ABSTRACT
BACKGROUND: Bone marrow mesenchymal stem cells (BMSCs) and BMSCs-derived exosomes have similar functions, but the regulatory mechanism underlying the release of exosomes is still unclear. OBJECTIVE: To investigate the role of GW4869, an inhibition of neutral sphingomyelinase 2, in the release of exosomes in BMSCs and the influence of GW4869 on BMSCs proliferation. METHODS: Rat BMSCs were divided into three groups: normal control group, 24-hour GW4869 treatment group and withdrawal of GW4869 for 24 hours group (24-hour GW4869 treatment followed by 24-hour successive culture with drug withdrawal). Cultured cells were collected to extract exosomes by ultracentrifugation. Western blot was used to detect exosome-associated proteins CD63 and tumor susceptibility gene 101 (TSG101). The concentration and size distribution of exosomes were measured using nanoparticle tracking analysis. BCA was used to test the level of total proteins in exosomes. Live cell imaging system was used to observe the influence of GW4869 on BMSCs proliferation. RESULTS AND CONCLUSION: (1) Western blot results showed that exosomes expressed marker proteins such as CD63, TSG101. (2) Findings from the nanoparticle tracking analysis confirmed that the size of released exosomes was about 114 nm. (3) Significantly reduced release of exosomes was found in the two treatment groups compared with the normal control group (P < 0.01), but there was no significant difference between 24-hour GW4869 treatment group and withdrawal of GW4869 for 24 hours group (P > 0.05). (4) No significant difference in the proliferation of BMSCs was found among the three groups (P > 0.05). To conclude, 24-hour W4869 can inhibit the release of exosomes by BMSCs and this inhibitory effect is still sustained within 24 hours after drug withdrawal. However, GW4869 has no influence on the proliferation of BMSCs.
ABSTRACT
Objective Acute lung injury induced by variety causes can be reduced by mesenchymal stem cells.Some studies have shown that mesenchymal stem cell-derived exosomes have similar features with mesenchymal stem cell,but its role in acute lung injury is less studied.The study was to investigate the protective role and underlying mechanisms of bone marrow mesenchymal stem cell-derived exosomes (BMSC-DEs) on smoke inhalation injury (SⅡ) in rats.Methods Thirty Wistar rats were randomly divided into 3 equal groups:normal control group,smoke inhalation injury (SⅡ) model group and bone marrow mesenchymal stem cell-derived exosomes (BMSC-DEs) treated group.12 h after establishing the SⅡ model,BMSC-DEs treated group was injected with 0.5 mL BMSC-DEs (derived from 4× 106 BMSCs),and normal control group and SⅡ model group were injected with equivalent volume of normal saline.7 days later,samples were collected.The histopathologic changes of lung were observed after HE staining;BCA was used to test the amounts of total protein in bronchoalveolar lavage fluid (BALF);Enzyme linked immunosorbent assay was used to test the levels of tumor necrosis factor-α (TNF-α) and keratinocyte growth factor (KGF) in the lung tissue;Immunohistochemical was used to test the levels of pulmonary surfactant protein C(SP-C).Results The BALF levels of total protein of SⅡ group was significantly higher than those of normal control group (P＜0.01) and BMSC-DEs groups(P＜0.05);Compared with normal group [(0.164±0.021) ng/L],the levels of tumor necrosis factor-α of SII and BMSC-DEs groups [(0.355±0.106)、(0.234±0.024) ng/L] (P＜ 0.05) were significantly higher,and SⅡ group was higher than that of BMSC-DEs group(P＜0.01);Compared with normal group,the KGF protein expression level in lung tissue of SⅡ group was significantly lower (P＜0.05),but BMSC-DEs group was higher (P＜0.05).BMSC-DEs group was higher than SⅡ group (P＜0.01);Immunohistochemistry showed that the SP-C expression level in lung tissue of SⅡ group was significantly lower than those of other groups (P＜0.05).There was no statistically difference between BMSC-DEs group and control group (P＞0.05).Conclusion BMSC-DEs has a protective effect of smoke inhalation injury rats,the underlying mechanism may be related to BMSC-DEs to reduce inflammation and promote restoration of the alveolar epithelial type Ⅱ.
ABSTRACT
<p><b>OBJECTIVE</b>The purpose of this study was to qualitatively and quantitatively analyze the initial force system of "rocking-chair archwire" on every tooth.</p><p><b>METHODS</b>Three-dimensional finite element model of "rocking-chair archwire" was set up, and nonlinear method was used to analyze the force system.</p><p><b>RESULTS</b>The archwire exerted intruding force, labial force, lingual-root torque and mesial-labial moment on incisors; Extruding force, lingual-root torque and mesial-labial moment were applied on canines and premolars; The archwire also created intruding force, buccal force, buccal-root torque and mesial-labial moment on molars.</p><p><b>CONCLUSIONS</b>"rocking-chair archwire" produced a complicated force system. While intruding incisors, molars and extruding premolars. It has a tendency to induce tooth rotation and tipping.</p>