This was manifested by more TRAP+ cells in the trabecular bone of the vertebra and ectopic bone formation within the EP, osteoporosis change in trabecular bone of vertebra and elevated levels of osteoclast marker genes including TRAP and Cathepsin K. We reported that PGRN protected bone from resorption in inflammatory arthritis model21. The gene discussed is CTSK; the disease is osteoporosis.