The Laryngoscope V C 2014 The American Laryngological, Rhinological and Otological Society, Inc. Angiogenesis in Costal Cartilage Graft Laryngotracheoplasty: A Corrosion Casting Study in Piglets Lukas H. Kus, MD, MSc; Jaina Negandhi, MSc; Michael C. Sklar, MD; Antoine Eskander, MD; Marvin Estrada, BSc; Robert V. Harrison, PhD, DSc; Paolo Campisi, MD, MSc, FRCSC; Vito Forte, MD, FRCSC; Evan J. Propst, MD, MSc, FRCSC Objectives/Hypothesis: To investigate the timing and degree of angiogenesis following anterior costal cartilage graft laryngotracheoplasty in an animal model. Study Design: Randomized controlled animal model. Methods: Twelve pigs were included in this study. Three control pigs were perfused with intravascular methyl methac- rylate, and overlying tissue was corroded with potassium hydroxide and hydrochloric acid, leaving only a cast of vessels. Nine pigs underwent anterior costal cartilage graft laryngotracheoplasty and were survived for various lengths of time (3 for 48 hours, 3 for 10 days, 3 for 3 weeks) prior to corrosion casting. Transition zones between trachea and cartilage graft as well as the graft itself were analyzed for signs of angiogenesis (budding, sprouting, intussusception) and hypoxic or degenerative vessel features (extravasation, corrugation, circular constriction) using scanning electron microscopy. Results: Angiogenesis peaked above control levels 48 hours after laryngotracheoplasty (P <.0001) and decreased 10 days and 3 weeks following surgery (P <.001, P <.0001, respectively) while remaining elevated above control levels (P <.0001, P <.005, respectively). There was no difference in hypoxic or degenerative features across surgical and control groups. Sprouting angiogenesis dominated over intussusception preoperatively (P <.0001) and 3 weeks following surgery (P <.05). However, there was no difference in type of angiogenesis 48 hours and 10 days following surgery. Conclusion: Angiogenesis peaked by 48 hours following costal cartilage graft laryngotracheoplasty and persisted for at least 3 weeks (although decreased) after surgery in this animal model. Hypoxic or degenerative processes did not appear to play a role in tracheal revascularization during the first 3 postoperative weeks. Key Words: Angiogenesis, laryngotracheoplasty, animal model, corrosion casting, costal cartilage graft. Level of Evidence: N/A. Laryngoscope, 124:2411–2417, 2014 INTRODUCTION Laryngotracheoplasty (LTP) is an airway recon- structive procedure for the treatment of subglottic steno- sis. LTP can be categorized as expansion of the subglottic framework using cartilage or resection of a stenotic segment. Expansion techniques usually involve placement of an autologous costal or thyroid ala cartilag- inous graft. Although LTP success rates can be as high as 90%, 1 restenosis and failure to decannulate can be devastating for patients when surgery is not successful. Approximately one in 50 rib grafts necrose following LTP. 1 Revascularization is believed to be an important factor in maintaining the viability of a cartilage graft and therefore in preventing restenosis. 2,3 The exact mechanism and timing of angiogenesis in laryngotra- cheal wound healing is poorly understood. Corrosion casting allows for the study of vascular structures. A liquid plastic polymer is injected into an organ’s blood supply and allowed to harden. Overlying tissues are then corroded and the resulting vascular cast can be analyzed using scanning electron microscopy (SEM). The purpose of this study was to employ the technique of corrosion casting to investigate angiogene- sis following anterior costal cartilage graft laryngotra- cheoplasty. We hypothesized that there would be a critical period of angiogenesis shortly after surgery that would decline over the ensuing weeks. MATERIALS AND METHODS Animals This study was approved by the Animal Care Committee at the Hospital for Sick Children. Twelve Yorkshire piglets, mean age 7.0 6 0.95 weeks (range 6–8 weeks) and mean weight Additional Supporting Information may be found in the online version of this article. From the Department of Otolaryngology–Head and Neck Surgery (L.H.K., J.N., M.C.S., A.E., R.V .H., P .C., V .F ., E.J.P .), Canada; and the Laboratory Animal Services (M.E.), The Hospital for Sick Children, University of Toronto, Toronto, Canada. Editor’s Note: This Manuscript was accepted for publication January 6, 2014. Presented at the American Society of Pediatric Otolaryngology Annual Meeting in Arlington, Virginia, U.S.A, April 25–28, 2013. This work was funded by a Hospital for Sick Children Surgical Services Innovation Grant. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Dr. Evan J. Propst, Department of Otolar- yngology–Head and Neck Surgery, 6th Floor, Burton Wing, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8, Canada. E-mail: evan.propst@utoronto.ca DOI: 10.1002/lary.24597 Laryngoscope 124: October 2014 Angiogenesis in Costal Cartilage Graft Laryngotracheoplasty 2411