IADR Abstract Archives
Bone Homeostasis Requires Control of Hypoxia-inducible Factor-2α
Objectives: To identify the function of HIF-2α in osteoclasts using constitutive HIF-2α knockout (KO) mice and conditional knock out mice with osteoclast-specific depletion of HIF-2α.
Methods: The role of HIF-2α was investigated by overexpression using adenovirus or knockdown analysis using primary cultured cells from knockout mice. To determine the regulatory function of HIF-2α in bone metabolism, we examined the bone microarchitecture in osteoclast conditional knockout mice using a high-resolution micro-CT system and analyzed bone mass using a bone histomorphometry analysis after H&E and TRAP staining.
Results: Overexpression of Epas1 in BMM upregulated various genes involved in both osteoclast differentiation and osteoclast fusion. The HIF-2α inhibitor, ZINC04179524, blocked RANKL-mediated osteoclastogenesis and osteoclast maturation. In addition, inhibition of TRAF6 with a TRAF6 decoy peptide blocked the effects of HIF-2α overexpression on RANKL-mediated osteoclast differentiation and maturation.
Osteoclast-specific HIF-2α KO mice have augmented bone formation. MicroCT and quantitative analyses (BV/TV, Tb.Th, Tb.Sp and Tb. N) addressed that osteoclast-specific depletion of HIF-2α increased bone mineral density. Bone histomorphometric analyses with H&E and TRAP staining showed that N.Oc/BS and Oc.S/BS were significantly decreased in osteoclast-specific HIF-2α KO mice whereas N.Ob/BS and Ob.S/BS were not changed (not significant), which indicates that specific depletion of HIF-2α in osteoclasts increased bone mineral density by preventing bone resorption.
Conclusions: These results indicate that HIF-2α may be a critical key in maintenance of bone homeostasis.
Methods: The role of HIF-2α was investigated by overexpression using adenovirus or knockdown analysis using primary cultured cells from knockout mice. To determine the regulatory function of HIF-2α in bone metabolism, we examined the bone microarchitecture in osteoclast conditional knockout mice using a high-resolution micro-CT system and analyzed bone mass using a bone histomorphometry analysis after H&E and TRAP staining.
Results: Overexpression of Epas1 in BMM upregulated various genes involved in both osteoclast differentiation and osteoclast fusion. The HIF-2α inhibitor, ZINC04179524, blocked RANKL-mediated osteoclastogenesis and osteoclast maturation. In addition, inhibition of TRAF6 with a TRAF6 decoy peptide blocked the effects of HIF-2α overexpression on RANKL-mediated osteoclast differentiation and maturation.
Osteoclast-specific HIF-2α KO mice have augmented bone formation. MicroCT and quantitative analyses (BV/TV, Tb.Th, Tb.Sp and Tb. N) addressed that osteoclast-specific depletion of HIF-2α increased bone mineral density. Bone histomorphometric analyses with H&E and TRAP staining showed that N.Oc/BS and Oc.S/BS were significantly decreased in osteoclast-specific HIF-2α KO mice whereas N.Ob/BS and Ob.S/BS were not changed (not significant), which indicates that specific depletion of HIF-2α in osteoclasts increased bone mineral density by preventing bone resorption.
Conclusions: These results indicate that HIF-2α may be a critical key in maintenance of bone homeostasis.