[Cytokines of bone turnover in postmenopause and old age]

BACKGROUND

The aim of the study was the assessment of the influence of cytokines on bone ageing by measuring their level in serum and their secretion in vitro by monocytes from women of different age.

METHODS

The levels of cytokines in 34 postmenopausal subjects and 14 old subjects were compared to those measured in 13 cycling subjects who were considered as control group. Subjects suffering from diseases inducing secondary osteoporosis, subjects taking medications that affect bone metabolism and alcohol- or tobacco-consumers were excluded from the study. The levels in serum of (i) the bone stimulating peptide insulin-like growth factor-I (IGF-I), (ii) the inhibitor of bone resorption interferon-gamma (IFN gamma), (iii) the stimulators of bone resorption interleukin-1 beta (IL-1 beta) tumor necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6) were evaluated by immunoassay. IL-1 beta, TNF alpha and IL-6 secreted by monocytes (MO) cultured in vitro from peripheral blood of the same subjects were measured, too. Bacterial endotoxin (LPS) was used as stimulator for cytokine secretion by monocytes.

RESULTS

Unlike IFN gamma, which was unaltered, circulating IGF-I level was found significantly diminished in postmenopausal and old subjects compared to control group. Among stimulators of bone resorption, IL-6 was greatly increased in postmenopausal and old subjects, while TNF alpha was reduced in postmenopausal group. In the supernatants of unstimulated monocytes the level of IL-1 beta was consistently decreased in old subjects; TNF alpha was found to be decreased in postmenopausal and old subjects. The stimulation index (SI), calculated as the ratio between the level of cytokines secreted by LPS-stimulated MO and the level of cytokines secreted by unstimulated MO, was found to be significantly increased for IL-1 beta and TNF alpha in postmenopausal subjects vs control group. In the old subjects the SI for IL-6 was enhanced.

CONCLUSIONS

The data collected suggest that the measurement of cytokines in serum and supernatants from monocytes may give a picture of the mechanisms regulating bone aging.

Wear debris and cytokine production in the interface membrane of loosened prostheses

In this study, thirty-nine patients were examined. All of them suffered from hip joint prostheses loosening and underwent revision surgery. Bioptic samples were collected at the interface between bone and implant either at the stem or cotyle level. Immunohistochemistry was performed to detect IL-1alpha, IL-1beta, IL-6 and TNF, cytokines that directly cause bone resorption and indirectly induce synthesis of other bone resorbing cytokines. Quantitative analysis of the positive cells and correlation with clinical data was performed. It resulted that there is a great variability in positive cells for cytokines according to the harvest site; anyway, cytokines tend to be higher in patients carrying a joint prosthesis with polyethylene acetabular component and it is associated with plastic wear particles, even though there is no direct correlation between wear amount and cytokine levels. There is a statistically significant negative correlation between metal wear and a cytokine (IL-6); cytokines levels do not depend on the implant time to failure and do not correlate with pain score. As expected, cytokines levels tend to be lower in subjects being treated with non-steroidal antiinflammatory drugs. It can be concluded that plastic wear is the factor inducing the highest cytokine levels in the tissues around the prosthesis at the interface; cytokines that are an indicator of osteolysis risk.

Determination of ifosfamide by HPLC using on-line sample preparation

The Authors have developed a novel and easily applicable HPLC method for ifosfamide (IF) determination. This method involves on-line sample processing and its solid-phase extraction by means of an automatic preparator integrated with the chromatographic system. The calibration graph of the method is linear in the concentration range 6-200 microg/ml; minimum detectable concentration is 6 microg/ml. This highly accurate and easily reproducible method was used by the Authors in the treatment of osteosarcoma with slow infusion of ifosfamide.

