Hyaluronic Acid Dermal Filler Promotes Cartilage Reshaping in Rabbit Ears

Background: Neonatal ear is more malleable and soft, allowing the correction of deformities by using external molding. This is mainly attributed to high concentration of the proteoglycan aggregate and hyaluronic acid. In this study, HA dermal filler was injected in rabbit ear as a long acting HA source to investigate the biological impact of HA in reshaping the ear cartilage. Materials and Methods: Ears of twelve rabbits were divided into 4 groups. Control group was the left ears of 6 animals which were left intact. Group 2 was the right ears of the same animals, which received saline solution injection. Group 3 was the left ears of the other 6 animals, which were given 1 mL of HA. Group 4 was the right ears of them, which were given 2 mL of HA in both sites of the ear. All ears were folded and splinted for 4 weeks. Then, the angle of each ear was calculated. Following an additional 4 weeks, a cartilage biopsy was taken for histological examination. Results: The ear angles did not show any statistical difference at week 4. There was a significant difference among the groups at the 8th week. In the 3rd and 4th groups, mean angles were higher than the group 1 and group 2. Thickening in the cartilage and ectopic cartilage formation was observed in the contact areas to hyaluronic acid. Significant difference was also found between the peak and mean cartilage thicknesses. Conclusion: HA dermal filler can stimulate cartilage regeneration by increasing the synthesis of extracellular matrix and chondrogenesis especially where it is in direct contact with the ear cartilage. No Level Assigned: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.