Keratin Pattern Research Articles

The Keratins of the Human Beard Hair Medulla: The Riddle in the Middle

We have investigated the expression of 52 of the 54 keratins in beard hair medulla. We found that not only 12 hair keratins but, unexpectedly, also 12 epithelial keratins are potentially expressed in medulla cells. The latter comprise keratins also present in outer- and inner-root sheaths and in the companion layer. Keratins K5, K14, K17, K25, K27, K28, and K75 define a "pre-medulla," composed of cells apposed to the upper dermal papilla. Besides K6, K16, K7, K19, and K80, all pre-medullary epithelial keratins continue to be expressed in the medulla proper, along with the 12 hair keratins. Besides this unique feature of cellular keratin co-expression, the keratin pattern itself is highly variable in individual medulla cells. Remarkably, both epithelial and hair keratins behave highly promiscuously with regard to heterodimer- and IF formation, which also includes keratin chain interactions in IF bundles. We also identified cortex cells within the medullary column. These exhibit all the properties of genuine cortex cells, including a particular type of keratin heterogeneity of their compact IF bundles. In both keratin expression profile and keratin number, medulla cells are distinct from all other cells of the hair follicle or from any other epithelium.

Intermediate Filament Keratin Dynamics During Oocyte Maturation Requires Maturation/M-Phase Promoting Factor and Mitogen-Activated Protein Kinase Kinase Activities in the Hamster

Research related to intermediate filaments in mammalian oocytes remains poorly advanced. We investigated keratin reorganization in oocytes during meiotic maturation using immunofluorescence, and examined effects of inhibitors for cdc2 and mitogen-activated protein kinase kinase (MAPKK) on keratin assembly. In germinal vesicle (GV) oocytes (n = 26), large and oval-shaped aggregates of non-fibrillar keratin were found in the cortical ooplasm (designated as a 'cortical' pattern). The delicate network of keratin filaments was concentrated in the GV periphery. The large keratin aggregates began to divide into small fragments at the pro-MI/MI stage (n = 22, designated as a 'fragmented' pattern). Some keratin fragments were occasionally broken down into several granules at the peripheral region. In the MII oocytes (n = 24), the filament network was extended over the ooplasm and numerous keratin granules were scattered across the oocyte (designated as a 'granular' pattern). After 12 h of incubation with roscovitine, 66.7% of the oocytes (20/30) were at the GV stage and showed a cortical pattern of keratin. After incubation with U0126, most oocytes (83.9%, 26/31) were at the MII stage; most of them (76.9%, 20/26) showed a fragmented pattern of keratin. The increasing complexity of keratin filament network from the GV to MII stages suggests a possible role in maintaining cell integrity under physical stress after ovulation. In fact, maturation/M-phase promoting factor is necessary for such keratin reorganization, as is meiotic nuclear progression. In addition, MAPKK is involved in keratin reorganization from a fragmented pattern to a granular pattern.

Staining patterns of keratins in the human urinary tract.

The keratins, members of the intermediate filament family, are characteristically expressed in epithelial cells. In the various types of epithelia, the keratin expression pattern is characterized by cell-type specific combinations of the keratin isotypes with a plain pattern in monolayered (simple) epithelia and more complex patterns in stratified and pseudostratified epithelia. Here we demonstrate that the transitional epithelium of the human urinary tract holds an exceptional position between the pseudostratified and stratified epithelia. We show that the simple epithelia keratins 7, 8, 18 and 19 are expressed throughout the whole epithelium as known from pseudostratified epithelia. In addition, we demonstrate expression of keratins 5, 14 and 17, otherwise present in basal cells of multilayered epithelia, and keratins 4 and 13, present in suprabasal areas of non cornified multilayered epithelia. Moreover, we report differences in expression in the various morphological parts of the urinary tract which might be related to their specific functions. Keratin 20, a typical component of the simple epithelia of the digestive tract, is present in bladder and ureter but not in the renal pelvis. Keratin 6, typical for stratified epithelia, is found only in parts of the renal pelvis. We further show that changes in keratin pattern occur during the development from embryonic to adult bladder urothelium. In contrast to adult tissue, the simple type keratins 7, 8 and 18 are not synthesized in basal embryonic cells. Further, keratin 20, present in cells facing the bladder lumen in adult urothelium, is expressed in all but the basal cells in embryonic bladder.

