HISTOLOGICAL AND FUNCTIONAL STUDY OF LASER AND LATEX TREATMENTS ON CRUSHED SCIATIC NERVE

Abstract

This study evaluated the effects of low‐level laser (LLL 15J/cm2, 780nm) associated or not to natural latex (F1 protein − 0,1%) on the crushed sciatic nerve (15 kgf, axonotmesis, left nerve). We used 36 male Wistar rats (200g) divided into 6 groups (n = 6): C ‐ control; E ‐ exposed nerve; I ‐injured nerve; L – LLL; F1 ‐ F1 protein; LF1 ‐ LLL and F1. The functional analysis of mechanical allodynia (von Frey), paw pressure (forceps test) and grip strength (Grip strength meter) was performed after 1, 7, 14, 28, 56 and 180 days of nerve injury. The histological analyses were assessed after 15, 57 and 181 days.Mechanical allodyniaThe non‐injured paw (right) did not differ in all groups studied. The left paw (injured) revealed a higher initial value in Groups I, LLL, LLL + P1 and P1 compared to groups C and E these values decreased in subsequent periods. After seven days the F1 values were very close to the C and E while this effect was observed in the other groups after 14 days. Group I had the highest value for this test after 180 days.Paw pressureThe right paw (non‐injured) showed similar values during the 180 days of the experiment. The left paw (injured) showed higher initial values in groups I, LLL, F1, LLL+ F1 compared to groups C and E. Baseline values reduction was observed after 7 days in the LLL group and after 14 days in the group LLL + F1. After 180 days all groups had similar values, with F1 group presenting the lowest value.Grip StrengthDuring 180 days there was an increase in the values in all groups. The initial values of groups C and E were higher compared to the other groups up to 56 days. At the end of the experiment (180 days) P1 and LLL + F1 groups showed the highest values for the test.Histological analysisGroups C and E showed normal characteristics. Injured groups (I, LLL, LLL + P1 and P1) reveal reduced number and size of nerve fibers, mainly after 15 and 56 days. In the course of time the injured nerve morphology improved with the P1 and LLL+P1 groups showing the best results among the treated groups. In the 180‐day period, P1 and LLL + P1 groups showed similar morphology to groups C and E. The functional and histological analyzes showed improvement after damage in all injured groups. The functional tests showed that the LLL was more effective in reducing pain (paw pressure) after 7 days, probably due to the anti‐inflammatory property of the laser. LLL + P1 treatment reduced pain after 14 days and improved of grip force at long‐term (180 days). F1 showed the best results for mechanical allodynia after 7 days, paw pressure after 180 days and grip force after 180 days. Histology showed promising results from the use of F1 with or without association with the LLL in accelerating nerve regeneration.Support or Funding InformationNerve injury, Low‐level laser, Latex protein, functional tests, morphologic analyses