Objective       To detect the expression of dentin matrix protein 1 (DMP1) and bone formation antagonist sclerostin (SOST) in the tibia of unloaded mice

and the expression of SOST in wild type mice and DMP1 knockout mice in order to investigate the possible function and mechanism of DMP1 in bone loss process during unloading.       Methods        Five 1-month-old wild type B6 mice was suspended by tail for 1 month. Another 5 mice served as control. HE staining was used to observe the morphological changes of the tibia

immunohistochemical assay were used to detect the expression of DMP1 and SOST in the tibia

and real-time PCR was employed to test the mRNA expression of Dmp1. In addition

SOST expression was also detected in 2-month-old Dmp1 knockout (KO) mice.       Results       Pathological observation showed more sparse trabeculae and thinner cortical bone in the unloaded mice than the control. Both immunohistochemical study and real-time PCR showed that expression of DMP1 and SOST were increased in unloaded tibia compared to the control (P0.05

P0.01). In addition

SOST expression was also increased in Dmp1 KO mice.       Conclusion       The expression of DMP1 at both protein and mRNA levels is increased in the osteocytes of unloaded mice

indicating that osteocytes secret more DMP1 after accepting unloading signals. SOST plays inhibitory role in bone formation. The increased expression in Dmp-1 KO mice and unloading mice suggests that bone loss in unloading mice and Dmp1 KO mice may share the same mechanisms through SOST pathway.