Integrins regulate epithelial cell shape by controlling the architecture and mechanical properties of basal actomyosin networks

Exploring the anti-cancer and antimetastatic effect of Silymarin against lung cancer

Lung cancer metastasis remains a significant challenge in cancer therapy, necessitating the exploration of novel treatment modalities. Silymarin, a natural compound derived from milk thistle, has demonstrated promising anticancer properties. This work explored the inhibitory effects of silymarin on lung cancer metastasis and revealed the underlying processes, focusing on matrix metalloproteinase (MMP) 2 and MMP-9 activities. Using a combination of in vitro and molecular docking analyses, we found that silymarin effectively reducing the lung cancer cells' motility and invasion by modulation of expression of MMP-2 and MMP-9. Furthermore, MTT assays revealed a dose-dependent inhibition of cell proliferation upon silymarin treatment and found the IC50 value at 58 μM. We observe that apoptotic morphology characteristic in silymarin treated groups. Cell cycle analysis exhibit the cell cycle arrest at G1 phase, 25.8 % increased apoptosis in silymarin treated groups, as evidenced by Annexin V staining. Moreover, silymarin treatment shows the lipid peroxidation in elevated level and reduced in enzymatic antioxidant level, indicating its potential role in mitigating oxidative stress induce cell death. Gelatin zymography assay indicates the silymarin has ability to inhibit the MMP-2 and MMP-9 expression in lung cancer. Additionally, cell migration assays and colony formation assays demonstrated impaired migratory and colony-forming abilities of lung cancer cells when treated with silymarin. Molecular docking studies further supported the binding affinity of silymarin with MMP-2 and MMP-9, demonstrate the -10.26 and -6.69 kcal/mol of binding energy. Collectively, our findings highlight the multifaceted anticancer properties of silymarin against lung cancer metastasis, providing insights into its therapeutic potential as an adjuvant treatment strategy.

Tensions on the actin cytoskeleton and apical cell junctions in the C. elegans spermatheca are influenced by spermathecal anatomy, ovulation state and activation of myosin

Introduction

Cells generate mechanical forces mainly through myosin motor activity on the actin cytoskeleton. In C. elegans, actomyosin stress fibers drive contractility of the smooth muscle-like cells of the spermatheca, a distensible, tube-shaped tissue in the hermaphrodite reproductive system and the site of oocyte fertilization. Stretching of the spermathecal cells by oocyte entry triggers activation of the small GTPase Rho. In this study, we asked how forces are distributed in vivo, and explored how spermathecal tissue responds to alterations in myosin activity.

Methods

In animals expressing GFP labeled actin or apical membrane complexes, we severed these structures using femtosecond laser ablation and quantified retractions. RNA interference was used to deplete key contractility regulators.

Results

We show that the basal actomyosin fibers are under tension in the occupied spermatheca. Reducing actomyosin contractility by depletion of the phospholipase C-ε/PLC-1 or non-muscle myosin II/NMY-1, leads to distended spermathecae occupied by one or more embryos, but does not alter tension on the basal actomyosin fibers. However, activating myosin through depletion of the Rho GAP SPV-1 increases tension on the actomyosin fibers, consistent with earlier studies showing Rho drives spermathecal contractility. On the inner surface of the spermathecal tube, tension on the apical junctions is decreased by depletion of PLC-1 and NMY-1. Surprisingly, when basal contractility is increased through SPV-1 depletion, the tension on apical junctions also decreases, with the most significant effect on the junctions aligned in perpendicular to the axis of the spermatheca.

Discussion

Our results suggest that much of the tension on the basal actin fibers in the occupied spermatheca is due to the presence of the embryo. Additionally, increased tension on the outer basal surface may compress the apical side, leading to lower tensions apically. The three dimensional shape of the spermatheca plays a role in force distribution and contractility during ovulation.

