Pseudostratified Epithelium Research Articles

Globulomaxillary Cyst in a 16 year old male patient-A case report with review

Globulomaxillary cyst is an uncommon, specious cyst. It was traditionally described as a fissural cyst between the maxillary lateral incisor and canine teeth, secondary to proliferation of entrapped epithelium between the globular portion of the medial nasal and maxillary processes. They are painless, submucosal, non-odontogenic jaw cysts presenting as soft tissue swellings in the maxillary anterior mucolabial fold lateral to midline. Present case documents 16 year old male patient with diffuse extra-oral swelling present involving the philtrum and extending upto the nasolabial fold was observed on the left side of the face. Intraorally well-defined soft and fluctuant swelling was present with pus discharge. Radiographically, well defined heart shaped radiolucency was observed in the left maxillary periapical region. The cyst was enucleated using intra-oral approach. Histopathological findings revealed pseudostratified ciliated epithelium with overlying inflammatory cells and goblet cells. Diagnosis of globulomaxillary cyst was confirmed.

Heterotopic respiratory mucosa of the uterine corpus

A 47-year-old, single, Chinese woman presented with pain on the 1st day of menses for more than 30 years. Her dysmenorrhea worsened over years and underwent a total abdominal hysterectomy and bilateral salpingooophorectomy. The myometrium showed trabeculated appearance, and there were adhesions between ovaries and fallopian tubes. A pale solid brownish mass measuring 1.5 cm × 1 cm × 0.6 cm with fibrous whitish cut surfaces was present on the lateral wall of the uterus in the lower uterine segment. Histologically, adenomyosis and left ovarian endometriosis were confirmed. The lateral uterine wall nodule showed a tubular structure lined by ciliated pseudostratified columnar epithelium. Smooth muscle bundles were found around the entire tubular structure. Lobules of salivary type glands containing both serous and mucous cells are present. The pathological diagnosis of heterotopic respiratory mucosa (HRM) was made. To our knowledge, this is the first reported case of HRM of the uterine corpus.

MICROANATOMY OF THE DIGESTIVE SYSTEM OF ENTEROCTOPUS MEGALOCYATHUS (CEPHALOPODA, OCTOPODA) OF THE SOUTHWEST ATLANTIC

A detailed description of the microanatomy of the digestive system of Enteroctopus megalocyathus is given, and this revealed some differences between this octopod species and other species of Octopodidae previously described. These differences are mainly related to tissues lining the lumen of digestive organs. Unlike descriptions in some octopods mucosa, in E. megalocyathus a pseudostratified epithelium is found covering the lumen of oesophagus, crop, stomach, intestine and caecum. Another major finding is that in the posterior salivary glands, two cell types are present in the same tubular adenomere; they do not constitute independent glandular tubules with only one type of glandular cells. The tubules of these glands are lined by two distinct epithelial cells, distributed from the distal to the proximal zones: type A, in the proximal zone of the glandular tubule, with cylindrical cells and globular mucous cells; and type B in the distal zone, cylindrical, with a weakly eosinophilic cytoplasm. The secretion of the cells was detected applying PAS and alcian blue at different pH. In the octopuses maintained without food in the aquarium for two days, histological structure of the epithelium of the caecum, intestine and digestive gland showed histological changes specially related with the mucosa. Taken together, the results allow to set the histological structure of the digestive tract of E. megalocyathus in their natural habitat and to provide preliminary evidence that this system responds rapidly (~2 days) to food deprivation, and give baseline data for future studies investigating the impact of environmental changes on the gut.

BMP signaling and cellular dynamics during regeneration of airway epithelium from basal progenitors.

