title: Circadian variation of growth factor levels in platelet-rich plasma.
abstract: 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.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Institutional.
  
  
  METHODS
  Ten adult male volunteers (mean age, 30.0 ± 2.6 years; range, 26-34 years).
  
  
  METHODS
  Each subject donated a 20-mL sample of fasting blood, 4 times per day (7 AM, 11 AM, 3 PM, and 7 PM).
  
  
  METHODS
  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.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan.
authors.forename: Katsuya
authors.initials: K
authors.lastname: Aoto
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kanamori
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yoshioka
authors.forename: Kenta
authors.initials: K
authors.lastname: Uemura
authors.forename: Masataka
authors.initials: M
authors.lastname: Sakane
authors.forename: Masashi
authors.initials: M
authors.lastname: Yamazaki
mesh_terms: D000328:Adult; D000077214:Becaplermin; D015415:Biomarkers / Q000097:blood; D001772:Blood Cell Count; D002940:Circadian Rhythm / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D053657:Platelet-Rich Plasma / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis / Q000097:blood*; D053773:Transforming Growth Factor beta1 / Q000097:blood*
chemical_list: D015415:Biomarkers; D020574:Proto-Oncogene Proteins c-sis; D053773:Transforming Growth Factor beta1; D000077214:Becaplermin