A Novel Animal Model for Studying Silicone Gel–Related Capsular Contracture:

Tumor necrosis factor-α-treated human adipose-derived stem cells enhance inherent radiation tolerance and alleviate in vivo radiation-induced capsular contracture

INTRODUCTION

Post-mastectomy radiotherapy plays a crucial role in breast cancer treatment but can lead to an inflammatory response causing soft tissue damage, particularly radiation-induced capsular contracture (RICC), impacting breast reconstruction outcomes. Adipose-derived stem cells (ADSCs), known for their regenerative potential via paracrine capacity, exhibit inherent radiotolerance. The influence of tumor necrosis factor-alpha (TNF-α) on ADSCs has been reported to enhance the paracrine effect of ADSCs, promoting wound healing by modulating inflammatory responses.

OBJECTIVE

This study investigates the potential of TNF-α-treated human ADSCs (T-hASCs) on silicone implants to alleviate RICC, hypothesizing to enhance suppressive effects on RICC by modulating inflammatory responses in a radiation-exposed environment.

METHODS

In vitro, T-hASCs were cultured on various surfaces to assess viability after exposure to radiation up to 20 Gy. In vivo, T-hASC and non-TNF-α-treated hASC (C-hASCs)-coated membranes were implanted in mice before radiation exposure, and an evaluation of the RICC mitigation took place 4 and 8 weeks after implantation. In addition, the growth factors released from T-hASCs were assessed.

RESULTS

In vitro, hASCs displayed significant radiotolerance, maintaining consistent viability after exposure to 10 Gy. TNF-α treatment further enhanced radiation tolerance, as evidenced by significantly higher viability than C-hASCs at 20 Gy. In vivo, T-hASC-coated implants effectively suppressed RICC, reducing capsule thickness. T-hASCs exhibited remarkable modulation of the inflammatory response, suppressing M1 macrophage polarization while enhancing M2 polarization. The elevated secretion of vascular endothelial growth factor from T-hASCs is believed to induce macrophage polarization, potentially reducing RICC.

CONCLUSION

This study establishes T-hASCs as a promising strategy for ameliorating the adverse effects experienced by breast reconstruction patients after mastectomy and radiation therapy. The observed radiotolerance, anti-fibrotic effects, and immune modulation suggest the possibility of enhancing patient outcomes and quality of life. Further research and clinical trials are warranted for broader clinical uses.

Effect of ASC Injection in the Inflammatory Reaction in Silicone Implant Capsule: Animal Model

Background

Capsular contracture is a common complication affecting about 80% of patients who receive radiotherapy after breast reconstruction with silicone prostheses. This study examines the use of adipocyte stem cells (ASCs) to treat capsular contracture.

Methods

Thirty rats were operated on to implant a minisilicone prosthesis in the dorsal region. The rats were divided into three groups: control (saline solution injection), radiotherapy (RDT), and RDT + ASC. After 3 months, the capsules were collected and submitted to histological analysis for inflammatory cell presence, vascular density, and collagen fibers, and gene expression of Tnf, Il1rap, Il10, Cd68, Mmp3, and Mmp9 by qPCR.

Results

In macroscopic analysis, the RTGO score showed a two-point reduction in RDT + ASC compared with the RDT (P = 0.003). In histological analysis, ASC exhibited less than 50% of inflammatory cells compared with RDT (P = 0.004), which was similar to control. This study demonstrated that Il1rap gene expression was identical in both RDT and RTD + ASC. Compared with control, treatment with ASC reduced Il1rap expression by 30%. Cd68 and Mmp3 expression levels were similar in both the control and RTD + ASC.

Conclusion

This study suggests that ASC treatment decreases silicone prosthesis capsule inflammation.

CD248 Regulates Inflammation and Encapsulation in Silicone-Related Capsule Formation

BACKGROUND

Capsular contracture is the most common reason for having a secondary breast implant operation. The failure of the implanted device and discomfort are related to foreign body response, which involves a pathologic encapsulation. An up-regulated expression of CD248 was previously demonstrated to modulate inflammation and fibrosis. The authors hypothesized that CD248 contributes to foreign body reaction and contracture during silicone-stimulated capsule formation.

METHODS

A murine capsular contracture model was established to correlate CD248 with capsular contracture. The timing and site of CD248 expression were characterized by protein analysis and histologic examination. The capsules between wild-type mice and CD248 knockout mice were compared in this model to verify the possible role of CD248 in silicone-related capsule formation.

RESULTS

CD248 was expressed in the peri-silicone implant capsule by stromal fibroblast and perivascular fibroblast. CD248 was overexpressed on day 4 and down to a constant level, but it was still up-regulated through day 21 to day 56 after silicone implantation. The CD248 knockout mice showed a prolonged inflammation period, whereas the wild-type mice developed a thinner but more collagenous capsule.

CONCLUSIONS

In conclusion, an effective murine capsular contracture model was established to study the relationship between CD248 and capsular contracture. CD248 may play a role in inflammation and encapsulation during silicone implantation. CD248 deletion in mice contributed to a loose and irregular collagen bundle in a capsule area, implying a decrease in contracture. Therefore, CD248 could be a potential therapeutic target in capsular contracture.

CLINICAL RELEVANCE STATEMENT

CD248 may play a role in inflammation and encapsulation during silicone implantation. It could be a potential therapeutic target in clinical capsular contracture.

Reducing Peri-implant Capsule Thickness in Submuscular Rodent Model of Breast Reconstruction With Delayed Radiotherapy

INTRODUCTION

Capsular contracture remains the most common complication following device-based breast reconstruction, occurring in up to 50% of women who also undergo adjuvant radiotherapy either before or after device-based reconstruction. While certain risk factors for capsular contracture have been identified, there remains no clinically effective method of prevention. The purpose of the present study is to determine the effect of coating the implant with the novel small molecule Met-Z2-Y12, with and without delayed, targeted radiotherapy, on capsule thickness and morphologic change around smooth silicone implants placed under the latissimus dorsi in a rodent model.