The pseudostratified epithelium of the lung contains ciliated and secretory luminal cells and basal stem/progenitor cells. To identify signals controlling basal cell behavior we screened factors that alter their self-renewal and differentiation in a clonal organoid (tracheosphere) assay. This revealed that inhibitors of the canonical BMP signaling pathway promote proliferation but do not affect lineage choice, whereas exogenous Bmp4 inhibits proliferation and differentiation. We therefore followed changes in BMP pathway components in vivo in the mouse trachea during epithelial regeneration from basal cells after injury. The findings suggest that BMP signaling normally constrains proliferation at steady state and this brake is released transiently during repair by the upregulation of endogenous BMP antagonists. Early in repair, the packing of epithelial cells along the basal lamina increases, but density is later restored by active extrusion of apoptotic cells. Systemic administration of the BMP antagonist LDN-193189 during repair initially increases epithelial cell number but, following the shedding phase, normal density is restored. Taken together, these results reveal crucial roles for both BMP signaling and cell shedding in homeostasis of the respiratory epithelium.

Morphometric and Immunohistochemical Studies on Camel Efferent Ductules in Relation to Reproductive Activity

Introduction: The efferent ductules that arise from rete testis convey spermatozoa from the testis to the epididymis. Seasonal studies on morphological and immunohistochemical characteristics of camel reproductive organs are rare. This study aimed to elucidate the morphometric changes and immunoreactivities of S-100 and alpha smooth muscle actin (α-SMA) in dromedary camel efferent ductules during rutting (reproductive) and non-rutting (non-reproductive) seasons. Methods: Simple (proximal part) and pseudo-stratified (distal part) columnar epithelium lined the efferent ductules, which contained ciliated and non-ciliated cells that gave the epithelial lining its wavy shape. Results: The epithelium was significantly higher and stereocilia were insignificantly longer during non-breeding season as compared to breeding season. There was a significant increase in luminal diameter and muscular coat thickness during breeding season. The epithelium of proximal and distal segments as well as smooth muscles and surrounding connective tissue exhibited positive S-100 reactions during breeding and non-breeding seasons; this reaction was stronger in breeding season than non-breeding season. The epithelial cell reaction was negative or very weak to α-SMA during breeding and non-breeding seasons, whereas smooth muscle and surrounding connective tissue showed positive reaction which was stronger in breeding season. Conclusion: In conclusion, S-100 and α-SMA show seasonal morphometric and immunoreactivities variations in camel efferent ductules; these variations could be associated with the physiological condition during breeding and non-breeding seasons.

Differentiation of respiratory epithelium in a 3-dimensional co-culture with fibroblasts embedded in fibrin gel.

BackgroundTracheal tissue engineering is a promising option for the treatment of tracheal defects. In a previous study we proved the suitability of fibrin gel as a scaffold for tracheal tissue engineering. This study investigates whether the differentiation of respiratory epithelium can be increased by culturing epithelial cells in a three dimensional system containing fibroblasts embedded into fibrin gel.MethodsRespiratory epithelial cells were isolated from porcine trachea, seeded onto a fibrin gel and kept in air-liquid-interface culture for 33 days. Morphology as well as pan-cytokeratin, MUC5AC and claudin-1 expression of cells cultured on pure fibrin gel were compared to culture on gels containing fibroblasts.ResultsAfter two weeks, cells seeded on pure fibrin gel were multilayered, showed hyperproliferation and dedifferentiation. Co-cultured cells built up a pseudostratified epithelium. The differentiation and organization of epithelial structure improved with respect to time. After four weeks, morphology of the co-cultured respiratory epithelium resembled native tracheal epithelium. Immunohistochemistry showed that respiratory epithelium co-cultured with fibroblasts had an increasing similarity of pan-cytokeratin expression compared to native trachea. Cells cultured without fibroblasts differed in pan-cytokeratin expression from native trachea and did not show any improvement of differentiation. Immunohistochemical staining of MUC5AC and claudin-1 proved seeded cells being respiratory epithelial cells.ConclusionsThis study indicates that adding fibroblasts to fibrin gel positively influences the differentiation of respiratory epithelium.

Regulation of epithelial function, differentiation, and remodeling in the epididymis.

