Histological study on acute inflammatory reaction to polyurethane-coated silicone implants in rats

Histological evaluation of capsules formed by texturized silicone implants with and without polyester mesh coverage (Parietex®). A study on female rats

Purpose

To evaluate capsules formed by microtextured silicone implants with and without Parietex® mesh coverage histologically.

Methods

Sixty Wistar rats were divided in two groups (meshed and unmeshed). Each group was, then, divided into two subgroups for evaluation at 30 and 90 days. Capsules were analyzed based on hematoxylin and eosin (HE) and picrosirius staining.

Results

The number of fibroblasts, neutrophils and macrophages was similar among all subgroups. There was a higher lymphocyte reaction in the 30-day meshed group (p = 0.003). Giant cell reaction, granulation tissue and neoangiogenesis were similar among the subgroups. Synovial metaplasia was milder at 90-day in the unmeshed (p = 0.002) and meshed group (p < 0.001). Capsular thickness was significantly greater in the meshed samples (30-day p < 0.001 and 90-day p < 0.001). There was a similar amount of collagen types I and III in both groups.

Conclusions

The mesh-covered implants produced capsules similar to the microtextured ones when analyzing inflammatory variables. Synovial metaplasia was milder at 90 than at 30 days, and the capsular thickness was significantly greater in the meshed group. A similar amount of collagen types I and III was observed. Due to these characteristics, the mesh coverage did not seem to significantly affect the local inflammatory activity.

Doxycycline-Coated Silicone Breast Implants Reduce Acute Surgical-Site Infection and Inflammation

BACKGROUND

Surgical-site infection after implant-based breast reconstruction remains a leading cause of morbidity. Doxycycline is an antibiotic used to treat soft-tissue infections. The authors hypothesize that doxycycline-coated breast implants will significantly reduce biofilm formation, surgical-site infection, and inflammation after bacterial infection.

METHODS

Pieces of silicone breast implants were coated in doxycycline. In vitro studies to characterize the coating include Fourier transmission infrared spectroscopy, elution data, and toxicity assays (n = 4). To evaluate antimicrobial properties, coated implants were studied after methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa inoculation in vitro and in a mouse model at 3 and 7 days (n = 8). Studies included bacterial quantification, cytokine profiles, and histology.

RESULTS

Coated silicone breast implants demonstrated a color change, increased mass, and Fourier transmission infrared spectroscopy consistent with a doxycycline coating. Coated implants were nontoxic to fibroblasts and inhibited biofilm formation and bacterial adherence after MRSA and P. aeruginosa incubation in vitro, and measurable doxycycline concentrations at 24 hours were seen. In a mouse model, a significant reduction of MRSA and P. aeruginosa bacterial colonization after 3 and 7 days in the doxycycline-coated implant mice was demonstrated when compared to the control mice, control mice treated with intraperitoneal doxycycline, and control mice treated with a gentamicin/cefazolin/bacitracin wash. Decreased inflammatory cytokines and inflammatory cell infiltration were demonstrated in the doxycycline-coated mice.

CONCLUSIONS

A method to coat silicone implants with doxycycline was developed. The authors' doxycycline-coated silicone implants significantly reduced biofilm formation, surgical-site infections, and inflammation. Further studies are needed to evaluate the long-term implications.

Smooth Muscle Alpha Actin Immunoexpression (α-Sma) and CD-117 Antibody (C-Kit) in Capsules Formed by Polyurethane Foam-Coated Silicone Implants and with Textured Surface: A Study on Rats

BACKGROUND

One of the undesirable complications that might occur after breast augmentation with silicone implants is capsular contracture. In its etiology, the relations between mast cells and myofibroblasts play an important role in collagen synthesis. Mast cells are able to activate fibroblasts into myofibroblasts, through paracrine secretions, inducing collagen production. The objectives of this study were to analyze the myofibroblast concentration through the α-SMA immunomarker and evaluate the intensity of mast cell expression against the C-Kit immunomarker.

