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Silver nanoparticles (Ag NPs) have been widely used in bone grafts due to their antimicrobial/antiviral properties. Despite extensive research focused on the cytotoxicity and genotoxicity of Ag NPs, little is known of their effect on cell differentiation. In this study, the uptake of Ag NPs and its effect on the osteogenic differentiation of human mensenchymal stem cells (hMSCs) were investigated in vitro. Ag NPs with a diameter of -30 nm were prepared. The hMSCs were exposed to different concentrations of Ag NPs, i.e., 0, 10, 50 and 100 microg/mL. The results show that Ag NPs cause cytotoxicity of hMSCs. It is also demonstrated that the uptake of Ag NPs does not affect the alkaline phosphatase activity, osteocalcin gene expression, osteopontin expression and mineralization level of hMSCs. The uptake of Ag NPs does not influence the osteogenic differentiation of hMSCs. This will give a positive reference for the application of Ag NPs in bone tissue engineering, especially their incorporation with stem cells in bone grafts.

Exposure to microgravity results in cardiovascular deconditioning, and cerebrovascular oxidative stress injury has been suggested to occur. To elucidate the mechanism for this condition, we investigated whether simulated microgravity induces mitochondrial dysfunction in rat arteries. Four-week hindlimb unweighting (HU) was used to simulate microgravity in rats. Mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (Δψm), mitochondrial permeability transition pore (mPTP) opening, mitochondrial respiratory control ratio (RCR), MnSOD/GPx activity and expression, and mitochondrial malondialdehyde (MDA) were examined in rat cerebral and mesenteric VSMCs. Compared with the control rats, mitochondrial ROS levels, mPTP opening, and MDA content increased significantly (P<0.001, P<0.01, and P<0.01, respectively), Δψm, RCR, MnSOD/GPx activity (P<0.001 for Δψm and RCR; P<0.05 for MnSOD; and P<0.001 for GPx activity) and protein abundance of mitochondrial MnSOD/GPx-1 decreased (P<0.001 for MnSOD and GPx-1) in HU rat cerebral but not mesenteric arteries. Chronic treatment with NADPH oxidase inhibitor apocynin and mitochondria-targeted antioxidant mitoTempol promoted recovery of mitochondrial function in HU rat cerebral arteries, but exerted no effects on HU rat mesenteric arteries. Therefore, simulated microgravity resulted in cerebrovascular mitochondrial dysfunction, and crosstalk between NADPH oxidase and mitochondria participated in the process.

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