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Sorsby M, Almardini S, Alayyat A, Hughes A, Venkat S, Rahman M, Baker J, Rana R, Rosen V, Liu ES. The role of GDF5 in regulating enthesopathy development in the Hyp mouse model of XLH. J Bone Miner Res 2024; 39:1162-1173. [PMID: 38836497 PMCID: PMC11337578 DOI: 10.1093/jbmr/zjae086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 04/25/2024] [Accepted: 06/04/2024] [Indexed: 06/06/2024]
Abstract
X-linked hypophosphatemia (XLH) is caused by mutations in PHEX, leading to rickets and osteomalacia. Adults affected with XLH develop a mineralization of the bone-tendon attachment site (enthesis), called enthesopathy, which causes significant pain and impaired movement. Entheses in mice with XLH (Hyp) have enhanced bone morphogenetic protein (BMP) and Indian hedgehog (IHH) signaling. Treatment of Hyp mice with the BMP signaling blocker palovarotene attenuated BMP/IHH signaling in Hyp entheses, thus indicating that BMP signaling plays a pathogenic role in enthesopathy development and that IHH signaling is activated by BMP signaling in entheses. It was previously shown that mRNA expression of growth/differentiation factor 5 (Gdf5) is enhanced in Hyp entheses at P14. Thus, to determine a role for GDF5 in enthesopathy development, Gdf5 was deleted globally in Hyp mice and conditionally in Scx + cells of Hyp mice. In both murine models, BMP/IHH signaling was similarly decreased in Hyp entheses, leading to decreased enthesopathy. BMP/IHH signaling remained unaffected in WT entheses with decreased Gdf5 expression. Moreover, deletion of Gdf5 in Hyp entheses starting at P30, after enthesopathy has developed, partially reversed enthesopathy. Taken together, these results demonstrate that while GDF5 is not essential for modulating BMP/IHH signaling in WT entheses, inappropriate GDF5 activity in Scx + cells contributes to XLH enthesopathy development. As such, inhibition of GDF5 signaling may be beneficial for the treatment of XLH enthesopathy.
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Affiliation(s)
- Melissa Sorsby
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Shaza Almardini
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Ahmad Alayyat
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Ashleigh Hughes
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Shreya Venkat
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Mansoor Rahman
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Jiana Baker
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Rakshya Rana
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
| | - Vicki Rosen
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115, United States
| | - Eva S Liu
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, MA 02115, United States
- Harvard Medical School, Boston, MA 02115, United States
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Chen Y, Hao M, Bousso I, Thomopoulos S, Xia Y. Reliable Fabrication of Mineral-Graded Scaffolds by Spin-Coating and Laser Machining for Use in Tendon-to-Bone Insertion Repair. Adv Healthc Mater 2024:e2402531. [PMID: 39104021 DOI: 10.1002/adhm.202402531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2024] [Revised: 07/28/2024] [Indexed: 08/07/2024]
Abstract
A reliable method for fabricating biomimetic scaffolds with a controllable mineral gradient to facilitate the surgical repair of tendon-to-bone injuries and the regeneration of the enthesis is reported. The gradient in mineral content is created by sequentially spin-coating with hydroxyapatite/poly(ε-caprolactone) suspensions containing hydroxyapatite nanoparticles in decreasing concentrations. To produce pores and facilitate cell infiltration, the spin-coated film is released and patterned with an array of funnel-shaped microchannels by laser machining. The unique design provided both mechanical (i.e., substrate stiffness) and biochemical (e.g., hydroxyapatite content) cues to spatially control the graded differentiation of mesenchymal stem cells. Immunocytochemical analysis of human mesenchymal stem cell-seeded scaffolds after 14 days of culture demonstrated the formation of a spatial phenotypic cell gradient from osteoblasts to mineralized chondrocytes based on the level of mineralization in the scaffold. By successfully recreating compositional and cellular features of the native tendon enthesis, the biomimetic scaffolds offer a promising avenue for improved tendon-to-bone repair.