MATERIAL AND METHOD

Sixty-four Wistar rats were used, divided into two groups (polyurethane foam and textured surface) with 32 animals in each. The animals received silicone implants on the back, below the panniculus carnosus, and after the determined period, they were killed and the capsules formed around the implants were studied. The capsules were analyzed employing the immunohistochemical technique, with the α-SMA and C-Kit immunomarkers in subgroups of 30, 50, 70 and 90 days.

RESULTS

The myofibroblast concentration was higher in the polyurethane group when compared to the textured group (30 days p = 0.105; 50 days p = 0.247; 70 days p = 0.014 and 90 days p = 0.536). The intensity of mast cell expression was more pronounced in the polyurethane group when compared to the textured group (30 days p = 0.798; 50 days p = 0.537; 70 days p = 0.094 and 90 days p = 0.536).

CONCLUSIONS

Polyurethane-coated implants induced higher concentrations of myofibroblasts and higher expression of mast cells, when compared to the textured surface implants.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Early fragmentation of polyester urethane sheet neither causes persistent oxidative stress nor alters the outcome of normal tissue healing in rat skin

Silicone breast implant is associated with complications inherent to the surgical procedure. Prosthesis coating with polyurethane, however, commonly reduces the incidence of such complications. In this paper, the authors evaluated the inflammatory histomorphometric profile and oxidative damage associated to the implant of polyester urethane sheets. Forty-eight Wistar rats were divided into Sham or polyester urethane groups (n = 8/group) and underwent a polyester urethane implant in the dorsal skinfold. Tissue samples were collected on days seven, 30, and 90 after surgery and subjected to histomorphometric analysis and biochemical tests. Results were analyzed by one-way ANOVA (p ≤ 0.05). Peri-implant tissue samples exhibited characteristic inflammatory response associated with the biomaterial, with increased vascularization on day seven and augmented levels of IL1-b and TNF-a after 30 days. Peri-implant fibrocystic population was small on day seven, but increased considerably after 90 days. A rise in the carbonyl group levels of skin samples in the polyester urethane group was observed on day seven. Findings suggest that polyester urethane sheets undergo biodegradation at an early stage after implantation, followed by increased vascularity and microencapsulation of biomaterial fragments, without persistent oxidative damage. Fiber arrangement inside the collagen matrix results in a fibrotic scar because of polyester urethane degradation.

Silicone Implant Incompatibility Syndrome: Mimicking Metastases on Fluoro-Deoxy-Glucose Positron Emission Tomography-Computed Tomography in a Treated Case of Carcinoma Breast

Silicone implant incompatibility syndrome (SIIS) has been identified as a cause of systemic symptoms such as lymphadenopathy, myalgia, and dyspnea in patients with silicone implants. We present a case of 76-year-old female patient, treated for carcinoma left breast with mastectomy and silicone breast implant, chemotherapy, and radiotherapy 42 years ago. There was a history of implant rupture and removal 2 years ago. The patient presented with right axillary swelling and dyspnea. 18-fluorine fluoro-deoxy-glucose positron emission tomography/computed tomography (F-18 FDG PET-CT) showed mildly FDG-avid left anterior chest wall and right rectus abdominis deposits, multiple lymph nodes, and low-grade FDG-avid pneumonitis changes in both lungs. Biopsy from the chest wall and rectus abdominis deposit was negative for malignancy and revealed foamy histiocytes and foreign-body giant cell reaction, indicative of SIIS. SIIS is a mimic for metastases and should be considered as a differential diagnosis in FDG PET-CT interpretation in patients with silicone breast implant.

