Melanocytes are surrounded by diverse cells, including sensory neurons in our skin, but their interaction and functional importance have been poorly investigated. In this study, we find that melanocytes and nociceptive neurons contact more in human skin color patch tissue than control. Co-culture with human iPSC-derived sensory neurons significantly induces morphogenesis and pigmentation of human melanocytes. To reveal melanocyte-stimulating factors secreted from neurons, we perform proteomic analyses and identify RGMB in the sensory neuron-conditioned medium. RGMB protein induces morphogenesis and melanin production of melanocytes, demonstrating that RGMB is a melanocyte-stimulating factor released from sensory neurons. Transcriptome analysis suggests that the melanosome transport machinery can be controlled by RGMB, leading us to identify the vesicle production response of melanocytes upon RGMB treatment. This study discovers a role of sensory neurons in modulating multiple aspects of human melanocytes through secretion of a key factor: RGMB.
Effects of molecular weight and end-group functionality on spreading of molecularly thin perfluoropolyether (PFPE) film over solid surfaces with groove-shaped textures have been studied by experiments and Monte Carlo simulations. In the experiments, lubricant spreading on a surface with groove-shaped textures was measured by making use of the phenomenon in which diffracted light weakens in the lubricant-covered region. It is found that grooves serve to accelerate spreading and this effect increases for deeper grooves, and also the accelerating rate becomes larger for a lubricant having a larger molecular weight or functional end-groups. In the simulations, the Monte Carlo method based on the Ising model was extended to enable us to evaluate the effect of molecular weight on the spreading of non-functional lubricant inside a groove. The validity of the newly developed simulation method was well confirmed from the agreement between the simulation and experimental results.
Characteristics of molecularly thin lubricant films are basically determined by their interactions with solid surfaces. Since these interactions can be modified by engineered microscopic surface textures, it is expected that rational design of the textures will make it possible to attain desired tribological functions and performance. In this research, with the aim of applying it to head-disk interface of hard disk drives, we propose a method based on diffraction simulations that enables thickness measurement of molecularly thin films coated on grooved solid surfaces. Using this method, we experimentally investigate the spreading characteristics of nanometer-thick polymeric liquid lubricant films on grooved surfaces. The results revealed that the average thicknesses of the films dip-coated on the grooved and smooth surfaces under identical conditions were approximately the same, whereas lubricant spreading on grooved surfaces was significantly faster than that on smooth surfaces.
Spreading characteristics of molecularly thin lubricant on a grooved surface have been studied numerically by Monte Carlo simulations and compared with measurements obtained by perfluoropolyether (PFPE) thin film spreading on a solid surface with minute grooves. In the simulations, by incorporating the interactions between molecules and the side surfaces of a groove, the Monte Carlo method based on the Ising model was extended to the case of a surface with grooves and applied to simulate the spreading of non-polar lubricant inside a groove. Compared with the spreading on a smooth surface, lubricant spreads rapidly inside a groove, indicating an acceleration of the spreading along the groove. In the experiments, lubricant spreading on surfaces with groove-shaped textures was measured by making use of the phenomenon in which diffracted light vanishes in the lubricant-covered region. Based on the results showing lubricant spreading predominantly along the groove, the accelerating effect obtained in the simulations is well confirmed by the measurements.
A method which enables measurement of thickness of a molecularly thin lubricant film coated on a surface with groove-shaped textures is presented. In this method, zero-order diffracted light is first calculated versus the film thickness by using rigorous coupled-wave analysis, and then parameters measured by an ellipsometer are converted to film thickness by using the calculated result. Lubricant spreading is experimentally measured on a grooved surface with this method. Compared with that on a smooth surface, lubricant spreading is faster on the grooved surface, indicating an acceleration effect of the grooves.
Spreading characteristics of molecularly thin lubricant over grooved surface has been studied numerically by Monte Carlo simulations and compared with measurements obtained by perfluoropolyether (PFPE) thin film spreading over a solid surface with minute grooves. In the simulations, by incorporating the interactions between molecule and side surfaces of a groove, the Monte Carlo method based on the Ising model was extended to the case of surface with grooves and applied to simulation for the spreading of non-polar lubricant inside a groove. Compared with the spreading on a smooth surface, lubricant spreads rapidly inside the groove, indicating an acceleration of the spreading along the groove. In the experiments, lubricant spreading on surface with groove-shaped texture was measured by making use of the extinction of diffraction light on the lubricant-covered region. From the results that lubricant spread predominantly along the groove, the accelerating effect obtained in the simulations is well confirmed by the measurements.
Spreading characteristics of molecularly thin lubricant on a grooved surface have been studied numerically by Monte Carlo simulations and compared with measurements obtained by perfluoropolyether (PFPE) thin film spreading on a solid surface with minute grooves. In the simulations, by incorporating the interactions between molecules and the side surfaces of a groove, the Monte Carlo method based on the Ising model was extended to the case of a surface with grooves and applied to simulate the spreading of non-polar lubricant inside a groove. Compared with the spreading on a smooth surface, lubricant spreads rapidly inside a groove, indicating an acceleration of the spreading along the groove. In the experiments, lubricant spreading on a surface with groove-shaped textures was measured by making use of the phenomenon in which diffracted light decreases or vanishes in the lubricant-covered region. Based on the results showing lubricant spreading predominantly along the groove, the accelerating effect obtained in the simulations is well confirmed by the measurements.
