Fibroblast-like synoviocyte (FLS) proliferation study by MTT assay: effect of nerve growth factor (NGF) on the proliferation of cultured FLSs derived from patients with psoriatic arthritis. Third-passage FLSs (5,000 cells per 200 μL of Dulbecco's modified Eagle's medium complete medium) in 96-well plates were cultured for 5 days with NGF-β (100 ng/mL) with or without anti-NGF neutralizing antibody (neut-ab). The optimal dose (OD) of NGF was determined by performing a dose response curve. Data are expressed as the mean ± standard deviation of triplicate cultures from three independent experiments. NGF demonstrated a significant mitogenic effect on FLSs. NGF neutralizing antibody-inhibited NGF-induced proliferation further substantiates that NGF-induced proliferation of FLSs is a specific biological action of NGF. MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.