Cellular Components and Growth Factor Content of Platelet-Rich Plasma With a Customizable Commercial System

Background: Platelet-rich plasma (PRP) is an autologous orthobiologic treatment option for musculoskeletal conditions with favorable results in a limited number of high-quality clinical trials. Because different blood-processing methods result in PRP with varying cellular and growth factor content, it is critical that clinicians understand the content of the specific PRP being used in clinical practice. One adjustable system, the Angel System, has few independent laboratory reports on the specific composition of its PRP. The goal of this study was to quantify the cellular and growth factor composition of PRP produced by this system at its lowest hematocrit settings.

Hypothesis: The authors hypothesized that the system would significantly concentrate platelets over baseline and, at the lowest hematocrit settings, would reduce leukocytes to produce leukocyte-poor PRP.

Study design: Descriptive laboratory study.

Methods: Ten healthy male volunteers donated 150 mL of whole blood for processing. Three separate processing cycles were performed for each sample at the 0%, 1%, and 2% hematocrit settings. The resultant PRP from each cycle was sent for complete blood counts and enzyme-linked immunosorbent assay to quantify the following growth factors: platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1), and vascular endothelial growth factor (VEGF).

Results: The system consistently concentrated platelets 5-fold over baseline, with no significant differences among settings. Leukocytes were concentrated at all settings, between 2 and 5 times over baseline. The 0% and 1% settings had significantly lower leukocyte concentrations than the 2% setting. Lymphocytes made up >89% of the leukocyte differential, while neutrophils represented <11% of the differential at each setting. There was a significant increase in PDGF and bFGF, a significant decrease in IGF-1, and no change in VEGF, with no difference among settings.

Conclusion: The system consistently concentrated platelets 5 times but was unable to reduce leukocytes, therefore resulting in leukocyte-rich PRP at each setting tested. Leukocytes had a differential composition of >89% lymphocytes and <11% neutrophils. For all settings, PDGF and bFGF were concentrated; IGF-1 was reduced; and VEGF was not significantly different from baseline.

Clinical relevance: These data can serve to guide clinicians considering using this particular PRP system. It consistently yielded leukocyte-rich PRP with a lymphocyte-predominant/neutrophil-reduced profile. Further research is needed to better understand how to apply this specific PRP in clinical practice.