The NYTimes recently published an article on platelets as a soft tissue treatment. ABC News also did a piece on this use of platelets to treat soft tissue problems. Back in 1993, I was at an orthopedic grand rounds at Yale where the speaker was Albert Banes, PhD. Dr. Banes has done pioneering research on what stimulates fibroblasts to multiply and synthesize collagen (collagen is needed to repair soft tissue injuries). His work has shown that intermittent loading (application of force) stimulates both replication and synthesis in fibroblasts. He also talked about how platelet bound growth factor also does this.
Dr. Banes related an anecdote that is similar to these stories. He talked about how an orthopedist at UNC, where Banes worked had chronic patellar tendinosis that was refractory to treatment. The doctor, a triathlete had suffered with the pain for over a year. Banes suggested based upon research they were going to do that the orthopedist get his own blood spun down and inject his tendon with his own platelets. This eliminated the symptoms in less than a week.
I've been teaching, for a few years, a treatment, Graston Technique that research also shows stimulates fibroblasts to replicate and synthesize collagen.