Derivation of the toxicological threshold of silicon element in the extractables and leachables from the pharmaceutical packaging and process components.

Silicon is one of the most monitored elements in extractables and leachables studies of pharmaceutical packaging systems and related components. There is a need to review and evaluate toxicological thresholds of silicon because of its direct contact with drug products (DP) especially a liquid form of DP with the widely used pharmaceutical packaging systems made of silicon materials like glass and silicone. It is required by regulatory authorities to test silicon content in DP; however, there are no official guidelines on the toxicology of silicon that are currently available, yet the knowledge of toxicological thresholds of silicon is critical to justify the analytical limit of quantification (LOQ). Therefore, we reviewed the toxicity of silicon to derive a toxicological threshold by literature review of toxicity studies of both inorganic and organic silicon compounds. Oral toxicity is low for inorganic silicon like silicon dioxide or organic silicon polymers such as silicone tube/silicone oil (polydimethylsiloxane, or namely, PDMS as the major ingredient). In comparison, inhalational toxicity of silicon dioxide leads to pulmonary silicosis or even lung cancer. When orally administered, the toxicity of silicon dioxide, glass, polymers, or PDMS oligomers varies depending on their morphology, molecular weight (MW), and degrees of polymerization. PDMS with high MW has minimal toxic symptoms with non-detectable degradation/elimination by both intraperitoneal and subcutaneous administration routes, while exposure to either PDMS or small molecule dimethyl silicone compounds by the intravenous administration route may lead to death. We here determined a general parenteral permitted daily exposure (PDE) of 93 µg/day for inorganic silicon element and 100 µg/day for organic silicon element by reviewing toxicological data of both forms of silicon. In conclusion, this work provides evidence for pharmaceutical companies and regulatory agencies on the PDEs of silicon elements in pharmaceutical packaging and process components through a variety of administration routes.

Entirely S-Protected Thiolated Silicone: A Novel Hydrophobic Mucoadhesive and Skin Adhesive.

The aim of this study was the synthesis and evaluation of an entirely S-protected thiolated silicone as novel hydrophobic mucoadhesive and skin adhesive. 2-[(2-Amino-2-carboxyethyl)disulfanyl]nicotinic acid was covalently attached to a poly(dimethylsiloxane)-graft-polyacrylate via amide bond formation. Adhesive properties were determined via the rotating cylinder method and tensile studies on porcine small intestinal mucosa besides on porcine abdominal skin. Rheological characteristics were evaluated on a cone-plate rheometer. The S-protected thiolated silicone exhibited 128 ± 18 µmol immobilized 2-mercaptonicotinic acid per gram of polymer and showed a 5.9-fold extended time of mucosal adhesion compared with the unmodified silicone on the rotating cylinder. With a 2.3-fold higher maximum detachment force and a 1.7-fold higher total work of adhesion tested on porcine small intestinal mucosa, the S-protected thiolated silicone is superior to the unmodified silicone. Furthermore, using porcine abdominal skin, a 2.4-fold higher maximum detachment force and a 4.4-fold higher total work of adhesion obtained for the S-protected thiolated silicone outlines the preferentially adhesion to skin. Triggered by N-acetyl-L-cysteine liberated thiol groups form interchain and intrachain disulfide bonds within the polymer (6.7% m/v) causing a 23.0-fold increase in dynamic viscosity (ƞ). In parallel, the elastic modulus (G') and the viscous modulus (G") increased 39.2-fold and 8.1-fold, respectively.

Ultrafine carbon particles promote rotenone-induced dopamine neuronal loss through activating microglial NADPH oxidase.

