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Xu W, Zhang Y, Li L, Pan L, Lu L, Zhi S, Li W. Osteocyte-derived exosomes regulate the DLX2/wnt pathway to alleviate osteoarthritis by mediating cartilage repair. Autoimmunity 2024; 57:2364686. [PMID: 38946534 DOI: 10.1080/08916934.2024.2364686] [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: 09/19/2023] [Accepted: 06/02/2024] [Indexed: 07/02/2024]
Abstract
BACKGROUND Chondrocyte viability, apoptosis, and migration are closely related to cartilage injury in osteoarthritis (OA) joints. Exosomes are identified as potential therapeutic agents for OA. OBJECTIVE This study aimed to investigate the role of exosomes derived from osteocytes in OA, particularly focusing on their effects on cartilage repair and molecular mechanisms. METHODS An injury cell model was established by treating chondrocytes with IL-1β. Cartilage repair was evaluated using cell counting kit-8, flow cytometry, scratch test, and Western Blot. Molecular mechanisms were analyzed using quantitative real-time PCR, bioinformatic analysis, and Western Blot. An OA mouse model was established to explore the role of exosomal DLX2 in vivo. RESULTS Osteocyte-released exosomes promoted cell viability and migration, and inhibited apoptosis and extracellular matrix (ECM) deposition. Moreover, exosomes upregulated DLX2 expression, and knockdown of DLX2 activated the Wnt pathway. Additionally, exosomes attenuated OA in mice by transmitting DLX2. CONCLUSION Osteocyte-derived exosomal DLX2 alleviated IL-1β-induced cartilage repair and inactivated the Wnt pathway, thereby alleviating OA progression. The findings suggested that osteocyte-derived exosomes may hold promise as a treatment for OA.
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Affiliation(s)
- Wenjuan Xu
- Chongqing Emergency Medical Center, Chongqing University Central Hospital, Clinical Laboratory, Chongqing, China
| | - Yuanyuan Zhang
- Chongqing Emergency Medical Center, Chongqing University Central Hospital, Clinical Laboratory, Chongqing, China
| | - Lijuan Li
- Chongqing Emergency Medical Center, Chongqing University Central Hospital, Clinical Laboratory, Chongqing, China
| | - Liyan Pan
- Chongqing Emergency Medical Center, Chongqing University Central Hospital, Clinical Laboratory, Chongqing, China
| | - Li Lu
- Chongqing Emergency Medical Center, Chongqing University Central Hospital, Clinical Laboratory, Chongqing, China
| | - Shenshen Zhi
- Department of Blood Transfusion, Chongqing University Central Hospital, School of Medicine, Chongqing University, Chongqing, China
| | - Wei Li
- Chongqing Emergency Medical Center, Chongqing University Central Hospital, Clinical Laboratory, Chongqing, China
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Benard EL, Küçükaylak I, Hatzold J, Berendes KU, Carney TJ, Beleggia F, Hammerschmidt M. wnt10a is required for zebrafish median fin fold maintenance and adult unpaired fin metamorphosis. Dev Dyn 2024; 253:566-592. [PMID: 37870737 PMCID: PMC11035493 DOI: 10.1002/dvdy.672] [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: 08/24/2023] [Revised: 10/03/2023] [Accepted: 10/08/2023] [Indexed: 10/24/2023] Open
Abstract
BACKGROUND Mutations of human WNT10A are associated with odonto-ectodermal dysplasia syndromes. Here, we present analyses of wnt10a loss-of-function mutants in the zebrafish. RESULTS wnt10a mutant zebrafish embryos display impaired tooth development and a collapsing median fin fold (MFF). Rescue experiments show that wnt10a is essential for MFF maintenance both during embryogenesis and later metamorphosis. The MFF collapse could not be attributed to increased cell death or altered proliferation rates of MFF cell types. Rather, wnt10a mutants show reduced expression levels of dlx2a in distal-most MFF cells, followed by compromised expression of col1a1a and other extracellular matrix proteins encoding genes. Transmission electron microscopy analysis shows that although dermal MFF compartments of wnt10a mutants initially are of normal morphology, with regular collagenous actinotrichia, positioning of actinotrichia within the cleft of distal MFF cells becomes compromised, coinciding with actinotrichia shrinkage and MFF collapse. CONCLUSIONS MFF collapse of wnt10a mutant zebrafish is likely caused by the loss of distal properties in the developing MFF, strikingly similar to the proposed molecular pathomechanisms underlying the teeth defects caused by the loss of Wnt10 in fish and mammals. In addition, it points to thus fur unknown mechanisms controlling the linear growth and stability of actinotrichia and their collagen fibrils.