Keratin Expression in Endocrine Organs and their Neoplasms

Keratins are intermediate filaments that provide mechanical support and fulfill a variety of additional functions in epithelial cells. Keratins show outstanding degree of molecular diversity. In humans, 54 functional keratin genes exist. Twenty common types of keratins are expressed in highly specific patterns related to epithelial type and stage of cellular differentiation. In general, keratins are classified as high-molecular-weight keratins (expressed in normal stratified epithelium and tumors derived from it) and low-molecular-weight keratins (expressed in normal simple epithelium and tumors derived from it). Histologically, endocrine organs belong to simple epithelium; thus, endocrine tissues usually express low-molecular-weight keratins. When an endocrine organ undergoes malignant transformation, its keratin profile usually remains constant. However, keratin expression in endocrine organs and endocrine tumors is much more complicated because of their diversified histogenesis. In this review article, we will first briefly review the molecular biology and protein chemistry of the keratins. We will then review the expression patterns of keratins in normal endocrine tissue and endocrine neoplasms.

Dealing wildlife offences in India: Role of the hair as physical evidence

India is known for its rich biodiversity, with a wide variety of wild floral and faunal species. This wildlife treasure of ours faces the threat of extinction due to rampant poaching and illegal trade. With most of the wildlife offence cases related to mammals having hair as physical evidence, it becomes imperative to use this evidence in the best possible way for wildlife crime investigation. We discuss the value of hair evidence with special reference to species characterization/identification using microscopic hair characteristics, keratin patterns, and mitochondrial DNA typing. The relevance of the techniques with respect to Indian scenario is specially taken care of and microscopic hair characteristics of one of the highly endangered species along with its keratin pattern are described. Finally, the use of mitochondrial DNA for species identification is also discussed.

Alterations of the Medullary Epithelial Compartment in the Aire-Deficient Thymus: Implications for Programs of Thymic Epithelial Differentiation

A widely held model of thymic epithelial differentiation is based on patterns of keratin expression, where a K8(+)K5(+) progenitor gives rise to K8(+)K5/K14(-) cortical thymic epithelium (CTEC), and medullary thymic epithelium (MTEC) are K8(-)K5(+)K14(+). The thymic phenotype of p63-deficient mice indicates that p63 is an important regulator of proximal stages of thymic epithelial differentiation. In this study, we have examined several features of the thymic medullary compartment in wild-type and Aire-deficient thymi in an effort to integrate the proapoptotic activity of Aire with these different perspectives of TE differentiation. Patterns of keratin and p63 expression by MTEC described here are difficult to reconcile with postmitotic MTEC that express a K8(-)K14(+) phenotype and suggest that the patterns of p63 and keratin expression reflecting differentiation programs of other epithelial tissues provide a useful framework for revising models of TE differentiation. Alterations of the Aire(-/-) MTEC compartment included reduced expression of p63, increased frequency of MTEC expressing truncated Aire protein, and shifts in the pattern of keratin expression and epithelial morphology. These data suggest a scenario where cellular targets of Aire-mediated apoptosis are postmitotic MTEC that have not yet completed their terminal differentiation program. According to this view, the minor population of globular K8(+)K14(-/low) MTEC observed in the Aire(+/+) thymus and significantly expanded in the Aire(-/-) thymic medulla represent end-stage, terminally differentiated MTEC. These Aire-dependent alterations of the MTEC compartment suggest that the activity of Aire is not neutral with respect to the program of MTEC differentiation.