The epididymis is a single convoluted tubule lined by a pseudostratified epithelium. Specialized epididymal epithelial cells, the so-called principal, basal, narrow, and clear cells, establish a unique luminal environment for the maturation and storage of spermatozoa. The epididymis is functionally and structurally divided into several segments and sub-segments that create regionally distinct luminal environments. This organ is immature at birth, and epithelial cells acquire their fully differentiated phenotype during an extended postnatal period, but the factors involved in this complex process remain incompletely characterized. In the adult epididymis, the establishment of an acidic luminal pH and low bicarbonate concentration in the epididymis contributes to preventing premature activation of spermatozoa during their maturation and storage. Clear cells are proton-secreting cells throughout the epididymis, but principal cells have distinct acid/base transport properties, depending on their localization within the epididymis. Basal cells are located in all epididymal segments, but they have a distinct morphology depending on the segment and species examined. How this structural plasticity of basal cells is regulated is discussed here. Also, the role of luminal factors and androgens in the regulation of epithelial cells is reviewed in relation to their respective localization in the proximal versus distal regions of the epididymis. Finally, we describe a novel role for CFTR in tubulogenesis and epithelial cell differentiation.

Deep RNA-Seq analysis reveals unexpected features of human prostate basal epithelial cells

Abstract Prostate cancer is the second leading cause of cancer-related deaths among American men [ 1 ]. The prostate gland mainly contains basal and luminal cells, which are constructed as a pseudostratified epithelium. Annotation of prostate epithelial transcriptomes provides a foundation for discoveries that can impact disease understanding and treatment. Here, for the first time, we describe a whole-genome transcriptome analysis of human benign prostatic basal and luminal populations by using deep RNA sequencing (GSE67070) [2]. Combined with comprehensive molecular and biological characterizations, we show that the differential gene expression profiles account for their distinct functional phenotypes. Strikingly, in contrast to luminal cells, basal cells preferentially express gene categories associated with stem cells, neural and neuronal development, and RNA processing. Of clinical relevance, the treatment failed castration-resistant and anaplastic prostate cancers molecularly resemble a basal-like phenotype. We also identified genes associated with patient clinical outcome. Therefore, we provide a gene expression resource for understanding human prostate epithelial lineages, and link the cell-type specific gene signatures to subtypes of prostate cancer development.

Reproductive System of Brown-throated Sloth (Bradypus variegatus, Schinz 1825, Pilosa, Xenarthra): Anatomy and Histology.

In recent years, habitat degradation led to the decline of some populations of brown-throated sloth. The aim of this study was to describe morphological features of the female reproductive system of the species. The oval ovaries were partially surrounded by ovarian bursa. An external cortex and an inner medulla were present. Corpora lutea and corpora albicans together with follicles at various stages of development each with a single oocyte were found in the cortex. Uterine tubes were tortuous, tubular, travelled around the perimeter of the ovary and possessed a folded mucosa with ciliated pseudostratified epithelium. Uterus was simplex, with no horns and divided into three parts: a pear-shaped cranial segment and a long caudal uterine segment (both forming the body of the uterus) and two cervices. Uterus presented three layers: mucosa, lined by pseudostratified epithelium, muscular and serosa. The cervices connected the uterus to the urogenital sinus, a distensible cavity with longitudinal mucosal folds lined by transitional epithelium that extended from the external urethral orifice and the external uterine ostia to the vulva, which was lined by a keratinized stratified squamous epithelium. Brown-throated sloth presented a bipartite clitoris with paired crura, bodies and glandes. The presence of a double cervix and a bipartite clitoris was unique features of the species.

