Apoptosis of endplate chondrocytes in cervical kyphosis is associated with chronic forward flexed neck: an in vivo rat bipedal walking model

• Published in: Journal of orthopaedic surgery and research Vol. 16; no. 1; p. 5
• Main Authors: Lai, Jinliang, Ji, Guanglin, Zhou, Yuqiao, Chen, Jincai, Zhou, Min, Mo, Jianwen, Zheng, Tiansheng
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 04.01.2021; BioMed Central; BMC
• Subjects: Animals; Apoptosis; Bipedal rat; Cervical kyphosis; Cervical Vertebrae - cytology; Cervical Vertebrae - diagnostic imaging; Cervical Vertebrae - pathology; Chondrocyte; Chondrocytes; Chondrocytes - pathology; Chondrocytes - physiology; Chronic Disease; Disease; Disease Models, Animal; DNA nucleotidylexotransferase; DNA polymerases; Enzymes; Ethylenediaminetetraacetic acid; Experiments; Forward flexed neck; Kinases; Kyphosis; Kyphosis - diagnostic imaging; Kyphosis - etiology; Kyphosis - pathology; Labeling; Neck; Neck - pathology; Orthopedics; Pathogenesis; Physiological aspects; Rats; Rats, Sprague-Dawley; Spine (cervical); Transmission electron microscopy; Variance analysis; United States > US; Germany; Forward flexed neck; Cervical kyphosis; Chondrocyte; Bipedal rat; Apoptosis
• ISSN: 1749-799X; 1749-799X
• DOI: 10.1186/s13018-020-02124-4

This study was undertaken to establish a rat bipedal walking model of cervical kyphosis (CK) associated with chronic forward flexed neck and assess the effects of chronic forward flexed neck on endplate chondrocytes. Forty-eight 1-month-old Sprague-Dawley rats were randomly divided into 3 groups: forward flexed neck group (n = 16), bipedal group (n = 16), and normal group (n = 16). Cervical curves were analyzed on a lateral cervical spine X-ray using Harrison's posterior tangent method before the experiment and at 2-week intervals for a 6-week period. Histologic changes in cartilaginous endplate chondrocytes were observed using hematoxylin and eosin (H&E) staining, transmission electron microscopy (TEM), and terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick-end labeling. Radiographic findings suggested a significantly decreased cervical physiological curvature in the forward flexed neck group over the 6-week follow-up; normal cervical curves were maintained in other groups. The average cervical curvature (C2-C7) was - 7.6 ± 0.9° in the forward flexed neck group before the experiment, - 3.9 ± 0.8° at 2 weeks post-experiment, 10.7 ± 1.0° at 4 weeks post-experiment, and 20.5 ± 2.1° at the last follow-up post-experiment. Histologically, results of H&E staining unveiled that cartilaginous endplate chondrocytes were arranged in an irregular fashion, with the decreased number at the observation period; the incidence of apoptotic cells in the forward flexed neck group was noticeably higher at the 6-week follow-up than that in other groups. CK developed as the result of chronic forward flexed neck. Histologic changes suggested that chondrocyte apoptosis may play a critical role in the development of cervical kyphotic deformity associated with chronic forward flexed neck.