METHODS

Twenty-four female Sprague Dawley rats each had 2 mL smooth round silicone breast implants implanted bilaterally under the latissimus dorsi muscle. Twelve received uncoated implants and twelve received implants coated with Met-Z2-Y12. Half of the animals from each group received targeted radiotherapy (20 Gray) on postoperative day ten. At three and 6 months after implantation, the tissue surrounding the implants was harvested for analysis of capsular histology including capsule thickness. Additionally, microCT scans were qualitatively analyzed for morphologic change.

RESULTS

Capsules surrounding Met-Z2-Y12-coated implants were significantly thinner (P = 0.006). The greatest difference in capsule thickness was seen in the irradiated 6-month groups, where mean capsule thickness was 79.1 ± 27.3 μm for uncoated versus 50.9 ± 9.6 μm for Met-Z2-Y12-coated implants (P = 0.038). At the time of explant, there were no capsular morphologic differences between the groups either grossly or per microCT.

CONCLUSIONS

Met-Z2-Y12 coating of smooth silicone breast implants significantly reduces capsule thickness in a rodent model of submuscular breast reconstruction with delayed radiotherapy.

A long-term fulvestrant eluting implant is safe, non-toxic, and reduces the risk of breast cancer in in vivo models

For individuals at high risk of developing breast cancer, interventions to mitigate this risk include surgical removal of their breasts and ovaries or five years treatment with the anti-estrogen tamoxifen or aromatase inhibitors. We hypothesized that a silicone based anti-estrogen-eluting implant placed within the breast would provide the risk reduction benefit of hormonal therapy, but without the adverse effects that limit compliance. To this end, we demonstrate that when placed adjacent to mammary tissue in the DMBA-induced rat breast cancer model a fulvestrant-eluting implant delays breast cancer with minimal systemic exposure. Using adult female sheep, fulvestrant-eluting implants were found to be safe and non-toxic when placed at the base of the udder for directed elution into the mammary tissue. At 30 days of elution, fulvestrant was found to penetrate mammary tissue forming a concentration gradient beyond 15 mm from the implant. Consistent with the small animal rat study, minimal systemic fulvestrant biodistribution was found. Together, these studies provide the proof of principle that a breast indwelling fulvestrant-eluting implant can reduce the risk of breast cancer and limit systemic exposure, while penetrating and distributing through breast tissue.

An Antifibrotic Breast Implant Surface Coating Significantly Reduces Periprosthetic Capsule Formation

BACKGROUND

The body responds to prosthetic materials with an inflammatory foreign body response and deposition of a fibrous capsule, which may be deleterious to the function of the device and cause significant discomfort for the patient. Capsular contracture (CC) is the most common complication of aesthetic and reconstructive breast surgery. The source of significant patient morbidity, it can result in pain, suboptimal aesthetic outcomes, implant failure, and increased costs. The underlying mechanism remains unknown. Treatment is limited to reoperation and capsule excision, but recurrence rates remain high. In this study, the authors altered the surface chemistry of silicone implants with a proprietary anti-inflammatory coating to reduce capsule formation.

METHODS

Silicone implants were coated with Met-Z2-Y12, a biocompatible, anti-inflammatory surface modification. Uncoated and Met-Z2-Y12-coated implants were implanted in C57BL/6 mice. After 21, 90, or 180 days, periprosthetic tissue was removed for histologic analysis.

RESULTS

The authors compared mean capsule thickness at three time points. At 21, 90, and 180 days, there was a statistically significant reduction in capsule thickness of Met-Z2-Y12-coated implants compared with uncoated implants ( P < 0.05).

CONCLUSIONS

Coating the surface of silicone implants with Met-Z2-Y12 significantly reduced acute and chronic capsule formation in a mouse model for implant-based breast augmentation and reconstruction. As capsule formation obligatorily precedes CC, these results suggest contracture itself may be significantly attenuated. Furthermore, as periprosthetic capsule formation is a complication without anatomical boundaries, this chemistry may have additional applications beyond breast implants, to a myriad of other implantable medical devices.

CLINICAL RELEVANCE STATEMENT

Coating of the silicone implant surface with Met-Z2-Y12 alters the periprosthetic capsule architecture and significantly reduces capsule thickness for at least 6 months postoperatively in a murine model. This is a promising step forward in the development of a therapy to prevent capsular contracture.

Study of the Effect of Different Breast Implant Surfaces on Capsule Formation and Host Inflammatory Response in an Animal Model

BACKGROUND

Breast implants are biomaterials eliciting a physiological and mandatory foreign body response.

OBJECTIVES

The authors designed an animal study to investigate the impact of different implant surfaces on the formation of the periprosthetic capsule, the inflammatory response, and the cellular composition.

METHODS

The authors implanted 1 scaled-down version of breast implants by different manufactures on 70 female Sprague Dawley rats. Animals were divided into 5 groups of 14 animals. Group A received a smooth implant (Ra ≈ 0.5 µm) according to the ISO 14607-2018 classification, Group B a smooth implant (Ra ≈ 3.2 µm), Group C a smooth implant (Ra ≈ 5 µm), Group D a macrotextured implant (Ra ≈ 62 µm), and Group E a macrotextured implant (Ra ≈ 75 µm). At 60 days, all animals received a magnetic resonance imaging (MRI), and 35 animals were killed and their capsules sent for histology (capsule thickness, inflammatory infiltrate) and immunohistochemistry analysis (cellular characterization). The remaining animals repeated the MRI at 120 days and were killed following the same protocol.