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Affiliation(s)
- Erica L. Benard
- Institute of Zoology, Developmental Biology Unit,
University of Cologne, Cologne, Germany
| | - Ismail Küçükaylak
- Institute of Zoology, Developmental Biology Unit,
University of Cologne, Cologne, Germany
| | - Julia Hatzold
- Institute of Zoology, Developmental Biology Unit,
University of Cologne, Cologne, Germany
| | - Kilian U.W. Berendes
- Institute of Zoology, Developmental Biology Unit,
University of Cologne, Cologne, Germany
| | - Thomas J. Carney
- Discovery Research Division, Institute of Molecular and
Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research),
Singapore, Republic of Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological
University, Singapore, Republic of Singapore
| | - Filippo Beleggia
- Department I of Internal Medicine, Faculty of Medicine and
University Hospital Cologne, University of Cologne, Germany
- Department of Translational Genomics, Faculty of Medicine
and University Hospital Cologne, University of Cologne, Cologne, Germany
- Mildred Scheel School of Oncology Aachen Bonn Cologne
Düsseldorf (MSSO ABCD), Faculty of Medicine and University Hospital Cologne,
University of Cologne, Cologne, Germany
| | - Matthias Hammerschmidt
- Institute of Zoology, Developmental Biology Unit,
University of Cologne, Cologne, Germany
- Center for Molecular Medicine Cologne, University of
Cologne, Cologne, Germany
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Li Y, Zhu S, Luo J, Tong Y, Zheng Y, Ji L, He Z, Jing Q, Huang J, Zhang Y, Bi Q. The Protective Effect of Selenium Nanoparticles in Osteoarthritis: In vitro and in vivo Studies. Drug Des Devel Ther 2023; 17:1515-1529. [PMID: 37249927 PMCID: PMC10216853 DOI: 10.2147/dddt.s407122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Accepted: 04/21/2023] [Indexed: 05/31/2023] Open
Abstract
Introduction Osteoarthritis (OA) is a common chronic joint disease characterized by articular cartilage degeneration. OA usually manifests as joint pain, limited mobility, and joint effusion. Currently, the primary OA treatment is non-steroidal anti-inflammatory drugs (NSAIDs). Although they can alleviate the disease's clinical symptoms and signs, the drugs have some side effects. Selenium nanoparticles (SeNPs) may be an alternative to relieve OA symptoms. Materials and Results We confirmed the anti-inflammatory effect of selenium nanoparticles (SeNPs) in vitro and in vivo experiments for OA disease in this study. In vitro experiments, we found that SeNPs could significantly reduce the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), the major inflammatory factors, and had significant anti-inflammatory and anti-arthritic effects. SeNPs can inhibit reactive oxygen species (ROS) production and increased glutathione peroxidase (GPx) activity in interleukin-1beta (IL-1β)-stimulated cells. Additionally, SeNPs down-regulated matrix metalloproteinase-13 (MMP-13) and thrombospondin motifs 5 (ADAMTS-5) expressions, while up-regulated type II collagen (COL-2) and aggrecan (ACAN) expressions stimulated by IL-1β. The findings also indicated that SeNPs may exert their effects through suppressing the NF-κB p65 and p38/MAPK pathways. In vivo experiments, the prevention of OA development brought on by SeNPs was demonstrated using a DMM model. Discussion Our results suggest that SeNPs may be a potential anti-inflammatory agent for treating OA.
