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- Andersson, Marcus, 1975, et al.
(författare)
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Effect of molecular mobility of polymeric implants on soft tissue reactions: An in vivo study in rats
- 2008
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Ingår i: Journal of Biomedical Materials Research Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 84A:3, s. 652-660
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Tidskriftsartikel (refereegranskat)abstract
- Although numerous different polymers are used as implants or otherwise studied for many other biotechnical applications, there is a lack of basic models that correlate polymer characteristics with foreign body reactions. This study aims at developing one such model by systematically studying surface molecular mobility of polymeric implants in soft tissues in vivo. Changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs), provides an interesting opportunity to study the surface molecular mobility with minimal changes of the hydrophobicity of the surface. Thus, in this study three different PAMAs, with increasingly surface mobility; poly (isobutyl methacrylate) (PIBMA), poly(butyl methacrylate) (PBMA), and poly(lauryl methacralate) (PLMA) along with pure titanium (Ti) substrates were implanted in the dorsum of Sprague-Dawley rats. Inflammatory cell recruitment, cell adhesion, and cytokine release were studied after 1, 3, and 28 days of implantation. Total number of inflammatory cells in the exudate was measured but no correlation between surface mobility and cell recruitment where found. However, the number of surface associated cells where significantly lower on the surfaces with high molecular mobility (PLMA and PBMA). The histological evaluation performed after 28 days revealed thicker fibrous capsule and a higher number of blood vessels on the low molecular mobility surface (PIBMA). After 28 days the cell activity was higher on the high molecular mobility surfaces (PLMA and PBMA) compared with PIBMA, based on the cytokine release. None of the surfaces induced any significant cell-death. On the basis of the results of this study we conclude that there is a significant difference in biological response to surfaces with different in molecular mobility. This might affect the wound healing process and the biocompatibility of biomaterials. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007 -------------------------------------------------------------------------------- Received: 13 March 2006; Revised: 15 December 2006; Accepted: 29 January 2007 Digital Object Identifier (DOI) 10.1002/jbm.a.31389 About DOI
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- Omar, Omar, et al.
(författare)
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In vivo gene expression in response to anodically oxidized versus machined titanium implants.
- 2010
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Ingår i: Journal of biomedical materials research. Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 92:4, s. 1552-1566
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative polymerase chain reaction technique (qPCR) in combination with scanning electron microscopy was applied for the evaluation of early gene expression response and cellular reactions close to titanium implants. Anodically oxidized and machined titanium miniscrews were inserted in rat tibiae. After 1, 3, and 6 days the implants were unscrewed and the surrounding bone was retrieved using trephines. Both the implants and bone were analyzed with qPCR. A greater amount of cells, as indicated with higher expression of 18S, was detected on the oxidized surface after 1 and 6 days. Significantly higher osteocalcin (at day 6), alkaline phosphatase (at days 3 and 6), and cathepsin K (at day 3) expression was demonstrated for the oxidized surface. Higher expression of tumor necrosis factor-alpha (at day 1) and interleukin-1beta (at days 1 and 6) was detected on the machined surfaces. SEM revealed a higher amount of mesenchymal-like cells on the oxidized surface. The results show that the rapid recruitment of mesenchymal cells, the rapid triggering of gene expression crucial for bone remodeling and the transient nature of inflammation, constitute biological mechanisms for osseointegration, and high implant stability associated with anodically oxidized implants. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.
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- Omar, Omar, et al.
(författare)
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Integrin and chemokine receptor gene expression in implant-adherent cells during early osseointegration.
- 2010
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 1573-4838 .- 0957-4530. ; 21:3, s. 969-80
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms of early cellular recruitment and interaction to titanium implants are not well understood. The aim of this study was to investigate the expression of pro-inflammatory cytokines, chemokines and adhesion markers during the first 24 h of implantation. Anodically oxidized and machined titanium implants were inserted in rat tibia. After 3, 12, and 24 h the implants were unscrewed and analyzed with quantitative polymerase chain reaction. Immunohistochemistry and scanning electron microscopy revealed different cell types, morphology and adhesion at the two implant surfaces. A greater amount of cells, as indicated by higher expression of small subunit ribosomal RNA (18S), was detected on the oxidized surface. Higher expression of CXC chemokine receptor-4 (at 12 h) and integrins, alphav (at 12 h), beta1 (at 24 h) and beta2 (at 12 and 24 h) was detected at the oxidized surfaces. Significantly higher tumor necrosis factor-alpha (at 3 h) and interleukin-1beta (at 24 h) expression was demonstrated for the machined surface. It is concluded that material surface properties rapidly modulate the expression of receptors important for the recruitment and adhesion of cells which are crucial for the inflammatory and regenerative processes at implant surfaces in vivo.