BACKGROUND: Atmospheric ultrafine particles (UFPs) and pesticide rotenone were considered as potential environmental risk factors for Parkinson's disease (PD). However, whether and how UFPs alone and in combination with rotenone affect the pathogenesis of PD remains largely unknown. METHODS: Ultrafine carbon black (ufCB, a surrogate of UFPs) and rotenone were used individually or in combination to determine their roles in chronic dopaminergic (DA) loss in neuron-glia, and neuron-enriched, mix-glia cultures. Immunochemistry using antibody against tyrosine hydroxylase was performed to detect DA neuronal loss. Measurement of extracellular superoxide and intracellular reactive oxygen species (ROS) were performed to examine activation of NADPH oxidase. Genetic deletion and pharmacological inhibition of NADPH oxidase and MAC-1 receptor in microglia were employed to examine their role in DA neuronal loss triggered by ufCB and rotenone. RESULTS: In rodent midbrain neuron-glia cultures, ufCB and rotenone alone caused neuronal death in a dose-dependent manner. In particularly, ufCB at doses of 50 and 100µg/cm2 induced significant loss of DA neurons. More importantly, nontoxic doses of ufCB (10µg/cm2) and rotenone (2nM) induced synergistic toxicity to DA neurons. Microglial activation was essential in this process. Furthermore, superoxide production from microglial NADPH oxidase was critical in ufCB/rotenone-induced neurotoxicity. Studies in mix-glia cultures showed that ufCB treatment activated microglial NADPH oxidase to induce superoxide production. Firstly, ufCB enhanced the expression of NADPH oxidase subunits (gp91phox, p47phox and p40phox); secondly, ufCB was recognized by microglial surface MAC-1 receptor and consequently promoted rotenone-induced p47phox and p67phox translocation assembling active NADPH oxidase. CONCLUSION: ufCB and rotenone worked in synergy to activate NADPH oxidase in microglia, leading to oxidative damage to DA neurons. Our findings delineated the potential role of ultrafine particles alone and in combination with pesticide rotenone in the pathogenesis of PD.

Reabsorção óssea associada ao implante de silicone em mentoplastia: relato de caso clínico / Bone reabsorption associated with silicone implants in mentoplasty: a clinical case report

Durante muitos anos, os implantes de silicone foram utilizados em cirurgias reconstrutivas e estéticas, principalmente em casos em que o perfil facial do paciente apresenta deficiência no terço inferior da face. Este material tem provado ser bem sucedido na maioria dos aspectos, contudo, algumas complicações já foram bem relatadas na literatura, como é o caso das reabsorções ósseas na região de mento mandibular. No presente artigo os autores apresentam dois casos clínicos de reabsorção óssea da cortical anterior do mento, associada ao implante de silicone e discutem a etiologia, as complicações e o plano de tratamento.

For many years, silicone implants were used in reconstructive and esthetic surgeries, especially in cases in which the facial profile of patients presented deficiencies in the inferior third of the face. This material proved to be successful in most aspects. However, several complications were well reported in the literature, as the case of bone reabsorption in the region of the mandibular chin. In this article, the authors present two clinical cases of bone reabsorption from the anterior cortex of the chin associated with silicone implants and discuss the etiology, complications, and treatment plan.

Assessment of oxidative stress and chromosomal aberration inducing potential of three medical grade silicone polymer materials.

Medical expenditures for devices are increasing along with the ageing of human population and the synthesis of materials such as silicone polymers is on upsurge for manufacturing these devices. The International Organization for Standardization (ISO) emphasizes a battery of tests for preclinical assessment of biocompatibility of medical devices. Genotoxicity assays have become an integral component of these test procedures and it employs a set of in vitro and in vivo experiments to detect mutagens. Hence, this study was performed with an intention to investigate the genotoxic potential of the physiological saline extracts of three medical grade silicone polymer materials by the in vitro chromosomal aberration assay using human peripheral blood lymphocytes. Further, the oxidative stress inducing potential of the material extracts was investigated in vivo in mice liver homogenates using cyclophosphamide as positive control. The investigation revealed that none of the three materials were able to produce marked human lymphocyte chromosomal aberration, suggesting the absence of mutagens. The materials also showed negative results in their oxidative stress inducing potential, which was revealed by the normal levels of lipid peroxidation and unaltered levels of glutathione and its metabolizing enzymes in the mice liver tissue homogenates. It was interesting to observe a significant correlation between the genotoxic and antioxidant parameters investigated. Hence, it is suggested that the estimation of antioxidant status would serve as a better preliminary testing procedure prior to evaluating the genetic and molecular toxicity mechanisms of medical devices and/or materials intended for manufacture of such devices.