RESULTS

MRI showed a thinner capsule in the smooth implants (Groups A-C) at 60 days (P < .001) but not at 120 days (P = .039), confirmed with histology both at 60 days (P = .005) and 120 days (P < .001). Smooth implants (Groups A-C) presented a mild inflammatory response at 60 days that was maintained at 120 days and a high M2-Macrophage concentration (anti-inflammatory).

CONCLUSIONS

Our study confirms that smooth implants form a thinner capsule, inferior inflammatory infiltrate, and a cellular composition that indicates a mild host inflammatory response. A new host inflammatory response classification is elaborated classifying breast implants into mild, moderate, and high.

Implantation and tracing of green fluorescent protein-expressing adipose-derived stem cells in peri-implant capsular fibrosis

BACKGROUND

Adipose-derived stem cells (ASCs) have been reported to reduce fibrosis in various tissues. In this study, we investigated the inhibitory role of ASCs on capsule formation by analyzing the histologic, cellular, and molecular changes in a mouse model of peri-implant fibrosis. We also investigated the fate and distribution of ASCs in the peri-implant capsule.

METHODS

To establish a peri-implant fibrosis model, customized silicone implants were inserted into the dorsal site of C57BL/6 wild-type mice. ASCs were harvested from the fat tissues of transgenic mice that express a green fluorescent protein (GFP-ASCs) and then injected into the peri-implant space of recipient mice. The peri-implant tissues were harvested from postoperative week 2 to 8. We measured the capsule thickness, distribution, and differentiation of GFP-ASCs, as well as the cellular and molecular changes in capsular tissue following ASC treatment.

RESULTS

Injected GFP-ASCs were distributed within the peri-implant capsule and proliferated. Administration of ASCs reduced the capsule thickness, decreased the number of myofibroblasts and macrophages in the capsule, and decreased the mRNA level of fibrogenic genes within the peri-implant tissue. Angiogenesis was enhanced due to trans-differentiation of ASCs into vascular endothelial cells, and tissue hypoxia was relieved upon ASC treatment.

CONCLUSIONS

We uncovered that implanted ASCs inhibit capsule formation around the implant by characterizing a series of biological alterations upon ASC treatment and the fate of injected ASCs. These findings highlight the value of ASCs for future clinical applications in the prevention of capsular contracture after implant-based reconstruction surgery.

Influence of Irradiation on Capsules of Silicone Implants Covered with Acellular Dermal Matrix in Mice

BACKGROUND

In advanced breast cancer, radiotherapy is recommended as adjuvant therapy following breast reconstructive surgery. This inevitably led to growing concerns over possible complications of radiotherapy on implants. In this experimental animal study, we investigated the utility of acellular dermal matrix (ADM) wraps around implants as preventive management for radiotherapy complications.

METHODS

Black mice (C57NL6; n = 32) were assigned to groups that either received radiation or did not: groups A and B underwent surgery using implants without radiotherapy; while groups C and D underwent surgery using implants with radiotherapy for one and three months, respectively. The hemispheric silicone implants with an 0.8-cm-diameter were inserted on the left back of each mouse, and implants wrapped by ADM were inserted on the right back. The Clinic 23EX LINAC model was used for irradiation at 10 Gy. The samples were evaluated by gross assessment, histological analysis, immunohistochemical analysis, and the Western blotting test.

RESULTS

The H&E staining analysis showed that membrane thickness is smallest in group A, followed by groups C, D, and B. In a Masson trichrome histological analysis, collagen fibers became less dense and more widespread over time in the groups that received an ADM. Immunohistochemistry findings were similarly constant. However, the expression of TGF-β1 was increased in the irradiated groups, whereas it was decreased in the non-irradiated groups as observed over time.

CONCLUSIONS

Radiotherapy was shown to increase risk factors for capsular contracture, including inflammatory response, pseudoepithelium, thinning of membrane, and TGF-β1 expression over time; however, the accompanying framework using an ADM as a barrier between implant and tissue was shown to be effective in alleviating these risks.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

The Treatment of Capsular Contracture Around Breast Implants Induced by Fractionated Irradiation: The Collagenase of the Bacterium Clostridium Histolyticum as a Novel Therapeutic Approach

BACKGROUND

Irradiation therapy limits the utilization of silicone implants for breast reconstruction due to a significant risk for capsular contracture. The injection of the collagenase of the bacterium Clostridium histolyticum (CCH) might trivialize this risk by providing a minimal-invasive treatment option by capsular contracture degradation. However, efficacy in degrading breast implant capsules induced by fractionated irradiation remains unclear.

METHODS

Twenty-four rats in three groups received miniature silicone implants in a submuscular pocket. After 3D dose calculation and treatment field definition, rats of two groups underwent fractionated radiotherapy (6 × 8 Gy) using a linear accelerator. A third group served as control. On day 120, one irradiated group received injections of 0.3 mg/ml collagenase. Administration of plain solvent solution served as control in the two other groups. Outcome parameters included CT-imaging, histology, vessel wall analysis, immunohistochemistry, chemical collagen quantification and gene expression analysis.

RESULTS

Fractioned irradiation leads to a significant increase in collagen deposition around silicone implants with higher capsule thickness and collagen density when comparing all groups. Additionally, significant alterations of collagen fiber deposition were evident. Vessel wall thickness was significantly increased after radiotherapy. The injection of collagenase led to a significant reduction of capsule thickness, collagen density and content. However, the collagenase application induced a significant overexpression of TGFβ1. No side effects were monitored.

CONCLUSIONS

The CCH proved to be a safe and effective approach to degrade capsule tissue induced by fractionated irradiation in an animal model. This may pave its way for clinical application in implant-based breast reconstruction patients.

