TRPV1 as a biomarker for regenerating muscle fibers (P2.113)

Objective: To identify biomarkers for regenerating muscle fibers, we examined the expression of transient receptor potential cation channel vanilloid 1 (TRPV1) in regenerating muscle fibers injured by cardiotoxin. Background: A clear physiological role of TRPV1 is the sensation of increased temperature in a tissue. Previous reports showed that the activation of TRPV1 by its agonist capsaicin increases myogenin protein levels. Thus, TRPV1 plays an important role in skeletal muscle growth. Design/Methods: Tibialis anterior muscles in 8–12 week C57BL/6 mice were injured by cardiotoxin injection (10 μM). Mice were euthanized at 0, 14, 21 and 30 days post injury, and muscles were collected. Serial frozen sections of the cardiotoxin-injured muscle specimens and muscle specimens from normal control subjects were examined by immunohistochemistry and Western blot analysis using antibodies against TRPV1 and developmental myosin-heavy chain (MHC-d). Results: At 1 week after muscle injury, immunoreactivity for MHC-d was observed in regenerating muscle fibers, while TRPV1 immunoreactivity was not observed. At 3 weeks after the cardiotoxin injury, both TRPV1 and MHC-d immunoreactivity were observed in atrophic muscle fibers present during muscle regeneration. The distribution pattern of TRPV1 and MHC-d was not consistent, and the ratio of TRPV1/MHC-d double-positive fibers was approximately 30–35% of all regenerating atrophic muscle fibers. These results suggest that an investigation of MHC-d expression alone in damaged muscle is inadequate for the prediction of muscle fiber regeneration. Conclusions: Our results suggest that both TRPV1 and MHC-d are important biomarkers for the detection of muscle fibers proliferation. Disclosure: Dr. Murata has nothing to disclose. Dr. Mori has nothing to disclose. Dr. Ito has nothing to disclose.