Abstract: Autologous Human Auricular Chondrocytes: What Are the “Rights” of Passage?

Abstract

INTRODUCTION: There has been an increasing interest in cartilage engineering given the significant shortcomings associated with current autologous reconstructive options for auricular deformities. A major obstacle in the engineering of human auricular scaffolds is the availability of a sufficient number of autologous human chondrocytes. A clinically obtainable amount of auricular tissue (i.e. 1 gram) only yields approximately 10 million cells, where 25 times this amount is needed for the fabrication of a full-scale pediatric ear. It is known that repeated passaging of chondrocytes leads to de-differentiation and loss of the chondrogenic potential. However, little to no data exists regarding the ideal number of times that human auricular chondrocytes can be passaged in a manner that both maximizes the cellular expansion while minimizing dedifferentiation. METHODS: Human auricular chondrocytes (HAuCs) were isolated from discarded otoplasty specimens. The HAuCs were then expanded and cells from passage 3, 4, and 5 were encapsulated into type I collagen 8mm diameter disc hydrogels with a cell density of 25 million cells/mL. The constructs were then implanted subcutaneously in the dorsa of nude mice, and harvested after 1 and 3 months for analysis. RESULTS: Constructs containing passage 3, 4, and 5 chondrocytes all maintained cylindrical geometry. After 3 months, passage 3 and 4 discs on average contracted 24.22% and 25.00%, respectively. Interestingly, passage 5 discs on average contracted only 19.97%, which was significantly less. Regardless of the passage number of the chondrocytes, all constructs developed a white cartilage like appearance and had flexibility similar to native human auricular cartilage. Histologic and biomechanical analyses are pending. CONCLUSION: With the analysis performed thus far, there appears to be no difference in the chondrogenic capacity between auricular chondrocytes expanded out to passage 3, 4, or 5. In fact, passage 5 constructs experienced significantly less contraction that passage 3 and 4. Future work will consist of further analyzing the biochemical, histological, and mechanical properties of the cartilage produced from the various passages. These data indicate that later passaged human auricular chondrocytes have the potential to be used for cartilage engineering and help us to overcome the current cell-sourcing barrier we face.