The study of testosterone and tacrolimus roles on gastrocnemius muscle following experimental sciatic nerve injury in rats

Abstract

Peripheral nerve damage is a critical disorder causing disability of locomotion. The aim of the study was to clarify the effects of testosterone and tacrolimus on the gastrocnemius muscle following sciatic injury. The study was done on 20 rats (n = 5 in each group) whose left sciatic nerve was crushed for 10 s. The sham group (S) of animals received no medicine; the testosterone group (Tes) received testosterone (5 mg/kg, s.c.); the tacrolimus group (Tac): received tacrolimus (5 mg/kg, p.o.); the testosterone and tacrolimus group (Tes+Tac) received testosterone (5 mg/kg, s.c.) and tacrolimus (5 mg/kg, p.o.) daily for four weeks. The gastrocnemius was assessed by gross observation of the plantar surface of paws; the pelvic limb mass muscle and the muscle diameter ratio of the left pelvic limb to the right one by ultrasonography. The gastrocnemius muscle index (GMI) of the left and right pelvic limb, muscle colour, and pathologic changes were also studied. Pathology study of the gastrocnemius included fatty infiltration, muscle atrophy, presence of inflammatory cells and fibrosis formation. Heel redness and swelling were seen in group Tac. No significant difference was found in the GMI between the Tes and S groups (P > 0.01); its value was higher than in the Tes+Tac and Tac groups (P < 0.01). One rat in group Tes had fatty infiltration grade II. Inflammatory cells were grade I in group Tes but fibrosis formation was grade I in group Tes+Tac. Our results show that tacrolimus and testosterone administration may shorten sciatic nerve regeneration time. Testosterone may diminish gastrocnemius muscle atrophy after sciatic nerve crush.