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Affiliation(s)
- Yidan Chen
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Min Hao
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, 30332, USA
| | - Ismael Bousso
- Department of Orthopedic Surgery, Department of Biomedical Engineering, Columbia University, New York, NY, 10032, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Department of Biomedical Engineering, Columbia University, New York, NY, 10032, USA
| | - Younan Xia
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, 30332, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
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Durtschi MS, Kim S, Li J, Kim C, Chu C, Cheung E, Safran M, Abrams G, Yang YP. Optimizing Tissue Engineering for Clinical Relevance in Rotator Cuff Repair. TISSUE ENGINEERING. PART B, REVIEWS 2024. [PMID: 38411502 DOI: 10.1089/ten.teb.2023.0320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Rotator cuff tear (RCT) is the most common cause of disability in the upper extremity. It results in 4.5 million physician visits in the United States every year and is the most common etiology of shoulder conditions evaluated by orthopedic surgeons. Over 460,000 RCT repair surgeries are performed in the United States annually. Rotator cuff (RC) retear and failure to heal remain significant postoperative complications. Literature suggests that the retear rates can range from 29.5% to as high as 94%. Weakened and irregular enthesis regeneration is a crucial factor in postsurgical failure. Although commercially available RC repair grafts have been introduced to augment RC enthesis repair, they have been associated with mixed clinical outcomes. These grafts lack appropriate biological cues such as stem cells and signaling molecules at the bone-tendon interface. In addition, they do little to prevent fibrovascular scar tissue formation, which causes the RC to be susceptible to retear. Advances in tissue engineering have demonstrated that mesenchymal stem cells (MSCs) and growth factors (GFs) enhance RC enthesis regeneration in animal models. These models show that delivering MSCs and GFs to the site of RCT enhances native enthesis repair and leads to greater mechanical strength. In addition, these models demonstrate that MSCs and GFs may be delivered through a variety of methods including direct injection, saturation of repair materials, and loaded microspheres. Grafts that incorporate MSCs and GFs enhance anti-inflammation, osteogenesis, angiogenesis, and chondrogenesis in the RC repair process. It is crucial that the techniques that have shown success in animal models are incorporated into the clinical setting. A gap currently exists between the promising biological factors that have been investigated in animal models and the RC repair grafts that can be used in the clinical setting. Future RC repair grafts must allow for stable implantation and fixation, be compatible with current arthroscopic techniques, and have the capability to deliver MSCs and/or GFs.
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Affiliation(s)
| | - Sungwoo Kim
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Jiannan Li
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Carolyn Kim
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Constance Chu
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Emilie Cheung
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Marc Safran
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Geoff Abrams
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
| | - Yunzhi Peter Yang
- Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
- Department of Material Science and Engineering, and Stanford University, Stanford, California, USA
- Department of Bioengineering, Stanford University, Stanford, California, USA
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Song L, Golman M, Abraham AC, Zelzer E, Thomopoulos S. A role for TGFβ signaling in Gli1+ tendon and enthesis cells. FASEB J 2024; 38:e23568. [PMID: 38522021 PMCID: PMC10962263 DOI: 10.1096/fj.202301452r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 02/16/2024] [Accepted: 03/07/2024] [Indexed: 03/25/2024]
Abstract
The development of musculoskeletal tissues such as tendon, enthesis, and bone relies on proliferation and differentiation of mesenchymal progenitor cells. Gli1+ cells have been described as putative stem cells in several tissues and are presumed to play critical roles in tissue formation and maintenance. For example, the enthesis, a fibrocartilage tissue that connects tendon to bone, is mineralized postnatally by a pool of Gli1+ progenitor cells. These cells are regulated by hedgehog signaling, but it is unclear if TGFβ signaling, necessary for tenogenesis, also plays a role in their behavior. To examine the role of TGFβ signaling in Gli1+ cell function, the receptor for TGFβ, TbR2, was deleted in Gli1-lineage cells in mice at P5. Decreased TGFβ signaling in these cells led to defects in tendon enthesis formation by P56, including defective bone morphometry underlying the enthesis and decreased mechanical properties. Immunohistochemical staining of these Gli1+ cells showed that loss of TGFβ signaling reduced proliferation and increased apoptosis. In vitro experiments using Gli1+ cells isolated from mouse tail tendons demonstrated that TGFβ controls cell proliferation and differentiation through canonical and non-canonical pathways and that TGFβ directly controls the tendon transcription factor scleraxis by binding to its distant enhancer. These results have implications in the development of treatments for tendon and enthesis pathologies.