Histopathological reaction over prosthesis surface covered with silicone and polyurethane foam implanted in rats / Reação histopatológica sobre a superfície de próteses cobertas por espuma de silicone e poliuretano implantadas em ratos

PURPOSES: To evaluate whether polyurethane foam leads more intense foreign-body reaction than silicone foam. To compare the vascularization of the capsules surrounding the foam implants. To investigate if the capsule of polyurethane foam implanted has greater amount of collagen than that of silicone foam. METHODS: Sixty-four young male Wistar rats were allocated into two groups: polyurethane foam and silicone foam. Subcutaneous discs were implanted into the dorsum of the animals in both groups. The capsules were assessed 28 days, two months, three months and six months postoperatively. Microscopic analysis with H&E stain was performed to evaluate the acute and chronic inflammatory process, foreign-body reaction and neovascularization. The analysis with picrosirius red was performed using the ImageProPlus software, to measure the number of vessels and collagen types I and III. RESULTS: There were no statistical differences between the two groups regarding the acute and chronic inflammatory processes. All rats from the polyurethane group, in all times, exhibited moderate or intense foreign-body reaction, with statistic significant difference (p=0.046) when compared with the silicone group, in which the reaction was either mild or nonexistent at two months. Vascular proliferation was significantly different between the groups at 28 days (p=0.0002), with the polyurethane group displaying greater neovascularization with H&E stain. Similar results were obtained with picrosirius red, which revealed in the polyurethane group a much greater number of vessels than in the silicone group (p=0.001). The collagen area was larger in the polyurethane group, significantly at 28 days (p=0.001) and at two months (p=0.030). CONCLUSIONS: Polyurethane foam elicited more intense foreign-body reaction when compared with silicone foam. The number of vessels was higher in the capsules of the polyurethane foam implants 28 days after the operation. The capsule of the polyurethane foam implants showed a greater amount of collagen than that of the silicone foam implants.

OBJETIVOS: Avaliar, em relação ao uso de próteses, se a espuma de poliuretano apresenta maior reação de corpo estranho no organismo ao ser comparada com a espuma de silicone. Se há diferenças na vascularização das cápsulas formada ao redor das duas espumas implantadas. Se as cápsulas dos implantes de espuma de poliuretano apresentam quantidade maior de fibras colágenas ao serem comparadas com as da espuma de silicone. MÉTODOS: Utilizou-se 64 ratos albinos da linhagem Wistar, distribuídos em dois grupos de 34, grupo espuma de poliuretano e grupo espuma de silicone e receberam implantes discóides subcutâneos em seu dorso. Foram analisadas as cápsulas peri-implante com 28 dias, dois, três e seis meses após a introdução. A análise microscópica com H&E considerou as variáveis: inflamação aguda, inflamação crônica, reação de corpo estranho e neoformação vascular. A análise da coloração com picrosirius-red usando ImageProPlus considerou o número de vasos e colágeno tipo I e tipo III. RESULTADOS: Em relação à inflamação aguda e crônica, não foram encontradas diferenças estatísticas nos dois grupos. Todos os animais do grupo poliuretano, em todos os momentos, apresentaram reação de corpo estranho moderada ou intensa e foi encontrada diferença estatística significativa (p=0,046) ao serem comparados com o grupo silicone, cuja reação era ausente ou discreta aos dois meses. A neoformação vascular apresentou diferenças significativas nos dois grupos, aos 28 dias (p=0,0002); o grupo poliuretano com H&E apresentava quantidade maior de vasos neoformados e o mesmo ocorrendo com o picrosirius, cujo número de vasos era maior que no grupo silicone (p=0,001). A área de colágeno em todos os momentos foi maior no grupo poliuretano, sendo significativa com 28 dias (p=0,001) e com dois meses (p=0,030). CONCLUSÕES: A espuma de poliuretano apresentou maior reação de corpo estranho no organismo do que a espuma de silicone. A quantidade de vasos foi maior na cápsula da espuma de poliuretano com 28 dias após o implante. Aos 28 dias as cápsulas dos implantes de espuma de poliuretano apresentaram quantidade significativamente maior de colágeno do que as de espuma de silicone.

Lack of promoting effect of titanium dioxide particles on chemically-induced skin carcinogenesis in rats and mice.