Cohesive silicone gel implants with smooth, textured or polyurethane-coated surface to restore volume in eviscerated sockets

The purpose of this article is to evaluate the three different surface coating on cohesive silicone gel implants in eviscerated rabbit eye sockets. Forty-five albino rabbits underwent right eye evisceration and received hemisphere-shaped cohesive silicone gel implants with smooth (Group 1), textured (Group 2), or polyurethane-coated surface (Group 3) in the socket. The animals were euthanized at 7, 30, and 90 days postoperatively. Computed tomography of the orbits was performed prior to euthanasia. Subsequently, the orbital contents were removed and underwent histologic and morphometric examination. Data were statistically analyzed. There were no adverse effects throughout the study. The majority of implants in the Group 1 exhibited 180° rotation. The Group 3 experienced an intense inflammatory reaction around the implant and implant deformation probably due to pseudocapsule contraction. Cohesive silicone gel implants had good integration into the scleral socket. Optimal results were obtained with cohesive silicone gel textured implants (Group 2). Smooth implants (Group 1) rotated significantly, whereas polyurethane (Group 3) coated implants precipitated an intense inflammatory reaction and were deformed postoperatively.

Histological evaluation of capsules formed by silicon implants coated with polyurethane foam and with a textured surface in rats

PURPOSE:

To assess the capsules formed by silicone implants coated with polyurethane foam and with a textured surface.

METHODS:

Sixty-four Wistar albinus rats were divided into two groups of 32 each using polyurethane foam and textured surface. The capsules around the implants were analyzed for 30, 50, 70 and 90 days. Were analyzed the following parameters: foreign body reaction, granulation tissue, presence of myofibroblasts, neoangiogenesis, presence of synovial metaplasia, capsular thickness, total area and collagen percentage of type I and III, in capsules formed around silicone implants in both groups.

RESULTS:

The foreign body reaction was only present in the four polyurethane subgroups. The formation of granulation tissue and the presence of myofibroblasts were higher in the four polyurethane subgroups. Regarding to neoangiogenesis and synovial metaplasia, there was no statistical difference between the groups. Polyurethane group presented (all subgroups) a greater capsule thickness, a smaller total area and collagen percentage of type I and a higher percentage area of type III, with statistical difference.

CONCLUSION:

The use of polyurethane-coated implants should be stimulated by the long-term results in a more stable capsule and a lower incidence of capsular contracture, despite developing a more intense and delayed inflammatory reaction in relation to implants with textured surface.

The effect of a bacterial contamination on the formation of capsular contracture with polyurethane breast implants in comparison with textured silicone implants: an animal study

INTRODUCTION

One of the most common complications following breast augmentation is capsular contracture. The subclinical infection of the implant is often considered to be one of the main risk factors. It is believed that polyurethane (PU) implants, because of their larger foam-like surface, have lower capsular contracture rates due to better tissue integration. It remains unclear if bacterial contamination and biofilm formation result in higher capsular contracture rates under the condition of the increased surface of PU implants compared to textured silicone-gel implants. The effect of this bacterial contamination was examined in an animal-based study.

METHODS

A total of 80 mini implants (40 textured silicone-gel implants and 40 PU implants) were implanted in the dorsum of female Wistar rats. In each group, 20 implants were inoculated before implantation with a standard amount of Staphylococcus epidermidis. Capsules and implants were explanted after 60 days, followed by double-blind histological, immunohistochemical, and microbiological examinations.

RESULTS

Macroscopic separation of the total capsule in the textured implant group was possible whereas the growth of surrounding tissue into the foam structure of PU implants made separation in that group difficult. After contamination, a thicker capsule could be observed in both groups without significant differences. Histologically, capsules around PU implants showed significantly lower expression of parallel myofibrils. We were able to describe a significant higher infiltration with inflammatory cells in capsules around PU implants both with and without contamination. Microbiological investigations revealed positive growth of S. epidermidis around one PU implant without related signs of capsular contracture.

DISCUSSION

This study demonstrates that aside from the surface of silicone implants, bacterial contamination has major impact on the architecture of capsule formation. In our study, we were able to demonstrate that bacterial contamination leads to a thicker capsule and an increased tissue reaction with a higher amount of inflammatory cells. However, a resulting bacterial infection was only demonstrated in one case and had an insignificant influence on capsule architecture. The observed inflammatory reaction around PU implants was observed as a nonbacterial, granulomatose foreign body reaction.

EBM RATING

Level I: Evidence obtained from at least one properly designed randomized controlled trial.