New concepts on the histogenesis of eccrine neoplasia from keratin expression in the normal eccrine gland, syringoma and poroma

Peripheral and luminal layers of eccrine sweat gland ducts are self-renewing structures. Proliferation is restricted to the lowermost luminal layer, but randomly scattered in the peripheral layer. Each layer exhibits differential expression of keratins K5/K14 and K6/K16. Keratin K1 occurs only in peripheral cells and the novel keratin K77 is specific for luminal cells. To investigate the expression of luminal (K77), peripheral (K1) and further discriminatory keratins in two eccrine sweat gland tumours: syringoma, thought to show differentiation towards luminal cells of intraepidermal sweat ducts and eccrine poroma, considered to arise from poroid cells, i.e. peripheral duct cells; and keratinocytes of the lower acrosyringium/sweat duct ridge differentiating towards cells of intradermal/intraepidermal duct segments. Paraffin-embedded sections were examined by immunohistochemistry using several keratin, smooth muscle actin and Ki-67 antibodies. We confirmed the ductal nature of syringomas. Despite drastic morphological alterations in both layers, their keratin patterns remained almost undisturbed compared with normal ducts. In eccrine poroma epidermal keratins K5/K14 were ubiquitously expressed in all poroid cells. Cell islands deviating morphologically from poroid cells contained epidermal keratins K1/K10. K77 expression was limited to luminal cells of intact duct structures within the tumours. Syringomas are benign tumours of luminal cells of the lowermost intraglandular sweat duct. Poroid precursor cells of poromas do not comprise peripheral duct cells nor do poromas differentiate towards peripheral or luminal duct cells. Instead, poroid cells consist only of keratinocytes of the lowermost acrosyringium and the sweat duct ridge and poromas tend to differentiate towards the cells of the upper acrosyringium.

Isotretinoin: state of the art treatment for acne vulgaris

Isotretinoin (13-cis retinoic acid) is the most potent known inhibitor of sebum production. The multiple modes of action for isotretinoin, including suppression of sebaceous gland activity, normalization of the pattern of keratinization within the sebaceous gland follicle, inhibition of inflammation, reduction of growth of Propionibacterium acnes in a secondary manner and, as currently shown, normalization of the expression of matrix tissue metalloproteinases and their inhibitors make this compound the single most effective in the treatment of severe recalcitrant nodulocystic acne, and in the prevention of acne scarring. Several generic formulations for oral use have recently been introduced, in addition to the brand formulations Roaccutane® and Accutane™ (Roche). This development, considering the high risk of teratogenicity associated with oral isotretinoin use, has led the European Commission and the European Medicines Agency (EMEA) to release a directive towards the harmonization of the Summary of Prod...

Expression of Follicular Sheath Keratins in the Normal Nail With Special Reference to the Morphological Analysis of the Distal Nail Unit

