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Chen MY, Zhao FL, Chu WL, Bai MR, Zhang DM. A review of tamoxifen administration regimen optimization for Cre/loxp system in mouse bone study. Biomed Pharmacother 2023; 165:115045. [PMID: 37379643 DOI: 10.1016/j.biopha.2023.115045] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/07/2023] [Accepted: 06/20/2023] [Indexed: 06/30/2023] Open
Abstract
Gene knockout is a technique routinely used in basic experimental research, particularly in mouse skeletal and developmental studies. Tamoxifen-induced Cre/loxp system is known for its temporal and spatial precision and commonly utilized by researchers. However, tamoxifen has been shown its side effects on affecting the phenotype of mouse bone directly. This review aimed to optimize tamoxifen administration regimens including its dosage and duration, to identify an optimal induction strategy that minimizes potential side effects while maintaining recombination efficacy. This study will help researchers in designing gene knockout experiments in bone when using tamoxifen.
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Affiliation(s)
- Ming-Yang Chen
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Fu-Lin Zhao
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Wen-Lin Chu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Ming-Ru Bai
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Department of Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
| | - De-Mao Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China; Institute of Biomedical Engineering, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, China.
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Stein M, Elefteriou F, Busse B, Fiedler IA, Kwon RY, Farell E, Ahmad M, Ignatius A, Grover L, Geris L, Tuckermann J. Why Animal Experiments Are Still Indispensable in Bone Research: A Statement by the European Calcified Tissue Society. J Bone Miner Res 2023; 38:1045-1061. [PMID: 37314012 PMCID: PMC10962000 DOI: 10.1002/jbmr.4868] [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: 11/03/2022] [Revised: 05/03/2023] [Accepted: 06/09/2023] [Indexed: 06/15/2023]
Abstract
Major achievements in bone research have always relied on animal models and in vitro systems derived from patient and animal material. However, the use of animals in research has drawn intense ethical debate and the complete abolition of animal experimentation is demanded by fractions of the population. This phenomenon is enhanced by the reproducibility crisis in science and the advance of in vitro and in silico techniques. 3D culture, organ-on-a-chip, and computer models have improved enormously over the last few years. Nevertheless, the overall complexity of bone tissue cross-talk and the systemic and local regulation of bone physiology can often only be addressed in entire vertebrates. Powerful genetic methods such as conditional mutagenesis, lineage tracing, and modeling of the diseases enhanced the understanding of the entire skeletal system. In this review endorsed by the European Calcified Tissue Society (ECTS), a working group of investigators from Europe and the US provides an overview of the strengths and limitations of experimental animal models, including rodents, fish, and large animals, as well the potential and shortcomings of in vitro and in silico technologies in skeletal research. We propose that the proper combination of the right animal model for a specific hypothesis and state-of-the-art in vitro and/or in silico technology is essential to solving remaining important questions in bone research. This is crucial for executing most efficiently the 3R principles to reduce, refine, and replace animal experimentation, for enhancing our knowledge of skeletal biology, and for the treatment of bone diseases that affect a large part of society. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Merle Stein
- Institute of Comparative Molecular Endocrinology, Ulm University, Ulm, Germany
| | - Florent Elefteriou
- Department of Orthopedic Surgery, Baylor College of Medicine, Houston, TX, USA and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Björn Busse
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Interdisciplinary Competence Center for Interface Research (ICCIR), University Medical Center Hamburg-Eppendorf, Germany
| | - Imke A.K. Fiedler
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Interdisciplinary Competence Center for Interface Research (ICCIR), University Medical Center Hamburg-Eppendorf, Germany
| | - Ronald Young Kwon
- Department of Orthopaedics and Sports Medicine, University of Washington School of Medicine, Seattle, USA and Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, USA
| | - Eric Farell
- Department of Oral and Maxillofacial Surgery, Erasmus MC, University Medical Center Rotterdam, the Netherlands
| | - Mubashir Ahmad
- Institute of Orthopaedic Research and Biomechanics, University Medical Center Ulm, Ulm, Germany
| | - Anita Ignatius
- Institute of Orthopaedic Research and Biomechanics, University Medical Center Ulm, Ulm, Germany
| | - Liam Grover
- Healthcare Technologies Institute, Institute of Translational MedicineHeritage Building Edgbaston, Birmingham
| | - Liesbet Geris
- Biomechanics Research Unit, GIGA In Silico Medicine, University of Liège, Liège, Belgium
- Skeletal Biology & Engineering Research Center, KU Leuven, Leuven, Belgium
| | - Jan Tuckermann
- Institute of Comparative Molecular Endocrinology, Ulm University, Ulm, Germany
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Chai W, Hao W, Liu J, Han Z, Chang S, Cheng L, Sun M, Yan G, Liu Z, Liu Y, Zhang G, Xing L, Chen H, Liu P. Visualizing Cathepsin K-Cre Expression at the Single-Cell Level with GFP Reporters. JBMR Plus 2022; 7:e10706. [PMID: 36699636 PMCID: PMC9850439 DOI: 10.1002/jbm4.10706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 11/10/2022] [Accepted: 11/16/2022] [Indexed: 11/23/2022] Open
Abstract
The Cre/lox system is a fundamental tool for functional genomic studies, and a number of Cre lines have been generated to target genes of interest spatially and temporally in defined cells or tissues; this approach has greatly expanded our knowledge of gene functions. However, the limitations of this system have recently been recognized, and we must address the challenge of so-called nonspecific/off-target effects when a Cre line is utilized to investigate a gene of interest. For example, cathepsin K (Ctsk) has been used as a specific osteoclast marker, and Cre driven by its promoter is widely utilized for osteoclast investigations. However, Ctsk-Cre expression has recently been identified in other cell types, such as osteocytes, periosteal stem cells, and tenocytes. To better understand Ctsk-Cre expression and ensure appropriate use of this Cre line, we performed a comprehensive analysis of Ctsk-Cre expression at the single-cell level in major organs and tissues using two green fluorescent protein (GFP) reporters (ROSA nT-nG and ROSA tdT) and a tissue clearing technique in young and aging mice. The expression profile was further verified by immunofluorescence staining and droplet digital RT-PCR. The results demonstrate that Ctsk-Cre is expressed not only in osteoclasts but also at various levels in osteoblast lineage cells and other major organs/tissues, particularly in the brain, kidney, pancreas, and blood vessels. Furthermore, Ctsk-Cre expression increases markedly in the bone marrow, skeletal muscle, and intervertebral discs in aging mice. These data will be valuable for accurately interpreting data obtained from in vivo studies using Ctsk-Cre mice to avoid potentially misleading conclusions. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Wenhuan Chai