Tensions on the actin cytoskeleton and apical cell junctions in the C. elegans spermatheca are influenced by spermathecal anatomy, ovulation state and activation of myosin

Cells generate mechanical forces mainly through myosin motor activity on the actin cytoskeleton. In C. elegans, actomyosin stress fibers drive contractility of the smooth muscle-like cells of the spermatheca, a distensible, tube-shaped tissue in the hermaphrodite reproductive system and the site of oocyte fertilization. Stretching of the spermathecal cells by oocyte entry triggers activation of the small GTPase Rho. In this study, we asked how forces are distributed in vivo using the spermatheca, and explored how this tissue responds to alterations in myosin activity. Using laser ablation, we show that the basal actomyosin fibers are under tension in the occupied spermatheca. Reducing actomyosin contractility by depletion of the phospholipase C-ε/PLC-1 or non-muscle myosin II/NMY-1, leads to distended spermathecae occupied by one or more embryos, but does not alter tension on the basal actomyosin fibers. This suggests that much of the tension on the basal actin fibers in the occupied spermatheca is due to the presence of the embryo. However, activating myosin through depletion of the Rho GAP SPV-1 increases tension on the actomyosin fibers, consistent with earlier studies showing Rho drives spermathecal contractility. On the inner surface of the spermathecal tube, tension on the apical junctions is decreased by depletion of PLC-1 and NMY-1. Surprisingly, when basal contractility is increased through SPV-1 depletion, the tension on apical junctions also decreases, with the most significant effect on the junctions aligned in perpendicular to the axis of the spermatheca. This suggests tension on the outer basal surface may compress the apical side, and suggests the three-dimensional shape of the spermatheca plays a role in force distribution and contractility during ovulation.

A dystroglycan-laminin-integrin axis coordinates cell shape remodeling in the developing Drosophila retina

Cell shape remodeling is a principal driver of epithelial tissue morphogenesis. While progress continues to be made in our understanding of the pathways that control the apical (top) geometry of epithelial cells, we know comparatively little about those that control cell basal (bottom) geometry. To examine this, we used the Drosophila ommatidium, which is the basic visual unit of the compound eye. The ommatidium is shaped as a hexagonal prism, and generating this 3D structure requires ommatidial cells to adopt specific apical and basal polygonal geometries. Using this model system, we find that generating cell type-specific basal geometries starts with patterning of the basal extracellular matrix, whereby Laminin accumulates at discrete locations across the basal surface of the retina. We find the Dystroglycan receptor complex (DGC) is required for this patterning by promoting localized Laminin accumulation at the basal surface of cells. Moreover, our results reveal that localized accumulation of Laminin and the DGC are required for directing Integrin adhesion. This induces cell basal geometry remodeling by anchoring the basal surface of cells to the extracellular matrix at specific, Laminin-rich locations. We propose that patterning of a basal extracellular matrix by generating discrete Laminin domains can direct Integrin adhesion to induce cell shape remodeling in epithelial morphogenesis.

Phage Display as a Medium for Target Therapy Based Drug Discovery, Review and Update

Phage libraries are now amongst the most prominent approaches for the identification of high-affinity antibodies/peptides from billions of displayed phages in a specific library through the biopanning process. Due to its ability to discover potential therapeutic candidates that bind specifically to targets, phage display has gained considerable attention in targeted therapy. Using this approach, peptides with high-affinity and specificity can be identified for potential therapeutic or diagnostic use. Furthermore, phage libraries can be used to rapidly screen and identify novel antibodies to develop immunotherapeutics. The Food and Drug Administration (FDA) has approved several phage display-derived peptides and antibodies for the treatment of different diseases. In the current review, we provided a comprehensive insight into the role of phage display-derived peptides and antibodies in the treatment of different diseases including cancers, infectious diseases and neurological disorders. We also explored the applications of phage display in targeted drug delivery, gene therapy, and CAR T-cell.