Keratin-dependent regulation of Aire and gene expression in skin tumor keratinocytes

Expression of the intermediate filament protein keratin 17 (K17) is robustly upregulated in inflammatory skin diseases and in many tumors originating in stratified and pseudostratified epithelia1-3. We report that Autoimmune regulator (Aire), a transcriptional regulator, is inducibly expressed in human and mouse tumor keratinocytes in a K17-dependent manner and required for a timely onset of Gli2-induced skin tumorigenesis in mice. Induction of Aire mRNA in keratinocytes depends upon a functional interaction between K17 and the heterogeneous nuclear ribonucleoprotein hnRNP K4. Further, K17 colocalizes with Aire protein in the nucleus of tumor-prone keratinocytes, and each are bound to a specific promoter region featuring a NF-κB consensus sequence in a relevant subset of K17- and Aire-dependent pro-inflammatory genes. These findings provide radically new insight into keratin intermediate filament and Aire function, along with a molecular basis for the K17-dependent amplification of inflammatory and immune responses in diseased epithelia.

Nasopalatine Duct Cyst: Report of a Case and Discussion of Differential Diagnosis

Nasopalatine duct cyst (NDC) is the most common non-odontogenic jaw cyst, arising from embryologic remnants of the nasopalatine duct. A 20-year-old male presented with a painless swelling in the hard palate. Cone-beam computed tomography revealed well-defined hypodense image, extending from the periapical region of tooth #13 to that of tooth #21. The lesion, which was approximately 2.0 cm in diameter, promoted root resorption in tooth #12, as well as expansion of the vestibular and palatine bone cortices. Histological examination of an excisional biopsy sample revealed a pathological cavity lined with cuboidal or ciliated pseudostratified columnar epithelium, with foci of squamous metaplasia. The cyst wall was composed of fibrovascular connective tissue with arteries, veins, minor salivary glands, and multiple moderate sized nerves. The final diagnosis was NDC. This case highlights the relevant aspects in the diagnosis of NDC based on clinical, radiological, and pathological features.

Morphology of the urogenital papilla and its component ducts in Astyanax altiparanae Garutti & Britski, 2000 (Characiformes: Characidae)

The histological description of the urogenital papilla is an important tool to comprehension of the reproductive mechanisms in fish, as well as a pre-requisite to germ cell transplantation in adult fish, besides to be a good biological indicator to environmental changes. Was performed the histological description of the urogenital papilla and its component ducts in the tetra Astyanax altiparanae. The genital and urinay ducts pass separately throughout most part of its extension, joining in a single duct before opening. In males this opening is asymmetric and seems to have double origin, being completely surrounded by striated muscle fibers, while in females it is symmetric and the muscle fibers does not surround it totally. Spermatic duct and oviduct undergo changes throughout their extension, mainly in the morphology of the surrounding epithelium. In the spermatic duct, squamous epithelial cells change to columnar and cuboid with possible secretory activity, close to testes. In the oviduct, anteriorly epithelial cells are also squamous, however, close to ovary there are lamellae composed by a pseudostratified epithelium with columnar and cuboid cells. The urinary duct is highly similar for both sexes presenting globoid cells, which description is known in mammals, however, rare in fish.

Inexpensive production of near-native engineered stromas

Although the self-assembly approach is an efficient method for the production of engineered physiological and pathological tissues, avoiding the use of exogenous materials, it nevertheless remains expensive and requires dexterity, which are features incompatible with large-scale production. We propose a modification to this technique to make easier the production of mesenchymal compartment, to reduce the cost and to improve the histological quality of the self-assembled tissues. The stroma produced by this novel approach allowed epithelial cell differentiation, resulting in a pseudostratified epithelium that shared several features with native tissues. The incorporation of endothelial cells in the reconstructed mesenchyme formed a three-dimensional capillary-like network, positive for CD31 and von Willebrand factor and surrounded by NG2 positive cells. It could limit self-contraction of the resulting tissue by recruiting α-Smooth Muscle Actin positive cells. With this new technique, which is relatively inexpensive and easy to use in a research laboratory set-up, near-native stromas can now be produced with minimal handling time. Copyright © 2015 John Wiley & Sons, Ltd.

