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

Biocompatibility of polyurethane-coated breast implants: A histological comparison of implant capsules

BACKGROUND

Biocompatibility describes the influence of materials on their biological environment. Implant material in the human body can cause a foreign body reaction and the formation of a capsule around the foreign material. Since capsular formation is the most frequent issue after breast-implant insertion, knowledge and awareness of biocompatibility is crucial, especially since worldwide, breast augmentation continues to be the most popular plastic surgery, with over 1.6 million procedures performed in 2020, according to surveys by the International Society of Aesthetic Plastic Surgery (ISAPS).

MATERIAL AND METHODS

This study includes 80 capsular samples of female patients who underwent revision surgery after breast-implant insertion at the University Hospital Regensburg. Capsules of breast implants with different surface structures (smooth, textured and polyurethane-coated) and shapes (round-shaped, anatomically-shaped) were analyzed histologically after hematoxylin-eosin-staining in respect to capsular thickness and layer formation.

RESULTS

Capsular thickness and layering showed a statistically significant difference between polyurethane-coated and smooth as well as polyurethane-coated and textured implants. Capsules around polyurethane-coated implants presented greater thickness. However, the difference between smooth and textured implants was not statistically significant. Furthermore, the shape of the implants also indicated a statistically significant difference in capsular thickness. Implants of anatomical shape resulted in a thinner capsule than round-shaped breast-implants.

CONCLUSION

In conclusion, this study demonstrated a thicker capsule around polyurethane-coated breast implants and no difference in capsular thickness between smooth and textured breast implants. Anatomically shaped breast-implants presented a thinner capsule than round shaped breast-implants.

Human-Mimic Submuscular and Premuscular Irradiated Rat Model: Histologic Characteristics of the Capsule Tissue in Contact with the Breast Implant

Background

In this study, we established two rat models that mimic human submuscular and premuscular breast reconstruction. We analyzed the capsule formation according to surgical techniques and adjacent tissues, including the chest wall tissues, such as the ribs and acellular dermal matrices (ADMs) that come in contact with silicone implants.

Methods

This study consisted of experiments on 12 Sprague-Dawley rats that underwent implant reconstruction using ADM. They were divided into two groups: rats that underwent dual-plane implantation (n = 6; group 1) and those that underwent premuscular implant insertion (n = 6; group 2). All rats were irradiated with 35 Gy of fractionated radiation. Three months after surgery, the histology and immunochemistry of the capsule tissues of the ADM, muscle, and chest wall were analyzed.

Results

Overall capsule thickness was thicker in group 1. Based on the tissue in contact with the silicone implant, ADM had a thinner capsule, less inflammation, less fibrosis, and less vascularization than the muscle and chest wall tissues.

Conclusions

This study described two rat models of clinically relevant implant-based breast reconstruction using a submuscular and premuscular plane, ADM, and irradiation. Overall, the premuscular implantation rat model was associated with a thinner capsule. The ADM in contact with the silicone implant, even after irradiation, had superior protection from radiation compared with the other tissues.

Difference in the Occurrence of Capsular Contracture According to Tissue Characteristics in an Irradiated Rat Model

BACKGROUND

This study was performed to evaluate the hypothesis that capsule formation varies according to the radiation dose in muscle tissues; chest wall tissues, including the ribs; and acellular dermal matrices (ADM) that are in contact with the silicone implant.

METHODS

In this study, 20 Sprague-Dawley rats underwent submuscular plane implant reconstruction using ADM. They were divided into four groups: an unradiated control group ( n = 5), nonfractionated radiation at a dose of 10 Gy ( n = 5), nonfractionated radiation at a dose of 20 Gy ( n = 5), and fractionated radiation at a dose of 35 Gy ( n = 5). Three months after surgery, hardness was measured, and histologic and immunochemical analyses of the capsule tissues of the ADM, muscle tissues, and chest wall tissues were analyzed.

RESULTS

As the radiation dose increased, the silicone implant became harder, but no significant difference in capsule thickness according to the radiation dose was observed. Based on the tissue in contact with the silicone implant, ADM had a thinner capsule thickness than the muscle tissues, as well as less inflammation and less neovascularization compared with the other tissues.

CONCLUSIONS

This study describes a new rat model of clinically relevant implant-based breast reconstruction using a submuscular plane and ADM with irradiation. The ADM in contact with the silicone implant, even after irradiation, was protected from radiation compared with the other tissues.

CLINICAL RELEVANCE STATEMENT

These research results could support the use of ADM in implant-based breast reconstruction for prevention of the capsular contracture, even after radiation.