Osteopontin Rejuvenates Senescent Adipose-Derived Stem Cells and Restores their Bone Tissue Regenerative Function

The regenerative function of stem cells is compromised when the proportion of senescent stem cells increases with ageing advance. Therefore, combating stem cell senescence is of great importance for stem cell-based tissue engineering in the elderly, but remains largely unexplored. Osteopontin (OPN), a glycosylated phosphoprotein, is one of the key extracellular matrix molecules in bone tissue. OPN activates various signalling pathways and modulates cellular activities, including cell senescence. However, the role of OPN in stem cell senescence remains largely unknown. This study aims to investigate if OPN modulates cell senescence and bone regenerative function in human adipose-derived mesenchymal stem cells (ASCs), and to determine the underlying mechanisms. We first developed a senescent ASC model using serial passaging until passage 10 (P10), in which senescent cells were characterised by reduced proliferation and osteogenic differentiation capacity compared to P4 ASCs. The conditioned medium from P10 ASCs exhibited a diminished trophic effect on human osteoblasts (HOBs), compared to that from P4 ASCs. P10 ASCs on OPN-coated surface showed rejuvenated phenotype and enhanced osteogenic differentiation. The conditioned medium from P10 ASCs on OPN-coating improved trophic effects on HOBs. OPN regulated the morphology of senescent ASCs, transforming them from a more rounded and flattened cell shape to an elongated shape with a smaller area. These findings demonstrated the effects of OPN in restoring senescent ASCs functions, possibly through a mechanism that involves the modulation of cell morphology, indicating that OPN might hold a great potential for rejuvenating senescent stem cells and could potentially open a new venue for regenerating bone tissue in age-related diseases.

Basal spot junctions of Drosophila epithelial tissues respond to morphogenetic forces and regulate Hippo signaling

Organ size is controlled by numerous factors including mechanical forces, which are mediated in part by the Hippo pathway. In growing Drosophila epithelial tissues, cytoskeletal tension influences Hippo signaling by modulating the localization of key pathway proteins to different apical domains. Here, we discovered a Hippo signaling hub at basal spot junctions, which form at the basal-most point of the lateral membranes and resemble adherens junctions in protein composition. Basal spot junctions recruit the central kinase Warts via Ajuba and E-cadherin, which prevent Warts activation by segregating it from upstream Hippo pathway proteins. Basal spot junctions are prominent when tissues undergo morphogenesis and are highly sensitive to fluctuations in cytoskeletal tension. They are distinct from focal adhesions, but the latter profoundly influences basal spot junction abundance by modulating the basal-medial actomyosin network and tension experienced by spot junctions. Thus, basal spot junctions couple morphogenetic forces to Hippo pathway activity and organ growth.

JNK signaling and integrins cooperate to maintain cell adhesion during epithelial fusion in Drosophila

The fusion of epithelial sheets is an essential and conserved morphogenetic event that requires the maintenance of tissue continuity. This is secured by membrane-bound or diffusible signals that instruct the epithelial cells, in a coordinated fashion, to change shapes and adhesive properties and when, how and where to move. Here we show that during Dorsal Closure (DC) in Drosophila, the Jun kinase (JNK) signaling pathway modulates integrins expression and ensures tissue endurance. An excess of JNK activity, as an outcome of a failure in the negative feedback implemented by the dual-specificity phosphatase Puckered (Puc), promotes the loss of integrins [the ß-subunit Myospheroid (Mys)] and amnioserosa detachment. Likewise, integrins signal back to the pathway to regulate the duration and strength of JNK activity. Mys is necessary for the regulation of JNK activity levels and in its absence, puc expression is downregulated and JNK activity increases.

