Cyclosporine A stimulated hair growth from mouse vibrissae follicles in an organ culture model

Hypertrichosis is one of the most common side effects of systemic cyclosporine A therapy.It has been previously shown that cyclosporine A induces anagen and inhibits catagen development in mice.In the present study,to explore the mechanisms of cyclosporine A,we investigated the effects of cyclosporine A on hair shaft elongation,hair follicle cell proliferation,apoptosis,and mRNA expression of selected growth factors using an organ culture model of mouse vibrissae.In this model,cyclosporine A stimulated hair growth of normal mouse vibrissae follicles by inhibiting catagen-like development and promoting matrix cell proliferation.In addition,cyclosporine A caused an increase in the expression of vascular endothelial growth factor（VEGF）,hepatocyte growth factor（HGF）,and nerve growth factor（NGF）,and inhibited follistatin expression.Our findings provide an explanation for the clinically observed effects of cyclosporine A on hair growth.The mouse vibrissae organ culture offers an attractive model for identifying factors involved in the modulation of hair growth.

Relationship between structure and function of mammalian vibrissa

The Structure of mammalian vibrissa was observed microscopically and the relationship of morphologyand function was discussed. The vibrissa is conical. The elasticity and tenacity of vibrissa are stronger than that ofpelage hair. The scales are shaped irregular on vibrissa shaft except for the root part, because of tractional damages. This type of scales is of great importance in preventing the vibrissa from being totally destroyed. Cortex ofvibrissa is observed very well developed, thus its elasticity and tenacity work well in touching and sensing. Medullaof vibrissa is not well developed because vibrissa has been evaluated to fail in warm-keeping function.

Dynamic Behavior Induced by the Cooperation between Two Different Ionic Conductances in a Mathematical Model of Vibrissa Motoneurons

A mathematical model of vibrissa motoneurons (vMN), which has been developed by Harish and Golomb, can show repetitive spiking in response to a transient external stimulation. The vMN model is described by a system of nonlinear ordinary differential equations based on the Hodgkin-Huxley scheme. The vMN model is regulated by various types of ionic conductances, such as persistent sodium, transient sodium, delayed-rectifier potassium, and slow ionic conductances (e.g., slowly activating potassium afterhyperpolarization (AHP) conductance and h conductance). In the present study, a numerical simulation analysis of the vMN model was performed to investigate the effect of variations in the transient sodium and the slow ionic conductance values on the response of the vMN model to a transient external stimulation. Numerical simulations revealed that when both the transient sodium and the AHP conductances are eliminated, the vMN model shows a bistable behavior (i.e., a stimulation-triggered transition between dynamic states). In contrast, none of the following induce the transition alone: 1) elimination of the transient sodium conductance;2) elimination of the AHP conductance;3) elimination of the h conductance;or 4) elimination of both the transient sodium and the h conductances.

Analysis of the Vibrissa Parametric Resonance Causing a Signal Amplification during Whisking Behaviour

The paper deals with the mechanical vibrational motion ofvibrissae during natural exploratory behaviour of mammals. The theoretical analysis is based on a mechanical model of a cylindrical beam with circular natural configuration under an applied periodic force at the tip, which corresponds to the surface roughness of an investigated object. The equation of motion of the beam is studied using the Euler-Bemoulli beam theory and asymptotic methods of mechanics. It is shown that from the me- chanical point of view the phenomenon of parametric resonance of the vibrissa is possible. It means that the amplitude of forced vibrations of a vibrissa increases exponentially with time, if it is stimulated within a specific resonance frequency range, which depends on biomechanical parameters of the vibrissa. The most intense parametric resonance occurs, when the excitation frequency is close to the doubled natural frequency of free vibrations. Thus, it may be used to distinguish and amplify specific periodic components of a complex roughness profile during texture discrimination.