Biomedical subjects

P Thomsen

Publications and source records attributed to P Thomsen.

At least 19 recordsLinked to original sources

PubMed2006

A novel tool for high-resolution transmission electron microscopy of intact interfaces between bone and metallic implants.

A key feature in the understanding of the mechanisms of integration versus rejection of implanted materials is a deepened understanding of the elemental and molecular compositions of the interface zone between the surface of the synthetic man-made material and the biological components of tissue. Intact interfaces between metallic implants and tissues have not been able to image and analyse on the ultrastructural level with the common transmission electron microscopy (TEM) sample preparation techniques. By using focused ion beam microscopy for site-specific preparation of TEM samples, intact interfaces between metal implants and calcified tissue were imaged for the first time. The interface's elemental and crystallographic compositions were determined using energy dispersive X-ray mapping and electron diffraction. The developed technique fulfills a long-sought-for demand to correlate the surface properties of implanted metal prostheses with the fine structure and composition of preserved interfaces with tissues.

Animals↗

PubMed2005

Interventions for replacing missing teeth: different types of dental implants.

BACKGROUND: Dental implants are available in different materials, shapes and with different surface characteristics. In particular, numerous implant surface modifications have been developed for enhancing clinical performances. OBJECTIVES: To test the null hypothesis of no difference in clinical performance between various root-formed osseointegrated dental implant types. SEARCH STRATEGY: We searched the Cochrane Oral Health Group's Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. Handsearching included several dental journals. We checked the bibliographies of relevant clinical trials and review articles for studies outside the handsearched journals. We wrote to authors of the identified randomised controlled trials (RCTs), to more than 55 oral implant manufacturers; we used personal contacts and we asked on an internet discussion group in an attempt to identify unpublished or ongoing RCTs. No language restriction was applied. The last electronic search was conducted on 28 June 2004. SELECTION CRITERIA: All RCTs of oral implants comparing osseointegrated implants with different materials, shapes and surface properties having a follow up of at least 1 year. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted in duplicate and independently by two reviewers. Results were expressed as random effects models using weighted mean differences for continuous outcomes and relative risk for dichotomous outcomes with 95% confidence intervals. MAIN RESULTS: Thirty-one different RCTs were identified. Twelve of these RCTs, reporting results from a total of 512 patients, were suitable for inclusion in the review. Twelve different implant types were compared with a follow up ranging from 1 to 5 years. All implants were made in commercially pure titanium and had different shapes and surface preparations. On a 'per patient ' rather than 'per implant' basis no significant differences were observed between various implant types for implant failures. There were statistically significant differences for peri-implant bone level changes on intraoral radiographs in three comparisons in two trials. In one trial there was more bone loss only at 1 year for IMZ implants compared to Branemark (mean difference 0.60 mm; 95% CI 0.01 to 1.10) and to ITI implants (mean difference 0.50 mm; 95% CI 0.01 to 0.99). In the other trial Southern implants displayed more bone loss at 5 years than Steri-Oss implants (mean difference -0.35 mm; 95% CI -0.70 to -0.01). However this difference disappeared in the meta-analysis. More implants with rough surfaces were affected by perimplantitis (RR 0.80; 95% CI 0.67 to 0.96) meaning that turned implant surfaces had a 20% reduction in risk of being affected by perimplantitis over a 3-year period. AUTHORS' CONCLUSIONS: Based on the available results of RCTs, there is limited evidence showing that implants with relatively smooth (turned) surfaces are less prone to loose bone due to chronic infection (perimplantitis) than implants with rougher surfaces. On the other hand, there is no evidence showing that any particular type of dental implant has superior long-term success. These findings are based on a few RCTs, often at high risk of bias, with few participants and relatively short follow-up periods. More RCTs should be conducted, with follow up of at least 5 years including a sufficient number of patients to detect a true difference if any exists. Such trials should be reported according to the CONSORT recommendations (http://www.consort-statement.org/).

Dental Implantation, Endosseous↗

PubMed2004

Micro patterning of cell and protein non-adhesive plasma polymerized coatings for biochip applications.