LEVEL OF EVIDENCE

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 .

Comparison of the Effects of Acellular Dermal Matrix and Montelukast on Radiation-Induced Peri-implant Capsular Formation in Rabbits

PURPOSE

Capsular contracture (CC) is a troublesome complication after breast surgery with breast implants, and the risk increases in breast cancer patients after radiotherapy. Studies investigating leukotriene antagonists (eg, montelukast, zafirlukast) found that the acellular dermal matrix (ADM) can help prevent CC. We aimed to compare the effects of ADM and montelukast on CC after irradiation.

METHODS

Eighteen New Zealand white rabbits were randomly divided into 3 groups of 6 each. Miniature cohesive gel implants were inserted into the pocket under the latissimus dorsi muscle. The lateral part was uncovered by the latissimus dorsi muscle. Six animals were included in the control group. In experimental group A (EG-A) (n = 6), the site was partially wrapped with ADM but not covered with muscle. Montelukast (Singulair, 0.2 mg/kg) was administered in experimental group B (EG-B) (n = 6) daily. Groups were irradiated at postoperative day 21 with Co-60 γ rays (25 Gy, single fraction) at the peri-implant area. Rabbits were sacrificed 12 weeks after surgery; implants with peri-implant capsule were harvested. Capsule thickness, collagen pattern, myofibroblast, and transforming growth factor (TGF) β1/2 levels in the peri-implant capsule were evaluated.

RESULTS

On histological evaluation, the capsule was thinner on the lateral aspect (covered with ADM) in EG-A (P = 0.004) and the entire capsule in EG-B (P = 0.004) than in the control group. However, there was no significant difference between EG-A and EG-B (P = 0.073). The collagen distribution pattern was more parallel with low density in the lateral capsular aspect in EG-A, but in the entire capsule in EG-B. The myofibroblast amount (EG-A, P = 0.031; EG-B, P = 0.016) and levels of TGF-β1 and TGF-β2 were reduced in the experimental groups (TGF-β1, EG-A, P = 0.019; TGF-β1, EG-B, P = 0.045; TGF-β2, EG-A, P = 0.018; TGF-β2, EG-B, P = 0.022). There was no significant difference between EG-A and EG-B (myofibroblast, P = 0.201; TGF-β1, P = 0.665; TGF-β2, P = 0.665).

CONCLUSIONS

Acellular dermal matrix and montelukast have a prophylactic effect for CC even when the breast is irradiated. There was no significant difference between ADM and montelukast in preventing capsular formation. The difference is that ADM will only have the effect of covering the capsular formation with ADM and montelukast can cause systemic effects or complications.

The Effect of Omega-3 Fatty Acids on Capsular Tissue around the Breast Implants

BACKGROUND

One of the most common complications of the use of foreign material, in both reconstructive and cosmetic breast surgery, is capsular contracture. Historically, research on capsular contracture has focused mainly on reducing bacterial contamination through antibiotic solutions. Only secondary studies have focused on pharmacological control of the inflammation process, with particular attention paid to the main inflammation pathway, the arachidonic acid cascade. An important role in the arachidonic acid cascade is played by the omega-3 fatty acids, which are found mainly in oily fish and food supplements. The goal of the present study was to investigate the effects of omega-3 supplements on capsule contraction.

METHODS

Female C57BL/6 mice were implanted with custom-made silicone gel implants and divided into two groups. The treated group received omega-3 oil daily while the control group received water daily by gavage. After mice were euthanized, samples of capsules were collected to evaluate thickness and transforming growth factor (TGF)-β expression.

RESULTS

The results showed that capsules in the omega-3 group were thinner and more transparent than those found in the control group. In addition, a significant downregulation of the TGF-β2 gene transcript was observed in the omega-3 group.

CONCLUSIONS

Omega-3 supplementation seems to be effective in reducing the occurrence of capsular formation, mainly through inhibition of the TGF-β pathway and impairment of collagen deposit. Omega-3 supplementation is a simple and promising method that could be used to prevent or at least reduce capsular contracture after silicone implant surgery.

Establishment and Characterization of Bacterial Infection of Breast Implants in a Murine Model

BACKGROUND

Staphylococcus epidermidis and Pseudomonas aeruginosa are the most common causes of Gram-positive and Gram-negative breast implant-associated infection. Little is known about how these bacteria infect breast implants as a function of implant surface characteristics and timing of infection.

OBJECTIVES

The aim of this work was to establish a mouse model for studying the impact of various conditions on breast implant infection.

METHODS

Ninety-one mice were implanted with 273 breast implant shells and infected with S. epidermidis or P. aeruginosa. Smooth, microtextured, and macrotextured breast implant shells were implanted in each mouse. Bacterial inoculation occurred during implantation or 1 day later. Implants were retrieved 1 or 7 days later. Explanted breast implant shells were sonicated, cultured, and colony-forming units determined or analyzed with scanning electron microscopy.

RESULTS

P. aeruginosa could be detected on all device surfaces at 1- and 7- days post infection (dpi), when mice were implanted and infected concurrently or when they were infected 1- day after implantation. However, P. aeruginosa infection was more robust on implant shells retrieved at 7 dpi and particularly on the macrotextured devices that were infected 1 day post implantation. S. epidermidis was mostly cleared from implants when mice were infected and implanted concurrently. Other the other hand, S. epidermidis could be detected on all device surfaces at 1 dpi and 2 days post implantation. However, S. epidermdis infection was suppressed by 7 dpi and 8 days post implantation.

CONCLUSIONS

S. epidermidis required higher inoculating doses to cause infection and was cleared within 7 days. P. aeruginosa infected at lower inoculating doses, with robust biofilms noted 7 days later.