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| 8. |
- Omar, Omar, et al.
(författare)
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Interfacial gene expression and stability of oxidized and machined titanium implants
- 2010
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Ingår i: European Association for Osseointegration 19th Annual Scientific Meeting, Glasgow, UK, 6-9 October, 2010.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In previous studies, combination of experimental model and gene expression analysis showed that from 3 hours to 6 days of implantation, significant differences in expression of genes denoting for cellular recruitment, inflammation, bone formation and bone resorption were seen at the interfaces of screw-shaped oxidized and machined titanium implants. It was concluded that the modulation of gene expression in favor of osteogenic differentiation and downregulation of the pro-inflammatory responses might explain the improved osseointegration of the oxidized implant surfaces. However, as a major condition, the developed bone-implant interface needs to be mechanically stable in order to fulfill the requirements of osseointegration The aim of the current study was to combine in vivo interfacial gene expression model with torque analysis in order to determine how molecular and cellular events taking place at the different titanium implants are related to the biomechanical properties of the interface. Anodically oxidized and machined titanium miniscrews were inserted in tibiae of 6 rats. Each rat received two oxidized implants in one tibia and two machined implants in the opposite tibia. After 28 days, the implants were removed using torque measuring equipment. The torque was registered and the implants completely removed and analyzed with quantitative polymerase chain reaction (n=12). Wilcoxon signed rank test was used to analyze the statistical differences of biomechanical and gene expression results between the two implant types. In addition, similar oxidized and machined titanium miniscrews were characterized topographically, chemically and ultrastructurally using profilometry, Auger electron microscopy and cross-sectioning electron microscopy, respectively. For chemical and topographical analyses, 3 implants from each type were analyzed. The measurements were made on flanks, tops, and valleys of two nonadjacent threads giving a total of 18 measurements for each implant type. Topographical comparisons were performed using one-way ANOVA followed by Bonferroni’s test. The biomechanical evaluation demonstrated 190% increase in torque values for the oxidized implants as compared to the machined ones. At the same time (28d), oxidized implants showed significantly higher expression of Runt-related transcription factor 1, osteocalcin, and tartrate resistant acid phosphatase. On the other hand higher expression of tumor necrosis factor-α and interleukin-1β was detected on the machined surfaces. Surface characterization procedures revealed major differences in the physico-chemical properties of the implant surfaces. In conclusion, the favorable cellular and molecular events at the oxidized implants were in parallel with significantly stronger bone anchorage during osseointegration
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- Omar, Omar, et al.
(författare)
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The correlation between gene expression of proinflammatory markers and bone formation during osseointegration with titanium implants
- 2011
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 32:2, s. 374-86
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Tidskriftsartikel (refereegranskat)abstract
- An in vivo interfacial gene expression model combined with biomechanical analysis was used in order to determine the relationship between the molecular events taking place during osseointegration and the biomechanical stability of the implant. Anodically oxidized and machined, threaded titanium implants were characterized topographically, chemically and ultrastructurally. The implants were inserted in rat tibiae and the implant bone torsion stability was evaluated. After measurements, the implants were removed and analyzed with qPCR. Results showed an increase in the breakpoint torque of 140%, 170% and 190%, after 6, 14, and 28 days, respectively, at the oxidized implants as compared to the machined. Gene expression analysis revealed higher expression of runt related transcription factor-2 (Runx2) (after 28 d), osteocalcin (OC) and tartrate resistant acid phosphatase (TRAP) (after 6, 14 and 28 d) and cathepsin K (CATK) (after 6 and 14 d) at the oxidized implants. On the other hand, machined implants were associated with higher expression of tumor necrosis factor-α (TNF-α) (after 6 and 28 d) and interleukin-1β (IL-1β) (after 6, 14 and 28 d) compared to the oxidized implants. In conclusion, the favorable cellular and molecular events at the oxidized implants were in parallel with significantly stronger bone anchorage during osseointegration.
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