title: Injectable chondroplasty: Enzymatic reshaping of cartilage grafts.
abstract: OBJECTIVE
  To develop an injection-based enzymatic technique that selectively softens cartilage tissue for reshaping cartilaginous structures in the head and neck.
  
  
  METHODS
  Two groups were formed using fresh rabbit ears: (1) whole rabbit ear group; (2) composite graft group (2.5mm×3.0cm specimens sectioned from the central region of the pinna). Subperichondrial injections using three enzymes (hyaluronidase, pronase, and collagenase II) in sequence were performed for the experimental specimens from both groups. In the control specimens, phosphate buffered saline was injected in a similar fashion. The whole ear specimens were then photographed while held upright in the anatomical vertical position to evaluate for buckling, which corresponds to the integrity of the cartilage. In addition, backlight photography was performed for all specimens to further evaluate the effect of the enzymes, such that increased light intensity represents increased cartilage digestion.
  
  
  RESULTS
  The application of the digestive enzymes resulted in marked reduction of cartilage tissue matrix resiliency, while preserving overlying skin layers. Enzymatically treated whole pinnae buckled at the site where enzymes were delivered. Backlit images revealed increased local light intensity at the regions of digestion. There was no obvious destruction of the overlying skin upon visual inspection.
  
  
  CONCLUSIONS
  This study demonstrates the feasibility of injectable chondroplasty as a potential alternative method to conventional surgery for auricular cartilage reshaping. Sequential injection of hyaluronidase, pronase, and collagenase II into the subperichondrial space can be performed to digest and soften cartilage structure with minimal involvement of surrounding tissue. Future studies will need to include chondrocyte viability testing and optimization of delivery techniques.
authors.affiliation: Division of facial plastic surgery, department of otolaryngology, head and neck surgery, university of California Irvine, 101, The City Drive, CA 92668 Orange, United States; Beckman Laser institute and medical clinic, university of California Irvine, 1002, Health Sciences Road East, CA 92612 Irvine, United States.
authors.forename: J R
authors.initials: JR
authors.lastname: Gandy
authors.affiliation: Division of facial plastic surgery, department of otolaryngology, head and neck surgery, university of California Irvine, 101, The City Drive, CA 92668 Orange, United States; Beckman Laser institute and medical clinic, university of California Irvine, 1002, Health Sciences Road East, CA 92612 Irvine, United States.
authors.forename: A
authors.initials: A
authors.lastname: Foulad
authors.affiliation: Beckman Laser institute and medical clinic, university of California Irvine, 1002, Health Sciences Road East, CA 92612 Irvine, United States; Department of radiation oncology, Epic Care, 400, Taylor Boulevard, Suite 102, CA 94523 Pleasant Hill, United States.
authors.forename: K K
authors.initials: KK
authors.lastname: Chao
authors.affiliation: Division of facial plastic surgery, department of otolaryngology, head and neck surgery, university of California Irvine, 101, The City Drive, CA 92668 Orange, United States; Beckman Laser institute and medical clinic, university of California Irvine, 1002, Health Sciences Road East, CA 92612 Irvine, United States; Department of Biomedical Engineering, university of California Irvine, CA 92612 Irvine, United States. Electronic address: bjwong@uci.edu.
authors.forename: B J F
authors.initials: BJF
authors.lastname: Wong
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D054644:Ear Auricle / Q000473:pathology*; D004425:Ear Cartilage / Q000637:transplantation*; D005240:Feasibility Studies; D006821:Hyaluronoglucosaminidase / Q000008:administration & dosage*; D007279:Injections, Subcutaneous / Q000379:methods; D020784:Matrix Metalloproteinase 8 / Q000008:administration & dosage*; D010781:Photography; D011402:Pronase / Q000008:administration & dosage*; D011817:Rabbits; D019651:Plastic Surgery Procedures / Q000379:methods; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D006821:Hyaluronoglucosaminidase; D011402:Pronase; D020784:Matrix Metalloproteinase 8
keywords: Cartilage; Collagen; Composite grafts; Enzymatic digestion; Shape change