Dynamics of structural transformations of intervertebral discs in humans in the fetal period

Abstract

BACKGROUND: The process of formation of the intervertebral disc structure remains poorly understood. Therefore, evaluating the forecasts for the development of the disc’s fibrous component as the foundation of its strength and elastic properties in the postnatal period seems appropriate.

AIM: To identify microstructural transformations of the annulus fibrosus and nucleus pulposus in the fetal period and compare them with the ontogenetic orientation of the spinal motion segment.

MATERIAL AND METHODS: The study material included 150 intervertebral discs obtained during autopsy of 50 fetuses. The gestational age of 42 fetuses was in the early fetal period, 8 fetuses were in the late fetal period. Intervertebral discs СV–СVI, ThV–ThVI, LV–SI were examined in each fetus. All histological preparations were stained with hematoxylin and eosin, silver impregnation method, PAS reaction, Alcian blue (pH=1.0), Van Gieson and Weigert stains. For intergroup comparisons, the Kruskal–Wallis, Mann–Whitney, and Newman–Keuls tests were used. Differences were considered statistically significant at p ≤0.05.

RESULTS: Elastic fibers in the late fetal period were found in the annulus fibrosus and the peripheral zone of the nucleus pulposus. The intensity of staining of collagen and elastic fibers was more pronounced in the outer layers of the annulus fibrosus. Analysis of the parameters of the vascular-connective tissue formations showed an increase in their number (p=0.0368) and an increase in the number of vessels in the vascular-connective tissue formations of the intervertebral disc (p=0.0449) in the direction of the lower levels of the spinal motion segments. Differences in these two indicators were obtained between the СV–СVI and LV–SI discs, as well as between the СV–СVI and ThV–ThVI discs. In relation to all the studied morphometric parameters of the vascular-connective tissue formations in the cervical and thoracic spine, no statistically significant differences were obtained between the early and late fetal periods.

CONCLUSION: The development of the intervertebral disc occurs from the peripheral parts to the center; the source for its further development is the fibrous ring.

Keywords

vascular-connective tissue formations / elastic fibers / nucleus pulposus / annulus fibrosus

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