AUTHOR=Kargarpour Zahra , Nasirzade Jila , Panahipour Layla , Miron Richard J. , Gruber Reinhard 

TITLE=Liquid PRF Reduces the Inflammatory Response and Osteoclastogenesis in Murine Macrophages

JOURNAL=Frontiers in Immunology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.636427

DOI=10.3389/fimmu.2021.636427

ISSN=1664-3224

ABSTRACT=Macrophage activation and osteoclastogenesis are hallmarks of inflammatory osteolysis and may be targeted by the local application of liquid platelet-rich fibrin (PRF). Liquid PRF is produced by a hard spin of blood in the absence of clot activators and anticoagulants, thereby generating an upper platelet-poor plasma (PPP) layer, a cell-rich buffy coat layer (BC; termed concentrated-PRF (C-PRF)), and the remaining red clot (RC) layer. Heating PPP has been shown to generate an albumin gel (Alb-gel) that when mixed back with C-PRF generates Alb-PRF. The advantage of Alb-PRF is its extended working properties when implanted in vivo from a 2-3 week biomaterial (traditional PRF) to 4-6 months (Alb-PRF). Evidence has demonstrated that traditional solid PRF holds a potent anti-inflammatory capacity and reduces osteoclastogenesis. Whether liquid PRF is capable of also suppressing an inflammatory response and the formation of osteoclasts remains open. In the present study, RAW 264.7 and primary macrophages were exposed to lipopolysaccharides (LPS) and lactoferrin in the presence or absence of lysates prepared by freeze-thawing of liquid PPP, BC, Alb-gel, and RC. For osteoclastogenesis, primary macrophages were exposed to RANKL in the presence or absence of PPP, BC, Alb-gel, and RC lysates. We show here that it is mainly the lysates prepared from PPP and BC that consistently reduced the LPS and lactoferrin-induced expression of interleukin 6 (IL6) in macrophages, as determined by RT-PCR and immunoassay. With respect to osteoclastogenesis, lysates from PPP and BC but particularly from RC reduced the expression of osteoclast marker genes tartrate-resistant acid phosphatase (TRAP) and cathepsin K, as well as TRAP histochemical staining. These findings suggest that liquid PRF holds a potent in vitro heat-sensitive anti-inflammatory activity in macrophages that goes along with an inhibition of osteoclastogenesis.