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Affiliation(s)
- Yong Li
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, People’s Republic of China
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Senbo Zhu
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Junchao Luo
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Yu Tong
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Yixuan Zheng
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Lichen Ji
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Zeju He
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Qiangan Jing
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Jiaqing Huang
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Yinjun Zhang
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, People’s Republic of China
| | - Qing Bi
- Laboratory Medicine Center, Department of Laboratory Medicine, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China
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Sun J, Zhang J, Bian Q, Wang X. Effects of Dlx2 overexpression on the genes associated with the maxillary process in the early mouse embryo. Front Genet 2023; 14:1085263. [PMID: 36891149 PMCID: PMC9986417 DOI: 10.3389/fgene.2023.1085263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 02/09/2023] [Indexed: 02/22/2023] Open
Abstract
The transcription factor Dlx2 plays an important role in craniomaxillofacial development. Overexpression or null mutations of Dlx2 can lead to craniomaxillofacial malformation in mice. However, the transcriptional regulatory effects of Dlx2 during craniomaxillofacial development remain to be elucidated. Using a mouse model that stably overexpresses Dlx2 in neural crest cells, we comprehensively characterized the effects of Dlx2 overexpression on the early development of maxillary processes in mice by conducting bulk RNA-Seq, scRNA-Seq and CUT&Tag analyses. Bulk RNA-Seq results showed that the overexpression of Dlx2 resulted in substantial transcriptome changes in E10.5 maxillary prominences, with genes involved in RNA metabolism and neuronal development most significantly affected. The scRNA-Seq analysis suggests that overexpression of Dlx2 did not change the differentiation trajectory of mesenchymal cells during this development process. Rather, it restricted cell proliferation and caused precocious differentiation, which may contribute to the defects in craniomaxillofacial development. Moreover, the CUT&Tag analysis using DLX2 antibody revealed enrichment of MNT and Runx2 motifs at the putative DLX2 binding sites, suggesting they may play critical roles in mediating the transcriptional regulatory effects of Dlx2. Together, these results provide important insights for understanding the transcriptional regulatory network of Dlx2 during craniofacial development.
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Affiliation(s)
- Jian Sun
- Shanghai Key Laboratory of Stomatology, National Center for Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral and Cranio-Maxillofacial Surgery, College of Stomatology, Shanghai Research Institute of Stomatology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jianfei Zhang
- Shanghai Key Laboratory of Stomatology, National Center for Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral and Cranio-Maxillofacial Surgery, College of Stomatology, Shanghai Research Institute of Stomatology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Qian Bian
- Shanghai Key Laboratory of Stomatology, National Center for Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral and Cranio-Maxillofacial Surgery, College of Stomatology, Shanghai Research Institute of Stomatology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai, China
| | - Xudong Wang
- Shanghai Key Laboratory of Stomatology, National Center for Stomatology, National Clinical Research Center for Oral Diseases, Department of Oral and Cranio-Maxillofacial Surgery, College of Stomatology, Shanghai Research Institute of Stomatology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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A novel Atlantic salmon (Salmo salar) bone collagen peptide delays osteoarthritis development by inhibiting cartilage matrix degradation and anti-inflammatory. Food Res Int 2022; 162:112148. [PMID: 36461366 DOI: 10.1016/j.foodres.2022.112148] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 11/13/2022] [Accepted: 11/15/2022] [Indexed: 11/21/2022]
Abstract
Nowadays, the biological activity of collagen peptides has been revealed, but the effect of Atlantic salmon (Salmo salar) bone-derived collagen peptide (CPs) on osteoarthritis remains unclear. In this study, CPs was identified as a small molecular weight peptide rich in Gly-X-Y structure. Meanwhile, interleukin-1β (IL-1β)-induced hypertrophic chondrocytes and partial medial meniscectomy (pMMx) surgery model in rats were performed. In IL-1β stimulated chondrocytes, CPs significantly increased the type-II collagen content, reduced the type-X collagen abundance and chondrocytes apoptosis. Meanwhile, CPs reversed the increased expression of matrix metalloproteinase, metalloproteinase with thrombospondin motifs and RUNX family transcription factor 2 in chondrocytes induced by IL-1β. In vivo, CPs increased pain tolerance of rats and without organ toxicity at 1.6 g/kg.bw. CPs significantly decreased the levels of COMP and Helix-II in serum. Furthermore, a significant decrease of IL-1β in synovial fluid and cartilage tissue were observed by CPs intervention. From Micro-CT, CPs (0.8 g/kg.bw) significantly decreased Tb.sp and SMI value. Meanwhile, the expression of tumor necrosis factor and interleukin-6 were reduced by CPs administration both in vitro and in vivo. Together, CPs showed potential to be a novel and safe dietary supplement for helping anti-inflammatory and cartilage regeneration, ultimately hindering osteoarthritis development. However, the clear mechanism of CPs's positive effect on osteoarthritis needs to be further explored.
