SCANNING ELECTRON MICROSCOPY OF THE STRATUM CORNEUM

Summary.— This report describes studies of stratum corneum from normal subjects and from patients with various scaly disorders, with the scanning electron microscope, using the skin surface biopsy technique.
Normnal squamous cells showed essentially the same structure in different parts of the body; individual squames demonstrated irregular surface folds, convolutions and occasionally a more villous appearance. In dominant ichthyosis vulgaris the squamous cells showed predominantly an irregular fine nodular surface pattern. Similar changes were found in non-bullous ichthyosiform erythroderma. Surface depressions (maxitnum diameter approximately 300 nm) were occasionally seen on squames from bullous ichthyosiform erythroderma. Psoriatic squamous cells showed a more pronounced villous pattern than normal squames, the villi being evenly distributed over the surface of the majority of cells examined; some cells had rather flattened villi near their edges.
Possible physiological roles for the structural changes found are discussed.     

EPIDERMAL CELL REPLACEMENT: TOPOGRAPHICAL VARIATIONS IN ALBINO GUINEA-PIG SKIN

SUMMARY.— The thickness of ear epidermis in normal albino guinea-pigs is 60% higher than that of back epidermis. The proliferative activity measured by DNA-synthesizing cells is equal in both body regions. Cytokinetic analysis of the upward movement of ³H-Thymidine-labelled cells revealed a transit time of about 8 days on the back and about 14 days on the ear. It is concluded that cell differentiation proceeds much more slowly in ear epidermis thus bringing about the increase in the cell population. No difference was found between systemic and intradermal injection of ³H-Thymidine.     

Epidermis reconstructed from the outer root sheath of human hair follicle. Effect of retinoic acid

In the present paper, we show that a multilayered and well-differentiated epidermis can easily and rapidly be generated in vitro from the outer root sheath of human hair follicles deposited on de-epidermized demis. Histologically, this epidermis presented characteristic features of normal human epidermis in vivo. Moreover, markers specific for interfollicular keratinocyte terminal differentiation, such as the K10 keratin, involucrin, membrane-bound transglutaminase, filaggrin and loricrin, were expressed in the reconstructed tissue. By in situ hybridization, keratin K5 and K10 mRNAs were detected in the basal and suprabasal cells, respectively, as in normal human epidermis. The differentiation pattern achieved in this reconstructed epidermis confirms the already reported phenotypical shift from outer root sheath cells to interfollicular keratinocytes and shows that this transition takes place in the absence of living fibroblasts. The differentiation of the reconstructed epidermis thus obtained was modulated by retinoic acid in a dose-dependent manner. This culture system on dead dermis is easier to handle than similar cultures on collagen-fibroblast lattices because of the resistance of dermis to mechanical forces and to collagenolysis. It could represent a valuable wound-healing model and a promising tool for pharmacological studies on in vitro reconstructed skin.     

A histochemical profile of lichen simplex

Enzyme histochemical tests were performed on biopsies taken from patches of lichen simplex in eighteen patients and the results were contrasted with previous findings in psoriasis and lichen planus. The mitochondria! enzyme reactions were found to be increased within the epidermis, differing from those in lichen planus, in which there is a decreased density of reaction product for these tests. The non-specific esterase band was increased in width in lichen simplex contrasting with the absence of a discrete band in psoriasis. The DOPA reaction demonstrated the presence of positively reacting cells in the basal layer, and the ATPase reaction showed that there were many ATPase positive dendritic cells within the epidermis. It appears that in lichen simplex there is hyperplasia of all components of the epidermis in contrast to psoriasis where it seems the hyperplasia is almost restricted to keratinocytes.     

