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      Exosomal lncRNA-H19 promotes osteogenesis and angiogenesis through mediating Angpt1/Tie2-NO signaling in CBS-heterozygous mice


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          Rationale: Emerging evidence indicates that the growth of blood vessels and osteogenesis is tightly coordinated during bone development. However, the molecular regulators of intercellular communication in the bone microenvironment are not well studied. Therefore, we aim to investigate whether BMMSC-Exo promotes osteogenesis and angiogenesis via transporting lnc-H19 in the CBS- heterozygous mouse model.

          Methods: Using RT2 lncRNA PCR array screening, we identify a bone-specific, long noncoding RNA-H19 (lncRNA-H19/lnc-H19) in exosomes derived from bone marrow mesenchymal stem cells (BMMSC-Exo) during osteogenesis. Using bioinformatics analysis, we further discovered the seed sequence of miR-106a that could bind to lnc-H19. A luciferase reporter assay was performed to demonstrate the direct binding of miR-106a to the target gene angiopoietin 1 (Angpt1). We employed an immunocompromised Nude mouse model, to evaluate the effects of BMMSC-Exo on angiogenesis in vivo. Using a micro-CT scan, we monitored microstructural changes of bone in the experimental mice.

          Results: BMMSC-Exo possessed exosomal characteristics including exosome size, and typical markers including CD63, CD9, and TSD101. In vitro, BMMSC-Exo significantly promoted endothelial angiogenesis and osteogenesis. Mechanistic studies have shown that exosomal lnc-H19 acts as “sponges” to absorb miR-106 and regulate the expression of angiogenic factor, Angpt1 that activates lnc-H19/Tie2-NO signaling in mesenchymal and endothelial cells. Both of these effects on osteogenesis and angiogenesis are inhibited by antagonizing Tie2 signaling. Treatment of BMMSC-Exo also restored the bone formation and mechanical quality in vivo.

          Conclusion: These findings provide a novel insight into how the extracellular role of exosomal lnc-H19 affects osteogenesis and angiogenesis through competing endogenous RNA networks.

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          Most cited references57

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          Coupling of angiogenesis and osteogenesis by a specific vessel subtype in bone.

          The mammalian skeletal system harbours a hierarchical system of mesenchymal stem cells, osteoprogenitors and osteoblasts sustaining lifelong bone formation. Osteogenesis is indispensable for the homeostatic renewal of bone as well as regenerative fracture healing, but these processes frequently decline in ageing organisms, leading to loss of bone mass and increased fracture incidence. Evidence indicates that the growth of blood vessels in bone and osteogenesis are coupled, but relatively little is known about the underlying cellular and molecular mechanisms. Here we identify a new capillary subtype in the murine skeletal system with distinct morphological, molecular and functional properties. These vessels are found in specific locations, mediate growth of the bone vasculature, generate distinct metabolic and molecular microenvironments, maintain perivascular osteoprogenitors and couple angiogenesis to osteogenesis. The abundance of these vessels and associated osteoprogenitors was strongly reduced in bone from aged animals, and pharmacological reversal of this decline allowed the restoration of bone mass.
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            Is Open Access

            Bone regeneration: current concepts and future directions

            Bone regeneration is a complex, well-orchestrated physiological process of bone formation, which can be seen during normal fracture healing, and is involved in continuous remodelling throughout adult life. However, there are complex clinical conditions in which bone regeneration is required in large quantity, such as for skeletal reconstruction of large bone defects created by trauma, infection, tumour resection and skeletal abnormalities, or cases in which the regenerative process is compromised, including avascular necrosis, atrophic non-unions and osteoporosis. Currently, there is a plethora of different strategies to augment the impaired or 'insufficient' bone-regeneration process, including the 'gold standard' autologous bone graft, free fibula vascularised graft, allograft implantation, and use of growth factors, osteoconductive scaffolds, osteoprogenitor cells and distraction osteogenesis. Improved 'local' strategies in terms of tissue engineering and gene therapy, or even 'systemic' enhancement of bone repair, are under intense investigation, in an effort to overcome the limitations of the current methods, to produce bone-graft substitutes with biomechanical properties that are as identical to normal bone as possible, to accelerate the overall regeneration process, or even to address systemic conditions, such as skeletal disorders and osteoporosis.
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              The H19 locus: role of an imprinted non-coding RNA in growth and development.

              The H19 gene produces a non-coding RNA, which is abundantly expressed during embryonic development and down-regulated after birth. Although this gene was discovered over 20 years ago, its function has remained unclear. Only recently a role was identified for the non-coding RNA and/or its microRNA partner, first as a tumour suppressor gene in mice, then as a trans-regulator of a group of co-expressed genes belonging to the imprinted gene network that is likely to control foetal and early postnatal growth in mice. The mechanisms underlying this transcriptional or post-transcriptional regulation remain to be discovered, perhaps by identifying the protein partners of the full-length H19 RNA or the targets of the microRNA. This first in vivo evidence of a functional role for the H19 locus provides new insights into how genomic imprinting helps to control embryonic growth.

                Author and article information

                Ivyspring International Publisher (Sydney )
                22 June 2021
                : 11
                : 16
                : 7715-7734
                [1 ]Bone Biology Laboratory, Department of Physiology, School of Medicine, University of Louisville, Louisville, KY 40202, USA.
                [2 ]James Graham Brown Cancer Center, Department of Microbiology & Immunology, University of Louisville, KY 40202, USA.
                [3 ]Departments of Orthopaedic Surgery and Bioengineering, School of Medicine and Speed School of Engineering, University of Louisville, Louisville, KY 40202, USA.
                Author notes
                ✉ Corresponding author: Neetu Tyagi, Ph.D., FAPS. Associate Professor, Bone Biology Laboratory, Department of Physiology, Health Sciences Center, A-1201, University of Louisville, Louisville, KY 40202. Phone: 502-852-4145; Fax: 502-852-6239; E-mail: n0tyag01@ 123456louisville.edu .

                Competing Interests: The authors have declared that no competing interest exists.

                © The author(s)

                This is an open access article distributed under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.

                : 19 January 2021
                : 13 May 2021
                Research Paper

                Molecular medicine
                lncrna-h19 regulation,mirna sponge,bone formation,angiogenesis,extracellular vesicles


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