In Search of a Murine Model of Radiation-Induced Periprosthetic Capsular Fibrosis

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.

Beneficial effects of transdermal administration of tamoxifen on capsular contracture after breast implantation in murine models

BACKGROUND AND AIM

Capsular contracture is the most common complication with smooth-type silicone implants. We investigated the preventive effect of an active metabolite of tamoxifen, 4-hydroxytamoxifen (4-OH TAM), on capsular contracture.

METHODS

A silicone sheet was implanted into the back of 28 female ICR mice. Mixtures of gel with 0.2% 4-OH TAM and 0.1% 4-OH TAM were administered transdermally once a day for 4 weeks. Saline was administered to the control. After killing the mice, capsular thickness was measured in H&E-stained specimens. Estrogen receptor (ER), α-smooth muscle actin (α-SMA), and transforming growth factor-β (TGF-β) expressions were immunohistochemically investigated in the capsules.

RESULTS

The capsule was thinner in the 0.2% 4-OH TAM gel group than in the control group (control, 0.1% 4-OH TAM gel, 0.2% 4-OH TAM gel: 52.8 ± 3.4 µm, 54.2 ± 6.8 µm, 46.4 ± 3.3 µm, respectively). ER was found in most fibroblasts of all samples. α-SMA expression in the capsule was significantly lower in the 4-OH TAM gel groups than in the control group (control = 70.0 ± 3.4%, 0.1% 4-OH TAM = 57.0 ± 3.4%, 0.2% 4-OH TAM = 49.4 ± 4.9%). TGF-β expression was significantly reduced by the 4-OH TAM gel injections dose-dependently (control = 67.3 ± 2.2%, 0.1% 4-OH TAM = 52.4 ± 3.1%, 0.2% 4-OH TAM = 45.1 ± 2.4%).

CONCLUSIONS

The transdermal administration of 0.1% and 0.2% 4-OH TAM gels inhibited capsule development. The inhibition of TGF-β expression is a mechanism by which 4-OH TAM suppresses fibroblast growth, preventing capsular formation.

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.

Nipple-sparing mastectomy with immediate breast reconstruction - early complications and outcomes of the treatment

AIM OF THE STUDY

To assess the early complications and outcomes of the treatment of patients undergoing nipple-sparing mastectomy (NSM) with immediate breast reconstruction.

MATERIAL AND METHODS

A retrospective study was performed on 120 patients who underwent 130 NSM (10 bilateral) procedures between 1.01.2015 and 31.12.2017 in two oncology centers in Poland. In 80 patients a breast cancer was recognized. Sixteen patients underwent operations on the basis of being carriers of the BRCA1 mutation. The follow-up period ranged from 10 to 34 months. The NSM procedures were performed with or without skin reduction and a free nipple-areola complex (NAC) transplant, with 130 prosthetic devices inserted subpectorally. Breast cancer patients followed the standard protocol for adjuvant therapy.

RESULTS

The patients for risk-reducing mastectomies were younger. Prevalent histology was no special type (NST) in 60 out of 80 patients, mean tumor - NAC distance was 43.3 mm. The prevalent biological subtype was Luminal B HER2-negative. Adjuvant management consisted of chemotherapy in 61 and radiotherapy in 35 patients. We noted 14 cases of complications, 13 in the cancer group, and 1 in the non-cancer group. Skin necrosis was the most common. The mean time for the appearance of the complications was 2.8 months. No local recurrences were observed.

CONCLUSIONS

NSM is a safe and effective surgical option for qualified patients with breast cancer and in risk-reducing mastectomies.

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.