MECHANISM OF BFGF IN PROMOTING THE RECOVERY OF MUSCLE FIBER ATROPHY AFTER SCIATIC NERVE INJURY IN RATS

Zean Wei^1#, Renqun Mao^2#, Chunqing Wang³, Qing Li³, Longjia Dong⁴, Leiluo Yang³, Youjia Xu^1*

¹Department of Orthopaedics, The Second Affiliated Hospital of Soochow University, Suzhou, 215044, China - ²Hand and Foot Microsurgery, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, 518052, China - ³Department of Orthopaedic Trauma, The Affiliated Hospital of Guizhou Medical University, Guiyang, 550001, China - ⁴Department of Orthopaedic, The Affiliated BaiYun Hospital of Guizhou Medical University, Guiyang, 550014, China

Objective: To analyze the mechanism of basic fibroblast growth factor (bFGF) in promoting the recovery of muscle atrophy after sciatic nerve injury in rats.

Methods: 120 SD rats were randomly selected as the control group, and the rest were divided into 5 groups. The experimental groups were treated for 1, 3, 5, 7, and 9 weeks, with 20 rats in each group. The left sciatic nerve was injured with mini hemostatic forceps. A gelatin sponge soaked with bFGF (concentration of 9900u / ml) was placed in the injured area of the experimental group, and a gelatin sponge injected with normal saline was put into the injured part of the control group. Gastrocnemius, longusdigitorumlongus, and metatarsal muscles were separated respectively. The common peroneal nerve on the injured side was electrically stimulated. The single contraction force (1Hz) and tetanic contraction force (50Hz) of gastrocnemius muscle were recorded by a two-channel physiological recorder. Compared with the healthy side, the recovery rate of the gastrocnemius muscle was calculated. The amplitude of muscle fiber fibrillation potential, the change of muscle fiber diameter, the cross-sectional area of muscle fiber, and the number of PCNA positive muscle nuclei were compared.

Results: the diameter of gastrocnemius intermediate muscle fiber and white muscle fiber in the observation group showed an increasing trend with the prolongation of medication time, and the diameter of gastrocnemius intermediate muscle fiber and white muscle fiber at each time point was higher than that of the control group, the difference was statistically significant (P< 0.05). The diameter of intermediate muscle fiber, white muscle fiber, and red muscle fiber of longusdigitorumlongus in the observation group showed an increasing trend with the prolongation of medication time and the diameters of intermediate muscle fiber, white muscle fiber, and red muscle fiber of long toe muscle at each time point were higher than those of the control group, the difference was statistically significant (P< 0.05). The diameter of intermediate muscle fiber, white muscle fiber, and red muscle fiber of the observation group showed an increasing trend with the prolongation of medication time and the diameter of intermediate muscle fiber, white muscle fiber, and red muscle fiber of metatarsal muscle at each time point was higher than that of the control group, and the difference was statistically significant (P< 0.05). The recovery degree of gastrocnemius muscle, longusdigitorum muscle, and metatarsal muscle fiber in the observation group increased with time, and the difference was statistically significant (P< 0.05). Muscle fiber potential amplitude, muscle cell diameter, muscle fiber cross-sectional area, PCNA positive muscle nucleus, and muscle fiber gray level in the observation group were significantly higher than those in the control group (P< 0.05).

Conclusion: bFGF can promote the recovery of gastrocnemius muscle, longusdigitorum muscle, and metatarsal muscle atrophy after sciatic nerve injury in rats, which may be related to the improvement of muscle fibrillation potential amplitude, muscle fiber diameter, muscle fiber cross-sectional area and the number of PCNA positive muscle nuclei.