BackgroundHematopoietic stem cells (HSCs) are primitive cells that often appear in peripheral blood (PB) following mobilization events from bone marrow due to stress, injury, exercise, or pharmaceutical agents like filgrastim and pegfilgrastim. These cells can be concentrated into platelet-rich plasma (PRP), which is widely used in orthopedics. Filgrastim requires consecutive daily doses, while pegfilgrastim requires a single dose. Hypothesis/PurposeThis crossover study aimed to compare the safety profiles of filgrastim and pegfilgrastim administration and quantify the cellular content of PRP derived from PB following drug administration. We hypothesized comparable rates and severity of adverse events (AEs) among participants, along with similar cellular content in the PRP products. Study designProspective, single-center, crossover and controlled laboratory study. MethodsHealthy participants aged 19 to 39 years and weighing 50 to 100 kg were screened and enrolled. They underwent a crossover design with 2 interventions separated by a washout period: 4 days of 10 mcg/kg filgrastim or a single 6 mcg/kg pegfilgrastim injection. PB samples were collected before and after each intervention to produce PRP samples for cellular comparison in vitro. AEs were monitored for severity and frequency throughout the study. ResultsTen healthy male participants were included in this study. The mean ± (SD) age of the participants was 28.30 ± 6.48 years, with a mean ± (SD) BMI of 25.29 ± 3.80. The most common AEs for filgrastim included fatigue (36%), myalgia (36%), and back pain (9.1%), and the most common AEs for pegfilgrastim included myalgia (31%), fatigue (23%), and back pain (23%). There were no significant differences in safety data between filgrastim and pegfilgrastim in terms of AE occurrence (P = .49) nor relationship to the study drug (P > .99). The baseline PRP samples had an average total nucleated cell (TNC) count of mean ± (SD) 3844.77 ± 1326.71, the filgrastim PRP samples had 6939.20 ± 6252.24, and the pegfilgrastim PRP samples had 8923.20 ± 3258.09. The baseline PRP samples had an average TNC concentration of mean ± (SD) 1.33 × 107 ± 4.60 × 106 cells/mL, the filgrastim PRP samples had 1.83 × 107 ± 1.81 × 107 cells/mL, and the pegfilgrastim samples had 3.09 × 107 ± 1.13 × 107 cells/mL. Significant differences were found in both TNC count (P = .010) and TNC concentration (P = .004). Specifically, there were significantly higher average TNC counts in the pegfilgrastim PRP samples compared to the control (P = .0082), but there were no differences between the filgrastim and pegfilgrastim PRP samples (P = .1515). There was also a significantly higher average TNC concentration in the pegfilgrastim PRP samples compared to control PRP (P = .0082) and compared to filgrastim PRP (P = .0197). White blood cells, basophils, and immature granulocytes were significantly higher in the pegfilgrastim PRP compared to the control (P = .0082, P = .0002, and P = .0272). Neutrophils were significantly higher in both the filgrastim PRP (P = .0357) and pegfilgrastim PRP (P = .0024) compared to the control. There were no differences detected for these measures among the filgrastim and pegfilgrastim PRP groups. None of the cultured PRP samples produced colony-forming unit fibroblasts, however cellular growth was qualitatively observed after overnight incubation. All PRP products expressed high levels (>88%) of hematopoietic progenitor cell/HSC-specific CD45+, CD34+, CD45dim+, and hematopoietic progenitor cell/HSC+ markers. There were no statistically significant differences in cell-surface antigens between the PRP products. ConclusionsThis prospective, single-center, crossover and controlled laboratory study demonstrated that filgrastim and pegfilgrastim administration appears safe and pegfilgrastim is equivalent to filgrastim for the mobilization of white blood cells and cells expressing hematopoietic cell-surface markers into the PB and consequently, into the derived PRP product. Clinical relevanceThis study presents pegfilgrastim as a single-injection alternative to filgrastim for the mobilization of HSCs into the PB and subsequent PB-derived PRP, which is more convenient and less invasive for patients.