Inhibited skeletal muscle healing in cyclooxygenase-2 gene-deficient mice: the role of PGE2 and PGF2alpha.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat skeletal muscle injury. However, studies have shown that NSAIDs may be detrimental to the healing process. Mediated by prostaglandin F(2alpha) (PGF(2alpha)) and prostaglandin E(2) (PGE(2)), the cycloxygenase-2 (COX-2) pathway plays an important role in muscle healing. We hypothesize that the COX-2 pathway is important for the fusion of muscle cells and the regeneration of injured muscle. For the in vitro experiments, we isolated myogenic precursor cells from wild-type (Wt) and COX-2 gene-deficient (COX-2(-/-)) mice and examined the effect of PGE(2) and PGF(2alpha) on cell fusion. For the in vivo experiments, we created laceration injury on the tibialis anterior (TA) muscles of Wt and COX-2(-/-) mice. Five and 14 days after injury, we examined the TA muscles histologically and functionally. We found that the secondary fusion between nascent myotubes and myogenic precursor cells isolated from COX-2(-/-) mice was severely compromised compared with that of Wt controls but was restored by the addition of PGF(2alpha) or, to a lesser extent, PGE(2) to the culture. Histological and functional assessments of the TA muscles in COX-2(-/-) mice revealed decreased regeneration relative to that observed in the Wt mice. The findings reported here demonstrate that the COX-2 pathway plays an important role in muscle healing and that prostaglandins are key mediators of the COX-2 pathway. It suggests that the decision to use NSAIDs to treat muscle injuries warrants critical evaluation because NSAIDs might impair muscle healing by inhibiting the fusion of myogenic precursor cells.