Small extracellular vesicles derived from hypoxic preconditioned dental pulp stem cells ameliorate inflammatory osteolysis by modulating macrophage polarization and osteoclastogenesis

Extensive macrophage inflammatory responses and osteoclast formation are predominant during inflammatory or infective osteolysis.Mesenchymal stem cell(MSC)-derived small extracellular vesicles(MSC-sEV)have been shown to exert therapeutic effects on bone defects.However,cultured MSCs are typically exposed to normoxia(21%O2)in vitro,which differs largely from the oxygen concentration in vivo under hypoxic conditions.It is largely unknown whether sEV derived from dental pulp stem cells(DPSCs)cultured under hypoxic conditions(Hypo-sEV)exert better therapeutic effects on lipopolysaccharide(LPS)-induced inflammatory osteolysis than those cultured under normoxic conditions(Nor-sEV)by simultaneously inhibiting the macrophage inflammatory response and osteoclastogenesis.In this study,we show that hypoxia significantly induces the release of sEV from DPSCs.Moreover,Hypo-sEV exhibit significantly improved efficacy in promoting M2 macrophage polarization and suppressing osteoclast formation to alleviate LPS-induced inflammatory calvarial bone loss compared with Nor-sEV.Mechanistically,hypoxia preconditioning markedly alters the miRNA profiles of DPSC-sEV.MiR-210-3p is enriched in Hypo-sEV,and can simultaneously induce M2 macrophage generation and inhibit osteoclastogenesis by targeting NF-κB1 p105,which attenuates osteolysis.Our study suggests a promising potential for hypoxia-induced DPSC-sEV to treat inflammatory or infective osteolysis and identifies a novel role of miR-210-3p in concurrently hindering osteoclastogenesis and macrophage inflammatory response by inhibiting NF-kB1 expression.

Trophic Mode-Dependent Proteomic Analysis Reveals Functional Significance of Light- Independent Chlorophyll Synthesis in Synechocystis sp. PCC 6803

The photosynthetic model organism Synechocystis sp. PCC 6803 can grow in different trophic modes, depending on the availability of light and exogenous organic carbon source. However, how the protein pro- file changes to facilitate the cells differentially propagate in different modes has not been comprehensively investigated. Using isobaric labeling-based quantitative proteomics, we simultaneously identified and quantified 45% Synechocystis proteome across four different trophic modes, i.e., autotrophic, heterotro- phic, photoheterotrophic, and mixotrophic modes. Among the 155 proteins that are differentially expressed across four trophic modes, proteins involved in nitrogen assimilation and light-independent chlorophyll synthesis are dramatically upregulated in the mixotrophic mode, concomitant with a dramatic increase of PII phosphorylation that senses carbon and nitrogen assimilation status. Moreover, functional study us- ing a mutant defective in light-independent chlorophyll synthesis revealed that this pathway is important for chlorophyll accumulation under a cycled light/dark illumination regime, a condition mimicking day/night cycles in certain natural habitats. Collectively, these results provide the most comprehensive information on trophic mode-dependent protein expression in cyanobacterium, and reveal the functional significance of light-independent chlorophyll synthesis in trophic growth.

The quantitative proteome atlas of a model cyanobacterium

Cyanobacteria are a group of oxygenic photosynthetic bacteria with great potentials in biotechnological applications and advantages as models for photosynthesis research. The subcellular localizations of the majority of proteins in any cyanobacteria remain undetermined, representing a major challenge in using cyanobacteria for both basic and industrial researches. Here, using label-free quantitative proteomics, we map 2027 proteins of Synechocystis sp. PCC6803, a model cyanobacterium, to different subcellular compartments and generate a proteome atlas with such information. The atlas leads to numerous unexpected but important findings, including the predominant localization of the histidine kinases Hik33 and Hik27 on the thylakoid but not the plasma membrane. Such information completely changes the concept regarding how the two kinases are activated. Together, the atlas provides subcellular localization information for nearly 60% proteome of a model cyanobacterium, and will serve as an important resource for the cyanobacterial research community.