Conceptualizing Scaffold Guided Breast Tissue Regeneration in a Preclinical Large Animal Model.

Scaffold-guided breast tissue regeneration (SGBTR) can transform both reconstructive and cosmetic breast surgery. Implant-based surgery is the most common method. However, there are inherent limitations, as it involves replacement of tissue rather than regeneration. Regenerating autologous soft tissue has the potential to provide a more like-for-like reconstruction with minimal morbidity. Our SGBTR approach regenerates soft tissue by implanting additively manufactured bioresorbable scaffolds filled with autologous fat graft. A pre-clinical large animal study was conducted by implanting 100 mL breast scaffolds (n = 55) made from medical-grade polycaprolactone into 11 minipigs for 12 months. Various treatment groups were investigated where immediate or delayed autologous fat graft, as well as platelet rich plasma, were added to the scaffolds. Computed tomography and magnetic resonance imaging were performed on explanted scaffolds to determine the volume and distribution of the regenerated tissue. Histological analysis was performed to confirm the tissue type. At 12 months, we were able to regenerate and sustain a mean soft tissue volume of 60.9 ± 4.5 mL (95% CI) across all treatment groups. There was no evidence of capsule formation. There were no immediate or long-term post-operative complications. In conclusion, we were able to regenerate clinically relevant soft tissue volumes utilizing SGBTR in a pre-clinical large animal model.

Biomechanical Principles of Breast Implants and Current State of Research in Soft Tissue Engineering for Cosmetic Breast Augmentation.

Currently there are limited implant-based options for cosmetic breast augmentation, and problems associated with those have been increasingly appreciated, most commonly capsular contracture, which occurs due to a chronic foreign body reaction against non-degradable implant materials such as silicone and polyurethane leading to scar tissue formation, pain, and deformity. The underlying biomechanical concepts with implants create a reciprocal stress-strain relationship with local tissue, whilst acting as a deforming force. This means that with time, as the implant continues to have an effect on surrounding tissue the implant and host's biomechanical properties diverge, making malposition, asymmetry, and other complications more likely. Research directed towards development of alternative therapies based on tissue engineering and regenerative medicine seeks to optimize new tissue formation through modulation of tissue progenitors and facilitating tissue regeneration. Scaffolds can guide the process of new tissue formation by providing both an implant surface and a three-dimensional space that promotes the development of a microenvironment that guides attachment, migration, proliferation, and differentiation of connective tissue progenitors. Important to scaffold design are the architecture, surface chemistry, mechanical properties, and biomaterial used. Scaffolds provide a void in which vascularization, new tissue formation, and remodelling can sequentially occur. They provide a conduit for delivery of the different cell types required for tissue regeneration into a graft site, facilitating their retention and distribution. Whilst recent research from a small number of groups is promising, there are still ongoing challenges to achieving clinical translation. This article summarizes the biomechanical principles of breast implants, how these impact outcomes, and progress in scaffold-guided tissue engineering approaches to cosmetic breast augmentation. LEVEL OF EVIDENCE V: 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 .

A Preclinical Animal Model for the Study of Scaffold-Guided Breast Tissue Engineering.

Scaffold-guided breast tissue engineering (SGBTE) has the potential to transform reconstructive breast surgery. Currently, there is a deficiency in clinically relevant animal models suitable for studying novel breast tissue engineering concepts. To date, only a small number of large animal studies have been conducted and characterization of these large animal models is poorly described in the literature. Addressing this gap in the literature, this publication comprehensively describes our original porcine model based on the current published literature and the experience gained from previous animal studies conducted by our research group. In a long-term experiment using our model, we investigated our SGBTE approach by implanting 60 additively manufactured bioresorbable scaffolds under the panniculus carnosus muscle along the flanks of 12 pigs over 12 months. Our model has the flexibility to compare multiple treatment modalities where we successfully investigated scaffolds filled with various treatments of immediate and delayed fat graft and augmentation with platelet rich plasma. No wound complications were observed using our animal model. We were able to grow clinically relevant volumes of soft tissue, which validates our model. Our preclinical large animal model is ideally suited to assess different scaffold or hydrogel-driven soft tissue regeneration strategies. Impact statement The ability to regenerate soft tissue through scaffold-guided tissue engineering concepts can transform breast reconstructive surgery. We describe an original preclinical large animal model to study controlled and reproducible scaffold-guided breast tissue engineering (SGBTE) concepts. This model features the flexibility to investigate multiple treatment conditions per animal, making it an efficient model. We have validated our model with a long-term experiment over 12 months, which exceeds other shorter published studies. Our SGBTE concept provides a more clinically relevant approach in terms of breast reconstruction. Future studies using this model will support the translation of SGBTE into clinical practice.