Nano-sized titanium dioxide particles (TiO(2)) are widely used in cosmetics, sunscreens and food additives. We previously reported that topical application of non-coated rutile type TiO(2) did not exhibit a promoting effect on ultraviolet B-initiated skin carcinogenesis in rats, and that this was likely due to lack of penetration of TiO(2) into the epidermis. In the present study, we examined the promoting effect of silicone coated TiO(2 )(sTiO(2)) suspended in silicone oil and non-coated TiO(2 )(ncTiO(2)) suspended in Pentalan 408 on a two-stage skin chemical carcinogenesis model: sTiO(2) suspended in silicon oil forms smaller particles than ncTiO(2) suspended in Pentalan because of the smaller sizes of aggregates formed. The model used skin carcinogenesis-sensitive human c-Ha-ras proto-oncogene transgenic mice (rasH2) and rats (Hras128) and their wild-type counterparts and CD-1 mice to test the effects of topical application of TiO(2). Animals were initially treated with a single dose of 7,12-dimethylbenz[a]anthracene (DMBA) and then with 0, 10, or 20 mg sTiO(2) (mice) or 0, 50, or 100 mg ncTiO(2) (rats). The incidence and multiplicity of skin tumors (squamous cell papilloma and carcinoma) did not increase over DMBA alone controls in skin carcinogenesis-sensitive mice or rats or wild-type animals. Analysis of rat skin indicated that sTiO(2) and ncTiO(2) did not penetrate though either healthy or damaged skin. Furthermore sTiO(2) did not penetrate an in vitro human epidermis model. Our results indicate that treatment with sTiO(2) or ncTiO(2) did not promote skin carcinogenesis in mice or rats, probably due to lack of penetration through the epidermis.

[Preliminary study on immunosuppressive effects evaluation of biomaterial].

In this paper, an immunosuppression model of immunotoxicity built through applying immunosuppressive agent-cyclophosphamide. Subsequently the changes of some assessment indexes including total amount of lymphocytes and concentration of cytokine TNF-alpha in peripheral blood were observed and were used to evaluate immunotoxicity induced by Medical Heat Vulcanizing Silicone Rubber. The final results showed no immunosuppressive effect caused by this material. The study provide effective and sensitive detection technique for evaluation of medical devices and biomaterials' immunotoxicity.

Production of silicon alloys is associated with respiratory symptoms among employees in Norwegian smelters.

OBJECTIVES: To develop a qualitative exposure classification of employees in Norwegian smelters and to investigate the relationship between respiratory symptoms and occupational exposure using this classification. METHODS: The 3,924 participants completed a standardised questionnaire including questions of respiratory symptoms, familial asthma, allergy, doctor-diagnosed asthma, smoking habits, previous exposure and occupation. The employees were classified according to their current job function: (1) line operators were employed full time on the production line, (2) non-exposed employees did not work in production, (3) the remaining employees were classified as non-line operators. The association between the prevalence of respiratory symptoms and job category was examined using multivariate logistic regression. RESULTS: The mean age of the participants was 38.6 years (standard deviation 9.2 years), 88.5% were males. The odds ratios (OR) (95% confidence intervals in parenthesis) for dyspnoea, cough and phlegm regarding previous exposure compared with no previous exposure were 1.4 (1.1-1.7), 1.4 (1.2-1.8) and 1.3 (1.0-1.7), respectively. The OR in line operators compared with non-exposed employees was 1.2 (0.9-1.7) for dyspnoea, 1.3 (1.0-1.8) for cough and 1.9 (1.4-2.7) for phlegm. The OR for respiratory symptoms was higher in relation to previous exposure than current job function except for phlegm. CONCLUSION: In Norwegian smelters respiratory symptoms appear to be positively related to both current job function and previous exposure. Previous exposure appears to be more important than current job function.

Categorizing mistaken false positives in regulation of human and environmental health.

One of the concerns often voiced by critics of the precautionary principle is that a widespread regulatory application of the principle will lead to a large number of false positives (i.e., over-regulation of minor risks and regulation of nonexisting risks). The present article proposes a general definition of a regulatory false positive, and seeks to identify case studies that can be considered authentic regulatory false positives. Through a comprehensive review of the science policy literature for proclaimed false positives and interviews with authorities on regulation and the precautionary principle we identified 88 cases. Following a detailed analysis of these cases, we found that few of the cases mentioned in the literature can be considered to be authentic false positives. As a result, we have developed a number of different categories for these cases of "mistaken false positives," including: real risks, "The jury is still out," nonregulated proclaimed risks, "Too narrow a definition of risk," and risk-risk tradeoffs. These categories are defined and examples are presented in order to illustrate their key characteristics. On the basis of our analysis, we were able to identify only four cases that could be defined as regulatory false positives in the light of today's knowledge and recognized uncertainty: the Southern Corn Leaf Blight, the Swine Flu, Saccharin, and Food Irradiation in relation to consumer health. We conclude that concerns about false positives do not represent a reasonable argument against future application of the precautionary principle.

