Robust hydrogel-integrated microsystems enabled by enhanced interfacial bonding strength

Noncovalent hydrogels, compared to covalent hydrogels, have distinctive advantages including biocompatibility and self-healing property but tend to have poor mechanical robustness, thus restricting their application spectrum. A clue to increase utility of such soft hydrogels without chemical bulk modification can be witnessed in biological organ walls where soft mucous epithelial layers are juxtaposed with tough connective tissues. Perhaps, similarly, bonding noncovalent hydrogels to stronger materials, such as tough hydrogels, might be a viable approach for increasing stability and scalability as well as creating novel functions for hydrogel-based systems. However when attempting to bond these two materials, each of the four existing hydrogel-hydrogel bonding method has practical shortcomings. In this work, we introduce a mucosa-inspired bonding method that realizes interfacial bonding of noncovalent hydrogels to tough, hybrid hydrogels without external glue or bulk modification of the noncovalent gel while preserving interfacial micropatterns. The procedure is simple and we confirmed broad applicability with various noncovalent hydrogels and tough hydrogels. We demonstrated the utility of our bonding method with novel applications regarding in vitro assay, soft robotics and biologically inspired systems.

Histomorphometrical study of the tongue epithelium of the peregrine falcon (Falco peregrinus)

The aim of this study is to examine the dorsal lingual epithelium of the peregrine falcon (Falco peregrinus) of the family Falconidae. The tongue in its dorsal, lateral and ventral surfaces is covered with a non-keratinized multilayered stratified squamous epithelium. Lamina propria is present beneath the epithelial layers. Morphometrically, thickness of the apex tongue epithelium is more than that in the tongue body. Thickness of the ventral surface of the tongue is less than that in the dorsal one. Thickness of the lateral surface of the tongue was thicker than that in the ventral one and tongue body. Large and small conical papillae appeared on the posterior dorsal surface of the lingual body. There are lingual glands in certain areas of tongue body with numerous openings through the dorsal surface.

Interwoven versus Knitted Self-Expandable Metallic Stents: A Comparison Study of Stent-Induced Tissue Hyperplasia in the Rat Esophagus

This study investigated whether interwoven self-expandable metallic stent (I-SEMS) placement suppresses stent-induced tissue hyperplasia compared with conventional knitted self-expandable metallic stent (K-SEMS) placement in a rat esophageal model. Twelve rats were randomly assigned to the I-SEMS (n = 6) and K-SEMS (n = 6) groups. All rats were sacrificed 4 weeks after the stent placement. The degree of stent-induced tissue hyperplasia on esophagography and histologic examination was compared between the groups. Stent placement was technically successful in all rats. Esophagography revealed significantly greater mean luminal diameter of the stented esophagus in the I-SEMS group than in the K-SEMS group (p < 0.001). Histologic examination revealed a significantly lower percentage of tissue hyperplasia area and a significantly thinner submucosal fibrosis in the I-SEMS group than in the K-SEMS group (all p < 0.001). There were no significant differences in the thickness of the epithelial layers (p = 0.290) and degree of inflammatory cell infiltration (p = 0.506). Formation of stent-induced tissue hyperplasia was evident with both I-SEMS and K-SEMS. Placement of I-SEMSs with a small cell size and high flexibility seems to be effective in suppressing stent-induced tissue hyperplasia compared with placement of K-SEMSs in rat esophageal models.

Oral Squamous Cells and Age Estimation in Exfoliative Cytology with Hematoxylin and Eosin Stain– A Quantitative Study

Introduction: Exfoliative cytology in age estimation is a simple, painless, less invasive collection of exfoliative cells from epithelial layers, used as a diagnostic aid for age estimation. The oral cavity is an ideal site for exfoliative epithelial cells with a physiological turnover of cells, turnover decreases as the age increases show age variation with cellular morphological changes. Age estimation is one of the important factors to identify an individual and also helps to know the chronological age of a person. Aim: To analyze and estimate the age from buccal smear and comparing the average cellular size under Image morphometric analysis. Materials and Methods: Buccal mucosal smears are taken using a wooden spatula in gentle motion of scraping and smeared on a clean glass slide and fixed in 95% ethanol immediately after smearing a minimum of around 15 minutes and stained with Haematoxylin and eosin stain. After staining, the cells were observed by microscope and measured by a paint tool. Pearson correlation analysis was done using SPSS software. Results: The cell and nuclear size difference values observed using a Pearson correlation coefficient were statistically significant with p value<0.05 revealing that there is shrinkage in cells with increase in age. Conclusion: Exfoliative cytology is a successful and vastly growing technology that is used for the detection of premalignant lesions.