Micro scale patterning of bioactive surfaces is desirable for numerous biochip applications. Polyethyleneoxide-like (PEO-like) coating with non-fouling functionality has been deposited using low frequency AC plasma polymerization. The non-fouling properties of the coating were tested with human cells (HeLa) and fluorescence labeled proteins (isothiocyanate-labeled bovine serum albumin, i.e. FITC-BSA). The PEO-like coatings were fabricated by plasma polymerization of 12-crown-4 (ppCrown) with plasma polymerized hexene (ppHexene) as adhesion layer. The coatings were micro patterned using conventional cleanroom photolithography and lift-off. Single cell arrays showed sharp contrast in cell adhesion between the untreated glass surface and the ppCrown layer. Similarly, proteins adsorbed selectively to untreated glass but not to ppCrown. The simplicity of the lift-off technique and the sturdiness and versatility of the plasma-polymerized coatings, make this technology highly suitable for bio-MEMS and biochip applications, where patterned high contrast non-fouling surfaces are needed.

Adsorption↗

PubMed2004

Interventions for replacing missing teeth: maintaining health around dental implants.

BACKGROUND: To maintain healthy tissues around dental implants it is important to institute an effective preventive regimen (supportive therapy). Different maintenance regimens have been suggested, however it is unclear which are the most effective. OBJECTIVES: To test the null hypothesis of no difference between different interventions for maintaining healthy tissues around dental implants. SEARCH STRATEGY: We searched the Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. Handsearching included several dental journals. We checked the bibliographies of the identified randomised controlled trials (RCTs) and relevant review articles for studies outside the handsearched journals. We wrote to authors of all identified RCTs, to more than 55 oral implant manufacturers and an internet discussion group to find unpublished or ongoing RCTs. No language restrictions were applied. The last electronic search was conducted on 2 February 2004. SELECTION CRITERIA: All randomised controlled trials of oral implants comparing agents or interventions for maintaining or recovering healthy tissues around dental implants. DATA COLLECTION AND ANALYSIS: We carried out a quality assessment of the included RCTs in duplicate and contacted the authors for missing information. We independently extracted the data in duplicate. We followed the Cochrane Oral Health Group's statistical guidelines. MAIN RESULTS: Fourteen RCTs were identified. Five of these trials, which reported results from a total of 127 patients, were suitable for inclusion in the review. Two trials evaluated the efficacy of powered and sonic toothbrushes, respectively, when compared to manual toothbrushing and showed no statistically significant differences. One RCT compared Listerine versus placebo mouthwashes showing a reduction of 54% in plaque and 34% in marginal bleeding compared with the placebo. One trial compared self administered subgingival chlorhexidine irrigation versus chlorhexidine mouthwash. The group using chlorhexidine irrigation resulted in statistically significantly lower mean plaque scores and a marginal bleeding index than the group using chlorhexidine mouthwash, however the mouthwash was given at a suboptimal dosage. One study compared etching gel with mechanical debridement showing no statistical differences. Follow ups ranged between 6 weeks and 5 months. It was not possible to make any meta-analysis as each trial assessed different interventions. REVIEWERS' CONCLUSIONS: There is only little reliable evidence for which are the most effective interventions for maintaining health around peri-implant tissues. There was no evidence that the use of powered or sonic toothbrushes was superior to manual toothbrushing. There is weak evidence that Listerine mouthwash, used twice a day for 30 seconds, as adjunct to routine oral hygiene is effective in reducing plaque formation and marginal bleeding around implants. There was no evidence that phosphoric etching gel offered any clinical advantage over mechanical debridement. These findings are based on RCTs having short follow-up periods and few subjects. There is not any reliable evidence for the most effective regimens for long term maintenance. More RCTs should be conducted in this area. In particular, there is a definite need for trials powered to find possible differences, using primary outcome measures and with much longer follow up. Such trials should be reported according the CONSORT guidelines (http://www.consort-statement.org/).

Dental Implants↗

PubMed2004

Interventions for replacing missing teeth: different times for loading dental implants.

