What is platelet rich plasma (PRP)?

Marx one of the pioneers of PRP defined it quite simply: "it is a volume of autologous plasma that has a platelet concentration above baseline". (Marx, Implant Dentistry Dec. 2001, pp. 225-228) There have been other attempts to specific what define PRP but I think this one is the best.

I would add that PRP naturally is unactivated. In his paper, Dr. Marx states that activation of platelet results 70% of the stored growth factors being secreted with in 10 minutes and close to 100% within the first hour. That makes it clear that PRP should NOT be activated until it is ready to be used. As I have consistently suggested, PRP should not be activated at all except in vivo by the collagen that is abundant within most connective tissues.

Any comments on this paper would be appreciated.

Total Tendon

ApexPRP

PRP activates Circulating Cells

The article referenced below discusses how locally injected PRP can mobilize cells to help heal a tendon. This provides solid mechanistic evidence to use PRP for tendon injuries and disorders and helps explain the positive clinical results. It is an excellent study and the authors have contributed significantly to our understanding of how PRP works.

Total Tendon and Apex PRP

Platelet-rich plasma enhances the initial mobilization of circulation-derived cells for tendon healing.

Kajikawa Y, Morihara T, Sakamoto H, Matsuda KI, Oshima Y, Yoshida A, Nagae M, Arai Y, Kawata M, Kubo T.

J. Cell Physiology Jan. 2008

Circulation-derived cells play a crucial role in the healing processes of tissue. In early phases of tendon healing processes, circulation-derived cells temporarily exist in the wounded area to initiate the healing process and decrease in number with time. We assumed that a delay of time-dependent decrease in circulation-derived cells could improve the healing of tendons. In this study, we injected platelet-rich plasma (PRP) containing various kinds of growth factors into the wounded area of the patellar tendon, and compared the effects on activation of circulation-derived cells and enhancement of tendon healing with a control group (no PRP injection). To follow the circulation-derived cells, we used a green fluorescent protein (GFP) chimeric rat expressing GFP in the circulating cells and bone marrow cells. In the PRP group, the numbers of GFP-positive cells and heat-shock protein (HSP47; collagen-specific molecular chaperone)-positive cells were significantly higher than in the control group at 3 and 7 days after injury. At the same time, the immunoreactivity for types I and III collagen was higher in the PRP group than in the control group at early phase of tendon healing. These findings suggest that locally injected PRP is useful as an activator of circulation-derived cells for enhancement of the initial tendon healing process. J. Cell. Physiol. (c) 2008 Wiley-Liss, Inc.