Tumor promotion by regenerative epidermal hyperplasia in mouse skin

Chemically induced epidermal carcinogenesis is usually divided into two stages: initiation, which involves the conversion of epidermal cells into latent neoplastic cells; and promotion, which allows the expression of this neoplastic change. One of the characteristics of promotion is the transformation of the normal epidermis into a hyperplastic epidermis.
One of the unanswered questions about epidermal tumor promotion is whether the epidermal hyperplasia that characterizes promoted skin is simply a regenerative epidermal hyperplasia resulting from damage produced by the promoter. The opinion currently held is that the epidermal hyperplasia produced by tumor promoters is not simply a regenerative epidermal hyperplasia and possesses characteristics which a regenerative hyperplasia does not have, enabling it to evolve into an epidermal neoplasm.
The purpose of this review is to present recent evidence which strongly suggests that promoter induced hyperplasia is a regenerative hyperplasia. Two principal lines of evidence arc reviewed. The first demonstrates that an epidermal regenerative hyperplasia repeatedly produced by wounding or abrasion can promote epidermal carcinogenesis in the initiated skin of mice. The second line of evidence demonstrates that the epidermal hyperplasia produced by the application of 12-O-tetradccanoyl-phorbol-13-acetate (TPA), the most powerful and widely used promoter of skin carcinogenesis, is preceded by damage to the epidermis. This strongly suggests that the epidermal hyperplasia which ensues is a regenerative hyperplasia.
The review concludes that during epidermal tumor promotion there is a chronic regenerative epidermal hyperplasia, and that there is no evidence for any other necessary factors during tumor promotion in appropriately initiated mouse skin.     

Mitotic rates of rat epidermis. During growth, maturity, senility, and regeneration.

Adult epidermal tissues are renewing cell populations. Mitosis continuously provides new cells replacing those that became keratinized and ultimately shed. It seems plausible to assume that in the epidermis of growing individuals mitosis supplies cells both for cell addition (growth) and renewal. During growth, more cells are presumably retained in the tissue than become lost through desquamation. It is feasible by cutaneous incision to temporarily revert adult epidermis into a growing cell population. Presumably also during healing, cell production exceeds cell loss. What is the magnitude of cell production for renewal of adult epidermis, for simultaneous cell addition and renewal during growth, as well as during epidermal regeneration? To elucidate these problems, the mitotic rates of three epidermal cell populations (ear, plantar, and abdominal epidermis) were determined in the growing, adult, and senile rat. Further, the adult ear and back skin epidermis was converted by cutaneous incision into regenerating cell populations, and the mitotic rates were determined during healing at intervals from six hours to nine days.     

Two patterns of solar lentigines: A histopathological analysis of 40 Japanese women

Solar lentigines are common acquired pigmented lesions on sun-exposed skin. Their histopathological features have been reported as large numbers of melanocytes at the base of clubbed and budding rete ridges. In this study, biopsies were taken from facial solar lentigines in 40 Japanese women, and the sections were stained using hematoxylin-eosin, Fontana-Masson, and immunostained for melanocytes and Langerhans cells in order to verify the histological patterns of Japanese patients. We characterized the histopathological features of solar lentigines on the face and identified two patterns: one pattern (20/40 cases) demonstrated a flattened epidermis with basal melanosis, and the other pattern (20/40 cases) showed epidermal hyperplasia with elongated rete ridges composed of deeply pigmented basaloid cells. We termed the former pattern the "flattened epidermis" group, and the latter the "budding" group, respectively. The flattened epidermis group showed a significantly thinner epidermis, more severe solar elastosis and fewer Langerhans cells in the epidermis as compared with the budding group. We concluded that more severely sun-damaged solar lentigines might show the changes observed in the flattened epidermis group. Langerhans cells in the epidermis of solar lentigines might play a role in the remission of postinflammatory pigmentation due to aesthetic treatment.     

Elemental changes in guinea pig epidermis at repeated exposure to sodium lauryl sulfate.

Epidermal hyperplasia is the response of the epidermis to external harmful stimuli. The control and regulation of this hyperplasia is not completely understood. It has been proposed that changes in the cellular sodium/potassium ratio are of importance in the regulation of cell proliferation. To evaluate if such a change in the elemental content of epidermal cells can be one factor to consider at irritant contact dermatitis, we performed a quantitative assessment of sodium lauryl sulfate (SLS)-induced contact reactions in the guinea pig. SLS was applied 1, 2 or 3 times and biopsies were obtained at 24 and 84 h after the last application. It was found that repeated exposures to SLS induced a hyperplasia of epidermis at 24 h persisting at 84 h. At 24 h there were significant changes in the sodium and potassium content of the keratinocytes. At 84 h there was still an increased potassium level in the cells and the sodium/potassium ratio was significantly decreased in epidermis exposed three times to SLS. This implies that changes in cellular sodium/potassium ratios occur in epidermal hyperplasia following irritant stimuli.     

