Researchers led by Irina Conboy at UC Berkeley have completed some very interesting research on human muscle. Essentially, they found that it is possible to regenerate old human muscle by activating an enzyme called mitogen-activated protein kinase (MAPK). MAPK regulates the activity of an adult stem cell receptor called Notch, which triggers growth when activated.
This is very exciting work, since it has been done on humans (following trials on rodents, of course). Here is a news piece that gives a nice summary of it all. I wonder how much the human participants got paid for doing this. Given that they had to have biopsies taken of their muscles and put into casts for two weeks, it must have been pretty uncomfortable…
Making old muscle young again