Methylation-mediated down-regulation of microRNA-497-195 cluster confers osteogenic differentiation in ossification of the posterior longitudinal ligament of the spine via ADORA2A

Hsa-miR-15b-5p/miR-195-5p Controls Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells Through Regulating Indian Hedgehog Expression

Osteoblastogenesis is regulated by several signaling pathways like hedgehog signaling. Of three types of mammalian Hedgehog genes, the Indian Hedgehog (Ihh) plays an important role in the formation of the skeleton. Mesenchymal stem cells (MSCs) isolated from adipose tissue have been considered a good source of osteoblast differentiation. Evidence also suggests that miRNAs play an important role in regulating key stages of osteoblast differentiation. In this study, two miRNAs targeting the Ihh were predicted by using bioinformatics analysis. ASCs were successfully derived, purified, and characterized from human adipose tissue. ASCs were chemically induced into osteoblast cells. Then, differentiation was confirmed by alkaline phosphatase (ALP) activity and Alizarin red staining. The relative expression of Ihh and related miRNAs was evaluated after 0, 7, 14, and 21 from the differentiation duration. The results of bioinformatics data showed that has-miR-195-5p and has-miR-15b-5p target the Ihh gene. The expression of Ihh significantly increased in a time-dependent manner in the differentiation process. In contrast, miR-195-5p and miR-15b-5p were significantly downregulated dependent on time duration (P < 0.01). Overall, the data indicate the antithetical regulation of Ihh versus has-miR-195-5p and has-miR-15b-5p during the differentiation process. These results support the hypothesis that these mi-RNAs could target the Ihh in the pathway of osteoblast differentiation derived from human ASCs.

Synergetic effect of 3D porous microsphere structure and activation of adenosine A2B receptor signal on promoting osteogenic differentiation of BMSCs

Biodegradable microspheres offer great potential as functional building blocks for bottom-up bone tissue engineering. However, it remains challenging to understand and regulate cell behaviors in fabrication of injectable bone microtissues using microspheres. The study aims to develop an adenosine functionalized poly (lactide-co-glycolide) (PLGA) microsphere to enhance cell loading efficiency and inductive osteogenesis potential, and subsequently to investigate adenosine signaling-mediated osteogenic differentiation in cells grown on three-dimensional (3D) microspheres and flat control. Adenosine was loaded on PLGA porous microspheres via polydopamine coating, and the cell adhesion and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were improved on these microspheres. It was found that adenosine A2B receptor (A2BR) was further activated by adenosine treatment, which consequently enhanced osteogenic differentiation of BMSCs. This effect was more obvious on 3D microspheres compared to 2D flats. However, the promotion of osteogenesis on the 3D microspheres was not eliminated by blocking the A2BR with antagonist. Finally, adenosine functionalized microspheres could fabricate injectable microtissues in vitro, and improve cell delivery and osteogenic differentiation after injection in vivo. Therefore, it is considered that adenosine loaded PLGA porous microspheres will be of good value in minimally invasive injection surgery and bone tissue repair.

Non-coding RNAs in ossification of the posterior longitudinal ligament

Ossification of the posterior longitudinal ligament (OPLL) is a kind of disease that involves a variety of factors leading to ectopic bone deposition of the spinal ligament. Although the detailed mechanism is not clear, genetic factors play important roles in the development of this disease. Noncoding RNA (ncRNA) refers to an RNA molecule that is not translated into a protein but participates in the regulation of gene expression. Functionally important types of ncRNA associated with OPLL include long noncoding RNA, microRNA, and circular RNA. We listed the differentially expressed ncRNAs in OPLL patients and normal controls to find the ncRNAs most relevant to the pathogenesis of the disease. The potential regulatory networks of ncRNA in OPLL cells were analyzed based on their most abundant signal transduction pathway data. The analysis of the highly connected ncRNAs in the regulatory network suggests that they play an important role in OPLL. These findings provide new directions for the study of OPLL pathogenesis and therapeutic targets. In this paper, we reviewed and analyzed the literature on ncRNAs in OPLL published in recent years, aiming to help doctors better understand and treat this disease.

Epigenetic modifications in spinal ligament aging

Spinal stenosis is a common degenerative spine disorder in the aged population and the spinal ligament aging is a main contributor to this chronic disease. However, the underlying mechanisms of spinal ligament aging remain unclear. Epigenetics is the study of heritable and reversible changes in the function of a gene or genome that occur without any alteration in the primary DNA sequence. Epigenetic alterations have been demonstrated to play crucial roles in age-related diseases and conditions, and they are recently studied as biomarkers and therapeutic targets in the field of cancer research. The main epigenetic modifications, including DNA methylation alteration, histone modifications as well as dysregulated noncoding RNA modulation, have all been implicated in spinal ligament aging diseases. DNA methylation modulates the expression of critical genes including WNT5A, GDNF, ACSM5, miR-497 and miR-195 during spinal ligament degeneration. Histone modifications widely affect gene expression and obvious histone modification abnormalities have been found in spinal ligament aging. MicroRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) exert crucial regulating effects on spinal ligament aging conditions via targeting various osteogenic or fibrogenic differentiation related genes. To our knowledge, there is no systematic review yet to summarize the involvement of epigenetic mechanisms of spinal ligament aging in degenerative spinal diseases. In this study, we systematically discussed the different epigenetic modifications and their potential functions in spinal ligament aging process.