I'd like to see the study. The body does have means to repair/correct for oxidative damage, and there are mechanisms by which DNA sequences can be corrected. Also, telemeres lost in cell divisions can be replaced, and epigenetic regulation can be modified or reversed. One of the best examples of this reverse aging IMHO is cloning with an adult nucleus. It's incredible that just the cytosol alone of an embryo has enough to motivate an adult cell to revert to developmental mechanisms. Immortalized cell lines are a crude example of making cells continue on. Theortically, there is no component of the body that can't be replaced piecemeal, or any damage that can't be undone. There is truth to the notion that we aren't the same material we were when we were born. The trick is to get the body to make the replacement, and to swap in less corrupted components.