[patall]

Yes and no. While some cells may be impossible to rejuvenate otherwise, there are few reasons why we cannot just exchange many organs for dish grown ones, i.e artificially grown kidneys. For others like blood stem cells, we many extinguish the existing ones and add replace them by fresh ones that lack any pathogenic somatic mutations every so often. Even parts of the brain may be replaced one by one, though I assume such a technology is quite far away (compared to the other two that may be possible in the next 2-3 decades).