by 100J/cm2 is also significantly reduced by the application of sunscreen (Figure 2B). Immunostaining against Involucrin (Figure 2C) demonstrates a modest increase in the expression level only for the 100J/cm2 conditions and is ameliorated by the application of sunscreens. Altogether, these stains displayed a cohesive understanding that the skin barrier is compromised not only in the elevated UV dose (100J/cm2) but in some physiological UV conditions (20J/cm2) as well.
TEM Analysis of Ex Vivo Skin Following UV-Exposure
Figure 4 demonstrates TEM images captured to evaluate changes in tissue ultrastructure following UV irradiation. Figure 4A is able to illustrate the presence of intact corneodesmosomes (blue arrow), desmosomes (green arrow), lamellar bodies (red arrow), and keratohyalin granules (yellow arrow) in the stratum corneum and transition layer of untreated control tissue. Untreated tissue also has abundance of keratohyalin granules, an essential component of the keratinocyte cornification process, in the stratum granulosum layer. In agreement with histological and immunostaining analysis, TEM analysis illustrated limited disruption to tissue structure as a result of one-time irradiation at 20J/cm2 level (Figure 4B). When the tissue was exposed to a daily irradiation of 20J/cm2 over the course of 5 days, alterations to the keratin fibers and disruption to the adherens junctions can be observed. Keratinocytes in the stratum granulosum also became more apoptotic (Figure 4C). The UV irradiation effects on barrier disruption were amplified in the 100J/cm2 conditions, where the tissue displayed severe disruption to the adherens junctions, disassociation between cellular layers, and marked reduction of keratohyalin granules and lamellar bodies (Figure 4E). The benefits of photoprotection were observed through TEM images, where the application of sunscreen in the daily irradiation conditions showed better preservation of the adherens junctions and the keratohyalin granules (Figure 4D). At the high UV dose (100J/cm2), photoprotection applied prior to irradiation helped maintain tissue structure, although some regions still demonstrated disrupted corneodesmosomes and reduction of the keratohyalin granules (Figure 4E).
In this study, fresh ex vivo skin was utilized as a physiologically relevant model to understand the dynamic changes to skin barrier as a result of high-level UV irradiation. Our findings can be summarized by Figure 5, which illustrates that prolonged sun exposure significantly impacted the inside-out skin barrier, referring to cell junctions that prevent loss of water, electrolytes, and proteins, while being less potent in altering the outside-in barrier.27 Our study demonstrated a reduction in proteins that contribute to adherens junctions (Claudin 4 and
TEM Analysis of Ex Vivo Skin Following UV-Exposure
Figure 4 demonstrates TEM images captured to evaluate changes in tissue ultrastructure following UV irradiation. Figure 4A is able to illustrate the presence of intact corneodesmosomes (blue arrow), desmosomes (green arrow), lamellar bodies (red arrow), and keratohyalin granules (yellow arrow) in the stratum corneum and transition layer of untreated control tissue. Untreated tissue also has abundance of keratohyalin granules, an essential component of the keratinocyte cornification process, in the stratum granulosum layer. In agreement with histological and immunostaining analysis, TEM analysis illustrated limited disruption to tissue structure as a result of one-time irradiation at 20J/cm2 level (Figure 4B). When the tissue was exposed to a daily irradiation of 20J/cm2 over the course of 5 days, alterations to the keratin fibers and disruption to the adherens junctions can be observed. Keratinocytes in the stratum granulosum also became more apoptotic (Figure 4C). The UV irradiation effects on barrier disruption were amplified in the 100J/cm2 conditions, where the tissue displayed severe disruption to the adherens junctions, disassociation between cellular layers, and marked reduction of keratohyalin granules and lamellar bodies (Figure 4E). The benefits of photoprotection were observed through TEM images, where the application of sunscreen in the daily irradiation conditions showed better preservation of the adherens junctions and the keratohyalin granules (Figure 4D). At the high UV dose (100J/cm2), photoprotection applied prior to irradiation helped maintain tissue structure, although some regions still demonstrated disrupted corneodesmosomes and reduction of the keratohyalin granules (Figure 4E).
In this study, fresh ex vivo skin was utilized as a physiologically relevant model to understand the dynamic changes to skin barrier as a result of high-level UV irradiation. Our findings can be summarized by Figure 5, which illustrates that prolonged sun exposure significantly impacted the inside-out skin barrier, referring to cell junctions that prevent loss of water, electrolytes, and proteins, while being less potent in altering the outside-in barrier.27 Our study demonstrated a reduction in proteins that contribute to adherens junctions (Claudin 4 and
