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Han J, Rindone AN, Elisseeff JH. Immunoengineering Biomaterials for Musculoskeletal Tissue Repair across Lifespan. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2311646. [PMID: 38416061 PMCID: PMC11239302 DOI: 10.1002/adma.202311646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 01/23/2024] [Indexed: 02/29/2024]
Abstract
Musculoskeletal diseases and injuries are among the leading causes of pain and morbidity worldwide. Broad efforts have focused on developing pro-regenerative biomaterials to treat musculoskeletal conditions; however, these approaches have yet to make a significant clinical impact. Recent studies have demonstrated that the immune system is central in orchestrating tissue repair and that targeting pro-regenerative immune responses can improve biomaterial therapeutic outcomes. However, aging is a critical factor negatively affecting musculoskeletal tissue repair and immune function. Hence, understanding how age affects the response to biomaterials is essential for improving musculoskeletal biomaterial therapies. This review focuses on the intersection of the immune system and aging in response to biomaterials for musculoskeletal tissue repair. The article introduces the general impacts of aging on tissue physiology, the immune system, and the response to biomaterials. Then, it explains how the adaptive immune system guides the response to injury and biomaterial implants in cartilage, muscle, and bone and discusses how aging impacts these processes in each tissue type. The review concludes by highlighting future directions for the development and translation of personalized immunomodulatory biomaterials for musculoskeletal tissue repair.
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Affiliation(s)
- Jin Han
- Translational Tissue Engineering Center, Wilmer Eye Institute and Department of Biomedical Engineering, Johns Hopkins University; Baltimore, MD 21231, USA
| | - Alexandra N. Rindone
- Translational Tissue Engineering Center, Wilmer Eye Institute and Department of Biomedical Engineering, Johns Hopkins University; Baltimore, MD 21231, USA
| | - Jennifer H. Elisseeff
- Translational Tissue Engineering Center, Wilmer Eye Institute and Department of Biomedical Engineering, Johns Hopkins University; Baltimore, MD 21231, USA
- Bloomberg~Kimmel Institute for Cancer Immunotherapy, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine; Baltimore, MD 21231, USA
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University; Baltimore, MD 21231, USA
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Koch DW, Froneberger A, Berglund A, Connard S, Souther A, Schnabel LV. IL-1β + TGF-β2 dual-licensed mesenchymal stem cells have reduced major histocompatibility class I expression and positively modulate tenocyte migration, metabolism, and gene expression. J Am Vet Med Assoc 2024; 262:S61-S72. [PMID: 38547589 PMCID: PMC11187728 DOI: 10.2460/javma.23.12.0708] [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: 12/22/2023] [Accepted: 03/08/2024] [Indexed: 04/24/2024]
Abstract
OBJECTIVE The study objectives were to 1) determine the mesenchymal stem cell (MSC) surface expression of major histocompatibility complex (MHC) class I and transcriptome-wide gene expression changes following IL-1β + TGF-β2 dual licensing and 2) evaluate if IL-1β + TGF-β2 dual-licensed MSCs had a greater ability to positively modulate tenocyte function compared to naive MSCs. SAMPLE Equine bone marrow-derived MSCs from 6 donors and equine superficial digital flexor tenocytes from 3 donors. METHODS Experiments were performed in vitro. Flow cytometry and bulk RNA sequencing were utilized to determine naive and dual-licensed MSC phenotype and transcriptome-wide changes in gene expression. Conditioned media were generated from MSCs and utilized in tenocyte cell culture assays as a method to determine the effect of MSC paracrine factors on tenocyte function. RESULTS Dual-licensed MSCs have a reduced expression of MHC class I and exhibit enrichment in functional pathways associated with the extracellular matrix, cell signaling, and tissue development. Additionally, dual-licensed MSC-conditioned media significantly improved in vitro tenocyte migration and metabolism to a greater degree than naive MSC-conditioned media. In tenocytes exposed to IL-1β, dual-licensed conditioned media also positively modulated tenocyte gene expression. CLINICAL RELEVANCE Our data indicate that conditioned media containing paracrine factors secreted from dual-licensed MSCs significantly modulates in vitro tenocyte function, which may confer benefits in vivo to healing tendons following injury. Additionally, due to reduced MHC class I expression in dual-licensed MSCs, this technique may also provide an avenue to provide an effective "off-the-shelf" allogenic source of MSCs.
