Effect of cryopreservation on the biomechanical properties of the intervertebral discs

Abstract

Intervertebral Disc (IVD) allograft transplantation is presented to be a practical treatment of severe Degenerative Disc Disease (DDD). Limited availability of fresh allograft tissues necessitate the establishment of tissue banking for long-term storage. However, the effects of the cryopreservants on the mechanical properties of the IVD remains unknown. We hypothesize that the appropriate use of cryopreservants can preserve the mechanical properties of the IVD. In this study porcine discs were cryopreserved in different cryopreservative agent (CPA) concentration following a stepwise freezing protocol. After four weeks of storage in liquid nitrogen, dynamic viscoelastic properties of the IVDs were tested using uniaxial compression at different frequencies. Compared to fresh IVDs, no significant differences were found in the elastic modulus (E'), viscous modulus (E') and loss tangent (E'/E') in the discs cryopreserved with 0-20% CPA. However, cryopreservation at 20% CPA mixture resulted in lower E' and E'. Our data suggest properly cryopreserved IVD is able to maintain both elastic and viscous characteristics and distribute loads as of a normal IVD.