Insights into the hallmarks of human nucleus pulposus cells with particular reference to cell viability, phagocytic potential and long process formation.

OBJECTIVE: As a main cellular component within the disc, nucleus pulposus (NP) cells play important roles in disc physiology. However, little is known on the biologic hallmarks of human NP cells. Therefore, the present study aimed to address the features of human NP cells. METHODS: Human NP samples were collected from normal cadavers, patients with scoliosis and disc degeneration as normal, disease control and degenerative NP, respectively. The NP samples were studied using transmission electron microscopy and TUNEL assay. Pre-digested NP samples were studied using flow cytometry with PI/Annexin V staining. RESULTS: Both control and degenerative human NP consisted of mainly viable cells with a variety of morphology. Both necrosis and apoptosis were noted in human NP as forms of cell death with increased apoptosis in degenerative NP, which was further confirmed by the TUNEL assay. Phagocytic NP cells had the hallmarks of both stationary macrophages with lysosomes and NP cells with the endoplasmic reticulum. Annulus fibrosus cells have similar morphologic characteristics with NP cells in terms of cell nest, phagocytosis and intracellular organs. Moreover, NP cells with long processes existed in degenerative and scoliotic NP rather than normal NP. When cultured in glucose-free medium, NP cells developed long and thin processes. CONCLUSION: Human degenerative NP consists of primarily viable cells. We present direct and in vivo evidence that both human annulus fibrosus and NP cells have phagocytic potential. Moreover, NP cells with long processes exist in both scoliotic and degenerative NP with lack of glucose as one of the possible underlying mechanisms.

C2-C3 Anterior Cervical Diskectomy and Fusion for Hangman's Fractures with C2 Posterior Dislocation: Technical Notes.

BACKGROUND: The overwhelming majority of hangman's fractures cause anterior dislocation of C2. Hangman's fracture with C2 posterior dislocation is extremely rare; only 1 pediatric case was reported in 2018 to date. This kind of injury cannot be cataloged using current classification schemes, and no established treatment recommendations exist. The purpose of this article is to report a rare case of a hangman's fracture with C2 posterior dislocation, which does not fit into existing classification systems and discuss management technical notes to avoid pitfalls. METHODS: We describe this case, review relevant literature, and share our experience. RESULTS: A 31-year-old male sustained a hangman's fracture with C2 posterior dislocation after he fell into a 50-cm deep roadside ditch when riding a motorcycle. Radiograph and computed tomography on admission showed fractures through both pars of C2 and C2 posterior dislocation. Magnetic resonance imaging on admission showed high T2-weighted signal intensity of cervical spinal cord and compression of the cervical spinal cord by posterior dislocation of the C2 vertebral body. A C2-3 anterior cervical diskectomy and fusion was performed. At 6 months after operation, bony fusion was achieved and magnetic resonance imaging showed the T2-weighted signal hyperintensity of cervical spinal cord before surgery disappeared. CONCLUSIONS: C2-C3 anterior cervical diskectomy and fusion is recommended for hangman's fractures with C2 posterior dislocation. Traction before surgery is not recommended.

Role of miR-155 in the regulation of MMP-16 expression in intervertebral disc degeneration.

The molecular mechanisms of intervertebral disc degeneration (IDD) remain elusive. We found that miR-155 is down-regulated in degenerative nucleus pulposus (NP), and more severe degeneration is correlated with higher matrix metallopeptidase 16 (MMP-16) expression. MMP-16 also degraded matrix aggrecan. Here, we addressed the in vivo miR-155-mediated pathological impact on IDD using a classic puncture mouse model. Lentiviral upregulated-miR-155 or downregulated-miR-155 was transduced into the discs of C57 mice, which was validated by real-time polymerase chain reaction (real-time PCR) and in situ hybridization. Immunohistochemistry and western blotting revealed that up-regulation of miR-155 resulted in down-regulation of MMP-16 and an increase in aggrecan and collagen type II in mouse NP; whereas, down-regulation of miR-155 resulted in up-regulation of MMP-16 and a decrease in aggrecan in mouse NP. Radiographic and histological analysis showed that the up-regulation of miR-155 attenuated IDD, while down-regulation of miR-155 resulted in the deterioration of IDD. These findings indicate that decreased miR-155 contributed to the up-regulation of MMP-16 in vivo, and MMP-16 further degraded aggrecan and collagen type II, leading to the dehydration and degeneration of discs. Our findings revealed a therapeutic role for miR-155 in IDD. © 2017 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1323-1334, 2017.