The young mouse old mouse experiment needs better explanation.
Instead of just a blood transfusion, the old mouse got the benefits of the young mouse’s immune system, liver, kidneys, stem cells, hormones, and more.
However, what the older mouse didn’t get were the things outside of the bloodstream, including digestive chemicals such as stomach acid and bile, the lymphatic system, “deposits” such as atherosclerosis, stones, plaques, and most especially the younger mouse’s microbiome, or intestinal flora, including viruses, bacteria, yeasts and fungus, protozoa, and parasites.
The original (expanded) article in the same magazine re the mice experiment. Looks like you may have already looked at it from the points you made
thx