Mechanical and biochemical mapping of human auricular cartilage for reliable assessment of tissue-engineered constructs

It is key for successful auricular (AUR) cartilage tissue-engineering (TE) to ensure that the engineered cartilage mimics the mechanics of the native tissue. This study provides a spatial map of the mechanical and biochemical properties of human auricular cartilage, thus establishing a benchmark for the evaluation of functional competency in AUR cartilage TE.

Stress-relaxation indentation (instantaneous modulus, E_in; maximum stress, σ_max; equilibrium modulus, E_eq; relaxation half-life time, t1/2; thickness, h) and biochemical parameters (content of DNA; sulfated-glycosaminoglycan, sGAG; hydroxyproline, HYP; elastin, ELN) of fresh human AUR cartilage were evaluated. Samples were categorized into age groups and according to their harvesting region in the human auricle (for AUR cartilage only).

AUR cartilage displayed significantly lower E_in, σ_max, E_eq, sGAG content; and significantly higher t1/2, and DNA content than NAS cartilage. Large amounts of ELN were measured in AUR cartilage (>15% ELN content per sample wet mass). No effect of gender was observed for either auricular or nasoseptal samples. For auricular samples, significant differences between age groups for h, sGAG and HYP, and significant regional variations for E_in, σ_max, E_eq, t1/2, h, DNA and sGAG were measured. However, only low correlations between mechanical and biochemical parameters were seen (R < 0.44).

In conclusion, this study established the first comprehensive mechanical and biochemical map of human auricular cartilage. Regional variations in mechanical and biochemical properties were demonstrated in the auricle. This finding highlights the importance of focusing future research on efforts to produce cartilage grafts with spatially tunable mechanics.