Structural and functional relations between the connective tissue and epithelium of enamel organ and their role during enamel maturation

The morphological and possible functional interactions between the connective tissue and enamel organ cells were examined during the maturation phase of enamel formation, using immunohistochemical techniques. Decalcified mandibular sections (10 µm) including incisors were used from Wistar rats ages 10-12 weeks. Sections were incubated with one or two primary antibodies targeting cell cytoskeleton (vimentin, α-actin, α-tubulin), dendritic marker (OX6), gap junctions (cx-43), enzymes (nitric-oxide synthase (nos1) and cyclooxygenase (cox1)), and the ion transporters (Na+/H+ exchanger (NHE1) and Na+/Ca2+ exchanger (NCX)) for 24 h, before incubation with the appropriate conjugated fluorescent secondary antibodies. Sections were examined by fluorescence microscopy. Haematoxylin-eosin slides were also employed. Cellular heterogeneity and morphological modulations were identified within enamel organ cells and connective tissue covering suggesting complex cellular interactions and indicating a new functional concept and possible complementary role during enamel maturation. Also, some ion transportation activity, and nos1 and cox1 signalling pathways have been identified, indicating intercellular communication between these regions. A hypothesis is suggested, to explain the morphological modulation of ameloblasts and papillary cells during enamel maturation which functions to increase the transporting membrane surface area to accomplish faster and bulker ion transportation to achieve controlled pH and to direct Ca2+ towards enamel.

Copper impair autophagy on zebrafish (Danio rerio) gill epithelium

Copper (Cu) is an essential element for organism's metabolism, being controversially listed as a priority pollutant. Importantly, the toxicity of Cu has been linked to several cell death pathways. Thus, this study aimed to assess if macroautophagic pathways are triggered by Cu in zebrafish gill, the main target of waterborne pollutants. The electron microscopy findings indicated that Cu induced profound impacts on zebrafish gill structure and functions, being this tissue a biomarker sensitive enough to indicate early toxic effects. The findings also support a clear impairment of autophagy, througth the absence of phagossomes and the significant down-regulation mRNA transcript levels of microtubule-associated protein light chain 3 (LC3). The reduction of LC3 levels was often associated to an increase of apoptotic activation, indicating that the inhibition of macroautophagy triggers apoptosis in zebrafish gills. This study highlighted that the autophagic down-regulation might be affected through the activation of other cell death signaling pathway.

Curvature in the reproductive tract alters sperm-surface interactions

The fallopian tube is lined with a highly complex folded epithelium surrounding a lumen that progressively narrows. To study the influence of this labyrinthine complexity on sperm behavior, we use droplet microfluidics to create soft curved interfaces over a range of curvatures corresponding to the in vivo environment. We reveal a dynamic response mechanism in sperm, switching from a progressive surface-aligned motility mode at low curvatures (larger droplets), to an aggressive surface-attacking mode at high curvatures (smaller droplets of <50 µm-radius). We show that sperm in the attacking mode swim ~33% slower, spend 1.66-fold longer at the interface and have a 66% lower beating amplitude than in the progressive mode. These findings demonstrate that surface curvature within the fallopian tube alters sperm motion from a faster surface aligned locomotion in distal regions to a prolonged physical contact with the epithelium near the site of fertilization, the latter being known to promote capacitation and fertilization competence.

Histologic Study of the Esophagogastric Junction of Organ Donors Reveals Novel Glandular Structures in Normal Esophageal and Gastric Mucosae

INTRODUCTION

Whether cardiac mucosa at the esophagogastric junction is normal or metaplastic is controversial. Studies attempting to resolve this issue have been limited by the use of superficial pinch biopsies, abnormal esophagi resected typically because of cancer, or autopsy specimens in which tissue autolysis in the stomach obscures histologic findings.

METHODS

We performed histologic and immunohistochemical studies of the freshly fixed esophagus and stomach resected from 7 heart-beating, deceased organ donors with no history of esophageal or gastric disease and with minimal or no histologic evidence of esophagitis and gastritis.

RESULTS

All subjects had cardiac mucosa, consisting of a mixture of mucous and oxyntic glands with surface foveolar epithelium, at the esophagogastric junction. All also had unique structures we termed compact mucous glands (CMG), which were histologically and immunohistochemically identical to the mucous glands of cardiac mucosa, under esophageal squamous epithelium and, hitherto undescribed, in uninflamed oxyntic mucosa throughout the gastric fundus.

DISCUSSION

These findings support cardiac mucosa as a normal anatomic structure and do not support the hypothesis that cardiac mucosa is always metaplastic. However, they do support our novel hypothesis that in the setting of reflux esophagitis, reflux-induced damage to squamous epithelium exposes underlying CMG (which are likely more resistant to acid-peptic damage than squamous epithelium), and proliferation of these CMG as part of a wound-healing process to repair the acid-peptic damage could result in their expansion to the mucosal surface to be recognized as cardiac mucosa of a columnar-lined esophagus.

Epithelial folding determines the final shape of beetle horns

The elaborate ornaments and weapons of sexual selection, such as the vast array of horns observed in scarab beetles, are some of the most striking outcomes of evolution. How these novel traits have arisen, develop, and respond to condition is governed by a complex suite of interactions that require coordination between the environment, whole-animal signals, cell-cell signals, and within-cell signals. Endocrine factors, developmental patterning genes, and sex-specific gene expression have been shown to regulate beetle horn size, shape, and location, yet no overarching mechanism of horn shape has been described. Recent advances in microscopy and computational analyses combined with a functional genetic approach have revealed that patterning genes combined with intricate epithelial folding and movement are responsible for the final shape of a beetle head horn.

Epithelial organ shape is generated by patterned actomyosin contractility and maintained by the extracellular matrix

Epithelial sheets define organ architecture during development. Here, we employed an iterative multiscale computational modeling and quantitative experimental approach to decouple direct and indirect effects of actomyosin-generated forces, nuclear positioning, extracellular matrix, and cell-cell adhesion in shaping Drosophila wing imaginal discs. Basally generated actomyosin forces generate epithelial bending of the wing disc pouch. Surprisingly, acute pharmacological inhibition of ROCK-driven actomyosin contractility does not impact the maintenance of tissue height or curved shape. Computational simulations show that ECM tautness provides only a minor contribution to modulating tissue shape. Instead, passive ECM pre-strain serves to maintain the shape independent from actomyosin contractility. These results provide general insight into how the subcellular forces are generated and maintained within individual cells to induce tissue curvature. Thus, the results suggest an important design principle of separable contributions from ECM prestrain and actomyosin tension during epithelial organogenesis and homeostasis.

