Tissue mechanics in stem cell fate, development, and cancer

Strain softening and hysteresis arising from 3D multicellular dynamics during long-term large deformation

Living tissues exhibit complex mechanical properties, including viscoelastic and elastoplastic responses, that are crucial for regulating cell behaviors and tissue deformations. Despite their significance, the intricate properties of three-dimensional (3D) cell constructs are not well understood and are inadequately implemented in biomaterial engineering. To address this gap, we developed a numerical method to analyze the dynamic properties of cell constructs using a 3D vertex model framework. By focusing on 3D tissues composed of confluent homogeneous cells, we characterized their properties in response to various deformation magnitudes and time scales. Stress relaxation tests revealed that large deformations initially induced relaxation in the shapes of individual cells. This process is amplified by subsequent transient cell rearrangements, homogenizing cell shapes and leading to tissue fluidization. Additionally, dynamic viscoelastic analyses showed that tissues exhibited strain softening and hysteresis during large deformations. Interestingly, this strain softening originates from multicellular structures independent of cell rearrangement, while hysteresis arises from cell rearrangement. Moreover, tissues exhibit elastoplastic responses over the long term, which are well represented by the Ramberg-Osgood model. These findings highlight the characteristic properties of cell constructs emerging from their structures and rearrangements, especially during long-term large deformations. The developed method offers a new approach to uncover the dynamic nature of 3D tissue mechanics and could serve as a technical foundation for exploring tissue mechanics and advancing biomaterial engineering.

Targeting metastasis in paediatric bone sarcomas

Paediatric bone sarcomas (e.g. Ewing sarcoma, osteosarcoma) comprise significant biological and clinical heterogeneity. This extreme heterogeneity affects response to systemic therapy, facilitates inherent and acquired drug resistance and possibly underpins the origins of metastatic disease, a key component implicit in cancer related death. Across all cancers, metastatic models have offered competing accounts on when dissemination occurs, either early or late during tumorigenesis, whether metastases at different foci arise independently and directly from the primary tumour or give rise to each other, i.e. metastases-to-metastases dissemination, and whether cell exchange occurs between synchronously growing lesions. Although it is probable that all the above mechanisms can lead to metastatic disease, clinical observations indicate that distinct modes of metastasis might predominate in different cancers. Around 70% of patients with bone sarcoma experience metastasis during their disease course but the fundamental molecular and cell mechanisms underlying spread are equivocal. Newer therapies such as tyrosine kinase inhibitors have shown promise in reducing metastatic relapse in trials, nonetheless, not all patients respond and 5-year overall survival remains at ~ 50%. Better understanding of potential bone sarcoma biological subgroups, the role of the tumour immune microenvironment, factors that promote metastasis and clinical biomarkers of prognosis and drug response are required to make progress. In this review, we provide a comprehensive overview of the approaches to manage paediatric patients with metastatic Ewing sarcoma and osteosarcoma. We describe the molecular basis of the tumour immune microenvironment, cell plasticity, circulating tumour cells and the development of the pre-metastatic niche, all required for successful distant colonisation. Finally, we discuss ongoing and upcoming patient clinical trials, biomarkers and gene regulatory networks amenable to the development of anti-metastasis medicines.

Modelling Cancer Pathophysiology: Mechanisms and Changes in the Extracellular Matrix During Cancer Initiation and Early Tumour Growth

