Genetic differences in osteogenic differentiation potency in the thoracic ossification of the ligamentum flavum under cyclic mechanical stress

Abstract

Mechanical stress and genetic factors play important roles in the occurrence of thoracic ossification of ligament flavum (TOLF), which can occur at one, two, or multiple levels of the spine. It is unclear whether single- and multiple-level TOLF differ in terms of osteogenic differentiation potency and osteogenesis-related gene expression under cyclic mechanical stress. This was addressed in the present study using patients with non-TOLF and single- and multiple-level TOLF (n=8 per group). Primary ligament cells were cultured and osteogenesis was induced by application of cyclic mechanical stress. Osteogenic differentiation was assessed by evaluating alkaline phosphatase (ALP) activity and the mRNA and protein expression of osteogenesis-related genes, including ALP, bone morphogenetic protein 2 (BMP2), Runt-related transcription factor-2 (Runx-2), osterix, osteopontin (OPN) and osteocalcin. The application of cyclic mechanical stress resulted in higher ALP activity in the multiple-level than in the single-level TOLF group, whereas no changes were observed in the non-TOLF group. The ALP, BMP2, OPN and osterix mRNA levels were higher in the multiple-level as compared to the single-level TOLF group, and the levels of all osteogenesis-related genes, apart from Runx2, were higher in the multiple-level as compared to the non-TOLF group. The osterix and ALP protein levels were higher in the multiple-level TOLF group than in the other 2 groups, and were increased with the longer duration of stress. These results highlight the differences in osteogenic differentiation potency between single- and multiple-level TOLF that may be related to the different pathogenesis and genetic background.

Angiopoietin-2 promotes osteogenic differentiation of thoracic ligamentum flavum cells via modulating the Notch signaling pathway

“…Due to the progressive nature of the ossification and the refractoriness to conservative treatment, TOLF generally requires aggressive surgical intervention[1–4]. Several investigations suggested that potential contributing factors associated with TOLF, such as mechanical effects[5–7], inflammatory factors [8, 9]and genetic factors[10, 11], but the underlying mechanism of TOLF has not yet been clarified.…”

A Transcriptome-Level Study Identifies Changing Expression Profiles for Ossification of the Ligamentum Flavum of the Spine

“…Also, it has been demonstrated that ciRS-7 can repress Alzheimer’s disease (AD) development by suppressing NF-κB protein synthesis and inducing its cytoplasmic localization, promoting UCHL1 expression and UCHL1-induced amyloid precursor protein (APP) and BACE1 ubiquitination and degradation 13 . Moreover, primary ligament cells were preferentially used for transcription profiling in most OLF research 42, 43. In this study, for the first time, we used normal and ossified ligament tissues for transcription profiling, which reflect more closely the change in expression of ncRNAs and mRNA of OLF in vivo .…”

Identification of crucial miRNAs and lncRNAs for ossification of ligamentum flavum

“…Although the pathogenesis of OLF remains to be elucidated, abnormal expression of osteogenic differentiation and cell proliferation related genes in LF cells may serve important roles (8). The mRNA levels of osteogenic markers [alkaline phosphatase (ALP), runt-related transcription factor 2, osterix and osteopontin)] in addition to signaling pathway genes [bone morphogenetic proteins (BMPs), Wnt/β-catenin and Notch] (9,10), were identified to be higher in patients with OLF compared with non-OLF subjects. Recombinant BMP2 or BMP14 [also known as growth/differentiation factor (GDF) 5] modification induced the osteoblastic differentiation of LF cells and promoted bone nodule formation, finally triggering neurological impairment in rat models (11,12), while downregulation of Notch2 ameliorated the processes (10).…”