BACKGROUND: To minimize the risk of implant failure, osseointegrated oral implants are conventionally kept load-free during the healing period. During healing removable prostheses are used, however many patients find these temporary prostheses rather uncomfortable and it would be beneficial if the healing period could be shortened without jeopardizing implant success. Nowadays immediate and early loaded implants are commonly used in mandibles of good bone quality. It would be useful to know whether there is a difference in success rates between immediately or early loaded implants compared with conventionally loaded implants. OBJECTIVES: To test the null hypothesis of no difference in the clinical performance between osseointegrated implants loaded at different times 1 year after loading. SEARCH STRATEGY: The Cochrane Oral Health Group's Trials Register, The Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE were searched. Handsearching included several dental journals. Authors of all identified trials, an internet discussion group and 55 oral implant manufacturers were contacted to find unpublished randomized controlled trials (RCTs). The last electronic search was conducted on 2 February 2004. SELECTION CRITERIA: All RCTs of root-form osseointegrated oral implants having a follow up of at least 1 year comparing the same osseointegrated root-form oral implants loaded at different times. DATA COLLECTION AND ANALYSIS: Data were independently extracted, in duplicate, by two reviewers. Authors were contacted for details of randomization and withdrawals and a quality assessment was carried out. The Cochrane Oral Health Group's statistical guidelines were followed. MAIN RESULTS: Seven RCTs were identified and five trials including 124 patients in total were suitable for inclusion. Implants have been either immediately loaded after insertion (2 to 3 days), early loaded (6 weeks) or conventionally loaded (3 to 8 months) in edentulous mandibles of adequate bone quality and shape. On a patient, rather than per implant basis, there were no statistically significant differences for prosthesis failures, implant failures and marginal bone loss on intra-oral radiographs. REVIEWERS' CONCLUSIONS: While it is possible to successfully load oral implants immediately after their placement in mandibles of adequate bone density and height of carefully selected patients, it is yet unknown how predictable this approach is. More well designed RCTs are needed to understand how predictable immediate and early loading are. Such trials should be simply designed and should be reported according to the CONSORT guidelines (http://www.consort-statement.org/). It is suggested that priority should be given to trials assessing the effectiveness of immediately loaded implants rather than early loaded ones.

Bone Density↗

PubMed2003

Interventions for replacing missing teeth: dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous maxilla.

BACKGROUND: Dental implants are used for replacing missing teeth. However, the possibility of placing dental implants is limited by the presence of adequate bone volume permitting their anchorage. Several bone grafting procedures have been developed to solve this problem. The missing bone can be taken from a donor site, transplanted where needed and then implants are placed. Major bone grafting operations have to be undertaken under general anaesthesia and patients have to be hospitalized for a few days. Some degree of morbidity related to the donor site must be expected and two to three surgical interventions are needed before the implants can be functionally used. Often patients have to wait more than 1 year before a denture can be fixed to the implants and the total cost of the treatment is high. However, the major problem is that about 25% of the implants placed in grafted bone fail. Zygomatic implants are long screw-shaped implants developed as an alternative to bone grafting. Zygomatic implants are inserted into the body of the zygomatic bone. Their main advantages are that bone grafting may not be needed and patients may be fitted with a fixed denture much sooner. OBJECTIVES: To test the hypothesis of no difference in outcomes between zygomatic implants without bone augmenting procedures in comparison with conventional dental implants in augmented bone for severely resorbed maxillae. SEARCH STRATEGY: We searched the Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. We handsearched several dental journals. No language restrictions were applied. Personal contacts and manufacturers of dental implants were contacted to identify unpublished trials. Most recent search: February 2003. SELECTION CRITERIA: Randomised controlled clinical trials (RCTs) on patients with severely resorbed maxillae who could not be rehabilitated with conventional dental implants, treated with zygomatic implants without bone grafts versus conventional dental implants with bone grafts or other procedures for bone augmentation with a follow up of at least 1 year. Outcome measures considered were: prosthesis and implant failures, side effects, patient satisfaction and cost effectiveness. DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were to be conducted in duplicate and independently by two reviewers. Results were to be expressed as random effects models using weighted mean differences for continuous outcomes and relative risk for dichotomous outcomes with 95% confidence interval. Heterogeneity was to be investigated including both clinical and methodological factors. MAIN RESULTS: No RCTs or controlled clinical trials (CCTs) were identified. REVIEWER'S CONCLUSIONS: There is an urgent need for RCTs in this area, since zygomatic implants, if found to be at least as effective as other augmentation procedures, may involve major advantages for both patients and society.