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Affiliation(s)
- Drew W. Koch
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
- Comparative Medicine Institute, North Carolina State University, Raleigh, NC
| | - Anna Froneberger
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
| | - Alix Berglund
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
- Comparative Medicine Institute, North Carolina State University, Raleigh, NC
| | - Shannon Connard
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
- Comparative Medicine Institute, North Carolina State University, Raleigh, NC
| | - Alexis Souther
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
| | - Lauren V. Schnabel
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
- Comparative Medicine Institute, North Carolina State University, Raleigh, NC
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López-Cerdá S, Molinaro G, Tello RP, Correia A, Künig S, Steinberger P, Jeltsch M, Hirvonen JT, Barreto G, Stöckl J, Santos HA. Study of the Synergistic Immunomodulatory and Antifibrotic Effects of Dual-Loaded Budesonide and Serpine1 siRNA Lipid-Polymer Nanoparticles Targeting Macrophage Dysregulation in Tendinopathy. ACS APPLIED MATERIALS & INTERFACES 2024; 16:18643-18657. [PMID: 38564504 DOI: 10.1021/acsami.4c02363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Musculoskeletal diseases involving tissue injury comprise tendon, ligament, and muscle injury. Recently, macrophages have been identified as key players in the tendon repair process, but no therapeutic strategy involving dual drug delivery and gene delivery to macrophages has been developed for targeting the two main dysregulated aspects of macrophages in tendinopathy, i.e., inflammation and fibrosis. Herein, the anti-inflammatory and antifibrotic effects of dual-loaded budesonide and serpine1 siRNA lipid-polymer hybrid nanoparticles (LPNs) are evaluated in murine and human macrophage cells. The modulation of the gene and protein expression of factors associated with inflammation and fibrosis in tendinopathy is demonstrated by real time polymerase chain reaction and Western blot. Macrophage polarization to the M2 phenotype and a decrease in the production of pro-inflammatory cytokines are confirmed in macrophage cell lines and primary cells. The increase in the activity of a matrix metalloproteinase involved in tissue remodelling is proven, and studies evaluating the interactions of LPNs with T cells proved that dual-loaded LPNs act specifically on macrophages and do not induce any collateral effects on T cells. Overall, these dual-loaded LPNs are a promising combinatorial therapeutic strategy with immunomodulatory and antifibrotic effects in dysregulated macrophages in the context of tendinopathy.
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Affiliation(s)
- Sandra López-Cerdá
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
| | - Giuseppina Molinaro
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
| | - Rubén Pareja Tello
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
| | - Alexandra Correia
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
| | - Sarojinidevi Künig
- Centre for Pathophysiology, Infectiology and Immunology, Institute of Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Peter Steinberger
- Centre for Pathophysiology, Infectiology and Immunology, Institute of Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Michael Jeltsch
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
- Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki FI-00014, Finland
- Wihuri Research Institute, Helsinki FI-00014, Finland
- Helsinki One Health, University of Helsinki, Helsinki FI-00014, Finland
| | - Jouni T Hirvonen
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
| | - Goncalo Barreto
- Translational Immunology Research Program, Faculty of Medicine, University of Helsinki, Helsinki FI-00014, Finland
- Orton Orthopedic Hospital, Tenholantie 10, Helsinki 00280, Finland
- Medical Ultrasonics Laboratory (MEDUSA), Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo 02150, Finland
| | - Johannes Stöckl
- Centre for Pathophysiology, Infectiology and Immunology, Institute of Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Hélder A Santos
- Drug Research Program, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Helsinki FI-00014, Finland
- Department of Biomaterials and Biomedical Technology, University Medical Center Groningen, University of Groningen, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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Steltzer SS, Abraham AC, Killian ML. Interfacial Tissue Regeneration with Bone. Curr Osteoporos Rep 2024; 22:290-298. [PMID: 38358401 PMCID: PMC11060924 DOI: 10.1007/s11914-024-00859-1] [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] [Accepted: 01/29/2024] [Indexed: 02/16/2024]
Abstract
PURPOSE OF REVIEW Interfacial tissue exists throughout the body at cartilage-to-bone (osteochondral interface) and tendon-to-bone (enthesis) interfaces. Healing of interfacial tissues is a current challenge in regenerative approaches because the interface plays a critical role in stabilizing and distributing the mechanical stress between soft tissues (e.g., cartilage and tendon) and bone. The purpose of this review is to identify new directions in the field of interfacial tissue development and physiology that can guide future regenerative strategies for improving post-injury healing. RECENT FINDINGS Cues from interfacial tissue development may guide regeneration including biological cues such as cell phenotype and growth factor signaling; structural cues such as extracellular matrix (ECM) deposition, ECM, and cell alignment; and mechanical cues such as compression, tension, shear, and the stiffness of the cellular microenvironment. In this review, we explore new discoveries in the field of interfacial biology related to ECM remodeling, cellular metabolism, and fate. Based on emergent findings across multiple disciplines, we lay out a framework for future innovations in the design of engineered strategies for interface regeneration. Many of the key mechanisms essential for interfacial tissue development and adaptation have high potential for improving outcomes in the clinic.