Cancer initiation and early tumour growth are complex processes influenced by multiple cellular and microenvironmental factors. A critical aspect of tumour progression is the dynamic interplay between cancer cells and the extracellular matrix (ECM), which undergoes significant alterations to support malignancy. The loss of cell polarity is an early hallmark of tumour progression, disrupting normal tissue architecture and fostering cancerous transformation. Circumstantially, cancer-associated microRNAs (miRNAs) regulate key oncogenic processes, including ECM remodelling, epithelial-to-mesenchymal transition (EMT), and tumorigenic vascular development, further driving tumour growth. ECM alterations, particularly changes in stiffness and mechanotransduction signals, create a supportive niche for cancer cells, enhancing their survival, proliferation, and invasion. EMT and its subtype, epithelial-to-endothelial transition (EET), contribute to tumour plasticity, promote the generation of cancer stem cells (CSCs), and support tumour vascularisation. Furthermore, processes of vascular development like vasculogenesis and angiogenesis are critical for sustaining early tumour growth, supplying oxygen and nutrients to hypoxic malignant cells within the evolving cancerous microenvironments. This review explores key mechanisms underlying these changes in tumorigenic microenvironments, with an emphasis on their collective role for tumour initiation and early tumour growth. It will further delve into present in vitro modelling strategies developed to closely mimic early cancer pathophysiology. Understanding these processes is crucial for developing targeted therapies aimed at disrupting key cancer-promoting pathways and improving clinical outcomes.

Nuclear envelope proteins, mechanotransduction, and their contribution to breast cancer progression

Breast cancer cells frequently exhibit changes in the expression of nuclear envelope (NE) proteins such as lamins and emerin that determine the physical properties of the nucleus and contribute to cellular mechanotransduction. This review explores the emerging interplay between NE proteins, the physical challenges incurred during metastatic progression, and mechanotransduction. Improved insights into the underlying mechanisms may ultimately lead to better prognostic tools and treatment strategies for metastatic breast cancer.

Regenerative characteristics of the immortal jellyfish, Turritopsis dohrnii, and their potential implications for human aging

The jellyfish Turritopsis dohrnii (T. Nutricala) is a cnidarian of the Oceaniidae family that lives in the Mediterranean Sea. It is known as the immortal jellyfish since, through a process of cell development called transdifferentiation, it manages to return to a polyp state. The role of regeneration processes and their impact on aging have been studied in recent years for their potential applications in the development of more efficient pharmacology to address disorders related to aging. Reviewing the terms related to transdifferentiation in jellyfish and understanding the underlying mechanisms can help comprehend diverse processes such as aging, regeneration, and the molecular bases of diseases like cancer. This paper's purpose is to provide a description of the regenerative characteristics of the jellyfish T. dohrnii, investigate how its regenerative processes allow it to rejuvenate, and determine if these tissue restoration processes are also found in humans.

Tissue mechanics in tumor heterogeneity and aggression

Tumorigenesis ensues within a heterogeneous tissue microenvironment that promotes malignant transformation, metastasis and treatment resistance. A major feature of the tumor microenvironment is the heterogeneous population of cancer-associated fibroblasts and myeloid cells that stiffen the extracellular matrix. The heterogeneously stiffened extracellular matrix in turn activates cellular mechanotransduction and creates a hypoxic and metabolically hostile microenvironment. The stiffened extracellular matrix and elevated mechanosignaling also drive tumor aggression by fostering tumor cell growth, survival, and invasion, compromising antitumor immunity, expanding cancer stem cell frequency, and increasing mutational burden, which promote intratumor heterogeneity. Delineating the molecular mechanisms whereby tissue mechanics regulate these phenotypes should help to clarify the basis for tumor heterogeneity and cancer aggression and identify novel therapeutic targets that could improve patient outcome. Here, we discuss the role of the extracellular matrix in driving cancer aggression through its impact on tumor heterogeneity.

Quantitative Super-Resolution Imaging of Molecular Tension

DNA-based molecular tension probes have revolutionized the localization of mechanical events in live cells with super-resolution. However, imaging the magnitude of these forces at super-resolution has been challenging. Here, qtPAINT (quantitative tension points accumulation for imaging in nanoscale topography) is introduced as a strategy to image the magnitude of molecular tension with super-resolution accuracy. By leveraging the force-dependent dissociation kinetics of short DNA oligonucleotides on their complementary strands, tension is encoded on individual molecules through their binding kinetics. This method allowed for a quantitative analysis of these kinetics, providing a detailed reconstruction of the force magnitudes acting on each tension probe. The technique integrates a molecular-beacon PAINT imager with a hairpin molecular tension probe, achieving a force quantification range of 9-30 pN and maintaining a spatial resolution of 30-120 nm in low and high-density regions. Additionally, qtPAINT offers a temporal resolution on the order of a minute, enhancing its applicability for studying dynamic cellular processes.