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Affiliation(s)
- Lee Song
- Department of Orthopedic Surgery, Columbia University, New York, NY10032, USA
| | - Mikhail Golman
- Department of Orthopedic Surgery, Columbia University, New York, NY10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY10027, USA
| | - Adam C. Abraham
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Elazar Zelzer
- Department of Molecular Genetics, Weizmann Institute of Science, Israel
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY10032, USA
- Department of Biomedical Engineering, Columbia University, New York, NY10027, USA
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吴 雨, 白 浪, 刘 妍, 韩 潜, 刘 俏, 艾 义, 徐 美, 温 暖, 单 智, 尹 战. [Research progress of magnesium and magnesium alloy implants in sports medicine]. ZHONGGUO XIU FU CHONG JIAN WAI KE ZA ZHI = ZHONGGUO XIUFU CHONGJIAN WAIKE ZAZHI = CHINESE JOURNAL OF REPARATIVE AND RECONSTRUCTIVE SURGERY 2024; 38:380-386. [PMID: 38500435 PMCID: PMC10982037 DOI: 10.7507/1002-1892.202401072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 03/02/2024] [Accepted: 03/04/2024] [Indexed: 03/20/2024]
Abstract
Objective To review the research progress of magnesium and magnesium alloy implants in the repair and reconstruction of sports injury. Methods Relevant literature of magnesium and magnesium alloys for sports injury repair and reconstruction was extensively reviewed. The characteristics of magnesium and its alloys and their applications in the repair and reconstruction of sports injuries across various anatomical sites were thoroughly discussed and summarized. Results Magnesium and magnesium alloys have advantages in mechanical properties, biosafety, and promoting tendon-bone interface healing. Many preclinical studies on magnesium and magnesium alloy implants for repairing and reconstructing sports injuries have yielded promising results. However, successful clinical translation still requires addressing issues related to mechanical strength and degradation behavior, where alloying and surface treatments offer feasible solutions. Conclusion The clinical translation of magnesium and magnesium alloy implants for repairing and reconstructing sports injuries holds promise. Subsequent efforts should focus on optimizing the mechanical strength and degradation behavior of magnesium and magnesium alloy implants. Conducting larger-scale biocompatibility testing and developing novel magnesium-containing implants represent new directions for future research.
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Affiliation(s)
- 雨宽 吴
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 浪 白
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 妍兰 刘
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 潜 韩
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 俏男 刘
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 义翔 艾
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 美光 徐
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 暖洋 温
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
| | - 智伟 单
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
- 西安交通大学材料科学与工程学院(西安 710049)Department of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an Shaanxi, 710049, P. R. China
| | - 战海 尹
- 西安交通大学第一附属医院骨科(西安 710061)Department of Orthopedics, First Affiliated Hospital of Xi’an Jiaotong University, Xi’an Shaanxi, 710061, P. R. China
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Mao D, Wang K, Jiang H, Mi J, Pan X, Zhao G, Rui Y. Suppression of Overactive Insulin-Like Growth Factor 1 Attenuates Trauma-Induced Heterotopic Ossification in Mice. THE AMERICAN JOURNAL OF PATHOLOGY 2024; 194:430-446. [PMID: 38101566 DOI: 10.1016/j.ajpath.2023.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/31/2023] [Accepted: 11/28/2023] [Indexed: 12/17/2023]
Abstract
Heterotopic ossification (HO) is the ectopic bone formation in soft tissues. Aside from hereditary HO, traumatic HO is common after orthopedic surgery, combat-related injuries, severe burns, or neurologic injuries. Recently, mammalian target of rapamycin (mTOR) was demonstrated to be involved in the chondrogenic and osteogenic processes of HO formation. However, its upstream signaling mechanism remains unknown. The current study used an Achilles tendon puncture-induced HO model to show that overactive insulin-like growth factor 1 (IGF-1) was involved in the progression of HO in mice. Micro-computed tomography imaging showed that IGF-1 not only accelerated the rate of osteogenesis and increased ectopic bone volume but also induced spontaneous ectopic bone formation in undamaged Achilles tendons. Blocking IGF-1 activity with IGF-1 antibody or IGF-1 receptor inhibitor picropodophyllin significantly inhibited HO formation. Mechanistically, IGF-1/IGF-1 receptor activates phosphatidylinositol 3-kinase (PI3K)/Akt signaling to promote the phosphorylation of mTOR, resulting in the chondrogenic and osteogenic differentiation of tendon-derived stem cells into chondrocytes and osteoblasts in vitro and in vivo. Inhibitors of PI3K (LY294002) and mTOR (rapamycin) both suppressed the IGF-1-stimulated mTOR signal and mitigated the formation of ectopic bones significantly. In conclusion, these results indicate that IGF-1 mediated the progression of traumatic HO through PI3K/Akt/mTOR signaling, and suppressing IGF-1 signaling cascades attenuated HO formation, providing a promising therapeutic strategy targeting HO.
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Affiliation(s)
- Dong Mao
- Orthopaedic Institute, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China; Wuxi School of Medicine, Jiangnan University, Wuxi, China
| | - Kai Wang
- Department of Orthopedics, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China; Suzhou Medical College of Soochow University, Soochow University, Suzhou, China
| | - Hong Jiang
- Suzhou Medical College of Soochow University, Soochow University, Suzhou, China; Department of Hand Surgery, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China
| | - Jingyi Mi
- Department of Sports Medicine, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China
| | - Xiaoyun Pan
- Orthopaedic Institute, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China
| | - Gang Zhao
- Department of Hand Surgery, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China.
| | - Yongjun Rui
- Wuxi School of Medicine, Jiangnan University, Wuxi, China; Department of Orthopedics, Wuxi Ninth People's Hospital Affiliated to Soochow University, Wuxi, China.