A new, heavier-than-water silicone oil: a solution of perfluorohexyloctane in polydimethylsiloxane.

PURPOSE: To pre p a re and explore new solutions of semifluorinated alkane in silicone oil, which have a specific gravity slightly higher than silicone oil and vitreous fluid (referred to in the following as heavier-than-water silicone oils (HWSs), and to investigate, in vitro, whether HWSs can be used to plug retina holes, while allowing dehydration of the subretinal space. METHODS: HWS solutions were pre p a red with silicone oil 5000 and perfluorohexyloctane (F6H8). The stability was investigated under different conditions. The viscosity was determined by means of a capillary viscometer. The surface and interface tension were measured using the ring method. RESULTS: HWSs are insoluble in an aqueous medium. Densiron(R)68 (HWS 1.06) is a transparent homogeneous liquid which is slightly heavier (1.06 g/cm3) than water and has a refractive index close to that of vitreous liquid. Densiron68 (HWS 1.06) has a low viscosity (1480 mPas) and interface tension (40.82 mN/m), making it an effective tamponade in the surgical treatment of an inferior detached retina. In addition, the interfaces between Densiron68 and other perfluorocarbon liquids are clearly visible. However, the interface layer between Densiron68 and water is not clear. Finally, all HWSs are stable over the long term at ambient temperatures, as well as physically and thermally resistant. CONCLUSIONS. Due to its physiochemical properties, Densiron68 could meet the requirements for a heavier-than-water tamponade.

Soft tissue response to microtextured silicone and poly-L-lactic acid implants: fibronectin pre-coating vs. radio-frequency glow discharge treatment.

From in vitro studies it is known that a plasma-treatment can enhance cell spreading. Similar effects can be observed after pretreatment of the surface with a protein coating, to mediate cell adhesion. The aim of the current study was to evaluate the in vivo effects of these surface modifications, in a three-month experiment in a goat model. We made silicone and poly-L-lactic acid implants with double-sided parallel micro-grooves (depth 1.0 microm, width 10.0 microm), a random surface roughness, or a smooth surface. Implants either received a radio-frequency glow discharge (RFGD) treatment, a fibronectin (Fn) pre-coating, or no pre-treatment. Subsequently, they were inserted into subcutaneous pockets created on the flanks of goats for 1, 3 or 12 weeks. Histological analysis showed that a fibrous tissue capsule had formed around all implants. Histomorphometrical analysis was performed on capsule thickness, capsule quality and the implant-tissue interface quality. Fn-treated surfaces showed a considerable early inflammatory reaction. Besides this, RFGD treatment or Fn pre-coating did not further influence any of the measured parameters. In conclusion, pre-treatment of polymer implant surfaces with Fn or RFGD treatment did not significantly influence tissue reaction around implants with micro-grooved, roughened or smooth surfaces.

A comparison of the inflammatory response to a polydimethylsiloxane implant in male and female Balb/c mice.

The implantation of biomaterials elicits a host response that influences the long-term behavior of implanted medical devices. This foreign body response is governed by cells of the immune system. Because sexual dimorphism in the immune system is well-established, a comparative study of the foreign body response in male and female mice was initiated. Eight-week-old male and female Balb/c mice received two subcutaneous implants in the interscapular region of a smooth peroxide-catalyzed polydimethylsiloxane (PDMS) and were sacrificed at 2, 14, 42, 70, and 105 days after implantation (n = 6 per sex per time point). Controls for each time point underwent the surgical procedure but received no implant. Tissue from the implant or surgical site was fixed, processed, and paraffin-embedded for histopathological evaluation and immunohistochemical (IHC) staining for tumor necrosis factor-alpha TNF-alpha) and interleukin-1 beta (IL-1beta). In control animals, an inflammatory response was observed at 2 days that was decreased by 14 days and absent after 42 days. At 2 and 14 days after PDMS implantation, a mild to moderate inflammatory reaction was observed around implants. The peak response was seen at 14 days, and granulation tissue, composed primarily of fibroblasts, macrophages, and neutrophils, was first observed at this time. After 105 days, the implantation site was surrounded by mature connective tissue, which had minimal numbers of macrophages and neutrophils, with severity scores that did not differ significantly in males and females. The immunostaining for TNF-alpha and IL-1beta followed similar temporal patterns, with both reaching a peak at the two week time point and remaining elevated, compared to level of expression in the controls, throughout the 105 day observation period. Staining for both cytokines in the implanted animals was generally higher in females than in males, although this difference was significant only for IL-1beta. These results suggest subtle differences between males and females in the activity of peri-implant inflammatory cells.

