A commonly used blood pressure drug not only improves regeneration of injured muscle but also protects against its wasting away from inactivity, according to Johns Hopkins research team.
“The goal of the investigation was to find a way to prevent a bad situation from getting worse in the case of old muscle that’s injured or not used,” said Ronald Cohn, an assistant professor of pediatrics and neurology in the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine.
“As pleased as we were to see that losartan therapy in mice had a positive effect on muscle regeneration, we were most surprised and excited by its striking prevention of disuse atrophy,” added Cohn.
To investigate losartan’s role in muscle injury regeneration in the context of aging, the Hopkins team worked with 40 mice which, at 21-months old, were considered geriatric. The researchers examined the stained muscle tissue under a microscope at four days and again at 19 days, looking for signs of regeneration: small fibers with larger-than-usual nuclei.
After four days, they saw no difference in the number of regenerating fibers between the losartan-treated mice and those not treated. However, after 19 days, the losartan-treated mice had about 10 to 15 per cent of scar tissue formation compared with 30 to 40 per cent of scar tissue formation in those not treated.
Next, the researchers conducted disuse experiments to find out if losartan, in addition to improving muscle regeneration, might have even broader clinical applications in the protection against immobilization atrophy.
Again, using 21-month-old mice, half treated with losartan and half not, the team this time clipped the hind right foot of the mice to their knees, immobilizing just the shin muscles; otherwise, the mice were normally active.
After 21 days, the animals’ shin muscles were weighed and compared under a microscope. The animals not treated with losartan lost 20 per cent of the mass of their immobilized shin muscles.
“When we saw that the loss of muscle fibers was completely prevented by losartan therapy, it was quite mind-blowing,” added Cohn.
The study has been published in the journal Science Translational Medicine.