The origin and the histology of the distal nail unit remain controversial. For some authors the nail bed is completely derived from the matrix epithelium and is not a self-regenerating, independent structure. The term onycholemmal keratinization has been used variably to describe both the so-called superficial horny layer without the granular layer of the nail bed, and the epidermal keratin of the hyponychium (HYN) and the eponychium. On the other hand, several contradictory systems of comparisons and homologies between components of the nail unit and those of the follicular sheaths have been proposed. Recently, the expression profiles of the epithelial keratins of the follicular sheaths have been determined in the human anagen hair follicle, but they have been only partially analyzed in the nail unit. This study was conducted to elucidate the morphology of the distal nail unit. To clarify the degree of homology between the nail unit and follicular sheaths, a selected set of keratins (K) was used. Formalin-fixed paraffin sections of adult nails were examined using mono- and polyclonal keratin antibodies, which are characteristic, respectively, for the inner root sheath, the companion layer, and the outer root sheath, as well as K10 and the antibody Ki-67 (antigen expressed in cycling cells). Longitudinal as well as transverse sections were investigated. The pattern of the keratins in the nail unit differs from that of the follicle in two points: the lack of an IRS-like compartment and of the companion layer. The expression of K6hf was observed almost exclusively in the nail bed. K6 and K16 were expressed in the eponychium, the apical matrix, and the nail bed, but not in the ventral matrix. Distribution of K6 and K16 was essentially suprabasal. On the basis of morphologic and biochemical considerations, the distal nail unit can be divided into three segments. The nail bed, which represents the main segment of distal nail unit, does not differentiate into a thin, orthokeratinizing surface. The nail isthmus is typified by a peculiar mode of keratinization (ie, a compartment of pale, nucleated corneocytes), which is closely adherent to the inferior border of the nail plate, including its distal free edge. The nail isthmus presents a profile of keratin expression in transition between the nail bed and HYN. The keratin pattern of the nail bed, including K6hf, is maintained. However, the nail isthmus differs from the nail bed in that K10 is only present in nail isthmus. The HYN differs from the nail isthmus in that K6hf is absent in HYN. In addition, the HYN shows, progressively or abruptly, a loss of expression of K6/16, and K5/17 expression returns to a basal pattern. The mean Ki-67 labeling index of ventral matrix, nail bed including nail isthmus, and distal HYN were, respectively, 21.16%, 5.2%, and 16.43%. The nail bed epithelium is an independent, specialized, epithelial structure with a true basal layer presenting a heterogeneous but significant proliferative activity. The so-called horny layer of the nail bed corresponds, in fact, to the superficial cells of the spinous layer of the nail bed. In this zone, the intercellular "spines" are barely detectable between cells replete with pink to brightly eosinophilic cytoplasm. The interlocking of the inferior border of the nail plate and the surface of the bed explain the strong attachment between the two tissues. The nail isthmus represents a transitional zone between the nail bed and the HYN and exhibits a pattern of keratinization different from the HYN. The cornified layer of the nail isthmus closely adheres to the undulating inferior surface of the nail plate; the two grow forward together. Therefore, the horny layer of the nail isthmus offers an effective sealing of the distal nail bed, preventing onycholysis. The terms matricial keratinization and onycholemmal keratinization could describe, respectively, the keratinization of the matrix and the nail isthmus.

Development and Characterization of a Human Tissue-Engineered Oral Mucosa

Open wounds in the mouth should be covered by a graft to prevent microbial infection, excessive fluid loss, foreign material contamination, or relapse (secondary to wound contracture). Currently oral mucosal or skin grafts are used for this purpose; however, both of these grafts require a second surgical procedure and have disadvantages in intraoral use. Split thickness skin grafts may contain adnexal structures, and express a different pattern of surface keratinization. The elective nature of the majority of oral and maxillofacial surgical procedures should allow the flexibility and timing to develop a tissue-engineered oral mucosa. As a tissue-engineered skin has been developed to treat patients suffering burn wounds, chronic ulcers, etc, there is a similar need for the development of a tissue-engineered oral mucosa suitable for intraoral grafting procedures. This graft would be used after major trauma, surgical resections, and for maxillofacial prosthetic surgery. Our research team has been successful in developing an ex vivo produced oral mucosal equivalent (EVPOME) fabricated in an environment free of serum, transformed irradiated feeder cells and pituitary extract. Our EVPOME consists of autologous oral mucosa keratinocytes and an acellular, non-immunogenic dermal equivalent, AlloDerm. The EVPOME was cultured at an air-liquid interface for up to two weeks, resulting in a well-differentiated, parakeratinized epithelial layer similar to native oral mucosa. The expression pattern of differentiation and proliferation markers showed an active and hyperproliferative state. The ultrastructure of EVPOME demonstrated hemi-desmosome-like structures were formed at the interface (basement membrane) of basal keratinocytes and a dermal layer by day 7 at an air-liquid interface. Tissue-engineered cell-based products usually fall under the auspices of the Center for Biological Evaluation and Research (CBER). They are considered a combination product by the Food and Drug Administration (FDA), and need to comply with the regulatory standards for determining safety and efficacy. Animal models are important to determine for conventional safety and efficacy. The SCID mice transplantation model (small animal) allowed us to investigate how EVPOME behaves in an in vivo environment and to determine the optimal stage of the EVPOME for clinical use. A large animal model is also required by the FDA prior to human clinical use; thus we developed a canine EVPOME fabrication protocol that was identical to our human EVPOME protocol. Our canine model enables us to evaluate the fate of EVPOME grafts in situ. Furthermore, the guidelines of CBER require us to demonstrate “dose and potency” of cell-based products, as is seen with drugs. Dose and potency appear to be representative of viable cell numbers and relevant biological function/activity of EVPOME, which provides a quantitative measurement of product quality. These quantitative measurements are challenging and specific for each cell-based product and need to be addressed.