Hydroxyapatite-coated orthopaedic screws as infection resistant materials: in vitro study

The authors evaluated in vitro the adherence of a Staphylococcus epidermidis strain to hydroxyapatite-coated stainless-steel screws-used in orthopaedic surgery for external fracture fixation-in comparison with the adherence to uncoated screws. Evaluations were also performed on analogous groups of screws immersed for 72 and 168 h in a solution at 37 degrees C, in order to simulate the interstitial fluid in a simplified way. Adherence values on coated prostheses resulted significantly lower compared with those observed on metal prostheses, both in basal conditions and after immersion in saline solution. Moreover, both on coated and on uncoated screws a significant reduction in bacterial adherence was noted related to the duration of the prosthesis permanence in saline solution.

Lipid peroxidation and antioxidant status in adults receiving lipid-based home parenteral nutrition

BACKGROUND

Infusion of lipid emulsions rich in polyunsaturated fatty acids (PUFAs) may increase lipid peroxidation, which is counteracted mainly by superoxide dismutase (SOD) (a zinc-, copper-, and manganese-dependent enzyme), selenium-dependent glutathione peroxidase (Se-GSHPx), and alpha-tocopherol.

OBJECTIVE

We investigated lipid peroxidation and antioxidant status in patients receiving home parenteral nutrition (HPN) providing variable amounts of a lipid emulsion rich in PUFAs, and alpha-tocopherol, zinc, copper, and manganese as recommended by the American Medical Association, and no selenium.

DESIGN

Serum malondialdehyde, plasma alpha-tocopherol, selenium, Se-GSHPx, PUFAs, and red blood cell Se-GSHPx and SOD were evaluated in 12 patients and in 25 healthy control subjects. Malondialdehyde was also assessed in a group of 40 healthy control subjects.

RESULTS

Patients had significantly higher concentrations of malondialdehyde and SOD and lower alpha-tocopherol concentrations and selenium nutritional status. Linear regression analysis showed that malondialdehyde was associated with the daily PUFA load (r=0.69, P< 0.03) and with plasma alpha-tocopherol (r=-0.59, P< 0.05), but stepwise multiple regression analysis confirmed only the association between malondialdehyde and alpha-tocopherol; plasma alpha-tocopherol was associated with the daily PUFA load (r=-0.65, P< 0.04) and with the duration of HPN (r=-0.74, P< 0.02).

CONCLUSIONS

In HPN patients, the peroxidative stress due to lipid emulsions rich in PUFAs is counteracted primarily by alpha-tocopherol. The dosages of alpha-tocopherol, zinc, copper, and manganese recommended by the American Medical Association appear sufficient to sustain SOD activity but inadequate to maintain alpha-tocopherol nutritional status. HPN formulations should be supplemented with selenium.

The effects of metal corrosion debris on immune system cells

Authors evaluated the correlation between immune system and metal ions release in blood of 17 subjects with Cr/Co/Ni joint prostheses. For the purpose Chromium (Cr), Cobalt (Co) and Nickel (Ni) serum levels were measured and, at the same time some immunological parameters (Leukocytes, Lymphocytes and Lymphocytes T, B and Natural Killer cells sub-populations) were evaluated. The results showed a significant decrease of Leukocytes, Lymphocytes and of T Lymphocytes sub-populations. At the same time it was demonstrated a significant increase of Chromium, Cobalt and Nickel levels in patients with joint prostheses as compared to control population (23 patients). In conclusion, ions release from metallic surface of the prostheses is correlated with a depression of immune system. This correlation could depend on a toxic action on immune system caused by the products released by the implant. It could also depend on a lymphocytes compartimentalization in periprosthetic tissues as a consequence of a cell-mediated hypersensitivity reaction towards implants corrosion products.

Evaluation of cytokines regulating bone turnover in the serum of post-menopausal and senile women

The authors evaluated the Insulin-like Growth Factor-1 (IGF-1) stimulating the formation of bone tissue, and interferon gamma (IFN gamma), inhibiting bone resorption, in the serum of women, 13 of fertile age, 34 of post-menopausal age, and 14 of senile age. Values for IGF-1 in the serum were considerably low in patients of post-menopausal and senile age, and presented highly significant differences with values for subjects of fertile age. The values for IFN gamma did not present significant differences between different age groups. It may be assumed that post-menopause and during senile age physiological osteopenia may be favored by a decrease in the secretion of IGF-1.

