Phenotypic Plasticity of Mouse Spermatogonial Stem Cells

BACKGROUND:Spermatogonial stem cells (SSCs) continuously undergo self-renewal division to support spermatogenesis. SSCs are thought to have a fixed phenotype, and development of a germ cell transplantation technique facilitated their characterization and prospective isolation in a deterministic manner; however, our in vitro SSC culture experiments indicated heterogeneity of cultured cells and suggested that they might not follow deterministic fate commitment in vitro. METHODOLOGY AND PRINCIPAL FINDINGS:In this study, we report phenotypic plasticity of SSCs. Although c-kit tyrosine kinase receptor (Kit) is not expressed in SSCs in vivo, it was upregulated when SSCs were cultured on laminin in vitro. Both Kit(-) and Kit(+) cells in culture showed comparable levels of SSC activity after germ cell transplantation. Unlike differentiating spermatogonia that depend on Kit for survival and proliferation, Kit expressed on SSCs did not play any role in SSC self-renewal. Moreover, Kit expression on SSCs changed dynamically once proliferation began after germ cell transplantation in vivo. CONCLUSIONS/SIGNIFICANCE:These results indicate that SSCs can change their phenotype according to their microenvironment and stochastically express Kit. Our results also suggest that activated and non-activated SSCs show distinct phenotypes

The effects of dipeptidyl peptidase-4 on cardiac fibrosis in pressure overload-induced heart failure

Dipeptidyl peptidase-4 (DPP-4) inhibitors are hypoglycemic agents. DPP-4 inhibitor has cardioprotective effects after transverse aortic constriction (TAC), but role of DPP-4 on cardiac fibrosis after TAC is not well known. Our aim was to determine the effects of DPP-4 on cardiac fibrosis in murine TAC model. Wild-type mice and DPP-4 knockout mice were subjected to TAC. Wild-type mice were then treated with vehicle or DPP-4 inhibitor. DPP-4 activities in serum and heart tissue were significantly increased at 2 weeks after TAC, but they were significantly decreased by DPP-4 inhibitor treatment. The inhibition of DPP-4 did not affect left ventricular hypertrophy, but improved cardiac function and decreased myocardial and perivascular fibrosis after TAC. The inhibition of DPP-4 decreased the collagen type III/I ratio in myocardium. These results suggest that DPP-4 inhibition ameliorates the progression of heart failure after TAC by changing the quality and quantity of cardiac fibrosis

Terahertz wave emission from plasmonic chiral metasurfaces

Plasmonic chiral metasurfaces with pinwheel-like structures are fabricated on silver films using a focused ion-beam milling technique. In time-domain spectroscopy, we observe terahertz (THz) wave emission from metasurfaces irradiated by a near-infrared Ti:sapphire ultrashort pulsed laser. The origin of the THz wave generation is likely to be tunnelling ionization accompanied with photoelectron acceleration by ponderomotive force. Numerical simulation is carried out toward improvement of the chiral metasurfaces for better emission of circularly polarized THz waves

DPP-4 inhibition protects human umbilical vein endothelial cells from hypoxia-induced vascular barrier impairment

Dipeptidyl peptidase-4 (DPP-4) inhibitors are relatively new class of anti-diabetic drugs. Some protective effects of DPP-4 on cardiovascular disease have been described independently from glucose-lowering effect. However, the detailed mechanisms by which DPP-4 inhibitors exert on endothelial cells remain elusive. The purpose of this research was to determine the effects of DPP-4 inhibitor on endothelial barrier function. Human umbilical vein endothelial cells (HUVECs) were cultured and exposed to hypoxia in the presence or absence of Diprotin A, a DPP-4 inhibitor. Immunocytochemistry of vascular endothelial (VE-) cadherin showed that jagged VE-cadherin staining pattern induced by hypoxia was restored by treatment with Diprotin A. The increased level of cleaved β-catenin in response to hypoxia was significantly attenuated by Diprotin A, suggesting that DPP-4 inhibition protects endothelial adherens junctions from hypoxia. Subsequently, we found that Diprotin A inhibited hypoxia-induced translocation of NF-κB from cytoplasm to nucleus through decreasing TNF-α expression level. Furthermore, the tube formation assay showed that Diprotin A significantly restored hypoxia-induced decrease in number of tubes by HUVECs. These results suggest that DPP-4 inhibitior protects HUVECs from hypoxia-induced barrier impairment