Patterns and associations of structural and functional cutaneous responses during loading at heel and sacral skin in aged females: A reanalysis of clinical study data.

AIM OF THE STUDY: The aim of this study was to explore possible interrelationships and cutaneous response patterns at the heel and sacral skin due to prolonged loading. MATERIALS AND METHODS: Skin stiffness, elasticity, roughness and transepidermal water loss, stratum corneum hydration, erythema, and temperature of n = 20 aged females (mean age 69.9 years) were measured before and after 90 and 150 min loading in supine position. Delta values were calculated and correlated using Spearman's rho. Strengths and directions of associations and similar patterns were subsequently identified for the heel and sacrum areas. RESULTS: At the sacral area decreased stiffness (Uf) was associated with increased TEWL and there was a positive relationship between mean roughness (Rz) and erythema. At the heel there was a positive association between TEWL and decreasing stiffness (Uf). CONCLUSIONS: Our results indicate a dynamic interaction between skin changes during loading and different physiological response patterns for sacral and heel skin. There seems to be close association between transepidermal water loss and stiffness changes during loading.

Physiological and Molecular Effects of in vivo and ex vivo Mild Skin Barrier Disruption.

The success of topically applied treatments on skin relies on the efficacy of skin penetration. In order to increase particle or product penetration, mild skin barrier disruption methods can be used. We previously described cyanoacrylate skin surface stripping as an efficient method to open hair follicles, enhance particle penetration, and activate Langerhans cells. We conducted ex vivo and in vivo measurements on human skin to characterize the biological effect and quantify barrier disruption-related inflammation on a molecular level. Despite the known immunostimulatory effects, this barrier disruption and hair follicle opening method was well accepted and did not result in lasting changes of skin physiological parameters, cytokine production, or clinical side effects. Only in ex vivo human skin did we find a discrete increase in IP-10, TGF-ß, IL-8, and GM-CSF mRNA. The data underline the safety profile of this method and demonstrate that the procedure per se does not cause substantial inflammation or skin damage, which is also of interest when applied to non-invasive sampling of biomarkers in clinical trials.

Adaptive microfluidic gradient generator for quantitative chemotaxis experiments.

Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell.

Infundibular protein and RNA microarray analyses from affected and clinically non-affected scalp in male androgenetic alopecia patients.

Non-invasive sample collection methods could facilitate clinical research on hair diseases. In an exploratory experimental study on six male volunteers with untreated androgenetic alopecia (AGA), Hamilton-Norwood stage IIIv-IV, skin surface and infundibular protein as well as RNA extracts from plucked hair follicles were analyzed from frontal skin, vertex and clinically unaffected occiput. Slightly increased levels of inflammatory markers were only found in AGA-affected scalp skin and infundibulum, not in RNA from plucked hair follicles. RNA expression profiles point towards differential expression of genes involved in hair cycle regulation, hair keratin production, but also RNA methylation and ion channel regulation.

Intracellular photoactivation of caged cGMP induces myosin II and actin responses in motile cells.

Cyclic GMP (cGMP) is a ubiquitous second messenger in eukaryotic cells. It is assumed to regulate the association of myosin II with the cytoskeleton of motile cells. When cells of the social amoeba Dictyostelium discoideum are exposed to chemoattractants or to increased osmotic stress, intracellular cGMP levels rise, preceding the accumulation of myosin II in the cell cortex. To directly investigate the impact of intracellular cGMP on cytoskeletal dynamics in a living cell, we released cGMP inside the cell by laser-induced photo-cleavage of a caged precursor. With this approach, we could directly show in a live cell experiment that an increase in intracellular cGMP indeed induces myosin II to accumulate in the cortex. Unexpectedly, we observed for the first time that also the amount of filamentous actin in the cell cortex increases upon a rise in the cGMP concentration, independently of cAMP receptor activation and signaling. We discuss our results in the light of recent work on the cGMP signaling pathway and suggest possible links between cGMP signaling and the actin system.

Impact of the carbazole derivative wiskostatin on mechanical stability and dynamics of motile cells.

Many essential functions in eukaryotic cells like phagocytosis, division, and motility rely on the dynamical properties of the actin cytoskeleton. A central player in the actin system is the Arp2/3 complex. Its activity is controlled by members of the WASP (Wiskott-Aldrich syndrome protein) family. In this work, we investigated the effect of the carbazole derivative wiskostatin, a recently identified N-WASP inhibitor, on actin-driven processes in motile cells of the social ameba Dictyostelium discoideum. Drug-treated cells exhibited an altered morphology and strongly reduced pseudopod formation. However, TIRF microscopy images revealed that the overall cortical network structure remained intact. We probed the mechanical stability of wiskostatin-treated cells using a microfluidic device. While the total amount of F-actin in the cells remained constant, their stiffness was strongly reduced. Furthermore, wiskostatin treatment enhanced the resistance to fluid shear stress, while spontaneous motility as well as chemotactic motion in gradients of cAMP were reduced. Our results suggest that wiskostatin affects the mechanical integrity of the actin cortex so that its rigidity is reduced and actin-driven force generation is impaired.