Vinculin in cell-cell and cell-matrix adhesions

Improved Cell Adhesion on Self-Assembled Chiral Nematic Cellulose Nanocrystal Films

Chirality is ubiquitous in nature, and closely related to biological phenomena. Nature-originated nanomaterials such as cellulose nanocrystals (CNCs) are able to self-assemble into hierarchical chiral nematic CNC films and impart handedness to nano and micro scale. However, the effects of the chiral nematic surfaces on cell adhesion are still unknown. Herein, this work presents evidence that the left-handed self-assembled chiral nematic CNC films (L-CNC) significantly improve the adhesion of L929 fibroblasts compared to randomly arranged isotropic CNC films (I-CNC). The fluidic force microscopy-based single-cell force spectroscopy is introduced to assess the cell adhesion forces on the substrates of L-CNC and I-CNC, respectively. With this method, a maximum adhesion force of 133.2 nN is quantified for mature L929 fibroblasts after culturing for 24 h on L-CNC, whereas the L929 fibroblasts exert a maximum adhesion force of 78.4 nN on I-CNC under the same condition. Moreover, the instant SCFS reveals that the integrin pathways are involved in sensing the chirality of substrate surfaces. Overall, this work offers a starting point for the regulation of cell adhesion via the self-assembled nano and micro architecture of chiral nematic CNC films, with potential practical applications in tissue engineering and regenerative medicine.

Identification of c-Jun phosphorylation as a crucial mediator of complement activation in renal ischemia-reperfusion injury revealed by phosphoproteomics and functional validation

BACKGROUND

Ischemia reperfusion injury (IRI) is an unavoidable condition that primarily affects graft function in renal transplantation. Blockage of complement activation by complement receptor immunoglobulin/ factor H (CRIg/FH), a novel complement inhibitor, shows great potency to ameliorate renal IRI. Sublytic membrane attack complex (MAC) disrupts cellular functions via the activation of different protein kinases and phosphorylation of critical signal transduction factors. We aimed to investigate whether complement activation triggered shift in phosphorylation status in IRI.

METHODS AND RESULTS

We performed a LC-MS/MS-based quantitative phosphoproteomic analysis of CRIg/FH-IRI, PBS-IRI and Sham mice, depicting a thorough protein phosphorylation profile. C3d and MAC staining were conducted to study the complement activation status. In vitro model mimicking complement mediated IRI tubular injury was achieved by applying normal human serum (NHS) to TCMK cells. By hierarchical clustering, we observed that CRIg/FH treatment reversed the hyperphosphorylation status triggered by IRI. Differentially expressed phosphoproteins (DEPs) were associated with focal adhesion, integrin activation, actin cytoskeleton organization and cell junction. We identified c-Jun as the most differentially phosphorylated transcriptional factor regulated by complement activation, the S63 phosphorylation of which was verified both in vitro and in vivo and screened for its downstream targets. JNK inhibitor reduced the phosphorylation of c-Jun and attenuated accumulation of the C3d on the tubular epithelial cells.

CONCLUSION

We proposed a crucial role of c-Jun phosphorylation in complement activation induced by renal IRI by combining phosphoproteomic approaches and protein validation, which hopefully could provide novel insights into the pathological mechanisms of IRI.

Sustainable Nonwoven Scaffolds Engineered with Recycled Carbon Fiber for Enhanced Biocompatibility and Cell Interaction: From Waste to Health

Carbon fibers, driven by ever-increasing demand, are contributing to a continuous rise in the generation of waste and byproducts destined for landfills or incineration. Recycling carbon fibers presents a promising strategy for reducing carbon emissions and conserving resources, thus contributing to more sustainable waste management practices. Discovering applications of recycled carbon fibers (rCFs) would inevitably accelerate the targeted integration of sustainable materials, fostering a circular economy. Herein, we have engineered rCF-based needlepunched nonwoven scaffolds and their blends with polypropylene (PP) fibers, providing the first example of investigating their interactions with human lung epithelial cells (Calu-3) and murine fibroblast cells (NIH/3T3). To promote the adsorption of extracellular matrix proteins such as laminin, these three-dimensional (3D) nonwoven scaffolds are designed and developed to feature tunable porous characteristics and wetting properties. Although cell adhesion and laminin adsorption are minimal on PP fibers, cells are preferentially organized on the rCFs. These nonwovens, composed exclusively of rCFs or their blends with PP fibers, exhibit no cytotoxic effects, with both cell types showing proliferation on the scaffolds and a progressive increase in cell numbers over time. Cell viability and apoptosis assays are also employed to comprehensively evaluate biocompatibility. Thus, our study proves rCF-based nonwoven scaffolds as potential candidates for artificial lung tissue scaffolds.

Crip2 affects vascular development by fine-tuning endothelial cell aggregation and proliferation

Endothelial cell adhesion and migration are crucial to various biological processes, including vascular development. The identification of factors that modulate vascular development through these cell functions has emerged as a prominent focus in cardiovascular research. Crip2 is known to play a crucial role in cardiac development, yet its involvement in vascular development and the underlying mechanism remains elusive. In this study, we revealed that Crip2 is expressed predominantly in the vascular system, particularly in the posterior cardinal vein and caudal vein plexus intersegmental vein. Upon Crip2 loss, the posterior cardinal vein plexus and caudal vein plexus are hypoplastic, and endothelial cells exhibit aberrant aggregation. In human umbilical vein endothelial cells (HUVECs), CRIP2 interacts with the cytoskeleton proteins KRT8 and VIM. The absence of CRIP2 negatively regulates their expression, thereby fine-tuning cytoskeleton formation, resulting in a hyperadhesive phenotype. Moreover, CRIP2 deficiency perturbs the VEGFA/CDC42 signaling pathway, which in turn diminishes the migrating capacity of HUVECs. Furthermore, the loss of CRIP2 impairs cell proliferation by affecting its interaction with SRF through PDE10A/cAMP and PDGF/JAK/STAT/SRF signaling. Collectively, our findings delineate a crucial role for CRIP2 in controlling the migration, adhesion and proliferation of endothelial cells, thereby contributing to vascular development in zebrafish. These insights may provide a deeper understanding of the etiology of cardiovascular disorders.

Optimizing Jasplakinolide delivery in rhabdomyosarcoma cells using pulsed electric fields (PEFs) for enhanced therapeutic impact

This study explores the combination of jasplakinolide with electroporation (JSP + EP), a method enhancing targeted molecule delivery. CHO-K1 (Chinese hamster ovarian), C2C12 (mouse myoblast), and RD (rhabdomyosarcoma) cells were treated with jasplakinolide (50 nM) in HEPES buffer and exposed to electrical pulses (0.8-1.2 kV/cm). Cell viability was measured via the MTS assay, cytoskeleton structure was assessed with confocal microscopy, and docking studies examined jasplakinolide-actin interactions. The combination of jasplakinolide and electric pulses synergistically affected RMS cells (Rhabdomyosarcoma), causing significant cytoskeletal changes and reduced viability. Docking studies revealed that jasplakinolide interacts with both monomeric and filamentous actin, highlighting a dual mechanism. Confocal imaging showed substantial actin cytoskeleton disruption in cancer cells, with minimal effects on normal cells. Jasplakinolide combined with electric pulses can specifically target cancer cells with less cytotoxicity to normal cells, potentially reducing side effects following the clinical procedure.

Temperature-responsive properties of pH-sensitive poly(methacrylic acid)-grafted brush coatings with controlled wettability for cell culture

Poly(methacrylic acid) (PMAA) is a well-known pH-responsive polymer with under-explored temperature-responsive properties. This study investigated the temperature-responsive properties of PMAA-grafted brush coatings, synthesized via the SI-ATRP polymerization of sodium methacrylate (NaMAA) and methacrylic acid (MAA) on glass surfaces. Distinct water contact angles were observed for PMAA brush coatings fabricated from NaMAA (38 deg) and MAA (60 deg) solutions. The reduced wettability of PMAA brushes from MAA indicates a reduced exposure of the hydrophilic moieties acquired during synthesis, which is postulated to occur with a lower grafting density. PMAA brush coatings showed a lower critical solution temperature (LCST), characterized by changes in wettability and thickness; however, this transition was not observed after immersion in various pH buffer solutions. Although inhibited growth of cells cultured on PMAA brushes was previously reported, we observed that the increased hydrophobicity of PMAA coatings from MAA resulted in excellent biocompatibility, demonstrated by growth and viability of dermal fibroblast cultures, making them prospective for biomedical applications. However, the LCST transition of these coatings did not induce temperature-controlled changes in protein (BSA) adsorption and cell (fibroblast) morphology.