The regulation and maintenance of an organ’s shape is a major outstanding problem in developmental biology. An iterative approach combining multiscale computational modelling and quantitative experimental approach was used to decouple direct and indirect roles of subcellular mechanical forces, nuclear positioning, and extracellular matrix in shaping the major axis of the wing pouch during the larval stage in fruit flies, which serves as a prototypical system for investigating epithelial morphogenesis. The research findings in this paper demonstrate that subcellular mechanical forces can effectively generate the curved tissue profile, while extracellular matrix is necessary for preserving the bent shape even in the absence of subcellular mechanical forces once the shape is generated. The developed integrated multiscale modelling environment can be readily extended to generate and test hypothesized novel mechanisms of developmental dynamics of other systems, including organoids that consist of several cellular and extracellular matrix layers.

Uterine Luminal Epithelium as the Transient Gateway for Embryo Implantation

The uterine luminal epithelium (LE) is the first maternal contact for an implanting embryo. Intrauterine fluid resorption, cessation of LE proliferation and apoptosis, and LE structural changes are prerequisites for establishing transient uterine receptivity for embryo implantation. Vesicle trafficking in the LE and receptor-mediated paracrine and autocrine mechanisms are crucial both for LE preparation and LE communications with the embryo and stroma during the initiation of embryo implantation. This review mainly covers recent in vivo studies in LE of mouse models from 0.5 days post-coitus (D0.5) to ∼D4 20 h when the trophoblasts pass through the LE layer for embryo implantation. The review is organized into three interconnected sections: preimplantation LE preparation for embryo attachment, embryo-LE communications, and LE-stroma communications.

Differential lateral and basal tension drive folding of Drosophila wing discs through two distinct mechanisms

Epithelial folding transforms simple sheets of cells into complex three-dimensional tissues and organs during animal development. Epithelial folding has mainly been attributed to mechanical forces generated by an apically localized actomyosin network, however, contributions of forces generated at basal and lateral cell surfaces remain largely unknown. Here we show that a local decrease of basal tension and an increased lateral tension, but not apical constriction, drive the formation of two neighboring folds in developing Drosophila wing imaginal discs. Spatially defined reduction of extracellular matrix density results in local decrease of basal tension in the first fold; fluctuations in F-actin lead to increased lateral tension in the second fold. Simulations using a 3D vertex model show that the two distinct mechanisms can drive epithelial folding. Our combination of lateral and basal tension measurements with a mechanical tissue model reveals how simple modulations of surface and edge tension drive complex three-dimensional morphological changes.

Relationship Between Clinical and Histologic Periodontal Biotypes in Humans

Histologic and histomorphometric evaluations of gingival biopsy samples of patients presenting either a thick or a thin gingival biotype were performed. Full-thickness gingival biopsy samples were obtained and processed for histologic and histometric evaluations. Thickness of the keratinized mucosa or gingiva was found to be increased in the thick biotype. Specifically, the connective tissue layer was thicker with no change in epithelial thickness. In conclusion, gingival transparency appears to be an adequate, clinically useful method to classify the gingival biotype. The thin gingival biotype is manifested by reduced connective tissue thickness; therefore, biotype conversion or enhancement may be based on augmentation of the connective tissue portion of the gingival tissues.

A hybrid computational model to explore the topological characteristics of epithelial tissues

Epithelial tissues show a particular topology where cells resemble a polygon-like shape, but some biological processes can alter this tissue topology. During cell proliferation, mitotic cell dilation deforms the tissue and modifies the tissue topology. Additionally, cells are reorganized in the epithelial layer and these rearrangements also alter the polygon distribution. We present here a computer-based hybrid framework focused on the simulation of epithelial layer dynamics that combines discrete and continuum numerical models. In this framework, we consider topological and mechanical aspects of the epithelial tissue. Individual cells in the tissue are simulated by an off-lattice agent-based model, which keeps the information of each cell. In addition, we model the cell-cell interaction forces and the cell cycle. Otherwise, we simulate the passive mechanical behaviour of the cell monolayer using a material that approximates the mechanical properties of the cell. This continuum approach is solved by the finite element method, which uses a dynamic mesh generated by the triangulation of cell polygons. Forces generated by cell-cell interaction in the agent-based model are also applied on the finite element mesh. Cell movement in the agent-based model is driven by the displacements obtained from the deformed finite element mesh of the continuum mechanical approach. We successfully compare the results of our simulations with some experiments about the topology of proliferating epithelial tissues in Drosophila. Our framework is able to model the emergent behaviour of the cell monolayer that is due to local cell-cell interactions, which have a direct influence on the dynamics of the epithelial tissue.

Midgut epithelium in molting silkworm: A fine balance among cell growth, differentiation, and survival

The midgut of insects has attracted great attention as a system for studying intestinal stem cells (ISCs) as well as cell death-related processes, such as apoptosis and autophagy. Among insects, Lepidoptera represent a good model to analyze these cells and processes. In particular, larva-larva molting is an interesting developmental phase since the larva must deal with nutrient starvation and its organs are subjected to rearrangements due to proliferation and differentiation events. Several studies have analyzed ISCs in vitro and characterized key factors involved in their division and differentiation during molt. However, in vivo studies performed during larva-larva transition on these cells, and on the whole midgut epithelium, are fragmentary. In the present study, we analyzed the larval midgut epithelium of the silkworm, Bombyx mori, during larva-larva molting, focusing our attention on ISCs. Moreover, we investigated the metabolic changes that occur in the epithelium and evaluated the intervention of autophagy. Our data on ISCs proliferation and differentiation, autophagy activation, and metabolic and functional activities of the midgut cells shed light on the complexity of this organ during the molting phase.

Analysis of Cell Turnover in the Bronchiolar Epithelium Through the Normal Aging Process

PURPOSE

Aging is associated with changes in the lung that leads to a decrease in its function. Alterations in structure and function in the small airways are well recognized in chronic lung diseases. The aim of this study was the assessment of cell turnover in the bronchiolar epithelium of mouse through the normal aging process.

METHODS

Lungs from CD1 mice at the age of 2, 6, 12, 18, or 24 months were fixed in neutral-buffered formalin and paraffin-embedded. Proliferating cell nuclear antigen was examined by immunohistochemistry. Apoptosis was analyzed by in situ end-labeling of fragmented DNA. Epithelial dimensions were analyzed by morphometry.

