Lamellar granules (LGs), which are fused to the cellular membrane and release their contents to intracellular spaces, are thought to play crucial roles in the skin barrier formation and desquamation. Although LGs have been observed as oval-shaped vesicles or vesicular tubular structures on electron micrographs, the overall structures of LGs in the epidermis are unclear due to the technical limitations of the previously applied microscopy techniques. In this study, we aimed to elucidate how the structures of LGs change in normal human skin by using focused ion beam scanning microscopy (FIB-SEM). The 3D images showed that LGs fused with the cellular membrane in the most superficial granular layer. LGs in the second granular layer was not only localized in the cytoplasm but also secreted into the intercellular space and structure of LGs was reticular at the cell surface. In contrast, within the SG3 layer, LGs resided in the cytoplasm as vesicles. Furthermore, the trans-Golgi network which was well developed, spread into the cytoplasm with branched tubular structures and connected to LGs.
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