Bicomponent keratohyalin in normal human ridged skin

Summary Up to now, bicomponent keratohyalin has only been described for rat epithelium and human intraepidermal sweat ducts and fetal nail organ cells. In normal human interductal epidermis, the keratohyalin appears homogeneous, osmiophilic and stellate in shape. Under pathological conditions, bicomponent keratohyalin has been observed in different palmoplantar keratoses and has therefore been thought to be associated with abnormal keratosis. We studied the keratinization process in normal human plantar epidermis, in which keratohyalin was found to exhibit several morphological differences as compared to that seen in non-ridged skin. The most striking feature was seen in upper granular cells, where the keratohyalin granules consisted of two components of differing electron density. The electron-dense component formed the main part of the composite granule and was found in the cytoplasm of lower and upper granular cells. The less-electron-dense component was attached to the main component and appeared in the cytoplasm of upper granular cells, forming the convex contact zone. No intranuclear osmiophilic inclusions were present. The respective electron densities of the two keratohyalin components of ridged skin were obviously different to that of the bicomponent keratohyalin granules seen in the epidermal sweat-duct cells of the same specimen. These findings indicate the presence of at least two different types of keratohyalin proteins in normal human ridged skin. They can be distinguished at the electron-microscope level and differ from the keratohyalin of human non-ridged skin as well as from bicomponent keratohyalin granules derived from human epidermal sweat-duct cells or from rat epithelium.     

Amyloid P component binds to keratin bodies in human skin and to isolated keratin filament aggregates in vitro

Dermal keratin bodies, consisting mainly of keratin intermediate filament aggregates (KIFA) coated with IgM anti-KIF autoantibodies, are present in normal human skin and occur in increased quantities in certain skin diseases. Keratin bodies are normally rapidly removed, but in primary localized cutaneous amyloidosis (PLCA) they are converted by an unknown mechanism to amyloid. Amyloid P component (AP), a glycoprotein identical to, and derived from, the normal plasma protein serum amyloid P component (SAP), is present in all forms of amyloid including PLCA. We investigated the interaction between SAP, keratin bodies, and KIFA. Immunofluorescence staining of normal skin using fluoresceinated anti-SAP and rhodamine-conjugated anti-IgM, or AE-1/AE-3 anti-keratin antibodies followed by Texas Red-conjugated anti-mouse immunoglobulin, showed that 52% +/- 4 (mean +/- sem, n = 6) of keratin bodies bound anti-SAP. Similar findings were present in a biopsy from a patient with lichen planus. Isolated KIFA, prepared by 8M urea extraction of normal human epidermis or cultured keratinocytes, were preincubated with normal human serum as a source of SAP and then stained with fluoresceinated anti-SAP. Bright fluorescence seen when the incubation medium contained Ca++ was absent in the presence of ethylenediamine tetraacetic acid. Specific Ca++-dependent binding of SAP to KIFA was confirmed using immunoblotting. Binding of SAP to KIFA did not prevent their degradation following exposure to trypsin or alpha-chymotrypsin. Similarly, partial enzymatic digestion of KIFA did not abrogate their ability to bind SAP. Our findings, that SAP is associated with keratin bodies in skin and exhibits Ca++-dependent binding to KIFA in vitro, identify keratin filaments as a newly recognized ligand for SAP.     

Ontogeny and regional variability of keratin 2e (K2e) in developing human fetal skin: a unique spatial and temporal pattern of keratin expression in development

Keratin 2e (K2e) is expressed in the upper spinous and granular cells of adult epidermis. A highly specific polyclonal antibody was made against a C-terminal peptide of K2e and used to observe K2e expression at different developmental stages. At 12.5 weeks estimated gestational age (EGA) K2e was detected in trunk skin in scattered cells in the intermediate layer. At 13.5 weeks EGA, greater numbers of intermediate cells were stained with variable intensity, and staining in this pattern increased with age. Epidermal sheets from 14 weeks EGA showed that K2e + cells were excluded from developing hair follicles. At 135 days EGA, the following regional patterns were observed: in cheek, trunk, dorsal and ventral knee, elbow and dorsal hand there was moderate to intense staining of upper intermediate keratinocytes excluding cells of the hair canals and sweat ducts. The periumbilical region distinctly lacked K2e staining, while more distal areas showed increasing numbers of K2e + cells. The earliest expression of K2e was at 10 weeks EGA in the presumptive nail bed of developing digits. By 13.5 weeks EGA this pattern had shifted to the proximal nail fold, and K2e was absent in the nail bed. K2e was excluded from developing sweat glands and ducts and from developing hair follicles at the hair germ and early peg stages. By 15 weeks EGA in the fetal hair follicle small groups of cells were K2e + and by 19 weeks K2e + cells were seen at the level of the matrix. Some overlap in staining was detected for K2e with K10, and in palmar skin with K9; however, mostly the filamentous staining patterns for these keratins were distinctive. This study shows that the complex patterns of temporal and regional expression of K2e differ from known patterns for other epidermal keratins and suggest different regulation and function for this epidermal keratin.     