Alveolar Ridge Augmentation↗

PubMed2003

Antibiotics to prevent complications following dental implant treatment.

BACKGROUND: Some dental implant failures may be due to bacterial contamination at implant insertion. Infections around biomaterials are difficult to treat and almost all infected implants have to be removed. In general, antibiotic prophylaxis in surgery is only indicated for patients at risk of infectious endocarditis, for patients with reduced host-response, when surgery is performed in infected sites, in cases of extensive and prolonged surgical interventions and when large foreign materials are implanted. To minimise infections after dental implant placement various prophylactic systemic antibiotic regimens have been suggested. More recent protocols recommended short term prophylaxis, if antibiotics have to be used. With the administration of antibiotics adverse events may occur, ranging from diarrhoea to life-threatening allergic reactions. Another major concern associated with the widespread use of antibiotics is the selection of antibiotic-resistant bacteria. The use of antibiotics in implant dentistry is controversial. It would be useful to know whether prophylactic antibiotics are effective in reducing failures of dental implants. OBJECTIVES: To assess the beneficial or harmful effects of the administration of prophylactic antibiotics for dental implant placement versus no antibiotic/placebo administration and if antibiotics are of benefit, to find which type, dosage and duration is the most effective. SEARCH STRATEGY: We searched the Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. We handsearched several dental journals. No language restrictions were applied. Personal contacts and manufacturers of dental implants were contacted to identify unpublished trials. Most recent search: March 2003. SELECTION CRITERIA: Randomised controlled clinical trials (RCTs) with a follow up of at least 3 months comparing the administration of various prophylactic antibiotics regimens and no antibiotics/placebo to patients undergoing dental implant placement. Outcome measures were prosthesis failures, implant failures, postoperative infections and adverse events (gastrointestinal, hypersensitivity). DATA COLLECTION AND ANALYSIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were to be conducted in duplicate and independently by two reviewers. Results were to be expressed as random effects models using weighted mean differences for continuous outcomes and relative risk for dichotomous outcomes with 95% confidence interval. Heterogeneity was to be investigated including both clinical and methodological factors. MAIN RESULTS: No RCTs were identified. REVIEWER'S CONCLUSIONS: There is not appropriate scientific evidence to recommend or discourage the use of prophylactic systemic antibiotics to prevent complications and failures of dental implants. Even though the present review did not assess the effectiveness of prophylactic antibiotics for patients at risk for endocarditis, it seems sensible to recommend the use of prophylactic antibiotics for patients at high and moderate risk for endocarditis, with immunodeficiencies, metabolic diseases, irradiated in the head and neck area and when an extensive or prolonged surgery is anticipated.

Antibiotic Prophylaxis↗

PubMed2003

IL-1alpha, IL-1beta and TNF-alpha secretion during in vivo/ex vivo cellular interactions with titanium and copper.

Titanium (Ti) and copper (Cu) were used to evaluate cytokine secretion around materials with different chemical properties. Ti disks were coated with Cu or left uncoated. The disks were inserted subcutaneously in rats for 1, 3, 12, 18, 24 and 48 h. Interleukin-1alpha (IL-1alpha), IL-1beta and tumor necrosis factor-alpha (TNF-alpha) concentrations were measured in vivo around the materials, in sham operated sites, and after ex vivo incubation of surface adherent cells. Ti and Cu revealed distinct cytokine expression patterns. Cu recruited cells showed higher and prolonged release of IL-1alpha than Ti at longer times (>24 h), whereas Ti exhibited a transient IL-1alpha response at earlier periods (<24 h). An early enhanced secretion of TNF-alpha characterized Ti. Low amounts of IL-1beta were found around both materials. Sham site recruited cells produced lower levels of cytokines. The results after ex vivo incubations were similar to those in vivo. This study shows that material chemical properties influence early cytokine production. The Ti-associated transient rise of IL-1alpha and TNF-alpha may be of importance for the early tissue response around biocompatible materials, while a delayed high IL-1alpha expression could be a marker of inflammation induced by toxic materials.

Animals↗

PubMed2003

Adhesion, apoptosis and cytokine release of human mononuclear cells cultured on degradable poly(urethane urea), polystyrene and titanium in vitro.

