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- Ben Amara, Heithem, 1984, et al.
(author)
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Immunomodulation by biodegradable Mg-implants promotes soft and hard tissues responses in vivo
- 2023
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In: Scandinavian Society of Biomaterials conference, 21–24 March 2023, Røros, Norway.
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Conference paper (other academic/artistic)abstract
- INTRODUCTION: Magnesium (Mg)-based degradable implants are an attractive treatment solution for musculoskeletal injuries, avoiding second-stage surgical removal. In multiple clinical applications, the implant is in contact with both the bone and the overlying soft tissue. Although Mg implants are often presented to hold anti-inflammatory properties, less attention has been paid to the sequential response to these implants including initial immune response and subsequent tissue repair. The present study investigated the molecular, cellular, and structural events taking place at the Mg implant interface to soft tissue and bone after in vivo implantation in dedicated experimental rat models. METHODS: Male Sprague Dawley rats received disc-shaped implants in the dorsum subcutis or screw-shaped implants in the proximal tibial metaphysis. Implants were manufactured from pure magnesium (99.99% - high purity; Mg) or from pure titanium (grade 4; Ti) as control. Animals were euthanized after 1, 3, 6, 14, and 28 day of soft tissue implantation, and after 3 and 28 days of bone implantation. Two types of samples were collected: 1-Implants with the adherent cells (n=7-8/group/time-point). These were allocated for cell counting and /or gene expression analyses of implant-adherent cells. 2-Peri-implant tissue with implants (n = 8/group/time-point). These enabled histological and histomorphometric analyses of the fibrous capsule organization around implants inserted in soft tissues and of osseointegration parameters at the bone-implant interface. Statistical comparisons between experimental groups were run using Kruskal-Wallis, and Mann-Whitney tests (p<0.05). RESULTS: Cells adherent to the surface of the implants featured different gene regulation patterns between Mg and Ti groups (Fig. 1). Consistently in soft tissue and in bone, macrophage polarization markers indicated higher expression of proinflammatory macrophage gene inducible nitric oxide synthase (iNos) initially at Mg versus Ti (3 d in bone and 1-6 d in soft tissue). Afterward, gene expression of both macrophage subtypes markers (proinflammatory – iNos and prohealing – Mannose receptor c1; Mrc1) was comparable between implants, irrespective of their insertion site. Histomorphometry evidenced superior bone-implant contact (at 28 d in bone) and thinner fibrous capsule (at 6-28 d in soft tissue) for Mg versus Ti. CONCLUSIONS: In comparison to non-degradable Ti, both soft tissue and bone responses to biodegradable Mg featured an initial yet transient gene activation of the macrophage proinflammatory subtype. Such immunomodulation by Mg resulted in the reduction of fibrous encapsulation in soft tissue and in the promotion of bone formation at the bone-implant interface. ACKNOWLEDGEMENTS: Mg implants were generously provided by Helmholtz-Zentrum Hereon, Geesthacht, Germany. This project is part of the European Training Network within the framework of Horizon 2020 Marie Skłodowska-Curie Action No 811226.
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| 2. |
- Ben Amara, Heithem, 1984, et al.
(author)
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Magnesium implant degradation provides immunomodulatory and proangiogenic effects and attenuates peri-implant fibrosis in soft tissues
- 2023
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In: Bioactive Materials. - : Elsevier BV. - 2452-199X. ; 26, s. 353-369
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Journal article (peer-reviewed)abstract
- Implants made of magnesium (Mg) are increasingly employed in patients to achieve osteosynthesis while degrading in situ. Since Mg implants and Mg2+ have been suggested to possess anti-inflammatory properties, the clinically observed soft tissue inflammation around Mg implants is enigmatic. Here, using a rat soft tissue model and a 1-28 d observation period, we determined the temporo-spatial cell distribution and behavior in relation to sequential changes of pure Mg implant surface properties and Mg2+ release. Compared to nondegradable titanium (Ti) implants, Mg degradation exacerbated initial inflammation. Release of Mg degradation products at the tissue-implant interface, culminating at 3 d, actively initiated chemotaxis and upregulated mRNA and protein immunomodulatory markers, particularly inducible nitric oxide synthase and toll-like receptor-4 up to 6 d, yet without a cytotoxic effect. Increased vascularization was demonstrated morphologically, preceded by high expression of vascular endothelial growth factor. The transition to appropriate tissue repair coincided with implant surface enrichment of Ca and P and reduced peri-implant Mg2+ concentration. Mg implants revealed a thinner fibrous encapsulation compared with Ti. The detailed understanding of the relationship between Mg material properties and the spatial and time-resolved cellular processes provides a basis for the interpretation of clinical observations and future tailoring of Mg implants.
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| 3. |
- Ben Amara, Heithem, 1984, et al.
(author)
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Promoting soft and hard tissue repair via immunomodulation by the surface degradation of magnesium implants in vivo
- 2023
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In: Materials for Tomorrow conference by Chalmers University of Technology, 8-10 November 2023, Gothenburg, Sweden.