IL‐6 INDUCES KERATIN EXPRESSION IN INTESTINAL EPITHELIAL CELLS: POTENTIAL ROLE OF KERATIN‐8 IN IL‐6 INDUCED BARRIER FUNCTION ALTERATIONS

The regulation and function of keratin in the intestinal epithelia is largely unknown. In this study we addressed the role and regulation of K8 and K18 expression by IL-6. Caco2-BBE cell line and IL-6 null mice were used to study the effect of IL-6 on keratin expression. Keratin expression was studied by Northern blot, Western blot and confocal microscopy. Paracellular permeability was assessed by apical-to-basal transport of a FITC dextran probe (FD-4). K8 was silenced using siRNA approach. IL-6 significantly upregulated mRNA and protein levels of K8 and K18. Confocal microscopy showed a reticular pattern of intracellular keratin localized to the sub-apical region after IL-6 treatment. IL-6 also induced serine phosphorylation of K8. IL-6 decreased paracellular flux of FD-4 compared to vehicle treated monolayer. K8 silencing abolished the decrease in paracellular permeability induced by IL-6. Interestingly, IL-6−/− mice showed decreased baseline levels of K8/K18 expression. Administration of dextran sodium sulfate (DSS) significantly increased intestinal permeability in IL-6−/− mice compared to WT mice given DSS. Collectively, our data demonstrate that IL-6 regulates the colonic expression of K8 and K18 and K8/K18 mediates barrier protection by IL-6 under conditions where intestinal barrier is compromised. Thus our data uncover a novel function of these abundant cytoskeletal proteins which may have implications in intestinal disorders such as inflammatory bowel disease wherein barrier dysfunction underlies the inflammatory response.

Interleukin-6 Induces Keratin Expression in Intestinal Epithelial Cells: POTENTIAL ROLE OF KERATIN-8 IN INTERLEUKIN-6-INDUCED BARRIER FUNCTION ALTERATIONS

Keratin 8 (K8) and keratin-18 (K18) are the major intermediate filament proteins in the intestinal epithelia. The regulation and function of keratin in the intestinal epithelia is largely unknown. In this study we addressed the role and regulation of K8 and K18 expression by interleukin 6 (IL-6). Caco2-BBE cell line and IL-6 null mice were used to study the effect of IL-6 on keratin expression. Keratin expression was studied by Northern blot, Western blot, and confocal microscopy. Paracellular permeability was assessed by apical-to-basal transport of a fluorescein isothiocyanate dextran probe (FD-4). K8 was silenced using the small interfering RNA approach. IL-6 significantly up-regulated mRNA and protein levels of K8 and K18. Confocal microscopy showed a reticular pattern of intracellular keratin localized to the subapical region after IL-6 treatment. IL-6 also induced serine phosphorylation of K8. IL-6 decreased paracellular flux of FD-4 compared with vehicle-treated monolayers. K8 silencing abolished the decrease in paracellular permeability induced by IL-6. Administration of dextran sodium sulfate (DSS) significantly increased intestinal permeability in IL-6-/- mice compared with wild type mice given DSS. Collectively, our data demonstrate that IL-6 regulates the colonic expression of K8 and K18, and K8/K18 mediates barrier protection by IL-6 under conditions where intestinal barrier is compromised. Thus, our data uncover a novel function of these abundant cytoskeletal proteins, which may have implications in intestinal disorders such as inflammatory bowel disease wherein barrier dysfunction underlies the inflammatory response.