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Liu Z, Huang Y, Jin X, Liu L, Gu H. PCB153 suppressed autophagy via PI3K/Akt/mTOR and RICTOR/Akt/mTOR signaling by the upregulation of microRNA-155 in rat primary chondrocytes. Toxicol Appl Pharmacol 2022; 449:116135. [PMID: 35732230 DOI: 10.1016/j.taap.2022.116135] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 06/07/2022] [Accepted: 06/15/2022] [Indexed: 02/04/2023]
Abstract
Polychlorinated biphenyls (PCBs) are a typical type of persistent organic pollutant. PCB exposure is associated to the occurrence and development of osteoarthritis (OA); however, the involved mechanisms have yet to be elucidated. Here, we investigated the pro-osteoarthritic effect of 2, 2', 4, 4', 5, 5'-hexachlorobiphenyl (PCB153), and the involvement of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) and the RICTOR/Akt/mTOR signaling pathways. PCB153 of 20 and 30 μM increased the expression of MMP13 and decreased the expression of type II collagen, in a concentration-dependent manner. PCB153 treatment reduced the expression of Beclin 1 and LC3B, but increased the expression of p62 by upregulating miR-155 levels. PCB153 treatment activated the PI3K/Akt/mTOR signaling pathway by upregulating miR-155 levels. RICTOR was involved in activating the Akt/mTOR signaling pathway, and was also regulated by miR-155. In conclusion, PCB153 could promote the degradation of the extracellular matrix of chondrocytes by upregulating miR-155 via a mechanism related to the activation of the PI3K/Akt/mTOR and RICTOR/Akt/mTOR signaling pathway, which suppressed autophagy and facilitated the development of OA. MiR-155 may represent potential therapeutic targets to alleviate the development of OA.
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Affiliation(s)
- Ziyu Liu
- Department of Nutrition and Food Hygiene, School of Public Health, China Medical University, 110122, China
| | - Yue Huang
- Department of Nutrition and Food Hygiene, School of Public Health, China Medical University, 110122, China
| | - Xin Jin
- Department of Nutrition and Food Hygiene, School of Public Health, China Medical University, 110122, China
| | - Li Liu
- Department of Nutrition and Food Hygiene, School of Public Health, China Medical University, 110122, China
| | - Hailun Gu
- Department of Orthopedics, Shengjing Hospital, China Medical University, 110004, China.
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Sun J, Ha N, Liu Z, Bian Q, Wang X. A Neural Crest-specific Overexpression Mouse Model Reveals the Transcriptional Regulatory Effects of Dlx2 During Maxillary Process Development. Front Physiol 2022; 13:855959. [PMID: 35514355 PMCID: PMC9070692 DOI: 10.3389/fphys.2022.855959] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Accepted: 03/14/2022] [Indexed: 11/13/2022] Open
Abstract
Craniofacial morphogenesis is a complex process that requires precise regulation of cell proliferation, migration, and differentiation. Perturbations of this process cause a series of craniofacial deformities. Dlx2 is a critical transcription factor that regulates the development of the first branchial arch. However, the transcriptional regulatory functions of Dlx2 during craniofacial development have been poorly understood due to the lack of animal models in which the Dlx2 level can be precisely modulated. In this study, we constructed a Rosa26 site-directed Dlx2 gene knock-in mouse model Rosa26 CAG-LSL-Dlx2-3xFlag for conditionally overexpressing Dlx2. By breeding with wnt1 cre mice, we obtained wnt1 cre ; Rosa26 Dlx2/- mice, in which Dlx2 is overexpressed in neural crest lineage at approximately three times the endogenous level. The wnt1 cre ; Rosa26 Dlx2/- mice exhibited consistent phenotypes that include cleft palate across generations and individual animals. Using this model, we demonstrated that Dlx2 caused cleft palate by affecting maxillary growth and uplift in the early-stage development of maxillary prominences. By performing bulk RNA-sequencing, we demonstrated that Dlx2 overexpression induced significant changes in many genes associated with critical developmental pathways. In summary, our novel mouse model provides a reliable and consistent system for investigating Dlx2 functions during development and for elucidating the gene regulatory networks underlying craniofacial development.
