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Vanvelk N, de Mesy Bentley KL, Verhofstad MHJ, Metsemakers WJ, Moriarty TF, Siverino C. Development of an ex vivo model to study Staphylococcus aureus invasion of the osteocyte lacuno-canalicular network. J Orthop Res 2024. [PMID: 39380444 DOI: 10.1002/jor.25988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2024] [Revised: 09/08/2024] [Accepted: 09/18/2024] [Indexed: 10/10/2024]
Abstract
Staphylococcus aureus has multiple mechanisms to evade the host's immune system and antibiotic treatment. One such mechanism is the invasion of the osteocyte lacuno-canalicular network (OLCN), which may be particularly important in recurrence of infection after debridement and antibiotic therapy. The aim of this study was to develop an ex vivo model to facilitate further study of S. aureus invasion of the OLCN and early-stage testing of antibacterial strategies against bacteria in this niche. The diameter of the canaliculi of non-infected human, sheep, and mouse bones was measured microscopically on Schmorl's picrothionin stained sections, showing a large overlap in canalicular diameter. S. aureus successfully invaded the OLCN in all species in vitro as revealed by presence in osteocyte lacunae in Brown and Brenn-stained sections and by scanning electron microscopy. Murine bones were then selected for further experiments, and titanium pins with either a wild-type or ΔPBP4 mutant S. aureus USA300 were placed trans-cortically and incubated for 2 weeks in tryptic soy broth. Wild-type S. aureus readily invaded the osteocyte lacunae in mouse bones while the ΔPBP4 showed a significantly lower invasion of the OLCN (p = 0.0005). Bone specimens were then treated with gentamicin, sitafloxacin, R14 bacteriophages, or left untreated. Gentamicin (p = 0.0027) and sitafloxacin (p = 0.0280) significantly reduced the proportion of S. aureus-occupied lacunae, whilst bacteriophage treatment had no effect. This study shows that S. aureus is able to invade the OLCN in an ex vivo model. This ex vivo model can be used for future early-stage studies before proceeding to in vivo studies.
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Affiliation(s)
- Niels Vanvelk
- AO Research Institute Davos, Davos, Switzerland
- Trauma Research Unit, Department of Surgery, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Karen L de Mesy Bentley
- Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, New York, USA
- Center for Advanced Research Technology (CART), University of Rochester Medical Center Rochester, Rochester, New York, USA
| | - Michael H J Verhofstad
- Trauma Research Unit, Department of Surgery, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Willem-Jan Metsemakers
- Department of Trauma Surgery, University Hospitals Leuven, Leuven, Belgium
- Department of Development and Regeneration, KU Leuven-University of Leuven, Leuven, Belgium
| | - Thomas F Moriarty
- AO Research Institute Davos, Davos, Switzerland
- Center for Muskuloskeletal Infections (ZMSI), University Hospital Basel, Basel, Switzerland
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Zelmer AR, Yang D, Gunn NJ, Solomon LB, Nelson R, Kidd SP, Richter K, Atkins GJ. Osteomyelitis-relevant antibiotics at clinical concentrations show limited effectivity against acute and chronic intracellular S. aureus infections in osteocytes. Antimicrob Agents Chemother 2024; 68:e0080824. [PMID: 39194210 PMCID: PMC11459924 DOI: 10.1128/aac.00808-24] [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: 06/02/2024] [Accepted: 08/09/2024] [Indexed: 08/29/2024] Open
Abstract
Osteomyelitis caused by Staphylococcus aureus can involve the persistent infection of osteocytes. We sought to determine if current clinically utilized antibiotics were capable of clearing an intracellular osteocyte S. aureus infection. Rifampicin, vancomycin, levofloxacin, ofloxacin, amoxicillin, oxacillin, doxycycline, linezolid, gentamicin, and tigecycline were assessed for their minimum inhibitory concentration (MIC) and minimum bactericidal concentrations against 12 S. aureus strains, at pH 5.0 and 7.2 to mimic lysosomal and cytoplasmic environments, respectively. Those antibiotics whose bone estimated achievable concentration was commonly above their respective MIC for the strains tested were further assayed in a human osteocyte infection model under acute and chronic conditions. Osteocyte-like cells were treated at 1×, 4×, and 10× the MIC for 1 and 7 days following infection (acute model), or at 15 and 21 days of infection (chronic model). The intracellular effectivity of each antibiotic was measured in terms of CFU reduction, small colony variant formation, and bacterial mRNA expression change. Only rifampicin, levofloxacin, and linezolid reduced intracellular CFU numbers significantly in the acute model. Consistent with the transition to a non-culturable state, few if any CFU could be recovered from the chronic model. However, no treatment in either model reduced the quantity of bacterial mRNA or prevented non-culturable bacteria from returning to a culturable state. These findings indicate that S. aureus adapts phenotypically during intracellular infection of osteocytes, adopting a reversible quiescent state that is protected against antibiotics, even at 10× their MIC. Thus, new therapeutic approaches are necessary to cure S. aureus intracellular infections in osteomyelitis.