Surface modification with PEO-containing triblock copolymer for improved biocompatibility: in vitro and ex vivo studies.

Poly(ethylene oxide) (PEO) has been frequently used to modify biomaterial surfaces for improved biocompatibility. We have used PEO-polybutadiene-PEO triblock copolymer to graft PEO to biomaterials by gamma-irradiation for a total radiation dose of 1 Mrad. The molecular weight of PEO in the block copolymer was 5000. In vitro study showed that fibrinogen adsorption to Silastic, polyethylene, and glass was reduced by 70 to approximately 95% by PEO grafting. On the other hand, the reduction of fibrinogen adsorption was only 30% on expanded polytetrafluoroethylene (e-PTFE). In vitro platelet adhesion study showed that almost no platelets could adhere to PEO-coated Silastic, polyethylene, and glass, while numerous platelet aggregates were found on the ePTFE. The platelet adhesion in vitro corresponded to the fibrinogen adsorption. When the PEO-grafted surfaces were tested ex vivo using a series shunt in a canine model, the effect of the grafted PEO was not noticeable. Platelet deposition on ePTFE was reduced by PEO grafting from 8170 +/- 1030 to 5100 +/- 460 platelets 10(-3) microm2, but numerous thrombi were still present on the PEO-grafted surface. The numbers of platelets cumulated on Silastic, polyethylene, and glass were 100 +/- 80, 169 +/- 35, and 24 +/- 22 platelets 10(-3) microm2, respectively. This is about 35% reduction in platelet deposition by PEO grafting. While the numbers of deposited platelets were small, the decreases were not as large as those expected from the in vitro study. This may be due to a number of reasons which have to be clarified in future studies, but it appears that in vitro platelet adhesion and fibrinogen adsorption studies may not be a valuable predictor for the in vivo or ex vivo behavior of the PEO-grafted surfaces.

Influence of long term silicone implantation on type II collagen induced arthritis in mice.

OBJECTIVES: The use of silicone implants in cosmetic and reconstructive surgery has been implicated in the development of autoimmune connective tissue diseases. Previous investigation of the influence of short-term silicone implantation using an experimental model of rheumatoid arthritis revealed no adverse influence upon disease despite the generation of autoantibodies against silicone bound proteins. This study was designed to examine the influence of long term implantation of different forms of silicone in collagen induced arthritis. METHODS: DBA/1 mice were surgically implanted with silicone elastomers, gel or oil nine months before immunisation with type II collagen emulsified in Freund's incomplete adjuvant. The incidence and severity of arthritis, antibodies to type II collagen, and serum cytokines were assessed and compared with sham implanted mice. Silicone implants were recovered, and autoantibodies to silicone bound proteins evaluated in arthritic and non-arthritic mice. RESULTS: Immunisation with CII/FIA resulted in a 30% arthritis incidence in sham implanted DBA/1 mice. Long term silicone implantation resulted in an increased incidence of arthritis, with a significant increase of 90% arthritis in animals implanted with silicone elastomers. Animals implanted with silicone elastomer also developed foreign body sarcomas during the study. Serum concentrations of interleukin 10 were increased in mice implanted with elastomers and immunised with CII/FIA, while interleukin 5 concentrations were significantly diminished in these mice. The production of autoantibodies to autologous silicone bound proteins, including anti-type I collagen antibody, was also attributed to the implantation of either silicone gel or silicone elastomer in type II collagen immunised animals. CONCLUSIONS: These data suggest that long term silicone implantation results in both the production of autoantibodies to connective tissue antigens and increased susceptibility to an experimental model of autoimmune disease.

Silicone gel enhances the development of autoimmune disease in New Zealand black mice but fails to induce it in BALB/cAnPt mice.