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Conference paper (other academic/artistic)abstract
- INTRODUCTION: Magnesium (Mg) is a reactive metallic biomaterial that degrades via surface corrosion upon contact with body fluids. By virtue of its degradation and mechanical properties, Mg implants are currently employed with success to treat musculoskeletal injuries and avoid second-stage surgical removal 1. While these implants are claimed to possess anti-inflammatory properties, this notion contrasts with the initial signs of inflammation observed in the soft tissue of patients treated with Mg implants. This study investigated how the surface degradation of Mg implants in vivo influences the molecular, cellular, and structural events during initial inflammation and subsequent healing of the interfacing soft tissue and bone in comparison to nondegradable titanium (Ti) implants using experimental rat models. METHODS: Rats received disc-shaped implants in their dorsum subcutis or screw-shaped implants in the proximal metaphysis of their tibiae. Implants were manufactured from pure Mg (>99.995% - high purity) or from pure Ti (grade 4). Animals were euthanized after 1, 3, 6, 14, and 28 days of soft tissue implantation, and after 3 and 28 days of bone implantation. Two types of samples were collected: i) Implants only (n = 7-8/group/time-point): for counting and/or gene expression analyses of implant-adherent cells. ii) Implants with peri-implant tissues (n = 5-8/group/time-point): for compositional analysis of the Mg degradation layer in conjunction with the histomorphometry of the fibrous capsule around implants in soft tissues and of osseointegration at the bone–implant interface. Statistical comparisons were run using Kruskal-Wallis and Mann-Whitney tests (p<0.05). RESULTS: Cells adherent to the implant surfaces featured different gene regulation patterns between Mg and Ti groups (Fig. 1). Initially in soft tissue (1–6 d) and bone (3 d), a higher expression of proinflammatory macrophage polarization markers, e.g. inducible nitric oxide synthase (iNos), was shown in Mg versus Ti groups. Afterward, by 28 d, gene expression of both macrophage subtype markers (proinflammatory – iNos, and prohealing – Mannose receptor c1; Mrc1) was comparable between implants, irrespective of their insertion site. Histomorphometry revealed superior bone–implant contact (at 28 d in bone) and thinner fibrous capsule (at 6–28 d in soft tissue) for Mg versus Ti (Fig. 1). The 28 d-degradation layer at the Mg surface was enriched in Ca and P in both soft tissue and bone. CONCLUSIONS: In comparison to Ti implants, both soft tissue and bone responses to Mg implants featured an initial, amplified, yet transient, inflammation marked by the gene activation of the macrophage proinflammatory subtype. Such immunomodulation by the surface degradation of Mg implant promoted more bone deposition, at the bone–implant interface, and less fibrous encapsulation, at the soft tissue–implant interface. REFERENCES: 1. Han et al. Mater Today 2019, 23: 57-71. ACKNOWLEDGEMENTS: Horizon 2020 Marie Skłodowska-Curie Action (No 811226) and Area of Advance Materials/Chalmers and GU Biomaterials. Mg implants were generously provided by Hereon, Geesthacht, Germany.
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| 4. |
- Campbell, PJ, et al.
(author)
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Pan-cancer analysis of whole genomes
- 2020
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In: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 578:7793, s. 82-
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Journal article (peer-reviewed)abstract
- Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale1–3. Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4–5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter4; identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation5,6; analyses timings and patterns of tumour evolution7; describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity8,9; and evaluates a range of more-specialized features of cancer genomes8,10–18.
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| 5. |
- Gerner, Erik, 1986, et al.
(author)
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Targeting Pseudomonas aeruginosa quorum sensing with sodium salicylate modulates immune responses in vitro and in vivo.
- 2023
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In: Frontiers in cellular and infection microbiology. - 2235-2988. ; 13
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Journal article (peer-reviewed)abstract
- Chronic infections are a major clinical challenge in hard-to-heal wounds and implanted devices. Pseudomonas aeruginosa is a common causative pathogen that produces numerous virulence factors. Due to the increasing problem of antibiotic resistance, new alternative treatment strategies are needed. Quorum sensing (QS) is a bacterial communication system that regulates virulence and dampens inflammation, promoting bacterial survival. QS inhibition is a potent strategy to reduce bacterial virulence and alleviate the negative impact on host immune response.This study investigates how secreted factors from P. aeruginosa PAO1, cultured in the presence or absence of the QS inhibitor sodium salicylate (NaSa), influence host immune response.In vitro, THP-1 macrophages and neutrophil-like HL-60 cells were used. In vivo, discs of titanium were implanted in a subcutaneous rat model with local administration of P. aeruginosa culture supernatants. The host immune response to virulence factors contained in culture supernatants (+/-NaSa) was characterized through cell viability, migration, phagocytosis, gene expression, cytokine secretion, and histology.In vitro, P. aeruginosa supernatants from NaSa-containing cultures significantly increased THP-1 phagocytosis and HL-60 cell migration compared with untreated supernatants (-NaSa). Stimulation with NaSa-treated supernatants in vivo resulted in: (i) significantly increased immune cell infiltration and cell attachment to titanium discs; (ii) increased gene expression of IL-8, IL-10, ARG1, and iNOS, and (iii) increased GRO-α protein secretion and decreased IL-1β, IL-6, and IL-1α secretion, as compared with untreated supernatants.In conclusion, treating P. aeruginosa with NaSa reduces the production of virulence factors and modulates major immune events, such as promoting phagocytosis and cell migration, and decreasing the secretion of several pro-inflammatory cytokines.
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