Roxatidine inhibits fibrosis by inhibiting NF‑κB and MAPK signaling in macrophages sensing breast implant surface materials

Capsular contracture is an important complication after silicone mammary implant surgery. Fibroblasts and macrophages play critical roles in the pathogenesis of capsular contracture, making these two cell types therapeutic targets. It has been reported that inhibiting histamine receptors results attenuates fibrosis, but the role of roxatidine (a histamine receptor 2 inhibitor) in preventing fibrosis caused by breast implant materials remains unknown. The aim of the present study was to assess the hypothesis that roxatidine might have a prophylactic effect in capsular contracture induced by implant material. Inflammation induced by breast implant materials was mimicked by co-culturing macrophages or fibroblasts with these materials in vitro. Capsular contracture was modeled in mice by planting breast implant materials in a subcutaneous pocket. Roxatidine was added in the culture medium or administered to mice bearing breast implant materials. By co-culturing macrophages or fibroblasts with common breast implant materials (micro-textured or smooth breast implants), the present study demonstrated that macrophages respond to these materials by producing pro-inflammatory cytokines, a process that was abolished by addition of roxatidine to the culture medium. Although fibroblasts did not respond to implant surface materials in the same way as macrophages, the conditioned media of macrophages induced proliferation of fibroblasts. Mechanistically, administration of roxatidine inhibited activation of NF-κB and p38/mitogen-activated protein kinase (MAPK) signaling in macrophages. Furthermore, treatment with roxatidine in implant-bearing mice reduced serum concentrations of transforming growth factor-β and the abundance of fibroblasts around the implant. The present study concluded that roxatidine plays an important role in preventing fibrosis by inhibiting activation of NF-κB and p38/MAPK signaling in macrophages.

Discovery of Novel Small Molecules that Block Myofibroblast Formation: Implications for Capsular Contracture Treatment

Capsular contracture is a devastating complication that occurs in patients undergoing implant-based breast reconstruction. Ionizing radiation drives and exacerbates capsular contracture in part by activating cytokines, including transforming growth factor-beta (TGF-β). TGF-β promotes myofibroblast differentiation and proliferation, leading to excessive contractile scar formation. Therefore, targeting the TGF-β pathway may attenuate capsular contracture.

METHODS

A 20,000 small molecule library was screened for anti-TGF-β activity. Structurally diverse anti-TGF-β agents were identified and then tested on primary human capsular fibroblasts. Fibroblasts were irradiated or not, and then treated with both TGF-β and candidate molecules. Resulting cells were then analyzed for myofibroblast activity using myofibroblast markers including alpha-smooth muscle actin, collagen I, Thy1, and periostin, using Western Blot, quantitative real-time polymerase chain reaction, and immunofluorescence.

RESULTS

Human capsular fibroblasts treated with TGF-β showed a significant increase in alpha-smooth muscle actin, collagen I, and periostin levels (protein and/or mRNA). Interestingly, fibroblasts treated with latent TGF-β and 10 Gy radiation also showed significantly increased levels of myofibroblast markers. Cells that were treated with the novel small molecules showed a significant reduction in myofibroblast activation, even in the presence of radiation.

CONCLUSIONS

Several novel small molecules with anti-TGF-β activity can effectively prevent human capsular fibroblast to myofibroblast differentiation in vitro, even in the presence of radiation. These results highlight novel therapeutic options that may be utilized in the future to prevent radiation-induced capsular contracture.

The Collagenase of the Bacterium Clostridium histolyticum in the Treatment of Irradiation-Induced Capsular Contracture

BACKGROUND

Irradiation therapy is an important pillar in the treatment of breast cancer. However, it can trigger capsular fibrosis, the most significant complication of implant-based breast reconstruction. As collagen is the main component of fibrotic capsules, the collagenase of the bacterium Clostridium histolyticum poses a potential treatment option for this pathological condition.

METHODS

Thirty-six rats received miniature silicone implants on their backs. On day 1, the implant sites of two groups were irradiated with 10 Gy. On day 120, one irradiated group received collagenase injections into the implant pockets (n = 12). Non-irradiated (n = 12) and irradiated capsules (n = 12) were injected with plain solvent solution serving as controls. Data were analyzed by means of in vivo imaging, histology, immunohistochemistry and gene expression analysis.

RESULTS

Compared with both controls, the injection of collagenase led to significantly thinner capsules. This was verified by in vivo imaging and histology. Although irradiation provoked alterations in capsule collagen structure and vessel wall thickness, the application of collagenase resulted in a significant reduction of collagen density. This was accompanied by an up-regulation of VEGF-A gene expression. Of note, hematoma formation inside the implant pocket occurred in two cases after collagenase injection.

CONCLUSIONS

The collagenase of the bacterium Clostridium histolyticum is effective in degrading irradiation-induced capsular fibrosis around silicone implants. Hematoma formation occurred most likely because of irradiation-induced alterations in vessel wall architecture and capsule vascularization. Further studies need to be performed to address the clinical safety of this novel treatment option.

Periprosthetic Capsule Formation and Contracture in a Rodent Model of Implant-Based Breast Reconstruction With Delayed Radiotherapy

INTRODUCTION

Capsular contracture (CC) is the most common complication of breast implantation, with an incidence of nearly 50% in patients undergoing breast reconstruction with subsequent radiotherapy. Although the move toward submuscular (SM) device placement led to a decreased incidence of CC, subcutaneous (SQ) implantation has seen a resurgence. The purpose of this study was to use a rodent model of breast reconstruction with smooth silicone implants and delayed radiotherapy to assess the occurrence of CC in SQ versus SM implantation.