RESULTS

The 2-month-old mice showed significantly higher number of proliferating cells when compared with mice at all other age groups. The number of apoptotic cells in mice at 24 months of age was significantly greater than in mice at all other age groups. Thus, the number of epithelial cells decreased as the age of the subject increased. We also found reductions in both area and height of the bronchiolar epithelium in mice at 18 and 24 months of age.

CONCLUSIONS

We found a decrease in the total number of epithelial cells in the aged mice, which was accompanied by a thinning of the epithelium. These changes reflect a dysregulated tissue regeneration process in the bronchiolar epithelium that might predispose to respiratory diseases in elderly subjects.

Quantitative Assessment of Mouse Mammary Gland Morphology Using Automated Digital Image Processing and TEB Detection

The assessment of rodent mammary gland morphology is largely used to study the molecular mechanisms driving breast development and to analyze the impact of various endocrine disruptors with putative pathological implications. In this work, we propose a methodology relying on fully automated digital image analysis methods including image processing and quantification of the whole ductal tree and of the terminal end buds as well. It allows to accurately and objectively measure both growth parameters and fine morphological glandular structures. Mammary gland elongation was characterized by 2 parameters: the length and the epithelial area of the ductal tree. Ductal tree fine structures were characterized by: 1) branch end-point density, 2) branching density, and 3) branch length distribution. The proposed methodology was compared with quantification methods classically used in the literature. This procedure can be transposed to several software and thus largely used by scientists studying rodent mammary gland morphology.

Models, measurement and inference in epithelial tissue dynamics

The majority of solid tumours arise in epithelia and therefore much research effort has gone into investigating the growth, renewal and regulation of these tissues. Here we review different mathematical and computational approaches that have been used to model epithelia. We compare different models and describe future challenges that need to be overcome in order to fully exploit new data which present, for the first time, the real possibility for detailed model validation and comparison.

Influence of embedded fibers and an epithelium layer on the glottal closure pattern in a physical vocal fold model

PURPOSE The purpose of this study was to explore the possible structural and material property features that may facilitate complete glottal closure in an otherwise isotropic physical vocal fold model. METHOD Seven vocal fold models with different structural features were used in this study. An isotropic model was used as the baseline model, and other models were modified from the baseline model by either embedding fibers aligned along the anterior-posterior direction in the body or cover layer, adding a stiffer outer layer simulating the epithelium layer, or a combination of the 2 features. Phonation tests were performed with both aerodynamic and acoustic measurements and high-speed imaging of vocal fold vibration. RESULTS Compared with the isotropic one-layer model, the presence of a stiffer epithelium layer led to complete glottal closure along the anterior-posterior direction and strong excitation of high-order harmonics in the resulting acoustic spectra. Similar improvements were observed with fibers embedded in the cover layer, but to a lesser degree. The presence of fibers in the body layer did not yield noticeable improvements in glottal closure or harmonic excitation. CONCLUSION This study shows that the presence of collagen and elastin fibers and the epithelium layer may play a critical role in achieving complete glottal closure.

Development of oral and extra-oral endosseous craniofacial implants by using a mesh structure for connective tissue attachment

Connective tissue attachment to a mesh structure incorporated on the surface of oral implants and extra-oral endosseous craniofacial implants (EOECI) was investigated. Two types of implants were prepared: TI and TI-Mesh. TI was composed of an upper and a lower component, both comprised of a titanium cylinder, which could be connected using a titanium screw. The composition of the TIMesh was similar, but the lower cylinder had a lateral groove that was covered with a titanium mesh. In animal experiments performed using rat calvaria, the lower component was first implanted and was left submerged for 3 weeks, then the upper component was mounted percutaneously. After an additional 2 weeks, each implant and the surrounding tissues were harvested and evaluated. Histological observations revealed collagen fibers originating from surrounding hypodermal tissues anchored to the mesh structures of the TI-Mesh whereas no such collagen fibers were observed around TI. Significantly greater values of the attachment strength, the thickness of the dermal tissue, the thickness of hypodermal tissue, and the attachment lengths were observed in TI-Mesh than those of TI. Thus connective tissue attachment with collagen fibers anchored to the mesh was achieved by incorporating mesh structures into the percutaneously placed implants.

Eriosema laurentii De Wild (Leguminosae) methanol extract has estrogenic properties and prevents menopausal symptoms in ovariectomized Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Eriosema laurentii De Wild (Leguminosae) is a medicinal plant used in West and Central Africa for different diseases. In Cameroon, this plant is used as a treatment for infertility, and various gynecological and menopausal complaints. However, despite this use as a natural remedy, the biological activity of Eriosema laurentii has not been studied until now.

AIM OF STUDY

In order to determine the potential use of this plant in gynecological conditions/disorders, we evaluated the estrogenic properties of a methanol extract of its aerial parts and its ability to prevent different menopausal health problems induced by bilateral oophorectomy.

MATERIAL AND METHODS

Two approaches were used. In vitro, recombinant yeast systems were applied, featuring either the respective human receptors (ERα, AR, and PR) or into chromosome III integrated human aryl hydrocarbon receptor (AhR) and the respective reporter plasmid. In vivo, the investigation was carried out using the 3 days uterotrophic assay and 9 weeks oral treatment in ovariectomized rats.

RESULTS

The results showed that the methanol extract of the aerial parts of Eriosema laurentii transactivated the estrogen receptor-α and displayed AhR agonistic activity but was neither androgenic nor progesteronic. In rats, the extract did not induce endometrium proliferation either in the 3-day or the 9-week treatment regimens, but induced vaginal stratification and cornification, prevented loss of femur bone mass, increased high density lipoprotein cholesterol (HDL-C), and reduced total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), TC/HDL-C ratio, LDL-C/HDL-C ratio and the atherogenic index of plasma (AIP).

CONCLUSION

These results suggest that the methanol extract of the aerial parts of Eriosema laurentii does not seem to have an undesirable influence on the endometrium but might prevent vaginal dryness and bone mass loss and improve the lipid profile.