Redox regulation of focal adhesions

Focal adhesions (FAs), multi-protein complexes that link the extracellular matrix to the intracellular cytoskeleton, are key mediators of cell adhesion, migration, and proliferation. These dynamic structures act as mechanical sensors, transmitting stimuli from the extracellular to intracellular environment activating in this way signaling pathways and enabling cells to adapt to environmental changes. As such, FAs are critical for tissue organization and serve as hubs governing cell spatial arrangement within the organism. The assembly, reactivity, and functional regulation of FAs are tightly controlled by post-translational modifications, including redox modulation by reactive oxygen and nitrogen species. Increasing evidence suggests that redox signaling plays a pivotal role in both the physiological and pathological functions of FAs and their downstream processes. Redox regulation affects various components of the FA complex, including integrins, focal adhesion kinase 1 (FAK1), SRC, adapter proteins, and cytoskeletal elements. In this review, we provide an updated overview of the complex interplay between redox signaling and post-translational modifications in FAs. We explore how redox reactions influence the structure, dynamics, and function of FAs, shedding light on their broader implications in health and disease.

Vinculin: A new target for the diagnosis and treatment of disease

Vinculin, a crucial adhesion plaque protein, plays a significant role in cell morphology and tissue development. Dysregulation of focal adhesion proteins has been linked to numerous diseases, including cardiovascular conditions, gastrointestinal disorders, and cancer. Recent studies increasingly highlight vinculin's involvement in the progression of these diseases; however, a comprehensive review remains lacking. Therefore, an in-depth and timely review is essential to consolidate the latest findings on vinculin's role in disease mechanisms. This study aims to examine how vinculin coordinates a complex network of signaling pathways across various pathological contexts.

Aflatoxin B1 Exposure Suppresses the Migration of Dendritic Cells by Reshaping the Cytoskeleton

Exposure to Aflatoxin B1 (AFB1) is considered a significant risk factor for human diseases, including the immune function impairment of immune cells. Dendritic cells (DCs), as essential antigen-presenting cells, play a pivotal role in bridging innate and adaptive immunity. However, the impact of AFB1 exposure on DCs has not been fully elucidated. In this study, we investigated the effects of AFB1 exposure on the migration ability of DCs and its underlying action model. Initially, we observed that AFB1 exposure inhibited the survival of DCs and altered their cellular morphology. Further investigation revealed that AFB1 promotes cell adhesion and inhibits DC migration by modulating the expression of cell adhesion molecules. Additionally, our findings indicated that cytoskeletal remodeling plays a crucial role in these processes. Experimental techniques such as immunofluorescence and RNA sequencing confirmed that AFB1 exposure regulates the expression of cytoskeleton-related genes. Moreover, we found that the perturbation of the gene expression profile through AFB1 exposure is associated with cell communication. Collectively, our study findings demonstrate that AFB1 can disrupt the expression of cytoskeleton- and adhesion-related molecules in DCs, thereby altering cell morphology and migration. These insights could provide new perspectives for further understanding the immunosuppressive effects of AFB1 and developing therapeutic strategies for diseases associated with AFB1 exposure.

Biofunctionalization of Collagen Barrier Membranes with Bone-Conditioned Medium, as a Natural Source of Growth Factors, Enhances Osteoblastic Cell Behavior

A key principle of guided bone regeneration (GBR) is the use of a barrier membrane to prevent cells from non-osteogenic tissues from interfering with bone regeneration in patients with hard tissue deficiencies. The aim of the study was to investigate whether the osteoinductive properties of bone-conditioned medium (BCM) obtained from cortical bone chips harvested at the surgical site can be transferred to a native bilayer collagen membrane (nbCM). BCM extracted within 20 or 40 min, which corresponds to a typical implant surgical procedure, and BCM extracted within 24 h, which corresponds to BCM released from the autologous bone chips in situ, contained significant and comparable amounts of TGF-β1, IGF-1, FGF-2, VEGF-A, and IL-11. Significant (p < 0.001) quantities of BMP-2 were only detected in the 24-h BCM preparation. The bioactive substances contained in the BCM were adsorbed to the nbCMs with almost 100% efficiency. A fast but sequential release of all investigated proteins occurred within 6-72 h, reflecting their stepwise involvement in the natural regeneration process. BCM-coated nbCM significantly (p < 0.05) increased the migratory, adhesive, and proliferative capacity of primary human bone-derived cells (hBC), primary human periodontal ligament cells (hPDLC), and an osteosarcoma-derived osteoblastic cell line (MG-63) compared to cells cultured on BCM-free nbCM. The high proliferative rates of MG-63 cells cultured on BCM-free nbCM were not further potentiated by BCM, indicating that BCM-coated nbCM has no detrimental effects on cancer cell growth. BCM-coated nbCM caused significant (p < 0.05) induction of early osteogenic marker gene expression and alkaline phosphatase activity, suggesting an important role of BCM-functionalized nbCM in the initiation of osteogenesis. The 24-h BCM loaded on the nbCM was the only BCM preparation that caused significant induction of late osteogenic marker gene expression. Altogether, our data define the pre-activation of collagen membranes with short-term-extracted BCM as a potential superior modality for treating hard tissue deficiencies via GBR.

Loss of Cathepsin K impairs collagen biogenesis and enhances actin polymerization in trabecular meshwork

Trabecular meshwork (TM) dysfunction and extracellular matrix (ECM) dysregulation contribute to increased intraocular pressure (IOP) in primary open-angle glaucoma (POAG). Earlier, we provide a proof-of-concept study identifying the regulation and the role of Cathepsin K (CTSK), a potent collagenase, in ECM homeostasis, actin bundling, and IOP regulation. Better understanding of the loss of CTSK function in TM remains unclear. Using siRNA-mediated knockdown of CTSK (siCTSK) in human TM cells, this study investigated the role of CTSK in actin and ECM homeostasis using an unbiased proteomics approach. Loss of CTSK significantly disrupted collagen biogenesis and ECM homeostasis. CTSK depletion also increased intracellular calcium levels, with proteomics data suggesting possible involvement of calcium-regulatory proteins. Additionally, PRKD1 activation enhanced actin polymerization through the LIMK1/SSH1/cofilin pathway, promoting focal adhesion maturation. Despite increased apoptotic markers (CASP3, CASP7, TRADD, PPM1F), caspase 3/7 activation was not induced, suggesting apoptosis-independent cellular remodeling. Notably, RhoQ and myosin motor proteins were significantly downregulated, indicating altered mechanotransduction in TM cells. These findings highlight the role of CTSK in maintaining ECM homeostasis, calcium signaling, and cytoskeletal regulation in TM. Its depletion induces actin polymerization, which may influence aqueous humor outflow. Targeting CTSK-related pathways may provide novel therapeutic strategies for regulating IOP and preventing glaucoma progression.

Vinculin-Arp2/3 interaction inhibits branched actin assembly to control migration and proliferation

Vinculin is a mechanotransducer that reinforces links between cell adhesions and linear arrays of actin filaments upon myosin-mediated contractility. Both adhesions to the substratum and neighboring cells, however, are initiated within membrane protrusions that originate from Arp2/3-nucleated branched actin networks. Vinculin has been reported to interact with the Arp2/3 complex, but the role of this interaction remains poorly understood. Here, we compared the phenotypes of vinculin knock-out (KO) cells with those of knock-in (KI-P878A) cells, where the point mutation P878A that impairs the Arp2/3 interaction is introduced in the two vinculin alleles of MCF10A mammary epithelial cells. The interaction of vinculin with Arp2/3 inhibits actin polymerization at membrane protrusions and decreases migration persistence of single cells. In cell monolayers, vinculin recruits Arp2/3 and the vinculin-Arp2/3 interaction participates in cell-cell junction plasticity. Through this interaction, vinculin controls the decision to enter a new cell cycle as a function of cell density.