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Affiliation(s)
- Anja R. Zelmer
- Center for Orthopedic and Trauma Research, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia
| | - Dongqing Yang
- Center for Orthopedic and Trauma Research, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia
| | - Nicholas J. Gunn
- Center for Orthopedic and Trauma Research, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia
| | - L. Bogdan Solomon
- Center for Orthopedic and Trauma Research, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia
- Department of Orthopedics and Trauma, Royal Adelaide Hospital, Adelaide, Australia
| | - Renjy Nelson
- Department of Infectious Diseases, Central Adelaide Local Health Network, Adelaide, Australia
| | - Stephen P. Kidd
- Australian Center for Antimicrobial Resistance Ecology, University of Adelaide, Adelaide, Australia
- Research Center for Infectious Disease, School of Biological Science, University of Adelaide, Adelaide, Australia
| | - Katharina Richter
- Department of Surgery, Richter Lab, Basil Hetzel Institute for Translational Health Research, University of Adelaide, Adelaide, Australia
- Institute for Photonics and Advanced Sensing, University of Adelaide, Adelaide, Australia
| | - Gerald J. Atkins
- Center for Orthopedic and Trauma Research, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia
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Sun Q, Huynh K, Muratovic D, Gunn NJ, Zelmer AR, Solomon LB, Atkins GJ, Yang D. Rapid bacterial evaluation beyond the colony forming unit in osteomyelitis. eLife 2024; 13:RP93698. [PMID: 38910553 PMCID: PMC11196105 DOI: 10.7554/elife.93698] [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] [Indexed: 06/25/2024] Open
Abstract
Examination of bacteria/host cell interactions is important for understanding the aetiology of many infectious diseases. The colony forming unit (CFU) has been the standard for quantifying bacterial burden for the past century, however, this suffers from low sensitivity and is dependent on bacterial culturability in vitro. Our data demonstrate the discrepancy between the CFU and bacterial genome copy number in an osteomyelitis-relevant co-culture system and we confirm diagnosis and quantify bacterial load in clinical bone specimens. This study provides an improved workflow for the quantification of bacterial burden in such cases.
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Affiliation(s)
- Qi Sun
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
| | - Kimberley Huynh
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
| | - Dzenita Muratovic
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
| | - Nicholas J Gunn
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
| | - Anja R Zelmer
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
| | - Lucian Bogdan Solomon
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
- Department of Orthopaedics and Trauma, Royal Adelaide HospitalAdelaideAustralia
| | - Gerald J Atkins
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
| | - Dongqing Yang
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical Sciences, University of AdelaideAdelaideAustralia
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Gunn NJ, Kidd SP, Solomon LB, Yang D, Roscioli E, Atkins GJ. Staphylococcus aureus persistence in osteocytes: weathering the storm of antibiotics and autophagy/xenophagy. Front Cell Infect Microbiol 2024; 14:1403289. [PMID: 38915921 PMCID: PMC11194354 DOI: 10.3389/fcimb.2024.1403289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/17/2024] [Indexed: 06/26/2024] Open
Abstract
Staphylococcus aureus is a major causative pathogen of osteomyelitis. Intracellular infections of resident bone cells including osteocytes can persist despite gold-standard clinical intervention. The mechanisms by which intracellular S. aureus evades antibiotic therapy are unknown. In this study, we utilised an in vitro S. aureus infection model of human osteocytes to investigate whether antibiotic-mediated dysregulation of autophagy contributes to this phenomenon. Infected or non-infected osteocyte-like cells were exposed to combinations of rifampicin, vancomycin, and modulators of autophagy. Intracellular bacterial growth characteristics were assessed using