Early interactions between materials and mononuclear cells may influence the viability and secretory response of the cells. Such effects may in turn influence the subsequent inflammatory and repair phases around the materials. In the present study, it was examined if mononuclear cells cultured in vitro either unstimulated or stimulated with lipopolysaccharide (LPS) (10ng/ml) revealed differences regarding cell viability and apoptosis. A major interest was to study the influence of different material properties on the parameters of the inflammatory response upon cell adhesion to materials with widely different surface chemical properties but similar surface topography: degradable poly(urethane urea) (PUUR), cell culture treated polystyrene (PS) surfaces, and commercially pure (c.p.) titanium (Ti). Finally, the secretion of the proinflammatory tumor necrosis factor-a (TNF-alpha) and the downregulating interleukin-10 (IL-10) cytokines was examined in the supernatants from 24h mononuclear cell cultures. No differences in cell viability as measured by lactate dehydrogenas (LDH) were observed between the three materials. The number of material-surface adherent cells was higher on PUUR than the more hydrophilic PS and Ti as judged by quantification of material surface-associated DNA, light microscopic morphological examination of DAPI-stained cells and SEM. LPS increased the number of adherent cells, irrespective of the type of material. The lowest number of apoptotic (annexin-V) and necrotic (propidium iodide) mononuclear cells was detected on PUUR. LPS decreased the number of both apoptotic and necrotic cells, irrespective of material. Low TNF-alpha levels were detected in unstimulated conditions, irrespective of material types. A significantly lower amount of TNF-alpha was found with unstimulated cells on PUUR than on Ti. A significantly higher IL-10 level was detected in unstimulated Ti cultures compared with PUUR and PS. Secretion of IL-10 was predominantly stimulated by LPS on PUUR and Ti. The data indicate that material-related differences are expressed in differences in cell adherence, apoptosis and cytokine secretion. Further, degradable PUUR has equal or less cell-activating properties than Ti and PS under in vitro conditions.

Absorbable Implants↗

PubMed2002

Interventions for replacing missing teeth: different types of dental implants.

BACKGROUND: Dental implants are available in different materials, shapes and with different surface characteristics. In particular, numerous implant surface modifications have been developed for enhancing clinical performances. OBJECTIVES: To test the null hypothesis of no difference in clinical performance between various root-formed osseointegrated implant types. SEARCH STRATEGY: The Cochrane Oral Health Group Specialised Trials Register, The Cochrane Controlled Trials Register, MEDLINE and EMBASE were searched. Hand searching included several dental journals. Bibliographies of relevant clinical trials and review articles were checked for studies outside the handsearched journals. In addition, authors of all identified trials and fifty-five oral implant manufacturers were contacted to find unpublished or ongoing RCTs. Two extensive personal libraries (ME and AJ) were consulted. The last electronic search was conducted 8th May 2002. SELECTION CRITERIA: All randomised controlled trials of oral implants comparing implants with different materials, shapes and surface properties having a follow-up of at least one year. DATA COLLECTION AND ANALYSIS: Data were independently extracted, in duplicate, by two reviewers (ME & HW). Authors were contacted for details of randomisation and withdrawals and a quality assessment was carried out. The Cochrane Oral Health Group's statistical guidelines were followed. MAIN RESULTS: Thirty publications, representing 13 different RCTs, were identified. Five of these RCTs (seven publications), which reported results from a total of 326 patients, were suitable for inclusion in the review. Six implant systems were compared: Astra, Branemark, IMZ, ITI, Steri-Oss and Southern with a follow-up ranging from one to three years. All implants were made in commercially pure titanium and had different shapes and surface preparations. On a patient rather than per implant basis there were no statistically significant differences for failures and marginal bone level changes on intra-oral radiographs between various implant systems. REVIEWER'S CONCLUSIONS: There was no evidence that any of the implant systems evaluated was superior to the other. However, these findings are based on a few RCTs all having short follow-up periods and few participants. More RCTs should be conducted, with follow-up of at least five years and including a sufficient number of patients, to detect a true difference if any exists. Such trials should be reported according to the CONSORT guidelines (http://www.consort-statement.org/).

Dental Implantation, Endosseous↗

PubMed2002

Apoptosis and cytokine release in human monocytes cultured on polystyrene and fibrinogen-coated polystyrene surfaces.