Softness or Stiffness What Contributes to Cancer and Cancer Metastasis?

Beyond the genomic and proteomic analysis of bulk and single cancer cells, a new focus of cancer research is emerging that is based on the mechanical analysis of cancer cells. Therefore, several biophysical techniques have been developed and adapted. The characterization of cancer cells, like human cancer cell lines, started with their mechanical characterization at mostly a single timepoint. A universal hypothesis has been proposed that cancer cells need to be softer to migrate and invade tissues and subsequently metastasize in targeted organs. Thus, the softness of cancer cells has been suggested to serve as a universal physical marker for the malignancy of cancer types. However, it has turned out that there exists the opposite phenomenon, namely that stiffer cancer cells are more migratory and invasive and therefore lead to more metastases. These contradictory results question the universality of the role of softness of cancer cells in the malignant progression of cancers. Another problem is that the various biophysical techniques used can affect the mechanical properties of cancer cells, making it even more difficult to compare the results of different studies. Apart from the instrumentation, the culture and measurement conditions of the cancer cells can influence the mechanical measurements. The review highlights the main advances of the mechanical characterization of cancer cells, discusses the strength and weaknesses of the approaches, and questions whether the passive mechanical characterization of cancer cells is still state-of-the art. Besides the cell models, conditions and biophysical setups, the role of the microenvironment on the mechanical characteristics of cancer cells is presented and debated. Finally, combinatorial approaches to determine the malignant potential of tumors, such as the involvement of the ECM, the cells in a homogeneous or heterogeneous association, or biological multi-omics analyses, together with the dynamic-mechanical analysis of cancer cells, are highlighted as new frontiers of research.

Biomaterial scaffold stiffness influences the foreign body reaction, tissue stiffness, angiogenesis and neuroregeneration in spinal cord injury

Biomaterial scaffold engineering presents great potential in promoting axonal regrowth after spinal cord injury (SCI), yet persistent challenges remain, including the surrounding host foreign body reaction and improper host-implant integration. Recent advances in mechanobiology spark interest in optimizing the mechanical properties of biomaterial scaffolds to alleviate the foreign body reaction and facilitate seamless integration. The impact of scaffold stiffness on injured spinal cords has not been thoroughly investigated. Herein, we introduce stiffness-varied alginate anisotropic capillary hydrogel scaffolds implanted into adult rat C5 spinal cords post-lateral hemisection. Four weeks post-implantation, scaffolds with a stiffness approaching that of the spinal cord effectively minimize the host foreign body reaction via yes-associated protein (YAP) nuclear translocation. Concurrently, the softest scaffolds maximize cell infiltration and angiogenesis, fostering significant axonal regrowth but limiting the rostral-caudal linear growth. Furthermore, as measured by atomic force microscopy (AFM), the surrounding spinal cord softens when in contact with the stiffest scaffold while maintaining a physiological level in contact with the softest one. In conclusion, our findings underscore the pivotal role of stiffness in scaffold engineering for SCI in vivo, paving the way for the optimal development of efficacious biomaterial scaffolds for tissue engineering in the central nervous system.

