Fibroblast growth factor 21 (FGF21) is a protein that in mammals is encoded by the FGF21 gene. The protein encoded by this gene is a member of the fibroblast growth factor (FGF) family which possess broad mitogenic and cell survival activities, and are involved in a variety of biological processes including embryonic development, cell growth, morphogenesis, tissue repair, tumor growth and invasion. A proliferation assay was conducted to detect the bioactivity of recombinant rat FGF21 using Balb/c 3T3 cells. Briefly, 3T3 cells were seeded into triplicate wells of 96-well plates at a density of 4,000 cells/well and allowed to attach overnight, then the medium was replaced with various concentrations of FGF21 diluted with serum-free standard DMEM. After incubated for 48h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8(CCK-8). Briefly, 10 µl of CCK-8 solution was added to each well of the plate, then the absorbance at 450 nm was measured using a microplate reader after incubating the plate for 1-4 hours at 37°C. Proliferation of Balb/c 3T3 cells after incubation with FGF21 for 48h observed by inverted microscope was shown in Figure1. Cell viability was assessed by CCK-8(Cell Counting Kit-8 ) assay after incubation with recombinant FGF21 for 48h. The result was shown in Figure2. It was obvious that FGF21 significantly increased cell viability of 3T3 cells. The ED50 of recombinant rat FGF21 is 0.23 ng/ml.

Figure 2. The dose-effect curve of FGF21 on Balb/c 3T3 cells.