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Weiwei Hao
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Jintao Liu
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Zhenglin Han
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Shiyu Chang
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Liben Cheng
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Mingxin Sun
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Guofang Yan
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Zemin Liu
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Yin Liu
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Guodong Zhang
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Li Xing
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Hongqian Chen
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
| | - Peng Liu
- Laboratory of Bone & Adipose BiologyShanxi Medical UniversityTaiyuanChina
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Davis JL, Pokhrel NK, Cox L, Rohatgi N, Faccio R, Veis DJ. Conditional loss of IKKα in Osterix + cells has no effect on bone but leads to age-related loss of peripheral fat. Sci Rep 2022; 12:4915. [PMID: 35318397 PMCID: PMC8940989 DOI: 10.1038/s41598-022-08914-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 03/10/2022] [Indexed: 11/09/2022] Open
Abstract
NF-κB has been reported to both promote and inhibit bone formation. To explore its role in osteolineage cells, we conditionally deleted IKKα, an upstream kinase required for non-canonical NF-κB activation, using Osterix (Osx)-Cre. Surprisingly, we found no effect on either cancellous or cortical bone, even following mechanical loading. However, we noted that IKKα conditional knockout (cKO) mice began to lose body weight after 6 months of age with severe reductions in fat mass and lower adipocyte size in geriatric animals. qPCR analysis of adipogenic markers in fat pads of cKO mice indicated no difference in early differentiation, but instead markedly lower leptin with age. We challenged young mice with a high fat diet finding that cKO mice gained less weight and showed improved glucose metabolism. Low levels of recombination at the IKKα locus were detected in fat pads isolated from old cKO mice. To determine whether recombination occurs in adipocytes, we examined fat pads in Osx-Cre;TdT reporter mice; these showed increasing Osx-Cre-mediated expression in peripheral adipocytes from 6 weeks to 18 months. Since Osx-Cre drives recombination in peripheral adipocytes with age, we conclude that fat loss in cKO mice is most likely caused by progressive deficits of IKKα in adipocytes.
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Affiliation(s)
- Jennifer L Davis
- Musculoskeletal Research Center, Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Nitin Kumar Pokhrel
- Musculoskeletal Research Center, Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Linda Cox
- Musculoskeletal Research Center, Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Nidhi Rohatgi
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Roberta Faccio
- Musculoskeletal Research Center, Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Shriners Hospitals for Children, St. Louis, MO, 63110, USA
| | - Deborah J Veis
- Musculoskeletal Research Center, Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Shriners Hospitals for Children, St. Louis, MO, 63110, USA.
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Wee NK, Sims NA, Morello R. The Osteocyte Transcriptome: Discovering Messages Buried Within Bone. Curr Osteoporos Rep 2021; 19:604-615. [PMID: 34757588 PMCID: PMC8720072 DOI: 10.1007/s11914-021-00708-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/24/2021] [Indexed: 12/16/2022]
Abstract
PURPOSE OF THE REVIEW Osteocytes are cells embedded within the bone matrix, but their function and specific patterns of gene expression remain only partially defined; this is beginning to change with recent studies using transcriptomics. This unbiased approach can generate large amounts of data and is now being used to identify novel genes and signalling pathways within osteocytes both at baseline conditions and in response to stimuli. This review outlines the methods used to isolate cell populations containing osteocytes, and key recent transcriptomic studies that used osteocyte-containing preparations from bone tissue. RECENT FINDINGS Three common methods are used to prepare samples to examine osteocyte gene expression: digestion followed by sorting, laser capture microscopy, and the isolation of cortical bone shafts. All these methods present challenges in interpreting the data generated. Genes previously not known to be expressed by osteocytes have been identified and variations in osteocyte gene expression have been reported with age, sex, anatomical location, mechanical loading, and defects in bone strength. A substantial proportion of newly identified transcripts in osteocytes remain functionally undefined but several have been cross-referenced with functional data. Future work and improved methods (e.g. scRNAseq) likely provide useful resources for the study of osteocytes and important new information on the identity and functions of this unique cell type within the skeleton.
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Affiliation(s)
- Natalie Ky Wee
- Bone Cell Biology and Disease Unit, St Vincent's Institute of Medical Research, 9 Princes St, Fitzroy, 3065, Australia
| | - Natalie A Sims
- Bone Cell Biology and Disease Unit, St Vincent's Institute of Medical Research, 9 Princes St, Fitzroy, 3065, Australia
- Department of Medicine, The University of Melbourne, St. Vincent's Hospital, Melbourne, 3065, Australia
| | - Roy Morello
- Department of Physiology & Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
- Department of Orthopaedic Surgery, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
- Division of Genetics, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
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