Objective: To observe the effect of electroacupuncture (EA) at "Ashi" acupoint and "Kunlun" (BL60) on elastic modulus, histopathological changes and expression of myogenic regulatory factors in gastrocnemius(GM) contusion rats, so as to explore the therapeutic effect of local acupoint selection and acupoint selection along channel.
Methods: Male SD rats were randomly divided into blank control (n＝5), model (n＝15), Ashi-point (n＝15) and BL60 (n＝15) groups. The acute GM contusion model was established by striking (free falling) the GM with a homemade hitter. EA (0.5 to 1.0 mA, 2 Hz/10 Hz) was applied to Ashi-point (local focus) and BL60 for 30 min 24 h after muscle injury. The elasticity maximum (Emax) of gastrocnemius muscle was measured by using an ultrasonic device. Histopathological changes were observed after H．E. stain, and the number of Myogenic differentiation(MyoD)- and Myogenin (MyoG)-positive cells was detected by using immunohistochemistry.
Results: After mdeling, the Emax value of GM was significantly increased from the 3rd h to 7th day in comparison with pre- injury of muscle (P<0.05), and was markedly increased on the 3rd day and obviously lower on day 7 in the Ashi-point group than in the model group (P<0.05). The numbers of MyoD- and MyoG-positive cells of GM were significantly increased on day 7 in the model group than in the blank control group (P<0.05), and both further increased in Ashi-point on day 3 and 5, and MyoG-positive cells further increased in BL60 group on day 5 and in Ashi-point group on day 7 relevant to the model group(P<0.05). The therapeutic effect of EA-Ashi-point was apparently superior to that of BL60 in up-regulating Emax on day 3 and in up-regulating the number of MyoD-positive cells on day 3 and 5 (P<0.05). H．E. stain showed disordered arrangement of muscle fibers, infiltration of inflammatory cells, increase of intercellular space, and edema on day 3 after modeling (which was milder in the Ashi-point group); and gradual fusion and thickening of new born muscle fibers with obvious connective tissue hyperplasia converged to the lesioned region on day 7 in the model group (convergence of new born muscle cells to the lesion region in both EA groups, and more complete tissues in the Ashi-point group).
Conclusion: EA of Ashi-point and BL60 can up-regulate the expression of myogenic regulatory factors MyoD and MyoG of GM tissue in GM contusion rats, which may contribute to its function in promoting recovery of muscle elasticity. The role of EA-Ashi-point is superior to that of EA-BL60.
Keywords: Ashi-point; Electroacupuncture; Gastrocnemius injury; Kunlun(BL60); Myogenic differentiation; Myogenin; Shear wave elastography.