Background Reconstruction of the external ear is one of the most challenging problems in the field of plastic and reconstructive surgery. Surgical options for microtia involve harvesting costal cartilage, sculpting an ear shape, and implanting the construct subcutaneously or under a fascial flap. This may involve several surgeries to complete and often results in only a crude replication of the ear. Another approach for auricle reconstruction is to implant a porous polyethylene strut that simulates the contours of the ear. This plastic material is inflexible and only available in a predetermined shape and size. A non-degradable flexible and porous polyvinyl alcohol-alginate gel in combination with tissue engineering of cartilage using human naso-septal chondrocytes could be a possible alternative for auricle reconstruction.
Materials and Methods All actions were approved by the IACUC and IRB committees. Nasal septum cartilage from a 30 year old female patient was collected from the OR and taken to the laboratory. The cartilage was finely minced and digested for 16 hours with 0.08% collagenase. Cells were filtered, centrifuged, washed in phosphate buffered saline and placed in culture to expand cell numbers. After expansion, cells were mixed with a 2% sodium alginate solution resulting in a final cell concentration of 60x10^6 cells per milliliter. The cell-alginate mixture was injected into porous polyvinyl alcohol gel discs (n=6, Image A) and alginate gel cross-linking was achieved by immersion in calcium chloride. Polyvinyl alcohol-alginate constructs without cells (n=6) and chondrocyte-alginate nodules (n=6) were also done for this study. Constructs were washed in media and placed in nude mice dorsum for 6 weeks.
Results No signs of extrusion were noted at the time of explantation. Harvested samples were surrounded by a thin fibrous capsule that was easily removed. All of the constructs had a similar appearance to native cartilage on histological analysis, shown by Toluidine Blue (Image B) and Safranin-O stains (Image C). The interface between the polyvinyl alcohol gel and neocartilage was in close contact without the presence of fibrous tissue or inflammatory cells. Both micro and macropores of the non-degradable gel maintained their original dimensions. Specimens stained positive for collagen type II (Image D).
Conclusions We have demonstrated tissue engineering of cartilage with human naso-septal chondrocytes in vivo using a novel porous polyvinyl alcohol-alginate gel hybrid. Both gels can be shaped into any predetermined size and shape, such as the human auricle (Image E). Further studies using flexible gels with autologous chondrocytes should be carried out considering that autografts and allografts used for the reconstruction of the human auricle are associated with various degrees of success. We believe this material will be conducive to functional cartilage production due to its porosity and will improve the surgical outcome due to its flexibility.