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Root SH, Wee NKY, Novak S, Rosen CJ, Baron R, Matthews BG, Kalajzic I. Perivascular osteoprogenitors are associated with transcortical channels of long bones. Stem Cells 2020; 38:769-781. [PMID: 32053258 DOI: 10.1002/stem.3159] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 01/23/2020] [Indexed: 12/14/2022]
Abstract
Bone remodeling and regeneration are dependent on resident stem/progenitor cells with the ability to replenish mature osteoblasts and repair the skeleton. Using lineage tracing approaches, we identified a population of Dmp1+ cells that reside within cortical bone and are distinct from osteocytes. Our aims were to characterize this stromal population of transcortical perivascular cells (TPCs) in their resident niche and evaluate their osteogenic potential. To distinguish this population from osteoblasts/osteocytes, we crossed mice containing inducible DMP1CreERT2/Ai9 Tomato reporter (iDMP/T) with Col2.3GFP reporter (ColGFP), a marker of osteoblasts and osteocytes. We observed iDMP/T+;ColGFP- TPCs within cortical bone following tamoxifen injection. These cells were perivascular and located within transcortical channels. Ex vivo bone outgrowth cultures showed TPCs migrated out of the channels onto the plate and expressed stem cell markers such as Sca1, platelet derived growth factor receptor beta (PDGFRβ), and leptin receptor. In a cortical bone transplantation model, TPCs migrate from their vascular niche within cortical bone and contribute to new osteoblast formation and bone tube closure. Treatment with intermittent parathyroid hormone increased TPC number and differentiation. TPCs were unable to differentiate into adipocytes in the presence of rosiglitazone in vitro or in vivo. Altogether, we have identified and characterized a novel stromal lineage-restricted osteoprogenitor that is associated with transcortical vessels of long bones. Functionally, we have demonstrated that this population can migrate out of cortical bone channels, expand, and differentiate into osteoblasts, therefore serving as a source of progenitors contributing to new bone formation.
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Affiliation(s)
- Sierra H Root
- Department of Reconstructive Sciences, UConn Health, Farmington, Connecticut, USA
| | - Natalie K Y Wee
- Department of Reconstructive Sciences, UConn Health, Farmington, Connecticut, USA
| | - Sanja Novak
- Department of Reconstructive Sciences, UConn Health, Farmington, Connecticut, USA
| | - Clifford J Rosen
- Department of Medicine, Tufts University School of Medicine, Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Roland Baron
- Department of Oral Medicine, Infection and Immunity, Division of Bone and Mineral Research, Harvard School of Dental Medicine, Boston, Massachusetts, USA.,Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA
| | - Brya G Matthews
- Department of Reconstructive Sciences, UConn Health, Farmington, Connecticut, USA.,Department of Molecular Medicine and Pathology, University of Auckland, Auckland, New Zealand
| | - Ivo Kalajzic
- Department of Reconstructive Sciences, UConn Health, Farmington, Connecticut, USA
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Creecy A, Damrath JG, Wallace JM. Control of Bone Matrix Properties by Osteocytes. Front Endocrinol (Lausanne) 2020; 11:578477. [PMID: 33537002 PMCID: PMC7848033 DOI: 10.3389/fendo.2020.578477] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 12/01/2020] [Indexed: 12/13/2022] Open
Abstract
Osteocytes make up 90-95% of the cellular content of bone and form a rich dendritic network with a vastly greater surface area than either osteoblasts or osteoclasts. Osteocytes are well positioned to play a role in bone homeostasis by interacting directly with the matrix; however, the ability for these cells to modify bone matrix remains incompletely understood. With techniques for examining the nano- and microstructure of bone matrix components including hydroxyapatite and type I collagen becoming more widespread, there is great potential to uncover novel roles for the osteocyte in maintaining bone quality. In this review, we begin with an overview of osteocyte biology and the lacunar-canalicular system. Next, we describe recent findings from in vitro models of osteocytes, focusing on the transitions in cellular phenotype as they mature. Finally, we describe historical and current research on matrix alteration by osteocytes in vivo, focusing on the exciting potential for osteocytes to directly form, degrade, and modify the mineral and collagen in their surrounding matrix.
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Affiliation(s)
- Amy Creecy
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States
| | - John G. Damrath
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States
| | - Joseph M. Wallace
- Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, United States
- *Correspondence: Joseph M. Wallace,
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