Keratinization Of Keratinocytes Research Articles

ALA-PDT alleviates the psoriasis by inhibiting JAK signalling pathway.

Photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA) is a well-known treatment for non-hypertrophic actinic keratoses and superficial basal-cell carcinomas. In this study, we first revealed that ALA-PDT treatment effectively ameliorated the psoriasis-like lesion in imiquimod (IMQ)-induced mouse model and further explored the potential molecular mechanism and related signalling pathways during the treatment. Besides, we also confirmed a significant alleviation of ALA-PDT therapy on IFN-γ-induced over-proliferation of keratinocytes. H&E staining was conducted to reveal the histological changes of mice in different groups. The different expression levels of RNA were illustrated by using QRT-PCR. Western blot was performed to confirm the various expression levels of protein in mice. In vitro, cell proliferation and cell cycle were evaluated by cell counting kit-8 and flow cytometry assay, respectively. The result showed that ALA-PDT's anti-proliferation effect and regulation on Socs1/3, JAK1/2 and K17 in IFN-γ-induced keratinocytes were largely weakened by NAC, indicating that ALA-PDT attenuated the proliferation of IFN-γ-induced keratinocytes by enhancing ROS level. These results demonstrated that ALA-PDT largely activated the productivity of Socs1/3 in a ROS-dependent manner. Socs1/3 is a potential blocker in JAK signalling pathway and inhibits the proliferation and keratinization of keratinocytes in psoriasis.

Blistering diseases

Blistering occurs in many situations — infections (viral and bacteriological), in response to physical or chemical trauma, as a reaction to drugs, and as a result of specific blistering diseases. The autoimmune blistering diseases, the pemphigus and pemphigoid group, are characterized by autoantobodies directed against antigens that are structural proteins forming part of the adhesion complexes of the skin. In pemphigus, autoantibodies are formed against desmogleins, the major component of the desmosomes, and result in superficial, intra-epidermal blistering, manifest as erosions of the skin and mucous membranes. The skin and mucosa differ in relative expression of the two desmogleins involved and the clinical picture correlates with the autoantibody profile. The pemphigoid group (bullous pemphigoid, mucous membrane pemphigoid, pemphigoid gestationis) is characterized by different clinical syndromes, all associated predominantly with autoantibodies to BP180, a large transmembrane protein forming part of the basement membrane zone adhesion complex that links the epithelium to the underlying dermis. The autoantibodies are known to be pathogenic in bullous pemphigoid and pemphigoid gestationis and lead to large, tense, subepidermal blisters. The different clinical syndrome of mucous membrane pemphigoid with erosions and scarring of mucosal surfaces is more difficult to explain. Genetic epidermolysis bullosa is characterized by mutations in skin structural proteins, either the keratinocyte keratins, with splitting through basal epidermal cells, or adhesion complex proteins, with blistering of the basement membrane zone.

The importance of laminin 5 in the dermal–epidermal basement membrane

The skin consists of two main layers, epidermis and dermis, separated by the basement membrane. Epidermal–dermal communication through the basement membrane is important for skin homeostasis. The basement membrane contains specialized structures, called the anchoring complex, which ensure the stability of connection and communication between these two tissue compartments. The proteins within the anchoring complex provide links to both the intracellular cytoskeletal keratins in keratinocytes and connective tissue proteins of the dermis. One of the key components of the complex is laminin 5, which is essential to epidermal cell attachment. The biological function of laminin 5 has been investigated by using a skin equivalent model in vitro and during keratinocyte sheet grafting in vivo. As a major link between the epidermal basal cells and the papillary dermis, laminin 5 initiates hemidesmosome formation and provides stable attachment of the epidermis to the dermis. Laminin 5 also accelerates the assembly of basement membranes and may enhance the recovery of damaged skin. An intact basement membrane at the epidermal–dermal junction is essential to stability of the skin.

Human keratin diseases: the increasing spectrum of disease and subtlety of the phenotype-genotype correlation.