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Affiliation(s)
- Stephanie S Steltzer
- Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Adam C Abraham
- Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Megan L Killian
- Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA.
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA.
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Clayton SW, Walk RE, Mpofu L, Easson GW, Tang SY. Analysis of Infiltrating Immune Cells Following Intervertebral Disc Injury Reveals Recruitment of Gamma-Delta ( γδ) T cells in Female Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.01.582950. [PMID: 38464124 PMCID: PMC10925253 DOI: 10.1101/2024.03.01.582950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Inadequate repair of injured intervertebral discs (IVD) leads to degeneration and contributes to low back pain. Infiltrating immune cells into damaged musculoskeletal tissues are critical mediators of repair, yet little is known about their identities, roles, and temporal regulation following IVD injury. By analyzing longitudinal changes in gene expression, tissue morphology, and the dynamics of infiltrating immune cells following injury, we characterize sex-specific differences in immune cell populations and identify the involvement of previously unreported immune cell types, γδ and NKT cells. Cd3+Cd4-Cd8- T cells are the largest infiltrating lymphocyte population with injury, and we identified the presence of γδ T cells in this population in female mice specifically, and NKT cells in males. Injury-mediated IVD degeneration was prevalent in both sexes, but more severe in males. Sex-specific degeneration may be associated with the differential immune response since γδ T cells have potent anti-inflammatory roles and may mediate IVD repair.
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Affiliation(s)
| | - Remy E. Walk
- Washington University in St. Louis, St. Louis, MO
| | - Laura Mpofu
- Washington University in St. Louis, St. Louis, MO
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Darrieutort-Laffite C, Blanchard F, Soslowsky LJ, Le Goff B. Biology and physiology of tendon healing. Joint Bone Spine 2024; 91:105696. [PMID: 38307405 DOI: 10.1016/j.jbspin.2024.105696] [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: 12/04/2023] [Revised: 01/11/2024] [Accepted: 01/23/2024] [Indexed: 02/04/2024]
Abstract
Tendon disorders affect people of all ages, from elite and recreational athletes and workers to elderly patients. After an acute injury, 3 successive phases are described to achieve healing: an inflammatory phase followed by a proliferative phase, and finally by a remodeling phase. Despite this process, healed tendon fails to recover its original mechanical properties. In this review, we proposed to describe the key factors involved in the process such as cells, transcription factors, extracellular matrix components, cytokines and growth factors and vascularization among others. A better understanding of this healing process could help provide new therapeutic approaches to improve patients' recovery while tendon disorders management remains a medical challenge.
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Affiliation(s)
- Christelle Darrieutort-Laffite
- Service de rhumatologie, CHU de Nantes, Nantes, France; Oniris, Regenerative Medicine and Skeleton, RMeS, UMR 1229, Inserm, CHU de Nantes, Nantes université, 44000 Nantes, France.
