Nipple Reconstruction: A Regenerative Medicine Approach Using 3D-Printed Tissue Scaffolds

3D printing of Ceffe-infused scaffolds for tailored nipple-like cartilage development

The reconstruction of a stable, nipple-shaped cartilage graft that precisely matches the natural nipple in shape and size on the contralateral side is a clinical challenge. While 3D printing technology can efficiently and accurately manufacture customized complex structures, it faces limitations due to inadequate blood supply, which hampers the stability of nipple-shaped cartilage grafts produced using this technology. To address this issue, we employed a biodegradable biomaterial, Poly(lactic-co-glycolic acid) (PLGA), loaded with Cell-Free Fat Extract (Ceffe). Ceffe has demonstrated the ability to promote angiogenesis and cell proliferation, making it an ideal bio-ink for bioprinting precise nipple-shaped cartilage grafts. We utilized the Ceffe/PLGA scaffold to create a porous structure with a precise nipple shape. This scaffold exhibited favorable porosity and pore size, ensuring stable shape maintenance and satisfactory biomechanical properties. Importantly, it could release Ceffe in a sustained manner. Our in vitro results confirmed the scaffold's good biocompatibility and its ability to promote angiogenesis, as evidenced by supporting chondrocyte proliferation and endothelial cell migration and tube formation. Furthermore, after 8 weeks of in vivo culture, the Ceffe/PLGA scaffold seeded with chondrocytes regenerated into a cartilage support structure with a precise nipple shape. Compared to the pure PLGA group, the Ceffe/PLGA scaffold showed remarkable vascular formation, highlighting the beneficial effects of Ceffe. These findings suggest that our designed Ceffe/PLGA scaffold with a nipple shape represents a promising strategy for precise nipple-shaped cartilage regeneration, laying a foundation for subsequent nipple reconstruction.

Long-Term Maintenance of Projection of Nipples Reconstructed Using Three-Dimensionally Printed Poly-4-Hydroxybutyrate Bioabsorbable Scaffolds

BACKGROUND

For patients who are unable to undergo nipple-sparing mastectomy, reconstruction of the nipple-areola complex has been shown to promote greater satisfaction in cosmetic outcome, body image, and sexual relationships. Although a variety of techniques have been developed to optimize the shape, size, and mechanical properties of the reconstructed nipple-areola complex, maintenance of sustained nipple projection over time remains a challenge for plastic surgeons.

METHODS

Three-dimensionally printed poly-4-hydroxybutyrate (P4HB) scaffolds were designed and fabricated filled with either mechanically minced or zested patient-derived costal cartilage, designed with an internal P4HB lattice (rebar) to provide interior structure to foster tissue ingrowth, or left unfilled. All scaffolds were wrapped within a C-V flap on the dorsa of a nude rat.

RESULTS

One year after implantation, neonipple projection and diameter were well preserved in all scaffolded groups compared with nonscaffolded neonipples ( P < 0.05). Histologic analysis showed significant vascularized connective tissue ingrowth at 12 months in both empty and rebar-scaffolded neonipples and fibrovascular cartilaginous tissue formation in mechanically processed costal cartilage-filled neonipples. The internal lattice promoted more rapid tissue infiltration and scaffold degradation and best mimicked the elastic modulus of the native human nipple after 1 year in vivo. No scaffolds extruded or caused any mechanical complications.

CONCLUSIONS

Three-dimensionally printed biodegradable P4HB scaffolds maintain diameter and projection while approximating the histologic appearance and mechanical properties of native human nipples after 1 year with a minimal complication profile. These long-term preclinical data suggest that P4HB scaffolds may be readily translated for clinical application.

CLINICAL RELEVANCE STATEMENT

The authors' unique, three-dimensionally printed P4HB scaffolds can be used to create custom nipple scaffolds that contour to any nipple shape and size, enabling the fabrication of tissue-engineered neonipples with significantly greater projection maintenance and closely approximating desired nipple biomechanical properties.

A review of bioengineering techniques applied to breast tissue: Mechanical properties, tissue engineering and finite element analysis

