Abundant FGFR1 and FGFR3 expression in articular chondrocytes. (A) Human articular chondrocytes were incubated with anti-CD32/CD16 monoclonal antibody to block nonspecific antibody binding. FGFR1, FGFR2, FGFR3, and FGFR4 antibodies were incubated with cells, followed by incubation with a secondary antibody, goat-anti-rabbit Alexa Fluor 488. Cells were also incubated with goat-anti-rabbit Alexa 488, or non-immune rabbit serum plus goat-anti-rabbit Alexa Fluor 488 as controls. FGFRs on the plasma membrane of chondrocytes were analyzed with a FACS Calibur instrument and CellQuest software. (B) Human articular chondrocytes in monolayer were subjected to RNA extraction, cDNA synthesis, and qPCR quantification of FGFR isoform expression. * P < 0.05. (C) Human articular chondrocytes in monolayer were directly lysed. Equal amounts of total protein were resolved on a SDS-PAGE gel, followed by transfer and immunoblotting of FGFR isoforms. FGF, fibroblast growth factor; FGFR, FGF receptor; qPCR, quantative polymerase chain reaction.