| | - Frédéric Blanchard
- Oniris, Regenerative Medicine and Skeleton, RMeS, UMR 1229, Inserm, CHU de Nantes, Nantes université, 44000 Nantes, France
| | - Louis J Soslowsky
- Department of Orthopaedic Surgery, McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA
| | - Benoit Le Goff
- Service de rhumatologie, CHU de Nantes, Nantes, France; Oniris, Regenerative Medicine and Skeleton, RMeS, UMR 1229, Inserm, CHU de Nantes, Nantes université, 44000 Nantes, France
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Koch DW, Schnabel LV. Mesenchymal stem cell licensing: enhancing MSC function as a translational approach for the treatment of tendon injury. Am J Vet Res 2023; 84:1-8. [PMID: 37669745 PMCID: PMC11027115 DOI: 10.2460/ajvr.23.07.0154] [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: 07/12/2023] [Accepted: 08/14/2023] [Indexed: 09/07/2023]
Abstract
Tendon injuries are common in both veterinary and human clinical patients and result in morbidity, pain, and lost athletic performance. Consequently, utilizing naturally occurring injuries in veterinary patients as a comparative model could inform the development of novel therapies and increase translation for the treatment of human tendon injuries. Mesenchymal stem cells (MSCs) have shown considerable efficacy for the treatment of experimental and clinical superficial digital flexor tendon injury in the horse; however, the reinjury rate following treatment can remain high and MSC efficacy in treating other tendons is less well known. Additionally, the translation of MSC therapy to human tendon injury has remained poor. Recent evidence indicates that naïve MSC function can be enhanced through exogenous stimulation or manipulation of their environment. This stimulation or activation, herein termed MSC licensing, markedly alters MSC functions associated with immunomodulation, extracellular matrix remodeling, vascular development, bioactive factor production, and endogenous stromal/progenitor cell support. Additionally, a variety of licensing strategies has proven to influence MSC-secreted factors that have positively influenced outcome parameters in both in vitro and in vivo disease models separate from musculoskeletal tissues. Therefore, identifying the optimal licensing strategy for MSCs could ultimately provide an avenue for reliable and repeatable treatment of a broad range of tendon injuries of both veterinary and human clinical patients. This article details current evidence on the effects of licensed MSCs in both in vitro and in vivo disease models of different species and provides commentary on how those effector functions identified may be translated to the treatment of tendon injuries.
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Affiliation(s)
- Drew W. Koch
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
- Comparative Medicine Institute, North Carolina State University, Raleigh, NC
| | - Lauren V. Schnabel
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC
- Comparative Medicine Institute, North Carolina State University, Raleigh, NC
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Baht GS, Grol MW. Editorial: The immune system and inflammation in musculoskeletal health, aging, and disease. Front Immunol 2023; 14:1218118. [PMID: 37275852 PMCID: PMC10233133 DOI: 10.3389/fimmu.2023.1218118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Accepted: 05/09/2023] [Indexed: 06/07/2023] Open
Affiliation(s)
- Gurpreet S. Baht
- Department of Orthopaedic Surgery, Duke Molecular Physiology Institute, Duke University, Durham, NC, United States
| | - Matthew W. Grol
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
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Bautista CA, Srikumar A, Tichy ED, Qian G, Jiang X, Qin L, Mourkioti F, Dyment NA. CD206+ tendon resident macrophages and their potential crosstalk with fibroblasts and the ECM during tendon growth and maturation. Front Physiol 2023; 14:1122348. [PMID: 36909235 PMCID: PMC9992419 DOI: 10.3389/fphys.2023.1122348] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 01/23/2023] [Indexed: 02/24/2023] Open
Abstract
Resident macrophages exist in a variety of tissues, including tendon, and play context-specific roles in their tissue of residence. In this study, we define the spatiotemporal distribution and phenotypic profile of tendon resident macrophages and their crosstalk with neighboring tendon fibroblasts and the extracellular matrix (ECM) during murine tendon development, growth, and homeostasis. Fluorescent imaging of cryosections revealed that F4/80+ tendon resident macrophages reside adjacent to Col1a1-CFP+ Scx-GFP+ fibroblasts within the tendon fascicle from embryonic development (E15.5) into adulthood (P56). Through flow cytometry and qPCR, we found that these tendon resident macrophages express several well-known macrophage markers, including Adgre1 (F4/80), Mrc1 (CD206), Lyve1, and Folr2, but not Ly-6C, and express the Csf1r-EGFP ("MacGreen") reporter. The proportion of Csf1r-EGFP+ resident macrophages in relation to the total cell number increases markedly during early postnatal growth, while the density of macrophages per mm2 remains constant during this same time frame. Interestingly, proliferation of resident macrophages is higher than adjacent fibroblasts, which likely contributes to this increase in macrophage proportion. The expression profile of tendon resident macrophages also changes with age, with increased pro-inflammatory and anti-inflammatory cytokine expression in P56 compared to P14 macrophages. In addition, the expression profile of limb tendon resident macrophages diverges from that of tail tendon resident macrophages, suggesting differential phenotypes across anatomically and functionally different tendons. As macrophages are known to communicate with adjacent fibroblasts in other tissues, we conducted ligand-receptor analysis and found potential two-way signaling between tendon fibroblasts and resident macrophages. Tendon fibroblasts express high levels of Csf1, which encodes macrophage colony stimulating factor (M-CSF) that acts on the CSF1 receptor (CSF1R) on macrophages. Importantly, Csf1r-expressing resident macrophages preferentially localize to Csf1-expressing fibroblasts, supporting the "nurturing scaffold" model for tendon macrophage patterning. Lastly, we found that tendon resident macrophages express high levels of ECM-related genes, including Mrc1 (mannose receptor), Lyve1 (hyaluronan receptor), Lair1 (type I collagen receptor), Ctss (elastase), and Mmp13 (collagenase), and internalize DQ Collagen in explant cultures. Overall, our study provides insights into the potential roles of tendon resident macrophages in regulating fibroblast phenotype and the ECM during tendon growth.