Fluorescent microplate assay for respiratory burst of PMNs challenged in vitro with orthopedic metals

This report describes a simple, rapid, automated microassay for measuring in vitro changes of oxidative burst of phagocytes following challenge with metals for orthopedic devices. The production of reactive oxygen species (ROS) by polymorphonuclear leukocytes (PMNs) was measured using 2',7'-dichlorofluorescin-diacetate (DCFH-DA) as fluorescent probe. DCFH-DA enters the cells and is oxidized by ROS to fluorescent DCF. The DCF generated was directly proportional to ROS produced intracellularly: The fluorescence intensity was read and converted to an index of ROS production by cells. In our experimental system, granulocytes (PMNs) were isolated from normal human blood and seeded in microplates. To verify if metals could influence ROS production, chromium, cobalt, nickel, molybdenum, titanium, aluminum, and vanadium prepared as aqueous extracts in phosphate-buffered saline were tested onto PMNs using phorbolmyristate acetate (PMA) as positive control. Molybdenum, aluminum, and vanadium increased ROS generation by PMNs, while signals not different from unstimulated PMNs were recorded for chromium, cobalt, nickel, and titanium. The DCFH-DA microplate-based assay provides an in vitro tool for the detection of oxygen-reactive species generated by PMNs as a response to metals.

In vitro sister chromatid exchange induced by glass ionomer cements

The genotoxicity of three glass ionomer cements used in dentistry, manufactured by American (Vitrebond), Japanese (Fuji I), and European (Ketac Cem) companies were examined. The cement components were mixed according to the manufacturers' instructions and allowed to set for two defined times: 1 h or 1 week, before extracting them, as established by ISO standard 10993 part 12. To highlight sister chromatid exchange during mitosis, the extracts then were tested with human peripheral lymphocytes in the presence or absence of metabolic activation with S9 mix. The test performed was a genotoxicity test as provided for in standard EN 30993 part 3. Vitrebond resulted in direct genotoxicity and was strongly cytotoxic both in the extracts performed at 1 h and those at 1 week if they were allowed to set without photoactivation. Fuji I was noncytotoxic and showed only uncertain indirect genotoxicity in the extracts at 1 h; genotoxicity was not present in the extracts at 1 week. Ketac Cem cement was not genotoxic nor was it cytotoxic either at 1 h or 1 week. The authors concluded that of the three cements tested the European cement Ketac Cem passed one of the tests suggested by the EEC standard for assessing genotoxicity.

The interface of bone microstructure and an innovative coating: an X-ray diffraction study

The in vivo compatibility and degradation aspects of an innovative coating to be sprayed onto titanium implants were investigated. The surface of fluorinated apatite (fHA), consisting of fluorhydroxyapatite plasma sprayed in a vacuum atmosphere, was treated with carbonate to improve its biological compatibility. fHA coating was compared with titanium implants coated (a) with hydroxyapatite (HA) by the traditional plasma spraying, and (b) with titanium oxide (TiOx). Screw-shaped implants were inserted in the cortical bone of sheep tibiae. X-ray diffraction (XRD) analysis of bone tissue and coatings was carried out at 2, 4, 12 and 36 weeks after surgery. The crystallographic habit of the implant-facing bone, as well as the structural stability of the coating, were evaluated. For each time period and type of ceramic bone apatite lattice at the interface, no significantly different reference apatite lattice and no foreign peak were recorded. Two weeks after implantation, the bone at the interface was strongly unmineralized in all samples; after 4 weeks, poorly mineralized bone microareas decreased. At 12 weeks, the newly formed bone tissue at the interface with both the new coating and HA coating was shown to be fully mineralized; this crystallographic habit was retained at 36 weeks, when particle release from the tested material was lower compared to the controls. The XRD pattern of bone apatite surrounding the coating particles was unmodified. The innovative coating did not alter the mineralization process at the interface. It improved implant osteointegration, mainly due to a limited release of particles. Consequently, clinical performance of external fixation treatment could be improved by modifying the chemical composition of the implant surface.

