Functional evaluation outcomes correlate with histomorphometric changes in the rat sciatic nerve crush injury model: A comparison between sciatic functional index and kinematic analysis

PLoS One. 2018 Dec 12;13(12):e0208985. doi: 10.1371/journal.pone.0208985. eCollection 2018.

Abstract

Elucidating whether there is a correlation between biomechanical functions and histomorphometric data in the rat sciatic nerve crush injury model would contribute to an accurate evaluation of the regeneration state without sacrificing animals. The gold standard for functional evaluation is the sciatic functional index (SFI) despite there being intrinsic shortcomings. Kinematic analysis is considered a reliable and sensitive approach for functional evaluation, most commonly assessed as ankle angle at various phases of a gait cycle. Studies utilizing the toe angle for functional evaluation are scarce, and changes in the toe angle following surgery remain unknown. The present study assessed correlations of ankle angle, toe angle and SFI with histomorphometric data, aiming to determine which parameters most accurately reflect changes in histomorphometric data over time. Six Lewis rats were designated as the control group. 30 animals received surgery, six of them were randomly selected on the first, second, third, fourth, and sixth week after surgery for measurements of ankle and toe angles in the "toe-off" phase, and for evaluation of SFI. Histomorphometric analysis were also performed, to determine the number of myelinated nerve fibers, diameters of myelinated nerve fibers, axon diameters, and myelin sheath thicknesses. Furthermore, we investigated changes in ankle angle, toe angle, SFI, and histomorphometric data over time, as well as correlations between ankle angle, toe angle, and SFI with histomorphometric data. The results revealed that changes in SFI, ankle angle, and toe angle highly correlate with histomorphometric data in the rat sciatic nerve crush injury model. Toe angle reflected changes in histomorphometric data with time more precisely than ankle angle or SFI did, and ankle angle was a better prognostic parameter than SFI.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / physiology
  • Biomechanical Phenomena*
  • Disease Models, Animal
  • Male
  • Myelin Sheath / pathology
  • Myelin Sheath / physiology
  • Nerve Fibers, Myelinated / pathology
  • Nerve Fibers, Myelinated / physiology
  • Rats
  • Rats, Inbred Lew
  • Recovery of Function*
  • Sciatic Nerve / injuries*
  • Sciatic Nerve / pathology
  • Tarsus, Animal / pathology
  • Tarsus, Animal / physiology
  • Toes / physiology

Grants and funding

This study was supported by Japan Society for the Promotion of Science (JSPS, http://www.jsps.go.jp/index.html) KAKENHI Grant-in-Aid for Young Scientists (B) (number 17K13052) to AI and JSPS KAKENHI Grant-in-Aid for Scientific Research (B) (number 26282154) to TA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.