We were discussing the efficacy of PRP as well as some of the pros/cons this weekend while recording an upcoming podcast.
This paper did a nice job explaining what we know versus what we do not know at this point in time, regarding the basics science behind it. A referenced, full text article for you:
Yiqin Zhou and James H-C. Wang, “PRP Treatment Efficacy for Tendinopathy: A Review of Basic Science Studies,” BioMed Research International, vol. 2016, Article ID 9103792, 8 pages, 2016. https://doi.org/10.1155/2016/9103792.
link to free full text: https://www.hindawi.com/journals/bmri/2016/9103792/