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

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.

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.

Optimal Timing of Expander-to-Implant Exchange after Irradiation in Immediate Two-Stage Breast Reconstruction

BACKGROUND

Time intervals for expander-to-implant exchange from radiation therapy have been reported to reduce device failure. This study investigated the optimal timing of expander-to-implant exchange after irradiation in terms of short- and long-term outcomes.

METHODS

This retrospective review enrolled consecutive patients who underwent immediate two-stage breast reconstruction and radiation therapy to tissue expanders from 2010 to 2019. Receiver operating characteristic curves and the Youden index were used to estimate the optimal time from radiation therapy to implant placement in terms of 49-day (early) and 2-year (late) complications. Logistic regression analysis was performed to identify the risk factors for each complication.

RESULTS

Of the 1675 patients, 133 were included. The 49-day and 2-year complication rates were 8.3 percent and 29.7 percent, respectively. Capsular contracture was the most common 2-year complication. The Youden index indicated that implant placement at 131 days after radiation therapy was most effective in reducing the 49-day complications, but that the 2-year complication was less significant, with lower sensitivity and area under the curve. Modified radical mastectomy, expander fill volume at radiation therapy, and size of permanent implant increased the odds of 49-day complications; none of them was associated with the odds of 2-year complications.

CONCLUSIONS

To reduce short-term complications, the best time point for permanent implant placement was 131 days after radiation therapy. However, there was no significant time interval for reducing long-term complications. Capsular contracture was an irreversible complication of radiation injury that was not modified by postirradiation variables including the time from irradiation or size of permanent implant.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Strategy for salvaging infected breast implants: lessons from the recovery of seven consecutive patients

Background

In recent years, implant-based breast reconstruction has been performed because of its simplicity, short operation time, and rapid recovery of patients. Several studies have reported treatment methods for implant surgery-related infection, which is a serious complication. The aim of this study was to introduce our strategy for salvaging infected implants and to evaluate its effectiveness.

Methods

The authors performed a retrospective study of 145 cases from 132 patients who underwent implant-based breast reconstruction from January 2012 to December 2018. Empirical antibiotics were immediately administered to patients with suspected infections. The patients then underwent salvage treatment including appropriate antibiotics, ultrasonography-guided aspiration, debridement, antibiotic lavage, and implant exchange through a multidisciplinary approach. Patient demographics, operative data, duration until drain removal, adjuvant treatment, and complications were analyzed.

Results

The total infection rate was 5.5% (8/145). A longer indwelling catheter period and adjuvant treatment were significantly associated with infection. The salvage treatment showed a success rate of 87.5% (7/8). Seven patients who received early aggressive salvage treatment recovered from infection. One patient with methicillin-resistant Staphylococcus aureus, who received salvage treatment 11 days after symptom onset, did not respond to drainage and antibiotic treatment. That patient subsequently underwent explantation.

Conclusions

In implant-based breast reconstruction, prevention of infection is of the utmost importance. However, if an infection is suspected, proactive empirical antibiotic therapy and collaboration with the necessary departments are required. Through a multidisciplinary approach and proactive early management, swift and appropriate salvage should be performed.

Angiotensin-Converting Enzyme Inhibitor Reduces Radiation-Induced Periprosthetic Capsular Fibrosis

BACKGROUND

The capsular contracture is one of the main complications after radiotherapy in patients with implant-based reconstruction. The aim of this study is to evaluate the efficacy of ramipril for the prevention of radiation-induced fibrosis around the silicone implant.

MATERIALS AND METHODS

Thirty Wistar rats in 5 groups were used. Group 1: implant; group 2: implant + radiation; group 3: ramipril + implant; group 4: ramipril + implant + radiation; group 5: sham. Ramipril treatment was started 5 d before surgery and continued for 12 wk after surgery. A mini silicone implant was placed in the back of the rats. A single fraction of 21.5 Gy radiation was applied. Tissues were examined histologically and immunohistochemically (TGF-β1, MMP-2, and TIMP-2 expression). The alteration of plasma TGF-β1 levels was examined before and after the experiment.

RESULTS

After applying implant or implant + radiation, capsular thickness, percentage of fibrotic area, tissue and plasma TGF-β1 levels significantly increased, and MMP-2/TIMP-2 ratio significantly decreased compared with the sham group. In ramipril-treated groups, the decrease in capsular thickness, fibrosis, TGF-β1 positivity, and an increase in MMP-2/TIMP-2 ratio were found significant. In the ramipril + implant + radiation group, the alteration values of TGF-β1 dramatically decreased.

CONCLUSIONS

Our results show that ramipril reduces radiation-induced fibrosis and contracture. The results of our study may be important for the design of the clinical trials required to investigate the effective and safe doses of ramipril, which is an inexpensive and easily tolerated drug, on humans.

Covalently Grafted 2-Methacryloyloxyethyl Phosphorylcholine Networks Inhibit Fibrous Capsule Formation around Silicone Breast Implants in a Porcine Model

The surface of human silicone breast implants is covalently grafted at a high density with a 2-methacryloyloxyethyl phosphorylcholine (MPC)-based polymer. Addition of cross-linkers is essential for enhancing the density and mechanical durability of the MPC graft. The MPC graft strongly inhibits not only adsorption but also the conformational deformation of fibrinogen, resulting in the exposure of a buried amino acid sequence, γ377-395, which is recognized by inflammatory cells. Furthermore, the numbers of adhered macrophages and the amounts of released cytokines (MIP-1α, MIP-1β, IL-8, TNFα, IL-1α, IL-1β, and IL-10) are dramatically decreased when the MPC network is introduced at a high density on the silicone surface (cross-linked PMPC-silicone). We insert the MPC-grafted human silicone breast implants into Yorkshire pigs to analyze the in vivo effect of the MPC graft on the capsular formation around the implants. After 6 month implantation, marked reductions of inflammatory cell recruitment, inflammatory-related proteins (TGF-β and myeloperoxidase), a myoblast marker (α-smooth muscle actin), vascularity-related factors (blood vessels and VEGF), and, most importantly, capsular thickness are observed on the cross-linked PMPC-silicone. We propose a mechanism of the MPC grafting effect on fibrous capsular formation around silicone implants on the basis of the in vitro and in vivo results.

