Stiffness and viscoelasticity of human lung tissue unaltered by freeze-thawing

Abstract

Rationale: The biomechanics of human lung tissue is strongly influenced by the composition of the extracellular matrix (ECM). The effect of storage (freezing and subsequent thawing) on biomechanics and ECM in lung tissue is as yet not known. The aim of this study was to evaluate if storing human lung tissue frozen or frozen in Tissue-Tek® O.C.T.™ changed its mechanical properties. Methods: Pieces of human explanted lung (nondiseased n=4, COPD IV n=3 and pulmonary fibrosis n=1) were stored cooled (4°C), frozen fresh, or frozen in Tissue-Tek® O.C.T.™ (-20°C) for 24 to 48h. Tissues were warmed to room temperature, washed 3x with HBSS and mechanical properties assessed using a low load compression tester measuring stiffness and viscoelastic stress relaxation. Measurements were obtained from 3 locations per tissue piece with 1 piece per storage method per donor. Results: No differences in stiffness and stress relaxation were found between the fresh tissue and tissue frozen either fresh or in O.C.T. (Table 1). Conclusions: The stiffness and viscoelasticity of human nondiseased and diseased lung tissue were unaltered by freeze-thawing. These findings open up the possibility to use human lung tissue stored in biobanks in order to study the involvement of ECM and biomechanics in lung disease.