Aptscl56 could bind to sclerostin in the serum of the selected OI patients and healthy controls via targeting loop3. In our in vitro studies, it was validated by western blot analysis that the binding between aptscl56 and recombinant full-length sclerostin were blocked if aptscl56 was pre-bound to exogenous loop3. This evidence concerns the gene SOST and osteogenesis imperfecta.