A theoretical model for focal adhesion and cytoskeleton formation in non-motile cells

To function and survive cells need to be able to sense and respond to their local environment through mechanotransduction. Crucially, mechanical and biochemical perturbations initiate cell signalling cascades, which can induce responses such as growth, apoptosis, proliferation and differentiation. At the heart of this process are actomyosin stress fibres (SFs), which form part of the cell cytoskeleton, and focal adhesions (FAs), which bind this cytoskeleton to the extra-cellular matrix (ECM). The formation and maturation of these structures (connected by a positive feedback loop) is pivotal in non-motile cells, where SFs are generally of ventral type, interconnecting FAs and producing isometric tension. In this study we formulate a one-dimensional bio-chemo-mechanical continuum model to describe the coupled formation and maturation of ventral SFs and FAs. We use a set of reaction-diffusion-advection equations to describe three sets of biochemical events: the polymerisation of actin and subsequent bundling into activated SFs; the formation and maturation of cell-substrate adhesions; and the activation of signalling proteins in response to FA and SF formation. The evolution of these key proteins is coupled to a Kelvin-Voigt viscoelastic description of the cell cytoplasm and the ECM. We employ this model to understand how cells respond to external and intracellular cues in vitro and are able to reproduce experimentally observed phenomena including non-uniform cell striation and cells forming weaker SFs and FAs on softer substrates.

Combinational regenerative inductive effect of bio-adhesive hybrid hydrogels conjugated with hiPSC-derived myofibers and its derived EVs for volumetric muscle regeneration

In regenerative medicine, extracellular vesicles (EVs) possess the potential to repair injured cells by delivering modulatory factors. However, the therapeutic effect of EVs in large-scale tissue defects, which are subject to prolonged timelines for tissue architecture and functional restoration, remains poorly understood. In this study, we introduce EVs and cell-tethering hybrid hydrogels composed of tyramine-conjugated gelatin (GelTA) that can be in-situ crosslinked with EVs derived from human induced pluripotent stem cell-derived myofibers (hiPSC-myofibers) and hiPSC-muscle precursor cells. This hybrid hydrogel sustains the release of EVs and provides a beneficial nano-topography and mechanical properties for creating a favorable extracellular matrix. Secreted EVs from the hiPSC-myofibers contain specific microRNAs, potentially improving myogenesis and angiogenesis. Herein, we demonstrate increased myogenic markers and fusion/differentiation indexes through the combinatory effects of EVs and integrin-mediated adhesions in the 3D matrix. Furthermore, we observe a unique impact of EVs, which aid in maintaining the viability and phenotype of myofibers under harsh environments. The hybrid hydrogel in-situ crosslinked with hiPSCs and EVs is facilely used to fabricate large-scale muscle constructs by the stacking of micro-patterned hydrogel domains. Later, we confirmed a combinational effect, whereby muscle tissue regeneration and functional restoration were improved, via an in vivo murine volumetric muscle loss model.

Focal adhesions, reticular adhesions, flat clathrin lattices: what divides them, what unites them?

The majority of cells within multicellular organisms requires anchorage to their surroundings in the form of cell-cell or cell-matrix adhesions. In regards to cell-matrix adhesions, the transmembrane receptors of the integrin family have long been recognized as the central scaffold around which these adhesion complexes are built. Via their extracellular domains integrins bind extracellular matrix ligands while their intracellular tails interact with a plethora of proteins that link integrin-based adhesions to the cytoskeleton and turn them also into important signaling platforms. Depending on the specific intracellular interactome of the integrins, different types of integrin adhesion complexes have been classified. The best-studied ones are the focal adhesions, in which integrins become firmly linked to contractile actomyosin fibers, allowing force transduction. But integrins also form an integral part of adhesion structures that lack the strong actomyosin link and are enriched in endocytic proteins. These have been named reticular adhesions, flat clathrin lattices, or clathrin plaques. Initially, the different types of integrin adhesion complexes have been viewed as discrete entities with their own separate life cycles. However, in the past years it has become more and more apparent how closely intertwined they are. In fact, it was shown that they can trigger each other's biogenesis or can even directly convert into each other. Here, we describe similarities as well as differences between integrin adhesion complexes, focusing on the versatile αvβ5 integrins, and discuss the recently discovered close links and interconversion modes between the different αvβ5 integrin adhesion types.

Programmable soft DNA hydrogels stimulate cellular endocytic pathways and proliferation

Hydrogels are pivotal in tissue engineering, regenerative medicine, and drug delivery applications. Existing hydrogel platforms are not easily customizable and often lack precise programmability, making them less suited for 3D tissue culture and programming of cells. DNA molecules stand out among other promising biomaterials due to their unparalleled precision, programmability, and customization. In this study, we introduced a palette of novel cellular scaffolding platforms made of pure DNA-based hydrogel systems while improving the shortcomings of the existing platforms. We showed a quick and easy one step synthesis of DNA hydrogels using thermal annealing based on sequence specific hybridization strategy. We also demonstrated the formation of multi-armed branched supramolecular scaffolds with custom mechanical stiffness, porosity, and network density by increasing or decreasing the number of branching arms. These mechanically tuneable DNA hydrogels proved to be a suitable suitable platform for modulating the physiological processes of retinal pigment epithelial cells (RPE1). In-vitro studies showed dynamic changes at multiple levels, ranging from a change in morphology to protein expression patterns, enhanced membrane traffic, and proliferation. The soft DNA hydrogels explored here are mechanically compliant and pliable, thus excellently suited for applications in cellular programming and reprogramming. This research lays the groundwork for developing a DNA hydrogel system with a higher dynamic range of stiffness, which will open exciting avenues for tissue engineering and beyond.

Graphene SU-8 Platform for Enhanced Cardiomyocyte Maturation and Intercellular Communication in Cardiac Drug Screening

Cell culture substrates designed for myocardial applications are pivotal in promoting the maturation and functional integration of cardiomyocytes. However, traditional in vitro models often inadequately mimic the diverse biochemical signals and electrophysiological properties of mature cardiomyocytes. Herein, we propose the application of monolayer graphene, transferred onto SU-8 cantilevers integrated with a microelectrode array, to evaluate its influence on the structural, functional, and electro-mechano-physiological properties of cardiomyocytes. The monolayer graphene, prepared using chemical vapor deposition, is adeptly transferred to the target substrates via thermal release tape. The electrical conductivity of these graphene-enhanced SU-8 substrates is about 1600 S/cm, markedly surpassing that of previously reported cell culture substrates. Immunofluorescence staining and Western blot analyses reveal that the electrically conductive graphene significantly enhances cardiomyocyte maturation and cardiac marker expression compared to bare SU-8 substrates. Cardiomyocytes cultured on graphene-transferred substrates exhibit conduction velocity approximately 3.4 times greater than that of the control group. Such improvements in cardiac marker expression, mechano-electrophysiological performance lead to better responsiveness to cardiovascular drugs, such as Verapamil and Isoproterenol. While the graphene monolayer does not fully replicate the complex environment found in native cardiac tissue, its use on SU-8 substrates offers a feasible approach for accelerating cardiomyocyte maturation and facilitating drug screening applications.

Comparison of the Effects of Four Laser Wavelengths on Medication-Related Osteonecrosis of the Jaw (MRONJ) in a Murine Model: An In Vivo Photobiomodulation Study

Background: This study aims to investigate the effectiveness of lasers at various wavelengths in treating medication-related osteonecrosis of the jaw (MRONJ) using biochemical, clinical scoring, micro CT analysis, and histopathological methods. The study follows the ARRIVE guidelines to ensure robust and transparent research. Methods: In our study, there were 6 groups, including one SHAM group, one CONTROL group, and four experimental groups, with 8 rats in each individual group. Each rat received antiresorptive drug intraperitoneally for 4 weeks and then had the left second molar in the mandible extracted. All animals were sacrificed at the end of the 12th week. In the experimental groups, lasers at wavelengths of 405nm, 445nm, 660nm, and 808nm were applied to the animals. Parameters such as serum vitamin D levels, bone density and bone volume at the extraction site, new bone formation, dead bone count, inflammatory cell count, and epithelial regeneration were examined. Additionally, clinical scoring was conducted after sacrifice. The laser parameters included power density, area, time, fluence, and mode (continuous wave), and the light was administered using a fiber with a Gaussian profile. Statistical analyses were performed with the NCSS (Number Cruncher Statistical System) 2007 Statistical Software (Utah, USA) package program. The results were evaluated at the p<0.05 significance level. Results: According to the results obtained from our study, new bone formation in all experimental groups was significantly higher than in the SHAM and CONTROL groups. Furthermore, the 660nm and 808nm wavelengths increased serum vitamin D levels significantly. The most successful outcomes were observed in clinical scoring, dead bone count, epithelial cell regeneration, and bone density in the 660nm and 808nm wavelength groups. Conclusions: The combined use of lasers at 660nm and 808nm wavelengths may yield successful results in treating MRONJ.