Female breast cancer was the most prevalent cancer worldwide in 2020, according to the Global Cancer Observatory. As a prophylactic measure or as a treatment, mastectomy and lumpectomy are often performed at women. Following these surgeries, women normally do a breast reconstruction to minimize the impact on their physical appearance and, hence, on their mental health, associated with self-image issues. Nowadays, breast reconstruction is based on autologous tissues or implants, which both have disadvantages, such as volume loss over time or capsular contracture, respectively. Tissue engineering and regenerative medicine can bring better solutions and overcome these current limitations. Even though more knowledge needs to be acquired, the combination of biomaterial scaffolds and autologous cells appears to be a promising approach for breast reconstruction. With the growth and improvement of additive manufacturing, three dimensional (3D) printing has been demonstrating a lot of potential to produce complex scaffolds with high resolution. Natural and synthetic materials have been studied in this context and seeded mainly with adipose derived stem cells (ADSCs) since they have a high capability of differentiation. The scaffold must mimic the environment of the extracellular matrix (ECM) of the native tissue, being a structural support for cells to adhere, proliferate and migrate. Hydrogels (e.g., gelatin, alginate, collagen, and fibrin) have been a biomaterial widely studied for this purpose since their matrix resembles the natural ECM of the native tissues. A powerful tool that can be used in parallel with experimental techniques is finite element (FE) modeling, which can aid the measurement of mechanical properties of either breast tissues or scaffolds. FE models may help in the simulation of the whole breast or scaffold under different conditions, predicting what might happen in real life. Therefore, this review gives an overall summary concerning the human breast, specifically its mechanical properties using experimental and FE analysis, and the tissue engineering approaches to regenerate this particular tissue, along with FE models.

3D-printed poly-4-hydroxybutyrate bioabsorbable scaffolds for nipple reconstruction

Nearly all autologous tissue techniques and engineered tissue substitutes utilized for nipple reconstruction are hindered by scar contracture and loss of projection of the reconstructed nipple. The use of unprocessed costal cartilage (CC) as an internal support for the reconstructed nipple has not been widely adopted because of the excessively firm resultant construct. Herein we use a 3D-printed Poly-4-Hydroxybutyrate (P4HB) bioabsorbable scaffold filled with mechanically processed patient-derived CC to foster ingrowth of tissue in vivo to protect the regenerated tissue from contractile forces as it matures. After 6 months in vivo, newly formed spongy fibrovascular cartilaginous tissue was noted in processed CC filled 3D-printed scaffolds, which maintained significantly greater projection than reconstructions without scaffolds. Interestingly, 3D-printed P4HB scaffolds designed with an internal 3D lattice of P4HB filaments (without CC) displayed the fastest material absorption and vascularized adipose-fibrous tissue as demonstrated by SEM and histological analysis, respectively. Using 3D-printed P4HB scaffolds filled with either processed CC, a 3D P4HB lattice or no fills, we have engineered neo-nipples that maintain projection over time, while approximating the biomechanical properties of the native human nipple. We believe that this innovative 3D-printed P4HB nipple reconstruction scaffold will be readily translatable to the clinic. STATEMENT OF SIGNIFICANCE: Nearly all autologous tissue techniques and engineered tissue substitutes utilized for nipple reconstruction are hindered by scar contracture and substantial loss of projection of the reconstructed nipple, leading to significant patient dissatisfaction. Using 3D-printed P4HB scaffolds filled with either processed costal cartilage or 3D P4HB lattices, we have engineered neo-nipples that resist the forces induced by scar contracture, resulting in maintenance of neo-nipple projection over time and biomechanically approximating human nipples after 6 months in vivo implantation. This novel 3D-printed bioabsorbable P4HB scaffold will be readily translatable to the clinic to reconstruct nipples with patient-specific dimensions and long-lasting projection.

Viability of acellular biologic graft for nipple-areolar complex reconstruction in a non-human primate model

Many of the > 3.5 million breast cancer survivors in the US have undergone breast reconstruction following mastectomy. Patients report that nipple-areolar complex (NAC) reconstruction is psychologically important, yet current reconstruction techniques commonly result in inadequate shape, symmetry, and nipple projection. Our team has developed an allogeneic acellular graft for NAC reconstruction (dcl-NAC) designed to be easy to engraft, lasting, and aesthetically pleasing. Here, dcl-NAC safety and host-mediated re-cellularization was assessed in a 6-week study in rhesus macaque non-human primates (NHPs). Human-derived dcl-NACs (n = 30) were engrafted on the dorsum of two adult male NHPs with each animal's own nipples as controls (n = 4). Weight, complete blood counts, and metabolites were collected weekly. Grafts were removed at weeks 1, 3, or 6 post-engraftment for histology. The primary analysis evaluated health, re-epithelialization, and re-vascularization. Secondary analysis evaluated re-innervation. Weight, complete blood counts, and metabolites remained mostly within normal ranges. A new epidermal layer was observed to completely cover the dcl-NAC surface at week 6 (13-100% coverage, median 93.3%) with new vasculature comparable to controls at week 3 (p = 0.10). Nerves were identified in 75% of dcl-NACs (n = 9/12) at week 6. These data suggest that dcl-NAC is safe and supports host-mediated re-cellularization.

