RUNX1 and osteoporosis: AAV-Runx1 overexpression can rescue bone loss in osteoporosis by regulating osteoblast proliferation and differentiation and cooperate with Cbfβ.21 Runx1 overexpression in calvarial cells with conventional Runx2 knockout (Runx2−/−) rescued osteogenesis and mineralization, as shown by ALP and von Kossa staining, respectively, indicating that Runx1 could compensate for the loss of Runx2 expression.