The keratin polypeptide patterns in heterotypically recombined epithelia of skin and mucosa of adult mouse

Estrogen modulates mesenchyme-epidermis interactions in the adult nipple

Maintenance of specialized epidermis requires signals from the underlying mesenchyme; however, the specific pathways involved remain to be identified. By recombining cells from the ventral skin of the K14-PTHrP transgenic mice [which overexpress parathyroid hormone-related protein (PTHrP) in their developing epidermis and mammary glands] with those from wild type, we show that transgenic stroma is sufficient to reprogram wild-type keratinocytes into nipple-like epidermis. To identify candidate nipple-specific signaling factors, we compared gene expression signatures of sorted Pdgfrα-positive ventral K14-PTHrP and wild-type fibroblasts, identifying differentially expressed transcripts that are involved in WNT, HGF, TGFβ, IGF, BMP, FGF and estrogen signaling. Considering that some of the growth factor pathways are targets for estrogen regulation, we examined the upstream role of this hormone in maintaining the nipple. Ablation of estrogen signaling through ovariectomy produced nipples with abnormally thin epidermis, and we identified TGFβ as a negatively regulated target of estrogen signaling. Estrogen treatment represses Tgfβ1 at the transcript and protein levels in K14-PTHrP fibroblasts in vitro, while ovariectomy increases Tgfb1 levels in K14-PTHrP ventral skin. Moreover, ectopic delivery of Tgfβ1 protein into nipple connective tissue reduced epidermal proliferation. Taken together, these results show that specialized nipple epidermis is maintained by estrogen-induced repression of TGFβ signaling in the local fibroblasts.

Biomarkers of Alzheimer's disease risk in peripheral tissues; focus on buccal cells

Alzheimer's disease (AD) is a progressive degenerative disorder of the brain and is the most common form of dementia. To-date no simple, inexpensive and minimally invasive procedure is available to confirm with certainty the early diagnosis of AD prior to the manifestations of symptoms characteristic of the disease. Therefore, if population screening of individuals is to be performed, more suitable, easily accessible tissues would need to be used for a diagnostic test that would identify those who exhibit cellular pathology indicative of mild cognitive impairment (MCI) and AD risk so that they can be prioritized for primary prevention. This need for minimally invasive tests could be achieved by targeting surrogate tissues, since it is now well recognized that AD is not only a disorder restricted to pathology and biomarkers within the brain. Human buccal cells for instance are accessible in a minimally invasive manner, and exhibit cytological and nuclear morphologies that may be indicative of accelerated ageing or neurodegenerative disorders such as AD. However, to our knowledge there is no review available in the literature covering the biology of buccal cells and their applications in AD biomarker research. Therefore, the aim of this review is to summarize some of the main findings of biomarkers reported for AD in peripheral tissues, with a further focus on the rationale for the use of the buccal mucosa (BM) for biomarkers of AD and the evidence to date of changes exhibited in buccal cells with AD.

Regionalisation of the skin

The skin displays marked anatomical variation in thickness, colour and in the appendages that it carries. These regional distinctions arise in the embryo, likely founded on a combinatorial positional code of transcription factor expression. Throughout adult life, the skin's distinct anatomy is maintained through both cell autonomous epigenetic processes and by mesenchymal-epithelial induction. Despite the readily apparent anatomical differences in skin characteristics across the body, several fundamental questions regarding how such regional differences first arise and then persist are unresolved. However, it is clear that the skin's positional code is at the molecular level far more detailed than that discernible at the phenotypic level. This provides a latent reservoir of anatomical complexity ready to surface if perturbed by mutation, hormonal changes, ageing or experiment.

Gingiva as a source of stem cells with therapeutic potential

Postnatal connective tissues contain phenotypically heterogeneous cells populations that include distinct fibroblast subpopulations, pericytes, myofibroblasts, fibrocytes, and tissue-specific mesenchymal stem cells (MSCs). These cells play key roles in tissue development, maintenance, and repair and contribute to various pathologies. Depending on the origin of tissue, connective tissue cells, including MSCs, have different phenotypes. Understanding the identity and specific functions of these distinct tissue-specific cell populations may allow researchers to develop better treatment modalities for tissue regeneration and find novel approaches to prevent pathological conditions. Interestingly, MSCs from adult oral mucosal gingiva possess distinct characteristics, including neural crest origin, multipotent differentiation capacity, fetal-like phenotype, and potent immunomodulatory properties. These characteristics and an easy, relatively noninvasive access to gingival tissue, and fast tissue regeneration after tissue biopsy make gingiva an attractive target for cell isolation for therapeutic purposes aiming to promote tissue regeneration and fast, scar-free wound healing. The purpose of this review is to discuss the identity, phenotypical heterogeneity, and function of gingival MSCs and summarize what is currently known about their properties, role in scar-free healing, and their future therapeutic potential.

Influence of the mesenchymal cell source on oral epithelial development

The extent of the influence of mesenchymal tissue on epithelial development is still debated, and elucidation of epithelial-mesenchymal interactions should be of relevance for controlling normal as well as pathological growth and development. The aim of the present study was to elucidate the influence of the mesenchymal cell type on oral mucosa epithelial development in vitro, using tissue-engineering principles, by including three different sources for mesenchymal cell type, viz. oral mucosa, skin and cornea, each of them presenting a distinct type of epithelium in situ. We investigated epithelial-mesenchymal interactions, considering both morphological criteria and protein expression (filaggrin, keratin 10, keratin 12, keratin 13 and laminin 5). The results of the histology, immunohistochemistry and transmission electron microscopy of the three types of tissue-engineered constructs composed of mesenchymal cells of different sources (oral, dermal and corneal fibroblasts) and of the same oral epithelial cells showed that the mesenchymal cell source had a significant influence on the thickness and ultrastructure of the epithelium, but not on the differentiation of oral epithelial cells, which might be an intrinsic property of these cells due to their genetic programming.

Newly established cell lines from mouse oral epithelium regenerate teeth when combined with dental mesenchyme

The present study attempted to examine whether clonal cell lines of the oral epithelium can differentiate into ameloblasts and regenerate tooth when combined with dental germ mesenchyme. Clonal cell lines with a distinct morphology were established from the oral epithelium of p53-deficient fetal mice at embryonic day 18 (E18). The strain of mouse is shown to be a useful source for establishing clonal and immortalized cell lines from various tissues and at various stages of development. Tooth morphogenesis is almost completed and the oral epithelium is segregated from the dental epithelium at E18. In RT-PCR analysis of cell lines, mucosal epithelial markers (cytokeratin 14) were detected, but ameloblast markers such as amelogenin and ameloblastin were not detected when cells were cultured on plastic dish. They formed stratified epithelia and expressed a specific differentiation marker (CK13) in the upper layer when cultured on feeder layer or on collagen gel for 1–3 wk, demonstrating that they are of oral mucosa origin. Next, bioengineered tooth germs were prepared with cell lines and fetal molar mesenchymal tissues and implanted under kidney capsule for 2–3 wk. Five among six cell lines regenerated calcified structures as seen in natural tooth. Our results indicate that some oral epithelial cells at E18 possess the capability to differentiate into ameloblasts. Furthermore, cell lines established in the present study are useful models to study processes in tooth organogenesis and tooth regeneration.

Eyelid mucous membrane grafts: a histologic study of hard palate, nasal turbinate, and buccal mucosal grafts

PURPOSE

To histologically evaluate the outcome of mucous membrane grafts to the eyelid.

