Peripheral Nerve Repair: Monitoring by Using Gadofluorine M–enhanced MR Imaging with Chitosan Nerve Conduits with Cultured Mesenchymal Stem Cells in Rat Model of Neurotmesis

Abstract

To observe the longitudinal changes of nerve repair in rats after tissue-engineered construct implantation at magnetic resonance (MR) imaging and to determine whether the enhanced nerve regeneration with use of tissue-engineered constructs could be monitored with gadofluorine M-enhanced MR imaging or nerve T2 relaxation time measurement. All experimental protocols were approved by the institutional Animal Use and Care Committee. Tissue-engineered constructs were prepared by seeding mesenchymal stem cells (MSCs) into chitosan nerve tubes. Thirty-six rats with sciatic nerve transection injury underwent nerve tube implantation with (n = 18) or without (n = 18) MSC seeding. Sequential T2 measurement, gadofluorine M-enhanced MR imaging, and sciatic function index measurement were performed over an 8-week follow-up period, with histologic assessments performed at regular intervals. T2 relaxation times and signal intensity at gadofluorine M-enhanced T1-weighted imaging were measured and were compared by using repeated-measures analysis of variance followed by the Student-Neuman-Keuls post-hoc test for multiple pairwise comparisons. Nerve T2 relaxation times and gadofluorine M enhancement, as well as functional changes, showed a similar time course. Nerves implanted with MSC-seeded tubes achieved slightly better functional recovery and enhanced nerve regeneration while showing a slower return to baseline T2 relaxation time and a more rapid decline in gadofluorine M enhancement compared with nerves implanted with chitosan tubes alone. T2 values of the distal portion of transected nerves showed a more rapid return to baseline level than did gadofluorine M enhancement. Peripheral nerve repair with use of tissue-engineered constructs can be monitored by using gadofluorine M-enhanced MR imaging and T2 relaxation time measurements. T2 relaxation time seems more sensitive than gadofluorine M-enhanced MR imaging for detecting nerve regeneration.