Anecdotal evidence links silicone gel breast implants with the development of autoimmune connective tissue disease in women. To investigate whether silicone gel is capable of directly inducing and/or enhancing the development of autoimmune disease, female BALB/cAnPt (BALB/c) and New Zealand Black (NZB) mice were injected subcutaneously with silicone gel, pristane, a nonmetabolizable substance that can cause plasmacytomas in BALB/c and NZB mice, or saline and monitored for the development of glomerulonephritis and autoantibody production. NZB, but not BALB/c, mice spontaneously develop autoantibodies and an autoimmune hemolytic anemia by 12 months of age. Over a period of 10 months, biweekly screening for proteinuria revealed increases in urinary protein in NZB mice that received multiple injections of either silicone gel or pristane. In contrast, urinary protein was unaffected in identically treated BALB/c mice. Although, silicone gel had no effect on serum titers of antierythrocyte antibodies in NZB mice, the hematocrits were significantly decreased. Moreover, silicone gel both increased the concentration of IgM anti-type I collagen antibodies and skewed the immunofluorescent staining pattern of serum autoantibodies on HEp-2 cells. In contrast, silicone gel failed to induce the production of anti-erythrocyte or antinuclear antibodies in BALB/c mice and induced only slight increases in IgG anti-type I collagen antibodies. These results suggest that silicone gel can exacerbate the development of autoimmune disease in autoimmune NZB mice, but fails to induce disease in normal BALB/c mice. This is consistent with several epidemiological studies failing to demonstrate an increase in the incidence of autoimmune disease in women with breast implants. However, because silicone gel was able to exacerbate autoimmune disease in NZB mice, it may play a similar role in the development of autoimmune disease in a small percentage of women who are genetically susceptible to such diseases.

Characterization of cellular response to silicone implants in rats: implications for foreign-body carcinogenesis.

Foreign-body (FB) carcinogenesis is a classic model of multistage tumour development in rodents. Previous studies have demonstrated that the physical characteristics of the implant, and not the chemical composition, are the critical determinants of tumour development. The recent controversy over silicone breast implants has raised questions regarding the potential carcinogenicity of lifetime tissue exposure to silicone products. The present study was designed to determine whether the inflammatory and fibrotic reactions associated with silicone implants are due to a non-specific foreign-body reaction or whether these responses reflect the unique chemical composition of silicone. F344 rats were implanted subcutaneously with one of three biomaterials: silicone elastomer (Group 1); impermeable cellulose acetate filters (Group 2, positive control); or porous cellulose acetate filters (Group 3, negative control). The silicone and cellulose implants of Groups 1 and 2 have been previously shown to induce fibrosarcomas in rodents, whereas the porous cellulose acetate implants of Group 3 have been shown to be non-carcinogenic. One week and two months after implantation, the pericapsular tissues were evaluated using histopathological and in situ immunohistochemical analyses. Endpoints included expression of leucocyte antigens CD4 (T helper/inducer), CD8 (T suppressor/cytotoxic) and CD11 b/c (macrophage), proliferating cell nuclear antigen (PCNA) as an indicator of proliferation, and in situ end-labelling (ISEL) of 3'OH DNA strand breaks as an indicator of DNA damage and apoptosis. The results indicated that the acute and chronic cellular responses to silicone (Group 1) were not different from impermeable cellulose filters (Group 2) of identical size and shape, suggesting that these responses were not unique to silicone. The inflammatory response to the carcinogenic cellulose and silicone implants (Groups 1 and 2) was attenuated and associated with the formation of a thick fibrotic capsule. In contrast, the porous cellulose filters (Group 3) induced a markedly different cellular response in which the inflammatory reaction was more extensive, prolonged and associated with minimal fibrosis. Within the fibrotic capsule surrounding the tumorigenic implants, but not the non-tumorigenic implants, cell proliferation and apoptotic cell death were increased and associated with persistent DNA strand breaks. Taken together, the results suggest that the micrometre-scale surface morphology of the implant determines the nature of the subsequent cellular response which may predispose to tumour development. Further, these studies serve to emphasize the critical importance of appropriate physical controls in studies designed to evaluate carcinogenic or autoimmune manifestations associated with silicone implants in order to rule out the contribution of the chronic foreign-body reaction.

Testicular implants.

Testicular implants have been in use for more than 50 years with an excellent record of safety and efficacy. The controversy concerning the use of silicone prosthetics in breast implants also affected testicular implants. There is no conclusive evidence associating connective tissue disorders, autoimmunity, or malignancy with silicone implants. Studies show silicone leakage from these implants, but long-term follow-up is required to identify the significance of this finding. Saline-filled silastic shell testicular prostheses will be implanted as part of an ongoing study to monitor various safety parameters, as required by the Food and Drug Administration.