Selective suppression of two postnatally acquired 70 kD and 65 kD keratin proteins during continuous treatment of adult mouse tail epidermis with vitamin A

Using mouse tail epidermis as a model system we have studied the morphologic and biochemical effects of continuous topical treatment with vitamin A acid. Normal tail epidermis shows a regular pattern of parakeratotic scale regions and orthokeratotic interscale regions which arise postnatally from a uniformly orthokeratinizing neonatal epidermis. Daily treatment of tail epidermis with vitamin A acid for 14 days results in the induction of hyperplasia and the orthokeratotic conversion of the scale regions. The degree of these alterations is dose-dependent and maximally brought about by repetitive 30-microgram doses of the vitamin. To correlate morphologic with biochemical alterations, we have analyzed the keratin patterns of normal and vitamin A acid-treated epidermis by one- and two-dimensional gel electrophoresis. The results indicate that repetitive vitamin A treatment leads to the selective suppression of two postnatally acquired 70 kD and 65 kD type II keratin proteins. Again the minimum repetitive dose required for their complete suppression is 30 micrograms vitamin A acid. Kinetic studies reveal an initial lag phase of 6 days of apparent nonresponsiveness, followed by a 5-day period during which the adult pattern is gradually replaced by the neonatal pattern. Repetitive treatment of tail epidermis with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate leads to a strong hyperplasia; however, it strictly maintains the scale parakeratosis. Under these conditions only the 70 kD keratin subunit is suppressed. This indicates that the suppression of the 70 kD keratin is generally linked to the induction of hyperproliferation, whereas the suppression of the scale-associated 65 kD subunit is due to the metaplastic potency of vitamin A. We provide evidence that this vitamin A-specific in vivo effect can be used to determine the biologic activity of synthetic retinoids relative to vitamin A acid.     

c—Ha—ras原癌基因与银屑病

ｒａｓ癌基因与角朊细胞增殖、分化密切相关。本研究旨在利用斑点杂交和原位杂交法研究ｃ－Ｈａ－ｒａｓ癌基因在正常皮肤及进行期斑块型银屑病皮损中的表达，从癌基因角度初步探讨银屑病的发病机理。结果：①斑点杂交表明ｃ－Ｈａ－ｒａｓｍＲＮＡ在进行期斑块型银屑病皮损中含量较正常皮肤增加１倍；②ｃ－Ｈａ－ｒａｓ癌基因在正常皮肤表皮主要表达于部分基底层细胞，而在进行期银屑病皮损内则可见于除角质层外其余各层表皮细胞，且以棘层细胞为主。ｃ－Ｈａ－ｒａｓ癌基因在表皮细胞的过度表达及表达部位的改变可能是银屑病表皮过度增生和异常分化的重要机理。     

Appearance of Langerhans cells in the epidermis of Tgfb1(-/-) SCID mice: paracrine and autocrine effects of transforming growth factor-beta 1 and -beta 2(1)

A striking immunologic abnormality of normal and SCID Tgfb1(-/-) mice is the total absence of Langerhans cells in their epidermis. Here we show that transfer of Tgfb1(+/-) SCID bone marrow causes, within a few weeks, the appearance of Langerhans cells in the epidermis of gamma-irradiated and unirradiated Tgfb1(-/-) SCID recipients. In addition, local injection of 2 x 10(5) latent transforming growth factor-beta1 cDNA-transduced cloned CD4+ T lymphocytes causes the appearance of Langerhans cells in the ear epidermis of Tgfb1(-/-) SCID mice. This effect is enhanced by antigen-specific activation of these T cells. Injection of recombinant active transforming growth factor-beta 2 into the ear of Tgfb1(-/-) SCID mice also results in the migration of Langerhans cells into the epidermis locally, but no epidermal Langerhans cells are seen after systemic injections of transforming growth factor-beta 2. Our results suggest that transforming growth factor-beta can act in paracrine as well as autocrine fashion to induce the differentiation of precursors into Langerhans cells. Furthermore, these results indicate that the relative roles of different transforming growth factor-beta isoforms in vivo may be influenced by their local availability and/or the regulation of their conversion from latent into active form.     