colony-forming unit (CFU) analysis, viable bacterial DNA abundance, and the rate of escape into antibiotic-free medium, together with measures of autophagic flux. Rifampicin, alone or in combination with vancomycin, caused a rapid decrease in the culturability of intracellular bacteria, concomitant with stable or increased absolute bacterial DNA levels. Both antibiotics significantly inhibited autophagic flux. However, modulation of autophagic flux did not affect viable bacterial DNA levels. In summary, autophagy was shown to be a factor in the host-pathogen relationship in this model, as its modulation affected the growth state of intracellular S. aureus with respect to both their culturability and propensity to escape the intracellular niche. While rifampicin and vancomycin treatments moderately suppressed autophagic flux acutely, this did not explain the paradoxical response of antibiotic treatment in decreasing S. aureus culturability whilst failing to clear bacterial DNA and hence intracellular bacterial load. Thus, off-target effects of rifampicin and vancomycin on autophagic flux in osteocyte-like cells could not explain the persistent S. aureus infection in these cells.
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Affiliation(s)
- Nicholas J. Gunn
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Stephen P. Kidd
- Australian Centre for Antimicrobial Resistance Ecology, University of Adelaide, Adelaide, SA, Australia
- Research Centre for Infectious Disease, School of Biological Science, University of Adelaide, Adelaide, SA, Australia
| | - Lucian B. Solomon
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
- Department of Orthopaedics and Trauma, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Dongqing Yang
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Eugene Roscioli
- Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, SA, Australia
- Department of Medicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
- Centre for Cancer Biology, South Australia (SA) Pathology and University of South Australia, Adelaide, SA, Australia
| | - Gerald J. Atkins
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
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Subramaniam S, Joyce P, Ogunniyi AD, Dube A, Sampson SL, Lehr CM, Prestidge CA. Minimum Information for Conducting and Reporting In Vitro Intracellular Infection Assays. ACS Infect Dis 2024; 10:337-349. [PMID: 38295053 DOI: 10.1021/acsinfecdis.3c00613] [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] [Indexed: 02/02/2024]
Abstract
Bacterial pathogens are constantly evolving to outsmart the host immune system and antibiotics developed to eradicate them. One key strategy involves the ability of bacteria to survive and replicate within host cells, thereby causing intracellular infections. To address this unmet clinical need, researchers are adopting new approaches, such as the development of novel molecules that can penetrate host cells, thus exerting their antimicrobial activity intracellularly, or repurposing existing antibiotics using nanocarriers (i.e., nanoantibiotics) for site-specific delivery. However, inconsistency in information reported across published studies makes it challenging for scientific comparison and judgment of experiments for future direction by researchers. Together with the lack of reproducibility of experiments, these inconsistencies limit the translation of experimental results beyond pre-clinical evaluation. Minimum information guidelines have been instrumental in addressing such challenges in other fields of biomedical research. Guidelines and recommendations provided herein have been designed for researchers as essential parameters to be disclosed when publishing their methodology and results, divided into four main categories: (i) experimental design, (ii) establishing an in vitro model, (iii) assessment of efficacy of novel therapeutics, and (iv) statistical assessment. These guidelines have been designed with the intention to improve the reproducibility and rigor of future studies while enabling quantitative comparisons of published studies, ultimately facilitating translation of emerging antimicrobial technologies into clinically viable therapies that safely and effectively treat intracellular infections.
