Morphology of cultured fibroblast-like synovial (FLS) cells and co-cultured dorsal root ganglion (DRG) neurones. (a) Mono-culture of FLS cells. (b) Co-culture of FLS cells and DRG neurones. The DRG neurones show neurone-specific enolase-like immunoreactivity (white staining indicated by stars). (c,d) Co-culture of FLS cells and DRG neurones. The processes of DRG neurones are indicated with arrows. Note the contact between the DRG neurones and the FLS cells (d). Scale bars: 10 μm (a); 30 μm (b,c); 10 μm (d).