Keratin 8 is required for the maintenance of architectural structure in thymus epithelium

Keratins (Ks), the intermediate filament (IF) proteins of epithelia, are coordinately expressed as pairs in a cell-lineage and differentiation manner. Cortical thymic epithelial cells (cTECs) predominantly express the simple epithelium keratin 8/18 (K8/K18) pair, whereas medullary thymic epithelial cells (mTECs) express the stratified epithelium K5/K14 pair, with TECs exhibiting K5 and K8 at the cortico-medullary junction in mature thymus. In the work reported here, we used wild-type (WT) and K8-knockout (K8-null) mice to address the contribution of K8/K18 IFs in the maintenance of the thymic epithelial structure. K8-null thymus maintained the differential cell segregation at the cortex versus the medulla observed in WT thymus, and the distribution of immature thymocytes at the cortex. The K8/K18 loss did not affect thymocyte development. However, it massively perturbed the TEC morphology both at the cortex and the medulla, along with a prominent depletion of cTECs. Such tissue alterations coincided with an increase in apoptosis and a reduced expression of Albatross (Fas-binding factor-1), also known for its capacity to bind K8/18 IFs. In addition, the K8/K18 loss affected the distribution of K5/K14-positive mTECs, but not their differentiation status. Together, the results indicate that K8/K18 IFs constitute key promoters of the thymic epithelium integrity.

Multicompartmental pharmacokinetic model of tenofovir delivery by a vaginal gel

Background

Trials of a vaginal Tenofovir gel for pre-exposure prophylaxis (PrEP) for HIV have given conflicting results. Knowledge of concentrations of Tenofovir and its active form Tenofovir diphosphate, at putative sites of anti-HIV functioning, is central to understanding trial outcomes and design of products and dosage regimens. Topical Tenofovir delivery to the vaginal environment is complex, multivariate and non-linear; determinants relate to drug, vehicle, dosage regimen, and environment. Experimental PK methods cannot yield mechanistic understanding of this process, and have uncontrolled variability in drug sampling. Mechanistic modeling of the process could help delineate its determinants, and be a tool in design and interpretation of products and trials.

Methods and Findings

We created a four-compartment mass transport model for Tenofovir delivery by a gel: gel, epithelium, stroma, blood. Transport was diffusion-driven in vaginal compartments; blood concentration was time-varying but homogeneous. Parameters for the model derived from in vitro and in vivo PK data, to which model predictions gave good agreement. Steep concentration gradients occurred in stroma ≤8 hours after gel release. Increasing epithelial thickness delayed initial TFV delivery to stroma and its decline: t_max increased but AUC at 24 hours was not significantly altered. At 24 and 48 hours, stromal concentrations were 6.3% and 0.2% of C_max. Concentrations in simulated biopsies overestimated stromal concentrations, as much as ∼5X, depending upon time of sampling, biopsy thickness and epithelial thickness.

Conclusions

There was reasonably good agreement of model predictions with clinical PK data. Conversion of TFV to TFV-DP was not included, but PK data suggest a linear relationship between them. Thus contrasts predicted by this model can inform design of gels and dosage regimens in clinical trials, and interpretation of PK data. This mass transport based approach can be extended to TFV conversion to TFV-DP, and to other drugs and dosage forms.

Apparent diffusion coefficients of normal uterus in premenopausal women with 3 T MRI

AIM

To investigate the apparent diffusion coefficient (ADC) values of the normal uterine cervical zonal structures (cervical epithelium, the junctional zone, and myometrium) during different phases of the menstrual cycle among premenopausal women in different age groups.

MATERIALS AND METHODS

Seventy healthy women, who were divided into three age groups (group A, 24 women in their twenties; group B, 23 women in their thirties; group C, 23 women in their forties), underwent 3 T magnetic resonance imaging (MRI) with T2-weighted and diffusion-weighted imaging (DWI) during the mid-proliferative and the mid-secretory phases.

RESULTS

The ADC values of each cervical zonal structure were significantly different from one another (p < 0.001). The ADC values of the epithelium and junctional zones were both lower during the mid-secretory phase than those during the mid-proliferative phase in each age group (p < 0.05). There were no significant differences in the ADC values of any of the cervical zones among the three age groups for a given phase (p > 0.05).

CONCLUSION

ADC values of normal cervical epithelium and the junctional zone change with different phases of the menstrual cycle, which should be taken into consideration when early cervical disease is detected, when monitoring treatment response, and differentiating early tumour recurrence.

Establishment of an in vitro system representing the chicken gut-associated lymphoid tissue

The bursa of Fabricius is critical for B cell development and differentiation in chick embryos. This study describes the production in vitro, from dissociated cell suspensions, of cellular agglomerates with functional similarities to the chicken bursa. Co-cultivation of epithelial and lymphoid cells obtained from embryos at the appropriate developmental stage regularly led to agglomerate formation within 48 hours. These agglomerates resembled bursal tissue in having lymphoid clusters overlaid by well organized epithelium. Whereas lymphocytes within agglomerates were predominantly Bu-1a⁺, a majority of those emigrating onto the supporting membrane were Bu-1a⁻ and IgM⁺. Both agglomerates and emigrant cells expressed activation-induced deaminase with levels increasing after 24 hours. Emigrating cells were actively proliferating at a rate in excess of both the starting cell population and the population of cells remaining in agglomerates. The potential usefulness of this system for investigating the response of bursal tissue to avian Newcastle disease virus (strain AF2240) was examined.

Reflectance model for acetowhite epithelium

Application of low concentration acetic acid solution to various types of human epithelia, in vivo, is a well-established technique for the visual identification of neoplastic and potential precancerous lesions, especially in the cervix. An acetic acid application produces a transient whitening effect associated with the aforementioned lesions (acetowhite effect). In this article, a simple semi-empirical tissue reflectance model is presented, which describes the acetowhite effect in terms of the tissue's optical properties and layered structure. The model successfully describes data available in the literature, explains basic characteristics of the acetowhite effect, and can serve as the basis for the development of more accurate and reliable noninvasive diagnostic methodologies for precancerous epithelial lesions.

High-resolution multiband polarization epithelial tissue imaging method by sparse representation and fusion

Multiband polarization epithelial tissue imaging is an effective tool to measure tissue's birefringence and structure for quantitative pathology analysis. To discriminate the pathology accurately, high-resolution multiband polarization images are essential. But it is difficult to acquire high-resolution polarization images because of the limitations of imaging systems. The polarization image calculation process can be regarded as image fusion with fixed rules, and multiband polarization images are intrinsically sparse. In this paper, we propose a novel high-resolution multiband polarization image calculation method by utilizing the sparse representation and image fusion method. The multiband images are first represented in the sparse domain and we further introduce total-variation-regularization terms into the sparse representation framework. Then, polarization parameter images are calculated by simultaneous fusion and reconstruction. Higher quality multiband polarization images can be obtained through additional regularization constraint in the fusion process. Extensive experiments validate that the proposed method achieves much better results than many state-of-the-art algorithms in terms of both peak signal-to-noise-ratio and visual perception.

