{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,6]],"date-time":"2026-11-06T12:32:21Z","timestamp":1793968341701,"version":"4.8.0"},"reference-count":30,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,9,23]],"date-time":"2025-09-23T00:00:00Z","timestamp":1758585600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["CIMB"],"abstract":"<jats:p>Platelet-rich plasma (PRP) is increasingly used in orthopedics, with its regenerative potential attributed to platelet-derived cytokines and growth factors. However, variability in PRP composition hampers standardization and reproducibility, contributing to inconsistent outcomes. Since platelet counts in whole blood follow circadian rhythms, we investigated whether blood collection time affects PRP composition. Venous blood was collected from 25 healthy individuals at 8:00 a.m., 12:00 p.m., and 4:00 p.m. Whole blood was analyzed, and leukocyte-poor PRP (LP-PRP) was prepared for quantification of erythrocytes, leukocytes, and platelets. Platelets were lysed by freeze\u2013thaw cycles, and protein levels of PDGF-BB, IGF1, HGF, IL6, and IL10 were measured via ELISA. Whole blood exhibited diurnal variation in platelet counts. In contrast, LP-PRP was consistently depleted of leukocytes and erythrocytes and showed stable platelet enrichment (PRP\/whole blood ratio 2.1 \u00b1 0.3). Protein concentrations in LP-PRP did not differ across collection times. Despite marked interindividual variability, no time-dependent differences were observed in platelet or protein composition. These results demonstrate that LP-PRP is temporally stable, independent of blood sampling time. This robustness supports flexible clinical use and contributes to efforts toward PRP standardization in therapeutic practice.<\/jats:p>","DOI":"10.3390\/cimb47100788","type":"journal-article","created":{"date-parts":[[2025,9,23]],"date-time":"2025-09-23T10:27:53Z","timestamp":1758623273000},"page":"788","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["The Time of Blood Collection Does Not Alter the Composition of Leucocyte-Poor Platelet-Rich Plasma: A Quantitative Analysis of Platelets and Key Regenerative Proteins"],"prefix":"10.3390","volume":"47","author":[{"given":"Hadrian","family":"Platzer","sequence":"first","affiliation":[{"name":"Department of Orthopedics and Trauma Surgery, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Stra\u00dfe 3, 24105 Kiel, Germany"},{"name":"Orthopedic Research Center, Kiel University, Michaelisstr. 5, 24105 Kiel, Germany"},{"name":"Department of Orthopedics, Heidelberg University Hospital, Schlierbacher Landstra\u00dfe 200a, 69118 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alena","family":"Bork","sequence":"additional","affiliation":[{"name":"Department of Orthopedics, Heidelberg University Hospital, Schlierbacher Landstra\u00dfe 200a, 69118 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-2481-7151","authenticated-orcid":false,"given":"Malte","family":"Wellbrock","sequence":"additional","affiliation":[{"name":"Orthopedic Research Center, Kiel University, Michaelisstr. 5, 24105 Kiel, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6487-030X","authenticated-orcid":false,"given":"Axel","family":"Horsch","sequence":"additional","affiliation":[{"name":"Department of Orthopedics, Heidelberg University Hospital, Schlierbacher Landstra\u00dfe 200a, 69118 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ghazal","family":"Pourbozorg","sequence":"additional","affiliation":[{"name":"Orthopedic Research Center, Kiel University, Michaelisstr. 5, 24105 Kiel, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-2075-9550","authenticated-orcid":false,"given":"Simone","family":"Gantz","sequence":"additional","affiliation":[{"name":"Orthopedic Research Center, Kiel University, Michaelisstr. 5, 24105 Kiel, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-8877-1102","authenticated-orcid":false,"given":"Reza","family":"Sorbi","sequence":"additional","affiliation":[{"name":"Department of Orthopedics and Trauma Surgery, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Stra\u00dfe 3, 24105 Kiel, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S\u00e9bastien","family":"Hagmann","sequence":"additional","affiliation":[{"name":"Department of Orthopedics, Heidelberg University Hospital, Schlierbacher Landstra\u00dfe 200a, 69118 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8392-7829","authenticated-orcid":false,"given":"Yannic","family":"Bangert","sequence":"additional","affiliation":[{"name":"Department of Orthopedics, Heidelberg University Hospital, Schlierbacher Landstra\u00dfe 200a, 69118 Heidelberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1714-2171","authenticated-orcid":false,"given":"Babak","family":"Moradi","sequence":"additional","affiliation":[{"name":"Department of Orthopedics and Trauma Surgery, University Medical Center Schleswig-Holstein, Campus Kiel, Arnold-Heller-Stra\u00dfe 3, 24105 Kiel, Germany"},{"name":"Orthopedic Research Center, Kiel University, Michaelisstr. 5, 24105 Kiel, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1186\/s40634-020-00282-2","article-title":"Platelet-rich plasma (PRP) as therapy for cartilage, tendon and muscle damage\u2014German working group position statement","volume":"7","author":"Tischer","year":"2020","journal-title":"J. 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