Finishing the egg

Gamete development is a fundamental process that is highly conserved from early eukaryotes to mammals. As germ cells develop, they must coordinate a dynamic series of cellular processes that support growth, cell specification, patterning, the loading of maternal factors (RNAs, proteins, and nutrients), differentiation of structures to enable fertilization and ensure embryonic survival, and other processes that make a functional oocyte. To achieve these goals, germ cells integrate a complex milieu of environmental and developmental signals to produce fertilizable eggs. Over the past 50 years, Drosophila oogenesis has risen to the forefront as a system to interrogate the sophisticated mechanisms that drive oocyte development. Studies in Drosophila have defined mechanisms in germ cells that control meiosis, protect genome integrity, facilitate mRNA trafficking, and support the maternal loading of nutrients. Work in this system has provided key insights into the mechanisms that establish egg chamber polarity and patterning as well as the mechanisms that drive ovulation and egg activation. Using the power of Drosophila genetics, the field has begun to define the molecular mechanisms that coordinate environmental stresses and nutrient availability with oocyte development. Importantly, the majority of these reproductive mechanisms are highly conserved throughout evolution, and many play critical roles in the development of somatic tissues as well. In this chapter, we summarize the recent progress in several key areas that impact egg chamber development and ovulation. First, we discuss the mechanisms that drive nutrient storage and trafficking during oocyte maturation and vitellogenesis. Second, we examine the processes that regulate follicle cell patterning and how that patterning impacts the construction of the egg shell and the establishment of embryonic polarity. Finally, we examine regulatory factors that control ovulation, egg activation, and successful fertilization.

Integrins Can Act as Suppressors of Ras-Mediated Oncogenesis in the Drosophila Wing Disc Epithelium

Cancer is the second leading cause of death worldwide. Key to cancer initiation and progression is the crosstalk between cancer cells and their microenvironment. The extracellular matrix (ECM) is a major component of the tumour microenvironment and integrins, main cell-ECM adhesion receptors, are involved in every step of cancer progression. However, accumulating evidence has shown that integrins can act as tumour promoters but also as tumour suppressor factors, revealing that the biological roles of integrins in cancer are complex. This incites a better understating of integrin function in cancer progression. To achieve this goal, simple model organisms, such as Drosophila, offer great potential to unravel underlying conceptual principles. Here, we find that in the Drosophila wing disc epithelium the βPS integrins act as suppressors of tumours induced by a gain of function of the oncogenic form of Ras, RasV12. We show that βPS integrin depletion enhances the growth, delamination and invasive behaviour of RasV12 tumour cells, as well as their ability to affect the tumour microenvironment. These results strongly suggest that integrin function as tumour suppressors might be evolutionarily conserved. Drosophila can be used to understand the complex tumour modulating activities conferred by integrins, thus facilitating drug development.

Actin polymerization and depolymerization in developing vertebrates

Development is a complex process that occurs throughout the life cycle. F-actin, a major component of the cytoskeleton, is essential for the morphogenesis of tissues and organs during development. F-actin is formed by the polymerization of G-actin, and the dynamic balance of polymerization and depolymerization ensures proper cellular function. Disruption of this balance results in various abnormalities and defects or even embryonic lethality. Here, we reviewed recent findings on the structure of G-actin and F-actin and the polymerization of G-actin to F-actin. We also focused on the functions of actin isoforms and the underlying mechanisms of actin polymerization/depolymerization in cellular and organic morphogenesis during development. This information will extend our understanding of the role of actin polymerization in the physiologic or pathologic processes during development and may open new avenues for developing therapeutics for embryonic developmental abnormalities or tissue regeneration.

Alveolar repair following LPS-induced injury requires cell-ECM interactions

During alveolar repair, alveolar type 2 (AT2) epithelial cell progenitors rapidly proliferate and differentiate into flat AT1 epithelial cells. Failure of normal alveolar repair mechanisms can lead to loss of alveolar structure (emphysema) or development of fibrosis, depending on the type and severity of injury. To test if β1-containing integrins are required during repair following acute injury, we administered E. coli lipopolysaccharide (LPS) by intratracheal injection to mice with a postdevelopmental deletion of β1 integrin in AT2 cells. While control mice recovered from LPS injury without structural abnormalities, β1-deficient mice had more severe inflammation and developed emphysema. In addition, recovering alveoli were repopulated with an abundance of rounded epithelial cells coexpressing AT2 epithelial, AT1 epithelial, and mixed intermediate cell state markers, with few mature type 1 cells. AT2 cells deficient in β1 showed persistently increased proliferation after injury, which was blocked by inhibiting NF-κB activation in these cells. Lineage tracing experiments revealed that β1-deficient AT2 cells failed to differentiate into mature AT1 epithelial cells. Together, these findings demonstrate that functional alveolar repair after injury with terminal alveolar epithelial differentiation requires β1-containing integrins.