The cutaneous non-neuronal cholinergic system and smoking related dermatoses: Studies of the psoriasis variant palmoplantar pustulosis

Palmoplantar pustulosis (PPP) is probably the inflammatory skin disease most strongly associated to smoking. The disease is common in middle-aged, smoking women, and is chronic, sometimes disabling and characterized by pustules, erythema and scaling on the soles and palms. It is often treatment-resistant. PPP patients have a co-morbidity with an increased risk of autoimmune thyroid disease, celiac disease/gluten intolerance, abnormal calcium homeostasis, diabetes type 2, and depression. The sweat gland apparatus is involved in the pathogenesis of PPP since a) the normal structure of the acrosyringium is abolished so the keratin pattern differs to that in normal palmar skin; b) granulocytes migrate outwards in the acrosyringium forming the pustule in the stratum corneum. Acetylcholine (ACh) is the main inducer of sweating. With immunohistochemistry the ACh synthesizing enzyme choline acetyltransferase (ChAT) and the ACh-degrading enzyme acetylcholinesterase (AChE) were found to be strongly expressed in the gland and duct as were the α-3 and α-7 nicotinic acetylcholine receptors (nAChRs). Smoking influenced the staining intensity of the enzymes and the α-3 nAChR in healthy subjects. In involved PPP skin there was a massive infiltration of granulocytes expressing ChAT and α-3 nAChR, and mast cells expressing AChE indicating a role for acetylcholine in inflammation. Cessation of smoking resulted in fewer pustules, and less scaling and erythema. The mechanisms for the effect of nicotine/smoking in PPP are still unknown but nicotine may lead to enhanced inflammation in consideration of the properties of the sweat duct and/or nicotine might facilitate autoimmune reactions.

Histological microstructure of the claws of the African clawed frog, Xenopus laevis (Anura: Pipidae): implications for the evolution of claws in tetrapods

Claws are consistent components of amniote anatomy and may thus be implicated in the success of the amniote invasion of land. However, the evolutionary origin of these structures in tetrapods is unclear. Claws are present in certain extant non-amniotes, such as Xenopus laevis, the African clawed frog. The histology of the soft tissue component of the claws of X. laevis is described and compared with the amniote condition in order to gain new information on the question of homology of claws in these two groups based on patterns of keratinization. The X. laevis claw sheath is composed of a localized thickening of the corneous region of the epidermis that envelops the terminal phalanx. Noted differences between the non-cornified layers of the epidermis of the claw and non-claw region are the overall grainier appearance of the cells and an increased abundance of desmosomes in the intermediate spinosus cells. The biochemical identity of the sheath keratin(s) is inferred to be different from that of non-claw region epidermis, based on histological differences and differences in stain affinity between the two regions. The microstructure of the frog claw differs from that of amniotes in several respects, including the lack of a specified zone of growth near the base of the claw. Amphibians and amniotes, therefore, have very different patterns of claw sheath growth. Observations do not support homology of claws on a structural level in these two groups; however, further experimental work may confirm a conserved pattern of cornification in these structures in tetrapods.

Morphofunctional Evidence of Changes in Principal and Mitochondria-Rich Cells in the Epidermis of the Frog Rana kl. esculenta Living in a Polluted Habitat