METHODS

Case series of 31 eyes from 24 patients who underwent transplantation of hard palate (25 eyes), buccal (1 eye), or nasal turbinate (5 eyes) mucosa to the posterior eyelid surface. These grafts were biopsied at 0.5 months to 84 months (mean, 20 months) postoperatively. They were examined with light microscopy and compared with either the donor mucosa from the same patient (2 patients) or the typical donor site histology (22 patients).

RESULTS

Graft biopsies revealed general epithelial morphology that was quite similar to the respective donor sites in virtually all cases. Six (25%) of 24 hard palate graft biopsies, which were obtained at 8 months to 49 months (mean, 22 months) postoperatively, displayed orthokeratosis alternating with parakeratosis, while 12 (50%) demonstrated parakeratosis alone, and another 6 (25%) showed adjacent regions of parakeratotic and nonkeratinized epithelium. No hard palate grafts showed complete absence of keratinization after transplantation. Other significant findings included loss of goblet cells in nasal turbinate grafts and few submucosal glands remaining in any specimen.

CONCLUSIONS

Full-thickness mucosal grafts typically maintain their native epithelial morphology following transplantation to the ocular surface. Submucosal glands usually do not survive transplantation, which could be the result of intentional thinning of the graft at the time of transplantation. Contrary to the opinion that hard palate graft epithelium usually undergoes metaplasia from keratinized to nonkeratinized within 6 months following transplantation to the eye, all hard palate grafts in this study remained orthokeratotic and/or parakeratotic.

Distinctive molecular composition of human gingival interdental papilla

BACKGROUND

Gingiva is composed of attached and marginal (free) gingiva and interdental papilla. Increasing esthetic demands in dentistry have created a need to restore all parts of the gingiva. However, the interdental papilla has limited regeneration potential compared to other parts of the gingiva. It also is more susceptible to gingival overgrowth, suggesting that it has distinct cellular and molecular properties from other parts of the gingiva. Very little is known about the possible differences in the molecular composition of different parts of the gingiva.

METHODS

We compared the expression of a set of key molecules in interdental papilla and marginal gingiva from seven healthy subjects by immunohistochemical staining.

RESULTS

In the interdental papilla, immunoreactivity for integrin alphavbeta6 and cytokeratin 19 in the oral epithelium was significantly higher than in marginal gingiva. Expression of type I procollagen, extra domain A (EDA) and extra domain B (EDB) fibronectin isoforms, tenascin-C, transforming growth factor-beta (TGF-beta), connective tissue growth factor (CTGF), and the signaling molecule son-of-sevenless (SOS)-1 also were increased in the interdental papilla. The expression of small leucine-rich proteoglycans decorin, biglycan, fibromodulin, and lumican in the interdental papilla was partially different from the marginal gingiva.

CONCLUSIONS

Molecular composition of the interdental papilla is distinct from marginal gingiva. Increased expression of molecules normally induced in wound healing (alphavbeta6 integrin, fibronectin-EDB and -EDA, tenascin-C, type I procollagen, TGF-beta, CTGF, and SOS-1) suggests that the cells in the interdental papilla are in an activated state and/or inherently display a specific phenotype resembling wound healing.

Identification of markers for nipple epidermis: changes in expression during pregnancy and lactation

In vertebrates, specific regions of skin crucial for interaction with and manipulation of elements in the environment are characterized by specialized epidermis. Regions of specialized epidermis show distinct patterns of cellular differentiation and express specific keratins that provide an increased ability to withstand mechanical strain. The nipple, which must endure the mechanical strain of nursing, is a type of specialized epidermis. The entire ventral skin of the keratin 14 promoter driven PTHrP mouse provides a model for nipple development. To identify novel markers for this specialized epidermis, we have used two-dimensional (2-D) gels, mass spectrometric protein identification, Western blotting and immunohistochemistry to compare intermediate filament preparations from the nipple-like K14-PTHrP ventral skin to that of wild-type littermates. We identified 64 spots on 2-D gels that were increased in expression in the nipple-like skin of the female K14-PTHrP mouse and 11 spots that were elevated in the wild type. Microsequencing suggested that K17 and epiplakin were among the proteins with the greatest increase in expression in the K14-PTHrP ventral skin. Using Western blots and immunohistochemistry, we evaluated the expression of these proteins as well as K6 in the wild-type nipple, K14-PTHrP ventral skin and wild-type ventral skin. In addition, we found that the expression of K6 was minimally changed in the pregnant and lactating nipple, but the expression of a previously identified marker, K2e, was reduced during lactation. Using a model of the mechanical strain induced by nursing, we found that K2e but not K6 expression was responsive to this condition. The identification of epidermal markers and their expression patterns will provide insight into the cellular differentiation patterns of the nipple and the underlying epidermal-mesenchymal interactions that direct this differentiation.

Keratin 2e: a marker for murine nipple epidermis

Mesenchyme-derived signals influence the unique keratinization and appendage formation programs in specialized skin regions. Interactions between primary mammary mesenchyme and epidermal cells result in the formation of the nipple; however, it is unclear whether this represents a site of regionally specialized epidermis. We profiled the ultrastructure and keratin expression of the murine nipple, and the ventral skin of the K14-parathyroid hormone-related protein (PTHrP) transgenic mouse, which models nipple formation. We found the murine nipple and ventral K14-PTHrP epidermis display expanded suprabasal and granular layers, as well as a thickened cornified layer compared to ventral skin of wild-type littermates. We also observed increased levels of filaggrin in extracts from the ventral epidermis of the K14-PTHrP mouse when compared to that of wild-type littermates. Keratin 2e, previously reported to be expressed in various specialized epidermal sites in the mouse, is expressed in the nipple and the ventral skin of the K14-PTHrP mouse. Keratinocytes grown from the ventral epidermis of the K14-PTHrP mouse or wild-type littermates exhibited identical expression of epidermal markers in vitro, suggesting that the modulated differentiation profile observed in the nipple or the ventral K14-PTHrP skin was dependent on interactions with fibroblasts. The lack of appendages, altered stratification pattern and expression of a specialized keratin suggests that the murine nipple is an example of regionally specialized epidermis.

Recapitulation of oral mucosal tissues in long-term organotypic culture

To test the influence of fibroblasts on epithelial morphology and expression of keratinocyte proteins and barrier lipids, we bioengineered homotypic and heterotypic oral mucosae and skin using cultured adult human cells. Fibroblasts were allowed to modify collagen type I gels for 2 weeks before keratinocytes were added. The organotypic cultures were then grown at the air-liquid interface for 4 weeks. In homotypic combinations, epithelial morphology and protein expression closely mimicked those in vivo. In heterotypic combinations, the morphology resembled that in vivo and keratinocytes expressed their typical markers, except when skin keratinocytes were recombined with alveolar fibroblasts; they expressed K19, K4, and K13, which is similar to oral mucosal epithelia rather than to the epidermis. Morphologically, the stratum corneum layers were typical for the epithelial tissues. Grafting the bioengineered cultures to the backs of Nude mice did not change the results, suggesting that our findings are not merely a culture phenomenon. Lipid profiles of the homotypic combinations mimicked the profiles found in the normal epithelial tissues, except that the engineered alveolar epithelium expressed more ceramide 2 than that in vivo. In the heterotypic combinations, keratinocytes appeared to control the lipid profile, except in the combination of skin keratinocytes with alveolar fibroblasts, wherein the ceramide profile appeared to be partly that of alveolar epithelium and partly that of epidermis. These results suggest that cultured adult fibroblasts and keratinocytes are sufficient to recapitulate graftable oral tissues, and, except for alveolar fibroblasts, the type of fibroblast had little influence on keratinocyte differentiation.