Constriction imposed by basement membrane regulates developmental cell migration

The basement membrane (BM) is a specialized extracellular matrix (ECM), which underlies or encases developing tissues. Mechanical properties of encasing BMs have been shown to profoundly influence the shaping of associated tissues. Here, we use the migration of the border cells (BCs) of the Drosophila egg chamber to unravel a new role of encasing BMs in cell migration. BCs move between a group of cells, the nurse cells (NCs), that are enclosed by a monolayer of follicle cells (FCs), which is, in turn, surrounded by a BM, the follicle BM. We show that increasing or reducing the stiffness of the follicle BM, by altering laminins or type IV collagen levels, conversely affects BC migration speed and alters migration mode and dynamics. Follicle BM stiffness also controls pairwise NC and FC cortical tension. We propose that constraints imposed by the follicle BM influence NC and FC cortical tension, which, in turn, regulate BC migration. Encasing BMs emerge as key players in the regulation of collective cell migration during morphogenesis.

RTK signalling promotes epithelial columnar cell shape and apical junction maintenance in human lung progenitor cells

Multipotent epithelial progenitor cells can be expanded from human embryonic lungs as organoids and maintained in a self-renewing state using a defined medium. The organoid cells are columnar, resembling the cell morphology of the developing lung tip epithelium in vivo. Cell shape dynamics and fate are tightly coordinated during development. We therefore used the organoid system to identify signalling pathways that maintain the columnar shape of human lung tip progenitors. We found that EGF, FGF7 and FGF10 have distinct functions in lung tip progenitors. FGF7 activates MAPK/ERK and PI3K/AKT signalling, and is sufficient to promote columnar cell shape in primary tip progenitors. Inhibitor experiments show that MAPK/ERK and PI3K/AKT signalling are key downstream pathways, regulating cell proliferation, columnar cell shape and cell junctions. We identified integrin signalling as a key pathway downstream of MAPK/ERK in the tip progenitors; disrupting integrin alters polarity, cell adhesion and tight junction assembly. By contrast, stimulation with FGF10 or EGF alone is not sufficient to maintain organoid columnar cell shape. This study employs organoids to provide insight into the cellular mechanisms regulating human lung development.

Non-muscle myosin 2 at a glance

Non-muscle myosin 2 (NM2) motors are the major contractile machines in most cell types. Unsurprisingly, these ubiquitously expressed actin-based motors power a plethora of subcellular, cellular and multicellular processes. In this Cell Science at a Glance article and the accompanying poster, we review the biochemical properties and mechanisms of regulation of this myosin. We highlight the central role of NM2 in multiple fundamental cellular processes, which include cell migration, cytokinesis, epithelial barrier function and tissue morphogenesis. In addition, we highlight recent studies using advanced imaging technologies that have revealed aspects of NM2 assembly hitherto inaccessible. This article will hopefully appeal to both cytoskeletal enthusiasts and investigators from outside the cytoskeleton field who have interests in one of the many basic cellular processes requiring actomyosin force production.

Integrins control epithelial stem cell proliferation in the Drosophila ovary by modulating the Notch pathway

Cell proliferation and differentiation show a remarkable inverse relationship. The temporal coupling between cell cycle withdrawal and differentiation of stem cells (SCs) is crucial for epithelial tissue growth, homeostasis and regeneration. Proliferation vs. differentiation SC decisions are often controlled by the surrounding microenvironment, of which the basement membrane (BM; a specialized form of extracellular matrix surrounding cells and tissues), is one of its main constituents. Years of research have shown that integrin-mediated SC-BM interactions regulate many aspects of SC biology, including the proliferation-to-differentiation switch. However, these studies have also demonstrated that the SC responses to interactions with the BM are extremely diverse and depend on the cell type and state and on the repertoire of BM components and integrins involved. Here, we show that eliminating integrins from the follicle stem cells (FSCs) of the Drosophila ovary and their undifferentiated progeny increases their proliferation capacity. This results in an excess of various differentiated follicle cell types, demonstrating that cell fate determination can occur in the absence of integrins. Because these phenotypes are similar to those found in ovaries with decreased laminin levels, our results point to a role for the integrin-mediated cell-BM interactions in the control of epithelial cell division and subsequent differentiation. Finally, we show that integrins regulate proliferation by restraining the activity of the Notch/Delta pathway during early oogenesis. Our work increases our knowledge of the effects of cell-BM interactions in different SC types and should help improve our understanding of the biology of SCs and exploit their therapeutic potential.