ΔNp63 knockout mice reveal its indispensable role as a master regulator of epithelial development and differentiation

The transcription factor p63 is important in the development of the skin as p63-null mice exhibit striking defects in embryonic epidermal morphogenesis. Understanding the mechanisms that underlie this phenotype is complicated by the existence of multiple p63 isoforms, including TAp63 and ΔNp63. To investigate the role of ΔNp63 in epidermal morphogenesis we generated ΔNp63 knock-in mice in which the ΔNp63-specific exon is replaced by GFP. Homozygous ΔNp63(gfp/gfp) animals exhibit severe developmental anomalies including truncated forelimbs and the absence of hind limbs, largely phenocopying existing knockouts in which all p63 isoforms are deleted. ΔNp63-null animals show a poorly developed stratified epidermis comprising isolated clusters of disorganized epithelial cells. Despite the failure to develop a mature stratified epidermis, the patches of ΔNp63-null keratinocytes are able to stratify and undergo a program of terminal differentiation. However, we observe premature expression of markers associated with terminal differentiation, which is unique to ΔNp63-null animals and not evident in the skin of mice lacking all p63 isoforms. We posit that the dysregulated and accelerated keratinocyte differentiation phenotype is driven by significant alterations in the expression of key components of the Notch signaling pathway, some of which are direct transcriptional targets of ΔNp63 as demonstrated by ChIP experiments. The analysis of ΔNp63(gfp/gfp) knockout mice reaffirms the indispensable role of the ΔN isoform of p63 in epithelial biology and confirms that ΔNp63-null keratinocytes are capable of committing to an epidermal cell lineage, but are likely to suffer from diminished renewal capacity and an altered differentiation fate.

Fish geometry and electric organ discharge determine functional organization of the electrosensory epithelium

Active electroreception in Gymnotus omarorum is a sensory modality that perceives the changes that nearby objects cause in a self generated electric field. The field is emitted as repetitive stereotyped pulses that stimulate skin electroreceptors. Differently from mormyriformes electric fish, gymnotiformes have an electric organ distributed along a large portion of the body, which fires sequentially. As a consequence shape and amplitude of both, the electric field generated and the image of objects, change during the electric pulse. To study how G. omarorum constructs a perceptual representation, we developed a computational model that allows the determination of the self-generated field and the electric image. We verify and use the model as a tool to explore image formation in diverse experimental circumstances. We show how the electric images of objects change in shape as a function of time and position, relative to the fish's body. We propose a theoretical framework about the organization of the different perceptive tasks made by electroreception: 1) At the head region, where the electrosensory mosaic presents an electric fovea, the field polarizing nearby objects is coherent and collimated. This favors the high resolution sampling of images of small objects and perception of electric color. Besides, the high sensitivity of the fovea allows the detection and tracking of large faraway objects in rostral regions. 2) In the trunk and tail region a multiplicity of sources illuminate different regions of the object, allowing the characterization of the shape and position of a large object. In this region, electroreceptors are of a unique type and capacitive detection should be based in the pattern of the afferents response. 3) Far from the fish, active electroreception is not possible but the collimated field is suitable to be used for electrocommunication and detection of large objects at the sides and caudally.

Freshwater fish gill ion transport: August Krogh to morpholinos and microprobes

August Krogh proposed that freshwater fishes (and other freshwater animals) maintain body NaCl homoeostasis by extracting these ions from the environment via separate Na(+) /NH(4)(+) and Cl(-) /HCO(3)(-) exchangers in the gill epithelium. Subsequent data from other laboratories suggested that Na(+) uptake was more probably coupled to H(+) secretion via a vesicular proton pump (V-ATPase) electrically coupled to a Na(+) channel. However, despite uncertainty about electrochemical gradients, evidence has accrued that epithelial Na(+) /H(+) exchange indeed may be an alternative pathway for Na(+) uptake. The specific pathways for Na(+) uptake may be species and environment specific. An apical Cl(-) /HCO(3)(-) exchanger is generally accepted for most species (some species do not extract Cl(-) from freshwater), but the relative roles of anion exchanger-like (SLC4A1) vs. pendrin-like (SLC26Z4) exchangers are unknown, and also may be species specific. Most recently, data have supported the presence of an apical Na(+) + Cl(-) cotransporter (NCC-type), despite thermodynamic uncertainty. Ammonia extrusion may be via NH(3) diffusing through the paracellular junctions or NH(4) (+) substitution on both basolateral and apical ionic exchangers (Na(+) + K(+) -ATPase; Na(+) + K(+) + Cl(-) - cotransporter; and Na(+) /H(+) exchanger), but recent evidence suggests that Rhesus-glycoproteins mediate both basolateral and apical movement of ammonia.

MEMS scanner enabled real-time depth sensitive hyperspectral imaging of biological tissue

We demonstrate a hyperspectral and depth sensitive diffuse optical imaging microsystem, where fast scanning is provided by a CMOS compatible 2-axis MEMS mirror. By using lissajous scanning patterns, large field-of-view (FOV) of 1.2 cmx1.2 cm images with lateral resolution of 100 µm can be taken at 1.3 frames-per-second (fps). Hyperspectral and depth-sensitive images were acquired on tissue simulating phantom samples containing quantum dots (QDs) patterned at various depths in Polydimethylsiloxane (PDMS). Device performance delivers 6 nm spectral resolution and 0.43 wavelengths per second acquisition speed. A sample of porcine epithelium with subcutaneously placed QDs was also imaged. Images of the biological sample were processed by spectral unmixing in order to qualitatively separate chromophores in the final images and demonstrate spectral performance of the imaging system.

Histological changes in the uterus of the hens after embryonic exposure to bisphenol A and diethylstilbestrol

Many employed chemicals in industries have estrogenic hormone effects on organisms, and these are called as environmental estrogens. Environmental estrogens have adverse effects on development and function of reproductive organs of the birds. Bisphenol A (BPA) is one of the best known environmental estrogens widely found in plastic products. In this study, we injected BPA and the synthetic estrogen diethylstilbestrol (DES) in ovo and then examined and compared the effects of those on the uteri (shell gland) of the adult hens by histological methods. Five groups have been designed in the current study. Only vehicle substance was given in ovo to the control group and BPA (67 or 134 μg/g egg) and DES (0.02 or 0.2 μg/g egg) were administered in the experimental groups. Tissue specimens were taken from uteri of hens at 21 weeks of age, prior to the laying period. Estrogen receptor alpha (ERα) was immunohistochemically stained. It was observed that the hatching proportion in BPA (67 μg and 134 μg/g) was lesser than the other groups (P<0.01). Uterine tubular glandular density and thickness of tunica mucosa were found to have reduced (P<0.01) in BPA (134 μg/g) and DES (0.2 μg/g) groups, in comparison with those of the control and the other experimental groups. Uterine gland epithelium revealed positive immunoreaction for ERα. These findings suggested that administration of BPA and DES at high doses affected embryonic development in a negative way, and this adverse effect was seen less in adult period.

