Skp2/p27 axis regulates chondrocyte proliferation under high glucose induced endoplasmic reticulum stress.

OBJECTIVE: Diabetes mellitus is closely related to osteoarthritis (OA) and may be an independent risk factor for the development of OA. As one of the main characteristics of diabetes, endoplasmic reticulum (ER) stress resulting from glucose metabolism disorder is one of the main causes of cartilage degeneration. The aim of our study is to illuminate the effect of high glucose to chondrocytes (CHs) and the role of Skp2 in high-glucose induced ER stress in CHs. PATIENTS AND METHODS: We compared the ER stress status between healthy and diabetic OA cartilage using Western blot and quantitative reverse-transcription polymerase chain reaction (RT-PCR) methods. Different concentration of glucose was used to culture CHs for both 24 h and 72 h. Furthermore, Tunicamycin (TM) and 4-Phenylbutyric acid (4-PBA) were used to mediate ER stress of CHs, and human recombinant Skp2 protein was used to promote Skp2 expression. CH viability was determined by CCK8 assay, and cell proliferation was determined by flow cytometry. Western and RT-PCR were performed to measure related gene expression. RESULTS: ER stress makers GADD34, GRP78, and MANF were upregulated in diabetic OA cartilage. The long-term high glucose increased GADD34, GRP78, and MANF expression, but decreased collagen II and proliferation of CHs, and Skp2 expression was negative related to the ER stress level. Additionally, Skp2 overexpression partly reversed ER stress-induced collagen II and proliferation suppression by the suppression of p27 expression. CONCLUSIONS: High glucose raises the ER stress in CHs and overexpression of Skp2 promotes CH proliferation under high glucose treatment.

Hybrid metamaterial switching for manipulating chirality based on VO2 phase transition.

Polarization manipulations of electromagnetic waves can be obtained by chiral and anisotropic metamaterials routinely, but the dynamic and high-efficiency modulations of chiral properties still remain challenging at the terahertz range. Here, we theoretically demonstrate a new scheme for realizing thermal-controlled chirality using a hybrid terahertz metamaterial with embedded vanadium dioxide (VO2) films. The phase transition of VO2 films in 90° twisted E-shaped resonators enables high-efficiency thermal modulation of linear polarization conversion. The asymmetric transmission of linearly polarized wave and circular dichroism simultaneously exhibit a pronounced switching effect dictated by temperature-controlled conductivity of VO2 inclusions. The proposed hybrid metamaterial design opens exciting possibilities to achieve dynamic modulation of terahertz waves and further develop tunable terahertz polarization devices.

Optically controlled background-free terahertz switching in chiral metamaterial.

We demonstrate a multiband background-free terahertz (THz) switch in photoactive chiral metamaterial using polarization conversion. Orthogonal arrangement of two asymmetrical split-ring apertures allows a high polarization conversion efficiency and low copolarization transmission. The chiral metamaterial embedded with photoactive silicon promises a dynamic control on cross-polarization transmission and thus enables an efficient background-free THz switch. The on/off state of THz metamaterial switching can be efficiently controlled by an optical pump. The realization of a cross-polarization THz switch provides a new mechanism of mode switching to control THz wave propagation and will be a promising candidate for polarization devices.