The Mechanisms Of Y₂O₃ Nanospheres Induce Apoptosis In Bone Mesenchymal Stem Cells Via Lysosome-mitochondria Mediated Pathway

Rare earth oxide nanoparticals have been largely applied in biological medicine fields due to their unique optical and magnetic properties.Y₂O₃ NPs are largely used as luminescence probes,drug carriers,bone scaffold materials etc.,some researches report that rare earth deposited in the bone are excreted slowly,however,the hazardous effects of Y₂O₃ NSs on bone metabolism have not yet completely expounded.In this study,combining with physicochemical properties of Y₂O₃ NSs systematically explain how Y₂O₃ NSs interact with BMSCs.We synthesized Y₂O₃ NSs with the diameter of 160 nm and characterized via SEM,TEM,DLS.MTT assay indicated that Y₂O₃ NSs led to cytotoxicity of BMSCs in concentration and time dependent manner.We examined the influence of Y₂O₃ NSs on lysosome and mitochondria by Annexin V-FITC/PI staining,endocytic pathways,location in cells,hydrolase enzyme activity,Bid and Bax expression,the release of Cyt C and the activation of Caspase 3.Y₂O₃@YPO4 was synthesized in LSBF by TEM,Zeta,FTIR and Y₂O₃ NSs compared with Y₂O₃@YPO4 in terms of hydrolase enzyme activity and the detection of Cyt C.The pathological analysis was further performed by HE staining,TUNEL assay and immunofluorescence staining of bone.Results showed that Y₂O₃ NSs entered into BMSCs through macropinocytosis,localized in lysosomes,which caused Y₂O₃ NSs dissolution in lysosomal pH.Intracellular release of Y3+ leads to lysosome membrane damage in a phosphate complexation of phophlipid layer manner and formed the spider mesh structure.Lysosomal protease ultimately induced BMSCs apoptosis via Caspase 3 dependent pathway,while Y₂O₃@YPO4 decreased the expression of Caspase 3 and the release of Cyt C.Y₂O₃ NSs lead to hepatic necrosis,alveolar rupture and bone trabecula thinner and lower,nevertheless Y₂O₃@YPO4 eased the abovementioned conditions in vivo.This comprehension acquired from the assessment of toxicity in vitro and vivo associated with Y₂O₃ NSs presents a valuable information for the safe use,and Y₂O₃ NSs based on lysosomal dissolution chemistry as a major predictor of toxicity.