Hepatocyte growth factor (HGF) and the satellite cell response following muscle lengthening contractions in humans
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AbstractThe time‐courses of satellite cell (SC) activation and protein expression of hepatocyte growth factor (HGF), HGF activator (HGFA), HGFA inhibitor‐1 (HAI‐1), and HGFA inhibitor‐2 (HAI‐2) in human skeletal muscle, as well as serum HGF following a single bout of muscle lengthening contractions, were determined. Eight recreationally active participants were recruited for the study. Subjects performed 300 lengthening contractions involving the quadriceps femoris muscles of a single leg at a fixed velocity of 180°/s. Percutaneous muscle biopsies were taken before (PRE) and at 4 h (T4), 24 h (T24), 72 h (T72), and 120 h (T120) following the exercise. The protocol resulted in an increase in the number of SCs [neural cell adhesion molecule (NCAM)‐labeled cells] expressed relative to total myonuclei, at T24, compared with both PRE and T4 (P < 0.05), and peaked at T72 (∽80% increase vs. PRE, P < 0.05). HGF protein increased significantly in serum from baseline (PRE) to T4 (P < 0.05). Active HGF protein was detected in skeletal muscle at rest [14.4 ± 1.3 average integrated density value (IDV)/actin average IDV] and tended to increase at early time‐points (P = 0.12). HGFA protein increased significantly from PRE to T24 (P < 0.05). HAI‐1 protein increased significantly from PRE to T24 (P < 0.05). HAI‐2 (32 kDa) increased significantly from baseline (PRE) by T24 (P < 0.05), and also by T72 and T120 (P < 0.05). We conclude that a single bout of lengthening muscle contractions is sufficient to activate SCs, which may involve both a local and systemic HGF response to contraction‐induced injury. Muscle Nerve, 2008