Flow-cytometric analysis of leukocyte activation induced by polyethylene-terephthalate with and without pyrolytic carbon coating

Leukocyte activation is one test for the evaluation of blood-materials interaction. The expression of adhesion molecules analyzed by flow cytometry provides a simple method to evaluate leukocyte activation by biomaterials: any change in these molecules can be predictive of the inflammatory activity of the materials. In this study the contact between leukocytes and uncoated polyethylene terephthalate or pyrolytic carbon-coated polyethylene terephthalate (PET and PET-PC, respectively) was inspected by analyzing whether the expression of some adhesion molecules involved in leukocyte activation, namely LFA-1 (CD11a/ CD18), Mac-1/CR3 (CD11b/CD18), and LECAM-1 (CD62L) can be modified. By flow cytometry expression of the adhesion molecules can be studied separately on lymphocytes and myeloid cells. The materials tested reduced the total numbers of both leukocytes and neutrophils, although not significantly. Neither PET nor PET-PC changed the expression of the adhesion molecules in lymphocytes: this suggests that no specific immune response is stimulated. On the contrary, statistically significant changes were observed for monocytes and granulocytes: the percentage of cells expressing Mac-1 and the density of such antigens on cell membranes increased while the percentage of LECAM-1 positive cells decreased. Similar changes were observed when the cells underwent the inflammatory stimulus provided by an in vitro challenge with bacterial endotoxin. Our results demonstrated that polyethylene terephthalate activates leukocytes by modifying the expression in neutrophils of the molecules involved in the early phase of the inflammatory response. Even after coating PET with pyrolytic carbon, the ability of this material to activate circulating leukocytes was maintained.

Detection of mutagenic potential of some glass-ionomer cements through Ames testing

The mutagenic potential of three commercially available glass-ionomer cements used in dentistry was examined. The cement components were mixed according to the manufacturers indications and set for two defined times: 1 h or, alternatively, 1 wk. Cements B and C set spontaneously; in the case of cement A, the manufacturer suggests the use of a lamp to trigger also a photopolymerization. Photopolymerization, however, was not used. Ames tests were performed on the dimethyl sulphoxide extracts of cements by using Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537, TA 1538 and TA 102. Cement A showed mutagenicity only against TA 1537 strain, either in the presence or absence of metabolic activation with microsomial fraction S9. The other two cements showed no mutagenic potential. We conclude that glass-ionomer cements are, on the whole, safe materials from the viewpoint of genotoxicity, and hypothesize that the mutagenicity observed in cement A could depend on its polymerization performed without light activation.

False positive results in cytotoxicity testing due to unexpectedly volatile compounds

We investigated the cytotoxicity of different dental materials according to the study protocol adopted by our lab for the screening of new materials. Experimental parameters used in such testing are addressed mainly in documents EN 30993 "Biological evaluation of medical devices, Part 5: Tests for cytotoxicity: in vitro methods" and "Biological evaluation of medical devices, Part 12: Sample preparation and reference materials." Cells were cultured in microplates and challenged with aqueous extracts of the materials. The assay methods were neutral red- and propidium iodide-uptake assays, both indicative of cell viability and able to provide quantitative data. The observation of contrasting results for one material using the above-mentioned methods raised some concern about the assay system used. With further experimentation, it appeared that a sustained release of volatile substances still present in one extract exerted a toxic effect in neighboring cultures. It is concluded that in the microenvironment of a microplate the distribution of samples cannot be disregarded, as it may be responsible for toxicity cross-contamination. Moreover, the use of more than one single method has to be recommended in cytotoxicity testing, in order to avoid false positive results due to experimental artifacts.