The effects of polystyrene (PS) material surface preadsorption with fibrinogen (3 mg/ml) and a low concentration of lipopolysaccharide (LPS; 10 ng/ml) and polystyrene particles (PS; 10(5)/ml) on human monocyte adhesion, viability and cytokine release were studied during 24h culture in vitro. LPS caused an upregulation of CD14 in adherent cells. In comparison with unstimulated cells on uncoated polystyrene surfaces, LPS did not alter the number of adherent cells but caused a markedly increased release of the proinflammatory cytokines (IL-1alpha and TNF-alpha) and the down-regulating IL-10. The expression of indicators of various stages of cell death, TdT, annexin-V, propidium iodide (PI) and lactate dehydrogenase (LDH), were unaltered, decreased, decreased and increased, respectively, after LPS stimulation. PS particles (3 microm psi) caused an increased DNA fragmentation but had a reduced proportion of annexin-V and PI positive cells in comparison with unstimulated cells on uncoated PS. In contrast, 1microm psi particles had a similar proportion of TdT, annexin-V and PI expressing cells as unstimulated controls. Cultures stimulated with particles (irrespective of size), had a similar concentration of proinflammatory cytokines as unstimulated controls, whereas a higher level of IL-10 was detected. Precoating of PS with fibrinogen revealed an enhanced cell adhesion and a concomitant reduction of CD14 expression. irrespective of stimulation with various agonists. The proportions of TdT, annexin-V and PI positive cells were unaltered or reduced on fibrinogen-coated PS in both unstimulated and agonist-challenged cultures. However, depending on the presence and type of agonist, fibrinogen mediated either a markedly increased (LPS) or equivalent (particles and unstimulated) IL-1alpha and TNFalpha release. Further, in comparison with uncoated substrates, fibrinogen was associated with a reduction of IL-10 release, irrespective of the type of stimuli. These observations, using low concentrations of bacterial and material products, indicate that fibrinogen modulates cell material interactions and up- and down-regulates specific events depending on the nature/ type of immediate stimuli.

Annexin A5↗

PubMed2002

H2O2 production by cells on titanium and polystyrene surfaces using an in vivo model of exudate and surface related cell function.

The determination of secreted levels of reactive oxygen species by implant-adherent cells in vivo is required for understanding of the role(s) of such reactive oxygen species for the tissue response around medical devices. A model with subcutaneous implants of c.p. titanium (Ti) or polystyrene (PS) (cell culture grade) inserted on the back of rats were used. Implants and associated cells were retrieved and assayed after 1, 3, 5, 7, 14, 21 and 28 days. Morphological analysis of exudate cells showed that polymorphonuclear leukocytes (PMN) predominated after one day whereas macrophages were predominant after three days. The number of implant-adherent cells, as reflected by measurement of DNA, decreased with time. Ultrastructural observations showed that macrophages were predominant cells in contact with the implant surface. Measurement of hydrogen peroxide (H(2)O(2)) secretion by implant-adherent cells during 40 min incubation ex vivo revealed a constitutive generation of 40-400 pmol H(2)O(2)/microg DNA, depending on implantation time. Stimulation with protein kinase C agonist phorbol myristate acetate (PMA) caused an increased H(2)O(2) generation by adherent cells at early (up to five days) but not later (7-28 days) time periods. No major differences between Ti and PS were observed. Taken together, these findings show that Ti and PS implant-adherent cells secrete H(2)O(2) under in vivo conditions. Further, a reduced capacity to mount an enhanced H(2)O(2) secretion upon stimulation was demonstrated at late time periods. The role of this mediator for biocompatibility remains to be established.

Journal Article↗

PubMed2001

In vitro study of monocyte viability during the initial adhesion to albumin- and fibrinogen-coated surfaces.

