Histological Assessment of Wallerian Degeneration of the Rat Tibial Nerve Following Crush and Transection Injuries

Abstract

Background Wallerian degeneration (WD) following peripheral nerve injury (PNI) is an area of growing focus for pharmacological developments. Clinically, WD presents challenges in achieving full functional recovery following PNI, as prolonged denervation of distal tissues for an extended period of time can irreversibly destabilize sensory and motor targets with secondary tissue atrophy. Our objective is to improve upon histological assessments of WD. Methods Conventional methods utilize a qualitative system simply describing the presence or absence of WD in nerve fibers. We propose a three-category assessment that allows more quantification: A fibers appear normal, B fibers have moderate WD (altered axoplasm), and C fibers have extensive WD (myelin figures). Analysis was by light microscopy (LM) on semithin sections stained with toluidine blue in three rat tibial nerve lesion models (crush, partial transection, and complete transection) at 5 days postop and 5 mm distal to the injury site. The LM criteria were verified at the ultrastructural level. This early outcome measure was compared with the loss of extensor postural thrust and the absence of muscle atrophy. Results The results showed good to excellent internal consistency among counters, demonstrating a significant difference between the crush and transection lesion models. A significant decrease in fiber density in the injured nerves due to inflammation/edema was observed. The growth cones of regenerating axons were evident in the crush lesion group. Conclusion The ABC method of histological assessment is a consistent and reliable method that will be useful to quantify the effects of different interventions on the WD process.

Compound Motor Action Potentials During a Modest Nerve Crush

“…Among the histological preparations assessed in the present study, we were surprised to see the consistent extent of axon sparing, especially among the small myelinated fibers. Compared to our previous study, the sequential breakdown of the axoplasm prior to myelin sheath was very similar to the Wallerian degeneration observed 5 days post-crush in the rat tibial nerve (Kerns et al, 2020 ). In the present study, the sequence of the observed changes was a result of injury itself, rather than Wallerian degeneration.…”

Time-Dependent Proregenerative Effects of Exogenous Melatonin on the Transected Sciatic Nerve

“…Nerve transection results in histological changes of intrafascicular and extrafascicular structures (Turgut et al, 2005;Cosovic et al, 2017;Kerns et al, 2021). To study the neuroprotective effect of melatonin as a proregenerative substance we have observed the intrafascicular structures of the rat sciatic nerve with the emphasis on degenerating and regenerating nerve fibers, changes of the myelin sheath, connective tissue of the endoneurial compartment and the endoneurial tubes.…”

Leupeptin accelerates recovery after sciatic transection and repair, but not crush injuries in rats

“…3) with leupeptin after transection and repair, but not crush may have stemmed from the similarity of a crush injury of this magnitude to a segmental defect, which is more damaging than a transection due to the axon-less gap between proximal and distal segments that the recovering nerve needs to bridge. Recent studies have shed light on potential differences between outcomes and responses in peripheral nerve to transection and repair versus crush injuries [17,18], namely, there is an observable difference in inflammation, target muscle atrophy, and growth cone generation between the two injury types. Leupeptin, a calpain inhibitor, can halt Wallerian degeneration that is responsible for these processes described previously.…”