Immunohistochemical staining characteristics of epidermal appendages (hair follicles and eccrine sweat glands) to anti-epidermal keratin antisera

The cellular characteristics of the epidermal appendages and their differentiations in relation to those of the epidermis have been chiefly studied from the morphological points in the past. We investigated them from the immunohistochemical characteristics of the constituent keratin protein to the antiserum against total keratin isolated from human plantar stratum corneum (TKA) which stains the whole epidermis, and to the antiserum against 64K keratin separated from total keratin (64KA) which stains the whole epidermis except the basal layer. In the hair follicles, medulla and cortex of the hair shaft and inner root sheath were positively stained with both types of the antisera only at the keratogenous zone. The staining pattern of the outer root sheath with 64KA were variable at different levels of the hair follicle. The secretory portion of the eccrine glands showed a heterogeneous staining pattern as compared with the ductal portions which were stained homogeneously by both antisera. In eccrine poroma, all of the tumor cells were stained positively with TKA, while negatively or positively stained cells were intermingled with 64KA, suggesting that only some tumor cells showed mature keratinization.     

Acrosyringial keratinocytes--no abnormal differentiation in psoriasis vulgaris

Histochemical investigations were performed in normal and psoriatic epidermis to evaluate possible differences in the acrosyringial reactivity. Luminal (abundant in glycoconjugates, immunoreactive) and outer (almost nonreactive) epithelial cells could be distinguished. Psoriasis did not affect the staining pattern. The findings argue against a primary involvement of acrosyringial keratinocytes in the abnormal differentiation pathway of psoriatic epidermal cells. Moreover, they underline the relative independence of the acrosyringium from interfollicular epidermis.     

Distribution of metallothionein in normal and pathological human skin

The expression and distribution of metallothionein (MT) in frozen sections of normal and pathological human skin was studied using the monoclonal antibody L2E3 directed against MT derived from human fetal liver. Immunohistochemical staining of normal fetal and adult skin revealed strong reactivity in basal keratinocytes of epidermis and outer hair root sheath, hair matrix cells and the secretory coil, but not the exocrine portion of eccrine glands; myoepithelial cells around apocrine sweat glands were similarly stained. In epidermal hyperplasia, variable numbers of suprabasal keratinocytes were stained, whereas in interface dermatitis, interrupted staining was found in the basal layer. Weak or scattered staining was observed in squamous tumours, whereas basal cell carcinomas did not show consistent staining. The distribution of MT in normal skin was in line with the germinative role of basal keratinocytes and hair matrix cells, whereas its distribution in hyperplastic epidermis was in line with experimental animal data, and reflected the increase in the germinative pool in these conditions. It is concluded that monoclonal antibody L2E3 may serve as a valuable immunohistochemical marker in diagnostic cutaneous pathology since it labels basal keratinocytes selectively, and since it discriminates between eccrine and apocrine sweat glands.     

Expression of the basal cell adhesion molecule (B-CAM) in normal and diseased human skin

The basal cell adhesion molecule (B-CAM) is a 90-kD cell surface glycoprotein with a characteristic immunoglobulin domain structure. The pattern of B-CAM expression in cultured cells suggests that the molecule is associated with a substrate-adherent growth pattern in some lineages. We investigated the expression of B-CAM in normal and diseased human epidermis by means of immunohistochemistry employing a single batch of high-titer mouse monoclonal antibody G253. Snap-frozen biopsy material from normal skin (n = 8), psoriasis (n = 5), contact dermatitis (n = 6), basal cell carcinoma (n = 5) and fetal skin (n = 6) was studied. In normal human skin, B-CAM was found in varying degrees throughout the epidermis with a preference for suprabasal expression, hair follicles were regularly of a B-CAM-positive phenotype. There were no qualitative differences with regard to the B-CAM expression pattern in normal skin in comparison to psoriasis and contact dermatitis. In contrast, fetal skin (15th to 18th week of gestation) was characterized by B-CAM-positive cells in the basal layer of the epidermis as well as in the outer root sheath of hair follicles. Basal cell carcinomas also regularly expressed high levels of B-CAM. A strong B-CAM-positive phenotype can be found in the outer root sheath of hair follicles of adult and fetal human skin as well as in fetal basal keratinocytes.     