The epidermis of vertebrates is the body's principal barrier against environment and its possible contaminants. The presence of keratins, as well as specific detoxifying molecules or enzyme activities, in the various epidermis layers is believed to be involved in providing protection from harmful environmental influences. Anuran integument is poorly hornified and thus permeable to some endogenous and exogenous compounds and thus serves as a good bioindicator of overall environmental conditions. In the present investigation, we studied the epidermis of Rana kl. esculenta adult specimens collected at two different rice fields, relatively unpolluted and heavily polluted, respectively. Environmental pollution was assayed by chemical analysis performed on both sediments and animals. We evaluated the structural aspects of the epidermis at both light and electron microscopy levels and the pattern of keratinization by immunohistochemistry. Furthermore, we studied the activities of some enzymes (acid and alkaline phosphatase, nitric oxide synthase-related nicotinamide adenine dinucleotide phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, catalase, nonspecific esterases, and succinic dehydrogenase) involved mainly in membrane transport, xenobiotics, and oxidative metabolism. Compared with controls, in polluted animals we found the following results: (1) an increase in pollutant levels (i.e., cadmium, mercury, and lead); (2) less keratinized superficial cells in the epidermis; and (3) changes in most enzyme activities in keratinocytes and mitochondria-rich cells (particularly glucose-6-phosphate dehydrogenase and esterases, both important to counteract oxidative and toxic stress). Taken as a whole, the present data indicate the morphofunctional plasticity of the frog epidermis in response to environmental contamination.

Necrolytic migratory erythema without glucagonoma in a patient with short bowel syndrome

Necrolytic migratory erythema (NME) is an uncommon inflammatory dermatosis with a distinctive clinical and histological appearance. It shows irregular erythema, bullae, erosion, crusts and pigmentation. While it is typically associated with glucagonoma, some cases of NME without glucagonoma have been reported. Herein, we report a case of necrolytic migratory erythema associated with malabsorption 30 years after ileocolectomy. She presented erosive erythema with scale or partly flaccid bullae on her intergluteal cleft, buttock and extremities. Her laboratory data revealed essential amino acid deficiency and a slightly decreased serum zinc level, while her plasma glucagon level was low. With diagnosis of non-glucagonoma-associated NME with malabsorption due to short-bowel syndrome, she was treated and improved by i.v. amino acid supplement. Histological findings of NME include necrotic changes of keratinocytes in the upper epidermis, proliferation of those in the lower epidermis and inflammatory cell infiltration of upper dermis. We also examined the expression pattern of epidermal keratins (K6, K10) and Ki-67, one of the markers of proliferative activity, to assess the proliferation and differentiation of keratinocytes in a NME lesion by immunostaining. The findings with these immunostainings support the characteristics of HE-staining, and suggest hyponutrition may induce changing differentiation/proliferation of keratinocytes.

Altered phenotype of cultured urothelial and other stratified epithelial cells: implications for wound healing

The differentiation of cultured stratified epithelial cells can deviate significantly from that of normal epithelium, leading to suggestions that cultured cells undergo abnormal differentiation, or a truncated differentiation. Thus cultured epidermal and corneal epithelial cells stop synthesizing their tissue-specific keratin pair K1/K10 and K3/K12, respectively. The replacement of these keratins in the suprabasal compartment by K6/K16 keratins that are made by all stratified squamous epithelia during hyperplasia rules out a truncated differentiation. Importantly, the keratin pattern of in vivo corneal epithelium undergoing wound repair mimics that of cultured rabbit corneal epithelial cells. Although cultured urothelial cells continue to synthesize uroplakins, which normally form two-dimensional crystalline urothelial plaques covering almost the entire apical urothelial surface, these proteins do not assemble into crystals in cultured cells. Cultured epithelial cells can, however, rapidly regain normal differentiation on the removal of mitogenic stimuli, the use of a suitable extracellular matrix, or the transplantation of the cells to an in vivo, nonmitogenic environment. These data suggest that cultured epithelial cells adopt altered differentiation patterns mimicking in vivo regenerating or hyperplastic epithelia. Blocking the synthesis of tissue-specific differentiation products, such as the K1 and K10 keratins designed to form extensive disulfide cross-links in cornified cells, or the assembly of uroplakin plaques allows epithelial cells to better migrate and proliferate, activities that are of overriding importance during wound repair. Cultured urothelial and other stratified epithelial cells provide excellent models for studying the regulation of the synthesis and assembly of differentiation products, a key cellular process during epithelial wound repair.