Surface adherent monocytes and macrophages play a central role in the inflammatory response to biomaterials. In the present study the adhesion, viability and apoptotic changes in material surface adherent monocytes during the first hours of cell-surface interactions in vitro were studied, using tissue culture polystyrene surfaces coated with human albumin and fibrinogen. Human peripheral blood monocytes were enriched by a two-step gradient centrifugation and resuspended (1 x 10(6)/ml) in RPMI with 10% fetal bovine serum. The cells were added to polystyrene surfaces coated with human fibrinogen or albumin and incubated in 37 degrees C (5% CO2, 100% humidity) for 30 min, 1, 2, 3 and 24 h. The adherent cells were stained for early apoptotic changes (exposed phosphatidylserine) and cell death using Annexin-V-fluorescein and propidium iodide staining, respectively. A bi-phasic adhesion was observed on the fibrinogen coated surface, having the highest number of adherent cells after 30 min and 24 h, while the cell number was markedly reduced after 1-3 h. The number of adherent cells on albumin was relatively low after all short time incubations but had reached a high level after 24 h. The number of adherent dead cells was highest after I h on both albumin (approximately 30%) and fibrinogen (approximately 15%). In the 24 h cultures, the viability of adherent cells was high on both surfaces (95-100%). Viable cells staining positive for early apoptotic changes could only be clearly observed on the albumin coated surface, after 30 min of cell-material surface interaction. Cell death, including apoptotic death, thus seems to play an important role during the initial interactions between monocytes and a foreign surface.

Albumins↗

PubMed2001

Tissue response to hafnium.

The aim of the present experimental study was to evaluate the tissue response to hafnium (Hf) a reactive metal closely related to titanium (Ti) and zirconium (Zr). Hf has not been previously evaluated as implant material in a biologic environment. In a first experiment, 21 machined Hf non-threaded implants (test) and 21 similar Ti implants (control) were inserted in the abdominal wall of 21 rats. Animals were sacrificed after 8 days (6 rats), 6 (7 rats) and 12 weeks (8 rats). In a second experiment, 18 rabbits received 18 Hf and 18 Ti threaded implants in their tibiae, one implant in each tibia. The rabbits were sacrificed after 6, 12 and 24 weeks (6 animals/time interval). The bulk metal of the abdominal wall implants, embedded together with the surrounding tissue, was electrolytically dissolved and semithin (1 microm) sections of the intact tissue-implant interface were evaluated by light microscopy (morphometry). Bone-implant contact and bone area within threads were evaluated in ground sections. In soft tissues, a fluid space containing predominantly monocytes/macrophages surrounded the abdominal implants at 8 days. At 6 and 12 weeks, a fibrous capsule, consisting of layers of macrophages and fibroblasts, surrounded the implants. Macrophages, including multinuclear giant cells, always formed the innermost layer in contact with the implant surface. No quantitative or qualitative difference in the tissue organization was detected between Ti and Hf implants. In rabbits, 6 weeks after insertion, the proximal two threads located within the cortical bone were filled with bone in contact with Hf and Ti. The distal threads contained bone marrow. After 12 and 24 weeks, mature bone was present in the proximal 3-4 implant threads. No statistically significant difference was found between Hf and Ti implants at any time periods. It is concluded that Hf is an interesting metal for biomedical applications in bone and soft tissue.

Journal Article↗

PubMed2000

The HPV16 E5 oncogene inhibits endocytic trafficking.

The small hydrophobic E5 protein of Human Papillomavirus type 16 (HPV16) binds to the 16-kDa subunit of the V-H+-ATPase. This binding has been suggested to interfere with acidification of late endocytic structures. We here used video microscopy, ratio imaging and confocal microscopy of living C127 fibroblasts to study the effects of E5. Various endocytic markers including the pH-sensitive probe DM-NERF coupled to dextran, TransFluoSpheres and TRITC-concanavalin A, were applied. In E5-transfected cells, none of these markers colocalized with the membrane permeable probe LysoTracker Red, which accumulates in acidic, late endocytic structures, or with a green fluorescent version of the small GTPase Rab7 labeling late endocytic structures. Importantly, however, late endocytic structures accumulating LysoTracker were still present in the E5-transfected cells. It is therefore concluded that HPV16 E5 perturbs trafficking from early to late endocytic structures rather than acidification.

Actins↗

PubMed2000

Co-culture of human monocytes and thyrocytes in bicameral chamber: monocyte-derived IL-1alpha impairs the thyroid epithelial barrier.

