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.

Nipple Engineering: Maintaining Nipple Geometry with Externally Scaffolded Processed Autologous Costal Cartilage

INTRODUCTION

Nipple reconstruction is the essential last step of breast reconstruction after total mastectomy, resulting in improved general and aesthetic satisfaction. However, most techniques are limited by secondary scar contracture and loss of neo-nipple projection leading to patient dissatisfaction. Approximately, 16,000 patients undergo autologous flap breast reconstruction annually, during which the excised costal cartilage (CC) is discarded. We propose utilizing processed CC placed within biocompatible 3D-printed external scaffolds to generate tissue cylinders that mimic the shape, size and biomechanical properties of native human nipple tissue while mitigating contracture and projection loss.

METHODS

External scaffolds were designed and then 3D-printed using polylactic acid (PLA). Patient-derived CC was processed by mincing or zesting, then packed into the scaffolds, implanted into nude rats and explanted after 3 months for volumetric, histologic and biomechanical analyses. Similar analyses were performed on native human nipple tissue and unprocessed CC.

RESULTS

After 3 months in vivo, gross analysis demonstrated significantly greater preservation of contour, projection and volume of the scaffolded nipples. Mechanical analysis demonstrated that processing of the cartilage resulted in implant equilibrium modulus values closer to that of the human nipple. Histologic analysis showed the presence of healthy and viable cartilage after 3 months in vivo, invested with fibrovascular tissue.

CONCLUSIONS

Autologous CC can be processed intraoperatively and placed within biocompatible external scaffolds to mimic the shape and biomechanical properties of the native human nipple. This allows for custom design and fabrication of individualized engineered autologous implants tailored to patient desire, without the loss of projection seen with traditional approaches.