Acellular dermal matrix allografts to achieve increased attached gingiva. Part 2. A histological comparative study

BACKGROUND

In part 1 of this study, we compared the clinical efficacy of freeze-dried acellular dermal matrix (ADM) allograft in 6 patients with autogenous free gingival graft (FGG) in 6 patients for increasing the width of attached gingiva in the mandibular anterior area. The purpose of the present study was to histologically compare the microstructure of ADM and FGG treated sites from the same group.

METHODS

Biopsies were harvested from all 12 patients at 6 months postsurgery. The biopsies included the grafted sites with adjacent alveolar mucosa and gingiva propria and also donor palatal mucosa saved at the time of surgery. The 5 microm thick, neutral buffered formalin fixed, paraffin-embedded tissue sections were stained with hematoxylin and eosin (H&E), Masson's trichrome, and Verhoeff-van Gieson stains in order to investigate the density of collagen and elastic fibers. Additional sections were stained with periodic acid-Schiff (PAS) and Papanicolaou's stain to identify the presence of glycogen granules in the epithelial layer and to highlight the keratin layer respectively.

RESULTS

The unique appearance of ADM-derived tissue did not parallel any known oral mucosa. The connective tissue portion contained dense to extremely dense collagen fibers along with scattered elastic fibers. The demarcations between the ADM graft and the coronal gingiva as well as the apical alveolar mucosa were usually not very defined. A moderate to thin epithelial layer, with heterogeneous expression of keratinization and flat epithelium-connective tissue interface, covered the lamina propria. Both the thickness of the epithelium and the degree of keratinization decreased in apical direction, being mostly para- or orthokeratinized in the area close to gingiva and non-keratinized adjacent to the alveolar mucosa. In the FGG-treated sites, the density of collagen fibers was less than in ADM-derived tissue, palatal mucosa, and gingiva. Elastic fibers were very sparse, comparable to gingiva, but much less than in ADM-derived tissue. The epithelium was moderate, somewhat thinner but the shape of the rete ridges resembled that of palatal mucosa. Similar to gingiva epithelium, the epithelium of the FGG-treated area was relatively uniform in both thickness and keratinization, mostly para-keratinized with a well defined border to the non-keratinized alveolar mucosa. Underneath the FGG-alveolar mucosa junction, a scar band composed of extremely dense collagen fibers consistently existed.

CONCLUSIONS

The results of this 6-month histological evaluation suggest that: 1) the resultant tissue types of ADM grafts were similar to "scar" tissue; 2) the non-vital dermal matrix of ADM allograft lacked the capability of directing cyto-differentiation of the covering epithelium; 3) autogenous FGG-derived tissue was neither identical to donor palatal mucosa nor to adjacent gingiva propria; 4) the connective tissue of donor palatal mucosa only partially contributed to the differentiation of the epithelium covering the FGG-treated area; and 5) the epithelium/connective tissue microenvironment surrounding the recipient site influenced the epithelial differentiation of the graft; this may play a more critical role in ADM grafting than in the grafting of autogenous FGG.

Cultured human sole-derived keratinocyte grafts re-express site-specific differentiation after transplantation

Cultured epithelial autografts (CEA) derived from sole skin were transplanted to full-thickness wounds excised to muscle fascia over a variety of diverse body sites in 12 pediatric patients treated for acute burns or giant congenital nevi. The skin regenerated from the grafts was biopsied from 7 days to 6 years after grafting. The resultant epidermal phenotype was analyzed histologically and by immunohistochemical localization of keratin 9 (K9) as objective evidence of sole-type site-specific differentiation. Expression of K9 was also verified by one-dimensional gel electrophoresis of epidermal cytoskeletal extracts and K9 immunoblot analysis. Grafts prepared from epidermis of axilla; groin or foreskin and transplanted to wounds of comparable depth in an identical manner in the same patients served as controls of postgrafting differentiation. Biopsies of sole skin from amputation specimens from patients of comparable age served as normal positive controls, and biopsies of nonsole skin from patients of comparable age served as normal negative controls. As early as 2 weeks postgrafting, the histologic appearance of sole-derived CEA differed substantively from that of axilla- or groin-derived CEA controls and displayed a phenotype characteristic of sole skin with a thick compact stratum corneum, a thick stratum granulosum, and a distinct stratum lucidum. In sole-derived grafts rete ridges regenerated within 2 months postgrafting, whereas nonsole-derived grafts required 4-6 months for rete ridge regeneration. Once acquired, the sole skin phenotype was maintained long-term by all sole-derived CEA. In vitro, sole-derived keratinocytes synthesized little, if any, K9. However, within 7 days after grafting, K9 synthesis by multiple suprabasal keratinocytes was seen within the epidermis regenerated from sole-derived CEA. Protein of K9 appeared progressively more diffuse throughout the suprabasal layers, attaining a confluent pattern of expression comparable to normal controls of sole skin by 6 to 12 months postgrafting, and the confluent pattern of suprabasal K9 synthesis was maintained long-term. The results demonstrate that site-specific differentiation is an intrinsic property of postnatal human keratinocytes and can be expressed and maintained in a permissive environment in the absence of dermal tissue.

Differential expression of integrins and laminin-5 in normal oral epithelia

beta 1 and beta 4 integrins are receptors on epithelial cells mediating cell-extracellular matrix adhesion. Furthermore, alpha 2 beta 1 and alpha 3 beta 1 contribute to cell-cell adhesion. Laminin-5 in epithelial basement membranes (BMs) is a ligand for alpha 6 beta 4 and alpha 3 beta 1. Expression of different integrins and laminin-5 was studied in oral epithelium to characterize regional variations in these adhesion molecules. Monoclonal antibodies directed against alpha 2-alpha 6 beta 1/alpha 6 beta 4 and laminin-5 were examined in cryopreserved biopsies of normal mucosa by immunohistochemistry. Laminin-5 was expressed as a line along the BMs. The junctional epithelium showed a unique phenotype: Laminin-5 was detected in the internal BM at the tooth surface and in the external BM, where excessive laminin-5 was seen in the stroma. alpha 6 beta 4 was expressed in all cells of the junctional epithelium. Integrins alpha 4 beta 1 and alpha 5 beta 1 were not detected in the epithelia, whereas alpha 2 beta 1 and alpha 3 beta 1 showed differential expression. Epithelia with well-developed rete pegs and connective tissue papillae showed polarized alpha 3 beta 1 expression along the BM in the rete pegs, in contrast to negative expression at the tips of the connective tissue papillae. A variation in the suprabasal distribution of alpha 2 beta 1 and alpha 3 beta 1 was observed between epithelia from different regions. alpha 2 beta 1 and alpha 3 beta 1 were detected in basal/parabasal cells in keratinized epithelia, whereas there was increased suprabasal expression in nonkeratinized mucosa. These results indicate inhomogeneity in the basal cell population of oral squamous epithelia and differential expression of integrins, which may reflect differences in the underlying stroma. Laminin-5 deposits in the stroma underneath the junctional epithelium may indicate subclinical gingival inflammation.

