In the latest season of HBO show Silicon Valley, the tech-billionaire antagonist Gavin Belson is shown undergoing a blood transfusion from his own personal "blood boy" – a young, healthy subject whom he pays to harvest youthful blood from. Like many seemingly absurd scenarios from the satirical show, it is a story with a basis in fact. Ambrosia, a San Francisco-based startup founded in 2016, is now embarking on a controversial trial intended to demonstrate the medical benefits of young blood transfusions. Anyone can enrol, as long as they are over the age of 35 and can afford the US$8,000 per transfusion charge.

There is a long history of people believing there to be a rejuvenating power in the blood of the young. Sixteenth century German chemist Andreas Libavius was recorded as proposing to connect a young man and old man together by the arteries. In a story recounted by Sally Rudmann, Libavius was heard to say, "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."

Of course, until we discovered the complexity of human blood types in the early 20th century, blood transfusions of any type were a dangerous game of Russian roulette. In the 1920s, philosopher and physician Alexander Bogdanov conducted experiments on himself and claimed infusions of young blood gave him more energy, improved his eyesight, and put a stop to his balding. However, Bogdanov died a few years into his blood experiments, allegedly either due to an incorrect blood type or from blood laden with malaria and tuberculosis.

The modern focus on youthful blood transfusions as a fountain of youth comes mostly from a Stanford study published in 2014. While other researchers were focusing on specific genes or protiens that could possibly combat aging, a team decided to keep things simple –get some blood from young mice, remove the blood cells, and then inject the remaining plasma into old mice.

Although the study was obviously incredibly limited, the results were impressive. Across several different tests the old mice that received the young blood behaved like young mice. The study, initially rejected by the journal Nature before ultimately being published in Nature Medicine, was titled "Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice".

Inspired by that study, and others, a young entrepreneur named Jesse Karmazin founded Ambrosia, kicking off its services in the form of a patient-funded open trial. The company is initially operating what is technically a formal clinical trial, recorded on, and scheduled to run for two years from 2016 to 2018. The trial, (which essentially allows the company to circumvent FDA regulations), will involve measuring a large set of age-associated biomarkers from each patient before, and one month after, a blood treatment.

The design of the trial has drawn significant criticism from many scientists who claim it is flawed for lacking a placebo control group, unclear in the effects of the "age-associated biomarkers" it will be testing, and problematic in being funded by the patients themselves. Even the Stanford neuroscientist Tony Wyss-Coray, behind the key 2014 mouse study, is skeptical of Ambrosia's purported "trial."

"People want to believe that young blood restores youth, even though we don't have evidence that it works in humans and we don't understand the mechanism of how mice look younger," Wyss-Coray told MIT Technology Review in early 2017. "I think people are just attracted to it because of vampire stories."

Still, Ambrosia is reported to have already signed up 600 subjects, or clients, and their average age is 60 years old. A general blood treatment costs US$8,000 and involves 1.5 liters (0.39 US gal) of plasma transfused into an individual over two days. The blood reportedly comes from blood banks, is treated to remove blood cells, and then just the plasma is transfused into the patient. Ostensibly, it is just like the Stanford mice study.

Who is participating in this strange, expensive experiment? Obviously quite a few very rich people. Tech-billionaire Peter Thiel is rumored to be interested, after discussing the process in interviews, and Ambrosia-founder Jesse Karmazin suggested one of Thiel's senior employees has been in contact regarding the trial. Thiel is also thought to be the primary inspiration for the character of Gavin Belson in HBO's Silicon Valley.

At this stage it is hard to tell whether this is life imitating art or art imitating life. The only thing we do know for sure is that over 600 people in San Francisco are currently paying $8,000 a pop for the blood of the young.