Comparison of three kinds of self-expandable metallic stents induced granulation tissue hyperplasia in the rabbit trachea

To compare stent-induced granulation tissue hyperplasia of bare (SEMS), polyurethane-covered (PU-SEMS) and electrospun nanofibre-covered (EN-SEMS) self-expandable metallic stents in the rabbit trachea. Twenty-seven rabbits were randomly assigned to 3 groups that received SEMS, PU-SEMS or EN-SEMS. Computed tomography and sacrifice were performed as scheduled. Haematoxylin–eosin and Masson’s trichrome staining protocols were performed for pathological analysis. The data for tracheal ventilation area ratio, qualitative histological scoring, number of epithelial layers, and thicknesses of papillary projection and submucosa were documented and statistically analysed. All stents were successfully placed under the guidance of fluoroscopy without complications. Post-stenting 3 and 7 days, computed tomography revealed that the fully expandable EN-SEMS was similar to the SEMS and PU-SEMS. The mean stented tissue score in the SEMS group was higher than those of both the PU-SEMS and EN-SEMS groups at 3 days post-stenting. The pathological findings suggested that there was no papillary projection formation 3 days after stent placement. The thickness of papillary projection in the SEMS group was significantly higher than those of the PU-SEMS and EN-SEMS groups at 7 days post-stenting. After stenting 4 weeks, the tracheal ventilation area ratio of SEMS, PU-SEMS and EN-SEMS was 0.214 ± 0.021, 0.453 ± 0.028 and 0.619 ± 0.033, respectively. There were significant between-group differences. In conclusion, the stent-induced granulation tissue formation in EN-SEMS is less severe than that of PU-SEMS and SEMS. EN-SEMS has smaller radial force, and the tracheal ventilation ratio after stent placement better than that of PU-SEMS.

Adipocyte Atrophy Mimicking Signet Ring Cell Carcinoma of the Gallbladder

Signet ring cell morphology may result from a variety of causes and ranges from a benign reactive phenomenon to being indicative of highly aggressive malignancy. Benign epithelial signet ring cell change is well described in a variety of tissues, but nonepithelial signet ring cell change is a rare morphologic adaptation of adipose tissue principally described in the setting of cachexia. The location of these atrophic adipocytes outside the plane of normal epithelial layers may raise concern for invasive or metastatic malignancy, and consideration of a benign reactive process is critical to avoid catastrophic overdiagnosis and overtreatment. Further, this change is itself associated with significant mortality related to the underlying cachexia and may be important to highlight to treating clinicians. Compared to malignant signet ring cell carcinoma, benign signet ring cell change is more likely to retain normal lobulated architecture without mass formation, lack significant atypia, have myxoid stroma with a prominent capillary network, and show positive staining S100 protein with negative staining for cytokeratins and mucin. To our knowledge, we present the first described case of nonepithelial signet ring cell change involving the gallbladder, detected as an incidental finding following routine cholecystectomy in an elderly cachectic man.

3D Cell neighbour dynamics in growing pseudostratified epithelia

During morphogenesis, epithelial sheets remodel into complex geometries. How cells dynamically organize their contact with neighbouring cells in these tightly packed tissues is poorly understood. We have used light-sheet microscopy of growing mouse embryonic lung explants, three-dimensional cell segmentation, and physical theory to unravel the principles behind 3D cell organization in growing pseudostratified epithelia. We find that cells have highly irregular 3D shapes and exhibit numerous neighbour intercalations along the apical-basal axis as well as over time. Despite the fluidic nature, the cell packing configurations follow fundamental relationships previously described for apical epithelial layers, i.e., Euler's formula, Lewis' law, and Aboav-Weaire's law, at all times and across the entire tissue thickness. This arrangement minimizes the lateral cell-cell surface energy for a given cross-sectional area variability, generated primarily by the distribution and movement of nuclei. We conclude that the complex 3D cell organization in growing epithelia emerges from simple physical principles.