Cytokeratin phenotypes at the dento-gingival junction in relative health and inflammation, in smokers and nonsmokers

OBJECTIVES

The cells of the junctional epithelium (JE) provide and maintain the epithelial attachment, and remain morphologically and phenotypically distinct from oral sulcular (OSE) and external oral epithelia (EOE), from which they may be regenerated de novo. Expression of cytokeratins (CK) in human epithelia has been shown to be highly site-specific, implying a functional role. The aims of this study were to differentiate between the cytokeratin profiles of JE, OSE, EOE and pocket epithelia (PE) in health and disease, in smokers and non-smokers.

MATERIALS AND METHODS

The cytokeratin profiles of 40 samples of healthy and clinically inflamed human gingival tissue taken from 15 smokers and 25 non-smokers were studied by immunocytochemistry. Cryostat sections of fresh frozen gingival tissues were stained with a panel of monoclonal antibodies (mAb) and visualised by a biotin-Streptavidin-peroxidase complex technique.

RESULTS

JE and PE expressed an identical range of cytokeratins irrespective of the inflammatory or smoking status, with the exception of CK4 expression, which tended to be increased in smokers. The OSE and EOE expressed non-cornifying and cornifying differentiation cytokeratins respectively, but in the presence of inflammation, both these epithelia showed increased expression of CK19 at a basal level in association with expression of one or more of the simple cytokeratins. JE/PE expressed CK17 in external layers only, approximating the tooth surface. All epithelia expressed CK6, 16 the markers of high cell turnover.

CONCLUSIONS

CK 19 was a consistent differentiation marker for JE and PE. Expression of CK8, 18 was enhanced by inflammation. CK4 expression increased in association with smoking. Markers of differentiation were not always co-expressed equally within a pair. Pairs were not always completely mutually exclusive with frequent co-localisation.

Epidermal differentiation and dermal changes in healing following treatment of surgical wounds with sheets of cultured allogeneic keratinocytes

AIMS

To establish the structural changes that occur in deep surgical wounds engrafted with allogeneic sheets, their time course and inter-relation.

METHODS

Deep surgical wounds following shave excision of tattoos (down to deep dermis/subcutaneous fat) were treated with sheets of sex mismatched allogeneic keratinocytes in 19 patients and then biopsied weekly until wound healing was complete. More superficial surgical wounds--that is, 20 standard skin graft donor sites, were biopsied at seven to 10 days (all healed) following application of keratinocyte allografts. All biopsy specimens were examined with a large panel of monoclonal antibodies to keratins, envelope proteins, basement membrane components, and to extracellular matrix components.

RESULTS

The hyperproliferative keratin pair K6/16 was expressed in all wounds, for up to six weeks in keratinocyte grafted deep wounds, and up to six months in split thickness skin grafted wounds.

CONCLUSIONS

Keratins 6 and 16 have not been detected in normal skin, although the relevant mRNA has. This raises the possibility of regulation at a post-transcriptional level allowing a rapid response to injury with cytoskeletal changes that may aid cell migration. This keratin pair offers the most sensitive marker for altered epidermis following wounding.

The nature of the epithelium in acquired cholesteatoma: Part 3--Cytokeratin patterns in aural epithelial and cholesteatoma cells grown in cell culture

The nature and origin of the epithelial layers in acquired cholesteatoma is still unclear. Although previous morphological studies comparing external meatal and cholesteatoma epithelium have shown no significant difference, bone resorption is generally much more severe with cholesteatoma than with chronic otitis media without cholesteatoma. It is possible that cholesteatoma epithelium has undergone transformation leading to its enhanced bone destroying role. In this study the cytokeratin patterns of aural and cholesteatoma epithelia grown in cell culture were compared using monoclonal antibodies. No significant difference in staining patterns were found suggesting that there has been no change in cell phenotype which maintains that of external auditory meatus epithelium. This study therefore supports the immigration theory of cholesteatoma genesis.

Transdifferentiation of embryonic and postnatal rabbit corneal epithelial cells

In order to study the determination of corneal epithelial cells, rabbit corneal epithelium of 12- to 24-day embryos, newborn and 12-day-old offspring were recombined with mouse embryo upper-lip or dorsal dermis. Epithelial differentiation was analyzed using immunohistology with corneal monospecific monoclonal antibody AK12 (anti-keratin K12). Recombinants involving 12-day embryo undifferentiated corneal ectoderm formed a typical epidermis with hair follicles after 10 days of culture on the chick chorioallantoic membrane. Central corneal epithelium from 23- to 24-day embryos and newborn, which express suprabasally both K3 and K12 keratins and basally the K12 keratin alone, when grown in association with trichogenic dermis first failed to produce K12 in its new forming basal layer and then stratified after 11 days of culture above a differentiating epidermis with hair buds. When the culture period was increased up to 21 days by grafting under the kidney capsule from athymic mice, even the central corneal epithelium of 12-day-old off-spring gave rise to a complete epidermis with emerging hairs. The vibrissal- or pelage-type of hairs was in conformity with the regional origin of the mouse dermis. The species origin of the epithelial cells of the recombinants was discriminated incontestably using the Hoechst staining of interphase nuclei. Thus, the rabbit corneal epithelial cells can transdifferentiate into epidermal keratinocytes and trichocytes at least until 12 days after birth, despite the fact that from the fifth postnatal day the cells of its basal layer express both the K3 and the K12 keratins, a keratin pair marker of corneal cell-type terminal differentiation.

Cytokeratin profile of the junctional epithelium in partially erupted teeth

This study uses cytokeratins (CK) as markers to investigate the phenotype of the junctional epithelium (JE) in partially erupted human teeth. The gingival samples, which were clinically healthy, were carefully dissected from the teeth. Cryostat sections were cut for histological staining, immunofluorescence microscopy and gel electrophoresis. Cytokeratins were extracted after microdissection. The basal and suprabasal epithelial cell markers, cytokeratins 4, 5, 13, 14 and 19 were detected with specific monoclonal antibodies. They showed that the junctional epithelium in erupting teeth has a complex topography. The cytokeratin immunohistochemical profile distinguished between the primary junctional epithelium (CK 5, 14 and 19 in basal and suprabasal cells and CK 13 faintly stained throughout the suprabasal layers) and the adjacent epithelium that had the same cytokeratin profile as the sulcular epithelium (CK 5, 14 and 19 in basal cells and CK 4 and 13 intensively stained in the suprabasal cells). Extraction, two-dimensional electrophoresis and western blotting showed that this transitional JE during eruption also contained CK 6, 16 and perhaps CK 4. Thus, the JE in erupting teeth shows patterns of CK distribution that are very similar to that of developing oral epithelia.

Immunohistochemical analysis of cells attached to teflon membranes following guided tissue regeneration

A wide panel of monoclonal antibodies to various keratins together with an anti-vimentin antibody to label mesenchymal cells were used to label cells attached to expanded polytetrafluorethylene (ePTFE) membranes removed 6 weeks postoperatively from 7 patients. All membranes demonstrated variable amounts of adherent tissue, within which vimentin-positive cells were detected. In 8 of the 18 samples, no epithelial cells were detected. Seven of the 18 samples demonstrated small groups of epithelial cells on both sides of the membranes, staining predominantly as basal cells. The remaining 3 samples were more densely populated by epithelium which expressed a diverse keratin profile. Thus, the membranes were successful in establishing mesenchymal cell proliferation, as evidenced by vimentin positivity, but did not totally exclude epithelium.