Spinal neurenteric cyst in a dog

A 2-year-old female crossbreed dog was presented with progressive ataxia and paraparesis. A T3-L3 spinal lesion was determined by neurological examination. Magnetic resonance imaging (MRI) revealed an ovoid-shaped, well-circumscribed mass affecting the spinal cord at the level of the T9 vertebra. A left hemilaminectomy and a durotomy at the level of T9 allowed discovery of an ovoid deformation of the meninges with a cystic appearance.En bloc removal was performed and appeared to be complete. Pathological analysis showed a voluminous cystic lesion lined by a heterogeneous epithelium. Three types of epithelium were present: a pseudostratified columnar epithelium, a stratified squamous epithelium and a transitional epithelium. Mucus production, the morphology of some cells with microvilli at the apical pole and immunohistochemical assays were highly in favor of an endodermal origin of the cyst. The age of the dog, anamnesis, MRI study and histological findings were consistent with an intradural neurenteric cyst as described in humans. Total surgical removal led to a progressive clinical improvement with no recurrence at 18 months. We report an unusual intradural extramedullary cyst, called a neurenteric cyst, in a 2-year-old female crossbreed dog. This type of cyst is well-known in humans but has never been described in dogs. We propose that neurenteric cysts should be included in the differential diagnoses for tumor-like or cystic intradural lesions in the young dog. Prognosis for this type of cyst seems to be good, as total surgical removal led to a progressive clinical improvement with no recurrence at 18 months.

Light and electron microscopy study of the spermatheca of Eupholidoptera chabrieri bimucronata (Ramme, 1927) and Uromenus brevicollis trinacriae La Greca 1964 (Orthoptera: Tettigoniidae).

A study by both optical and electron microscopy has been carried out on the spermatheca of Eupholidoptera chabrieri bimucronata and Uromenus brevicollis trinacriae (Orthoptera: Tettigoniidae). In both the examined species, the spermatheca consists of a sac/kidney-shaped seminal receptacle and a more or less tortuous spermathecal duct that opens into the common oviduct. The wall of both the organs consists of a pseudostratified epithelium surmounted by a cuticular intima; the latter is made up of a thicker endocuticle and an epicuticle. The epithelium shows two different cell types, irregularly arranged and with well differentiated functions: cuticle-forming and gland cells. In both the species, the cuticle-forming cells perform other functions, in addition to producing the cuticular intima. The gland cells never come in contact with the cuticular intima, have inside the reservoir a secretion whose appearance can diversify also in contiguous zones of the seminal receptacle. Based on our findings in both the species, the functions of the seminal receptacle would differ from those of the spermathecal duct. In the latter, some areas of the wall of the connecting tract show an activity of lysis, by contiguous epithelial cells, that could play a role in control and selection of spermatozoa. As for the feather-shaped spermatodesms, similar in both the species, freeze-fracture observations have shown that the acrosome of each spermatozoon regularly covers three-quarters of the extension of the acrosome of the following spermatozoon. Finally, the significance of our findings, compared with what is known in literature, is discussed.

Expression and relationship of pendrin and MUC5AC in patients with chronic rhinosinusitis

