Ablation of S1P receptor protects mouse soleus from age-related drop in muscle mass, force, and regenerative capacity.

We investigated the effects of S1P deficiency on the age-related atrophy, decline in force, and regenerative capacity of soleus muscle from 23-mo-old male (old) mice. Compared with muscle from 5-mo-old (adult) mice, soleus mass and muscle fiber cross-sectional area (CSA) in old wild-type mice were reduced by ~26% and 24%, respectively. By contrast, the mass and fiber CSA of soleus muscle in old S1P-null mice were comparable to those of adult muscle. Moreover, in soleus muscle of wild-type mice, twitch and tetanic tensions diminished from adulthood to old age. A slowing of contractile properties was also observed in soleus from old wild-type mice. In S1P-null mice, neither force nor the contractile properties of soleus changed during aging. We also evaluated the regenerative capacity of soleus in old S1P-null mice by stimulating muscle regeneration through myotoxic injury. After 10 days of regeneration, the mean fiber CSA of soleus in old wild-type mice was significantly smaller (-28%) compared with that of regenerated muscle in adult mice. On the contrary, the mean fiber CSA of regenerated soleus in old S1P-null mice was similar to that of muscle in adult mice. We conclude that in the absence of S1P, soleus muscle is protected from the decrease in muscle mass and force, and the attenuation of regenerative capacity, all of which are typical characteristics of aging.