X-ray diffraction of bone at the interface with hydroxyapatite-coated versus uncoated metal implants

The microstructural characteristics of the newly formed bone tissue at the interface with hydroxyapatite-coated and uncoated stainless steel pins used in an external fracture fixation system have been evaluated. The bone far from the interface was used as a control. Pins were transversally inserted into the diaphyses of sheep tibiae and were loaded in for six weeks. Three sheep received coated pins and two received uncoated pins. Crystallographic habit and mineralization of the implant-facing bone were evaluated. Moreover, lattice parameters of bone apatite were measured and hydroxyapatite (HA) coating degradation was investigated, by means of conventional and microbeam X-ray diffraction (XRD). In coated pins, six weeks after the implantation the newly formed bone tissue at the interface did not reach complete maturation, but the presence of the implant did not alter the apatite lattice structure; the lattice parameters did not show statistically significant variations with respect to those observed in the control bone. In uncoated pins, bone tissue rarely appeared totally mineralized and lattice parameters were significantly different with respect to those observed in the bone far from the implant. HA particles were observed spreading in the bone-facing coated pins; the XRD pattern of bone apatite surrounding HA particles was unmodified. It was concluded that HA coatings improved the bone remodelling process during pin fixation in comparison to uncoated pins and did not alter the crystallographic habit of apatite.

Cell death induced by metal ions: necrosis or apoptosis?

We have evaluated if the cytotoxic effects of metals released from implants are due to necrosis or apoptosis. Peripheral blood mononuclear cells were exposed to different concentrations of chromium, nickel and cobalt extracts and the characteristics of both apoptosis and necrosis were evaluated by flow-cytometry at different culture endpoints. In order to define the prevalence of apoptosis or necrosis, the ratio cell death/apoptosis was calculated. A ratio of </=1 means the prevalence of apoptotic events; a ratio >1 indicates the acute toxicity of the tested substance (necrosis). The extracts of chromium, cobalt and nickel had a cytotoxic effect on the mononuclear cells; high concentrations of cobalt and nickel produced cell necrosis, whereas by lowering the extract concentration apoptotic phenomena were observed. High chromium concentrations can induce cell death by apoptosis. Our data suggest that when large amounts of nickel and cobalt are released from implanted metal devices, necrosis is produced and consequently a strong inflammatory tissue reaction is likely to occur. The release of either chromium or limited amounts of nickel and cobalt induces toxicity characterized by apoptotic phenomena, which allows an adaptation of the tissue to the implant.

Effects of chromium extract on cytokine release by mononuclear cells

We have evaluated the effects of chromium extract on the release by peripheral blood mononuclear cells (PBMCs) of cytokines favouring bone resorption. Furthermore, we have evaluated whether the chromium effects could be correlated with the activation and proliferation of PBMCs. Cell cultures were maintained in serum-free medium (AIM-V), in order to avoid the interference of exogenous growth factors. Increasing concentrations of chromium extract, ranging between 3 and 100%, were added to culture medium. Cytokine release (IL-1beta, TNFalpha, IL-6, GM-CSF and IFNgamma) was assessed on both PBMCs cultured with AIM-V only (unstimulated PBMC) and PBMCs cultured with AIM-V plus phytohaemagglutinina (PHA-stimulated PBMC). The activation and proliferation of PBMCs were evaluated by assessing DNA synthesis and soluble IL-2 receptor release, in order to determine whether an IL-2-dependent immune response can be induced by chromium. Our results show that in unstimulated PBMCs chromium ions slightly increased the release of pro-inflammatory cytokines, such as TNFalpha and IL-6, even though the increase is not significant. On the contrary, the different concentrations of chromium extract significantly inhibited the response to PHA stimulation, as shown by the decrease in IL-6 and sIL-2r release, and by the influence on cell viability and DNA synthesis. Both these effects are undesirable and support hypotheses on the biological effects of chromium. The continuous release of chromium from the implant could induce in PBMCs the release of bone-resorbing cytokines, which in the long term could be responsible for irreversible tissue damage. Moreover, chromium seems to inhibit the IL-2-dependent response of PBMCs, so that they are not able to trigger an efficient cell-mediated immune response.