Keratins are obligate heterodimer proteins that form the intermediate filament cytoskeleton of all epithelial cells. Keratins are tissue and differentiation specific and are expressed in pairs of types I and II proteins. The spectrum of inherited human keratin diseases has steadily increased since the causative role of mutations in the basal keratinocyte keratins 5 and 14 in epidermolysis bullosa simplex (EBS) was first reported in 1991. At the time of writing, mutations in 15 epithelial keratins and two trichocyte keratins have been associated with human diseases which include EBS, bullous congenital ichthyosiform erythroderma, epidermolytic palmoplantar keratoderma, ichthyosis bullosa of Siemens, diffuse and focal non-epidermolytic palmoplantar keratoderma, pachyonychia congenita and monilethrix. Mutations in extracutaneous keratins have been reported in oral white sponge naevus and Meesmann's corneal dystrophy. New subtleties of phenotype-genotype correlation are emerging within the keratin diseases with widely varying clinical presentations attributable to similar mutations within the same keratin. Mutations in keratin-associated proteins have recently been reported for the first time. This article reviews clinical, ultrastructural and molecular aspects of all the keratin diseases described to date and delineates potential future areas of research in this field.

Keratin expression in anal carcinoma: an immunohistochemical study.

The keratin expression of 40 frozen tissue specimens of anal carcinoma was investigated using a panel of 17 monoclonal antibodies to 14 individual keratins. The tumours were divided into three histological subgroups showing pure squamous, squamous and basaloid, or squamous and glandular differentiation. A further assessment of the tumour grade was made. The overall profile was of expression of keratins 4, 13, 17, 18 and 19 across the majority of the tumours, with the minority expressing keratins 1 and 10, and keratin 7. Dedifferentiation was associated with loss of expression of keratinocyte keratins, particularly the cornification markers keratin 1 and 10, and K6 and 16 associated with keratinocyte hyperproliferation and differentiation. This correlated with acquisition of the simple epithelial keratins 7 and 8. Compared with the tumours as a whole, well differentiated squamous tumours (the most easily identifiable histological group) showed consistent positivity for keratins 6 and 16, expressed suprabasally, while simple keratins 18 and 19 were also found. Independent of grade, mixed tumours showed more widespread positivity for simple epithelial keratins 7, 8 and 18 and loss of expression of cornification keratins 1 and 10 and K6 and 16 compared with pure squamous tumours. The relatively limited keratin profile of pure squamous tumours, predominantly consisting of keratinocyte keratins, suggests that these malignancies are less likely to originate from the region of the anal canal where the keratin profile is heterogeneous, i.e. the anal transitional zone.

Keratin expression in the normal anal canal

The pattern of epithelial keratin expression in the normal anal canal has not been extensively defined and is a necessary prerequisite to the interpretation of alterations in these intermediate filaments in pathological anal epithelial lesions. Thirty-five frozen tissue specimens of resected haemorrhoids were investigated immunohistologically for expression of 14 individual keratins (K) using a panel of 17 monoclonal antibodies. Perianal skin showed basal expression of keratinocyte Ks 5, 14 and 17, and suprabasal expression of keratinocyte Ks 14, 10, 1 and 16. Anal squamous epithelium showed persistent basal K5 and 17, basal and suprabasal K4, 13 and 16 positivity, with sporadic expression of K1 and 10. The expression of simple epithelial keratins in squamous epithelium adjacent to the anal transitional zone varied with basal expression of K7, K8, K18 and K19 and sporadic suprabasal expression of K7 and K19. The anal transitional zone (ATZ) expressed K19, as found in transitional epithelia elsewhere. The full thickness of epithelium was positive for the simple epithelial Ks 7, 8 18 and 19. Marked heterogeneity of keratinocyte keratin expression was seen. Basal layers expressed Ks 4, 13, 14 and 17 and variably K16, while suprabasal layers expressed Ks 4 and 13, 14 and 17 and variably K16, while suprabasal layers expressed Ks 4 and 13 and variably K14, 16 and 17. This anomalous expression of keratinocyte K4 and 13 has also been documented in transitional epithelium of the bladder. The anal glands and ducts showed a keratin distribution similar to the transition zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of keratinization of keratinocytes from fetal rat skin with N-(O-linoleoyl) ω-hydroxy fatty acyl sphingosyl glucose (lipokeratinogenoside) as a marker of epidermis