Enhancing Titanium Osteoconductivity by Alkali-Hot Water Treatment

Titanium and its alloys are essential in orthopedic and dental treatments owing to their high strength, corrosion resistance, and superior biocompatibility compared with those of other metals. However, titanium alloys are bioinert. Previous studies have indicated that alkali treatment (AT) is a straightforward method to create a surface oxidization layer on titanium, thereby improving its bioactivity. Herein, alkali-hot water pretreatment was used to enhance the osteoconductivity of titanium and to identify a simple and efficient means of enhancing the interaction between osteoblasts and implants for clinical applications. Commercial pure titanium plates were ground (CP Ti) and subjected to alkali solution and hot water treatments (AWT). Single-process CP Ti specimens were prepared via either AT or hot water treatment (WT). Network-like structural features were observed in the AT specimens and were further refined and densified in the AWT specimens. Water contact angle testing revealed that the hydrophilicity of the titanium specimen (80° for CP Ti) increased by 19° for the AT specimens but decreased by 59° for the AWT specimens. Mouse preosteoblasts (MC3T3-E1 cells) were used for in vitro evaluation. After 24 h of culturing, the number of attached MC3T3-E1 cells on the AWT specimens was 1.5 times larger than that on the CP Ti specimens, suggesting that the alkali-hot water treatment enhanced the initial cell attachment. Cell proliferation evaluation indicated that fewer cells were detected in the AT and AWT specimens compared with those in the CP Ti or WT specimens. However, osteogenic differentiation evaluation on day 10 revealed a 1.5-fold higher alkaline phosphatase expression in cells cultured on the AWT specimens than in cells cultured on the CP Ti specimens. These findings demonstrate the good cytocompatibility and osteoconductivity of AWT Ti, highlighting its benefits in orthopedics and dental treatments.

Vasoactive intestinal peptide exerts an osteoinductive effect in human mesenchymal stem cells

Several neuropeptides present in bone tissues, produced by nerve fibers and bone cells, have been reported to play a role in regulating the fine-tuning of osteoblast and osteoclast functions to maintain bone homeostasis. This study aims to characterize the influence of the neuropeptide vasoactive intestinal peptide (VIP) on the differentiation process of human mesenchymal stem cells (MSCs) into osteoblasts and on their anabolic function. We describe the mRNA and protein expression profile of VIP and its receptors in MSCs as they differentiate into osteoblasts, suggesting the presence of an autocrine signaling pathway in these cells. Our findings reveal that VIP enhances the expression of early osteoblast markers in MSCs under osteogenic differentiation and favors both bone matrix formation and proper cytoskeletal reorganization. Finally, our data suggest that VIP could be exerting a direct modulatory role on the osteoblast to osteoclast signaling by downregulating the receptor activator of nuclear factor-κB ligand/osteoprotegerin ratio. These results highlight the potential of VIP as an osteoinductive differentiation factor, emerging as a key molecule in the maintenance of human bone homeostasis.

A multicellular developmental program in a close animal relative

All animals develop from a single-celled zygote into a complex multicellular organism through a series of precisely orchestrated processes1,2. Despite the remarkable conservation of early embryogenesis across animals, the evolutionary origins of how and when this process first emerged remain elusive. Here, by combining time-resolved imaging and transcriptomic profiling, we show that single cells of the ichthyosporean Chromosphaera perkinsii-a close relative that diverged from animals about 1 billion years ago3,4-undergo symmetry breaking and develop through cleavage divisions to produce a prolonged multicellular colony with distinct co-existing cell types. Our findings about the autonomous and palintomic developmental program of C. perkinsii hint that such multicellular development either is much older than previously thought or evolved convergently in ichthyosporeans.

FUT3 promotes gastric cancer cell migration by synthesizing Lea on ITGA6 and GLG1, affecting adhesion and vesicle distribution

AIMS

Lewis antigen plays an important role in the progression of gastric cancer (GC), FUT3 is a key enzyme in the synthesis of Lewis antigen, but the molecular mechanism of its promotion of GC progression remains unclear.

MAIN METHODS

We used Lea-antibody capturing coupled with mass spectrometry to identify the target proteins of FUT3, immunofluorescence (IF), molecular biology and cell function experiments were conducted to clarify the molecular mechanism of FUT3 promoting the migration and invasion of GC cells by regulating Lea glycosylation on ITGA6 and GLG1.

KEY FINDINGS

FUT3 promote migration and invasion of GC cells. FUT3 silencing in GC cells led to the aggregation of integrin α6β4 on the plasma membrane, associated with focal adhesion and hemidesmosome, and decreased GLG1 distribution in cellular vesicles. IGP analysis revealed Lea structure in 10 N-glycans of 2 glycosites for ITGA6 and 31 N-glycans of 4 glycosites for GLG1. Silencing ITGA6 promoted migration and invasion, while silencing GLG1 inhibited these processes in GC cells, regulated by FUT3-mediated Lea synthesis.

SIGNIFICANCE

In conclusion, FUT3's promotion of GC cell migration and invasion is attributed to Lea synthesis on ITGA6, impacting cell adhesion, and on GLG1, influencing distribution in intracellular vesicles. These findings may contribute to developing novel therapeutic targets for inhibiting or controlling the metastatic behavior of GC cells and enhancing our understanding of Lea's role in regulating protein functions.

3D-printed biomimetic bone scaffold loaded with lyophilized concentrated growth factors promotes bone defect repair by regulation the VEGFR2/PI3K/AKT signaling pathway

This study investigates the effects of concentrated growth factors (CGF) and bone substitutes on the proliferation and differentiation of bone marrow mesenchymal stem cells (BMSCs), as well as the development of a novel 3D-printed biomimetic bone scaffold. Based on the structure of cancellous bone, 3D-printed bionic bone with sustainable release of growth factors and Ca2+ was prepared. Using BMSCs and EA.hy926 in co-culture with the bionic bone scaffold, experimental results demonstrate that this bionic structural design enhances cell proliferation and adhesion, and that the bionic bone possesses the ability to promote bone and vascular regeneration directly. Transcriptomics, western blot analysis, and flow cytometry are employed to investigate the effects of CGF and Ca2+ on the signaling pathways of BMSCs. The study reports that vascular endothelial growth factor (VEGF) released by CGF activated VEGFR2 on BMSCs, leading to Ca2+ influx and activation of the PI3K/AKT signaling pathway, thereby influencing osteogenesis. Animal experiments confirm the ability of the bionic bone to promote osteogenesis in vivo, and its unique degradation pattern accelerates the in vivo repair of bone defects. In conclusion, this study presents a novel biomimetic strategy and, for the first time, explores the potential mechanism by which VEGF and Ca2+ regulate BMSCs differentiation through the VEGFR2/PI3K/AKT signaling pathway. These insights offer a new perspective for the development of innovative bone substitute materials.

Mechanosensitive recruitment of Vinculin maintains junction integrity and barrier function at epithelial tricellular junctions

Apical cell-cell junctions, including adherens junctions and tight junctions, adhere epithelial cells to one another and regulate selective permeability at both bicellular junctions and tricellular junctions (TCJs). Although several specialized proteins are known to localize at TCJs, it remains unclear how actomyosin-mediated tension transmission at TCJs contributes to the maintenance of junction integrity and barrier function at these sites. Here, utilizing the embryonic epithelium of gastrula-stage Xenopus laevis embryos, we define a mechanism by which the mechanosensitive protein Vinculin helps anchor the actomyosin network at TCJs, thus maintaining TCJ integrity and barrier function. Using an optogenetic approach to acutely increase junctional tension, we find that Vinculin is mechanosensitively recruited to apical junctions immediately surrounding TCJs. In Vinculin knockdown (KD) embryos, junctional actomyosin intensity is decreased and becomes disorganized at TCJs. Using fluorescence recovery after photobleaching (FRAP), we show that Vinculin KD reduces actin stability at TCJs and destabilizes Angulin-1, a key tricellular tight junction protein involved in regulating barrier function at TCJs. When Vinculin KD embryos are subjected to increased tension, TCJ integrity is not maintained, filamentous actin (F-actin) morphology at TCJs is disrupted, and breaks in the signal of the tight junction protein ZO-1 signal are detected. Finally, using a live imaging barrier assay, we detect increased barrier leaks at TCJs in Vinculin KD embryos. Together, our findings show that Vinculin-mediated actomyosin organization is required to maintain junction integrity and barrier function at TCJs and reveal new information about the interplay between adhesion and barrier function at TCJs.

