Vascularized tissue-engineered ears.

Abstract

BACKGROUND: A paucity of appropriate regional and local matching tissue can compromise the reconstruction efforts in areas of the body that require specialized tissue. The current study uses techniques of vascular prefabrication, tissue culturing, and capsule formation to form a vascularized ear construct that is reliably transferable on its blood supply. METHODS: Thirty male Wistar rats (250 to 350 g) were anaesthetized. An incision was made over the right lower abdominal wall. A pocket was formed by blunt dissection just below the panniculus carnosus. A separate incision was made over the right femoral vessels, which were then isolated and transected distally. The vessels were transposed in a subcutaneous plane to the abdominal wound. A silicone mold in the shape of an ear (2 x 1.5 cm) was placed over the transposed vessels in the abdominal wound pocket. The wounds were closed. Auricular cartilage was minced, washed, and cultured. After 14 days, the chondrocyte culturing was complete and a vascularized capsule based on the incorporated, transposed femoral vessels was formed. The abdominal incision was then reopened, an incision was made in the lateral capsule, and the cultured chondrocytes were introduced into the molded capsule. Study groups included capsules filled with chondrocytes only, chondrocytes and a fibrin glue carrier, and the fibrin glue only. The capsule was closed and the wounds sutured. The prefabricated, prelaminated construct was isolated on its vascular pedicle 14 days later and traversed microsurgically to the contralateral leg vessels. Histologic analysis was performed. RESULTS: All 30 capsules were completely vascularized and could be reliably isolated and transferred microsurgically on the transposed femoral vessels. The pedicle, being incorporated directly into the capsule, provided the dominant blood supply to the construct. None of the capsules with the fibrin glue only retained any shape and all were devoid of cartilage. Similarly, there was no evidence of retained cartilage in the capsules filled with chondrocytes alone. All capsules with the chondrocytes and the fibrin carrier had mature shaped cartilage preserved. External molds were required to maintain the shape of the ear. Extrusion, although almost uniform in the group with external molds, did not interfere with the end construct shape or vascularity. When molds were used, four of six had excellent maintenances of shape and two of six had only minor superior pole deformation. All constructs were reliably transferred as free flaps. CONCLUSIONS: The authors have shown that transposing a vascular pedicle to a subcutaneously placed silicone block will result in a vascular capsule that can be mobilized and transferred based solely on the pedicle. Although the capsule provides vascularity to the chondrocytes, the cultured cartilage will fill the shape of the silicone mold only if an appropriate carrier such as fibrin glue is used and an external mold is applied.