Tissue Active Matter: Integrating Mechanics and Signaling into Dynamical Models

The importance of physical forces in the morphogenesis, homeostatic function, and pathological dysfunction of multicellular tissues is being increasingly characterized, both theoretically and experimentally. Analogies between biological systems and inert materials such as foams, gels, and liquid crystals have provided striking insights into the core design principles underlying multicellular organization. However, these connections can seem surprising given that a key feature of multicellular systems is their ability to constantly consume energy, providing an active origin for the forces that they produce. Key emerging questions are, therefore, to understand whether and how this activity grants tissues novel properties that do not have counterparts in classical materials, as well as their consequences for biological function. Here, we review recent discoveries at the intersection of active matter and tissue biology, with an emphasis on how modeling and experiments can be combined to understand the dynamics of multicellular systems. These approaches suggest that a number of key biological tissue-scale phenomena, such as morphogenetic shape changes, collective migration, or fate decisions, share unifying design principles that can be described by physical models of tissue active matter.

Tunable Integrin-Ligand Coupling Strength Modulates Cellular Adaptive Mechanosensing

Cells sense and respond to the matrix by exerting traction force through binding of integrins to an integrin-specific ligand. Here, Arg-Gly-Asp (RGD) peptide is covalently conjugated to the double-stranded DNA (dsDNA) and stem-loop DNA (slDNA) tethers with a tension tolerance of 43pN and immobilized on a PEG substrate. Unlike dsDNA, which is ruptured under high tension, leading to the removal of RGD, slDNA remains bound even when ruptured. Our results suggest that cells adapt their adhesion state by modulating actin filament polymerization and cofilin phosphorylation, effectively balancing the talin conformation to prevent dsDNA rupture and maintain normal adhesion. This phenomenon, termed integrin-ligand coupling strength, mediated cellular adaptive mechanosensing. Furthermore, we demonstrate that positive durotaxis can shift to negative durotaxis, depending on the integrin-ligand coupling strength. This study highlights the significance of the coupling strength in cell-extracellular matrix (ECM) interactions and offers new insights into designing biomaterials with tunable adhesive properties for cell-based applications.

Nanoscale distribution of bioactive ligands on biomaterials regulates cell mechanosensing through translocation of actin into the nucleus

Cells respond to adhesive ligands such as arginine-glycine-aspartate (RGD) through integrins, which regulates cellular activities via influencing cytoskeleton assembly. Herein, we report that the nanoscale distribution of active ligands on biomaterials regulates cells through not only cytoplasmic tension but also nuclear tension. This is particularly related to translocation of actin into nucleus and highlighted in our interpretation of an "abnormal" phenomenon that large RGD nanospacing (>70 nm) disassembles integrin clusters, inhibits cell adhesion, but promotes osteogenic differentiation of mesenchymal stem cells. Our studies reveal that the unstable adhesion at the 150 nm RGD distance increases actin dynamics, resulting in the nuclear translocation of globular (G) actin. The compartment polymerization of more G-actins to filamentous actins in nucleus increases nuclear tension, facilitating transcription activity and releasing calcium ions from the endoplasmic reticulum. This noncanonical mechanotransduction process sheds insight into mechanotransduction pertinent to cell-material interactions.

ECM Stiffness-Induced Redox Signaling Enhances Stearoyl Gemcitabine Efficacy in Pancreatic Cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, largely due to its dense fibrotic stroma that promotes drug resistance and tumor progression. While patient-derived organoids (PDOs) have emerged as promising tools for modeling PDAC and evaluating therapeutic responses, the current PDO models grown in soft matrices fail to replicate the tumor's stiff extracellular matrix (ECM), limiting their predictive value for advanced disease.

METHODS

We developed a biomimetic model using gelatin-based matrices of varying stiffness, achieved through modulated transglutaminase crosslinking rates, to better simulate the desmoplastic PDAC microenvironment. Using this platform, we investigated organoid morphology, proliferation, and chemoresistance to gemcitabine (Gem) and its lipophilic derivative, 4-N-stearoyl gemcitabine (Gem-S). Mechanistic studies focused on the interplay between ECM stiffness, hypoxia-inducible factor (HIF) expression, and the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in drug resistance.

