ABSTRACT
In the present study, we examined the role of MDM2 in the angiogenesis process and its potential association with the sprouting of endothelial tip cells. To address this, we performed hypoxia-treated gastric cancer cells (HGC-27) to quantitative RT-PCR and Western blot analysis to measure the levels of MDM2 and VEGF-A mRNA and protein expression. Subsequently, we employed siRNA to disrupt MDM2 expression, followed by hypoxia treatment. The expression levels of MDM2 and VEGF-A mRNA and protein were subsequently reassessed. Additionally, ELISA was utilized to quantify the secretion levels of VEGF-A in each experimental group. A conditioned medium derived from HGC-27 cells treated with different agents was employed to assess its influence on the formation of EA.hy926 endothelial tip cells, using various techniques including Transwell plates migration assays, wound healing experiments, vascular formation assays, scanning electron microscopy, and immunofluorescence staining. These findings demonstrated that the in vitro knockdown of MDM2 in the conditioned medium exhibited significant inhibitory effects on endothelial cell migration, wound healing, and vascular formation. Additionally, the intervention led to a reduction in the presence of CD34+ tip cells and the formation of filopodia in endothelial cells, while partially restoring the integrity of tight junctions. Subsequent examination utilizing RNA-seq revealed that the suppression of MDM2 in HGC-27 cells resulted in the downregulation of the PI3K/AKT signaling pathway. Consequently, this downregulation led to an elevation in angiogenic effects induced by hypoxia.
ABSTRACT
Bending sensing was realized by constructing a tapered four-core optical fiber (TFCF) sensor. The four-core fiber (FCF) between the fan-in and fan-out couplers was tapered and the diameter became smaller, so that the distance between the four cores arranged in a square became gradually smaller to produce supermodes. The two ends of the TFCF were respectively connected to the fan-in and fan-out couplers so that the individual cores in the FCF could link to the separate single-mode fibers. A broadband light source (superluminescent diodes (SLD)) spanning 1250-1650 nm was injected into any one of the four cores, and the orientation was thus determined. In the tapering process, the remaining three cores gradually approached the excitation core in space to excite several supermodes based on the tri-core structure first, and then transited to the quadruple-core structure. The field distributions of the excited supermodes were asymmetric due to the corner-core excitation scheme, and the interference thus resulted in a higher measurement sensitivity. When the diameter of the TFCF was 7.5 µm and the tapered length was 2.21 mm, the sensitivity of the bending sensor could reach 16.12 nm/m-1.
ABSTRACT
A weakly-coupled multicore fiber can generate supermodes when the multi-cores are closer to enter the evanescent power coupling region. The high sensitivity strain sensors using tapered four-core fibers (FCFs) were demonstrated. The fan-in and fan-out couplers were used to carry out light coupling between singlemode fibers and the individual core of the FCFs. A broadband lightsource from superlumminescent diodes (SLDs) was launched into one of the four cores arranged in a rectangular configuration. When the FCF was substantially tapered, the asymmetric supermodes were produced to generate interferences through this corner-core excitation scheme. During tapering, the supermodes were excited based on a tri-core structure initially and then transited to a rectangular quadruple-core structure gradually to reach the sensitivity of 185.18 pm/µÔ under a tapered diameter of 3 µm. The asymmetric evanescent wave distribution due to the corner-core excitation scheme is helpful to increase the optical path difference (OPD) between supermodes for improving the strain sensitivity.