Trans-cellular tunnels induced by the fungal pathogen Candida albicans facilitate invasion through successive epithelial cells without host damage

SummaryThe opportunistic fungal pathogen Candida albicans is normally commensal, residing in the mucosa of most healthy individuals. In susceptible hosts, its filamentous hyphal form can invade epithelial layers leading to superficial or severe systemic infection. Invasion is mainly intracellular, though it causes no apparent damage to host cells. We investigated the invasive lifestyle of C. albicans in vitro using live-cell imaging and the damage-sensitive reporter galectin-3. Quantitative single cell analysis showed that invasion can result in host membrane breaching at different stages of invasion and cell death, or in traversal of host cells without membrane breaching. Membrane labelling and three-dimensional “volume” electron microscopy revealed that hyphae can traverse several host cells within trans-cellular tunnels that are progressively remodelled and may undergo ‘inflations’ linked to host glycogen stores, possibly during nutrient uptake. Thus, C. albicans invade epithelial tissues by either inflicting or avoiding host damage, the latter facilitated by trans-cellular tunnelling.

Single-cell transcriptomics elucidates in vitro reprogramming of human intestinal epithelium cultured in a physiodynamic gut-on-a-chip

The microphysiological human gut-on-a-chip has demonstrated in vivo-relevant cellular fidelity of intestinal epithelium compared to its cultures in a static condition. Microfluidic control of morphogen gradients and mechanical cues robustly induced morphological histogenesis with villi-like three-dimensional (3D) microarchitecture, lineage-associated cytodifferentiation, and physiological functions of a human intestinal Caco-2 epithelium. However, transcriptomic dynamics that orchestrates morphological and functional reprogramming of the epithelium in a microphysiological culture remains elusive. Single-cell transcriptomic analysis revealed that a gut-on-a-chip culture that offers physiological motions and flow drives three distinctive subclusters that offer distinct gene expression and unique spatial representation in 3D epithelial layers. The pseudotemporal trajectory of individual cells visualized the evolutionary transition from ancestral genotypes in static cultures into more heterogeneous phenotypes in physiodynamic cultures on cell cycles, differentiation, and intestinal functions including digestion, absorption, drug transport, and metabolism of xenobiotics. Furthermore, the inversed transcriptomic signature of oncogenes and tumor-suppressor genes of Caco-2 cells verified that a gut-on-a-chip culture drives a postmitotic reprogramming of cancer-associated phenotypes. Thus, we discovered that a physiodynamic on-chip culture is necessary and sufficient for a cancer cell line to be reprogrammed to elicit in vivo-relevant heterogeneous cell populations with restored normal physiological signatures.

Modelling the collective mechanical regulation of the structure and morphology of epithelial cell layers

The morphology and function of epithelial sheets play an important role in healthy tissue development and cancer progression. The maintenance of structure of closely packed epithelial layers requires the coordination of various mechanical forces within the cells and others resulting from interactions with other cells and other tissues or substrates. However, a general model for the combination of mechanical properties which determine the cell shape and the overall structure of epithelial layers remains elusive. Here, we propose a computational model, based on the Cellular Potts Model, to study the interplay between mechanical properties of cells and dynamical transitions in epithelial structures and cell shapes. We map out phase diagrams as functions of cellular properties and the orientation of cell division. Monolayers of squamous, cuboidal, and columnar cells are found when the axis of cell proliferation is perpendicular to the substrate. Monolayer-to-multilayer transition is promoted via cell extrusion, depending on the mechanical properties of cells and the orientation of cell division. The results and model predictions are discussed in the context of experimental observations.