The role of autophagy in ossification of the human ligamentum flavum / 中国组织工程研究

BACKGROUND: Pathological mechanism of ossification of the ligamentum flavum is unclear. There is no effective drug or non-surgical treatment in clinical practice. Current studies have found that osteopontin and autophagy play an important role in the process of osteogenesis, but their role in ossification of the ligamentum flavum has not been elucidated. OBJECTIVE: To seek for the potential target of drug therapy by exploring the mechanism of ossification of the ligamentum flavum. METHODS: (1) Surgical specimens of the ligamentum flavum were taken from patients with ossification of the ligamentum flavum, thoracic vertebrae or simple lumbar disc herniation undergoing posterior total laminectomy and decompression. These specimens were divided into two groups: An ossification group and a non-ossification group. Eight specimens from each group were collected. Osteopontin, osteocalcin and autophagy indexes Beclin-1, LC3 and P62 were stained by immunohistochemistry. (2) The ligamentum flavum cells were isolated and cultured by adherence method. The third generation cells were treated with osteopontin at different concentrations for different time to construct an in vitro model of ligamentum flavum ossification. (3) Autophagy inhibitor 3-methyladenine with different concentrations was used to intervene with non-ossified ligamentum flavum cells, followed by induction with 100 μg/L osteopontin. Western blot assay was used to detect the expression of alkaline phosphatase, osteocalcin. (4) Non-ossified ligamentum flavum cells were induced with 100 μg/L osteopontin, and the induction was terminated at 0, 15, 30, 60, and 120 minutes, respectively. The phosphorylation of ERK1/2, JNK and P38, which are important molecules in the MAPK signaling pathway, was detected by western blot. (5) Finally, after inhibition by ERK1/2 phosphorylation blocker U0126, the expression of alkaline phosphatase and osteocalcin was detected by western blot after induction with 100 μg/L steopontin. RESULTS AND CONCLUSION: (1) Immunohistochemical staining of osteopontin and osteocalcin in ossified and non-ossified ligamentum flavum was positive. In the ossified ligamentum flavum, Beclin-1 was positive, but LC3 and P62 were not. Beclin-1, LC3 and P62 were all positive in the non-ossified ligamentum flavum. (2) The expression of alkaline phosphatase and osteocalcin in the ossified ligamentum flavum cells was higher than that in the non-ossified ligamentum flavum cells. Osteopontin could induce ossification of the ligamentum flavum in a concentration- and time-dependent manner. (3) The degree of ossification was negatively correlated with the degree of autophagy, that is, the more obvious autophagy was, the weaker ossification was. (4) Osteopontin could phosphorylate the MAPK signaling pathway in a time-dependent manner. After inhibiting the phosphorylation of MAPK, osteopontin could still induce the ossification of ligamentum flavum cells. To conclude, in the process of ligamentum flavum ossification, the upstream and downstream relationships of ERK1/2, osteopontin, alkaline phosphatase and osteocalcin molecules in signaling pathway are ERK1/2→osteopontin→osteocalcin/alkaline phosphatase.

Compressive Myelopathy Due to Ossification of the Ligamentum Flavum: Case Report and Review of the Literature

Ossification of the ligamentum flavum (OLF) is a rare condition in which the ligamentum flavum, due to mechanical, biological and genetic factors, becomes ossified. Due to its nature and anatomic location, OLF produces symptoms characteristic of spinal cord compression. The diagnostic confirmation is based primarily on imaging tests such as computed tomography (CT) and magnetic resonance imaging (MRI). Ossification of the ligamentum flavum most often affects Asian populations, rarely occurring in black people. The authors report a case of a 61-year-old black man with progressive paraparesis due to OLF, and review the literature regarding the pathology's prevalence, pathogenesis, clinical features, diagnosis, treatment and prognosis.