Hair keratin pattern in human hair follicles grown in vitro

The keratin family includes epithelial (soft) keratins and hair (hard) keratins, and can be divided into acidic type I and basic to neutral type II subfamilies. Recently, nine type I and six type II hair keratin genes have been characterized through the screening of a human PAC library. The expression of these genes in the hair follicle was determined in vivo and a combined catalog of acidic and basic hair keratins was established. In this study, we investigated the expression and localization of most of the human hair keratin members of both types in human hair grown in vitro. We show that in vitro growth of hair follicles for 10 days in complete William's E culture medium did not alter the expression pattern of hair keratins. Similarly to the in vivo situation, each hair keratin was localized in precise and discrete compartments of the follicle, ranging from the matrix to the upper cortex and/or the hair cuticle. This study shows that the increase in length of in vitro grown follicles was accompanied by the proper hair shaft keratinization process. It also shows that hair follicle integrity was maintained in vitro, both in terms of gross morphology and molecular organization despite the complexity of the keratin expression pattern.     

瘦素调节HaCaT细胞角蛋白17的表达

目的 探讨瘦素对HaCaT细胞角蛋白17（K17）表达的影响。 方法 体外培养HaCaT细胞,给予100 ng/ml的瘦素作用24 h,应用实时PCR检测K17 mRNA表达水平、Western印迹及免疫荧光染色法检测K17蛋白表达水平变化。 结果 与阴性对照组（1.000 0 ± 0.000 0）相比较,瘦素组（3.086 7 ± 0.186 1）K17 mRNA表达显著升高,差异有统计学意义（P < 0.01）。Western印迹结果表明,瘦素组K17蛋白较阴性对照组显著上调,细胞免疫荧光染色结果与RT-PCR、Western印迹结果相符。与单纯使用瘦素组（2.242 7±0.188 7）相比较,STAT3抑制剂组和Erk1/2抑制剂组K17 mRNA分别为0.674 1 ± 0.060 0、0.855 0 ± 0.390 3,Western印迹和细胞免疫荧光染色显示,两个抑制剂组的K17蛋白较瘦素组均显著下调,差异均有统计学意义（P < 0.01）。 结论 瘦素可以诱导HaCaT细胞表达K17,其机制可能与激活STAT3、Erk1/2信号转导途径有关。     

白介素22调控角质形成细胞表达角蛋白17的研究

目的:研究白介素(IL)-22对培养的人永生化角质形成细胞(HaCaT细胞)表达角蛋白(K)17的影响.方法:对体外培养的HaCaT细胞分别给予不同浓度的IL-22(0 ～ 100 μg/L)作用24 h,应用实时荧光定量聚合酶链式反应(real-time PCR)检测K17mRNA 表达水平,以酶联免疫吸附测定技术(ELISA 法)、蛋白质免疫印记法(Western blot)及免疫荧光染色法检测K17 蛋白表达水平的变化.结果:HaCaT细胞经12.5、25.0、50.0、100.0 μg/L 的IL-22 作用后, 均出现不同程度的K17 表达.与空白对照组的HaCaT细胞相比,12.5 μg/L组的mRNA及蛋白表达无明显差异,而25.0、50.0、100.0 μg/L组的mRNA 及蛋白表达则明显上升(P ＜0.05),并且随着IL-22浓度增高,K17mRNA及蛋白表达量增多.免疫荧光染色图片显示,随着IL-22 浓度的增高,HaCaT细胞胞质中K17蛋白荧光染色增强.结论:IL-22可以剂量依赖方式诱导HaCaT细胞表达K17.     