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Affiliation(s)
- Catherine A. Bautista
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
- Department of Bioengineering, School of Engineering and Applied Science, University of PA, Philadelphia, PA, United States
| | - Anjana Srikumar
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
| | - Elisia D. Tichy
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
| | - Grace Qian
- Department of Bioengineering, School of Engineering and Applied Science, University of PA, Philadelphia, PA, United States
| | - Xi Jiang
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
| | - Ling Qin
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
| | - Foteini Mourkioti
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of PA, Philadelphia, PA, United States
- Penn Institute for Regenerative Medicine, Musculoskeletal Program, Perelman School of Medicine, University of PA, Philadelphia, PA, United States
| | - Nathaniel A. Dyment
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of PA, Philadelphia, PA, United States
- Department of Bioengineering, School of Engineering and Applied Science, University of PA, Philadelphia, PA, United States
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Muscat S, Nichols AEC, Gira E, Loiselle AE. CCR2 is expressed by tendon resident macrophage and T cells, while CCR2 deficiency impairs tendon healing via blunted involvement of tendon-resident and circulating monocytes/macrophages. FASEB J 2022; 36:e22607. [PMID: 36250393 PMCID: PMC9593314 DOI: 10.1096/fj.202201162r] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 09/13/2022] [Accepted: 09/29/2022] [Indexed: 11/11/2022]
Abstract
During tendon healing, macrophages are thought to be a key mediator of scar tissue formation, which prevents successful functional restoration of the tendon. However, macrophages are critical for successful tendon healing as they aid in wound debridement, extracellular matrix deposition, and promote fibroblast proliferation. Recent work has sought to better define the multi-faceted functions of macrophages using depletion studies, while other studies have identified a tendon resident macrophage population. To begin to delineate the functions of tendon-resident versus circulation-derived macrophages, we examined the tendon healing phenotype in Chemokine Receptor 2 (CCR2) reporter (CCR2GFP/+ ), and knockout mice. CCR2 is a chemokine receptor primarily found on the surface of circulating bone marrow-derived monocytes, with CCR2 being an important mediator of macrophage recruitment to wound environments. Surprisingly, CCR2GFP/+ cells were present in the tendon during adult homeostasis, and single-cell RNA sequencing identified these cells as tendon-resident macrophages and T cells. During both homeostasis and healing, CCR2 knockout resulted in a substantial decrease in CCR2GFP+ cells and pan-macrophages. Additionally, loss of CCR2 resulted in reduced numbers of myofibroblasts and impeded functional recovery during late healing. This study highlights the heterogeneity of tendon-resident and recruited immune cells and their contributions following injury, and establishes an important role for CCR2 in modulating both the adult tendon cell environment and tendon healing process.
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Affiliation(s)
- Samantha Muscat
- Center for Musculoskeletal Research, Department of Orthopaedics & Rehabilitation, University of Rochester Medical Center, Rochester, New York, USA
| | - Anne E C Nichols
- Center for Musculoskeletal Research, Department of Orthopaedics & Rehabilitation, University of Rochester Medical Center, Rochester, New York, USA
| | - Emma Gira
- Center for Musculoskeletal Research, Department of Orthopaedics & Rehabilitation, University of Rochester Medical Center, Rochester, New York, USA
| | - Alayna E Loiselle
- Center for Musculoskeletal Research, Department of Orthopaedics & Rehabilitation, University of Rochester Medical Center, Rochester, New York, USA
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