To elucidate the functional significance of sphingolipids altered in the epidermal differentiation, we examined the effects of sphingolipids on the activity of transglutaminase and the formation of cornified envelopes in the keratinocytes from fetal rat skin. N-(O-linoleoyl) ω-hydroxy fatty acyl sphingosyl glucose (lipokeratinogenoside) that was characteristically contained in the mammalian epidermis, as well as nonhydroxy fatty acid-containing GalCer and GlcCer, significantly enhanced the activity and the formation, but no or rather inhibited activity was observed with ceramides, GalCer with α-hydroxy fatty acid, saponified lipokeratinogenoside, etc. This indicates that skin-characteristic lipokeratinogenoside functions to regulate the transglutaminase for the formation of cornified envelopes in the process of keratinization.

Keratin 19: Predicted amino acid sequence and broad tissue distribution suggest it evolved from keratinocyte keratins

The type I keratin 19 is unusual in its tissue distribution in that under normal circumstances it does not seem to be restricted, as the other keratins are, to expression in either stratified or simple epithelia. In addition to the previously reported distribution of keratin 19 in human tissues, we have observed keratin 19 in epidermal basal cells, in a defined region of the hair follicle, and in nipple epidermis. We noticed that expression of keratin 19 appears to be especially characteristic of regions of labile or variable cellular differentiation as indicated by the presence of multiple keratin phenotypes in close proximity to each other. Using a monoclonal antibody recognizing keratin 19 (LP2K) to screen a human placenta cDNA expression library, we have isolated, cloned, and sequenced cDNA coding for full-length human keratin 19, as confirmed by its reactivity with several other known anti-keratin 19 monoclonal antibodies and by the near identity of its sequence with that of the bovine keratin 19 homologue. This similarity extends to both proteins being truncated at the C-terminal end to only 13 amino acids beyond the rod domain. Although the amino acid homology over the N-terminal and helical rod domains is particularly high, the human and bovine proteins diverge substantially over the short C-terminal domain, which suggests that this region has no conserved function. Comparison with other type I keratins indicates that the closest evolutionary neighbors of keratin 19 are keratinocyte keratins, probably 13 and 14, and not the simple epithelial keratin 18. Assessing the histochemistry and sequence data together, we propose that the cell may use this apparently deficient keratin as a “neutral” keratin. While unimpaired in its ability to polymerize (keeping the cell integrated into the epithelial sheet via filament-desmosome networks), keratin 19 expression does not irrevocably commit a cell to any one of the local differentiation options. Such predicted differentiational flexibility may also imply vulnerability to transformation.

Keratin 19: Predicted Amino Acid Sequence and Broad Tissue Distribution Suggest it Evolved from Keratinocyte Keratins.

The type I keratin 19 is unusual in its tissue distribution in that under normal circumstances it does not seem to be restricted, as the other keratins are, to expression in either stratified or simple epithelia. In addition to the previously reported distribution of keratin 19 in human tissues, we have observed keratin 19 in epidermal basal cells, in a defined region of the hair follicle, and in nipple epidermis. We noticed that expression of keratin 19 appears to be especially characteristic of regions of labile or variable cellular differentiation as indicated by the presence of multiple keratin phenotypes in close proximity to each other. Using a monoclonal antibody recognizing keratin 19 (LP2K) to screen a human placenta cDNA expression library, we have isolated, cloned, and sequenced cDNA coding for full-length human keratin 19, as confirmed by its reactivity with several other known anti-keratin 19 monoclonal antibodies and by the near identity of its sequence with that of the bovine keratin 19 homologue. This similarity extends to both proteins being truncated at the C-terminal end to only 13 amino acids beyond the rod domain. Although the amino acid homology over the N-terminal and helical rod domains is particularly high, the human and bovine proteins diverge substantially over the short C-terminal domain, which suggests that this region has no conserved function. Comparison with other type I keratins indicates that the closest evolutionary neighbors of keratin 19 are keratinocyte keratins, probably 13 and 14, and not the simple epithelial keratin 18. Assessing the histochemistry and sequence data together, we propose that the cell may use this apparently deficient keratin as a "neutral" keratin. While unimpaired in its ability to polymerize (keeping the cell integrated into the epithelial sheet via filament-desmosome networks), keratin 19 expression does not irrevocably commit a cell to any one of the local differentiation options. Such predicted differentiational flexibility may also imply vulnerability to transformation.

