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Li X, Deng Z, Lu W. Mechanistic study of the effect of flexible fixation and load-bearing stress environment on fracture healing and shaping. Animal Model Exp Med 2024. [PMID: 38978345 DOI: 10.1002/ame2.12448] [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: 12/18/2023] [Revised: 04/27/2024] [Accepted: 05/22/2024] [Indexed: 07/10/2024] Open
Abstract
BACKGROUND The biomechanical environment created by suture-button fixation Latarjet is conducive to the healing and shaping of the transplanted coracoid, but its mechanism remains unclear. The latest research has found that the absence of stem cell chemokine (CXCL12) impeded bone regeneration in Sonic Hedgehog (SHH)-deficient animals. However, whether the biomechanical environment affects SHH and CXCL12 function has not been studied. METHODS Rat fracture models were constructed to simulate stress environments under non-load-bearing and load-bearing conditions. The fracture healing and shaping, as well as the expression levels of SHH and CXCL12, were assessed through gross viewing, micro-computed tomography (micro-CT), and histochemical staining. RESULTS Under flexible fixation, the relative bone volume (BV/TV) of rats exposed to the load-bearing stress environment was significantly higher than that of rats under a non-load-bearing stress environment (p ≤ 0.05). Adverse bone shaping was not observed in rats subjected to flexible fixation. The levels of SHH and CXCL12 in load-bearing rats exhibited significant elevation (p ≤ 0.05). Under a load-bearing stress environment, no significant difference was observed in the BV/TV between the flexible fixation group and the rigid fixation group (p ≥ 0.05), but there was excessive hyperplasia of the fracture callus in the rigid fixation group. The levels of SHH and CXCL12 in rats subjected to rigid fixation were significantly elevated (p ≤ 0.05). CONCLUSIONS Flexible fixation and load-bearing stress environment may contribute to bone healing and shaping by influencing the levels of SHH and CXCL12, suggested that this mechanism may be relevant to the healing and shaping of the transplanted coracoid after suture-button fixation Latarjet.
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Affiliation(s)
- Xingfu Li
- Department of Sports Medicine, Shenzhen Second People's Hospital (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong, China
- Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, School of Biomedical Engineering, Shenzhen University Medical School, Shenzhen, Guangdong, China
| | - Zhenhan Deng
- Department of Sports Medicine, Shenzhen Second People's Hospital (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong, China
- Department of Orthopedics Surgery, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Wei Lu
- Department of Sports Medicine, Shenzhen Second People's Hospital (The First Affiliated Hospital of Shenzhen University), Shenzhen, Guangdong, China
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Rundle CH, Gomez GA, Pourteymoor S, Mohan S. Sequential application of small molecule therapy enhances chondrogenesis and angiogenesis in murine segmental defect bone repair. J Orthop Res 2023; 41:1471-1481. [PMID: 36448182 PMCID: PMC10506518 DOI: 10.1002/jor.25493] [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: 04/06/2022] [Revised: 10/03/2022] [Accepted: 11/28/2022] [Indexed: 12/05/2022]
Abstract
The increasing incidence of physiologic/pathologic conditions that impair the otherwise routine healing of endochondral bone fractures and the occurrence of severe bone injuries necessitate novel approaches to enhance clinically challenging bone fracture repair. To promote the healing of nonunion fractures, we tested an approach that used two small molecules to sequentially enhance cartilage development and conversion to the bone in the callus of a murine femoral segmental defect nonunion model of bone injury. Systemic injections of smoothened agonist 21k (SAG21k) were used to stimulate chondrogenesis through the activation of the sonic hedgehog (SHH) pathway early in bone repair, while injections of the prolyl hydroxylase domain (PHD)2 inhibitor, IOX2, were used to stimulate hypoxia signaling-mediated endochondral bone formation. The expression of SHH pathway genes and Phd2 target genes was increased in chondrocyte cell lines in response to SAG21k and IOX2 treatment, respectively. The segmental defect responded to sequential systemic administration of these small molecules with increased chondrocyte expression of PTCH1, GLI1, and SOX9 in response to SAG and increased expression of hypoxia-induced factor-1α and vascular endothelial growth factor-A in the defect tissues in response to IOX2. At 6 weeks postsurgery, the combined SAG-IOX2 therapy produced increased bone formation in the defect with the bony union over the injury. Clinical significance: This therapeutic approach was successful in promoting cartilage and bone formation within a critical-size segmental defect and established the utility of a sequential small molecule therapy for the enhancement of fracture callus development in clinically challenging bone injuries.