Association of Shh and Ptc with keratin localization in the initiation of the formation of circumvallate papilla and von Ebner’s gland

The development of gustatory papillae in mammalian embryos requires the coordination of a series of morphological events, such as proliferation, differentiation and innervation. In mice, the circumvallate papilla (CVP) is a specialized structure that develops in a characteristic spatial and temporal pattern in the posterior region of the tongue dorsal surface. The distinct expression patterns of Shh and Ptc, which play important roles in the development of other epithelial appendages, have been localized in the trench wall that gives rise to von Ebner's gland (VEG). To define the cellular mechanisms responsible for morphogenesis and differentiation during early development of CVP and VEG, the localization patterns of keratins (cytokeratins) K7, K8, K18, K19, K14 and connexin-43, which are dependent on Shh expression in other developmental systems, have been examined in detail. The distinct localization of keratins K7, K8, K18, K19, K14 and connexin-43 in the epithelium giving rise to the CVP and VEG suggests that cytodifferentiation is established prior to morphological changes. Interestingly, the localization of proliferating cell nuclear antigen, a marker for cell proliferation, is similar to that of Shh. An understanding of the regulatory roles of cell-cell interactions and signalling molecules in orchestrating a mutual network will bring us nearer to defining the molecular and cellular mechanisms underlying morphogenesis in mammalian taste bud development.

Expression of Keratin 12 and Maturation of Corneal Epithelium during Development and Postnatal Growth

To determine the kinetics of corneal epithelial maturation during embryonic development and postnatal growth. Expression patterns of keratin (K)12 and K14 were determined in mouse embryos (embryonic days [E]15.5-19.5), corneas of postnatal day (P)0 to 10 months, and healing corneas after epithelial debridement in P30 and P90 mice. The expression of alkaline phosphatase (AP) was determined during postnatal growth and healing of epithelial debridement of Krt12(Cre/Cre)/ZAP bitransgenic mice. During embryonic development, K12 expression by corneal peridermal epithelium commenced at E15.5. In the period from E15.5 to P10, the expression of K12 was restricted to the suprabasal and/or superficial cells of the corneal epithelium, whereas the K14 expression was restricted to the basal cells. After P30, K12 expression was sporadically detected in the basal corneal epithelium, and the number of K12-positive basal cells increased as the mice grew older. The number of K14-positive cells that coexpressed K12 increased with age and reached a plateau after P180. Healing of the debrided epithelium facilitated the increase in K14-positive cells that coexpressed K12. Many basal cells of Krt12(Cre/Cre)/ZAP mice remained undifferentiated and expressed LacZ at P15, and they then differentiated to express Cre, which leads to excision of LacZ and AP expression. In the mouse, the corneal epithelium does not become fully mature until 3 to 6 months after birth, in that a significant number of corneal basal epithelial cells of young mice (<P30), which derive from embryonic surface ectoderm remain undifferentiated and serve as corneal epithelial progenitor cells. These progenitor cells may have some stem cell characteristics.

P63 protein is essential for the embryonic development of vibrissae and teeth

Development of skin appendages strongly depends on epithelial–mesenchymal interactions. One of the genes involved in this process is p63, a member of the p53 family of transcription factors, essential for ectodermal development, as elucidated by the phenotype of p63 knock-out mice. Surprisingly, no information on p63 expression in tooth and hair is yet available. Here, we show p63 expression during teeth and vibrissae morphogenesis in mouse embryos and we also show a correlation with the expression patterns of the epithelial marker keratin 5 and the proliferation marker Ki67. Our results show that p63 colocalizes with both K5 and Ki67 in the epithelium of developing vibrissae, while in teeth p63 is expressed, together with K5, in the undifferentiated ectoderm (enamel organ), and in ameloblasts, a subpopulation of differentiated ectodermal cells. Moreover, p63 expression in tooth seems not to be fully colocalized with nuclear Ki67 expression.