GARP Regulates the Immune Capacity of a Human Autologous Platelet Concentrate

Abstract

Autologous platelet concentrates, like liquid platelet rich fibrin (iPRF), optimize wound healing; however, the underlying immunological mechanisms are poorly understood. Platelets, the main cellular component of iPRF, highly express the protein, Glycoprotein A repetitions predominant (GARP), on their surfaces. GARP plays a crucial role in maintaining peripheral tolerance, but its influence on the immune capacity of iPRF remains unclear. This study analyzed the interaction of iPRF with immune cells implicated in the wound healing process (human monocyte derived macrophages and CD4+ T cells) and evaluated the distinct influence of GARP on these mechanisms in vitro. GARP was determined to be expressed on the surface of platelets and to exist as a soluble factor in iPRF. Platelets derived from iPRF and iPRF itself induced a regulatory phenotype in CD4+ T cells, shown by increased expression of Foxp3 and GARP as well as decreased production of IL-2 and IFN-γ. Application of an anti-GARP antibody reversed these effects. Additionally, iPRF polarized macrophages to a “M0/M2-like” phenotype in a GARP independent manner. Altogether, this study demonstrated for the first time that the immune capacity of iPRF is mediated in part by GARP and its ability to induce regulatory CD4+ T cells.

Towards optimized tissue regeneration: a new 3D printable bioink of alginate/cellulose hydrogel loaded with thrombocyte concentrate

“…The regulation of immune capacity by inducing regulatory CD4 + T cells is attributed to GARP, as previously described in native PRF (Trzeciak et al, 2022). Furthermore, native PRF polarized macrophages to a "M0/M2-like" phenotype (Trzeciak et al, 2022). Given the significant overlap in proteome and secretome between native PRF and the 3D-printed constructs, our results suggest that the printed constructs may exhibit similar antiinflammatory effects.…”

“…This differentiation process is associated with the Glycoprotein A repetitions predominant (GARP), a transmembrane protein and TGF-β binding partner. The regulation of immune capacity by inducing regulatory CD4 + T cells is attributed to GARP, as previously described in native PRF ( Trzeciak et al, 2022 ). Furthermore, native PRF polarized macrophages to a “M0/M2-like” phenotype ( Trzeciak et al, 2022 ).…”

“…Therefore, it is heavily used in regenerative and reconstructive surgery such as orthopedic procedures, cardiac surgery, plastic surgery, gynecology, urology, and medical esthetics as well as craniomaxillofacial-surgery ( Gupta et al, 2021 ; Puricelli et al, 2023 ). The different cells involved, like thrombocytes and leukocytes confined in the structure-given fibrin net of these blood-derived products, release growth factors that can further interact with other cell types to initiate angiogenesis and stimulate immunological as well as other cellular processes involved in tissue regeneration ( Miron et al, 2017a ; Trzeciak et al, 2022 ). As a great advantage, the chair-side production and simple processing are timesaving and cost-efficient.…”

Platelet-rich fibrin as an autologous biomaterial for bone regeneration: mechanisms, applications, optimization

“…Moreover, PRF promoted the expression of M2 type macrophage markers ARG1 and CD206, activated the TGF-β signaling pathway or increased the activity of the TGF-β signaling pathway to promote M2 type macrophage activation ( Zhang et al, 2020 ; Kargarpour et al, 2021b ; Kargarpour et al, 2023 ). At the same time, PRF promotes the polarization of monocyte-derived macrophages to an “M0/M2-like” phenotype and promotes wound healing by inducing the conversion of CD4 + T cells to a regulatory phenotype via glycoprotein A repeat dominant protein (GARP) ( Trzeciak et al, 2022 ). At the transcriptional level, PRF exerted an anti-inflammatory effect by decreasing the expression of IL-1β, NLRP3, CAS11, and IL-18 in LPS-induced macrophages, reducing ROS release in RAW 264.7 cells activated by LPS, and inhibiting macrophage pyroptosis ( Sordi et al, 2022 ).…”

New strategy of personalized tissue regeneration: when autologous platelet concentrates encounter biomaterials

“…Venous blood without anticoagulant is centrifuged at 60 × g for 3 min and the pale-yellow supernatant is iPRF. Reduced time and speed decrease blood cell aggregation at the tube bottom, significantly increasing platelet and leukocyte content homogenously distributed within the dense fibrin network (Trzeciak et al, 2022). The lowspeed centrifugation allows iPRF to remain injectable liquid initially for ~15 min before gradually transforming into gel, enabling minimally invasive injection into defect sites or topical wound coating, as well as facile combination with biomaterials (Zhang et al, 2020).…”