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Ye P, Gu R, Zhu H, Chen J, Han F, Nie X. SOX family transcription factors as therapeutic targets in wound healing: A comprehensive review. Int J Biol Macromol 2023; 253:127243. [PMID: 37806414 DOI: 10.1016/j.ijbiomac.2023.127243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/02/2023] [Accepted: 10/02/2023] [Indexed: 10/10/2023]
Abstract
The SOX family plays a vital role in determining the fate of cells and has garnered attention in the fields of cancer research and regenerative medicine. It also shows promise in the study of wound healing, as it actively participates in the healing processes of various tissues such as skin, fractures, tendons, and the cornea. However, our understanding of the mechanisms behind the SOX family's involvement in wound healing is limited compared to its role in cancer. Gaining insight into its role, distribution, interaction with other factors, and modifications in traumatized tissues could provide valuable new knowledge about wound healing. Based on current research, SOX2, SOX7, and SOX9 are the most promising members of the SOX family for future interventions in wound healing. SOX2 and SOX9 promote the renewal of cells, while SOX7 enhances the microvascular environment. The SOX family holds significant potential for advancing wound healing research. This article provides a comprehensive review of the latest research advancements and therapeutic tools related to the SOX family in wound healing, as well as the potential benefits and challenges of targeting the SOX family for wound treatment.
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Affiliation(s)
- Penghui Ye
- Key Lab of the Basic Pharmacology of the Ministry of Education & Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563006, China; College of Pharmacy, Zunyi Medical University, Zunyi 563006, China
| | - Rifang Gu
- Key Lab of the Basic Pharmacology of the Ministry of Education & Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563006, China; School Medical Office, Zunyi Medical University, Zunyi 563006, China
| | - Huan Zhu
- Key Lab of the Basic Pharmacology of the Ministry of Education & Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563006, China; College of Pharmacy, Zunyi Medical University, Zunyi 563006, China
| | - Jitao Chen
- Key Lab of the Basic Pharmacology of the Ministry of Education & Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563006, China; College of Pharmacy, Zunyi Medical University, Zunyi 563006, China
| | - Felicity Han
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Xuqiang Nie
- Key Lab of the Basic Pharmacology of the Ministry of Education & Joint International Research Laboratory of Ethnomedicine of Ministry of Education, Zunyi Medical University, Zunyi 563006, China; College of Pharmacy, Zunyi Medical University, Zunyi 563006, China; Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia.
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Luzzi AJ, Ferrer X, Fang F, Golman M, Song L, Marshall BP, Lee AJ, Kim JJ, Hung CT, Thomopoulos S. Hedgehog Activation for Enhanced Rotator Cuff Tendon-to-Bone Healing. Am J Sports Med 2023; 51:3825-3834. [PMID: 37897335 PMCID: PMC10821775 DOI: 10.1177/03635465231203210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/30/2023]
Abstract
BACKGROUND Rotator cuff repair is a common orthopaedic procedure, yet the rate of failure to heal after surgery is high. Repair site rupture is due to poor tendon-to-bone healing and lack of regeneration of the native fibrocartilaginous enthesis. During development, the enthesis is formed and mineralized by a pool of progenitors activated by hedgehog signaling. Furthermore, hedgehog signaling drives regenerative enthesis healing in young animals, in contrast to older animals, in which enthesis injuries heal via fibrovascular scar and without participation of hedgehog signaling. HYPOTHESIS Hedgehog activation improves tendon-to-bone healing in an animal model of rotator cuff repair. STUDY DESIGN Controlled laboratory study. METHODS A total of 78 adult Sprague-Dawley rats were used. Supraspinatus tendon injury and repair were completed bilaterally, with microsphere-encapsulated hedgehog agonist administered to right shoulders and control microspheres administered to left shoulders. Animals were sacrificed after 3, 14, 28, or 56 days. Gene expression and histological, biomechanical, and bone morphometric analyses were conducted. RESULTS At 3 days, hedgehog signaling pathway genes Gli1 (1.70; P = .029) and Smo (2.06; P = .0173), as well as Runx2 (1.69; P = .0386), a transcription factor of osteogenesis, were upregulated in treated relative to control repairs. At 14 days, transcription factors of tenogenesis, Scx (4.00; P = .041), and chondrogenesis, Sox9 (2.95; P = .010), and mineralized fibrocartilage genes Col2 (3.18; P = .031) and Colx (1.85; P = .006), were upregulated in treated relative to control repairs. Treatment promoted fibrocartilage formation at the healing interface by 28 days, with improvements in tendon-bone maturity, organization, and continuity. Treatment led to improved biomechanical properties. The material property strength (2.43 vs 1.89 N/m2; P = .046) and the structural property work to failure (29.01 vs 18.09 mJ; P = .030) were increased in treated relative to control repairs at 28 days and 56 days, respectively. Treatment had a marginal effect on bone morphometry underlying the repair. Trabecular thickness (0.08 vs 0.07 mm; P = .035) was increased at 28 days. CONCLUSION Hedgehog agonist treatment activated hedgehog signaling at the tendon-to-bone repair site and prompted increased mineralized fibrocartilage production. This extracellular matrix production and mineralization resulted in improved biomechanical properties, demonstrating the therapeutic potential of hedgehog agonism for improving tendon-to-bone healing after rotator cuff repair. CLINICAL RELEVANCE This study demonstrates the therapeutic potential of hedgehog agonist treatment for improving tendon-to-bone healing after rotator cuff injury and repair.