Creating a Favorable Microenvironment for Fat Grafting in a Novel Model of Radiation-Induced Mammary Fat Pad Fibrosis

BACKGROUND

Radiofibrosis of breast tissue compromises breast reconstruction by interfering with tissue viability and healing. Autologous fat transfer may reduce radiotherapy-related tissue injury, but graft survival is compromised by the fibrotic microenvironment. Elevated expression of receptor for hyaluronan-mediated motility (RHAMM; also known as hyaluronan-mediated motility receptor, or HMMR) in wounds decreases adipogenesis and increases fibrosis. The authors therefore developed RHAMM peptide mimetics to block RHAMM profibrotic signaling following radiation. They propose that this blocking peptide will decrease radiofibrosis and establish a microenvironment favoring adipose-derived stem cell survival using a rat mammary fat pad model.

METHODS

Rat mammary fat pads underwent a one-time radiation dose of 26 Gy. Irradiated (n = 10) and nonirradiated (n = 10) fat pads received a single intramammary injection of a sham injection or peptide NPI-110. Skin changes were examined clinically. Mammary fat pad tissue was processed for fibrotic and adipogenic markers using quantitative polymerase chain reaction and immunohistochemical analysis.

RESULTS

Clinical assessments and molecular analysis confirmed radiation-induced acute skin changes and radiation-induced fibrosis in rat mammary fat pads. Peptide treatment reduced fibrosis, as detected by polarized microscopy of picrosirius red staining, increased collagen ratio of 3:1, reduced expression of collagen-1 crosslinking enzymes lysyl-oxidase, transglutaminase 2, and transforming growth factor β1 protein, and increased adiponectin, an antifibrotic adipokine. RHAMM was expressed in stromal cell subsets and was downregulated by the RHAMM peptide mimetic.

CONCLUSION

Results from this study predict that blocking RHAMM function in stromal cell subsets can provide a postradiotherapy microenvironment more suitable for fat grafting and breast reconstruction.

Botulinum Toxin A Plays an Important Role in the Placement of Implants Deep Within the Pectoralis Major Muscle for Mammaplasty: A Systematic Review and Meta-analysis

BACKGROUND

Breast prosthesis implants have been safely and efficiently used in the plastic surgery department. With the increasing demand for aesthetics, these silicon implants were not only used in breast augmentation surgery but also in breast reconstruction after mastectomy. Nevertheless, breast prosthesis implantation brings a lot of complications, such as: postoperative chronic pain, capsule contracture, prosthesis displacement and prosthesis rupture and infection in severe cases. From the year 1998, botulinum toxin A (BTX-A), a neurotoxin, has been reported to be effective for pain control, capsule contracture lessening, expander enlargement and so on. However, those articles included all kinds of study types: randomized, double-blinded controlled trial (RCT), nonrandomized trial, retrospective analysis and case series, besides the outcomes were varied. To clarify how BTX-A acts at the mammaplasty field, we made this systematic review and meta-analysis.

PURPOSE

To review how BTX-A acts in the field of mammaplasty as well as discuss the relative mechanisms of BTX-A and the related research progress.

METHODS

We searched Pubmed, Embase, Cochrane, Web of science, Clinical trials, Wanfang Database and VIP from inception until March 2018 for papers reporting the use of BTX-A in the breast surgery using implants deep within the pectoralis major muscle. System review, viewpoints and case reports were excluded.

RESULTS

Ten articles met the criteria for inclusion including six prospective controlled (2 RCT; 4 other trails), three retrospective cohorts and one case series. These studies were all about patients using BTX-A during or after breast surgery with expanders or prostheses. A total of 682 patients were enrolled, 543 (79.61%) accepted BTX-A injection, 185 underwent mastectomies with immediate reconstruction, 13 with delayed reconstruction, 295 mastectomies with either immediate or delayed reconstruction and 189 with breast augmentation using silicone prostheses. The study time ranging from 4 months to 13 years, 15 patients (2.76%) received BTX-A injection more than two times, 9.2% received less than 75 U BTX-A, 34.3% 75-100 U, 0.18% 250 U, and in 56.4% the dosage was not stated. No complications associated with BTX-A were mentioned, almost all the studies reported efficacy for pain control. Other assessments included increased speed of expander enlargement and volume were mentioned in four papers, two articles analyzed the visual analogue scores, three suggested relief of capsular contracture, two reported lower narcotic use, three mentioned shorter hospital stays and one proved lowering the rate of unplanned expander. It seems all the studies demonstrate the valid usage of BTX-A, but the quality of this evidence still under the line.

CONCLUSION

We could try to use BTX-A as a new method in the field of mammaplasty. There are so many advantages such as postoperative pain relief, reducing the hospital stay, and increasing operation success rate, but rigorous methodological evidence is still lacking. A lot of studies were retrospective, only two studies used the RCT method. Therefore, to obtain strong evidence to clarify the usage of BTX-A, more randomized double-blinded controlled trials will be required, meanwhile the mechanism study adds to the evidence.

LEVEL OF EVIDENCE III

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 .