MMP9 and osteoporosis: MMP-9 is implicated in osteoclast-induced bone resorption.50, 51 Increased expression of MMP-9 has been described in RA patient serum.52 The previous study suggested that MMP-9 was an important downstream effector molecule driving pathologic systemic bone loss observed in osteoporosis.53 Many studies employed MMP-9 as osteoclastogenesis-related markers.12, 47, 54 Our study demonstrated that M19 inhibited expressions of MMP-9 during osteoclastogenesis.