A ossificação do ligamento flavo (OLF) é uma doença rara na qual o ligamento flavo se torna ossificado devido a fatores mecânicos, biológicos e genéticos. Devido à sua natureza e localização anatômica, a OLF produz sintomas característicos de compressão da medula espinhal. A confirmação diagnóstica baseia-se principalmente em exames de imagem, como tomografia computadorizada (TC) e ressonância magnética (RM). A OLF afeta mais comumente populações asiáticas, raramente sendo observada em pacientes negros. Os autores relatam o caso de um homem negro de 61 anos com paraparesia progressiva decorrente de OLF com uma revisão da literatura a respeito da prevalência, patogênese, aspectos clínicos, diagnóstico, tratamento e prognóstico desta patologia.

Clinical characteristics and operative treatment of the ossification of ligamentum flavum thoracic spinal stenosis / 中国矫形外科杂志

[Objective]To evaluate the clinical characteristics and effect of operative treatment for the ossification of ligamentum flavum thoracic spinal stenosis (OLF-TSS). [Methods]From October 1998 to February 2007,38 patients with OLF-TSS were treated with en bloc hemi-articular process laminectomy. In this group,25 cases were male,and 13 cases were female. The average age was 48 years (range,29～71 years). Totally 81.6% of the lesion was between T10～L1 intervertebral disc space.The average history was 10 months. There were 5.3 percent with protrusion of intervertebral disc of thoracio spine.[Results]Thirty-eight cases were followed-up for 1～8 years,with an average of 3 years and 6 months. Dural injury occurred in 4 cases of 38,3 cases appeared postoperative cerebrospinal fluid leakage. All cases were cured conservatively mainly with bed rest in the prostrate position. According to WANG's evaluation,25 had excellent results,11 had good results,2 had no change and none was poor,The excellent to good rate was 94.7% in this group. There were no patients with the wrong level. No patient neurological functions were deteriorated.[Conclusion]The chinical features of OLF-TSS are very complex. The common symptoms of the disease are progressive onset of numbness,weakness,low back pain,intermittent claudication of the lower extremities,constriction on trunk or lower limbs and sphincter dysfunction. The clinical presentation and neurological examination associated with X-ray film,MRI and CT were the important means of the diagnosis of the disease. Removal of the posterior wall of the thoracic spinal canal via the technique of en bloc hemi-articular process laminectomy is safe and effective to treat OLF-TSS. The strategy for diminishing fault and complications is to discriminate pathogenic segment (locating-diagnosis) and follow the principles of surgical procedure.

Thoracic Stenosis Secondary to Ossification of the Ligamentum Flavum

The thoracic portion of the spinal cord is susceptible to compression by hypertrophic ossification of the spinal ligament in the thoracic spinal canal. Unlike ossification of the posterior longitudinal ligament(OPLL) in the cervical spine, however, thoracic myelopathy due to ossification of the ligamentum flavum(OLF) may be overlooked, misdiagnosed, or treated inappropriately. This is mainly because of lack of knowledge of this condition. We therefore describe our experience with 22 cases of thoracic myelopathy secondary to ossification of the ligamentum flavum among 45 cases of thoracic stenosis. The clinical manifestations of this condition and the results of its surgical treatment are described. The most common cause of thoracic stenosis was OLF(48.9%) and the most common symptoms were numbness or tingling in the legs(81.8%) and motor weakness of the lower extremities(72.7%). Radiologically, OLF occurred mainly at intervertebral segments T9-T10 through T12-L1(86.2%), the most prevalent site was T11-T12(31.0%). Most OLF involved multiple intervertebral segments(81.8%) particularly two or three segments (59.1%). Eleven of the 22 patients were also suffering from other ossified conditions such as OPLL(45.5%) at other spinal sites, suggesting that ossification has a common underlying etiology. According to the authors' experience, surgical treatment, particularly laminectomy, was usually successful and outcomes were very promising(excellent, 27.3% ; good, 45.5%). OLF of the thoracic spine is no longer an uncommon condition and the authors believe that early diagnosis and appropriate surgical treatment, before irreversible damage to the spinal cord has occurred, may be the key to better results.