Adhesive protein expression on human endothelial cells after in vitro contact with woven Dacron

In this research adhesive proteins are studied in order to evaluate the interference of woven Dacron in the endothelialization process and in the ability of endothelial cells to bind circulating leucocytes. Endothelial cells from human umbilical vein (HUVEC) were put in contact with woven Dacron for 24 h. PECAM-1, ELAM-1, ICAM-1 and VCAM-1 expression was then evaluated by flow cytometry, using indirect immunofluorescence reaction with monoclonal antibodies. The study of adhesive proteins was completed with the quantitative determination of surface antigens expressed as the antibody binding capacity (ABC). Antigenic density was calculated by the DAKO QFIT calibration system for indirect immunofluorescence. After contact with woven Dacron no significant change was observed in the percentage of positive cells or in the fluorescence intensity of the adhesins. No significant variation was also noted by calculating the surface antigen density by means of calibration fluorospheres. It can be concluded that the material examined does not significantly affect leucocyte adhesion to the endothelium.

In vitro complement activation after contact with pyrolytic carbon-coated and uncoated polyethylene terephthalate

This study was undertaken to evaluate whether the pyrolytic carbon coating of polyethylene terephthalate induces complement activation. Complement activation induced by pyrolytic carbon-coated polyethylene terephthalate (PET+PC) in comparison with uncoated polyethylene terephthalate (PET) was assessed on whole blood collected with heparin. The activation of the classic pathway was evaluated by C4d fragment enzyme immunoassay. The activation of the alternative pathway was evaluated with Bb fragment enzyme immunoassay. The results show that uncoated PET activates the alternative pathway, but not the classic one. PET+PC does not induce complement activation, not even through the alternative pathway. Pyrolytic carbon coating therefore contributes to improving blood compatibility.

Determinants of functional status in healthy Italian nonagenarians and centenarians: a comprehensive functional assessment by the instruments of geriatric practice

OBJECTIVE

To evaluate the physical ability and psychocognitive status of a population more than 90 years of age with regard to sociodemographic, behavioral, and biomedical variables known to affect functional status in old age.

DESIGN

A survey design was used.

SETTING

Emilia Romagna, Northern Italy.

PARTICIPANTS

Eighty-four healthy community-dwelling subjects aged 90 to 106 years.

MEASUREMENTS

Sociodemographic variables, health behavior, anthropometric indices, and serum DHEAS levels were recorded. Functional assessment was performed by instruments currently used in geriatric practice: the Mini-Mental State Examination (MMSE), Geriatric Depression Scale (GDS), and Activities of Daily Living (ADL) scale. A stepwise multiple regression analysis was performed.

RESULTS

GDS scores correlated directly with MMSE scores and inversely with ADL severity scores. Poor education, institutionalization, sensory impairment, muscular mass loss, and lower DHEAS levels were the variables with the highest correlation to functional impairment. Smoking, alcohol consumption, and marital status were relatively unimportant. An inverse association was found between DHEAS levels and dependency scores of single ADLs (continence, mobility).

CONCLUSION

Impaired cognitive and physical ability with no increase in depression prevalence was found in a sample of subjects more than 90 years of age free of major age-related disease. Muscular mass and DHEAS levels seem to play a role in maintaining physical independence. In turn, physical independence, as well as social and cultural factors, strongly affect the compliance of long-lived subjects with psychocognitive tests currently used in the clinical evaluation of younger old people, suggesting that these instruments are not reliable for screening for cognitive impairment and depression in the oldest old subjects.

CD62, thromboxane B2, and beta-thromboglobulin: a comparison between different markers of platelet activation after contact with biomaterials

The authors examined the modifications of some markers of platelet activation after contact with biomaterials. Glycoprotein GMP-140 (CD62) was evaluated by flow cytometry; beta-thromboglobulin (beta-TG) and thromboxane B2 (TXB2) were determined by radioimmunoassay. Polyethylene terephthalate (PET) induced a remarkable platelet adhesion and a significant increase in beta-TG and TXB2, with no increase in CD62 on the nonadherent platelets. Pyrolytic carbon-coated PET (PC) did not induce platelet adhesion after 15 min of contact, but a significant increase in CD62 was detected. After 30 min a significant increase in platelet adhesion as well as the release of beta-TG and TXB2 were noted. The increase was lower than that observed for uncoated PET, and after 30 min of contact with PC the increase no longer was observed.