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Affiliation(s)
- Jian Sun
- Department of Oral and Cranio-Maxillofacial Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, Shanghai, China
| | - NaYoung Ha
- Department of Oral and Cranio-Maxillofacial Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, Shanghai, China
| | - Zhixu Liu
- Department of Oral and Cranio-Maxillofacial Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, Shanghai, China
| | - Qian Bian
- Department of Oral and Cranio-Maxillofacial Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Institute of Precision Medicine, Shanghai, China
| | - Xudong Wang
- Department of Oral and Cranio-Maxillofacial Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, Shanghai, China
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Overexpression of Dlx2 enhances osteogenic differentiation of BMSCs and MC3T3-E1 cells via direct upregulation of Osteocalcin and Alp. Int J Oral Sci 2019; 11:12. [PMID: 30880332 PMCID: PMC6421343 DOI: 10.1038/s41368-019-0046-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 01/02/2019] [Accepted: 01/03/2019] [Indexed: 01/17/2023] Open
Abstract
Genetic studies have revealed a critical role of Distal-homeobox (Dlx) genes in bone formation, and our previous study showed that Dlx2 overexpressing in neural crest cells leads to profound abnormalities of the craniofacial tissues. The aim of this study was to investigate the role and the underlying molecular mechanisms of Dlx2 in osteogenic differentiation of mouse bone marrow stromal cells (BMSCs) and pre-osteoblast MC3T3-E1 cells. Initially, we observed upregulation of Dlx2 during the early osteogenesis in BMSCs and MC3T3-E1 cells. Moreover, Dlx2 overexpression enhanced alkaline phosphatase (ALP) activity and extracellular matrix mineralization in BMSCs and MC3T3-E1 cell line. In addition, micro-CT of implanted tissues in nude mice confirmed that Dlx2 overexpression in BMSCs promoted bone formation in vivo. Unexpectedly, Dlx2 overexpression had little impact on the expression level of the pivotal osteogenic transcription factors Runx2, Dlx5, Msx2, and Osterix, but led to upregulation of Alp and Osteocalcin (OCN), both of which play critical roles in promoting osteoblast maturation. Importantly, luciferase analysis showed that Dlx2 overexpression stimulated both OCN and Alp promoter activity. Through chromatin-immunoprecipitation assay and site-directed mutagenesis analysis, we provide molecular evidence that Dlx2 transactivates OCN and Alp expression by directly binding to the Dlx2-response cis-acting elements in the promoter of the two genes. Based on these findings, we demonstrate that Dlx2 overexpression enhances osteogenic differentiation in vitro and accelerates bone formation in vivo via direct upregulation of the OCN and Alp gene, suggesting that Dlx2 plays a crucial role in osteogenic differentiation and bone formation. The distal-less homeobox (Dlx) gene family is related to various features of bone development, and the Dlx2 member of that family has been found to play a crucial role in bone formation. A team headed by Steve Guofang Shen at the Shanghai Jiao Tong University School of Medicine in China investigated the function of Dlx2 in osteogenic (bone development) differentiation of mouse bone marrow stromal cells (BMSCs) and MC3T3-E1 cells (precursors of osteoblasts, the major cellular component of bone). The team found that overexpression of Dlx2 promotes osteogenic differentiation in vitro and accelerates bone formation in vivo by enhancing Osteocalcin and Alp genes (both of which play critical roles in promoting osteoblast maturation). The authors conclude that their results suggest a promising future strategy for treating bone defects where BMSCs overexpress Dlx2.
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