Experimental and theoretical evaluation of a fiber-optic approach for optical property measurement in layered epithelial tissue

Improvements in measurement of epithelial tissue optical properties (OPs) in the ultraviolet and visible (UV-Vis) may lead to enhanced understanding of optical techniques for neoplasia detection. In this study, we investigated an approach based on fiber-optic measurement of reflectance to determine absorption and reduced scattering coefficients (μ(a) and μ(s)') in two-layer turbid media. Neural network inverse models were trained on simulation data for a wide variety of OP combinations (μ(a) = 1-22.5, μ(s)' = 5-42.5 cm(-1)). Experimental measurements of phantoms with top-layer thicknesses (D) ranging from 0.22 to 0.66 mm were performed at three UV-Vis wavelengths. OP estimation accuracy was calculated and compared to theoretical results. Mean prediction errors were strongly correlated with D and ranged widely, from 1.5 to 12.1 cm(-1). Theoretical analyses indicated the potential for improving accuracy with alternate probe geometries. Although numerous challenges remain, this initial experimental study of an unconstrained approach for fiber-optic-based OP determination in two-layer epithelial tissue indicates the potential to provide useful measurements.

Exposure to flaxseed during lactation does not alter prostate area or epithelium height but changes lipid profile in rats

Flaxseed intake has increased owing to beneficial effects to health and prevention of diseases. Provided that it's an important source of lignan, a phytoestrogen, the present study aimed at evaluating the possible effect of the intake of this seed during lactation upon prostate, sexual hormones and lipidic profile of the offspring in adult life.

MATERIAL AND METHODS

16 female Wistar rats were used. After delivery, they were divided into two different groups to receive one of the following diets during lactation: Control group (CG), with a casein based diet and Flaxseed group (FG), with a flaxseed based diet containing 25% flaxseed. At weaning, male pups received commercial chow until adult life (170 days old), when they were sacrificed.

RESULTS

No differences were perceived concerning offspring food intake and body weight at 170 days. There was a reduction in total cholesterol levels (FG = 45.71 +/- 8.96 mg/dL; CG = 63.43 +/- 15.69 mg/dL, p = 0.02) and triglycerides (FG = 54.29 +/- 11.10 mg/dL; CG = 79.86 +/- 25.68 mg/dL, p = 0.03). Also, no alterations were observed in prostatic morphology, testosterone or estradiol levels in the two groups analyzed.

CONCLUSION

Flaxseed intake during lactation did not produce histological alterations in prostatic alveolus or in sexual hormones, but programmed to a reduction in lipid profile in adult life with decreased cardiovascular risk.

Histological analysis of healthy epithelium of Wistar rats in vivo irradiated with different intensities of therapeutic ultrasound

BACKGROUND

Ultrasound (US) is a widely used and studied resource for physical therapy treatments. Given the scarcity of studies on the effects of US on healthy tissue, many physical therapy professionals make unfounded decisions regarding its methods and parameters of application.

OBJECTIVES

The possible histological and morphometric changes in the healthy tissue of Wistar rats in vivo irradiated with different intensities of US were evaluated.

METHODS

Thirty Wistar rats, randomly distributed among five groups of six animals each, were treated on the right side of the dorsal region, over an area of 4 cm(2). The left side served as a control. The treatment was applied over a four-day period, with two mins. of daily irradiation. The output intensity was checked using a precision dosimeter before the applications. Histological and morphometric analyses were performed using the Image Tool software.

RESULTS

There were slight inflammatory infiltration and thinning of the dermis fibers, particularly in the groups irradiated with 1.5 and 2 W/cm(2). There was also thickening of the epidermis in the samples from the irradiated animals. To evaluate the quantitative results, the statistical analyses consisted of one-way ANOVAs with the post-hoc Tukey tests. There were significant differences in epidermis thicknesses between the control group and the groups irradiated with 1.0, 1.5 and 2.0 W/cm(2).

CONCLUSIONS

Higher doses of US produced changes in the epidermis and dermis, i.e. increased thickness and collagen fiber thinning and proliferation, respectively. These results serve as a warning of the possible implications of therapeutic ultrasound use in esthetics.

Ret-dependent cell rearrangements in the Wolffian duct epithelium initiate ureteric bud morphogenesis

While the genetic control of renal branching morphogenesis has been extensively described, the cellular basis of this process remains obscure. GDNF/RET signaling is required for ureter and kidney development, and cells lacking Ret are excluded from the tips of the branching ureteric bud in chimeric kidneys. Here, we find that this exclusion results from earlier Ret-dependent cell rearrangements in the caudal Wolffian duct, which generate a specialized epithelial domain that later emerges as the tip of the primary ureteric bud. By juxtaposing cells with elevated or reduced RET activity, we find that Wolffian duct cells compete, based on RET signaling levels, to contribute to this domain. At the same time, the caudal Wolffian duct transiently converts from a simple to a pseudostratified epithelium, a process that does not require Ret. Thus, both Ret-dependent cell movements and Ret-independent changes in the Wolffian duct epithelium contribute to ureteric bud formation.

The Drosophila metastasis suppressor gene Nm23 homolog, awd, regulates epithelial integrity during oogenesis

The expression levels of the metastasis suppressor gene Nm23 have been shown to correlate positively or inversely with prognosis in different cancer cohorts. This indicates that Nm23 may be needed at different expression levels and may function differently in various tissues. Here we report a novel epithelial function of the Drosophila melanogaster homolog of human Nm23, abnormal wing discs (awd). We show a dynamic expression pattern of the Awd protein during morphogenesis of the Drosophila follicle cells during oogenesis. Loss-of-function awd mutant cells result in the accumulation and spreading of adherens junction components, such as Drosophila E-cadherin, beta-catenin/Armadillo, and alpha-spectrin, and the disruption of epithelial integrity, including breaking up of the epithelial sheet and piling up of follicle cells. In contrast, overexpression of awd diminishes adherens junction components and induces a mesenchymal-cell-like cell shape change. The gain-of-function phenotype is consistent with a potential oncogenic function of this metastasis suppressor gene. Interestingly, we demonstrate that the epithelial function of awd is mediated by Rab5 and show that the Rab5 expression level is downregulated in awd mutant cells. Therefore, awd modulates the level and localization of adherens junction components via endocytosis. This is the first demonstration of an in vivo function of Nm23 family genes in regulating epithelial morphogenesis.

