Advanced age impairs bone fracture healing;the underlying mechanism of this phenomenon remains unknown.We determined that apolipoprotein E(ApoE)increases with age and causes poor fracture healing.After deletion of hep...Advanced age impairs bone fracture healing;the underlying mechanism of this phenomenon remains unknown.We determined that apolipoprotein E(ApoE)increases with age and causes poor fracture healing.After deletion of hepatic ApoE expression(ΔApoE),24-month-oldΔApoE mice displayed a 95%reduction in circulating ApoE levels and significantly improved fracture healing.ApoE treatment of aged BMSCs inhibited osteoblast differentiation in tissue culture models;RNA-seq,Western blot,immunofluorescence,and RT-PCR analyses indicated that the Wnt/β-catenin pathway is the target of this inhibition.Indeed,we showed that ApoE had no effect on cultures with stabilizedβ-catenin levels.Next,we determined that Lrp4 serves as the osteoblast cell surface receptor to ApoE,as expression of Lrp4 is required in ApoE-based inhibition of Wnt/β-catenin signaling and osteoblast differentiation.Importantly,we validated this ApoE-Lrp4-Wnt/β-catenin molecular mechanism in human osteoblast differentiation.Finally,we identified an ApoE-neutralizing antibody(NAb)and used it to treat aged,wildtype mice 3 days after fracture surgery resulting in fracture calluses with 35%more bone deposition.Our work here identifies novel liver-to-bone cross-talk and a noninvasive,translatable therapeutic intervention for aged bone regeneration.展开更多
基金supported by a Borden Scholars awardDuke Claude D.Pepper Older Americans Independence Center Pilot Award(P30AG028716)by the NIH/NIA(R01AG081393)。
文摘Advanced age impairs bone fracture healing;the underlying mechanism of this phenomenon remains unknown.We determined that apolipoprotein E(ApoE)increases with age and causes poor fracture healing.After deletion of hepatic ApoE expression(ΔApoE),24-month-oldΔApoE mice displayed a 95%reduction in circulating ApoE levels and significantly improved fracture healing.ApoE treatment of aged BMSCs inhibited osteoblast differentiation in tissue culture models;RNA-seq,Western blot,immunofluorescence,and RT-PCR analyses indicated that the Wnt/β-catenin pathway is the target of this inhibition.Indeed,we showed that ApoE had no effect on cultures with stabilizedβ-catenin levels.Next,we determined that Lrp4 serves as the osteoblast cell surface receptor to ApoE,as expression of Lrp4 is required in ApoE-based inhibition of Wnt/β-catenin signaling and osteoblast differentiation.Importantly,we validated this ApoE-Lrp4-Wnt/β-catenin molecular mechanism in human osteoblast differentiation.Finally,we identified an ApoE-neutralizing antibody(NAb)and used it to treat aged,wildtype mice 3 days after fracture surgery resulting in fracture calluses with 35%more bone deposition.Our work here identifies novel liver-to-bone cross-talk and a noninvasive,translatable therapeutic intervention for aged bone regeneration.
