PubMed · 2474732
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K Hancock, M E Hackett. 1989-08-19. Skin equivalents.. https://doi.org/10.1016/s0140-6736(89)90608-9
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The outermost region of the epidermis, the stratum corneum (SC), provides an essential barrier to water loss and protects against exogenous substances. The functional integrity of the SC depends on a complex maturation and exfoliation process, which is often perturbed in skin diseases. The maturation of corneocytes isolated from different depths in healthy human SC was investigated using infrared (IR) spectroscopic imaging and Raman microscopy. Both IR and Raman spectral quality of individual corneocytes was high and revealed depth-dependent variations in molecular composition. Spectral changes were identified as arising from alterations in the concentration of the major constituents of natural moisturizing factor (NMF), important in maintaining SC hydration. A significant decrease in the concentration of NMF was observed for corneocytes isolated from superficial compared to deeper SC layers (layer 3 vs. layer 11, respectively). An IR parameter that measures the relative NMF concentration in corneocytes is introduced. The potential role of vibrational imaging to evaluate corneocyte composition and molecular structure in the treatment of NMF-related diseases is discussed.
Nestin, a member of the sixth class of intermediate filament proteins, has long been known not only as a specific marker for central nervous system stem cells, but also as an indicator of the degree of neural stem cell differentiation. Immunohistochemical analysis showed nestin expression in the epidermis and the upper two-third of the hair follicle in non-balding human scalp skin, but not in the lower third of the follicle. Expression was very weak in the sebaceous gland. The level of nestin mRNA transcription was much higher in the bulge region of the follicle than in the sebaceous gland. These results show that the pattern of nestin expression is related to the differentiation of epidermal stem cells.
By means of flow cytometry, we demonstrate that a subpopulation of cells in the basal layer of the human epidermis has undetectable levels of major histocompatibility complex (MHC) class I molecule. The percentage of MHC class I-negative cells in the basal layer ranged 0.5%-2%. MHC class I-negative cells were characterized by small size (low forward scatter) and low granularity (low side scatter). Upon culturing of MHC class I-negative cells, increase of MHC class I expression was observed. This expression was lower than the expression of MHC class I molecule both in cultured MHC class I-positive cells and in ex vivo keratinocytes. Furthermore, stimulation of MHC class I-negative keratinocytes with interferon gamma (IFN-gamma) did not bring about further increase in MHC class I expression. MHC class I-negative cells were identified as keratinocytes as they expressed keratin 14 and formed keratinocyte colonies in vitro.