Biomechanical changes from long-term freezer storage and cellular reduction of tracheal scaffoldings

To determine structural biomechanical changes in tracheal scaffolds resulting from cellular reduction and storage at -80(o) C.

Laboratory-based study.

Forty-four rabbit tracheal segments were separated into four treatment groups: untreated (group A, control), cellular-reduced (group B), storage at -80(o) C followed by cellular reduction (group C), and cellular-reduced followed by storage at -80(o) C (group D). Tracheal segments were subjected to uniaxial tension (n = 21) or compression (n = 23) using a universal testing machine to determine sutured tensile yield load and radial compressive strengths at 50% lumen occlusion. Mean differences among groups for tension and compression were compared by analysis of variance with post-hoc Tukey-Kramer test.

The untreated trachea (group A) demonstrated mean yield strength of 5.93 (± 1.65) N and compressive strength of 2.10 (± 0.51) N. Following treatment/storage, the tensile yield strength was not impaired (group B = 6.79 [± 1.58] N, C = 6.21 [± 1.40] N, D = 6.26 [± 1.18]; P > 0.10 each). Following cellular reduction, there was a significant reduction in compressive strength (group B = 0.44 N [± 0.13], P < 0.0001), but no further reduction due to storage (group C = 0.39 N [± 0.10]; P = 0.97 compared to group B).

The data suggest cellular reduction leads to loss of compressive strength. Freezing at -80°C (either before, or subsequent to cellular reduction) may be a viable storage method for tracheal grafts.