Human primary myotubes +/- electrical pulse stimulation

Human myogenic progenitor cells (MPCs) were isolated from the gracilis of two patients (1 female and 1 male) undergoing anterior cruciate ligament reconstruction (age 30-34 years) using a human anti-CD56 (1:20, Cat# 355503, Biolegend) antibody for FACS. Cells were passaged 2-3 times in growth media consisting of Ham's F-10 (Thermofisher), 20% fetal bovine serum (FBS, Atlanta Biological, Minneapolis, MN, USA), 1% penicillin/streptomycin and 10ng/ml basic fibroblast growth-factor (bFGF, Peprotech, Rocky Hill, NJ, USA). Cells were differentiated into myotubes for 5 days using MyoCult differentiation media (Stemcell Technologies, Vancouver, Canada). On the fifth day, fresh media was added just prior to electrical pulse stimulation (E). Cells were then either stimulated at 12 V, 1 Hz, 2 ms for 24 hr (IonOptix C-Pace EP, Westwood, MA, USA) or had electrodes placed in wells with no stimulation (E(+) or E(-)), followed by immediate RNA extraction using Qiazol (Qiagen, Hilden, Germany).