Sustained or higher levels of growth factors in platelet-rich plasma during 7-day storage

The effectiveness of platelet-rich plasma (PRP) for treating soft tissue injuries is still controversial. Most of PRPs were prepared simply by concentrating in volume and were injected right after preparation in physician offices. Neither platelet count nor growth factors were quantitated in advance. We prepared and stored leukocyte and platelet-rich plasma (L-PRP) by regular separation protocols for blood components in the blood bank. And we investigated the dynamic change of growth factors in the L-PRPs over the period of storage.

The L-PRPs were prepared by 2-step centrifugation and stored agitatedly at 22 °C for 7 days in the platelet incubator of blood bank. Levels of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF)-basic, hepatocyte growth factor (HGF), insulin-like growth factor (IGF)-1, platelet derived growth factor (PDGF)-AB, endothelial growth factor (EGF), and transforming growth factor (TGF) over the period of storage were evaluated daily after freeze-thawing to release growth factors from platelet.

Compared to original whole blood, platelet concentration, VEGF, FGF-basic, PDGF-AB, EGF, and TGF-beta1 levels of L-PRPs significantly increased after PRP preparation. Both HGF and IGF-1 in L-PRPs remained the original plasma level. Platelet, FGF, and TGF-beta1 concentrations sustained during storage, and concentrations of VEGF, HGF, IGF-1, PDGF-AB, and EGF in L-PRPs increased over the period of storage.

During the storage in blood bank, platelet counts and 7 growth factors sustained or reached higher level than L-PRP obtained on first day. Multiple injections of stored PRPs could become applicable by our protocol.