A preliminary study of apoptosis in skeletal muscles at the early stage of peripheral never regeneration in rats

Abstract

Objective To explore skeletal muscle apoptosis at the early stage of peripheral never regeneration in rats.Methods A total of 54 male SD rats were randomly assigned to 3 groups ( n = 18/group): denervation group (A), neurorrhaphy group (B), normal control group (C).In group A, a 1 cm segment of the left sciatic nerve was removed.In group B, the left sciatic nerve was transected above the bifurcation and immediately repaired with 10-0 sutures.No surgery was done in group C.The gastrocnemius muscle wet weight served as an indicator of the degree of muscle atrophy.Marker of apoptosis, nuclear DNA fragmentation, was detected using terminal deoxyribnudeotidyl transferase mediated dUTP nick end labeling (the TUNEL method) and observed under confocal microscopy at 2, 14 and 28 days postoperatively.Another portion of the gastrocnemius muscle was homogenized to analyze the activity of caspase-3 and -8 by spectrophotometry.Results TUNEL labeling of fragmented DNA on histological sections in the neuorrhaphy group revealed levels of apoptotic nuclei higher than the control group and lower than the denervation group at the early stage ( ＜ 28days ).The activity of caspase-3 and -8 in the neuorrhaphy group was also higher than the control group but lower than the denervation group.Conclusion At the initial stage of peripheral never regeneration, apoptosis may contribute to muscle atrophy and extrinsic apoptotic pathways may take part in it. Key words: Peripheral nevers; Muscylar atrophy; Apoptosis