Platelet factor 4 (PF4) is a small cytokine belonging to the CXC chemokine family that is also known as chemokine (C-X-C motif) ligand 4 (CXCL4). This chemokine is released from alpha-granules of activated platelets during platelet aggregation, and promotes blood coagulation by moderating the effects of heparin-like molecules. Due to these roles, it is predicted to play a role in wound repair and inflammation. To measure its ability to inhibit the FGF basic-dependent proliferation of HUVEC human umbilical vein endothelial cells, HUVEC cells were seeded into 96-well plates at a density of 3,000 cells/well with 2% serum standard DMEM including 1μg/mL recombinant human FGF1 and various concentrations of recombinant human PF4. After incubated for 48h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10µL of CCK-8 solution was added to each well of the plate, then the absorbance at 450nm was measured using a microplate reader after incubating the plate for 1-2 hours at 37℃. Proliferation of HUVEC cells after incubation with PF4 for 48h observed by inverted microscope was shown in Figure 1. Cell viability was assessed by CCK-8 (Cell Counting Kit-8) assay after incubation with recombinant human PF4 for 48h. The result was shown in Figure 2. It was obvious that PF4 significantly FGF basic-dependent proliferation of HUVEC cells. The ED50 is 3.4μg/mL.
(A)HUVEC cells cultured in DMEM with 1μg/mL FGF1, stimulated with 5μg/mL PF4 for 48h;
(B) Unstimulated HUVEC cells cultured in DMEM with 1μg/mL FGF1 for 48h.
Figure. Inhibition of HUVEC cells proliferation after stimulated with PF4.

Figure. Inhibition of FGF basic-dependent HUVEC proliferation after stimulated with PF4.