Role of Cytoskeletal Elements in Regulation of Synaptic Functions: Implications Toward Alzheimer's Disease and Phytochemicals-Based Interventions

Alzheimer's disease (AD), a multifactorial disease, is characterized by the accumulation of neurofibrillary tangles (NFTs) and amyloid beta (Aβ) plaques. AD is triggered via several factors like alteration in cytoskeletal proteins, a mutation in presenilin 1 (PSEN1), presenilin 2 (PSEN2), amyloid precursor protein (APP), and post-translational modifications (PTMs) in the cytoskeletal elements. Owing to the major structural and functional role of cytoskeletal elements, like the organization of axon initial segmentation, dendritic spines, synaptic regulation, and delivery of cargo at the synapse; modulation of these elements plays an important role in AD pathogenesis; like Tau is a microtubule-associated protein that stabilizes the microtubules, and it also causes inhibition of nucleo-cytoplasmic transportation by disrupting the integrity of nuclear pore complex. One of the major cytoskeletal elements, actin and its dynamics, regulate the dendritic spine structure and functions; impairments have been documented towards learning and memory defects. The second major constituent of these cytoskeletal elements, microtubules, are necessary for the delivery of the cargo, like ion channels and receptors at the synaptic membranes, whereas actin-binding protein, i.e., Cofilin's activation form rod-like structures, is involved in the formation of paired helical filaments (PHFs) observed in AD. Also, the glial cells rely on their cytoskeleton to maintain synaptic functionality. Thus, making cytoskeletal elements and their regulation in synaptic structure and function as an important aspect to be focused for better management and targeting AD pathology. This review advocates exploring phytochemicals and Ayurvedic plant extracts against AD by elucidating their neuroprotective mechanisms involving cytoskeletal modulation and enhancing synaptic plasticity. However, challenges include their limited bioavailability due to the poor solubility and the limited potential to cross the blood-brain barrier (BBB), emphasizing the need for targeted strategies to improve therapeutic efficacy.

Nanoscale dynamics of the cadherin-catenin complex bound to vinculin revealed by neutron spin echo spectroscopy

We report a neutron spin echo (NSE) study of the nanoscale dynamics of the cell-cell adhesion cadherin-catenin complex bound to vinculin. Our measurements and theoretical physics analyses of the NSE data reveal that the dynamics of full-length α-catenin, β-catenin, and vinculin residing in the cadherin-catenin-vinculin complex become activated, involving nanoscale motions in this complex. The cadherin-catenin complex is the central component of the cell-cell adherens junction (AJ) and is fundamental to embryogenesis, tissue wound healing, neuronal plasticity, cancer metastasis, and cardiovascular health and disease. A highly dynamic cadherin-catenin-vinculin complex provides the molecular dynamics basis for the flexibility and elasticity that are necessary for the AJs to function as force transducers. Our theoretical physics analysis provides a way to elucidate these driving nanoscale motions within the complex without requiring large-scale numerical simulations, providing insights not accessible by other techniques. We propose a three-way "motorman" entropic spring model for the dynamic cadherin-catenin-vinculin complex, which allows the complex to function as a flexible and elastic force transducer.

β2 integrins impose a mechanical checkpoint on macrophage phagocytosis

Phagocytosis is an intensely physical process that depends on the mechanical properties of both the phagocytic cell and its chosen target. Here, we employed differentially deformable hydrogel microparticles to examine the role of cargo rigidity in the regulation of phagocytosis by macrophages. Whereas stiff cargos elicited canonical phagocytic cup formation and rapid engulfment, soft cargos induced an architecturally distinct response, characterized by filamentous actin protrusions at the center of the contact site, slower cup advancement, and frequent phagocytic stalling. Using phosphoproteomics, we identified β2 integrins as critical mediators of this mechanically regulated phagocytic switch. Macrophages lacking β2 integrins or their downstream effectors, Talin1 and Vinculin, exhibited specific defects in phagocytic cup architecture and selective suppression of stiff cargo uptake. We conclude that integrin signaling serves as a mechanical checkpoint during phagocytosis to pair cargo rigidity to the appropriate mode of engulfment.

Expression of opsin and visual cycle-related enzymes in fetal rat skin keratinocytes and cellular response to blue light

The mechanism by which the skin, a non-visual tissue, responds to light remains unknown. To date, opsin expression has been demonstrated in keratinocytes, melanocytes, and fibroblasts, all of which are skin-derived cells. In this study, we examined whether the visual cycle, by which opsin activity is maintained, is present in skin keratinocytes. We also identified the wavelengths of light to which opsin in keratinocytes responds and explored their effects on skin keratinocytes. The fetal rat skin keratinocytes used in this study expressed OPN2, 3, and 5 in addition to enzymes involved in the visual cycle, and all-trans-retinal, which is produced by exposure to light, was reconverted to 11-cis-retinal, resulting in opsin activation. Using the production of all-trans-retinal after light exposure as an indicator, we discovered that keratinocytes responded to light at 450 nm. Furthermore, actin alpha cardiac muscle 1 expression in keratinocytes was enhanced and cell migration was suppressed by exposure to light at these wavelengths. These results indicate that keratinocytes express various opsins and have a visual cycle that keeps opsin active. Moreover, keratinocytes were shown to respond to the blue/UV region of the light spectrum, suggesting that opsin plays a role in the light response of the skin.

Role of LMO7 in cancer (Review)

Cancer constitutes a multifaceted ailment characterized by the dysregulation of numerous genes and pathways. Among these, LIM domain only 7 (LMO7) has emerged as a significant player in various cancer types, garnering substantial attention for its involvement in tumorigenesis and cancer progression. This review endeavors to furnish a comprehensive discourse on the functional intricacies and mechanisms of LMO7 in cancer, with a particular emphasis on its potential as both a therapeutic target and prognostic indicator. It delves into the molecular attributes of LMO7, its implications in cancer etiology and the underlying mechanisms propelling its oncogenic properties. Furthermore, it underscores the extant challenges and forthcoming prospects in targeting LMO7 for combating cancer.

Utilizing machine learning to integrate single-cell and bulk RNA sequencing data for constructing and validating a novel cell adhesion molecules related prognostic model in gastric cancer

BACKGROUND

Cell adhesion molecules (CAMs) play a vital role in cell-cell interactions, immune response modulation, and tumor cell migration. However, the unique role of CAMs in gastric cancer (GC) remains largely unexplored.

METHODS

This study characterized the genetic alterations and mRNA expression of CAMs. The role of CD34, a representative molecule, was validated in 375 GC tissues. The activity of the CAM pathway was further tested using single-cell and bulk characterization. Next, data from 839 patients with GC from three cohorts was analyzed using univariate Cox and random survival forest methods to develop and validate a CAM-related prognostic model.

RESULTS

Most CAM-related genes exhibited multi-omics alterations and were associated with clinical outcomes. There was a strong correlation between increased CD34 expression and advanced clinical staging (P = 0.026), extensive vascular infiltration (P = 0.003), and unfavorable prognosis (Log-rank P = 0.022). CD34 expression was also found to be associated with postoperative chemotherapy and tumor immunotherapy response. Furthermore, the CAM pathway was significantly activated and mediated poor prognosis. Additionally, eight prognostic signature genes (PSGs) were identified in the training cohort. There was a substantial upregulation of the expression of immune checkpoints and a pronounced infiltration of immune cells in GC tissues with high PSG score, which is consistent with the prediction of increased sensitivity to immunotherapy. Moreover, 9 compounds from the CTRPv2 database and 13 from the Profiling Relative Inhibition Simultaneously in Mixture (PRISM) database were identified as potential therapeutic drugs for patients with GC with high PSG score.