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Affiliation(s)
- Santhni Subramaniam
- UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia
| | - Paul Joyce
- UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia
| | - Abiodun D Ogunniyi
- Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Roseworthy, SA 5371, Australia
| | - Admire Dube
- School of Pharmacy, University of the Western Cape, Bellville, 7535 Cape Town, South Africa
| | - Samantha L Sampson
- South African Medical Research Council Centre for Tuberculosis Research, and Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, 7602 Cape Town, South Africa
| | - Claus-Michael Lehr
- Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Campus Building E 8.1, 66123 Saarbrücken, Germany
- Department of Pharmacy, Saarland University, Campus Building E8.1, 66123 Saarbrücken, Germany
| | - Clive A Prestidge
- UniSA Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia
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Liu S, Chen H, Xu F, Chen F, Yin Y, Zhang X, Tu S, Wang H. Unravelling staphylococcal small-colony variants in cardiac implantable electronic device infections: clinical characteristics, management, and genomic insights. Front Cell Infect Microbiol 2024; 13:1321626. [PMID: 38259974 PMCID: PMC10800868 DOI: 10.3389/fcimb.2023.1321626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Accepted: 12/11/2023] [Indexed: 01/24/2024] Open
Abstract
Objectives Staphylococcal small-colony variants (SCVs) are common in cardiac implantable electronic device (CIED) infections. This is the first retrospective and multi-case study on CIED infections due to staphylococcal SCVs, aiming to provide a theoretical basis for the clinical management of CIED and device-related infections caused by staphylococcal SCVs. Methods Ninety patients with culture positive CIED infections were enrolled between 2021 and 2022. We compared the demographic and clinical characteristics of patients with and without SCVs and performed genomic studies on SCVs isolates. Results Compared to patients without SCVs, those with SCVs had a longer primary pacemaker implantation time and were more likely to have a history of device replacement and infection. They showed upregulated inflammatory indicators, especially higher NEUT% (52.6 vs. 26.8%, P = 0.032) and they had longer hospital stays (median 13 vs. 12 days, P = 0.012). Comparative genomics analysis was performed on Staphylococcus epidermidis wild-type and SCVs. Some genes were identified, including aap, genes encoding adhesin, CHAP domain-containing protein, LPXTG cell wall anchor domain-containing protein, and YSIRK-type signal peptide-containing protein. Conclusion Staphylococcal SCVs affect the clinical characteristics of CIED infections. The process of staphylococcal SCVs adherence, biofilm formation, and interaction with neutrophils play a vital role.
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Affiliation(s)
- Si Liu
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
| | - Hongbin Chen
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
| | - Fangjie Xu
- Department of Clinical Laboratory, Urumqi Friendship Hospital, Urumqi, China
| | - Fengning Chen
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
| | - Yuyao Yin
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
| | - Xiaoyang Zhang
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
| | - Shangyu Tu
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
| | - Hui Wang
- Department of Clinical Laboratory, Peking University People’s Hospital, Beijing, China
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Zelmer AR, Starczak Y, Solomon LB, Richter K, Yang D, Atkins GJ. Saos-2 cells cultured under hypoxia rapidly differentiate to an osteocyte-like stage and support intracellular infection by Staphylococcus aureus. Physiol Rep 2023; 11:e15851. [PMID: 37929653 PMCID: PMC10626491 DOI: 10.14814/phy2.15851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/02/2023] [Accepted: 10/20/2023] [Indexed: 11/07/2023] Open
Abstract
The intracellular infection of osteocytes represents a clinically important aspect of osteomyelitis. However, few human osteocyte in vitro models exist and the differentiation of immature osteoblasts to an osteocyte stage typically takes at least 4-weeks of culture, making the study of this process challenging and time consuming. The osteosarcoma cell line Saos-2 has proved to be a useful model of human osteoblast to mature osteocyte differentiation. Culture under osteogenic conditions in a standard normoxic (21% O2 ) atmosphere results in reproducible mineralization and acquisition of mature osteocyte markers over the expected 28-35 day culture period. In order to expedite experimental assays, we tested whether reducing available oxygen to mimic concentrations experienced by osteocytes in vivo would increase the rate of differentiation. Cells cultured under 1% O2 exhibited maximal mineral deposition by 14 days. Early (COLA1, MEPE) and mature (PHEX, DMP1, GJA1, SOST) osteocyte markers were upregulated earlier under hypoxia compared to normoxia. Cells differentiated under 1% O2 for 14 days displayed a similar ability to internalize Staphylococcus aureus as day 28 cells grown under normoxic conditions. Thus, low oxygen accelerates Saos-2 osteocyte differentiation, resulting in a useful human osteocyte-like cell model within 14 days.