[Plasma protein adsorption on variously treated +polybutylene terephthalate]

BACKGROUND

The aim of the research was the evaluation of plasmatic protein adsorption on untreated polybutylene terephthalate, corona treated polybutylene terephthalate and polyvinylacetate coated corona treated polybutylene terephthalate.

METHODS

Total proteins, albumin, immunoglobulins, fibrinogen, insulin and ostecalcin were determined on plasma after contact with these polymers.

RESULTS

Unsignificant variations were observed for the assayed proteins.

CONCLUSIONS

The conclusions are drawn that the tested materials do not adsorbe significantly the most important plasmatic proteins.

[In vitro production of endothelin-1 and prostacyclin by cultured endothelial cells in the presence of polymers]

The aim of this study was to evaluate endothelin-1 and prostacyclin production by human endothelial cells cultured in the presence of polyethylene terephthalate and collagen-coated PET. Cell counting and the assay of endothelin-1 and 6-keto-prostaglandin F1 alpha, stable metabolite of prostacyclin, were carried out after 48 hour contact of the cells with the examined materials. Endothelial cell contact with uncoated PET caused a significant reduction in cell number, a significant increase in the production of endothelin-1 and a not significant increase in 6-keto-prostaglandin F1 alpha. The endothelial cell contact with collagen-coated PET caused a highly significant decrease in cell number and a not significant decrease in endothelin-1 and 6-keto-prostaglandin F1 alpha. It was concluded that PET causes both a decrease in cell number and a remarkable increase in endothelin-1. On the contrary, collagen-coated PET determines a decrease in cell number and a slight reduction of endothelin-1 and 6-keto-prostaglandin F1 alpha.

Expression of adhesion molecules on endothelial cells after contact with knitted Dacron

The aim of this study is to evaluate the expression of some adhesion molecules on the surface of endothelial cells cultured in contact with knitted Dacron. These molecules, as mediators of cell adhesion, could play a role in the modulation of adhesion on the biomaterials, therefore conditioning the response of tissues to implant. Twenty different cultures of human umbilical vein endothelial cells (HUVECs) were cultured in contact with knitted Dacron. Both HUVECs grown without the material and HUVECs incubated with endotoxin were used as control. After 24 h, the cell adhesion molecules PECAM-1, ELAM-1, ICAM-1 and VCAM-1 were evaluated on the cells by monoclonal antibodies and flow cytometry. After 24 h of contact with knitted Dacron, a significant decrease in the proportion of cells expressing PECAM-1 was observed, as well as a significant increase in the proportion of cells expressing ELAM-1. The contact with knitted Dacron did not induce significant variations of ICAM-1 and VACM-1. The incubation with endotoxin determined a significant increase in the proportion of ELAM-1-positive cells, a significant increase in ICAM-1 fluorescence intensity, and a significant increase both in fluorescence intensity and in the proportion of VCAM-1-positive cells. The results obtained with the endotoxin are in agreement with those reported in the literature. The ELAM-1 increase, observed after contact with knitted Dacron, could favour leucocyte adhesion, while the decrease in PECAM-1 expression could result from an inhibiting effect on the endothelial cell adhesion so as to hinder the mechanisms involved in the endothelialization of the material. The variations were interpreted as inhibiting endothelialization and favouring the leucocyte adhesion effect by knitted Dacron.

High-performance liquid chromatography assay of N,N-dimethyl-p-toluidine released from bone cements: evidence for toxicity

Five commercially available bone cements were analysed by high-performance liquid chromatography for detecting the residual content of an accelerator, the amine N,N-dimethyl-p-toluidine (DMPT), after curing. It was found that the concentration of DMPT in aqueous extracts decreases with time, being almost absent 7 days after curing. Differences were noticed among the cements; residual DMPT is higher in cements prepared with higher content of the amine. It is verified that DMPT's toxic effect on cell cultures is dose-related; a delay in the cell replication cycle is induced in vitro. Damage is reversible, thus justifying the low bone cement toxicity that is clinically ascertained.