CONCLUSION

Thorough understanding of CAM pathways regulation and the innovative PSG score model hold significant implications for medical diagnosis, potentially enhancing personalized treatment strategies and improving patient outcomes in GC management.

Granulosa Cell-Layer Stiffening Prevents Escape of Mural Granulosa Cells from the Post-Ovulatory Follicle

Ovulation is vital for successful reproduction. Following ovulation, cumulus cells and oocyte are released, while mural granulosa cells (mGCs) remain sequestered within the post-ovulatory follicle to form the corpus luteum. However, the mechanism underlying the confinement of mGCs has been a longstanding mystery. Here, in vitro and in vivo evidence is provided demonstrating that the stiffening of mGC-layer serves as an evolutionarily conserved mechanism that prevents mGCs from escaping the post-ovulatory follicles. The results from spatial transcriptome analysis and experiments reveal that focal adhesion assembly, triggered by the LH (hCG)-cAMP-PKA-CREB signaling cascade, is necessary for mGC-layer stiffening. Disrupting focal adhesion assembly through RNA interference results in stiffening failure, mGC escape, and the subsequent development of an abnormal corpus luteum characterized by decreased cell density or cavities. These findings introduce a novel concept of "mGC-layer stiffening", shedding light on the mechanism that prevents mGC escape from the post-ovulatory follicle.

The ability of the LIMD1 and TRIP6 LIM domains to bind strained f-actin is critical for their tension dependent localization to adherens junctions and association with the Hippo pathway kinase LATS1

A key step in regulation of Hippo pathway signaling in response to mechanical tension is recruitment of the LIM domain proteins TRIP6 and LIMD1 to adherens junctions. Mechanical tension also triggers TRIP6 and LIMD1 to bind and inhibit the Hippo pathway kinase LATS1. How TRIP6 and LIMD1 are recruited to adherens junctions in response to tension is not clear, but previous studies suggested that they could be regulated by the known mechanosensory proteins α-catenin and vinculin at adherens junctions. We found that the three LIM domains of TRIP6 and LIMD1 are necessary and sufficient for tension-dependent localization to adherens junctions. The LIM domains of TRIP6, LIMD1, and certain other LIM domain proteins have been shown to bind to actin networks under strain/tension. Consistent with this, we show that TRIP6 and LIMD1 colocalize with the ends of actin fibers at adherens junctions. Point mutations in a key conserved residue in each LIM domain that are predicted to impair binding to f-actin under strain inhibits TRIP6 and LIMD1 localization to adherens junctions and their ability to bind to and recruit LATS1 to adherens junctions. Together these results show that the ability of TRIP6 and LIMD1 to bind to strained actin underlies their ability to localize to adherens junctions and regulate LATS1 in response to mechanical tension.

Detecting normal and cancer skin cells via glycosylation and adhesion signatures: A path to enhanced microfluidic phenotyping

Recruiting circulating cells based on interactions between surface receptors and corresponding ligands holds promise for capturing cells with specific adhesive properties. Our study investigates the adhesion of skin cells to specific lectins, particularly focusing on advancements in lectin-based biosensors with diagnostic potential. We explore whether we can successfully capture normal skin (melanocytes and keratinocytes) and melanoma (WM35, WM115, WM266-4) cells in a low-shear flow environment by coating surfaces with lectins. Specifically, we coated surfaces with Dolichos biflorus (DBA) and Maackia Amurensis (MAL) lectins, which were used to detect and capture specific skin cells from the flow of cell mixture. Alterations in glycan expression (confirmed by fluorescent microscopy) demonstrated that DBA binds predominantly to normal skin cells, while MAL interacts strongly with melanoma cells. Assessing adhesion under static and dynamic low-shear stress conditions (up to 30 mPa) underscores the reliability of DBA and MAL as markers for discriminating specific cell type. Melanocytes and keratinocytes adhere to DBA-coated surfaces, while melanoma cells prefer MAL-coated surfaces. A comprehensive analysis encompassing cell shape, cytoskeleton, and focal adhesions shows the independence of our approach from the inherent characteristics of cells, thus demonstrating its robustness. Our results carry practical implications for lectin-biosensor designs, emphasizing the significance of glycan-based discrimination of pathologically altered cells. Combined with microfluidics, it demonstrates the value of cell adhesion as a discriminant of cancer-related changes, with potential applications spanning diagnostics, therapeutic interventions, and advanced biomedical technologies.

Molecular simulation approaches to probing the effects of mechanical forces in the actin cytoskeleton

In this article we give our perspective on the successes and promise of various molecular and coarse-grained simulation approaches to probing the effect of mechanical forces in the actin cytoskeleton.

IpaA reveals distinct modes of vinculin activation during Shigella invasion and cell-matrix adhesion

Vinculin is a cytoskeletal linker strengthening cell adhesion. The Shigella IpaA invasion effector binds to vinculin to promote vinculin supra-activation associated with head-domain-mediated oligomerization. Our study investigates the impact of mutations of vinculin D1D2 subdomains' residues predicted to interact with IpaA VBS3. These mutations affected the rate of D1D2 trimer formation with distinct effects on monomer disappearance, consistent with structural modeling of a closed and open D1D2 conformer induced by IpaA. Notably, mutations targeting the closed D1D2 conformer significantly reduced Shigella invasion of host cells as opposed to mutations targeting the open D1D2 conformer and later stages of vinculin head-domain oligomerization. In contrast, all mutations affected the formation of focal adhesions (FAs), supporting the involvement of vinculin supra-activation in this process. Our findings suggest that IpaA-induced vinculin supra-activation primarily reinforces matrix adhesion in infected cells, rather than promoting bacterial invasion. Consistently, shear stress studies pointed to a key role for IpaA-induced vinculin supra-activation in accelerating and strengthening cell-matrix adhesion.

Molecular dynamics simulations reveal how vinculin refolds partially unfolded talin rod helices to stabilize them against mechanical force

Vinculin binds to specific sites of mechanically unfolded talin rod domains to reinforce the coupling of the cell's exterior to its force generation machinery. Force-dependent vinculin-talin complexation and dissociation was previously observed as contraction or extension of the unfolded talin domains respectively using magnetic tweezers. However, the structural mechanism underlying vinculin recognition of unfolded vinculin binding sites (VBSs) in talin remains unknown. Using molecular dynamics simulations, we demonstrate that a VBS dynamically refolds under force, and that vinculin can recognize and bind to partially unfolded VBS states. Vinculin binding enables refolding of the mechanically strained VBS and stabilizes its folded α-helical conformation, providing resistance against mechanical stress. Together, these results provide an understanding of a recognition mechanism of proteins unfolded by force and insight into the initial moments of how vinculin binds unfolded talin rod domains during the assembly of this mechanosensing meshwork.

Develop Tandem Tension Sensor to Gauge Integrin-Transmitted Molecular Forces

DNA-based tension sensors have innovated the imaging and calibration of mechanosensitive receptor-transmitted molecular forces, such as integrin tensions. However, these sensors mainly serve as binary reporters, only indicating if molecular forces exceed one predefined threshold. Here, we have developed tandem tension sensor (TTS), which comprises two consecutive force-sensing units, each with unique force detection thresholds and distinct fluorescence spectra, thereby enabling the quantification of molecular forces with dual reference levels. With TTS, we revealed that vinculin is not required for transmitting integrin tensions at approximately 10 pN (piconewtons) but is essential for elevating integrin tensions beyond 20 pN in focal adhesions (FAs). Such high tensions have emerged during the early stage of FA formation. TTS also successfully detected changes in integrin tensions in response to disrupted actin formation, inhibited myosin activity, and tuned substrate elasticity. We also applied TTS to examine integrin tensions in platelets and revealed two force regimes, with integrin tensions surpassing 20 pN at cell central regions and 13-20 pN integrin tensions at the cell edge. Overall, TTS, especially the construct consisting of a hairpin DNA (13 pN opening force) and a shearing DNA (20 pN opening force), stands as a valuable tool for the quantification of receptor-transmitted molecular forces within living cells.

