Objective: The influence of circadian rhythms has recently been considered in advanced studies of chronopharmacology and chronotherapeutics. Although emerging studies have reported the usefulness of platelet-rich plasma (PRP), no reports have described the diurnal variations in PRP growth factor levels. In the present study, we hypothesized that growth factor levels in PRP show a significant diurnal variation.
Design: Controlled laboratory study.
Setting: Institutional.
Participants: Ten adult male volunteers (mean age, 30.0 ± 2.6 years; range, 26-34 years).
Interventions: Each subject donated a 20-mL sample of fasting blood, 4 times per day (7 AM, 11 AM, 3 PM, and 7 PM).
Main outcome measures: Each blood sample was processed to produce PRP. Complete blood counts of peripheral blood (PB) and PRP, as well as quantitative determination of PRP growth factor levels (platelet-derived growth factor and transforming growth factor) were performed. Statistical analyses were conducted using a one-way repeated measures analysis of variance.
Results: No significant differences were observed in platelet, white blood cell, and red blood cell counts in the PB or in the PRP samples throughout the course of the day. In addition, there were no significant differences in PRP growth factor levels at the various time points.
Conclusions: Significant diurnal variations in platelet counts and growth factor levels were not observed in PRP. Therefore, adjustments for diurnal variation in chronotherapy may not be important when PRP is used in clinical practice.