Gaining Wings to FLY: Using Drosophila Oogenesis as an Entry Point for Citizen Scientists in Laboratory Research

Citizen science is a productive approach to include non-scientists in research efforts that impact particular issues or communities. In most cases, scientists at advanced career stages design high-quality, exciting projects that enable citizen contribution, a crowdsourcing process that drives discovery forward and engages communities. The challenges of having citizens design their own research with no or limited training and providing access to laboratory tools, reagents, and supplies have limited citizen science efforts. This leaves the incredible life experiences and immersion of citizens in communities that experience health disparities out of the research equation, thus hampering efforts to address community health needs with a full picture of the challenges that must be addressed. Here, we present a robust and reproducible approach that engages participants from Grade 5 through adult in research focused on defining how diet impacts disease signaling. We leverage the powerful genetics, cell biology, and biochemistry of Drosophila oogenesis to define how nutrients impact phenotypes associated with genetic mutants that are implicated in cancer and diabetes. Participants lead the project design and execution, flipping the top-down hierarchy of the prevailing scientific culture to co-create research projects and infuse the research with cultural and community relevance.

The basement membrane controls size and integrity of the Drosophila tracheal tubes

Biological tubes are fundamental units of most metazoan organs. Their defective morphogenesis can cause malformations and pathologies. An integral component of biological tubes is the extracellular matrix, present apically (aECM) and basally (BM). Studies using the Drosophila tracheal system established an essential function for the aECM in tubulogenesis. Here, we demonstrate that the BM also plays a critical role in this process. We find that BM components are deposited in a spatial-temporal manner in the trachea. We show that laminins, core BM components, control size and shape of tracheal tubes and their topology within the embryo. At a cellular level, laminins control cell shape changes and distribution of the cortical cytoskeleton component α-spectrin. Finally, we report that the BM and aECM act independently-yet cooperatively-to control tube elongation and together to guarantee tissue integrity. Our results unravel key roles for the BM in shaping, positioning, and maintaining biological tubes.

A coarse-grained approach to model the dynamics of the actomyosin cortex

Background

The dynamics of the actomyosin machinery is at the core of many important biological processes. Several relevant cellular responses such as the rhythmic compression of the cell cortex are governed, at a mesoscopic level, by the nonlinear interaction between actin monomers, actin crosslinkers, and myosin motors. Coarse-grained models are an optimal tool to study actomyosin systems, since they can include processes that occur at long time and space scales, while maintaining the most relevant features of the molecular interactions.

Results

Here, we present a coarse-grained model of a two-dimensional actomyosin cortex, adjacent to a three-dimensional cytoplasm. Our simplified model incorporates only well-characterized interactions between actin monomers, actin crosslinkers and myosin, and it is able to reproduce many of the most important aspects of actin filament and actomyosin network formation, such as dynamics of polymerization and depolymerization, treadmilling, network formation, and the autonomous oscillatory dynamics of actomyosin.

Conclusions

We believe that the present model can be used to study the in vivo response of actomyosin networks to changes in key parameters of the system, such as alterations in the attachment of actin filaments to the cell cortex.

Supplementary Information

The online version contains supplementary material available at (10.1186/s12915-022-01279-2).