The role of actin cytoskeleton CFL1 and ADF/cofilin superfamily in inflammatory response

Actin remodeling proteins are important in immune diseases and regulate cell cytoskeletal responses. These responses play a pivotal role in maintaining the delicate balance of biological events, protecting against acute or chronic inflammation in a range of diseases. Cofilin (CFL) and actin depolymerization factor (ADF) are potent actin-binding proteins that cut and depolymerize actin filaments to generate actin cytoskeleton dynamics. Although the molecular mechanism by which actin induces actin cytoskeletal reconstitution has been studied for decades, the regulation of actin in the inflammatory process has only recently become apparent. In this paper, the functions of the actin cytoskeleton and ADF/cofilin superfamily members are briefly introduced, and then focus on the role of CFL1 in inflammatory response.

Detection of fluorescent protein mechanical switching in cellulo

The ability of cells to sense and respond to mechanical forces is critical in many physiological and pathological processes. However, determining the mechanisms by which forces affect protein function inside cells remains challenging. Motivated by in vitro demonstrations of fluorescent proteins (FPs) undergoing reversible mechanical switching of fluorescence, we investigated whether force-sensitive changes in FP function could be visualized in cells. Guided by a computational model of FP mechanical switching, we develop a formalism for its detection in Förster resonance energy transfer (FRET)-based biosensors and demonstrate its occurrence in cellulo within a synthetic actin crosslinker and the mechanical linker protein vinculin. We find that in cellulo mechanical switching is reversible and altered by manipulation of cell force generation, external stiffness, and force-sensitive bond dynamics of the biosensor. This work describes a framework for assessing FP mechanical stability and provides a means of probing force-sensitive protein function inside cells.

Hydroxyapatite-Coated Ti6Al4V ELI Alloy: In Vitro Cell Adhesion

The high rate of rejection and failure of orthopedic implants is primarily attributed to incomplete osseointegration and stress at the implant-to-bone interface due to significant differences in the mechanical properties of the implant and the surrounding bone. Various surface treatments have been developed to enhance the osteoconductive properties of implants. The aim of this work was the in vitro characterization of titanium alloy modified with a nanocrystalline hydroxyapatite surface layer in relative comparison to unmodified controls. This investigation focused on the behavior of the surface treatment in relation to the physiological environment. Moreover, the osteogenic response of human osteoblasts and adipose stem cells was assessed. Qualitative characterization of cellular interaction was performed via confocal laser scanning microscopy focusing on the cell nuclei and cytoskeletons. Filipodia were assessed using scanning electron microscopy. The results highlight that the HA treatment promotes protein adhesion as well as gene expression of osteoblasts and stem cells, which is relevant for the inorganic and organic components of the extracellular matrix and bone. In particular, cells grown onto HA-modified titanium alloy are able to promote ECM production, leading to a high expression of collagen I and non-collagenous proteins, which are crucial for regulating mineral matrix formation. Moreover, they present an impressive amount of filipodia having long extensions all over the test surface. These findings suggest that the HA surface treatment under investigation effectively enhances the osteoconductive properties of Ti6Al4V ELI.

Plakophilin 4 controls the spatio-temporal activity of RhoA at adherens junctions to promote cortical actin ring formation and tissue tension

Plakophilin 4 (PKP4) is a component of cell-cell junctions that regulates intercellular adhesion and Rho-signaling during cytokinesis with an unknown function during epidermal differentiation. Here we show that keratinocytes lacking PKP4 fail to develop a cortical actin ring, preventing adherens junction maturation and generation of tissue tension. Instead, PKP4-depleted cells display increased stress fibers. PKP4-dependent RhoA localization at AJs was required to activate a RhoA-ROCK2-MLCK-MLC2 axis and organize actin into a cortical ring. AJ-associated PKP4 provided a scaffold for the Rho activator ARHGEF2 and the RhoA effectors MLCK and MLC2, facilitating the spatio-temporal activation of RhoA signaling at cell junctions to allow cortical ring formation and actomyosin contraction. In contrast, association of PKP4 with the Rho suppressor ARHGAP23 reduced ARHGAP23 binding to RhoA which prevented RhoA activation in the cytoplasm and stress fiber formation. These data identify PKP4 as an AJ component that transduces mechanical signals into cytoskeletal organization.

Beyond microroughness: novel approaches to navigate osteoblast activity on implant surfaces

Considering the biological activity of osteoblasts is crucial when devising new approaches to enhance the osseointegration of implant surfaces, as their behavior profoundly influences clinical outcomes. An established inverse correlation exists between osteoblast proliferation and their functional differentiation, which constrains the rapid generation of a significant amount of bone. Examining the surface morphology of implants reveals that roughened titanium surfaces facilitate rapid but thin bone formation, whereas smooth, machined surfaces promote greater volumes of bone formation albeit at a slower pace. Consequently, osteoblasts differentiate faster on roughened surfaces but at the expense of proliferation speed. Moreover, the attachment and initial spreading behavior of osteoblasts are notably compromised on microrough surfaces. This review delves into our current understanding and recent advances in nanonodular texturing, meso-scale texturing, and UV photofunctionalization as potential strategies to address the "biological dilemma" of osteoblast kinetics, aiming to improve the quality and quantity of osseointegration. We discuss how these topographical and physicochemical strategies effectively mitigate and even overcome the dichotomy of osteoblast behavior and the biological challenges posed by microrough surfaces. Indeed, surfaces modified with these strategies exhibit enhanced recruitment, attachment, spread, and proliferation of osteoblasts compared to smooth surfaces, while maintaining or amplifying the inherent advantage of cell differentiation. These technology platforms suggest promising avenues for the development of future implants.

FAK, vinculin, and talin control mechanosensitive YAP nuclear localization

Focal adhesions (FAs) are nanoscale complexes containing clustered integrin receptors and intracellular structural and signaling proteins that function as principal sites of mechanotransduction in part via promoting the nuclear translocation and activation of the transcriptional coactivator yes-associated protein (YAP). Knockdown of FA proteins such as focal adhesion kinase (FAK), talin, and vinculin can prevent YAP nuclear localization. However, the mechanism(s) of action remain poorly understood. Herein, we investigated the role of different functional domains in vinculin, talin, and FAK in regulating YAP nuclear localization. Using genetic or pharmacological inhibition of fibroblasts and human mesenchymal stem cells (hMSCs) adhering to deformable substrates, we find that disruption of vinculin-talin binding versus talin-FAK binding reduces YAP nuclear localization and transcriptional activity via different mechanisms. Disruption of vinculin-talin binding or knockdown of talin-1 reduces nuclear size, traction forces, and YAP nuclear localization. In contrast, disruption of the talin binding site on FAK or elimination of FAK catalytic activity did not alter nuclear size yet still prevented YAP nuclear localization and activity. These data support both nuclear tension-dependent and independent models for matrix stiffness-regulated YAP nuclear localization. Our results highlight the importance of vinculin-talin-FAK interactions at FAs of adherent cells, controlling YAP nuclear localization and activity.

Structure-Mechanics Principles and Mechanobiology of Fibrocartilage Pericellular Matrix: A Pivotal Role of Type V Collagen

The pericellular matrix (PCM) is the immediate microniche surrounding resident cells in various tissue types, regulating matrix turnover, cell-matrix cross-talk and disease initiation. This study elucidated the structure-mechanical properties and mechanobiological functions of the PCM in fibrocartilage, a family of connective tissues that sustain complex tensile and compressive loads in vivo. Studying the murine meniscus as the model tissue, we showed that fibrocartilage PCM contains thinner, random collagen fibrillar networks that entrap proteoglycans, a structure distinct from the densely packed, highly aligned collagen fibers in the bulk extracellular matrix (ECM). In comparison to the ECM, the PCM has a lower modulus and greater isotropy, but similar relative viscoelastic properties. In Col5a1 +/- menisci, the reduction of collagen V, a minor collagen localized in the PCM, resulted in aberrant fibril thickening with increased heterogeneity. Consequently, the PCM exhibited a reduced modulus, loss of isotropy and faster viscoelastic relaxation. This disrupted PCM contributes to perturbed mechanotransduction of resident meniscal cells, as illustrated by reduced intracellular calcium signaling, as well as upregulated biosynthesis of lysyl oxidase and tenascin C. When cultured in vitro, Col5a1 +/- meniscal cells synthesized a weakened nascent PCM, which had inferior properties towards protecting resident cells against applied tensile stretch. These findings underscore the PCM as a distinctive microstructure that governs fibrocartilage mechanobiology, and highlight the pivotal role of collagen V in PCM function. Targeting the PCM or its molecular constituents holds promise for enhancing not only meniscus regeneration and osteoarthritis intervention, but also addressing diseases across various fibrocartilaginous tissues.