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Affiliation(s)
- Andrew J. Luzzi
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
| | - Xavier Ferrer
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
| | - Fei Fang
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
| | - Mikhail Golman
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
| | - Lee Song
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
| | - Brittany P. Marshall
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
| | - Andy J. Lee
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
| | - Jieon J. Kim
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
| | - Clark T. Hung
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
| | - Stavros Thomopoulos
- Department of Orthopaedic Surgery, Columbia University, New York, New York, USA
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
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蔡 武, 李 箭, 李 棋. [Research progress on bioactive strategies for promoting tendon graft healing after anterior cruciate ligament reconstruction]. ZHONGGUO XIU FU CHONG JIAN WAI KE ZA ZHI = ZHONGGUO XIUFU CHONGJIAN WAIKE ZAZHI = CHINESE JOURNAL OF REPARATIVE AND RECONSTRUCTIVE SURGERY 2023; 37:1292-1299. [PMID: 37848327 PMCID: PMC10581880 DOI: 10.7507/1002-1892.202306088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 09/14/2023] [Indexed: 10/19/2023]
Abstract
Objective To review the bioactive strategies that enhance tendon graft healing after anterior cruciate ligament reconstruction (ACLR), and to provide insights for improving the therapeutic outcomes of ACLR. Methods The domestic and foreign literature related to the bioactive strategies for promoting the healing of tendon grafts after ACLR was extensively reviewed and summarized. Results At present, there are several kinds of bioactive materials related to tendon graft healing after ACLR: growth factors, cells, biodegradable implants/tissue derivatives. By constructing a complex interface simulating the matrix, environment, and regulatory factors required for the growth of native anterior cruciate ligament (ACL), the growth of transplanted tendons is regulated at different levels, thus promoting the healing of tendon grafts. Although the effectiveness of ACLR has been significantly improved in most studies, most of them are still limited to the early stage of animal experiments, and there is still a long way to go from the real clinical promotion. In addition, limited by the current preparation technology, the bionics of the interface still stays at the micron and millimeter level, and tends to be morphological bionics, and the research on the signal mechanism pathway is still insufficient. Conclusion With the further study of ACL anatomy, development, and the improvement of preparation technology, the research of bioactive strategies to promote the healing of tendon grafts after ACLR is expected to be further promoted.
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Affiliation(s)
- 武峰 蔡
- 四川大学华西医院骨科 骨科研究所(成都 610041)Department of Orthopedics, Orthopedic Research Institute, West China Hospital, Sichuan Chengdu, 610041, P. R. China
| | - 箭 李
- 四川大学华西医院骨科 骨科研究所(成都 610041)Department of Orthopedics, Orthopedic Research Institute, West China Hospital, Sichuan Chengdu, 610041, P. R. China
| | - 棋 李
- 四川大学华西医院骨科 骨科研究所(成都 610041)Department of Orthopedics, Orthopedic Research Institute, West China Hospital, Sichuan Chengdu, 610041, P. R. China
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von Kroge S, Büyükyilmaz Z, Alimy AR, Hubert J, Citak M, Amling M, Beil FT, Ohlmeier M, Rolvien T. Do Clinical Parameters Reflect Local Bone Metabolism in Heterotopic Ossification After Septic or Aseptic THA? Clin Orthop Relat Res 2023; 481:2029-2041. [PMID: 37462509 PMCID: PMC10499090 DOI: 10.1097/corr.0000000000002758] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 06/06/2023] [Indexed: 09/16/2023]
Abstract
BACKGROUND Heterotopic ossification (HO) is a common complication after THA. Although current research primarily focuses on treatment and prevention, little is known about the local bone metabolism of HO and clinical contributing factors. QUESTIONS/PURPOSES We aimed to assess bone remodeling processes in HO using histomorphometry, focusing on the effects of inflammation and prior NSAID treatment. Specifically, we asked: (1) Are HO specimens taken from patients with periprosthetic joint infection (PJI) more likely to exhibit active bone modeling and remodeling than specimens taken at the time of revision from patients without infection? (2) Do clinical or inflammatory serum and synovial parameters reflect the microstructure of and remodeling in both HO entities? (3) Is NSAID treatment before revision surgery associated with altered local bone mineralization or remodeling properties? METHODS