Epithelia migration: a spatiotemporal interplay between contraction and adhesion

Hybrid model to simulate host cell biomechanics and infection spread during intracellular infection of epithelial monolayers

Mechanical signals are crucial in regulating the response of cells in a monolayer to both physiological and pathological stressors, including intracellular bacterial infections. In particular, during intracellular infection of epithelial cells in monolayer with the food-borne bacterial pathogen Listeria monocytogenes, cellular biomechanics dictates the degree of bacterial dissemination across the monolayer. This occurs through a process whereby surrounder uninfected cells mechanically compete and eventually extrude infected cells. However, the plethora of physical mechanisms involved and their temporal dynamics are still not fully uncovered, which could inform whether they benefit or harm the host. To further investigate these mechanisms, we propose a two-dimensional hybrid computational model that combines an agent-based model with a finite element method to simulate the kinematics and dynamics of epithelial cell monolayers in the absence or presence of infection. The model accurately replicated the impact of cell density on the mechanical behaviour of uninfected monolayers, showing that increased cell density reduces cell motility and coordination of motion, cell fluidity and monolayer stresses. Moreover, when simulating the intercellular spread of infection, the model successfully reproduced the mechanical competition between uninfected and infected cells. Infected cells showed a reduction in cell area, while the surrounder cells migrated towards the infection site, exerting increased monolayer stresses, consistent with our in vitro observations. This model offers a powerful tool for studying epithelial monolayers in health and disease, by providing in silico predictions of cell shapes, kinematics and dynamics that can then be tested experimentally.

Identification of SERPINE1, PLAU and ACTA1 as biomarkers of head and neck squamous cell carcinoma based on integrated bioinformatics analysis

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is the six leading cancer by incidence worldwide. The 5-year survival rate of HNSCC patients remains less than 65% due to lack of symptoms in the early stage. Hence, biomarkers which can improve detection of HNSCC should improve clinical outcome.

METHODS

Gene expression profiles (GSE6631, GSE58911) and the Cancer Genome Atlas (TCGA) HNSCC data were used for integrated bioinformatics analysis; the differentially expressed genes (DEGs) were then subjected to functional and pathway enrichment analysis, protein-protein interaction (PPI) network construction. Subsequently, module analysis of the PPI network was performed and overall survival (OS) analysis of hub genes in subnetwork was studied. Finally, immunohistochemistry was used to verify the selected markers.

RESULTS

A total of 52 up-regulated and 80 down-regulated DEGs were identified, which were mainly associated with ECM-receptor interaction and focal adhesion signaling pathways. Importantly, a set of prognostic signatures including SERPINE1, PLAU and ACTA1 were screened from DEGs, which could predict OS in HNSCC patients from TCGA cohort. Experiment of clinical samples further successfully validated that these three signature genes were aberrantly expressed in the oral epithelial dysplasia and HNSCC, and correlated with aggressiveness of HNSCC patients.

CONCLUSIONS

SERPINE1, PLAU and ACTA1 played important roles in regulating the initiation and progression of HNSCC, and could be identified as key biomarkers for precise diagnosis and prognosis of HNSCC, which will provide potential targets for clinical therapies.

Redox control of Cas phosphorylation requires Abl kinase in regulation of intestinal epithelial cell spreading and migration

Intestinal wounds often occur during inflammatory and ischemic disorders of the gut. To repair damage, intestinal epithelial cells must rapidly spread and migrate to cover exposed lamina propria, events that involve redox signaling. Wounds are subject to extensive redox alterations, particularly resulting from H2O2 produced in the adjacent tissue by both the epithelium and emigrating leukocytes. The mechanisms governing these processes are not fully understood, particularly at the level of protein signaling. Crk-associated substrate, or Cas, is an important signaling protein known to modulate focal adhesion and actin cytoskeletal dynamics, whose association with Crk is regulated by Abl kinase, a ubiquitously expressed tyrosine kinase. We sought to evaluate the role of Abl regulation of Cas at the level of cell spreading and migration during wound closure. As a model, we used intestinal epithelial cells exposed to H2O2 or scratch wounded to assess the Abl-Cas signaling pathway. We characterized the localization of phosphorylated Cas in mouse colonic epithelium under baseline conditions and after biopsy wounding the mucosa. Analysis of actin and focal adhesion dynamics by microscopy or biochemical analysis after manipulating Abl kinase revealed that Abl controls redox-dependent Cas phosphorylation and localization to influence cell spreading and migration. Collectively, our data shed new light on redox-sensitive protein signaling modules controlling intestinal wound healing.