The consumption of a high-fat diet(HFD)has been linked to osteoporosis and an increased risk of fragility fractures.However,the specific mechanisms of HFD-induced osteoporosis are not fully understood.Our study shows that exposure to an HFD induces premature senescence in bone marrow mesenchymal stem cells(BMSCs),diminishing their proliferation and osteogenic capability,and thereby contributes to osteoporosis.Transcriptomic and chromatin accessibility analyses revealed the decreased chromatin accessibility of vitamin D receptor(VDR)-binding sequences and decreased VDR signaling in BMSCs from HFD-fed mice,suggesting that VDR is a key regulator of BMSC senescence.Notably,the administration of a VDR activator to HFD-fed mice rescued BMSC senescence and significantly improved osteogenesis,bone mass,and other bone parameters.Mechanistically,VDR activation reduced BMSC senescence by decreasing intracellular reactive oxygen species(ROS)levels and preserving mitochondrial function.Our findings not only elucidate the mechanisms by which an HFD induces BMSC senescence and associated osteoporosis but also offer new insights into treating HFD-induced osteoporosis by targeting the VDR-superoxide dismutase 2(SOD2)-ROS axis.

The consumption of a high-fat diet(HFD)has been linked to osteoporosis and an increased risk of fragility fractures.However,the specific mechanisms of HFD-induced osteoporosis are not fully understood.Our study shows that exposure to an HFD induces premature senescence in bone marrow mesenchymal stem cells(BMSCs),diminishing their proliferation and osteogenic capability,and thereby contributes to osteoporosis.Transcriptomic and chromatin accessibility analyses revealed the decreased chromatin accessibility of vitamin D receptor(VDR)-binding sequences and decreased VDR signaling in BMSCs from HFD-fed mice,suggesting that VDR is a key regulator of BMSC senescence.Notably,the administration of a VDR activator to HFD-fed mice rescued BMSC senescence and significantly improved osteogenesis,bone mass,and other bone parameters.Mechanistically,VDR activation reduced BMSC senescence by decreasing intracellular reactive oxygen species(ROS)levels and preserving mitochondrial function.Our findings not only elucidate the mechanisms by which an HFD induces BMSC senescence and associated osteoporosis but also offer new insights into treating HFD-induced osteoporosis by targeting the VDR-superoxide dismutase 2(SOD2)-ROS axis.

Although mesenchymal stem cell-derived exosomes (MSC-exos) have been shown to have therapeutic effects in experimental periodontitis, their drawbacks, such as low yield and limited efficacy, have hampered their clinical application. These drawbacks can be largely reduced by replacing the traditional 2D culture system with a 3D system. However, the potential function of MSC-exos produced by 3D culture (3D-exos) in periodontitis remains elusive. This study showed that compared with MSC-exos generated via 2D culture (2D-exos), 3D-exos showed enhanced anti-inflammatory effects in a ligature-induced model of periodontitis by restoring the reactive T helper 17 (Th17) cell/Treg balance in inflamed periodontal tissues. Mechanistically, 3D-exos exhibited greater enrichment of miR-1246, which can suppress the expression of Nfat5, a key factor that mediates Th17 cell polarization in a sequence-dependent manner. Furthermore, we found that recovery of the Th17 cell/Treg balance in the inflamed periodontium by the local injection of 3D-exos attenuated experimental colitis. Our study not only showed that by restoring the Th17 cell/Treg balance through the miR-1246/Nfat5 axis, the 3D culture system improved the function of MSC-exos in the treatment of periodontitis, but also it provided a basis for treating inflammatory bowel disease (IBD) by restoring immune responses in the inflamed periodontium.
Colitis ; Exosomes ; Humans ; Periodontitis/therapy* ; Periodontium ; T-Lymphocytes, Regulatory ; Th17 Cells

The sodium hydrogen exchanger 1 (NHE1), which functions in maintaining the ratio of Na+ and H+ ions, is widely distributed in cell plasma membranes. It plays a prominent role in pH balancing, cell proliferation, differentiation, adhesion, and migration. However, its exact subcellular location and biological functions in Toxoplasma gondii are largely unclear. In this study, we cloned the C-terminal sequence of T. gondii NHE1 (TgNHE1) incorporating the C-terminal peptide of NHE1 (C-NHE1) into the pGEX4T-1 expression plasmid. The peptide sequence was predicted to have good antigenicity based on the information obtained from an immune epitope database. After induction of heterologous gene expression with isopropyl-b-D-thiogalactoside, the recombinant C-NHE1 protein successfully expressed in a soluble form was purified by glutathione sepharose beads as an immunogen for production of a rabbit polyclonal antiserum. The specificity of this antiserum was confirmed by western blotting and immunofluorescence. The antiserum could reduce T. gondii invasion into host cells, indicated by the decreased TgNHE1 expression in T. gondii parasites that were pre-incubated with antiserum in the process of cell entry. Furthermore, the antiserum reduced the virulence of T. gondii parasites to host cells in vitro, possibly by blocking the release of Ca2+. In this regard, this antiserum has potential to be a valuable tool for further studies of TgNHE1.
Animals ; Cell Line ; Immune Sera/genetics/immunology/*metabolism ; Male ; Mice ; Protozoan Proteins/genetics/*metabolism ; Rabbits ; Recombinant Proteins/immunology ; Sheep ; Sodium-Hydrogen Antiporter/genetics/immunology/*metabolism ; Toxoplasma/genetics/immunology/*metabolism ; Toxoplasmosis/parasitology/prevention & control