Functional and Morphological Assessment of a Standardized Rat Sciatic Nerve Crush Injury with a Non-Serrated Clamp

Abstract

Peripheral nerve researchers frequently use the rat sciatic nerve crush as a model for axonotmesis. Unfortunately, studies from various research groups report results from different crush techniques and by using a variety of evaluation tools, making comparisons between studies difficult. The purpose of this investigation was to determine the sequence of functional and morphologic changes after an acute sciatic nerve crush injury with a non-serrated clamp, giving a final standardized pressure of p = 9 MPa. Functional recovery was evaluated using the sciatic functional index (SFI), the extensor postural thrust (EPT) and the withdrawal reflex latency (WRL), before injury, and then at weekly intervals until week 8 postoperatively. The rats were also evaluated preoperatively and at weeks 2, 4, and 8 by ankle kinematics, toe out angle (TOA), and gait-stance duration. In addition, the motor nerve conduction velocity (MNCV) and the gastrocnemius-soleus weight parameters were measured just before euthanasia. Finally, structural, ultrastructural and histomorphometric analyses were carried out on regenerated nerve fibers. At 8 weeks after the crush injury, a full functional recovery was predicted by SFI, EPT, TOA, and gait-stance duration, while all the other parameters were still recovering their original values. On the other hand, only two of the histomorphometric parameters of regenerated nerve fibers, namely myelin thickness/axon diameter ratio and fiber/axon diameter ratio, returned to normal values while all other parameters were significantly different from normal values. The employment of traditional methods of functional evaluation in conjunction with the modern techniques of computerized analysis of gait and histomorphometric analysis should thus be recommended for an overall assessment of recovery in the rat sciatic nerve crush model.

Adenoviral GDNF gene transfer enhances neurofunctional recovery after recurrent laryngeal nerve injury

“…37,38 This process induces Sunderland second-degree injury (axonotmesis), which involves injury to the axon such that Wallerian degeneration occurs distal to the injury, with only rare and minor features of first-and thirddegree injury. 39 This model is ideal for exploring the effects of remotely injected viral vectors, providing an intact nerve for injection and retrograde axonal transport of virus.…”

“…MNCV for the injured nerve is a commonly used physiological measure to evaluate peripheral nerve function in the rat nerve injury model. 37,38,41 In this study, the latency of compound muscle action potential from the TA muscle was recorded, and MNCV was calculated from the latencies of action potential and distance between the two stimulating points. Control animals injected with or without AxCALacZ displayed a markedly slowed MNCV that did not change between 2 and 4 weeks after injury.…”

Evaluation of biodegradable electric conductive tube-guides and mesenchymal stem cells

“…Also, it is considered by the scientific bibliography that rats without sciatic nerve injury withdraw their paws from the hotplate within 4.3 s or less [9,17,31,33] . If there was no paw withdrawal after 12 s, the animal was assigned the maximal WRL of 12 s and the heat stimulus was removed to prevent tissue damage [34][35][36] . For sciatic functional index (SFI), a confined walkway measuring 42 cm long and 8.2 cm wide with a dark shelter at the end (own fabrication) that the rats cross was used.…”

“…The histological nerve preparation followed the previously reported protocol [3,9,17,25,31,33,35] and a systematic random sampling and D-disector were adopted [41][42][43][44] . At the end of the healing period tested (week 20), tibialis anterior (TA) muscles of all experimental (PVA, PVA-CNTs, PVA-PPy, Graft, End-to-End, and PVA-CNTsMSCs) and Control (no lesion) groups were collected, and the tissue samples were fixed in 10% buffered formalin, routinely processed, dehydrated and embedded in paraffin wax.…”

Future Perspectives in Nerve Repair and Regeneration

“…In addition to these models, various large animal models have been employed including rabbits, sheep, pigs, and primates because several authors believe that the translation to clinical application may benefit from a preclinical study on large animal nerves since the regeneration process of nerves in large animals is more similar to humans (Fullarton, Lenihan, Myles, & Glasby, 2000). Accordingtothelocalizationofthelesion,untilrecently,mostperipheral nerveregenerationstudieshadbeenmainlycarriedoutontheratsciaticnerve model, primarily because it is the largest peripheral nerve (Baptista et al, 2007;Luis et al, 2007;Varejao et al, 2004). However, since most of the human peripheral nerve injuries affect the upper extremity, the necessity ofanexperimentalmodelclosertoclinicalinterestsisrequired.Indeed,recent years have shown an increasing interest toward the employment of major forelimb nerves Papalia, Tos, Scevola, Raimondo, & Geuna, 2006;Sinis et al, 2008;Tos et al, 2009).…”