A Functional Evaluation of Cryopreserved Peripheral Nerve Autografts

ABSTRACT

This study compared the functional return following the repair of a 2.0-cm defect in the rat sciatic nerve with frozen (with or without treatment with a cryoprotectant, dimethyl sulfoxide [DMSO]) or fresh nerve grafts. In addition, a control group in which the defect was left ungrafted was evaluated. Recovery was assessed by functional studies (sensory testing, gait analysis, joint contractures, and tibialis anterior muscle weight), biochemical analysis (muscle hydroxyproline concentration), and histologic studies (axonal counts and fiber density). Sensory testing and gait analysis were not helpful because of cross-over innervation of the saphenous nerve and lack of recovery of the foot intrinsic muscles, respectively. The hind-limb contractures of the group with fresh nerve grafts (18° ± 3 °) were similar to those with DMSO-cryopreserved grafts (14° ± 4°). Both of these groups had statistically smaller contractures than the non-DMSO-cryopreserved group (45° ± 8°) and the gap control group (49° ± 6°), (p < 0.01). The tibialis anterior (TA) muscle-weight ratio (MWR) and the muscle-hydroxyproline-concentration ratio (MHPCR) showed a similar pattern, with no significant difference between the fresh (MWR, 0.5785 ± 0.068 and MHPCR, 1.527 ± 0.405) and DMSO-cryopreserved (MWR, 0.5675 ± 0.0989 and MHPCR, 1.660 ± 0.456) groups; both of these groups showed greater neurologic recovery when compared to the non-DMSO-cryopreserved (MWR, 0.3364 ± 0.0266 and MHPCR, 3.441 ± 0.300) and gap control (MWR, 0.2134 ± 0.0775 and MHPCR, 4.869 ± 2.351) groups. There was no significant difference between the axonal counts or fiber density in the graft segments in any of the three graft groups.

This animal model suggests that it may be possible for peripheral nerves to be stored using cryopreservation for staged autogenous construction or for banking of allogeneic grafts for tissue transplantation, in the event that they become clinically applicable.