For now, here's what we know — and what we don't know — about stem-cell therapy for knees. Bryan Johnson flew to the Bahamas to get MSC stem cells injected into his knees, hips, and shoulders — for about $16,500 per joint. Plus, even Sampson warns that young donor stem cells should not be seen as a quick fix or a panacea. Done with proper medical oversight, some studies have found no adverse effects from stem-cell treatments for various conditions. Botched stem-cell treatments can cause infection, blindness, and excessive cell growth, which can trigger the formation of tumors.

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Persons: —, Bryan Johnson, Johnson, hasn't, Josh DeAngelis, Rasul Chaudhry, Chaudhry, Steven Sampson, Chaundhry, Sampson, Peyton Manning, Patrick Smith, George Kittle, Hulk Hogan, TJ Dillashaw, Rafael Nadal, Jack Nicklaus, I've, it's, Paul Knoepfler, he's, It's, Mattias Bernow, we'll, Knoepfler Organizations: Service, Business, MSC, Oakland University, NFL, FDA, UFC, ESPN, CNN, UC Davis School of Medicine Locations: Bahamas, Panama