Synaptopodin is required for stress fiber and contractomere assembly at the epithelial junction

The apical junction of epithelial cells can generate force to control cell geometry and perform contractile processes while maintaining barrier function and cell-cell adhesion. Yet, the structural basis of force generation at the apical junction is not completely understood. Here, we describe 2 actomyosin structures at the apical junction containing synaptopodin, myosin IIB, and alpha-actinin-4. We showed that synaptopodin is required for the assembly of E-cadherin-associated apical stress fibers and a novel macromolecular structure, which we named contractomere. Knockdown of synaptopodin abolished both apical stress fiber and contractomere formation. Moreover, depletion of synaptopodin abolished basal stress fibers, converting myosin IIA sarcomere-like arrangement into a meshwork-type actomyosin organization. We propose a new model of junction dynamics that is dependent on contractomere movement to control epithelial cell boundary and geometry. Our findings reveal 2 actomyosin structures at the epithelial junction and underscore synaptopodin in the assembly of stress fibers and contractomeres.Summary StatementSynaptopodin assembles 2 actomyosin structures at the epithelial junction: apical stress fiber and contractomere. Synaptopodin selectively regulates myosin IIB without altering the level of myosin IIA and is responsible for converting evolutionary-conserved actomyosin meshwork into vertebrate-specific stress fibers.Graphic Abstract

ANTI-INFECTIVE EFFECTIVENESS OF ASCORBIC ACID IN THE ORAL MUCOSA OF GUINEA PIGS

Objective:To know the anti-infective effectiveness of ascorbic acid, after a linear incision in the mucosa of the mandibular antero-inferior segment of the oral cavity of the guinea pigs, housed in the vivarium of the Biology Center of the Central University of Ecuador. Materials and methods:This study is experimental in-vivo and longitudinal, where an incision was made in the mucosa of the mandibular anteroinferior segment of the oral cavity in guinea pigs, three groups of 10 guinea pigs were formed, Group C, received mega doses ( 1.42 ml / 214.2 mg) which contained high amounts of ascorbic acid, Group B received normal doses (0.095 ml / 14.25 mg) and group Aor control group did not receive ascorbic acid, this dose was applied one day before, during, and one day after the incision. The clinical evaluation was performed at 24 and 72 hours post incision, a sample was taken by swab from the wounded area at 72 hours for the planting of bacterial cultivation. Results: The clinical examination shows that at 24 hours in group C, 0% bleeding, edema, and erythema, and 100% epithelial junction, while in group B, 30% bleeding, 50% edema, 50% erythema and 100% epithelial junction and in group A50% bleeding, 40% edema, 40% erythema and 20% epithelial junction; at 72 hours the results in group C and B showed better healing percentages in relation to group A, in this group some guinea pigs still showed bleeding edema and erythema in the wounded area. Conclusion: It is determined that the guinea pigs who received mega doses of ascorbic acid presented a better result in the process of healing after clinical examination at 24 and 72 hours and the swab exam shows a lower amount of bacterial colonization, thus demonstrating the effectiveness of ascorbic acid in mega doses of infectious processes.

Effectiveness of Various Gingival Sulcus Widening Materials

The gingival-dental sulcus is a V-shaped depression located around the tooth neck; the space surrounded by the free gingival edge, the tooth (near the enamel-cement junction), and the junction between the gum and the tooth (epithelial junction); it contains the gingival sulcus fluid and the dental plaque. The long-term clinical success of prosthetic restorations depends on the careful and accurate completion of several procedures. One of the difficult procedures is the management of gum tissues and gum aesthetics. Their goal is to maintain the normal appearance of the healthy gum. Achieving this goal requires optimal periodontal health before treatment and minimal injury during treatment. The best way to optimize these things is to avoid touching the gum with the restoration materials.Our research was conducted on a number of nine (9) voluntary patients. Gingival sulcus widening is important for the accuracy of the impression for a future fixed prosthetic work, especially when the finishing line is in contact with the gingival sulcus. Dilation of the gingival sulcus is also important when crown restorations are performed in the cervix area due to the contact of the bare material with the periodontal tissues. Among the methods used for dilating the gingival sulcus, non-surgical ones are preferred by practitioners. For aesthetic and functional reasons, the edges of prosthetic restorations are placed under the gum. Therefore, the practitioner should record as accurately as possible the finishing edges to allow adequate edge integrity for restoration. This can be done by dilating the gingival sulcus, but also by providing a clean and dry space. In order to create a faithful mockup of the soft and hard tissue of the oral cavity, the gum around the prepared teeth should be thoroughly checked. This gum should be displaced and bleeding is avoided.

Synaptopodin couples epithelial contractility to α-actinin-4–dependent junction maturation

The epithelial junction experiences mechanical force exerted by endogenous actomyosin activities and from interactions with neighboring cells. We hypothesize that tension generated at cell–cell adhesive contacts contributes to the maturation and assembly of the junctional complex. To test our hypothesis, we used a hydraulic apparatus that can apply mechanical force to intercellular junction in a confluent monolayer of cells. We found that mechanical force induces α-actinin-4 and actin accumulation at the cell junction in a time- and tension-dependent manner during junction development. Intercellular tension also induces α-actinin-4–dependent recruitment of vinculin to the cell junction. In addition, we have identified a tension-sensitive upstream regulator of α-actinin-4 as synaptopodin. Synaptopodin forms a complex containing α-actinin-4 and β-catenin and interacts with myosin II, indicating that it can physically link adhesion molecules to the cellular contractile apparatus. Synaptopodin depletion prevents junctional accumulation of α-actinin-4, vinculin, and actin. Knockdown of synaptopodin and α-actinin-4 decreases the strength of cell–cell adhesion, reduces the monolayer permeability barrier, and compromises cellular contractility. Our findings underscore the complexity of junction development and implicate a control process via tension-induced sequential incorporation of junctional components.