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Affiliation(s)
- Anja R. Zelmer
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical SciencesUniversity of AdelaideAdelaideSouth AustraliaAustralia
| | - Yolandi Starczak
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical SciencesUniversity of AdelaideAdelaideSouth AustraliaAustralia
| | - Lucian B. Solomon
- Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical SciencesUniversity of AdelaideAdelaideSouth AustraliaAustralia
- Department of Orthopaedics and TraumaRoyal Adelaide HospitalAdelaideSouth AustraliaAustralia
| | - Katharina Richter
- Richter Lab, Department of SurgeryBasil Hetzel Institute for Translational Health Research, University of AdelaideAdelaideSouth AustraliaAustralia
| | - Dongqing Yang
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical SciencesUniversity of AdelaideAdelaideSouth AustraliaAustralia
| | - Gerald J. Atkins
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic & Trauma Research, Faculty of Health and Medical SciencesUniversity of AdelaideAdelaideSouth AustraliaAustralia
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Heng BC, Bai Y, Li X, Lim LW, Li W, Ge Z, Zhang X, Deng X. Electroactive Biomaterials for Facilitating Bone Defect Repair under Pathological Conditions. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2204502. [PMID: 36453574 PMCID: PMC9839869 DOI: 10.1002/advs.202204502] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 10/24/2022] [Indexed: 06/02/2023]
Abstract
Bone degeneration associated with various diseases is increasing due to rapid aging, sedentary lifestyles, and unhealthy diets. Living bone tissue has bioelectric properties critical to bone remodeling, and bone degeneration under various pathological conditions results in significant changes to these bioelectric properties. There is growing interest in utilizing biomimetic electroactive biomaterials that recapitulate the natural electrophysiological microenvironment of healthy bone tissue to promote bone repair. This review first summarizes the etiology of degenerative bone conditions associated with various diseases such as type II diabetes, osteoporosis, periodontitis, osteoarthritis, rheumatoid arthritis, osteomyelitis, and metastatic osteolysis. Next, the diverse array of natural and synthetic electroactive biomaterials with therapeutic potential are discussed. Putative mechanistic pathways by which electroactive biomaterials can mitigate bone degeneration are critically examined, including the enhancement of osteogenesis and angiogenesis, suppression of inflammation and osteoclastogenesis, as well as their anti-bacterial effects. Finally, the limited research on utilization of electroactive biomaterials in the treatment of bone degeneration associated with the aforementioned diseases are examined. Previous studies have mostly focused on using electroactive biomaterials to treat bone traumatic injuries. It is hoped that this review will encourage more research efforts on the use of electroactive biomaterials for treating degenerative bone conditions.
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Affiliation(s)
- Boon Chin Heng
- Central LaboratoryPeking University School and Hospital of StomatologyBeijing100081P. R. China
- School of Medical and Life SciencesSunway UniversityDarul EhsanSelangor47500Malaysia
| | - Yunyang Bai
- Department of Geriatric DentistryPeking University School and Hospital of StomatologyBeijing100081P. R. China
| | - Xiaochan Li
- Department of Geriatric DentistryPeking University School and Hospital of StomatologyBeijing100081P. R. China
| | - Lee Wei Lim
- Neuromodulation LaboratorySchool of Biomedical SciencesLi Ka Shing Faculty of MedicineThe University of Hong KongPokfulamHong KongP. R. China
| | - Wang Li
- Department of Biomedical EngineeringPeking UniversityBeijing100871P. R. China
| | - Zigang Ge
- Department of Biomedical EngineeringPeking UniversityBeijing100871P. R. China
| | - Xuehui Zhang
- Department of Dental Materials & Dental Medical Devices Testing CenterPeking University School and Hospital of StomatologyBeijing100081P. R. China
- National Engineering Research Center of Oral Biomaterials and Digital Medical DevicesNMPA Key Laboratory for Dental MaterialsBeijing Laboratory of Biomedical Materials & Beijing Key Laboratory of Digital StomatologyPeking University School and Hospital of StomatologyBeijing100081P. R. China
| | - Xuliang Deng
- Department of Geriatric DentistryPeking University School and Hospital of StomatologyBeijing100081P. R. China
- Department of Dental Materials & Dental Medical Devices Testing CenterPeking University School and Hospital of StomatologyBeijing100081P. R. China
- National Engineering Research Center of Oral Biomaterials and Digital Medical DevicesNMPA Key Laboratory for Dental MaterialsBeijing Laboratory of Biomedical Materials & Beijing Key Laboratory of Digital StomatologyPeking University School and Hospital of StomatologyBeijing100081P. R. China