Integrin expression and differentiation in transformed human epidermal cells is regulated by fibroblasts

Normal human foreskin keratinocytes (HFKs) and transformed HFKs (FEPE1L-8 cells) generated by the introduction of cloned human papillomavirus type 16 sequences were compared for the expression and function of a family of adhesion receptors termed integrins. Initially, cells were examined in conventional monolayer cultures. FEPE1L-8s expressed integrins alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha 6 beta 4 and beta 1 at comparable levels to HFKs. Further, these receptors were fully functional in mediating specific interactions with exogenously supplied ligands. However, FEPE1L-8s exhibited decreased synthesis of a number of extracellular matrix components, including laminin, fibronectin and epiligrin, compared to normal HFKs, which may be an alternate mechanism for regulating adhesion. Subsequently, organotypic cultures (OCs), which provide a suitable in vitro model system for the ordered stratification and differentiation of keratinocytes, were used to study the regulation of integrins and various epidermal markers in normal and transformed cells. OCs consisted of keratinocytes plated on a collagen gel containing primary human fibroblasts, grown at an air-medium interface. Unlike normal HFKs, the transformed FEPE1L-8 cells exhibited (a) disorganized stratification and limited differentiation capacity, (b) invasion into the collagen gel, and (c) unregulated expression of alpha 3 beta 1 and alpha 2 beta 1, and under-expression of alpha 6 beta 4 integrins. Ordered stratification and spatial regulation of integrin expression could be induced in the FEPE1L-8s by substituting Swiss 3T3 fibroblasts in the collagen gel. Further data indicate that the human fibroblasts induce the transformed HFKs to invade into the collagen gel.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in cytokeratin expression during the development of the human oral mucosa

The changes in cytokeratin expression by the developing oral mucosa of 10 to 23-week-old human fetuses were studied by indirect immunofluorescence using a panel of 15 monoclonal antibodies. The lining and masticatory mucosae were incompletely differentiated in 10-wk fetuses, since they expressed identical patterns of cytokeratins (CK 4, 5, 8, 13, 18, 19 and probably CK 14, 16, 17) very similar to that of adult alveolar mucosa. The main difference was the presence of cytokeratins 8, 18 and 19 in embryonic tissues. Cytokeratins 1, 2, 10 and 11 began to appear in gingival and hard palate epithelium from wk 11, predicting the differentiation of the masticatory mucosa by wk 16. The patterns of cytokeratin expression in the 23-wk fetus in the lining and masticatory mucosae appear to be different. In lining mucosa, the only difference from the 10th wk is a decrease in cytokeratins 8, 18 and 19, whereas the pattern of cytokeratin expression in masticatory mucosa (CK 1, 2, 4, 5, 8, 10, 11, 13, 18, 19 and probably CK 14, 16 and 17) is now very near that of adult gingiva. This pattern appears, as in the adult, to be similar to that of the epidermis in the same period.

Structural features and sites of expression of a new murine 65 kD and 48 kD hair-related keratin pair, associated with a special type of parakeratotic epithelial differentiation

In the course of studies on local keratin phenotypes in the epidermis of the adult mouse, we have identified a new 65 kD and 48 kD keratin pair. In mouse skin, this keratin pair is only expressed in suprabasal cells of adult mouse tail scale epidermis which is characterized by the complete absence of a granular layer and the formation of a remarkably compact stratum corneum. A second site in which the 65 kD and 48 kD keratin pair is suprabasally expressed and whose morphology corresponds to that of tail scale epidermis is found in the posterior unit of the complex filiform papillae of mouse tongue. The causal relationship of the expression of the 65 kD and 48 kD keratins with this particular type of a non-pathological epithelial parakeratosis is emphasized by the suppression of the mRNA synthesis of the two keratins during retinoic acid mediated orthokeratotic conversion of tail scale epidermis. Apart from tail scale epidermis and the posterior unit of the filiform papillae, the 65 kD and 48 kD keratin pair is, however, also coexpressed with "hard" alpha keratins in suprabulbar cells of hair follicles and in suprabasal cells of the central core unit of the lingual filiform papillae. The non alpha-helical domains of the two new keratins are rich in cysteine and proline residues and lack the typical subdomains into which epithelial keratins of both types can be divided. This structural resemblance of the 65 kD and 48 kD keratins to "hard" alpha keratins is supported by comparative flexibility predictions for their non alpha-helical domains. Phylogenetic investigations then show that the 65 kD and 48 kD keratin pair has evolved together with hair keratins, but has diverged from these during evolution to constitute an independent branch of a pair of hair-related keratins. In view of this exceptional position of the 65 kD and 48 kD keratins within the keratin multigene family, their expression has apparently been adopted by rare anatomical sites in which an orthokeratinized stratum corneum would be too soft and a hard keratinized structure would be too rigid to meet the functional requirement of the respective epithelia.

Cytokeratin pattern of clinically intact and pathologically changed oral mucosa

The various cytokeratin polypeptides in oral epithelia are expressed in dependence on site and formation of a stratum corneum. Certain cytokeratins occur permanently and others occasionally. In fibrous hyperplasia and Lichen ruber planus, patterns of cytokeratins did not deviate significantly from normal. In some but not all cases of squamous cell carcinoma and leukoplakia studied, marked aberrations of pattern were characterized by (i) appearance of cytokeratin No. 19, (ii) somewhat more frequent occurrence of cytokeratins Nos. 8 and 18, (iii) proteolytic modifications of cytokeratins, and (iv) partial loss of a few site-specific cytokeratins. The aberrations may be taken as additional diagnostic criteria for differentiation between non-aggressive and potentially aggressive leukoplakic lesion, even if they are not correlated with the conventional histological grading of dysplasia.

Cell surface carbohydrates are markers of differentiation in human oral epithelium

Carbohydrates of the epithelial cell membrane are involved in cell-cell and cell-substrate interaction, and changes are seen in relationship to cell differentiation and neoplastic transformation. The terminal part of carbohydrate structures carried on oral epithelial cells often expresses antigens of the ABO and Lewis blood group systems. The expression of these antigens are in oral mucosa genetically regulated by the A, B, H, Lewis, and secretor genes with subsequent correspondence between the blood group antigens expressed on erythrocytes and on oral epithelial cells. Variation in expression of carbohydrates is also seen in relationship to terminal differentiation in that blood group antigens and their immediate precursor structures are sequentially expressed on cells during their pathway through the epithelium. Various organs and tissues differ in their expression of cell surface carbohydrates. In oral mucosa, a close relationship is seen between the type of tissue differentiation and expression of blood group antigen; keratinized, nonkeratinized, and junctional epithelium all show different patterns of carbohydrate expression.

Association between keratin staining patterns and the structural and functional aspects of palatine tonsil epithelium

The keratin composition of stratified squamous epithelia has a complex pattern, which varies in different regions and as a result of pathological developments. The exact factors responsible for the characteristic keratin composition in a given epithelium are unknown. However, the environment, including factors from the connective tissue, is known to influence epithelial morphology and keratin composition. We here report that the reticulated squamous epithelium of the crypts of palatine tonsils shows an extensive staining for keratins 5 and 19 in basal as well as suprabasal cells, in contrast to neighbouring non-reticulated crypt epithelium and the epithelium at the tonsillar surface, in which staining is restricted to basal cells. The reticulation of the crypt epithelium is thought to be initiated by infiltration of immune-related cells in a preexistent non-reticulated epithelium. The extensive staining for keratins 5 and 19 in reticulated crypt epithelium correlates with the presence of numerous immune system-related cells and marked expression of intercellular adhesion molecule-1 (ICAM-1), thought to be involved in inflammatory and immunological responses. The results suggest that the massive lymphocytic traffic in the reticulated crypt epithelium and the overall distinct immune environment are responsible for the unique keratin staining pattern observed.

