3d-printed Poly-4-hydroxybutyrate (p4hb) Bioabsorbable Scaffolds Augmented With Autologous Processed Costal Cartilage Achieve Long Term Maintenance Of Nipple Projection With Biosimilar Mechanical Qualities
Xue Dong, MD, PhD1, Sabrina Shih, BA2, Carly Askinas, BS3, Nicholas Vernice, BA1, Kemal Sariibrahimoglu, PhD4, Skander Limem, PhD4, Jason Spector, MD1.
1Weill Cornell Medical College, New York, NY, USA, 2Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA, 3Tulane University School of Medicine, New Orleans, LA, USA, 4Tepha, Inc, Lexington, MA, USA.
Purposes: Nipple reconstruction is a vital part of breast reconstruction after total mastectomy. However, nearly all local autologous tissue techniques suffer from scar contracture and loss of neo-nipple projection. Costal cartilage (CC) has been reported to maintain projection in nipple reconstruction, yet it has not been widely adopted due to the excessively firm resultant nipple. Herein we propose using a 3D-printed bioabsorbable Poly-4-Hydroxybutyrate (3D-P4HB) scaffold loaded with fragmented CC to promote ingrowth of tissue that mimics the biomechanical properties of native nipples and protect the regenerated tissue from contracture as it matures. Methods: 3D-P4HB scaffolds (diameter: 1.0cm, height: 1.0cm) were fabricated and sterilized. Patient-derived CC (discarded from DIEP procedures) was either minced (1mm3) or zested (<0.2mm3) in sterile fashion to be used as a particulate infill within the scaffolds, achieving 10.4% and 7.6% porosity in minced and zested group 3D-P4HB respectively. Processed cartilage-filled 3D-P4HB scaffolds were subcutaneously implanted into nude rats using a CV flap technique. Additional groups include empty 3D-P4HB scaffolds, and non-scaffolded (naked) processed cartilage. The constructs were explanted at 1, 3, 6 and 12 months for gross, volumetrical, histological and biomechanical analysis. Four nipples per group/time point were analyzed. Results: All 3D-P4HB nipple reconstructions were well preserved in diameter and projection after 12 months in vivo when compared to the non-scaffolded groups (projection: minced 3D-P4HB: 100.0 ± 2.8%, zested 3D-P4HB: 93.6 ± 5.1%, empty 3D-P4HB: 93.3 ± 9.7%, minced naked: 53.0 ± 9.9%, zested naked: 52.7 ± 4.7%, respectively). An increase in tissue volume content was observed inside the scaffolds in both processed cartilage-filled 3D-P4HB groups and empty 3D-P4HB group overtime, due to cellular infiltration and tissue ingrowth through the pores and between cartilage pieces. However, the non-scaffolded (naked) group lost a significant amount of volume in the first 3 months (38% in minced and 26% in zested, p<0.05) due to lack of scaffold protection from skin retraction, and this smaller volume remained unchanged within 12 months. Newly formed fibrovascular cartilaginous tissue was noted in both processed cartilage-filled 3D-P4HB groups at 12 months. SEM images demonstrated the degradation of 3D-P4HB scaffolds with widespread pitting on the outer surface of the scaffold walls. The groups that most mimicked the elastic modulus of a native human nipple at 12 months were the empty scaffolded, zested CC scaffolded, and zested CC non-scaffolded neo-nipples (0.32 Mpa, 0.22 Mpa and 0.22 Mpa, respectively) Conclusions: Using 3D-P4HB scaffolds filled with autologous processed CC, we have engineered nipples that maintain their projection and volume over time, while simultaneously allowing for the maturation of an internal structure of fibrovascular cartilaginous tissue that biomechanically mimics that of native nipples. Because P4HB devices for soft tissue reinforcement have previously been cleared by the FDA and possess a long track record of safety, we believe that this novel 3D-P4HB nipple reconstruction scaffold has a great potential for clinical translation.
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