METHODS

Custom 2 mL smooth round silicone implants were placed bilaterally into 12 female Sprague Dawley rats that were randomized into 4 groups of 3, with each group differing by implantation plane (SQ vs SM) and irradiation status (irradiated vs nonirradiated). Rats from the SQ group received implants bilaterally underlying the skin on the flank. Rats in the SM groups received implants bilaterally under the latissimus dorsi muscle. Irradiated rats received 20 Gy localized to each implant on postoperative day 10. One rat from each group was imaged with a micro-computed tomography scanner at baseline and at explant 3 months later, whereupon capsules from all rats were examined histologically.

RESULTS

Rats in the SQ group showed evidence of contracture on gross examination and greater evidence of morphologic disruption per micro-computed tomography scan. There was no evidence of contracture or morphologic disruption in either SM group. Mean ± SD capsule thickness was 39.0 ± 9.0 μm in the SQ versus 37.6 ± 9.8 μm in the SM nonirradiated groups and 43.9 ± 14.9 μm in the SQ versus 34.3 ± 8.3 μm in the SM irradiated groups (all P > 0.05).

CONCLUSIONS

In a rodent model of smooth silicone breast implantation and delayed radiotherapy, although there did not appear to be differences in capsule thickness regardless of device placement plane, SQ implants demonstrated gross evidence of CC. These data indicate that capsule thickness is only part of a larger pathogenetic picture, which should take into consideration the contribution from all peri-implant tissue.

A murine model of radiation-induced capsule-tissue reactions around smooth silicone implants

As the availability of breast reconstruction using implants is becoming widespread and many implant recipients undergo radiation therapy, there is an increasing interest in understanding the potential complications associated with capsule-tissue interactions in response to irradiation. Accordingly, our medical institution designed an animal experiment to investigate the effects of irradiation on capsular contracture. A total of 40 mice (C57BL6) were divided into four groups according to whether or not they received irradiation and the time from implantation to irradiation. After each mouse received a specially-fabricated, 1.5 cm semi-spherical silicone implant inserted into the area below the panniculus carnosus, half of the mice were irradiated using singe administration of a 10 Gy dose of radiation (6 MeV). Subsequently, data from gross inspection, histological analysis and immunohistochemical analysis were obtained at one and three months postoperatively and analyzed. Changes that occurred near the capsule led to the phenomenon of contracture subsequent to encapsulation. Our findings suggest that the inflammation reaction occurring near the implant becomes aggravated by 'radiation toxicity' and creates an environment conducive to capsular contracture. The present study demonstrated the process by which the complication of capsular contracture may occur during the treatment of human breast cancer via radiotherapy. These findings may serve as the basis for research and development of future treatments of capsular contracture.

Thy1 (CD90) Expression Is Elevated in Radiation-Induced Periprosthetic Capsular Contracture: Implication for Novel Therapeutics

BACKGROUND

Capsular contracture is a devastating complication of postmastectomy implant-based breast reconstruction. Unfortunately, capsular contracture rates are drastically increased by targeted radiotherapy, a standard postmastectomy treatment. Thy1 (also called CD90) is important in myofibroblast differentiation and scar tissue formation. However, the impact of radiotherapy on Thy1 expression and the role of Thy1 in capsular contracture are unknown.

METHODS

The authors analyzed Thy1 expression in primary human capsular tissue and primary fibroblast explants by real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. Thy1 was depleted using RNA interference to determine whether Thy1 expression was essential for the myofibroblast phenotype in capsular fibroblasts. Furthermore, human capsular fibroblasts were treated with a new antiscarring compound, salinomycin, to determine whether Thy1 expression and myofibroblast formation were blocked by salinomycin.

RESULTS

In this article, the authors show that radiation therapy significantly increased Thy1 mRNA and protein expression in periimplant scar tissue. Capsular fibroblasts explanted from scar tissue retained the ability to make the myofibroblast-produced scar-forming components collagen I and α-smooth muscle actin. Depletion of Thy1 decreased the fibrotic morphology of capsular fibroblasts and significantly decreased α-smooth muscle actin and collagen levels. Furthermore, the authors show for the first time that salinomycin decreased Thy1 expression and prevented myofibroblast formation in capsular fibroblasts.

CONCLUSIONS

These data reveal that ionizing radiation-induced Thy1 overexpression may contribute to increased capsular contracture severity, and fibroblast scar production can be ameliorated through targeting Thy1 expression. Importantly, the authors' new results show promise for the antiscarring ability of salinomycin in radiation-induced capsular contracture.

CLINCAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Influence of External Beam Radiotherapy on the Properties of Polymethyl Methacrylate-Versus Silicone-Induced Membranes in a Bilateral Segmental Bone Defect in Rats

INTRODUCTION

Standard care for malignant tumors arising next to a bone structure is surgical removal with safety margins, followed by external beam radiotherapy (EBRT). Complete tumor removal can result in large bone defects. A two-step bone reconstruction technique using the induced membrane (IM) technique has proven its efficacy to bridge gap nonunion. During the first step, a spacer is placed in the bone gap. The spacer then is removed and the IM around it is filled with autologous cancellous bone graft. However, the feasibility of this technique with the addition of adjuvant EBRT between the two reconstruction steps has not yet been studied. Polymethyl methacrylate (PMMA) used to be the standard spacer material for the first step. Silicone spacers could replace them owing to their good behavior when submitted to EBRT and their easier removal from the surgical site during the second step. The aim of this study was to evaluate the influence of EBRT on the histological and biochemical properties of IM induced using PMMA or silicone as spacer.