To explore the expression of pendrin in sinonasal mucosal tissue of patients with chronic rhinosinusitis (CRS) and examine its relationship with mucin5AC (MUC5AC). Thirty mucosal tissue (located on anterior wall of maxillary sinus ostium and close to uncinate process) of patients with CRS with or without nasal polyps and 10 normal sinonasal mucosal tissue located at the same sites as CRS were collected. Histological changes of sinonasal mucosa were examined by hematoxylin and eosin (HE) staining. The expression of total mucins was evaluated by periodic acid Schiff staining (PAS). And the expressions of pendrin and MUC5AC in sinonasal mucosa were determined by immunohistochemistry (IHC), quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. The tissue samples demonstrated mucosal thickening, goblet cell hyperplasia and metaplasia, epithelial cilia partial deletion, glandular hyperplasia and a dense infiltration of inflammatory cells in CRS with or without nasal polyps. IHC revealed that positive pendrin was expressed dominantly at apical membrane of epithelial cells and sparsely in submucosal glandular cells, there was a positive expression rate of CRS with nasal polyps and CRS without nasal polyps; MUC5AC was expressed abundantly in goblet cells and pseudostratified ciliated columnar epithelium cells and weakly in submucosal glandular cells in CRS. There were significant increases in positive expression rate of total mucins production, pendrin and MUC5AC in patients of CRS with nasal polyps or without nasal polyps than those in control (86.7% and 80.0% vs 20.0%, 73.3% and 70.0% vs 10.0%, 83.3% and 76.7% vs 20.0%, all P<0.05); the relative expression levels of mRNA and protein expression of pendrin were significantly greater in patients of CRS with or without nasal polyps than those in controls (1.685±0.111 and 1.537±0.262 vs 1.012±0.167, 2.066±0.188 and 1.996±0.153 vs 1.000±0.169, all P<0.05). The relative expression levels of mRNA expression of MUC5AC were significantly greater in patients of CRS with or without nasal polyps than in controls (1.861±0.718 and 1.562±0.428 vs 1.004±0.094, P<0.05). And the expression level of pendrin mRNA was positively correlated with that of MUC5AC mRNA in patients with CRS (r=0.670, P=0.006 and r=0.713, P=0.003). An up-regulation of pendrin is correlated with an over-expression of MUC5AC in patients with CRS. And pendrin is an important cause of mucus hypersecretion in CRS.

Activation of NOTCH1 or NOTCH3 signaling skews human airway basal cell differentiation toward a secretory pathway.

Airway basal cells (BC) function as stem/progenitor cells capable of differentiating into the luminal ciliated and secretory cells to replenish the airway epithelium during physiological turnover and repair. The objective of this study was to define the role of Notch signaling in regulating human airway BC differentiation into a pseudostratified mucociliated epithelium. Notch inhibition with γ-secretase inhibitors demonstrated Notch activation is essential for BC differentiation into secretory and ciliated cells, but more so for the secretory lineage. Sustained cell autonomous ligand independent Notch activation via lentivirus expression of the intracellular domain of each Notch receptor (NICD1-4) demonstrated that the NOTCH2 and 4 pathways have little effect on BC differentiation into secretory and ciliated cells, while activation of the NOTCH1 or 3 pathways has a major influence, with persistent expression of NICD1 or 3 resulting in a skewing toward secretory cell differentiation with a parallel decrease in ciliated cell differentiation. These observations provide insights into the control of the balance of BC differentiation into the secretory vs ciliated cell lineage, a balance that is critical for maintaining the normal function of the airway epithelium in barrier defense against the inhaled environment.

Pathology of thyroglossal duct: an institutional experience.

Thyroglossal duct (TGD) is a developmental anomaly in which a remnant of the thyroid anlage is left in the neck during its descent from the foramen cecum of tongue to final pretracheal position. A persistent duct can lead to thyroglossal duct cyst (TGDC). Histologically, TGDC contains an epithelial lining of squamous or pseudostratified ciliated columnar epithelium and ectopic thyroid gland tissue in the duct wall. TGD-associated malignancy is rare, and the majority is papillary thyroid carcinoma (PTC). A total of 242 patients with a diagnosis of TGD-associated lesions were identified in our institute. Two hundred and seventeen cases were diagnosed as TGDC. Sixty-eight of 217 (31.3 %) cases of TGDC had ectopic thyroid tissue in the cystic wall. Thirty-nine cases had preoperative fine needle aspiration (FNA). Of these cases, 37 of 39 (94.9 %) demonstrated macrophages and 19 (48.7 %) also showed cells of squamous and/or columnar epithelial lining. Only two cases showed rare thyroid follicular cells. Thyroid carcinoma was identified in 18 of 242 (7.4 %) cases. All cases were diagnosed as PTC including 12 cases of classic PTC (66.7 %), 3 cases of follicular variant (16.7 %), 2 cases of tall cell variant (11.1 %), and 1 case of classic PTC with focal tall cell features (5.6 %). Nine cases had TGD component (either epithelial lining cysts or ectopic thyroid tissue). Ten patients also underwent total thyroidectomy (67 %). Of these patients, four had no tumor and one had an incidental medullary carcinoma. Five of 10 (50 %) cases had incidental PTC with a size range of 0.1-0.3 cm. Five patients had follow-up by imaging studies; no suspicious or nodular lesions were found in the thyroid. In conclusion, we report an institutional case cohort of 242 patients with TGD-associated lesions, including 217 TGDC and 18 cases of PTC. Only seven cases fulfilled the diagnostic criteria of TGD-associated PTC, i.e., the presence of components of TGD and a normal thyroid. In the remaining 11 cases, we could not differentiate with certainty between pyramidal primary thyroid PTC/Delphian node metastasis or TGD-associated PTC.