Crosstalk between basal extracellular matrix adhesion and building of apical architecture during morphogenesis

Tissues build complex structures like lumens and microvilli to carry out their functions. Most of the mechanisms used to build these structures rely on cells remodelling their apical plasma membranes, which ultimately constitute the specialised compartments. In addition to apical remodelling, these shape changes also depend on the proper attachment of the basal plasma membrane to the extracellular matrix (ECM). The ECM provides cues to establish apicobasal polarity, and it also transduces forces that allow apical remodelling. However, physical crosstalk mechanisms between basal ECM attachment and the apical plasma membrane remain understudied, and the ones described so far are very diverse, which highlights the importance of identifying the general principles. Here, we review apicobasal crosstalk of two well-established models of membrane remodelling taking place during Drosophila melanogaster embryogenesis: amnioserosa cell shape oscillations during dorsal closure and subcellular tube formation in tracheal cells. We discuss how anchoring to the basal ECM affects apical architecture and the mechanisms that mediate these interactions. We analyse this knowledge under the scope of other morphogenetic processes and discuss what aspects of apicobasal crosstalk may represent widespread phenomena and which ones are used to build subsets of specialised compartments.

Pentagalloyl Glucose-Laden Poly(lactide-co-glycolide) Nanoparticles for the Biomechanical Extracellular Matrix Stabilization of an In Vitro Abdominal Aortic Aneurysm Model

The suppression of abdominal aortic aneurysm (AAA) growth by nonsurgical therapy is currently not an option, and AAA is considered an irreversible destructive disease. The formation and development of AAA is associated with the progressive deterioration of the aortic wall. Infiltrated macrophages and resident vascular smooth muscle cells oversecrete matrix metalloproteinases (MMPs), which cause the loss of crucial aortic extracellular matrix (ECM) components, thus weakening the aortic wall. Stabilization of the aortic ECM could enable the development of novel therapeutic options for preventing and reducing AAA progression. In the present work, we studied the biochemical and biomechanical interactions of pentagalloyl glucose (PGG) on mouse C2C12 myoblast cells. PGG is a naturally occurring ECM-stabilizing polyphenolic compound that has been studied in various applications, including vascular health, with promising results. With its known limitations of systemic administration, we also studied the administration of PGG when encapsulated within poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs). Treatment with collagenase and elastase enzymes was used to mimic a pathway of degenerative effects seen in the pathogenesis of human AAA. PGG and PLGA(PGG) NPs were added to enzyme-treated cells in either a suppressive or preventative scenario. Biomolecular interactions were analyzed through cell viability, cell adhesion, reactive oxygen species (ROS) production, and MMP-2 and MMP-9 secretion. Biomechanical properties were studied through atomic force microscopy and quartz crystal microbalance with dissipation. Our results suggest that PGG or PLGA(PGG) NPs caused minor to no cytotoxic effects on the C2C12 cells. Both PGG and PLGA(PGG) NPs showed reduction in ROS and MMP-2 secretion if administered after enzymatic ECM degradation. A quantitative comparison of Young's moduli showed a significant recovery in the elastic properties of the cells treated with PGG or PLGA(PGG) NPs after enzymatic ECM degradation. This work provides preliminary support for the use of a pharmacological therapy for AAA treatment.

From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues

Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.

Cellular and Supracellular Planar Polarity: A Multiscale Cue to Elongate the Drosophila Egg Chamber

Tissue elongation is known to be controlled by oriented cell division, elongation, migration and rearrangement. While these cellular processes have been extensively studied, new emerging supracellular mechanisms driving tissue extension have recently been unveiled. Tissue rotation and actomyosin contractions have been shown to be key processes driving Drosophila egg chamber elongation. First, egg chamber rotation facilitates the dorsal-ventral alignment of the extracellular matrix and of the cell basal actin fibers. Both fiber-like structures form supracellular networks constraining the egg growth in a polarized fashion thus working as 'molecular corsets'. Second, the supracellular actin fiber network, powered by myosin periodic oscillation, contracts anisotropically driving tissue extension along the egg anterior-posterior axis. During both processes, cellular and supracellular planar polarity provide a critical cue to control Drosophila egg chamber elongation. Here we review how different planar polarized networks are built, maintained and function at both cellular and supracellular levels in the Drosophila ovarian epithelium.