Quantification of growth asymmetries in developing epithelia

Many developmental processes of multicellular organisms involve the patterning and growth of two-dimensional tissues, so called epithelia. We have quantified the growth of the wing imaginal disk, which is the precursor of the adult wing, of the fruit fly Drosophila melanogaster. We find that growth follows a simple rule with exponentially decreasing area growth rate. Anisotropies of growth can be precisely determined by comparing experimental results to a continuum theory. Growth anisotropies are to good approximation constant in space and time. They are weak in wild-type wing disks but threefold increased in GFP-Dpp disks in which the morphogen Dpp is overexpressed. Our findings indicate that morphogens such as Dpp control tissue shape via oriented cell divisions that generate anisotropic growth.

Morphological and histochemical characteristics of the epithelium of ovarian lamellae of Genypterus blacodes (Schneider, 1801)

The physiological significance of the glycoproteins (GPs) secreted by the epithelium of ovarian lamellae is discussed in reference to the reproductive biology of G. blacodes. Histochemical procedures for localising and characterising GPs were used to determine the cytoplasmic components of cells of the epithelium that covers the ovarian lamellae of pink cuskeel, Genypterus blacodes (Schneider, 1801) (Pisces, Ophidiidae), during spawning. This species is one of the most valuable demersal fish resources in the Argentine Sea, mainly due its large size and flesh quality. GPs with oxidizable vicinal diol groups, sialic acid with or without O-acyl substituents, O-acyl sugars, neutral sugars and GPs with carboxyl and sulphate groups were detected. Light microscope examination showed morphological changes in the epithelium of ovarian lamellae during the spawning season, associated with a secretory activity of mucus. Optical density studies revealed the presence of polyploid cells encompassing those morphological changes. Results of the present study suggest that the epithelium of ovarian lamellae of G. blacodes performs a secretory role, which is intensified during ovarian maturity, suggesting that G. blacodes could release masses of eggs enveloped in mucus.

Enhanced detection of early-stage oral cancer in vivo by optical coherence tomography using multimodal delivery of gold nanoparticles

Contrast in optical coherence tomography (OCT) images can be enhanced by utilizing surface plasmon resonant gold nanoparticles. To improve the poor in vivo transport of gold nanoparticles through biological barriers, an efficient delivery strategy is needed. In this study, the improved penetration and distribution of gold nanoparticles were achieved by microneedle and ultrasound, respectively, and it was demonstrated that this multimodal delivery of antibody-conjugated PEGylated gold nanoparticles enhanced the contrast in in vivo OCT images of oral dysplasia in a hamster model.

Morphological appraisal of gametogenesis. Spermatogenetic process in mammals with particular reference to man

The process of spermatogenesis in man can be subdivided into prenatal, postnatal and adult phases. Special attention is devoted to the cytomorphology of the germ cells in these phases, with a more detailed description of the proliferation, maturation and differentiation of the germ cells in the adult. Thus, spermatogonial renewal, meiotic division and the morphological transformations of the spermatids into mature spermatozoa are described. An outline of the structures characteristic of the latter is also given. The histological organization of the seminiferous epithelium is considered, whereby the concepts of the cycle, stage of the cycle and wave of the seminiferous epithelium are discussed. The duration of both the cycle and that of spermatogenesis of the adult are considered. The present review on mammalian, and chiefly human spermatogenic processes aims at: surveying of current concepts, and compiling of the more important facts and problems of spermatogenesis. The nomenclature and definitions advanced here arise from the concept of continuity of the processes of spermatogenesis from embryo to adult.

[Histophysiology of epithelial and connective tissue components of the vaginal portion of the uterine cervix]

This review provides an analysis of current data on the tissue and cell components of the vaginal portion of the uterine cervix (ectocervix - EC) in human female and on their interrelations under normal conditions and in the development of some pathological processes. Detailed histological and immunocytochemical characteristic is given to two types of the epithelium--stratified squamous and columnar; the regularities and mechanisms of their junction displacement during various age periods are described. The data on the relation between the proliferation activity and apoptosis intensity in EC epithelium at different developmental stages are discussed. The data are presented on connective tissue component (stroma), its vascular and nervous structures. Cellular elements of the immune system contained in EC are examined. The significance of hormones and other biologically active molecules in the control of EC tissue functions and in coordination of their interaction, is emphasized.

[Juxtaoral organ of Chievitz]

This review presents the analysis of the systematized data on human juxtaoral organ (JOO) development, structure and function based on the results of classical and recent morphological studies. JOO morphogenesis is traced, including the appearance of its anlage at the bottom of the primitive mouth, epithelial invagination into the mesenchyme, JOO detachment from the oral epithelium, its innervation, connective tissue capsule formation, and final maturation. The analysis of the results of macroscopical, histological, electron microscopical, histochemical and immunohistochemical studies is presented, suggesting high metabolic and synthetic activity of its epithelium, which expresses several neural markers, and emphasizing a rich innervation of both its epithelial and stromal components. The findings supporting the concepts of JOO secretory and mechanosensory functions, are examined. The data on the differential diagnosis between JOO and tumoral processes are discussed, as well as the pathological changes of JOO itself and their significance for the diagnosis of the diseases.

Wnt5a is essential for intestinal elongation in mice

Morphogenesis of the mammalian small intestine entails extensive elongation and folding of the primitive gut into a tightly coiled digestive tube. Surprisingly, little is known about the cellular and molecular mechanisms that mediate the morphological aspects of small intestine formation. Here, we demonstrate that Wnt5a, a member of the Wnt family of secreted proteins, is essential for the development and elongation of the small intestine from the midgut region. We found that the small intestine in mice lacking Wnt5a was dramatically shortened and duplicated, forming a bifurcated lumen instead of a single tube. In addition, cell proliferation was reduced and re-intercalation of post-mitotic cells into the elongating gut tube epithelium was disrupted. Thus, our study demonstrates that Wnt5a functions as a critical regulator of midgut formation and morphogenesis in mammals.