MATERIALS AND METHODS

The analyses were performed on PMMA- or silicone-IM with and without EBRT in a 6-mm bilateral femoral defect in 32 rats. Thickness and vessel content were measured in both groups. Bone morphogenetic protein 2 (BMP2) and vascular endothelial growth factor (VEGF) content in lysates of the crushed membranes were measured by enzyme immunoassay. Finally, alkaline phosphatase activity was analyzed in human bone marrow stromal cell cultures in contact with the same lysates.

RESULTS

EBRT did not change the histological structure of the cellular internal layer or the fibrous outer layer. The nature of the spacer only influenced IM thickness, PMMA-IM with external radiotherapy being significantly thicker. EBRT decreased the vascular density of IM but was less effective on VEGF/BMP2 production. In vitro, IM could have an osteoinductive potential on human bone marrow stem cells.

CONCLUSION

EBRT did not modify the histological properties of IMs but decreased their vascular density. VEGF and BMP2 production within IMs was not affected by EBRT. Silicone spacers are able to induce membranes with similar histological characteristics to PMMA-IM.

Follistatin and the Breast Implant Capsule

Supplemental Digital Content is available in the text.

Background:

Breast capsular contracture remains an elusive problem faced by plastic surgeons and is the leading long-term complication after breast implantation. Follistatin (Fst) is a protein with known anti-inflammatory and antifibrotic properties and has the potential to limit the severity of diseases associated with inflammation and fibrosis such as capsular contracture. The aim of this study was to examine the effect of Fst288 on capsular fibrosis around silicone implants in a mouse model.

Methods:

BALB/c mice were implanted subcutaneously with untreated silicone implants (baseline control). In the experimental group, immediately after silicone implant insertion, the implant pocket received either a single injection of 1 µg Fst288 or normal saline (internal control). The animals were killed at 3, 5, 7, 14, 28, and 90 days after surgery, and serum, implants, and the surrounding tissue were removed for histological and immunohistochemical analyses.

Results:

Fst288 treatment resulted in significant decreases in capsule thickness at 28 days (P < 0.05) and 3 months (P < 0.001), decreased collagen production at 14 days (P < 0.05) and 3 months (P < 0.01), decreased angiogenesis at 3 months (P < 0.001), decreased α-smooth muscle actin levels at 3 months (P < 0.05), and a decrease in the number of CD45+ cells at days 5 (P < 0.05) and 7 (P < 0.01), respectively, when compared with control implants.

Conclusions:

A single injection of Fst288 at the time of silicone implant insertion into the mice results in a significant reduction in pericapsular inflammation and capsular fibrosis.

Simvastatin Reduces Capsular Fibrosis around Silicone Implants

Capsular fibrosis and contracture occurs in most breast reconstruction patients who undergo radiotherapy, and there is no definitive solution for its prevention. Simvastatin was effective at reducing fibrosis in various models. Peri-implant capsular formation is the result of tissue fibrosis development in irradiated breasts. The purpose of this study was to examine the effect of simvastatin on peri-implant fibrosis in rats. Eighteen male Sprague-Dawley rats were allocated to an experimental group (9 rats, 18 implants) or a control group (9 rats, 18 implants). Two hemispherical silicone implants, 10 mm in diameter, were inserted in subpanniculus pockets in each rat. The next day, 10-Gy of radiation from a clinical accelerator was targeted at the implants. Simvastatin (15 mg/kg/day) was administered by oral gavage in the experimental group, while animals in the control group received water. At 12 weeks post-implantation, peri-implant capsules were harvested and examined histologically and by real-time polymerase chain reaction. The average capsular thickness was 371.2 μm in the simvastatin group and 491.2 μm in the control group. The fibrosis ratio was significantly different, with 32.33% in the simvastatin group and 58.44% in the control group (P < 0.001). Connective tissue growth factor (CTGF) and transforming growth factor (TGF)-β1 gene expression decreased significantly in the simvastatin group compared to the control group (P < 0.001). This study shows that simvastatin reduces radiation-induced capsular fibrosis around silicone implants in rats. This finding offers an alternative therapeutic strategy for reducing capsular fibrosis and contracture after implant-based breast reconstruction.

Quantifying shape changes of silicone breast implants in a murine model using in vivo micro-CT

A major complication of silicone breast implants is the formation of a capsule around the implant known as capsular contracture which results in the distortion of the implant. Recently, a mouse model for studying capsular contracture was examined using micro-computed tomography (micro-CT), however, only qualitative changes were reported. The aim of this study was to develop a quantitative method for comparing the shape changes of silicone implants using in vivo micro-CT. Mice were bilaterally implanted with silicone implants and underwent ionizing radiation to induce capsular contracture. On day 28 post-surgery mice were examined in vivo using micro-CT. The reconstructed cross-section images were visually inspected to identify distortion. Measurements were taken in 2D and 3D to quantify the shape of the implants in the normal (n = 11) and distorted (n = 5) groups. The degree of anisotropy was significantly higher in the distorted implants in the transaxial view (0.99 vs. 1.19, p = 0.002) and the y-axis lengths were significantly shorter in the sagittal (9.27 mm vs. 8.55 mm, p = 0.015) and coronal (9.24 mm vs. 8.76 mm, p = 0.031) views, indicating a deviation from the circular cross-section and shortening of the long axis. The 3D analysis revealed a significantly lower average thickness (sphere-fitting method) in distorted implants (6.86 mm vs. 5.49 mm, p = 0.002), whereas the volume and surface area did not show significant changes. Statistically significant differences between normal and distorted implants were found in 2D and 3D using distance measurements performed via micro-CT. This objective analysis method can be useful for a range of studies involving deformable implants using in vivo micro-CT. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1447-1452, 2017.

Histologic, Molecular, and Clinical Evaluation of Explanted Breast Prostheses, Capsules, and Acellular Dermal Matrices for Bacteria

BACKGROUND

Subclinical infections, manifest as biofilms, are considered an important cause of capsular contracture. Acellular dermal matrices (ADMs) are frequently used in revision surgery to prevent recurrent capsular contractures.