RESULTS

PDAC organoids in stiffer matrices demonstrated enhanced stemness features, including rounded morphology and elevated cancer stem cell (CSC) marker expression. Matrix stiffness-induced gemcitabine resistance correlated with the upregulation of ABC transporters and oxidative stress adaptive responses. While gemcitabine activated Nrf2 expression, promoting oxidative stress mitigation, Gem-S suppressed Nrf2 levels and induced oxidative stress, leading to increased reactive oxygen species (ROS) and enhanced cell death. Both compounds reduced HIF expression, with gemcitabine showing greater efficacy.

CONCLUSIONS

Our study reveals ECM stiffness as a critical mediator of PDAC chemoresistance through the promotion of stemness and modulation of Nrf2 and HIF pathways. Gem-S demonstrates promise in overcoming gemcitabine resistance by disrupting Nrf2-mediated adaptive responses and inducing oxidative stress. These findings underscore the importance of biomechanically accurate tumor models and suggest that dual targeting of mechanical and oxidative stress pathways may improve PDAC treatment outcomes.

Role of Cell Adhesion in Cancer Metastasis Formation: A Review

Intercellular adhesion is accompanied by several physical quantities and actions. In this review, we tried to collect information about the influence of surface energy and its impact on cell-cell adhesion. It still undergoes development for cancer treatment. Data on receptor-ligand interactions that occur on circulating tumor cells (CTCs) are described, and adhesion receptors as therapeutic targets are collected. Additionally, the impact of surface roughness on the interactions between CTC cells and the surface was monitored. The effects of different cell adhesion molecules (CAMs) on cell adhesion, growth, and proliferation were investigated. This review offers general principles of cell adhesion, through the blockade of adhesion with blocking drugs and inhibitors like computational models that describe the process of adhesion. Some theoretical models based on the minimum of the total free energy of interaction between CAMs and selected organic molecules have been presented. The final aim was to find information on how modulation of the surface of CTCs (by medicals or physically) inhibits cancer metastases formation.

Matrix Stiffness-Mediated DNA Methylation in Endothelial Cells

Purpose

Altered tissue mechanics is a prominent feature of many pathological conditions including cancer. As such, much work has been dedicated to understanding how mechanical features of tissues contribute to pathogenesis. Interestingly, previous work has demonstrated that the tumor vasculature acquires pathological features in part due to enhanced tumor stiffening. To further understand how matrix mechanics may be translated into altered cell behavior and ultimately affect tumor vasculature function, we have investigated the effects of substrate stiffening on endothelial epigenetics. Specifically, we have focused on DNA methylation as recent work indicates DNA methylation in endothelial cells can contribute to aberrant behavior in a range of pathological conditions.

Methods

Human umbilical vein endothelial cells (HUVECs) were seeded on stiff and compliant collagen-coated polyacrylamide gels and allowed to form monolayers over 5 days. DNA methylation was assessed via 5-methylcytosine ELISA assays and immunofluorescent staining. Gene expression was assessed via qPCR on RNA isolated from HUVECs seeded on collagen-coated polyacrylamide gels of varying stiffness.

Results

Our work demonstrates that endothelial cells cultured on stiffer substrates exhibit lower levels of global DNA methylation relative to endothelial cells cultured on more compliant substrates. Interestingly, gene expression and DNA methylation dynamics suggest stiffness-mediated gene expression may play a role in establishing or maintaining differential DNA methylation levels in addition to enzyme activity. Additionally, we found that the process of passaging induced higher levels of global DNA methylation.

Conclusions

Altogether, our results underscore the importance of considering cell culture substrate mechanics to preserve the epigenetic integrity of primary cells and obtain analyses that recapitulate the primary environment. Furthermore, these results serve as an important launching point for further work studying the intersection tissue mechanics and epigenetics under pathological conditions.