Between June 2021 and May 2022, we screened 395 patients undergoing revision THA at two tertiary centers in Germany. Of those, we considered all patients with radiographic HO as potentially eligible. Based on that, 21% (83 of 395) were eligible; a further 43 were excluded because of an inability to remove the implant intraoperatively (16 patients), insufficient material (11), comorbidities with a major effect on bone metabolism (10), or bone-specific drugs (six), leaving 10% (40) for analysis in this retrospective, comparative study. HO specimens were collected during aseptic (25 patients: 18 male, seven female, mean age 70 ± 11 years, mean BMI 29 ± 4 kg/m 2 ) and septic (15 patients: 11 male, four female, mean age 69 ± 9 years, mean BMI 32 ± 9 kg/m 2 ) revision THA at a mean of 6 ± 7 years after primary implantation and a mean age of 70 ± 9 years at revision. Septic origin (PJI) was diagnosed based on the 2018 International Consensus Meeting criteria, through a preoperative assessment of serum and synovial parameters. To specify the local bone microstructure, ossification, and cellular bone turnover, we analyzed HO specimens using micro-CT and histomorphometry on undecalcified sections. Data were compared with those of controls, taken from femoral neck trabecular bone (10 patients: five female, five male, mean age 75 ± 6 years, mean BMI 28 ± 4 kg/m 2 ) and osteophytes (10 patients: five female, five male, mean age 70 ± 10 years, mean BMI 29 ± 7 kg/m 2 ). The time between primary implantation and revision (time in situ), HO severity based on the Brooker classification, and serum and synovial markers were correlated with HO microstructure and parameters of cellular bone turnover. In a subgroup of specimens of patients with NSAID treatment before revision, osteoid and bone turnover indices were evaluated and compared a matched cohort of specimens from patients without prior NSAID treatment. RESULTS Patients with aseptic and septic HO presented with a higher bone volume (BV/TV; aseptic: 0.41 ± 0.15, mean difference 0.20 [95% CI 0.07 to 0.32]; septic: 0.43 ± 0.15, mean difference 0.22 [95% CI 0.08 to 0.36]; femoral neck: 0.21 ± 0.04; both p < 0.001), lower bone mineral density (aseptic: 809 ± 66 mg HA/cm 3 , mean difference -91 mg HA/cm 3 [95% CI -144 to -38]; septic: 789 ± 44 mg HA/cm 3 , mean difference -111 mg HA/cm 3 [95% CI -169 to -53]; femoral neck: 899 ± 20 mg HA/cm 3 ; both p < 0.001), and ongoing bone modeling with endochondral ossification and a higher proportion of woven, immature bone (aseptic: 25% ± 17%, mean difference 25% [95% CI 9% to 41%]; septic: 37% ± 23%, mean difference 36% [95% CI 19% to 54%]; femoral neck: 0.4% ± 0.5%; both p < 0.001) compared with femoral neck specimens. Moreover, bone surfaces were characterized by increased osteoblast and osteoclast indices in both aseptic and septic HO, although a higher density of osteocytes was detected exclusively in septic HO (aseptic: 158 ± 56 1/mm 2 versus septic: 272 ± 48 1/mm 2 , mean difference 114 1/mm 2 [95% CI 65 to 162]; p < 0.001). Compared with osteophytes, microstructure and turnover indices were largely similar in HO. The Brooker class was not associated with any local bone metabolism parameters. The time in situ was negatively associated with bone turnover in aseptic HO specimens (osteoblast surface per bone surface: r = -0.46; p = 0.01; osteoclast surface per bone surface: r = -0.56; p = 0.003). Serum or synovial inflammatory markers were not correlated with local bone turnover in septic HO. Specimens of patients with NSAID treatment before revision surgery had a higher osteoid thickness (10.1 ± 2.1 µm versus 5.5 ± 2.6 µm, mean difference -4.7 µm [95% CI -7.4 to -2.0]; p = 0.001), but there was no difference in other osteoid, structural, or cellular parameters. CONCLUSION Aseptic and septic HO share phenotypic characteristics in terms of the sustained increase in bone metabolism, although differences in osteocyte and adipocyte numbers suggest distinct homeostatic mechanisms. These results suggest persistent bone modeling or remodeling, with osteoblast and osteoclast indices showing a moderate decline with the time in situ in aseptic HO. Future studies should use longitudinal study designs to correlate our findings with clinical outcomes (such as HO growth or recurrence). In addition, the molecular mechanisms of bone cell involvement during HO formation and growth should be further investigated, which may allow specific therapeutic and preventive interventions. CLINICAL RELEVANCE To our knowledge, our study is the first to systematically investigate histomorphometric bone metabolism parameters in patients with HO after THA, providing a clinical reference for evaluating modeling and remodeling activity. Routine clinical, serum, and synovial markers are not useful for inferring local bone metabolism.