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Zelmer AR, Nelson R, Richter K, Atkins GJ. Can intracellular Staphylococcus aureus in osteomyelitis be treated using current antibiotics? A systematic review and narrative synthesis. Bone Res 2022; 10:53. [PMID: 35961964 PMCID: PMC9374758 DOI: 10.1038/s41413-022-00227-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/26/2022] [Accepted: 06/15/2022] [Indexed: 11/09/2022] Open
Abstract
Approximately 40% of treatments of chronic and recurrent osteomyelitis fail in part due to bacterial persistence. Staphylococcus aureus, the predominant pathogen in human osteomyelitis, is known to persist by phenotypic adaptation as small-colony variants (SCVs) and by formation of intracellular reservoirs, including those in major bone cell types, reducing susceptibility to antibiotics. Intracellular infections with S. aureus are difficult to treat; however, there are no evidence-based clinical guidelines addressing these infections in osteomyelitis. We conducted a systematic review of the literature to determine the demonstrated efficacy of all antibiotics against intracellular S. aureus relevant to osteomyelitis, including protein biosynthesis inhibitors (lincosamides, streptogramins, macrolides, oxazolidines, tetracyclines, fusidic acid, and aminoglycosides), enzyme inhibitors (fluoroquinolones and ansamycines), and cell wall inhibitors (beta-lactam inhibitors, glycopeptides, fosfomycin, and lipopeptides). The PubMed and Embase databases were screened for articles related to intracellular S. aureus infections that compared the effectiveness of multiple antibiotics or a single antibiotic together with another treatment, which resulted in 34 full-text articles fitting the inclusion criteria. The combined findings of these studies were largely inconclusive, most likely due to the plethora of methodologies utilized. Therefore, the reported findings in the context of the models employed and possible solutions for improved understanding are explored here. While rifampicin, oritavancin, linezolid, moxifloxacin and oxacillin were identified as the most effective potential intracellular treatments, the scientific evidence for these is still relatively weak. We advocate for more standardized research on determining the intracellular effectiveness of antibiotics in S. aureus osteomyelitis to improve treatments and patient outcomes.
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Affiliation(s)
- Anja R Zelmer
- Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, 5000, Australia
| | - Renjy Nelson
- Department of Infectious Diseases, Central Adelaide Local Health Network, Adelaide, SA, 5000, Australia.,Royal Adelaide Hospital, Adelaide, SA, 5000, Australia
| | - Katharina Richter
- Richter Lab, Department of Surgery, Basil Hetzel Institute for Translational Health Research, University of Adelaide, Adelaide, SA, 5011, Australia
| | - Gerald J Atkins
- Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, 5000, Australia.
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Garcia-Moreno M, Jordan PM, Günther K, Dau T, Fritzsch C, Vermes M, Schoppa A, Ignatius A, Wildemann B, Werz O, Löffler B, Tuchscherr L. Osteocytes Serve as a Reservoir for Intracellular Persisting Staphylococcus aureus Due to the Lack of Defense Mechanisms. Front Microbiol 2022; 13:937466. [PMID: 35935196 PMCID: PMC9355688 DOI: 10.3389/fmicb.2022.937466] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 06/20/2022] [Indexed: 11/24/2022] Open
Abstract
Chronic staphylococcal osteomyelitis can persist for long time periods causing bone destruction. The ability of Staphylococcus aureus to develop chronic infections is linked to its capacity to invade and replicate within osteoblasts and osteocytes and to switch to a dormant phenotype called small colony variants. Recently, osteocytes were described as a main reservoir for this pathogen in bone tissue. However, the mechanisms involved in the persistence of S. aureus within these cells are still unknown. Here, we investigated the interaction between S. aureus and osteoblasts or osteocytes during infection. While osteoblasts are able to induce a strong antimicrobial response and eliminate intracellular S. aureus, osteocytes trigger signals to recruit immune cells and enhance inflammation but fail an efficient antimicrobial activity to clear the bacterial infection. Moreover, we found that extracellular signals from osteocytes enhance intracellular bacterial clearance by osteoblasts. Even though both cell types express Toll-like receptor (TLR) 2, the main TLR responsible for S. aureus detection, only osteoblasts were able to increase TLR2 expression after infection. Additionally, proteomic analysis indicates that reduced intracellular bacterial killing activity in osteocytes is related to low antimicrobial peptide expression. Nevertheless, high levels of lipid mediators and cytokines were secreted by osteocytes, suggesting that they can contribute to inflammation. Taken together, our results demonstrate that osteocytes contribute to severe inflammation observed in osteomyelitis and represent the main niche for S. aureus persistence due to their poor capacity for intracellular antimicrobial response.
