It also needs to be a biomarker that tracks with rejuvenation and doesn't track non-rejuvenation. Which is probably more than this result can offer. It's like,

It also needs to be a biomarker that tracks with rejuvenation and doesn't track non-rejuvenation. Which is probably more than this result can offer. It's like, if you have an old car, the steel body will rust in sync with the engine getting worn. But if you fix the engine, it won't be reflected in the rust, it will just break the previous association. And if you fix the rust, the engine has not been rejuvenated.