TGF-β1 and CD68 immunoexpression in capsules formed by textured implants with and without mesh coverage: a study on female rats

PURPOSE

To evaluate fibrosis formation and number of macrophages in capsules formed around textured implants without and with mesh coverage.

METHODS

Fibrosis was analyzed through transforming growth factor-beta 1 (TGF-β1) immunomarker expression and the number of macrophages through CD68 percentage of cells in magnified field. Sixty female Wistar rats were distributed into two groups of 30 rats (unmeshed and meshed). Each group was then subdivided into two subgroups for postoperative evaluation after 30 and 90 days. The p value was adjusted by Bonferroni lower than 0.012.

RESULTS

No difference was observed in fibrosis between meshed and unmeshed groups (30 days p = 0.436; 90 days p = 0.079) and from 30 to 90 days in the unmeshed group (p = 0.426). The meshed group showed higher fibrosis on the 90th day (p = 0.001). The number of macrophages was similar between groups without and with mesh coverage (30 days p = 0.218; 90 days p = 0.044), and similar between subgroups 30 and 90 days (unmeshed p = 0.085; meshed p = 0.059).

CONCLUSIONS

In the meshed group, fibrosis formation was higher at 90 days and the mesh-covered implants produced capsules similar to microtextured ones when analyzing macrophages. Due to these characteristics, mesh coating did not seem to significantly affect the local fibrosis formation.

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.

Reduced Remodeling Biomarkers Tissue Expression in Nanotextured Compared With Polyurethane Implants Capsules: A Study in Rats

BACKGROUND

In the biological response to biomaterials, the implant shell plays a key role in immune and inflammatory reactions. We hypothesized that the capsules formed around nanotextured implants exhibit an immunohistochemical behavior different to those formed around polyurethane implants.

OBJECTIVES

The aim of this study was to evaluate through immunohistochemistry markers the capsules formed around nanotextured and polyurethane implants.

METHODS

Sixty albino female Wistar rats were divided into 2 groups (nanotextured and polyurethane), with 30 animals in each group. A mini silicone implant was inserted on the back of the animals. After a predetermined period, the animals were killed, and the capsules formed around the implants were studied. The capsules in the 30-, 60-, and 90-day subgroups were analyzed via immunohistochemistry to detect markers for fibroblast α smooth muscle actin (α-SMA), transforming growth factor β (TGF-β), cluster of differentiation 34 (CD34), and CD68, via picrosirius staining to determine the density of type I and III collagen fibers and via hematoxylin and eosin staining to assess capsule thickness. A Wilcoxon-Mann-Whitney test was used to compare the groups, and a Kruskal-Wallis test was used to compare the subgroups.

RESULTS

Lower α-SMA, TGF-β, CD34 and CD68 immunoexpression was observed in the nanotextured 30- and 60-day subgroups than in the corresponding polyurethane subgroups. In the 90-day subgroup, more pronounced α-SMA and CD34 immunoexpression was observed in the nanotextured group; however, TGF-β and CD68 immunoexpression remained lower. The nanotextured implants showed reduced capsular thickness and greater formation of type I collagen in all the analyzed subgroups.

CONCLUSIONS

Nanotextured implants led to reduced immune and inflammatory reactions compared with polyurethane implants according to all analyzed variables.

Comparison of inflammatory response and synovial metaplasia in immediate breast reconstruction with a synthetic and a biological mesh: a randomized controlled clinical trial

The aim of this study was to compare inflammatory response and synovial metaplasia in implant-based immediate breast reconstruction with a biological mesh (Veritas^®) with that of a synthetic mesh (TIGR^® Matrix Surgical Mesh). We hypothesize that the inflammatory response and formation of synovial metaplasia might be different and the rate of capsular contracture therefore different. The patients were recruited from the Gothenburg TIGR^®/Veritas^® Study (ClinicalTrials.Gov identifier NCT02985073). All referrals for bilateral immediate breast reconstruction were assessed for inclusions. During the operation, the patients were randomized to which sides the biological and the synthetic mesh were going to be applied. During the implant exchange biopsies were taken. Biopsies were taken from 30 breasts in 15 patients. There seem to be more myofibroblast and neovascularization in the biological meshes than in the synthetic and the collagen fibers seem to be aligned in an irregular pattern with both parallel and vertical fibers. In the synthetic meshes, there were more giant cells and foreign body reaction and the collagen fibers were loosely and well aligned, oriented parallel to the surface of the implant. Synovial metaplasia was seen in the majority of both the biological and the synthetic meshes. The histological patterns in early capsules from biological and synthetic meshes vary considerably. Nonetheless, it is unknown what role different cell types have in capsular formation in the long run and there was no difference in clinical capsular contracture at the clinical follow-up in this study.