‘Biohacker’ Bryan Johnson has revealed the latest surgery he is undergoing to try to reverse his biological age.

As if using his son’s blood and electric-shocking his own penis weren’t enough, Johnson, 46, has more plans to reverse his medical age to 18 years old.

Johnson said in a YouTube video posted on June 25 that he ‘injected’ his ‘joints with 300 million stem cells’.

And not just any old stem cells, but ‘300 million young Swedish bone marrow mesenchymal stem cells’ that he had injected into not only one region of his body, but also his joints, shoulders, and hips.

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But why?

Johnson’s description reads: “The aim: superhuman joints to match my total bone mineral density, which is in the top 99.8 percent for 30 year olds.”

In the video, he explains to Dr. Steve Sampson that the goal of his endeavor is to’rejuvenate’ his ‘entire body’ back to the age of 18, and that he came to him because he has’some soreness’ in his right shoulder as a result of growing up playing a variety of sports.

Johnson says he’s been suffering ‘weakness’ in the area, and scans show’meaningful degeneration’ in his joints.

While he is not in agony, he hopes to restore his physique to that of an 18-year-old by addressing both the soreness in the shoulder and rejuvenating what has been lost due to wear and strain on [his] joints.

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Despite Dr. Sampson’s warning that he doesn’t know how these cells may effect Johnson and his desire to de-age his body, the self-proclaimed ‘biohacker’ dives right in.

The Swedish bone marrow cells traveled 5,000 kilometers to Johnson in the Bahamas, where they were preserved in liquid nitrogen containers.

They were then thawed and injected very precisely into Johnson via a needle within a 30-minute window before they expired, with the biohacker given a small amount of local anaesthetic beforehand to help with any potential pain – with Johnson having to return for a second day of injections to complete the rest of his body as well, despite feeling some discomfort.

But what do stem cells really do?

Dr. Sampson says that these stem cells are known as therapeutic signalling cells. They nearly resemble mobile paramedics.

“So, if you think of our body as being made up of approximately 37 trillion cells coursing through it, when we have an injury – for example, if I get out of this chair and bang my knee – that triggers an injury response in which these mobile cells – called Pericytes – release and travel to the site of injury.

“So, we’re trying to mimic that response and what we found is in the published literature these MSC’s have the ability to significantly tamper or lower inflammation.”

Johnson has yet to provide an update to fans on how he is doing since the treatment and whether or not it was successful, so we’ll just have to keep tuned.