Pro-inflammatory cytokines are important mediators in tissue responses to a wide range of endogenous (e.g. autoantigens) and exogenous (e.g. infections, wounds, biomaterials) stimuli. The complex interactions taking place between different cell types in such processes are difficult to examine in vivo. Here we studied the effect of human monocytes on thyroid epithelial cells co-cultured in bicameral chambers. Freshly isolated monocytes (1x10(6)/ml) added to the basal compartment reduced the transepithelial resistance (from 300-600 to <100 Omega.cm(2)) and caused a disruption of the tight junctions in apically grown thyrocyte monolayers after co-culture for 24 h. The barrier function was further attenuated by monocytes exposed to lipopolysaccharide (10 microg/ml) or polystyrene microspheres (size: 3 microm; 1x10(7)/ml). Loss of transepithelial resistance was accompanied by release of interleukin 1alpha (maximally 550 pg/ml) from the monocytes. Conversely, the resistance remained high when co-cultures were simultaneously incubated with neutralizing anti-human interleukin 1alpha antibodies. The results show that the integrity of cultured thyroid epithelium is impaired by monocytes without requirement of direct cell-to-cell contact. This action, mediated by interleukin-1alpha, suggests a mechanism by which hidden (lumenal) autoantigens might be exposed to interstitial antigen-presenting cells in autoimmune thyroid disease. In perspective, the model provides a tool in which humoral and cell-cell dependent processes generated by bioactive agents and particulate materials, for instance, during the healing and repair of tissue around biomaterials and hybrid implants, can be selectively examined.

Antigen-Presenting Cells↗

PubMed2000

Secretion of IL-1 and H2O2 by human mononuclear cells in vitro.

The secretion of hydrogen peroxide (H2O2) and interleukin-1alpha (IL-1alpha) was evaluated during in vitro culturing of human monocytes. The oxidative metabolism and cytokine secretion were correlated to the cell distribution (number of surface-associated cells), the DNA content and their integrity, evaluated by lactate dehydrogenase (LDH) assay. The differentiation of cultured monocytes was determined by the expression of CD14, 27E10 and RM3/1. After 24 h cultivation, unstimulated cells had a low production of H2O2 and IL-1alpha. A four-fold increase in the production of H2O2 was detected with 5 and 10 microg/ml of lipopolysaccharide (LPS) and polystyrene (PS) particles. PS particles induced a concentration-dependent increase in IL-1alpha after 24 h. In contrast, cultivation for 48 h, did not result in any measurable production of H2O2, irrespective of the type of stimulus. A decreased viability of monocytes was shown after stimulation with PS particles in high concentrations. Our results indicate that the phenotype expression, adhesion, integrity and secretory pattern of human monocytes is dependent on the culture time and the type and concentration of stimulus.

Cell Adhesion↗

PubMed2000

The absence of reactive astrocytosis is indicative of a unique inflammatory process in Parkinson's disease.

Virtually any neurological disorder leads to activation of resident microglia and invasion of blood-borne macrophages, which are accompanied by an increase in number and change in phenotype of astrocytes, a phenomenon generally termed reactive astrocytosis. One of the functions attributed to activation of astrocytes is thought to involve restoration of tissue damage. Hitherto, the role of astrocytes in the inflammatory reaction occurring in Parkinson's disease has not received much attention. In the present study, we examined the inflammatory events in autopsies of the substantia nigra and putamen from Parkinson's disease patients using age-matched autopsies from normal patients as controls. In the substantia nigra, activation of microglia was consistently observed in all Parkinson's disease autopsies as verified from immunohistochemical detection of CR3/43 and ferritin. Activation of resident microglia was not observed in the putamen. No differences were observed between controls and Parkinson's disease autopsies from the substantia nigra and putamen, in terms of distribution, cellular density or cellular morphology of astrocytes stained for glial fibrillary acidic protein or metallothioneins I and II, the latter sharing high affinity for metal ions and known to be induced in reactive astrocytes, possibly to exert anti-oxidative effects. Together, these findings indicate that the inflammatory process in Parkinson's disease is characterized by activation of resident microglia without reactive astrocytosis, suggesting that the progressive loss of dopaminergic neurons in Parkinson's disease is an ongoing neurodegenerative process with a minimum of involvement of the surrounding nervous tissue. The absence of reactive astrocytosis in Parkinson's disease contrasts what follows in virtually any other neurological disorder and may indicate that the inflammatory process in Parkinson's disease is a unique phenomenon.

Aged↗