Changes in keratin 6 and keratin 10 (co-)expression in lesional and symptomless skin of spreading psoriasis

BACKGROUND: Keratin 6 (K6) and keratin 10 (K10) are markers for epidermal hyperproliferation and differentiation, respectively, and are both expressed in the suprabasal layers of the epidermis. They may be co-expressed in different stages of the spreading psoriatic lesion, but single expression can also occur. OBJECTIVE: To investigate to what extent keratinocytes express K6 and K10, and to what extent they co-express K6 and K10 in different stages of the psoriatic lesion. We studied this in spreading psoriatic plaques. METHODS: Three 3-mm punch biopsies were obtained from the inner involved margin of a spreading lesion, from the uninvolved skin immediately adjacent to the spreading plaque, and from the distant uninvolved skin of 8 patients with incipient psoriasis. From 9 healthy volunteers, 3-mm punch biopsies were obtained as controls. After preparation of single cell suspensions of these biopsies, a triple staining protocol was performed with markers for K6 (monoclonal antibody LHK6B), K10 (monoclonal antibody RKSE60) and DNA content (TO-PRO-3 iodide). Subsequently, cells were measured with a flow cytometer and the proportion of the markers was calculated using specific software. RESULTS: We observed a population of K6/K10-co-expressing cells, but also populations expressing only K6. These subpopulations varied with the involvement of the lesion. There was a statistically significant difference between the inner margin and the outer margin with respect to the proportion of K6- and K10-expressing cells, whereas more K6-positive and K10-negative cells were detected in the inner margin of the lesions. The proportion of K6/K10-co-expressing cells in the inner margin was significantly different from the distant uninvolved skin. CONCLUSION: We confirmed that individual keratinocytes in psoriasis can express K6 or K10 depending on their localization in involved or uninvolved skin. There is a unique subpopulation of cells in the psoriatic plaques which co-express K6 and K10. More studies are required to fully understand the pathogenic relevance of co-expression and single expression of K6 and K10.     

Lipase expression in human skin

We have used a monoclonal antibody against human pancreatic lipase to study the immunohistochemical expression of lipase in formalin-fixed, paraffin-embedded biopsy specimens from normal and a variety of tumoral and inflammatory skin diseases. In normal skin, lipase is detected in the sebaceous glands and in the external root sheath of the hair follicle. Antibody to lipase might be a valuable reagent to help confirm sebaceous and follicular differentiation in adnexal tumors. Immunoreactivity to lipase is also detected within mononuclear phagocytes in situations where extracellular release of lipids occurs, such as in xanthomas or in inflammation of the fat with significant lysis of adipocytes. The antibody to lipase identifies a major protein in pilosebaceous homogenates of 42.7 kDa following immunoblotting.     

Altered keratin expression in benign and malignant skin diseases revealed with monoclonal antibodies

We studied keratin expression in benign epidermal skin diseases, and in Bowen's disease by using three monoclonal cytokeratin antibodies. In adult normal skin, these antibodies bind only to the follicular epithelium (PKK1), the basal keratinocytes (PKK2), or the suprabasal cells in interfollicular epidermis (KA5). Additionally, in fetal epidermis, the PKK1 antibody reacts with basal keratinocytes. In psoriasis and lichen planus, the PKK2 antibody distinctly revealed all epidermal cell layers by immunostaining. However, a negative basal cell-like layer was revealed in both lesions with the KA5 antibody. In pityriasis rubra pilaris, the basal cell layer was uniformly stained with the PKK2 antibody, but only some keratinocytes in upper cell layers showed fluorescence and, in chronic eczema, the 3-4 lowest epidermal cell layers were reactive. The PKK1 antibody did not stain interfollicular keratinocytes in any of the benign proliferative skin diseases studied. In Bowen's disease, a heterogeneous staining pattern with varying intensity among individual cells was seen with all of the antibodies used. Our results suggest different changes in keratin expression in chronic benign and malignant epidermal diseases that may reflect the mechanisms behind these changes.     

