Using Young Blood for the Old

This is apparently becoming a thing again, but it's an old concept. Even in the linked article, the author writes:

Wyss-Coray is not the first person to wonder whether the answer to the problem of ageing might lie in human blood. One of the first physicians to propose blood transfusions to rejuvenate older people was Andreas Libavius, a German doctor and alchemist. In 1615 he proposed connecting the arteries of an old man to those of a young man. He had high hopes for the procedure. “The hot and spirituous blood of the young man will pour into the old one as if it were from a fountain of youth, and all of his weakness will be dispelled,” he claimed, in an account told in the Textbook of Bloodbanking and Transfusion Medicine by Sally Rudmann. It is unclear how it turned out; there is no record of the transfusion happening.

... 

The fledgling years of the Royal Society, founded in London in 1660, witnessed some of the earliest experiments in blood transfusion. When Robert Boyle, one of the society’s founders, compiled a wishlist of scientific projects, the top entry was “The prolongation of life”. That might be achieved, he hoped, by replacing old blood with new.

But there are many more examples.