In Vitro Betagro Supplementation Stimulates Myogenesis of Porcine Fetal Myoblasts and Porcine Satellite Cells in a Divergent Manner

Two separate experiments were conducted to evaluate the effect of betaGRO supplementation on proliferation rate, fusion rate, and myotube growth of porcine fetal myoblasts (PFM) and porcine satellite cells (PSC) in vitro. The PFM were isolated from the LM of d-60 of gestation fetuses and PSC from the LM of piglets within 24 h of birth. Proliferation assays were conducted as 4 × 3 factorial arrangements with time of culture (24, 48, 72, 96 h) and media treatment as main effects. Media treatments consisted of: a positive control which contained high-glucose Dulbecco's Modified Eagle Medium supplemented with 10% (vol/vol) fetal bovine serum, 2% (vol/vol) porcine serum, 100 U/mL penicillin, 100 µg/mL streptomycin, and 20 µg/mL gentamicin (HS); a negative control which consisted of HS without 10% FBS (LS); and LS supplemented with 10 mg/mL betaGRO (BG). Fusion rate and myotube growth assays were conducted as 2 × 2 factorial designs with serum concentration and betaGRO inclusion as the main effects. There was a treatment × time interaction (P<0.01) for proliferation rate of PFM. At all time points, HS and BG PFM had greater proliferation rates compared LS (P<0.01). The HS treatment had greater proliferation rates than BG (P<0.02) except at 72 h of culture (P=0.44). There were betaGRO × serum interactions for PFM fusion rate and myotube growth (P<0.01). When betaGRO was added to LS media of PFM, fusion percentage and myotube diameter decreased (P<0.01), while fusion percentage increased (P<0.01) and myotube diameter was unaffected (P=0.63) when betaGRO was added to HS media. There were treatment × time and betaGRO × serum interactions for proliferation rate and fusion rate of PSC, respectively (P<0.01). At all time points, HS had greater proliferation rates than LS and BG (P<0.01), and LS had greater proliferation rates than BG (P<0.02). When betaGRO was added to LS and HS media of PSC, fusion percentage increased for both media types (P<0.01). There was no betaGRO × serum interaction (P=0.63) for PSC myotube growth; however, betaGRO supplemented myotubes were larger (P<0.01) than non-betaGRO supplemented myotubes. These two experiments indicate betaGRO supplementation to culture media stimulates divergent responses based on the type of cell examined, with BG increasing proliferation in PFM and fusion rate and myotube growth in PSC. These findings suggest betaGRO supplementation may enhance both myogenesis in utero, as well as postnatal muscle hypertrophy.