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Affiliation(s)
| | - Paul M. Jordan
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University Jena, Jena, Germany
| | - Kerstin Günther
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University Jena, Jena, Germany
| | - Therese Dau
- Leibniz Institute on Aging, Fritz Lipmann Institute, Jena, Germany
| | - Christian Fritzsch
- Institute of Medical Microbiology, Jena University Hospital, Jena, Germany
| | - Monika Vermes
- Institute of Medical Microbiology, Jena University Hospital, Jena, Germany
| | - Astrid Schoppa
- 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
| | - Britt Wildemann
- Experimental Trauma Surgery, Department of Trauma, Hand and Reconstructive Surgery, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
| | - Oliver Werz
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, Friedrich Schiller University Jena, Jena, Germany
| | - Bettina Löffler
- Institute of Medical Microbiology, Jena University Hospital, Jena, Germany
| | - Lorena Tuchscherr
- Institute of Medical Microbiology, Jena University Hospital, Jena, Germany
- *Correspondence: Lorena Tuchscherr,
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Kuehling T, Schilling P, Bernstein A, Mayr HO, Serr A, Wittmer A, Bohner M, Seidenstuecker M. A human bone infection organ model for biomaterial research. Acta Biomater 2022; 144:230-241. [PMID: 35304323 DOI: 10.1016/j.actbio.2022.03.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 03/03/2022] [Accepted: 03/09/2022] [Indexed: 02/07/2023]
Abstract
The aim of this work was to establish an organ model for staphylococcal infection of human bone samples and to investigate the influence and efficacy of a microporous β-tricalcium phosphate ceramic (β-TCP, RMS Foundation) loaded with hydrogels (alginate, alginate-di-aldehyde (ADA)-gelatin) and clindamycin on infected human bone tissue over a period of 28 days. For this purpose, human tibia plateaus, collected during total knee replacement surgery, were used as a source of bone material. Samples were infected with S. aureus ATCC29213 and treated with differently loaded β-TCP composites (alginate +/- clindamycin, ADA-gelatin +/- clindamycin, unloaded). The loading of the composites was carried out by means of a flow chamber. The infection was observed for 28 days, quantifying bacteria in the medium and the osseus material on day 1, 7, 14, 21 and 28. All samples were histologically processed for bone vitality evaluation. Bone infection could be consistently performed within the organ model. In addition, a strong reduction in bacterial counts was recorded in the groups treated with ADA-gelatin + clindamycin and alginate + clindamycin, while the bacterial count in the control groups remained constant. No significant differences between groups could be observed in the number of lacunae filled with osteocytes suggesting no differences in bone vitality among groups. In an ex-vivo human bone infection model, over a period of 28 days bacterial growth could be reduced by treatment with ADA-Gel + CLI and ALG + CLI -releasing β-TCP composites. This could be relevant for its clinical use. Further work will be necessary to improve the loading of β-TCP and the bone infection organ model itself. STATEMENT OF SIGNIFICANCE: The common treatment of bone infections is debridement and systemic administration of antibiotics. In some cases, antibiotic-containing carriers are already used, but these must be removed again. Our work is intended to show another treatment option. The scaffold we have developed, made of a calcium phosphate ceramic and a hydrogel as the active substance carrier, can, in addition to releasing the active substance, also assume a load-bearing function of the bone and is biodegradable. In addition, the model we developed can also be used for the analysis and treatment of bone infections other than those of the musculoskeletal system. More importantly, it can also serve as a substitute for previously used animal experiments.
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