Peculiar vegetative tumor-like genital herpes simplex nodules with brisk tissue eosinophilia in patients with human immunodeficiency virus infection

Genital herpes simplex virus (HSV) infection in a human immunodeficiency virus (HIV) patient can present as a vegetative nodule. Clinical differential diagnoses of the nodule include condyloma latum, condyloma acuminatum, viral or fungal infection, and cutaneous neoplasms. Histological examination of herpetic nodules has been reported to show thick pseudoepitheliomatous hyperplasia with dense dermal lymphoplasmacytic infiltrate and multifocal multinucleated cells with herpetic viral cytopathic changes. We report two patients with HIV presenting with vegetative tumor-like HSV nodules with distinctive histopathologic pattern of inflammation that has not been described in the literature before. All samples displayed slightly acanthotic epidermis with focal ulceration, dense dermal sclerosis, scattered plasma cells, and a brisk lymphoeosinophilic infiltrate found dissecting between dense collagen bundles. This pattern of inflammation is an important clue that can guide the pathologist to look for focal herpetic viral changes in the epidermis, as patients with HIV possibly tend to amount a predominantly eosinophilic immune response in inflammatory skin conditions.     

Metallothionein expression in basaloid proliferations overlying dermatofibromas and in basal cell carcinomas

Basaloid proliferations overlying dermatofibromas which morphologically resemble superficial basal cell carcinomas have been interpreted as both reactive/regressive and frankly malignant. Metallothioneins (MTs) are low-molecular-weight proteins with a selective binding affinity for heavy metal ions. MTs has been proposed to represent a biological marker of carcinogenesis and, in a variety of human tumours, a correlation between immunohistochemically overexpresstion of MT and aggressive clinical behaviour has been shown. In order to clarify the nature of basaloid proliferations overlying dermatofibromas, we examined, immunohistochemically, 10 dermatofibromas with overlying simple hyperplasia, 16 dermatofibromas with overlying basaloid proliferation, and 35 basal cell carcinomas, for expression of MT. In normal epidermis, the basal keratinocytes showed cytoplasmatlc MT immunoreactivity. The staining intensity was stronger in the basal cells of the rete ridges, an observation which is in accordance with the high proportion of S-phase cells in this area. Simple hyperplasia showed the same MT expression pattern as normal epidermis. Basaloid proliferations stained like superficial and nodular basal cell carcinomas. Of nodular basal cell carcinomas, 92% (12 of 13) showed decreased/absent MT immunoreactivity, while 86% (six of seven) of infiltrating/morphoea-like basal cell carcinomas showed overexpression of MT (P = 0.001, Fisher's exact test). The results demonstrate that MT overexpression in basal cell carcinomas is correlated with infiltrative growth pattern. The similar expression of MT in basaloid proliferations and ‘non-infiltrating’ basal cell carcinomas suggests that these lesions share a common change in metabolism and/or differentiation.     

Hair follicle-like change over histiocytomas

Epidermal hyperplasia is a common finding overlying histiocytomas. Occasionally, a distinctive type of basaloid hyperplasia occurs, with differentiation into primitive hair follicle tissue. This study attempts to characterize this change and determine whether it is associated with any particular clinical or histological feature. Data from patients with histiocytomas displaying induction of pilar epithelium in the epidermis above the lesions was compared with data from controls who did not show this change. The size, site, and duration of histiocytomas were similar in both groups, as were the predominant cell type and distance of histiocytoma from the epidermis. Serial sectioning of histiocytomas showed that the induction of pilar epithelium was a focal phenomenon, often missed in routine sections. It is suggested that histiocytoma cells may produce a "hair organizing mediator."     

Thy-1 antigen-bearing dendritic cells populate murine epidermis

Two distinct cell populations, melanocytes and Langerhans cells (LC), have been recognized previously to possess dendritic configuration in normal mammalian epidermis. Employing immunofluorescence microscopy with monoclonal antibodies against Thy-1.2 antigen to identify cells in whole mounts of murine epidermis, we have identified a third dendritic cell population which differs from both LC and melanocytes. Thy-1 antigen-bearing (Thy-1+) epidermal cells are primarily dendritic, although round and angular forms may be found. They are distributed relatively evenly across skin surfaces, although densities vary greatly from site to site and from strain to strain. Densities were highest in ear epidermis from the pigmented strain B10.A (580 cells/mm2), a value approaching that of epidermal LC, and were lowest in ear epidermis from the albino strain BALB/c (5 cells/mm2). Thy-1+ epidermal cells possess neither Ia antigens nor substantial amounts of melanin, and their surface distributions are disparate from those of both LC and mature melanocytes. We propose that at least some of these cells are T lymphocytes whose malignant counterparts account for cutaneous T-cell lymphomas.