Ultrastructural Studies of Nuclei and Nucleoli in Psoriatic Epidermis, Compared With Those in Normal Epidermis

Abstract

Quantitative and qualitative differences of the nuclear and nucleolar structures in normal and psoriatic (involved and uninvolved) epidermis were revealed with the electron microscope. The size of nuclei and nucleoli was increased, the frequency of nuclear bodies was increased, and the relative amount of heterochromatin was decreased in involved skin compared to normal or uninvolved skin. There was no significant difference between normal skin and uninvolved skin of psoriasis. In addition to these changes, multiple fibrillar centers within nucleoli and small masses of chromatin in the epidermal nucleoplasm were observed very frequently in involved skin, while rarely or not at all in normal and uninvolved skin. These results suggest that involved psoriatic keratinocytes have increased metabolic activity and abnormal protein synthesis, having undergone gene derepression.

Remodeling of Three-Dimensional Organization of the Nucleus during Terminal Keratinocyte Differentiation in the Epidermis

“…In particular, we show that nuclear volume is significantly decreased during epidermal keratinocyte differentiation ( Figure 1 ), which corresponds well to the data obtained from normal human epidermis demonstrating that size of the nucleus (determined on ultrathin sections) in keratinocytes of the granular layer is markedly lower compared to cells of the basal or spinous layers (Tsuji and Cox, 1977). …”

“…Our data obtained by using a multi-color confocal microscopy of cryosections of the normal mouse foot-pad epidermis, followed by computational image reconstruction and mathematical modelling are quite consistent with the results of two-dimensional ultra-structural studies of the nucleus in differentiating epidermal keratinocytes obtained previously (Breathnach, 1971; Karasek et al , 1972; Tsuji and Cox, 1977). In particular, we show that nuclear volume is significantly decreased during epidermal keratinocyte differentiation ( Figure 1 ), which corresponds well to the data obtained from normal human epidermis demonstrating that size of the nucleus (determined on ultrathin sections) in keratinocytes of the granular layer is markedly lower compared to cells of the basal or spinous layers (Tsuji and Cox, 1977).…”

“…Earlier studies demonstrated that keratinocyte transition between the distinct epidermal layers is accompanied by marked morphological and ultrastructural changes in the nucleus including its size, shape, structure of nucleoli, etc. (Breathnach, 1971; Karasek et al , 1972; Tsuji and Cox, 1977). Because spatial organization of the distinct genomic loci and nuclear bodies are critical for the proper regulation of gene expression (Dundr and Misteli, 2010; Schoenfelder et al , 2010), changes in the size and shape of the keratinocyte nucleus associated with terminal differentiation might, on the one hand, influence 3D-genome structure and gene expression programs in differentiating cells, and, on the other hand, reflect re-organization of these programs accompanied by the differentiation-associated accumulation or loss of the distinct cytoplasmic components, such as keratin 14, interacting with nuclear envelope and regulating nuclear shape (Lee et al, 2012).…”

Ultrastructural Findings and Tumor Necrosis Factor-alpha and Intercellular Adhesion Molecule-1 Expression in Psoriasis Patients Before and After Oral Cyclosporin A Therapy

“…A decrease in tonofilaments and keratohyalin granules and enlarged intercellular spaces are common findings in psoriatic skin [31,32]. The size of nuclei and nucleoli is increased and the relative amount of heterochromatin is decreased in psoriatic skin [20,33]. Ultrastructurally, it is difficult to distinguish keratinocytes in each layer of epidermis, except in the basal layer, because each psoriatic keratinocyte loses its polarity and the cells exhibit a similar shape [20].…”

Mitochondrial ring‐phenomenon of keratinocytes in psoriasis vulgaris after dithranol therapy

“…We know that intraeellular events may be subdivided into cytoplasmic and nuclear reactions, and that most ofthe quantitative reactions of stimulated cells can be largely attributed to the nucleolus 214 (10,11). Investigations of psoriatic epidermis have shown that in involved lesions both the nucleus and the nucleolus are significantly larger than in normal uninvolved epidermis (12). The observation of nucleolus-associated substance may be of interest in so far as similar nuclear structures have not been described in untreated psoriatie lesions, although an increased occurrence of nuclear bodies has been noted (13).…”