Retinoids as important regulators of terminal differentiation: examining keratin expression in individual epidermal cells at various stages of keratinization.

When human epidermal cells were seeded on floating rafts of collagen and fibroblasts, they stratified at the air-liquid interface. The suprabasal cells synthesized the large type II (K1) and type I (K10/K11) keratins characteristic of terminal differentiation in skin. At earlier times in culture, expression of the large type II keratins appeared to precede the expression of their type I partners. At later times, all suprabasal cells expressed both types, suggesting that the accumulation of a critical level of K1 keratin may be a necessary stimulus for K10 and K11 expression. Expression of the terminal differentiation-specific keratins was completely suppressed by adding retinoic acid to the culture medium, or by submerging the cultures in normal medium. In submerged cultures, removal of vitamin A by delipidization of the serum restored the keratinization process. In contrast, calcium and transforming growth factor-beta did not influence the expression of the large keratins in keratinocytes grown in the presence of retinoids, even though they are known to induce certain morphological features of terminal differentiation. Retinoic acid in the raft medium not only suppressed the expression of the large keratins, but, in addition, induced the synthesis of two new keratins not normally expressed in epidermis in vivo. Immunofluorescence localized one of these keratins, K19, to a few isolated cells of the stratifying culture. In contrast, the other keratin, K13, appeared uniformly in a few outer layers of the culture. Interestingly, K13 expression correlated well with the gradient of retinoid-mediated disruptions of intercellular interactions in the culture. These data suggest that K13 induction may in some way relate to the reduction in either the number or the strength of desmosomal contacts between suprabasal cells of stratified squamous epithelial tissues.

Apoptosis in lichen planus and several other dermatoses. Intra-epidermal cell death with filamentous degeneration.

In hyperplastic conditions of the skin, eosinophilic bodies are often observed in the epidermis and upper dermis. These have been named variously Civatte body of lichen planus and dyskeratotic cell of actinic keratosis. In the present studies, it was found that (i) these cells commonly contain whorls of distinct filaments (60-80 A), which may be attached to desmosomes; (ii) unlike keratinized cells, the cellular envelope was not thickened by the formation of the marginal band; (iii) the cytoplasm contains a large number of vacuoles; (iv) the nucleus is lost by condensation or diffuse disintegration; and (v) these cells could be dropped into the upper dermis and filamentous contents could be released to dermal phagocytes. From these observations it was concluded that Civatte bodies and other eosinophilic bodies of neoplastic and hyperplastic epidermis represent "filamentous degeneration" or premature keratinization of keratinocytes.

Apoptosis in lichen planus and several other dermatoses. Intra-epidermal cell death with filamentous degeneration

In hyperplastic conditions of the skin, eosinophilic bodies are often observed in the epidermis and upper dermis. These have been named variously Civatte body of lichen planus and dyskeratotic cell of actinic keratosis. In the present studies, it was found that (i) these cells commonly contain whorls of distinct filaments (60-80 A), which may be attached to desmosomes; (ii) unlike keratinized cells, the cellular envelope was not thickened by the formation of the marginal band; (iii) the cytoplasm contains a large number of vacuoles; (iv) the nucleus is lost by condensation or diffuse disintegration; and (v) these cells could be dropped into the upper dermis and filamentous contents could be released to dermal phagocytes. From these observations it was concluded that Civatte bodies and other eosinophilic bodies of neoplastic and hyperplastic epidermis represent "filamentous degeneration" or premature keratinization of keratinocytes.