Morphological and morphometric characterization of direct transdifferentiation of support cells into hair cells in ototoxin-exposed neonatal utricular explants

We have studied aminoglycoside-induced vestibular hair-cell renewal using long-term culture of utricular macula explants from 4-day-old rats. Explanted utricles were exposed to 1 mM of gentamicin for 48 h, during 2nd and 3rd days in vitro (DIV), and then recovering in unsupplemented medium. Utricles were harvested at specified time points from the 2nd through the 28th DIV. The cellular events that occurred within hair cell epithelia during the culture period were documented from serial sectioned specimens. Vestibular hair cells (HCs) and supporting cells (SCs) were systematically counted using light microscopy (LM) with the assistance of morphometric software. Ultrastructural observations were made from selected specimens with transmission electron microscopy (TEM). After 7 DIV, i.e. four days after gentamicin exposure, the density of HCs was 11% of the number of HCs observed in non-gentamicin-exposed control explants. At 28 DIV the HC density was 61% of the number of HCs observed in the control group explant specimens. Simultaneously with this increase in HCs there was a corresponding decline in the number of SCs within the epithelium. The proportion of HCs in relation to SCs increased significantly in the gentamicin-exposed explant group during the 5th to the 28th DIV period of culture. There were no significant differences in the volume estimations of the gentamicin-exposed and the control group explants during the observed period of culture. Morphological observations showed that gentamicin exposure induced extensive loss of HCs within the epithelial layer, which retained their intact apical and basal linings. At 7 to 14 DIV (i.e. 3–11 days after gentamicin exposure) a pseudostratified epithelium with multiple layers of disorganized cells was observed. At 21 DIV new HCs were observed that also possessed features resembling SCs. After 28 DIV a new luminal layer of HCs with several layers of SCs located more basally characterized the gentamicin-exposed epithelium. No mitoses were observed within the epithelial layer of any explants.Our conclusion is that direct transdifferentiation of SCs into HCs was the only process contributing to the renewal of HCs after gentamicin exposure in these explants of vestibular inner ear epithelia obtained from the labyrinths of 4-day-old rats.

Interkinetic Nuclear Migration Is Centrosome Independent and Ensures Apical Cell Division to Maintain Tissue Integrity

Pseudostratified epithelia are widespread during animal development and feature elongated cells whose nuclei adopt various positions along the apicobasal cell axis. Before mitosis, nuclei migrate toward the apical surface, and subsequent divisions occur apically. So far, the exact purpose of this nuclear migration remained elusive. One hypothesis was that apical migration ensures that nuclei and centrosomes meet for mitosis. We here demonstrate that in zebrafish neuroepithelia apical nuclear migration occurs independently of centrosome position or integrity. It is a highly reproducible phenomenon linked to the cell cycle via CDK1 activity. We propose that the robustness of bringing nuclei apically for mitosis ensures that cells are capable of reintegrating into the epithelium after division. Nonapical divisions lead to cell delamination and formation of cell clusters that subsequently interfere with neuronal layering. Therefore, positioning divisions apically in pseudostratified neuroepithelia could serve to safeguard epithelial integrity and enable proper proliferation and maturation.