Dead but Highly Dynamic – The Stratum corneum Is Divided into Three Hydration Zones

Abstract

Topically applied water exerts mechanical stress on individual corneocytes as well as on the whole stratum corneum (SC), resulting in an alteration of barrier function. In this study we used complete skin biopsies and showed that the SC reacts to water stress as a highly optimized and well-regulated structure against osmotic changes. Following a relatively new cryo-processing protocol for cryo-SEM, it is possible to reliably maintain and investigate the hydrated state of the SC and individual corneocytes after treatment with solutions of different ionic strength. Treatment with distilled water results in swelling of SC cells together with formation of massive water inclusions between adjacent cell layers. Treatment with 5–20% NaCl reveals three different hydration zones within the SC: Corneocytes near the live-dead transition zone can swell to nearly double their thickness. The second zone is the most compact, as the corneocytes here show the smallest thickness variation with all treatments. Within the outermost zone, again a massive swelling and loosening of intracellular filament packing can be observed. We therefore conclude that the SC itself is subdivided into three functional zones with individual water penetration and binding potentials. Since the second zone remains nearly unaffected by water stress, we propose that this zone hosts the functional SC barrier.

Noninvasive Determination of Epidermal and Stratum Corneum Thickness in vivo Using Two-Photon Microscopy and Optical Coherence Tomography: Impact of Body Area, Age, and Gender

“…The average thickness of the stratum corneum (SC) ranges from 10 to 30 µm [1-3]. The SC, being the outermost cell layer, has direct contact to the environment and therefore a special role.…”

“…It functions as a protective barrier against extrinsic influences such as ultraviolet (UV) radiation, dehydration, and penetration. In addition, it offers the opportunity to observe the occurrences of hyperkeratosis as well as the healing processes of wounds [3, 4]. Furthermore, the quantification of the epidermal thickness (ET) is of great importance, in order to be able to evaluate the influential factors upon the protective function of the skin [5, 6].…”

“…OCT can be employed as a comparative reference to 2PM and can verify the quality and applicability of 2PM [4, 19]. The depiction of the SC and the exact determination of its thickness has not been possible up to now, either invasively or noninvasively [3, 17]. Quantification by OCT may be possible only at the palm and plantar and with hyperkeratotic skin (SC > 50 µm) [4, 6].…”

Application of the critical angle method to refractive index measurement of human skinin vivounder partial contact

“…[6][7][8][9][10][11][12] In the case of in vivo measurements of skin, the measurement depth is important because the amount of water varies dramatically with depth, and it generates a gradient in the RI with depth. 13,14 In evaluating the behavior of light at the air-skin interface, the latter class of measurements is more appropriate since those measurements are considered to be sensitive to the ratio of surface reflection to interior reflection. 1,2,15 The ultimate goal of our research is to measure in vivo the RI of a superficial area of a cornified layer.…”

Improved Native Tissue Ultrastructure Investigations by High Pressure Freezing and Cryo-SEM

“…protein patterns of membrane fracture faces, arrangement and dimensions of organelles and membranes in cross-fractured areas. The high throughput of this method [2] is ideally bridging the gab between CLSM and TEM investigations in space and in time.…”