Ileum Proteomics Identifies Distinct Pathways Associated with Different Dietary Doses of Copper-Fructose Interactions: Implications for the Gut-Liver Axis and MASLD

The interactions of different dietary doses of copper with fructose contribute to the development of metabolic dysfunction-associated steatotic liver disease (MASLD) via the gut-liver axis. The underlying mechanisms remain elusive. The aim of this study was to identify the specific pathways leading to gut barrier dysfunction in the ileum using a proteomics approach in a rat model. Male weanling Sprague Dawley rats were fed diets with adequate copper (CuA), marginal copper (CuM), or supplemented copper (CuS) in the absence or presence of fructose supplementation (CuAF, CuMF, and CuSF) for 4 weeks. Ileum protein was extracted and analyzed with an LC-MS. A total of 2847 differentially expressed proteins (DEPs) were identified and submitted to functional enrichment analysis. As a result, the ileum proteome and signaling pathways that were differentially altered were revealed. Of note, the CuAF is characterized by the enrichment of oxidative phosphorylation and ribosome as analyzed with the KEGG; the CuMF is characterized by an enriched arachidonic acid metabolism pathway; and focal adhesion, the regulation of the actin cytoskeleton, and tight junction were significantly enriched by the CuSF. In conclusion, our proteomics analysis identified the specific pathways in the ileum related to the different dietary doses of copper-fructose interactions, suggesting that distinct mechanisms in the gut are involved in the development of MASLD.

Advanced gene nanocarriers/scaffolds in nonviral-mediated delivery system for tissue regeneration and repair

Tissue regeneration technology has been rapidly developed and widely applied in tissue engineering and repair. Compared with traditional approaches like surgical treatment, the rising gene therapy is able to have a durable effect on tissue regeneration, such as impaired bone regeneration, articular cartilage repair and cancer-resected tissue repair. Gene therapy can also facilitate the production of in situ therapeutic factors, thus minimizing the diffusion or loss of gene complexes and enabling spatiotemporally controlled release of gene products for tissue regeneration. Among different gene delivery vectors and supportive gene-activated matrices, advanced gene/drug nanocarriers attract exceptional attraction due to their tunable physiochemical properties, as well as excellent adaptive performance in gene therapy for tissue regeneration, such as bone, cartilage, blood vessel, nerve and cancer-resected tissue repair. This paper reviews the recent advances on nonviral-mediated gene delivery systems with an emphasis on the important role of advanced nanocarriers in gene therapy and tissue regeneration.

Comparative Analysis of Osteoblastic Responses to Titanium and Alumina-Toughened Zirconia Implants: An In Vitro Study

INTRODUCTION

Osteoblastic responses play a crucial role in the success of oral implants. Enhanced proliferation of osteoblast cells is associated with reduced cell mortality and an increase in bone regeneration. This study aims to evaluate the osteoblastic responses following oral implantation.

MATERIALS AND METHODS

Osteoblast stem cells were harvested and subsequently cultivated using cell culture techniques. The osteoblastic phenotype of the extracted cells was confirmed by examining the extracellular matrix. Cell morphogenesis on functionalized biomaterial surfaces was assessed through indirect immunofluorescence staining. The cellular response was investigated in the presence of two types of implant materials: titanium (Ti) and alumina-toughened zirconia (ATZ). Cell viability and apoptosis were quantitatively assessed using MTT assays and flow cytometry, respectively.

RESULTS

The survival of osteoblastic lineage cells was moderately reduced post-implantation. Viability in the Ti implant group remained at approximately 86%, while in the ATZ group, it was observed at 75%, which is considered acceptable. Moreover, there was a significant disparity in cell survival between the two implant groups (p < 0.05). Analysis of apoptosis levels at various concentrations revealed that the rate of apoptosis was 3.6% in the control group and 18.5% in the ATZ group, indicating that apoptosis or programmed cell death in the ATZ-treated group had increased nearly four-fold (p < 0.05).

CONCLUSIONS

The findings of this study indicate a reduction in osteoblastic cell line survival following implant treatment, with titanium implants exhibiting superior performance in terms of cell survival. However, it was also noted that the incidence of apoptosis in osteoblast cells was significantly higher in the presence of zirconium-based implants.

Human Platelet Lysate-Derived Nanofibrils as Building Blocks to Produce Free-Standing Membranes for Cell Self-Aggregation

Amyloid-like fibrils are garnering keen interest in biotechnology as supramolecular nanofunctional units to be used as biomimetic platforms to control cell behavior. Recent insights into fibril functionality have highlighted their importance in tissue structure, mechanical properties, and improved cell adhesion, emphasizing the need for scalable and high-kinetics fibril synthesis. In this study, we present the instantaneous and bulk formation of amyloid-like nanofibrils from human platelet lysate (PL) using the ionic liquid cholinium tosylate as a fibrillating agent. The instant fibrillation of PL proteins upon supramolecular protein-ionic liquid interactions was confirmed from the protein conformational transition toward cross-β-sheet-rich structures. These nanofibrils were utilized as building blocks for the formation of thin and flexible free-standing membranes via solvent casting to support cell self-aggregation. These PL-derived fibril membranes reveal a nanotopographically rough surface and high stability over 14 days under cell culture conditions. The culture of mesenchymal stem cells or tumor cells on the top of the membrane demonstrated that cells are able to adhere and self-organize in a three-dimensional (3D) spheroid-like microtissue while tightly folding the fibril membrane. Results suggest that nanofibril membrane incorporation in cell aggregates can improve cell viability and metabolic activity, recreating native tissues' organization. Altogether, these PL-derived nanofibril membranes are suitable bioactive platforms to generate 3D cell-guided microtissues, which can be explored as bottom-up strategies to faithfully emulate native tissues in a fully human microenvironment.

Silanization Strategies for Tailoring Peptide Functionalization on Silicon Surfaces: Implications for Enhancing Stem Cell Adhesion

Biomaterial surface engineering and the integration of cell-adhesive ligands are crucial in biological research and biotechnological applications. The interplay between cells and their microenvironment, influenced by chemical and physical cues, impacts cellular behavior. Surface modification of biomaterials profoundly affects cellular responses, especially at the cell-surface interface. This work focuses on enhancing cellular activities through material manipulation, emphasizing silanization for further functionalization with bioactive molecules such as RGD peptides to improve cell adhesion. The grafting of three distinct silanes onto silicon wafers using both spin coating and immersion methods was investigated. This study sheds light on the effects of different alkyl chain lengths and protecting groups on cellular behavior, providing valuable insights into optimizing silane-based self-assembled monolayers (SAMs) before peptide or protein grafting for the first time. Specifically, it challenges the common use of APTES molecules in this context. These findings advance our understanding of surface modification strategies, paving the way for tailoring biomaterial surfaces to modulate the cellular behavior for diverse biotechnological applications.

Multifunctional Prosthesis Surface: Modification of Titanium with Cinnamaldehyde-Loaded Hierarchical Titanium Dioxide Nanotubes

Orthopedic prostheses are the ultimate therapeutic solution for various end-stage orthopedic conditions. However, aseptic loosening and pyogenic infections remain as primary complications associated with these devices. In this study, a hierarchical titanium dioxide (TiO2) nanotube drug delivery system loaded with cinnamaldehyde for the surface modification of titanium implants, is constructed. These specially designed dual-layer TiO2 nanotubes enhance material reactivity and provide an extensive drug-loading platform within a short time. The introduction of cinnamaldehyde enhances the bone integration performance of the scaffold (simultaneously promoting bone formation and inhibiting bone resorption), anti-inflammatory capacity, and antibacterial properties. In vitro experiments have demonstrated that this system promoted osteogenesis by upregulating both Wnt/β-catenin and MAPK signaling pathways. Furthermore, it inhibits osteoclast formation, suppresses macrophage-mediated inflammatory responses, and impedes the proliferation of Staphylococcus aureus and Escherichia coli. In vivo experiments shows that this material enhances bone integration in a rat model of femoral defects. In addition, it effectively enhances the antibacterial and anti-inflammatory properties in a subcutaneous implant in a rat model. This study provides a straightforward and highly effective surface modification strategy for orthopedic Ti implants.