Differentiation of mouse embryonic palatal epithelium in culture: selective cytokeratin expression distinguishes between oral, medial edge and nasal epithelial cells

During normal murine palatogenesis, regional specific differentiation of the epithelium results in three cell phenotypes: nasal (ciliated pseudostratified columnar cells), oral (stratified squamous cells) and medial edge (migratory, epithelio-mesenchymally transformed cells). We have developed a defined, serum-free, culture system which supports the growth and differentiation of isolated murine embryonic palatal epithelia in vitro. Using immunofluorescence microscopy, an established panel of antibodies was used to characterise the cytokeratin intermediate filament profile of palatal epithelial sheets at a precise developmental stage, following culture in serum-free medium with and without either transforming growth factor alpha (TGF alpha) or 10% donor calf serum (DCS). The morphologically discernable oral, medial edge and nasal phenotypes exhibited distinctive cytokeratin profiles, which remained consistent for all culture conditions, and which correlated with the known differentiation states of the epithelial types. The oral epithelia stained positively for cytokeratin 19 and cytokeratins characteristic of multilayered epithelia (1, 5, 14). Nasal epithelia stained similarly but in addition expressed the simple-epithelial cytokeratin pair, 8 and 18. Medial edge epithelia also expressed cytokeratins 1, 5 and 14 but with the exception of a few isolated cells there was no staining for cytokeratins 8 and 18. Cytokeratin 19 was absent specifically from the medial edge epithelial cells: this result may be related to the loss of cytokeratin expression observed during epithelial-mesenchymal transformations. By exhibiting a complexity of expression linked to differentiation state and independent of culture conditions, cytokeratins constitute useful markers of palatal epithelial differentiation in vitro as well as in vivo.

Current concepts of the role of fibroblasts and extracellular matrix in wound healing and their relevance to oral implantology

Control of tissue differentiation and modelling are discussed in the context of epithelial-mesenchymal interactions and oral implantology. An accumulating body of evidence points to functional heterogeneity of oral fibroblasts and the use of a cell density migration assay to characterize this is described. Present data indicate that oral mucosal fibroblasts exhibit fetal-like phenotypes except in their responses to peptide growth factors. The hypothesis that clonal expansion of fibroblast subsets plays a role in the development of malignancy and in inflammatory disorders is presented. Production of a newly identified migration-stimulating factor by oral fibroblasts is described along with the heterogeneous distribution of extracellular matrix in the oral mucosa. The development of techniques for extracellular matrix localization in hard tissue is discussed.

Immunohistochemical distribution of keratin proteins in human gingival heterotransplants in nude mice

Clinically healthy human gingivae from deciduous molar regions were transplanted to subcutaneous sites of nude mice (nu/nu NC). Transplants were harvested after posttransplantation periods of 5, 6, 7, 8.5, 10.5 and 12 weeks and examined histologically after staining with hematoxylin-eosin (H.E.), bisbenzimide, and a panel of mouse monoclonal anti-keratin antibodies in an indirect fluorescence technique. Central parts of transplants contained human connective tissue covered by human stratified squamous epithelium which were unkeratinized in 5- to 7-wk-old transplants and most frequently (75%) parakeratinized in 8.5-wk to 12-wk transplants. Comparison of keratin expression before and after transplantation revealed a progressive keratin reconstitution, i.e., keratin markers of basal/suprabasal cells preceded those of suprabasal/spinous cell layers and immunohistochemical markers of keratinization preceded routine histologically observed parakeratinization. Original keratin staining and essential features of histodifferentiation were reconstituted and maintained after 8.5 wk but graft recovery rate decreased drastically 12 wk after transplantation. This study shows that the human gingiva/nude mouse model is useful in experimental studies of the gingival keratin profile in the period 8.5 to 10.5 wk after transplantation.

Three distinct keratinocyte subtypes identified in human oral epithelium by their patterns of keratin expression in culture and in xenografts

We have characterized the cells that form the human oral epithelia by analyzing their patterns of keratin expression in culture and in transplants. Keratinocytes of all oral regions synthesized high levels of keratins K5/K14 and K6/K16,K17, as expressed by cells of all stratified squamous epithelia in culture. However, cells from different regions varied in their expression in culture of retinoid-inducible (K19 and K13) and simple epithelial (K7, K8 and K18) keratins. By these criteria, all oral cells could be classified as belonging to one of three intrinsically distinct subtypes: "keratinizing" (gingiva, hard palate), "typical nonkeratinizing" (inner cheek, floor of mouth, ventral tongue) and "special non-keratinizing" (soft palate), all of which differed from the epidermal keratinocyte subtype. Cells from fetal floor of mouth expressed a pattern of keratins in culture markedly different from that of adult floor of mouth cells but identical to that of the adult "special nonkeratinizing" subtype and similar to that of several oral squamous cell carcinoma lines. When cultures of oral keratinocytes were grafted to the dermis of nude mice, they formed stratified epithelial structures after 10 days. In some areas of the stratified structures, the basal layer recapitulated the K19 expression pattern of the oral region from which they had originated. Thus, regional differentiation of the oral epithelium is based on an intrinsic specialization of regional keratinocyte stem cells. Additionally, oral cell transformation either frequently involves reversion to the fetal keratin program or else oral cells that express this keratin program are especially susceptible to transformation.

Mesenchyme-mediated and endogenous regulation of growth and differentiation of human skin keratinocytes derived from different body sites

In culture, keratinocytes generally express aberrant growth and differentiation programs, which are largely normalized in cell transplants. In order to study the underlying regulatory phenomena and to distinguish between intrinsic properties and external factors, different in vitro and in vivo models have been applied using human keratinocytes from foreskin and trunk skin. When transplanted onto nude mice, keratinocytes reformed a regular epithelium with expression of the differentiation markers, keratins K1 and K10, involucrin and filaggrin. Tissue homeostasis improved in later transplants, as made apparent by coexpression and regular distribution of K1 and K10. Since this was achieved in transplants, whether in contact with mesenchyme or separated by collagen matrix, renormalization was obviously mediated by diffusible factors. In vitro, the host-mesenchymal influence could largely be mimicked by recombining organotypic cultures (keratinocytes on lifted collagen gels) with de-epidermized dermis, but tissue homeostasis was apparently not achieved. Comparing keratinocytes from trunk skin and foreskin, differences observed in situ persisted in isolated cells and reconstituted tissues. The hyperproliferative character of foreskin epidermis, with its less-pronounced stratum granulosum, was maintained in recombinant cultures and transplants along with the expression of keratin K13 (typical for foreskin in situ) irrespective of the type of mesenchyme. Thus, we could demonstrate with these model systems that: (a) the regulation of keratinocyte growth and differentiation is mesenchyme-dependent; (b) it is mediated by diffusible factors; but that (c) differences between epidermis of different body sites are also controlled by intrinsic programs.

New approaches and concepts in the study of differentiation of oral epithelia

Epithelial structural proteins, the keratins and keratin-associated proteins, are useful as markers of differentiation because their expression is both region-specific and differentiation-specific. In general, basal cells in all stratified oral epithelia express similar keratins, while the suprabasal cells express a specific set of markers indicating commitment to a distinct program of differentiation. Critical factors in the regulation of epithelial protein expression are now under investigation. The promoter regions of keratin genes are being characterized to determine what sequences within the genes are responsible for differential expression. One important extracellular factor that influences epithelial protein expression is retinol (vitamin A), which exerts its effects via a group of nuclear receptor proteins that may also be expressed in a region-specific manner. These molecular biological approaches enhance our understanding of the mechanisms regulating differentiation of oral epithelia and its regional complexity.