Reproducible pattern of microRNA in normal human skin

Please cite this paper as: Reproducible pattern of microRNA in normal human skin. Experimental Dermatology 2010; 19 : e201–e205. Abstract: MicroRNAs (miRNAs) regulate cell growth, differentiation and apoptosis via specific targeting of messenger RNA (mRNA). Aberrant mRNA expression contributes to pathological processes such as carcinogenesis. To take advantage of miRNA profiling in skin disease it is essential to investigate miRNA expression pattern in normal human skin. Here we investigated miRNA expression profiles from skin biopsies of 8 healthy volunteers taken from sun protected and mildly photo damaged skin using the modified protocol for miRNA extraction. We were able to show a constant pattern of miRNA expression between different individuals. We did not find any significant differences in miRNA expression between sun protected and mildly photodamaged skin. These results may be valuable for future design of studies on miRNA expression in skin disease.     

Ageing processes influence keratin and KAP expression in human hair follicles

In many cultures, a youthful look is strictly linked to strong and healthy hair. Source of the hair fibre is the hair follicle, a highly specialized skin appendage. Biological alterations because of intrinsic or extrinsic stimuli can destabilize this perfectly organized system, thus effecting hair growth or metabolism. Also, ageing could be characterized as a disturbance in this well-balanced machinery. Albeit the predominant symptom of hair ageing, greying, is addressed in a plurality of research activities, further age-related changes, e.g. related to hair structure, remain obscure. Therefore, we characterized hair follicles of two volunteer panels (below 25 years, above 50 years) on the molecular level, especially focussing on alterations influencing gene expression of keratins and keratin-associated proteins. We showed that concordantly to other biological systems the hair follicle undergoes several modifications during the ageing process associated among others with a significant decline in these structural proteins. Providing strategies to fight against these age-related changes is a challenge for hair science.     

Neutrophils infiltrating ultraviolet B-irradiated normal human skin display high IL-10 expression

Exposure to an erythemal dose of ultraviolet B (UVB) is known to induce interleukin (IL-10) expression in human skin. It is generally believed that this IL-10 is predominantly expressed by CD11b⁺HLA-DR⁺ macrophages that infiltrate the UVB-exposed skin. This cytokine is presumed to contribute to the immunosuppressive effects of UVB by inhibiting cell-mediated immune responses. We recently demonstrated that neutrophils, which also invade UVB-irradiated skin, express CD11b and HLA-DR as well. In addition, we showed that the presence of these neutrophils affects T-cell responses in primary T-cell cultures derived from UVB-exposed skin. Since neutrophils invade UVB-exposed skin and, like macrophages, express CD11b and HLA-DR, we sought to determine whether neutrophils represent another source of IL-10. Skin biopsies were obtained from four healthy volunteers before and 2 days after exposure to four minimal erythema doses of UVB. A series of immunohistochemical double-staining procedures using the following markers was performed: IL-10, CD11b, HLA-DR, CD36, neutrophil elastase, and CD66b. As expected IL-10 could be detected in CD11b⁺HLA-DR⁺CD36⁺ macrophages in the epidermis and dermis of UVB-exposed skin. Surprisingly, the majority of the abundant IL-10 expression was found in CD11b⁺HLA-DR⁺elastase⁺CD66b⁺ neutrophils. Cytospin preparations from dermal cell suspensions confirmed the IL-10 expression by neutrophils displaying characteristic multilobular nuclei. Thus, neutrophils in UVB-exposed skin express IL-10 and should be recognized as active coplayers in the creation of the UVB-induced immunosuppressive microenvironment.     

Mammalian SIRT2 inhibits keratin 19 expression and is a tumor suppressor in skin

SIRT2 is a member of the mammalian sirtuin family (SIRT1‐7). As compared with other sirtuins, SIRT2 is found primarily in the cytoplasm. It regulates multiple physiological processes. However, the precise role of SIRT2 in skin cancer remains unclear. Here, we show that SIRT2 is downregulated in human skin cancer as compared with normal skin. SIRT2 deletion increases tumor growth in mice. SIRT2 knockdown upregulates the stem cell marker Keratin 19 (K19) in keratinocytes. In mice, SIRT2 deletion up‐regulates K19 and K15 while it down‐regulates the differentiation marker Loricrin in both normal skin and tumors. In skin tumors but not normal skin, SIRT2 deletion up‐regulates the stem cell marker CD34 and increases the number of Ki67‐positive cells. These findings indicate that SIRT2 is a tumor suppressor in the skin. Our findings add new insights into the role of SIRT2 in the molecular pathogenesis of skin cancer.