Transcardial perfusion versus immersion fixation for assessment of peripheral nerve regeneration.

Accurate assessment of peripheral nerve regeneration requires fixation techniques that preserve tissue in a natural state with minimal artifact. While transcardial perfusion fixation is accepted as the gold standard for tissue fixation, the less cumbersome approach of immersion fixation has been criticized for introducing artifacts in brain tissue. We investigated whether immersion fixation increased artifact compared to perfusion fixation in the rat sciatic nerve. Eighteen Lewis rats were randomized into three groups: glutaraldehyde immersion fixation; glutaraldehyde transcardial perfusion; and paraformaldehyde transcardial perfusion. All animals underwent sciatic nerve transection and repair followed by tissue harvest and fixation at three weeks. Qualitative assessment of neural architecture and histological features was followed by quantitative analysis of nerve regeneration parameters. Outcome measures included quantitative histomorphometry, analysis of axon/myelin ratios, assessment of fiber distributions, and ultrastructural analysis. No qualitative or quantitative differences were observed with immersion fixation when compared to the transcardial perfusion fixation methods. Immersion fixation is a valid method for assessment of peripheral nerve regeneration in a rat model.