Plastic Surgery Research Council
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PSRC 60th Annual Meeting
Program and Abstracts

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Patient-Specific Tissue Engineered Constructs for Ear Reconstruction: Long Term (6 month) Results
Benjamin P. Cohen, BS1, Rachel C. Hooper, MD2, Jennifer Puetzer, PhD1, Rachel Nordberg, MEng1, Ope A. Asanbe, MD2, Peipei Zhang, PhD2, Lawrence J. Bonassar, PhD1, Jason A. Spector, MD, FACS2.
1Cornell University, Ithaca, NY, USA, 2Weill Cornell Medical College, New York, NY, USA.

PURPOSE: The current gold standard for reconstruction of pediatric microtia is autologous costal cartilage reconstruction. This method is limited due to morbidity at the donor site, failure to match auricular cartilage properties, and difficulty accurately recreating the ear morphology of the individual patient. We have previously demonstrated the capacity to fabricate high fidelity patient-specific ear constructs using digital photogrammetry and CAD/CAM techniques, and that these constructs formed auricular cartilage when implanted in vivo for up to 3 months. We have now applied the same methods for constructs implanted in vivo for 6 months.
METHODS: A 5 year-old human female ear was imaged using three-dimensional photogrammetry, processed into a continuous surface, and embedded into a virtual block, which was printed as a 7-piece mold. A combination of bovine auricular chondrocytes and 10 mg/mL type I collagen was injection molded to form hydrogel ear constructs with a cell density of 25 x 106 cells/mL. Constructs were subcutaneously implanted into the dorsa of nude rats and harvested after 6 months. Post-harvest, constructs were analyzed by histological, biochemical, and biomechanical testing. Statistical analysis was performed using one-way ANOVA or one-way ANOVA by ranks, with a Tukey or Dunn’s, respectively, pairwise comparison and p<0.05 indicating statistical significance.
RESULTS: After 6 months of implantation, engineered auricular constructs demonstrated sustained ear morphology, formation of auricular neocartilage, and mechanical and biochemical properties similar to those of native auricular cartilage. Constructs maintained overall aesthetic fidelity and size upon gross inspection. Safranin O staining for GAG content and Verhoeff staining for elastin displayed the generation of a perichondrial surface layer, a proteoglycan rich core, and elastin fiber organization. Mechanically, the equilibrium modulus reached levels similar to those of native auricular cartilage within 3 months with reduced variation after 6 months. Proteoglycan and collagen content was found to not be statistically different from native bovine auricular cartilage for constructs implanted for 3 and 6 months.
CONCLUSIONS: High fidelity constructs composed of auricular cartilage were successfully produced following 6 months of in vivo subcutaneous growth of collagen hydrogels seeded with auricular chondrocytes. These engineered constructs maintained size and aesthetic quality and also displayed similar structural organization, matrix composition, and mechanical properties to native tissue. This injection molding approach demonstrates the feasibility for fabrication of patient-specific, high fidelity tissue engineered constructs for patients suffering from microtia or traumatic ear injury. Further work using human auricular chondrocytes is required to show translation of this technology, and alternative cell sources such as mesenchymal stem cells will be investigated.


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