{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,3]],"date-time":"2026-02-03T21:00:13Z","timestamp":1770152413278,"version":"3.49.0"},"reference-count":26,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2025,4,29]],"date-time":"2025-04-29T00:00:00Z","timestamp":1745884800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Natural Science Foundation of China","award":["82301019"],"award-info":[{"award-number":["82301019"]}]},{"name":"National Natural Science Foundation of China","award":["82270951"],"award-info":[{"award-number":["82270951"]}]},{"name":"National Natural Science Foundation of China","award":["YSP202201"],"award-info":[{"award-number":["YSP202201"]}]},{"name":"Young Scientist Program of Beijing Stomatological Hospital, Capital Medical University","award":["82301019"],"award-info":[{"award-number":["82301019"]}]},{"name":"Young Scientist Program of Beijing Stomatological Hospital, Capital Medical University","award":["82270951"],"award-info":[{"award-number":["82270951"]}]},{"name":"Young Scientist Program of Beijing Stomatological Hospital, Capital Medical University","award":["YSP202201"],"award-info":[{"award-number":["YSP202201"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medicina"],"abstract":"<jats:p>Background and Objectives: Aging-related bone loss still lacks interventions. As bone marrow-derived mesenchymal stem cells (BMSCs) undergo aging, R-loop-induced DNA replication stress impairs the osteogenic ability of BMSCs. High-mobility group A-2 (Hmga2) acts as a DNA-binding protein, and the understanding of its underlying mechanisms is crucial for developing effective preventive and therapeutic strategies. Materials and Methods: Aging mice were used as the experimental model, and mouse BMSCs were isolated from their femurs. Hmga2 was achieved through specific gene delivery methods. R-loop formation was detected using dot blotting, chromatin immunoprecipitation (ChIP), and DNA\u2013RNA immunoprecipitation (DRIP) assays. Osteogenic differentiation was evaluated. Results: R-loops were highly accumulated in aging BMSCs. Notably, the key regulator Hmga2 reversed the accumulation of R-loops in aging BMSCs. Hmga2 overexpression significantly decreased the senescence and improved the osteogenic differentiation of aging mBMSCs. Mechanistically, R-loop-forming sequence (RLFS) regions were confirmed in key osteogenesis-related genes, including runt-related transcription factor 2 (Runx2). Hmga2 bound to the RLFS region of Runx2 and promoted its expression by reducing the R-loop level. More, Hmga2 treatment delivered via the AAV system effectively decreased bone loss in aging mice and increased the serum bone turnover biomarkers and collagen remodeling. Conclusions: Our study demonstrates that Hmga2 acts as an activator of aging BMSCs, significantly promoting their osteogenic ability by eliminating the aging-induced DNA replication stress caused by R-loops. Our findings provide new insights into the mechanisms of aging-related bone loss, suggesting that Hmga2 may be a new strategy for alleviating the bone loss phenotype in aging individuals.<\/jats:p>","DOI":"10.3390\/medicina61050820","type":"journal-article","created":{"date-parts":[[2025,5,4]],"date-time":"2025-05-04T20:42:37Z","timestamp":1746391357000},"page":"820","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Investigating the Associations Between Hmga2 Overexpression, R-Loop Reduction, and Bone Loss in Aging Mice"],"prefix":"10.3390","volume":"61","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7935-6170","authenticated-orcid":false,"given":"Yangyang","family":"Cao","sequence":"first","affiliation":[{"name":"Laboratory of Molecular Signaling and Stem Cells Therapy, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, No. 4 Tiantanxili, Dongcheng District, Beijing 100050, China"},{"name":"Department of General Dentistry and Integrated Emergency Dental Care, Beijing Stomatological Hospital, Capital Medical University, Beijing 100050, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yantong","family":"Wang","sequence":"additional","affiliation":[{"name":"Laboratory of Molecular Signaling and Stem Cells Therapy, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, No. 4 Tiantanxili, Dongcheng District, Beijing 100050, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dengsheng","family":"Xia","sequence":"additional","affiliation":[{"name":"Laboratory of Molecular Signaling and Stem Cells Therapy, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, No. 4 Tiantanxili, Dongcheng District, Beijing 100050, China"},{"name":"Department of General Dentistry and Integrated Emergency Dental Care, Beijing Stomatological Hospital, Capital Medical University, Beijing 100050, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,4,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"243","DOI":"10.1016\/j.cell.2022.11.001","article-title":"Hallmarks of aging: An expanding universe","volume":"186","author":"Blasco","year":"2023","journal-title":"Cell"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"nwae076","DOI":"10.1093\/nsr\/nwae076","article-title":"Biomaterial design for regenerating aged bone: Materiobiological advances and paradigmatic shifts","volume":"11","author":"Dai","year":"2024","journal-title":"Natl. Sci. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"e48947","DOI":"10.2196\/48947","article-title":"Sex- and Age-Specific Prevalence of Osteopenia and Osteoporosis: Sampling Survey","volume":"10","author":"Fan","year":"2024","journal-title":"JMIR Public Health Surveill."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1016\/j.bone.2019.03.041","article-title":"Aging and lineage allocation changes of bone marrow skeletal (stromal) stem cells","volume":"123","author":"Nehlin","year":"2019","journal-title":"Bone"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"266","DOI":"10.1016\/j.tem.2022.01.007","article-title":"Targeting aging mechanisms: Pharmacological perspectives","volume":"33","author":"Moskalev","year":"2022","journal-title":"Trends Endocrinol. Metab."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1186\/s13287-022-02852-w","article-title":"Epigenetic therapy targeting bone marrow mesenchymal stem cells for age-related bone diseases","volume":"13","author":"Zhao","year":"2022","journal-title":"Stem Cell Res. Ther."