Engineering of scaffold-free tri-layered auricular tissues for external ear reconstruction

Abstract

Objectives: Current strategies for external ear reconstruction can lead to donor site morbidity and/or surgical complications. Tissue-engineered auricular tissues may provide readily available reconstructive materials that resemble native auricular tissue, which is composed of a cartilaginous region sandwiched between two perichondrial layers. We previously developed scaffold-free bi-layered auricular tissues, consisting of a perichondrial layer and a cartilaginous layer, by cultivating chondrocytes and perichondrial cells in a continuous flow bioreactor. Here, we aimed to improve construct properties and develop strategies to engineer tri-layered auricular constructs that better mimic native auricular tissue.

Study design: Experimental study.

Methods: Different concentrations of insulin-like growth factor (IGF)-1 and insulin were supplemented during bioreactor culture to determine conditions for engineering bi-layered constructs. We also investigated two methods of engineering tri-layered constructs. Method 1 used Ficoll separation to isolate perichondrial cells, followed by the seeding of isolated perichondrial cells onto the opposing side of the bi-layered constructs. Method 2 involved the growth of the bi-layered constructs in osteogenic culture medium.

Results: The combination of 10 nM IGF-1 and 100 nM insulin led to increased collagen content in the engineered bi-layered constructs. For developing tri-layered constructs, method 2 yielded thicker constructs with better mechanical and biochemical properties compared to method 1. In addition, the presence of the perichondrial layers protected the engineered constructs from tissue calcification.

Conclusion: Auricular tissues with a biomimetic microstructure can be created by growing chondrocytes and perichondrial cells in a continuous flow bioreactor, followed by cultivation in osteogenic medium.

Level of evidence: NA Laryngoscope, 129:E272-E283, 2019.

Keywords: External ear reconstruction; auricular cartilage; perichondrium; tissue engineering; tri-layered structure.