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Affiliation(s)
- Simon von Kroge
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Assil-Ramin Alimy
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jan Hubert
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Mustafa Citak
- Department of Joint Surgery, Helios ENDO-Klinik, Hamburg, Germany
| | - Michael Amling
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Frank Timo Beil
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Malte Ohlmeier
- Department of Joint Surgery, Helios ENDO-Klinik, Hamburg, Germany
- Department of Orthopaedic and Trauma Surgery, UKM Marienhospital, Steinfurt, Germany
| | - Tim Rolvien
- Department of Trauma and Orthopaedic Surgery, Division of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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Rana R, Baker JT, Sorsby M, Jagga S, Venkat S, Almardini S, Liu ES. Impaired 1,25-dihydroxyvitamin D3 action underlies enthesopathy development in the Hyp mouse model of X-linked hypophosphatemia. JCI Insight 2023; 8:e163259. [PMID: 37490334 PMCID: PMC10544216 DOI: 10.1172/jci.insight.163259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 07/20/2023] [Indexed: 07/27/2023] Open
Abstract
X-linked hypophosphatemia (XLH) is characterized by high serum fibroblast growth factor 23 (FGF23) levels, resulting in impaired 1,25-dihydroxyvitamin D3 (1,25D) production. Adults with XLH develop a painful mineralization of the tendon-bone attachment site (enthesis), called enthesopathy. Treatment of mice with XLH (Hyp) with 1,25D or an anti-FGF23 Ab, both of which increase 1,25D signaling, prevents enthesopathy. Therefore, we undertook studies to determine a role for impaired 1,25D action in enthesopathy development. Entheses from mice lacking vitamin D 1α-hydroxylase (Cyp27b1) (C-/-) had a similar enthesopathy to Hyp mice, whereas deletion of Fgf23 in Hyp mice prevented enthesopathy, and deletion of both Cyp27b1 and Fgf23 in mice resulted in enthesopathy, demonstrating that the impaired 1,25D action due to high FGF23 levels underlies XLH enthesopathy development. Like Hyp mice, enthesopathy in C-/- mice was observed by P14 and was prevented, but not reversed, with 1,25D therapy. Deletion of the vitamin D receptor in scleraxis-expressing cells resulted in enthesopathy, indicating that 1,25D acted directly on enthesis cells to regulate enthesopathy development. These results show that 1,25D signaling was necessary for normal postnatal enthesis maturation and played a role in XLH enthesopathy development. Optimizing 1,25D replacement in pediatric patients with XLH is necessary to prevent enthesopathy.
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Affiliation(s)
- Rakshya Rana
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Jiana T. Baker
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Melissa Sorsby
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Supriya Jagga
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Shreya Venkat
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Shaza Almardini
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Eva S. Liu
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
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Buss DJ, Rechav K, Reznikov N, McKee MD. Mineral tessellation in mouse enthesis fibrocartilage, Achilles tendon, and Hyp calcifying enthesopathy: A shared 3D mineralization pattern. Bone 2023:116818. [PMID: 37295663 DOI: 10.1016/j.bone.2023.116818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/17/2023] [Accepted: 06/01/2023] [Indexed: 06/12/2023]
Abstract
The hallmark of enthesis architecture is the 3D compositional and structural gradient encompassing four tissue zones - tendon/ligament, uncalcified fibrocartilage, calcified fibrocartilage and bone. This functional gradient accommodates the large stiffness differential between calcified bone and uncalcified tendon/ligament. Here we analyze in 3D the organization of the mouse Achilles enthesis and mineralizing Achilles tendon in comparison to lamellar bone. We use correlative, multiscale high-resolution volume imaging methods including μCT with submicrometer resolution and FIB-SEM tomography (both with deep learning-based image segmentation), and TEM and SEM imaging, to describe ultrastructural features of physiologic, age-related and aberrant mineral patterning. We applied these approaches to murine wildtype (WT) Achilles enthesis tissues to describe in normal calcifying fibrocartilage a crossfibrillar mineral tessellation pattern similar to that observed in lamellar bone, but with greater variance in mineral tesselle morphology and size. We also examined Achilles enthesis structure in Hyp mice, a murine model for the inherited osteomalacic disease X-linked hypophosphatemia (XLH) with calcifying enthesopathy. In Achilles enthesis fibrocartilage of Hyp mice, we show defective crossfibrillar mineral tessellation similar to that which occurs in Hyp lamellar bone. At the cellular level in fibrocartilage, unlike in bone where enlarged osteocyte mineral lacunae are found as peri-osteocytic lesions, mineral lacunar volumes for fibrochondrocytes did not differ between WT and Hyp mice. While both WT and Hyp aged mice demonstrate Achilles tendon midsubstance ectopic mineralization, a consistently defective mineralization pattern was observed in Hyp mice. Strong immunostaining for osteopontin was observed at all mineralization sites examined in both WT and Hyp mice. Taken together, this new 3D ultrastructural information describes details of common mineralization trajectories for enthesis, tendon and bone, which in Hyp/XLH are defective.