Guiding Nipple-Areola Complex Reconstruction: Literature Review and Proposal of a New Decision-Making Algorithm

BACKGROUND

Nipple-areola complex reconstruction (NAR) most commonly represents the finishing touch to breast reconstruction (BR). Nipple presence is particularly relevant to the patient's psyche, beyond any shadow of doubt. Many reconstructive options have been described in time. Surgery is easy, but final result is often disappointing on the long run.

METHODS

The goal of this manuscript is to analyze and classify knowledge concerning NAR techniques and the factors that influence success, and then to elaborate a practical evidence-based algorithm. Out of the 3136 available articles as of August 8th, 2020, we selected 172 manuscripts that met inclusion criteria, which we subdivided into 5 main topics of discussion, being the various NAR techniques; patient factors (including patient selection, timing and ideal position); dressings; potential complications and finally, outcomes/patient satisfaction.

RESULTS

We found 92 articles describing NAR techniques, 41 addressing patient factors (out of which 17 discussed patient selection, 14 described ideal NAC location, 10 described appropriate timing), 10 comparing dressings, 7 studying NAR complications, and 22 addressing outcomes and patient satisfaction. We elaborated a comprehensive decision-making algorithm to help narrow down the choice among NAR techniques, and choose the correct strategy according to the various scenarios, and particularly the BR technique and skin envelope.

CONCLUSIONS

No single NAR technique provides definitive results, which is why we believe there is no "end-all be-all solution". NAR must be approached as a case-by-case situation. Furthermore, despite NAR being such a widely discussed topic in scientific literature, we still found a lack of clinical trials to allow for more thorough recommendations to be elaborated.

LEVEL OF EVIDENCE III

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.

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.

Applications of 3D printing in breast cancer management

Three-dimensional (3D) printing is a method by which two-dimensional (2D) virtual data is converted to 3D objects by depositing various raw materials into successive layers. Even though the technology was invented almost 40 years ago, a rapid expansion in medical applications of 3D printing has only been observed in the last few years. 3D printing has been applied in almost every subspecialty of medicine for pre-surgical planning, production of patient-specific surgical devices, simulation, and training. While there are multiple review articles describing utilization of 3D printing in various disciplines, there is paucity of literature addressing applications of 3D printing in breast cancer management. Herein, we review the current applications of 3D printing in breast cancer management and discuss the potential impact on future practices.

Acellular Biologic Nipple-Areolar Complex Graft: In Vivo Murine and Nonhuman Primate Host Response Evaluation

There are more than 3 million breast cancer survivors living in the United States of which a significant number have undergone mastectomy followed by breast and nipple-areolar complex (NAC) reconstruction. Current strategies for NAC reconstruction are dependent on nonliving or nonpermanent techniques, including tattooing, nipple prosthetics, or surgical nipple-like structures. Described herein is a tissue engineering approach demonstrating the feasibility of an allogeneic acellular graft for nipple reconstruction. Nonhuman primate (NHP)-derived NAC tissues were decellularized and their extracellular matrix components analyzed by both proteomic and histological analyses. Decellularized NHP nipple tissue showed the removal of intact cells and greatly diminished profiles for intracellular proteins, as compared with intact NHP nipple tissue. We further evaluated the biocompatibility of decellularized grafts and their potential to support host-mediated neovascularization against commercially available acellular dermal grafts by performing in vivo studies in a murine model. A follow-up NHP pilot study evaluated the host-mediated neovascularization and re-epithelialization of onlay engrafted decellularized NAC grafts. The murine model revealed greater neovascularization in the decellularized NAC than in the commercially available control grafts, with no observed biocompatibility issues. The in vivo NHP model confirmed that the decellularized NAC grafts encourage neovascularization as well as re-epithelialization. These results support the concept that a biologically derived acellular nipple graft is a feasible approach for nipple reconstruction, supporting neovascularization in the absence of adverse systemic responses. Impact statement Currently, women in the United States most often undergo a mastectomy, followed by reconstruction, after being diagnosed with breast cancer. These breast cancer survivors are often left with nipple-areolar complex (NAC) reconstructions that are subsatisfactory, nonliving, and/or nonpermanent. Utilizing an acellular biologically derived whole NAC graft would allow these patients a living and permanent tissue engineering solution to nipple reconstruction.

3D Printing Breast Tissue Models: A Review of Past Work and Directions for Future Work

Breast cancer often results in the removal of the breast, creating a need for replacement tissue. Tissue engineering offers the promise of generating such replacements by combining cells with biomaterial scaffolds and serves as an attractive potential alternative to current surgical repair methods. Such engineered tissues can also serve as important tools for drug screening and provide in vitro models for analysis. 3D bioprinting serves as an exciting technology with significant implications and applications in the field of tissue engineering. Here we review the work that has been undertaken in hopes of generating the recognized in-demand replacement breast tissue using different types of bioprinting. We then offer suggestions for future work needed to advance this field for both in vitro and in vivo applications.