18, and P0. These findings establish a foundational understanding of MDB morphogenesis, crucial for elucidating its physiological functions and underlying mechanisms.