Identification of murine type I keratin 9 (73 kDa) and its immunolocalization in neonatal and adult mouse foot sole epidermis

The foot sole epidermis of the fore and hind feet of the adult mouse contains an acidic (type I) mRNA-encoded 73-kDa keratin polypeptide which cannot be detected in any other skin site of the mouse integument. Western blot analysis using an antibody specific for the 64-kDa keratin 9 of human and bovine callus-forming epidermis [A. C. Knapp et al. (1986) J. Cell Biol. 103, 657-667] demonstrates that the 73-kDa keratin represents the murine analog of keratin 9 of man and cow. Concomitant investigations in two related rodent species indicate that the size of this keratin varies more among species than that of any other orthologous keratin. Histological examination of adult mouse foot sole skin reveals an extremely thick and undulated epidermis covering the apical portion of the six footpads, whereas the epidermal-dermal junction of the lateral walls of these nodular protuberances as well as that of the remainder of the foot sole skin is essentially flat. If sections of adult foot sole skin are investigated by indirect immunofluorescence with the keratin 9-specific antibody, intense cytoplasmic staining is restricted to the apical rete pegs of the footpad epidermis in which virtually all suprabasal cells express keratin 9. However, we also observed keratin 9-negative cell columns ascending straight above the tips of the dermal papillae and separating the keratin 9-positive rete pegs from each other. At the transition from the strongly undulated apical epidermis to the flat epidermis of the lateral walls of the footpads, keratin 9-positive cells loose their coherence and gradually disappear toward the inter-footpad epidermis. This intimate relationship between the morphogenesis of epidermal ridges and inter-ridges and the expression of keratin 9 is also visible in foot sole epidermis of neonatal mice. Here we observed the appearance of keratin 9-positive suprabasal cells concomitant with the onset of pronounced folding of the apical footpad epidermis by about Day 3 after birth. Our findings confirm the view that the expression of keratin 9 is characteristic of a highly specialized pathway of epidermal differentiation. We propose a hypothesis for keratin expression in skin sites which are subject to pronounced mechanical wear and tear.

Retention of differentiated characteristics in human fetal keratinocytes in vitro

Many of the morphologic and biochemical changes that occur during human fetal skin development have been described, yet there has been little experimental analysis of the processes that regulate the development of human fetal skin. This is due in part to difficulties in culturing human fetal epidermal keratinocytes. We have successfully cultured fetal keratinocytes in two different in vitro systems; in a serum-free keratinocyte growth medium (KGM) on tissue culture plastic and cocultured with dermal fibroblasts as spheroidal aggregates. To characterize these fetal keratinocytes in vitro we have assessed their ability to express several markers of epidermal differentiation. Human fetal keratinocytes grown on plastic in KGM stratify and express some of the components of the differentiated epidermis, such as involucrin and the high molecular weight keratins. However, these keratinocytes co-express keratins and vimentin and do not form a structured basement membrane. More characteristics of fetal skin are preserved in mixed aggregates of epidermal keratinocytes and dermal fibroblasts, including epidermal stratification, synthesis of basement membrane components, tissue-specific expression of intermediate filaments, involucrin, and expression of high molecular weight keratins. The maintenance of human fetal epidermal keratinocytes in these two in vitro systems and their ability to express many differentiated characteristics suggests that these cultures will be valuable for studies of the molecular mechanisms that regulate the regionally specific differentiation of the human fetal epidermis.

Altered keratin expression in buccal mucosal squamous cell carcinoma

Cytokeratin pattern was analyzed in 14 moderately differentiated and 12 well-differentiated squamous cell carcinomas of buccal mucosa by SDS-PAGE, immunoblotting and two dimensional electrophoresis. These were compared with patterns of normal buccal mucosa and surrounding areas whenever possible. Normal buccal mucosa expresses keratin No. 4 (59Kd), 5 (58Kd), 13 (54Kd) and 14 (50Kd). Keratin No. 4 (59Kd) and 14 (50Kd) were expressed by 20 of 26 tumors studied, while many of the tumors did not express keratins No. 5 (58Kd) and 13 (54Kd). Keratin No. 1 (67Kd) and 16 (48Kd) were aberrantly expressed by 9 well-differentiated tumors. Keratin No. 17 (46Kd) and 18 (45Kd) were expressed by 10 and 8 tumors of 14 moderately differentiated tumors. Six tumors which showed involvement of alveolar mucosa, expressed some keratins expressed by its normal counterpart. Their altered expression was consistent with the differentiation pattern as stated earlier. Non-expression of keratins 5 and 13 seems to be the result of malignant transformation and is seen in the majority of tumors, while appearance of aberrant keratins seems to be related more to the degree of differentiation of the tumor.

Glucose metabolism and protein synthesis in stratified squamous epithelia from young and old mice

Glucose metabolism in regionally distinct epidermis and oral epithelia of young adult and aged mice was studied using 5-3H glucose and differentially labelled 14C-glucose. The results obtained with 3H-glucose indicate there is active utilization of glucose by all the epithelia examined. However, an enhanced utilization of glucose was observed in old ear epidermis when compared to that in young mice. The measurements of respiratory 14CO2 in the young and old epidermis indicated that aerobic glycolysis was significantly greater in ear epidermis and buccal epithelium from old than from young mice. Pentose phosphate activity was significantly reduced in palate epithelium from old animals when compared with that of young animals. Incorporation of radioactively labelled leucine and histidine revealed some regional differences between the epithelia examined. However, no age-associated differences were observed in any of the tissues. It is concluded that the observed metabolic changes reflect regionally specific adaptations to local factors rather than representing a programmed biological event.

Effect of retinoid deficiency on keratin expression in mouse bladder

Twelve to sixteen weeks following treatment of CF-1 mice with a vitamin A-deficient diet, characteristic signs of retinoid deficiency including body wasting, poor hair coat, altered gait, decreased mobility, and xerophthalmia were observed. Histological examination of tissue sections from these mice revealed dramatic changes in the urinary tract epithelium. The normal transitional epithelium was replaced by a stratified squamous epithelium that resembled hyperproliferative epidermis. Using two-dimensional gel electrophoresis, a number of new proteins were found to be synthesized in vitamin A-deficient bladder when compared to tissue from control bladders. Using antikeratin antibodies in immunoblot experiments, we found that at least some of the newly synthesized proteins were keratins. These proteins, which comprise the intermediate filaments of the cytoskeleton, are known to be specific markers of epithelial differentiation. Of particular interest was the appearance of a Mr 67,000 basic and Mr 61,000 acidic keratin pair, characteristic of terminally differentiating murine epidermal cells. Unexpectedly, several other keratins, previously associated only with hyperproliferative epidermis, were also expressed in the tissue. These results demonstrate that vitamin A deficiency in the mouse leads to the appearance of a squamous metaplasia in the urinary tract epithelium that is characterized by the expression of distinct epidermal keratins.

