Engineering autogenous cartilage in the shape of a helix using an injectable hydrogel scaffold

Objective: Previous successful efforts to tissue engineer cartilage for an auricle have used an immunocompromised nude mouse xenograft model. Subseque nt efforts in an immunocompetent autogenous animal model have been less suc cessful because of an inflammatory response directed against the foreign sc affold polymer used to provide an auricular shape. Ne studied an alternativ e polymer material and surgical technique to engineer autogenous cartilage in the shape of a human ear helix using injectable hydrogel scaffolding, Pl uronic F-127 (polyethylene oxide and polypropylene oxide). Subject: Yorkshi re swine. Material and Methods: Fresh autogenous chondrocytes were suspende d in a biodegradable, biocompatible co-polymer hydrogel, Pluronic F-127, at a concentration of 3 x 10(7) cells/mL, To support the contour of the impla nt, a skin fold channel in the shape of the helix of a human ear was create d in the skin in three sites on the ventral surface of the animal The cell- hydrogel suspension was injected through the skin fold channel. For control s, injections were made into identical channels using either cells alone or the Pluronic F-127 without cells. After 10 weeks, the specimens mere excis ed and examined both grossly and histologically, Results: Grossly, all impl ants retained a helical like shape. Excised specimens possessed flexible ch aracteristics consistent with elastic cartilage. The specimens could be fol ded and twisted and on release of mechanical pressure would instantly retur n to the original shape. Histological evaluation of the implants using H&E, Safranin O, trichrome blue, and Verhoeff's stains demonstrated findings co nsistent with mature elastic cartilage, Control injection of hydrogel alone demonstrated no evidence of cartilage formation and control injection of c hondrocytes alone showed evidence only of disassociated elastic cartilage. Conclusion: Injection of autologous porcine auricular chondrocytes suspende d in a biodegradable, biocompatible hydrogel of Pluronic F-127 resulted in the formation of cartilage tissue in the approximate size and shape of a hu man ear helix. This preliminary method extends the concept of auricular tis sue engineering from an immunocompromised xenograft animal model to an immu nocompetent autologous animal model.