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Affiliation(s)
- Charles H. Rundle
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
- Department of Medicine, Loma Linda University, Loma Linda, California, USA
| | - Gustavo A. Gomez
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
| | - Sheila Pourteymoor
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, VA Loma Linda Healthcare System, Loma Linda, California, USA
- Department of Medicine, Loma Linda University, Loma Linda, California, USA
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Kloen P, Loots G, Hamdy R, Smit T. Bridging the gap: compressing non-unions for proper cellular signaling. Med Hypotheses 2022. [DOI: 10.1016/j.mehy.2022.110794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Hixon KR, McKenzie JA, Sykes DAW, Yoneda S, Hensley A, Buettmann EG, Zheng H, Skouteris D, McAlinden A, Miller AN, Silva MJ. Ablation of Proliferating Osteoblast Lineage Cells After Fracture Leads to Atrophic Nonunion in a Mouse Model. J Bone Miner Res 2021; 36:2243-2257. [PMID: 34405443 PMCID: PMC8719642 DOI: 10.1002/jbmr.4424] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 07/15/2021] [Accepted: 08/10/2021] [Indexed: 01/19/2023]
Abstract
Nonunion is defined as the permanent failure of a fractured bone to heal, often necessitating surgical intervention. Atrophic nonunions are a subtype that are particularly difficult to treat. Animal models of atrophic nonunion are available; however, these require surgical or radiation-induced trauma to disrupt periosteal healing. These methods are invasive and not representative of many clinical nonunions where osseous regeneration has been arrested by a "failure of biology". We hypothesized that arresting osteoblast cell proliferation after fracture would lead to atrophic nonunion in mice. Using mice that express a thymidine kinase (tk) "suicide gene" driven by the 3.6Col1a1 promoter (Col1-tk), proliferating osteoblast lineage cells can be ablated upon exposure to the nucleoside analog ganciclovir (GCV). Wild-type (WT; control) and Col1-tk littermates were subjected to a full femur fracture and intramedullary fixation at 12 weeks age. We confirmed abundant tk+ cells in fracture callus of Col-tk mice dosed with water or GCV, specifically many osteoblasts, osteocytes, and chondrocytes at the cartilage-bone interface. Histologically, we observed altered callus composition in Col1-tk mice at 2 and 3 weeks postfracture, with significantly less bone and more fibrous tissue. Col1-tk mice, monitored for 12 weeks with in vivo radiographs and micro-computed tomography (μCT) scans, had delayed bone bridging and reduced callus size. After euthanasia, ex vivo μCT and histology showed failed union with residual bone fragments and fibrous tissue in Col1-tk mice. Biomechanical testing showed a failure to recover torsional strength in Col1-tk mice, in contrast to WT. Our data indicates that suppression of proliferating osteoblast-lineage cells for at least 2 weeks after fracture blunts the formation and remodeling of a mineralized callus leading to a functional nonunion. We propose this as a new murine model of atrophic nonunion. © 2021 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Katherine R Hixon
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - Jennifer A McKenzie
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - David A W Sykes
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
| | - Susumu Yoneda
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - Austin Hensley
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Evan G Buettmann
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Hongjun Zheng
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - Dimitrios Skouteris
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - Audrey McAlinden
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA.,Department of Cell Biology & Physiology, Washington University in St. Louis, St. Louis, MO, USA.,St. Louis Shriners Hospital Research Center, Shriners Hospital for Children, St. Louis, MO, USA
| | - Anna N Miller
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
| | - Matthew J Silva
- Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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Abstract
PURPOSE The goal of this study was to identify bone defects of critical size in C57BL/6 mouse mandibles. MATERIALS AND METHODS Twenty-four male mice were included in this study. All mice underwent surgeries on their left mandibles. Mandibular defects of 1.0 mm (n = 8), 1.6 mm (n = 8), and 2.3 mm (n = 8) were created. For the investigation of bone healing after an 8-week period, micro-computed tomography scans and histomorphology were performed. RESULTS Mandibular bone nonunions were seen 0/8 in the 1.0-mm group, 6/8 in the 1.6-mm group, and 8/8 in the 2.3-mm group. The outcome of micro-computed tomography showed that, after 8 weeks, the bone mineral density and the bone volume to total volume ratio were significantly different among the 3 groups. The defect gaps in the nonunion 1.6- and 2.3-mm groups were filled with connective tissue, and no obvious bone formation was found. Additionally, in quantitative analysis, according to the new bone fill calculations, the percentages were 91.85% ± 8.03% in the 1.0-mm group, 59.84% ± 20.60% in the 1.6-mm group, and 15.36% ± 8.28% in the 2.3-mm group, which indicated statistically significantly lower defect healing in the 2.3-mm group. CONCLUSIONS The creation of 2.3-mm mandibular defects produces osseous nonunion in C57BL/6 mice.
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