Functional anatomy of normal bile ducts

The biliary tree is a complex network of conduits that begins with the canals of Hering and progressively merges into a system of interlobular, septal, and major ducts which then coalesce to form the extrahepatic bile ducts, which finally deliver bile to the gallbladder and to the intestine. The biliary epithelium shows a morphological heterogeneity that is strictly associated with a variety of functions performed at the different levels of the biliary tree. In addition to funneling bile into the intestine, cholangiocytes (the epithelial cells lining the bile ducts) are actively involved in bile production by performing both absorbitive and secretory functions. More recently, other important biological properties restricted to cholangiocytes lining the smaller bile ducts have been outlined, with regard to their plasticity (i.e., the ability to undergo limited phenotypic changes), reactivity (i.e., the ability to participate in the inflammatory reaction to liver damage), and ability to behave as liver progenitor cells. Functional interactions with other branching systems, such as nerve and vascular structures, are crucial in the modulation of the different cholangiocyte functions.

Collective epithelial migration and cell rearrangements drive mammary branching morphogenesis

Epithelial organs are built through the movement of groups of interconnected cells. We observed cells in elongating mammary ducts reorganize into a multilayered epithelium, migrate collectively, and rearrange dynamically, all without forming leading cellular extensions. Duct initiation required proliferation, Rac, and myosin light-chain kinase, whereas repolarization to a bilayer depended on Rho kinase. We observed that branching morphogenesis results from the active motility of both luminal and myoepithelial cells. Luminal epithelial cells advanced collectively, whereas myoepithelial cells appeared to restrain elongating ducts. Significantly, we observed that normal epithelium and neoplastic hyperplasias are organized similarly, suggesting common mechanisms of epithelial growth.

Live imaging of chronic inflammation caused by mutation of zebrafish Hai1

The hallmark of chronic inflammation is the infiltration and persistence of leukocytes within inflamed tissue. Here, we describe the first zebrafish chronic inflammation mutant identified in an insertional mutagenesis screen for mutants that exhibit abnormal tissue distribution of neutrophils. We identified a mutant line with an insertion in the Hepatocyte growth factor activator inhibitor 1 gene (hai1; also known as Spint1) that showed accumulation of neutrophils in the fin. The mutant embryos exhibited inflammation in areas of epidermal hyperproliferation that was rescued by knock-down of the type II transmembrane serine protease Matriptase 1 (also known as St14), suggesting a novel role for Hai1-Matriptase 1 pathway in regulating inflammation. Using time-lapse microscopy of mutant embryos that express GFP from a neutrophil-specific promoter, we found that individual neutrophils in inflamed tissue displayed random motility characterized by periods of pausing alternating with periods of motility. During periods of persistent movement the cells were highly polarized, while the pausing modes were characterized by a loss of cell polarity. In contrast to responses to acute injury, neutrophils did not exhibit clear retrograde chemotaxis or resolution of inflammation in the mutant. These findings illustrate the utility of zebrafish as a new model system to study chronic inflammation and to visualize immune responses with high resolution in vivo.

Morphology of the tongue in a newborn Stejneger's beaked whale (Mesoplodon stejnegeri)

This light and scanning electron microscopic (SEM) study on the tongue of a newborn Stejneger's beaked whale (Mesoplodon stejnegeri) demonstrated a clear difference in its form from than that of other cetacean and adult Stejneger's beaked whales. This newborn Stejneger's beaked whale had a spoon-like shaped tongue. The dorsal surface in the center part of the tongue was flat and did not have papillae, but there were marginal papillae and small papillae on the anterior part of the tongue. In the posterior of the tongue, hillock-shaped papillae with taste buds on the epithelium were observed.

A computational study of the development of epithelial acini: I. Sufficient conditions for the formation of a hollow structure

Normal hollow epithelial acini are 3-dimensional culture structures that resemble the architecture and functions of normal breast glands and lobules. This experimental model enables in vitro investigations of genotypic and molecular abnormalities associated with epithelial cancers. However, the way in which the acinar structure is formed is not yet completely understood. Gaining more information about consecutive stages of acini development-starting from a single cell that gives rise to a cluster of randomly oriented cells, followed by cell differentiation that leads to a layer of polarised cells enclosing the hollow lumen-will provide insight into the transformations of eukaryotic cells that are necessary for their successful arrangement into an epithelium. In this paper, we introduce a two-dimensional single-cell-based model representing the cross section of a typical acinus. Using this model, we investigate mechanisms that lead to the unpolarised cell growth, cell polarisation, stabilisation of the acinar structure and maintenance of the hollow lumen and discuss the sufficient conditions for each stage of acinar formation. In the follow-up paper (Rejniak and Anderson, A computational study of the development of epithelial acini. II. Necessary conditions for structure and lumen stability), we investigate what morphological changes are observable in the growing acini when some assumptions of this model are relaxed.

The general architecture of sensory neuroepithelia

All neuroepithelia are sheets of cells lining an internal or external surface of the body and resting on a basement membrane. They consist of at least two kinds of cell, receptor cells and sustentacular (supporting) cells. Some contain undifferentiated precursor cells and senescent or degenerating cells. The potential for plasticity and regeneration in different sensory neuroepithelia varies widely according to their origins and structure in any individual animal and according to the species in which they occur. Four sensory neuroepithelia are described as examples of the range of construction, complexity, and life history.

Induction of proepicardial marker gene expression by the liver bud

Cells of the coronary vessels arise from a unique extracardiac mesothelial cell population, the proepicardium, which develops posterior to the sinoatrial region of the looping-stage heart. Although contribution of the proepicardial cells to cardiac development has been studied extensively, it remains unresolved how the proepicardium is induced and specified in the mesoderm during embryogenesis. It is known, however, that the proepicardium develops from the mesothelium that overlays the liver bud. Here, we show that the expression of proepicardial marker genes - Wt1, capsulin (epicardin, pod1, Tcf21) and Tbx18, can be induced in naïve mesothelial cells by the liver bud, both in vitro and in vivo. Lateral embryonic explants, when co-cultured with the liver bud, were induced to express these proepicardial marker genes. The same induction of the marker genes was detected in vivo when a quail liver bud was implanted in the posterior-lateral regions of a chick embryo. This ectopic induction of marker gene expression was not evident when other endodermal tissues, such as the lung bud or stomach, were implanted. This inductive response to the liver bud was not detectable in host embryos before stage 12 (16-somite stage). These results suggest that, after a specific developmental stage, a large area of the mesothelium becomes competent to express proepicardial marker genes in response to localized liver-derived signal(s). The developmentally regulated competency of mesothelium and a localized inductive signal might play a role in restricting the induction of the proepicardial marker gene expression to a specific region of the mesothelium. The data might also provide a foundation for future engineering of a coronary vascular progenitor population.