Platelet Counts in Insoluble Platelet-Rich Fibrin Clots: A Direct Method for Accurate Determination.

Yutaka Kitamura,Tomoyuki Kawase,Kazuhiro Okuda,Hideo Kawabata,Takaaki Tanaka,Kazushige Isobe,Kohya Uematsu,Koh Nakata,Masayuki Nakamura,Taisuke Watanabe

doi:10.3389/fbioe.2018.00004

Abstract

Platelet-rich fibrin (PRF) clots have been used in regenerative dentistry most often, with the assumption that growth factor levels are concentrated in proportion to the platelet concentration. Platelet counts in PRF are generally determined indirectly by platelet counting in other liquid fractions. This study shows a method for direct estimation of platelet counts in PRF. To validate this method by determination of the recovery rate, whole-blood samples were obtained with an anticoagulant from healthy donors, and platelet-rich plasma (PRP) fractions were clotted with CaCl2 by centrifugation and digested with tissue-plasminogen activator. Platelet counts were estimated before clotting and after digestion using an automatic hemocytometer. The method was then tested on PRF clots. The quality of platelets was examined by scanning electron microscopy and flow cytometry. In PRP-derived fibrin matrices, the recovery rate of platelets and white blood cells was 91.6 and 74.6%, respectively, after 24 h of digestion. In PRF clots associated with small and large red thrombi, platelet counts were 92.6 and 67.2% of the respective total platelet counts. These findings suggest that our direct method is sufficient for estimating the number of platelets trapped in an insoluble fibrin matrix and for determining that platelets are distributed in PRF clots and red thrombi roughly in proportion to their individual volumes. Therefore, we propose this direct digestion method for more accurate estimation of platelet counts in most types of platelet-enriched fibrin matrix.

Highlights

Owing to their higher growth factor levels, platelet-rich plasma (PRP) and other platelet concentrates have been used for tissue regeneration in a wide range of medical fields, including dentistry (Marx, 2004; Meschi et al, 2016; Panda et al, 2016)
It was believed that leukocyte- and platelet-rich fibrin does not contain high concentrations of growth factors (Dohan et al, 2006; Gassling et al, 2009), and positive effects of Platelet-rich fibrin (PRF) on tissue regeneration were thought to be mainly attributable to the fibrin architecture that effectively functions as a cellular scaffold (Dohan Ehrenfest et al, 2010; Perez et al, 2014)
The PRP-derived fibrin matrix (PRP-FM) did not form in the absence of the glass beads (GBs) and/or CaCl2 (Figure 1A)

Summary

Introduction

Owing to their higher growth factor levels, platelet-rich plasma (PRP) and other platelet concentrates have been used for tissue regeneration in a wide range of medical fields, including dentistry (Marx, 2004; Meschi et al, 2016; Panda et al, 2016). It was believed that leukocyte- and platelet-rich fibrin does not contain high concentrations of growth factors (Dohan et al, 2006; Gassling et al, 2009), and positive effects of PRF on tissue regeneration were thought to be mainly attributable to the fibrin architecture that effectively functions as a cellular scaffold (Dohan Ehrenfest et al, 2010; Perez et al, 2014). The characteristics of the presence of growth factors and the number of platelets distributed in these fibrin matrices and other fractions remain poorly understood

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