VIPR1 and arthritic joint disease: VPAC1 expression was significantly higher (p = 0.041) in monocytes from healthy donors compared with mature osteoclasts (Figure 1A) whereas in early arthritis patients a significant down-regulation of both receptors (VPAC1 and VAPC2) was observed after osteoclastogenesis (p = 0.001 and p = 0.002, respectively) (Figure 1B).