OBJECTIVE

We sought to identify an association between capsular contracture and biofilm formation on breast prostheses, capsules, and ADMs in a tissue expander/implant (TE/I) exchange clinical paradigm.

METHODS

Biopsies of the prosthesis, capsule, and ADM from patients (N = 26) undergoing TE/I exchange for permanent breast implant were evaluated for subclinical infection. Capsular contracture was quantified with Baker Grade and intramammary pressure. Biofilm formation was evaluated with specialized cultures, rtPCR, bacterial taxonomy, live:dead staining, and scanning electron microscopy (SEM). Collagen distribution, capsular histology, and ADM remodeling were quantified following fluorescent and light microscopy.

RESULTS

Prosthetic devices were implanted from 91 to 1115 days. Intramammary pressure increased with Baker Grade. Of 26 patients evaluated, one patient had a positive culture and one patient demonstrated convincing evidence of biofilm morphology on SEM. Following PCR amplification 5 samples randomly selected for 16S rRNA gene sequencing demonstrated an abundance of suborder Micrococcineae, consistent with contamination.

CONCLUSIONS

Our data suggest that bacterial biofilms likely contribute to a proportion, but not all diagnosed capsular contractures. Biofilm formation does not appear to differ significantly between ADMs or capsules. While capsular contracture remains an incompletely understood but common problem in breast implant surgery, advances in imaging, diagnostic, and molecular techniques can now provide more sophisticated insights into the pathophysiology of capsular contracture.

LEVEL OF EVIDENCE

4 Therapeutic.

Comparative study of membranes induced by PMMA or silicone in rats, and influence of external radiotherapy

The induced membrane technique has been used for long bone defect reconstruction after traumatism. One of the major drawbacks of this method is the difficult removal of the polymethyl methacrylate spacer after membrane formation. We therefore replaced the stiff PMMA spacer with a semi-flexible medical grade silicone spacer. This study aimed to compare subcutaneously formed membranes, induced by PMMA and silicone, in the irradiated or not irradiated areas within 28 rats that received the spacers. Histological analysis was performed to evaluate the composition of the membrane and to quantify the amount of vessels. Histomorphometric measurements were used to evaluate membranes' thickness, while fibrosis and inflammation were scored. The expression of VEGF and BMP-2 in lysates of the crushed membranes was determined by Western blotting. ALP expression was analyzed in HBMSC cultures in contact with the same lysates. Non-irradiated membranes induced by the two spacer types were non-inflammatory, fibrous and organized in layers. Irradiation did not change the macroscopic properties of membranes that were induced by silicone, while PMMA induced membranes were sensitive to the radiotherapy, resulting in thicker, strongly inflammatory membranes. Irradiated membranes showed an overall reduced osteogenic potential. Medical grade silicone is safe for the use in radiotherapy and might therefore be of great advantage for patients in need of cancer treatment.

The effect of Zafirlukast on capsule formation in post-radiation silicone implants

Currently, breast cancer represents the most common indication for mastectomy with negative influence on personal perception, sexuality and partnership. Since the introduction of breast implants, silicone, and saline breast implantation have become one of the most common procedures performed by plastic surgeons, not only for aesthetic reasons but also for reconstructive purposes. These women will ultimately be faced with the prospect of capsular contracture. This is especially true in patients receiving radiation therapy, where irradiation increases the risk of complications, capsular contracture and may compromise a favorable aesthetic result. Despite the capsular contracture is the most common complication for both aesthetic and reconstructive breast surgery, the treatment have remained unsolved. Leukotriene antagonists (LTRAs) have emerged as effective prophylactic agents in the management of reactive airway diseases, and recently they have used as an off label prophylactic agent against the capsular contracture after breast augmentation. However up to now there is no any experimental research or clinical study in the medical literature about the effect of Zafirlukast on the capsular formation around irradiated silicone implants.

The impact of Smad3 loss of function on TGF-β signaling and radiation-induced capsular contracture

BACKGROUND

Capsular contracture remains a major problem following prosthetic breast implantation, especially in patients undergoing irradiation. Recent studies suggest that such radiation injuries are a cascading process of cytokine activation, with transforming growth factor (TGF)-β acting as the "master switch." Because TGF-β signals through phosphorylation of Smad3, a plausible approach to abate TGF-β-induced capsular contracture would be to interrupt Smad3 signaling. To test this hypothesis, capsular contracture formation in wild-type and Smad3 knockout mice was compared using micro-computed tomographic and histologic examination.

METHODS

On day 0, 48 mice were implanted with bilateral silicone gel implants. Postoperatively, animals were imaged using live-scan micro-computed tomographic scanning. Animals in the radiation arm then received a 10-Gy directed radiation dose. On postoperative days 21, 28, 35, and 42, animals were imaged again. Histologic evaluation was performed at necropsy.

RESULTS

Irradiated implants in the wild-type mice demonstrated shape and contour deformation on micro-computed tomographic scanning beginning on postoperative day 21 and progressing through day 42. Conversely, micro-computed tomographic scanning of irradiated implants in knockout mice demonstrated few changes from day 0 through day 42. Corresponding histologic specimens from wild-type mice demonstrated irregular capsules composed of disorganized collagen that became thicker from day 21 to day 42. Irradiated knockout specimen maintained thin capsules from day 21 through day 42.

CONCLUSIONS

In this work, inhibiting TGF-β signaling led to a reduction in radiation-induced capsular contracture as measured by micro-computed tomographic and histologic evaluation. The results of this study suggest a promising target for the prevention of capsular contracture through the development of anti-Smad3/TGF-β-based therapies.