PA induces osteoclastogenesis in the absence of RANKL via increased TNFα expression, whereas combined treatment with PA and OA inhibits this effect. (A) a) TRAP staining for osteoclasts in RAW 264.7 cells after 5 days of treatment with PA, OA, or PA and OA. b) Average size of osteoclasts treated with PA, OA, or PA and OA. Average size was calculated from measurement of 173 osteoclasts in control treatment, 108 osteoclasts in PA-treated cultures, 109 osteoclasts in OA-treated cultures, and 133 osteoclasts in cultures treated with combination of PA and OA. (B) RT-PCR analysis for TRAP and TNFα mRNAs; **p < 0.01, ***p < 0.001, n = 4 to 9. (C) TRAP staining for osteoclasts in RAW 264.7 cells treated for 5 days with PA, anti-TNFα antibody, or PA and anti-TNFa antibody. (D) RT-PCR analysis for TRAP and TNFα mRNAs. *p < 0.05, ***p < 0.001, n = 3–9.