Patterns of keratin-expression in rests of Malassez and periapical lesions

Using immunocytochemistry and a panel of monoclonal antibodies directed against various keratin polypeptides we examined specimens of normal periodontal ligament, periapical granulomas and inflammatory dental cysts. Epithelial elements with the appearance of rests of Malassez were identified in 6 specimens of normal periodontium and 10 periapical granulomas. Altered epithelium was present in 16 periapical granulomas and a lining epithelium in 10 inflammatory dental cysts. The patterns of binding of antibodies by these epithelia indicated that (a) keratin 19 was expressed by all epithelia, and (b) rests of Malassez also expressed keratin 5 but not large amounts of other keratins and (c) epithelial proliferation in periapical lesions was associated with increased expression of keratin 14, a marker of stratifying epithelia, new expression of keratins 4 and 13, differentiation markers for non-cornifying epithelia and variable, low levels of keratins 8 and 18, markers of simple epithelia. Proliferation of the epithelial rests of Malassez to form the lining of inflammatory dental cysts thus appears to be associated with a change from an unusual epithelial phenotype to that of a stratified non-cornifying epithelium in which some simple epithelial keratins are coexpressed.

Keratins of the human hair follicle: "hyperproliferative" keratins consistently expressed in outer root sheath cells in vivo and in vitro

Keratins produced by morphologically distinct compartments of the human hair folicle (hHF) were analysed and compared to those produced by cultured hHF and interfollicular keratinocytes. Five of the major keratins, the basic keratins nos. 5 and 6 (apparent mol. mass 60 and 58 kDa) and the acidic keratins nos. 14, 16, and 17 (51, 49 and 48 kDa), could be labelled in intact hHF and were found in all fractions of the outer root sheath (ORS). The other major keratins, which were not labelled under these conditions (basic-neutral hHbI and -II; 60-62 kDa and acidic hHaI and -II; 40-42 kDa) were associated with hair shaft (hHS) both in the follicle and, virtually unchanged, in the distal part of the hair. Another, previously undescribed, group of proteins with keratin-like properties exhibiting a broad pI-spectrum (basic to slightly acidic: hIC-I, -II, -III, 64-67 kDa; distinctly acidic: hIC-IV, about 54 kDa) was detected in isolated inner root sheath (IRS), in the cuticular material shed from denuded hHS, and also in nail plates. In our experiments only ORS cells grew readily in culture irrespective of their origin from peripheral (mesenchyme-adjacent) or more central ORS-cell layers. In contrast to keratinocytes from interfollicular epidermis (IFE) the cultured ORS cells expressed a keratin set virtually identical to that expressed in vivo. This set also closely resembled that expressed by IFE keratinocyte cultures. The identity of the respective keratins (nos. 5, 6, 14, 16, and 17) present in all these cells in vivo and in vitro was confirmed by tryptic peptide mapping. The data indicated that the microenvironment (in situ) directs the differentiation of ORS cells in a manner comparable to the way it is directed by conventional culture conditions, with consistent expression of the "basal" and "hyperproliferative" set of keratins. This, however, does not exclude the possibility that other types of environmentally induced response may occur, as seen for example during the reepithelialization of superficial skin wounds by ORS cells.

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.

An unusual type-II 70-kilodalton keratin protein of mouse epidermis exhibiting postnatal body-site specificity and sensitivity to hyperproliferation

Keratin extracts from the epidermis of adult mouse ears, footpads, and tail contain large amounts of a 70-kilodalton (kDa) protein which has not been detected in any other body site of the adult mouse or in the epidermis of neonatal mice. Two-dimensional immunoblotting using an antiserum which recognizes both type-I and type-II murine keratins revealed that the 70-kDa protein is indeed a keratin belonging to the type-II subfamily. Its postnatal induction occurs during the first 2 weeks after birth, being first observed in tail epidermis, then in footpad epidermis, and only rather late in ear epidermis. Although in vitro translation experiments with polyA+-RNA from adult tail and footpad epidermis consistently failed to reveal the 70-kDa protein among the translation products, we obtained evidence using a specific cDNA clone that, in vivo, the protein is encoded by a discrete mRNA. This clone, termed pke70, was isolated from a cDNA library of footpad epidermal mRNA. Homology comparisons with a variety of known keratin cDNAs indicated that pke70 contains sequence information for a type-II keratin that is substantially larger than the mouse 67-kDa keratin protein. Northern-blot analysis with a specific 3'-fragment of pke70 demonstrated a single 2.8 +/- 0.1 kb mRNA species exclusively in adult ear, footpad, and tail epidermis. In situ hybridization with the same fragment revealed the presence of the pke70-hybridizing mRNA in both basal and suprabasal cells of ear and footpad epidermis as well as in the orthokeratinizing parts of the tail epidermis; however in the epidermis covering the balls of the feet, labeling was restricted to suprabasal cells at the base of these nodular elevations. Continuous treatment of adult tail or ear epidermis with hyperplasiogenic agents, e.g., vitamin A acid and the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), leads to a gradual disappearance of the 70-kDa protein. We obtained evidence using in situ hybridization that the loss of the 70-kDa keratin is preceded by a specific suppression of the transcription of its putative mRNA in basal cells, whereas initially suprabasal cells are apparently still able to complete their original commitment. The particular properties of the 70-kDa keratin protein, i.e., its topological restriction, its postnatal and time-dependent acquisition, and its pronounced sensitivity to hyperplasiogenic stimuli, make this keratin subunit an especially suitable candidate for studies concerning the regulation of keratin expression and morphogenesis in general, as well as for studies of the factors that control its expression so specifically.

Connective tissue influences on the expression of epithelial cell-surface antigens

Adult mice were found to show regional variation in the epithelial expression of some molecules of the blood-group antigen series. To investigate connective tissue influences on such differences, heterotypic recombinants of epithelia and connective tissues from various regions were prepared and examined using monoclonal antibodies directed against bloodgroup antigens H and Ley. The results indicate that epithelia may maintain a preexisting regionally specific pattern following recombination but that, in some recombinant matches, the connective tissue is capable of signalling redirection of the pattern of expression towards that typical of the epithelium with which it is normally associated.

Differentiation-dependent expression of keratins in human oral epithelia

The polypeptide composition of epithelial keratins varies with the state of differentiation. The epithelia lining the human oral cavity show regional variations in their histology. In the present study, paired samples of nonkeratinized buccal epithelium and keratinized hard palate epithelium were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by immunoblots with monoclonal antibodies AE1, AE2, and AE3, and results were correlated with immunofluorescence staining of tissue sections of the same samples. Keratins from hard palate (Mr 67K, 63-65K, 58K, 56.5K, 56K, 50K, 48K) and epidermis (Mr 67K, 63-65K, 58K, 56.5K, 50K) were similar to each other but distinctly different from those of buccal epithelium (major bands of Mr 52K and 59K, minor bands of 50K and 58K). The immunoblot analysis further indicated the similarity of hard palate and epidermal keratins, in contrast to those of buccal epithelium. Each oral tissue expressed keratins of the type I (AE1, acidic) subfamily and type II (AE3, basic) subfamily. In tissue sections, the predominant staining pattern for nonkeratinized buccal epithelium was: AE1, positive in the basal layer; AE2, negative; AE3, positive in all layers. In contrast, the staining pattern for keratinized palatal epithelium was: AE1 and AE2, positive in the suprabasal layers; AE3, positive in all layers. Strong suprabasal AE1 staining in palate may be related to the presence of the 48K keratin. Some buccal samples showed an alternate staining pattern of spotty suprabasal staining with AE1 and AE2 which was correlated with the expression of the 56.5K and 63-67K keratins, as well as filaggrin. These results suggest differentiation-specific expression of the keratins and show immunologically detectable variation in the apparently normal differentiation pattern of nonkeratinized buccal epithelium.