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"610","DOI":"10.1038\/s41586-023-06515-5","article-title":"R-loop-dependent promoter-proximal termination ensures genome stability","volume":"621","author":"Xu","year":"2023","journal-title":"Nature"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"8535","DOI":"10.18632\/aging.205070","article-title":"R-loops in neuronal aging","volume":"15","author":"Hall","year":"2023","journal-title":"Aging"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1038\/s41467-021-27722-6","article-title":"Proximity labeling identifies a repertoire of site-specific R-loop modulators","volume":"13","author":"Yan","year":"2022","journal-title":"Nat. Commun."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Su, L., Deng, Z., and Leng, F. (2020). The Mammalian High Mobility Group Protein AT-Hook 2 (HMGA2): Biochemical and Biophysical Properties, and Its Association with Adipogenesis. Int. J. Mol. Sci., 21.","DOI":"10.3390\/ijms21103710"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2128","DOI":"10.1002\/jcb.25519","article-title":"Fibroblast Growth Factor 2 Regulates High Mobility Group A2 Expression in Human Bone Marrow-Derived Mesenchymal Stem Cells","volume":"117","author":"Kalomoiris","year":"2016","journal-title":"J. Cell. Biochem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"588","DOI":"10.1002\/term.3023","article-title":"The protective effects of HMGA2 in the senescence process of bone marrow-derived mesenchymal stromal cells","volume":"14","author":"Yang","year":"2020","journal-title":"J. Tissue Eng. Regen. Med."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1245","DOI":"10.1038\/ng2121","article-title":"A common variant of HMGA2 is associated with adult and childhood height in the general population","volume":"39","author":"Weedon","year":"2007","journal-title":"Nat. Genet."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1016\/j.bbrc.2021.12.093","article-title":"High mobility group AT-hook 2 regulates osteoblast differentiation and facial bone development","volume":"590","author":"Negishi","year":"2022","journal-title":"Biochem. Biophys. Res. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.diff.2013.02.001","article-title":"Transdifferentiation of mesenchymal stem cells-derived adipogenic-differentiated cells into osteogenic- or chondrogenic-differentiated cells proceeds via dedifferentiation and have a correlation with cell cycle arresting and driving genes","volume":"85","author":"Ullah","year":"2013","journal-title":"Differentiation"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"4689","DOI":"10.12659\/MSM.904404","article-title":"MicroRNA-495 Inhibits New Bone Regeneration via Targeting High Mobility Group AT-Hook 2 (HMGA2)","volume":"23","author":"Tian","year":"2017","journal-title":"Med. Sci. Monit."},{"key":"ref_17","first-page":"2660","article-title":"MicroRNA-98-5p prevents bone regeneration by targeting high mobility group AT-Hook 2","volume":"18","author":"Zheng","year":"2019","journal-title":"Exp. Ther. Med."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"8450","DOI":"10.1002\/jcb.27069","article-title":"Epiregulin promotes the migration and chemotaxis ability of adipose-derived mesenchymal stem cells via mitogen-activated protein kinase signaling pathways","volume":"119","author":"Cao","year":"2018","journal-title":"J. Cell. Biochem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1007\/s00018-010-0457-9","article-title":"Histone deacetylase regulates high mobility group A2-targeting microRNAs in human cord blood-derived multipotent stem cell aging","volume":"68","author":"Lee","year":"2011","journal-title":"Cell. Mol. Life Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"588","DOI":"10.5713\/ajas.2012.12488","article-title":"Effects of serial passage on the characteristics and chondrogenic differentiation of canine umbilical cord matrix derived mesenchymal stem cells","volume":"26","author":"Lee","year":"2013","journal-title":"Asian-Australas. J. Anim. Sci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.scr.2012.11.002","article-title":"HMGA2 regulates the in vitro aging and proliferation of human umbilical cord blood-derived stromal cells through the mTOR\/p70S6K signaling pathway","volume":"10","author":"Yu","year":"2013","journal-title":"Stem Cell Res."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Kim, A., and Wang, G.G. (2021). R-loop and its functions at the regulatory interfaces between transcription and (epi)genome. Biochim. Biophys. Acta Gene Regul. Mech., 1864.","DOI":"10.1016\/j.bbagrm.2021.194750"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1178","DOI":"10.1038\/s12276-020-0471-4","article-title":"RUNX2-modifying enzymes: Therapeutic targets for bone diseases","volume":"52","author":"Kim","year":"2020","journal-title":"Exp. Mol. Med."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"269","DOI":"10.22203\/eCM.v028a19","article-title":"Role and regulation of RUNX2 in osteogenesis","volume":"28","author":"Bruderer","year":"2014","journal-title":"Eur. Cells Mater."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3392","DOI":"10.1038\/s41467-020-17176-7","article-title":"R-loop induced G-quadruplex in non-template promotes transcription by successive R-loop formation","volume":"11","author":"Lee","year":"2020","journal-title":"Nat. Commun."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"11942","DOI":"10.1093\/nar\/gkaa944","article-title":"G-quadruplex\u2013R-loop interactions and the mechanism of anticancer G-quadruplex binders","volume":"48","author":"Miglietta","year":"2020","journal-title":"Nucleic Acids Res."}],"container-title":["Medicina"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1648-9144\/61\/5\/820\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:24:01Z","timestamp":1760030641000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1648-9144\/61\/5\/820"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,4,29]]},"references-count":26,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2025,5]]}},"alternative-id":["medicina61050820"],"URL":"https:\/\/doi.org\/10.3390\/medicina61050820","relation":{},"ISSN":["1648-9144"],"issn-type":[{"value":"1648-9144","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,4,29]]}}}