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Affiliation(s)
- Daniel J Buss
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Katya Rechav
- Electron Microscopy Unit, Weizmann Institute of Science, Rehovot, Israel
| | - Natalie Reznikov
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Department of Bioengineering, Faculty of Engineering, McGill University, Montreal, Quebec, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Marc D McKee
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada.
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Peserico A, Barboni B, Russo V, Bernabò N, El Khatib M, Prencipe G, Cerveró-Varona A, Haidar-Montes AA, Faydaver M, Citeroni MR, Berardinelli P, Mauro A. Mammal comparative tendon biology: advances in regulatory mechanisms through a computational modeling. Front Vet Sci 2023; 10:1175346. [PMID: 37180059 PMCID: PMC10174257 DOI: 10.3389/fvets.2023.1175346] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 04/03/2023] [Indexed: 05/15/2023] Open
Abstract
There is high clinical demand for the resolution of tendinopathies, which affect mainly adult individuals and animals. Tendon damage resolution during the adult lifetime is not as effective as in earlier stages where complete restoration of tendon structure and property occurs. However, the molecular mechanisms underlying tendon regeneration remain unknown, limiting the development of targeted therapies. The research aim was to draw a comparative map of molecules that control tenogenesis and to exploit systems biology to model their signaling cascades and physiological paths. Using current literature data on molecular interactions in early tendon development, species-specific data collections were created. Then, computational analysis was used to construct Tendon NETworks in which information flow and molecular links were traced, prioritized, and enriched. Species-specific Tendon NETworks generated a data-driven computational framework based on three operative levels and a stage-dependent set of molecules and interactions (embryo-fetal or prepubertal) responsible, respectively, for signaling differentiation and morphogenesis, shaping tendon transcriptional program and downstream modeling of its fibrillogenesis toward a mature tissue. The computational network enrichment unveiled a more complex hierarchical organization of molecule interactions assigning a central role to neuro and endocrine axes which are novel and only partially explored systems for tenogenesis. Overall, this study emphasizes the value of system biology in linking the currently available disjointed molecular data, by establishing the direction and priority of signaling flows. Simultaneously, computational enrichment was critical in revealing new nodes and pathways to watch out for in promoting biomedical advances in tendon healing and developing targeted therapeutic strategies to improve current clinical interventions.
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Fang F, Xiao Y, Zelzer E, Leong KW, Thomopoulos S. A mineralizing pool of Gli1-expressing progenitors builds the tendon enthesis and demonstrates therapeutic potential. Cell Stem Cell 2022; 29:1669-1684.e6. [PMID: 36459968 PMCID: PMC10422080 DOI: 10.1016/j.stem.2022.11.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/27/2022] [Accepted: 11/08/2022] [Indexed: 12/03/2022]
Abstract
The enthesis, a fibrocartilaginous transition between tendon and bone, is necessary for force transfer from muscle to bone to produce joint motion. The enthesis is prone to injury due to mechanical demands, and it cannot regenerate. A better understanding of how the enthesis develops will lead to more effective therapies to prevent pathology and promote regeneration. Here, we used single-cell RNA sequencing to define the developmental transcriptome of the mouse entheses over postnatal stages. Six resident cell types, including enthesis progenitors and mineralizing chondrocytes, were identified along with their transcription factor regulons and temporal regulation. Following the prior discovery of the necessity of Gli1-lineage cells for mouse enthesis development and healing, we then examined their transcriptomes at single-cell resolution and demonstrated clonogenicity and multipotency of the Gli1-expressing progenitors. Transplantation of Gli1-lineage cells to mouse enthesis injuries improved healing, demonstrating their therapeutic potential for enthesis regeneration.
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Affiliation(s)
- Fei Fang
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA; Leni and Peter W. May Department of Orthopaedics, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Yang Xiao
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Elazar Zelzer
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Kam W Leong
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Stavros Thomopoulos
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA.
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