High-Throughput Single-Cell Analysis of Local Nascent Protein Deposition in 3D Microenvironments via Extracellular Protein Identification Cytometry (EPIC)

Extracellular matrix (ECM) guides cell behavior and tissue fate. Cell populations are notoriously heterogeneous leading to large variations in cell behavior at the single-cell level. Although insights into population heterogeneity are valuable for fundamental biology, regenerative medicine, and drug testing, current ECM analysis techniques only provide either averaged population-level data or single-cell data from a limited number of cells. Here, extracellular protein identification cytometry (EPIC) is presented as a novel platform technology that enables high-throughput measurements of local nascent protein deposition at single-cell level. Specifically, human primary chondrocytes are microfluidically encapsulated in enzymatically crosslinked microgels of 16 picoliter at kHz rates, forming large libraries of discrete 3D single-cell microniches in which ECM can be deposited. ECM proteins are labeled using fluorescence immunostaining to allow for nondestructive analysis via flow cytometry. This approach reveals population heterogeneity in matrix deposition at unprecedented throughput, allowing for the identification and fluorescent activated cell sorting-mediated isolation of cellular subpopulations. Additionally, it is demonstrated that inclusion of a second cell into microgels allows for studying the effect of cell-cell contact on matrix deposition. In summary, EPIC enables high-throughput single-cell analysis of nascent proteins in 3D microenvironments, which is anticipated to advance fundamental knowledge and tissue engineering applications.

Protein Coronation-Induced Cancer Staging-Dependent Multilevel Cytotoxicity: An All-Humanized Study in Blood Vessel Organoids

The protein corona effect refers to the phenomenon wherein nanomaterials in the bloodstream are coated by serum proteins, yet how protein coronated nanomaterials interact with blood vessels and its toxicity implications remain poorly understood. In this study, we investigated protein corona-related vessel toxicity by using an all-humanized assay integrating blood vessel organoids and patient-derived serum. Initially, we screened various nanomaterials to discern how parameters including size, morphology, hydrophobicity, surface charge, and chirality-dependent protein corona difference influence their uptake by vessel organoids. For nanomaterials showing substantial differences in vessel uptake, their protein corona was analyzed by using label-free mass spectra. Our findings revealed the involvement of cancer staging-related cytoskeleton components in mediating preferential uptake by cells, including endothelial and mural cells. Additionally, a transcriptome study was conducted to elucidate the influence of nanomaterials. We confirmed that protein coronated nanomaterials provoke remodeling at both transcriptional and translational levels, impacting pathways such as PI3K-Akt/Hippo/Wnt, and membraneless organelle integrity, respectively. Our study further demonstrated that the remodeling potential of patient-derived protein coronated nanomaterials can be harnessed to synergize with antiangiogenesis therapeutics to improve the outcomes. We anticipate that this study will provide guidance for the safe use of nanomedicine in the future.

Unraveling the Role of the Tumor Extracellular Matrix to Inform Nanoparticle Design for Nanomedicine

The extracellular matrix (ECM)-and its mechanobiology-regulates key cellular functions that drive tumor growth and development. Accordingly, mechanotherapy is emerging as an effective approach to treat fibrotic diseases such as cancer. Through restoring the ECM to healthy-like conditions, this treatment aims to improve tissue perfusion, facilitating the delivery of chemotherapies. In particular, the manipulation of ECM is gaining interest as a valuable strategy for developing innovative treatments based on nanoparticles (NPs). However, further progress is required; for instance, it is known that the presence of a dense ECM, which hampers the penetration of NPs, primarily impacts the efficacy of nanomedicines. Furthermore, most 2D in vitro studies fail to recapitulate the physiological deposition of matrix components. To address these issues, a comprehensive understanding of the interactions between the ECM and NPs is needed. This review focuses on the main features of the ECM and its complex interplay with NPs. Recent advances in mechanotherapy are discussed and insights are offered into how its combination with nanomedicine can help improve nanomaterials design and advance their clinical translation.

Sulfated and Phosphorylated Agarose as Biomaterials for a Biomimetic Paradigm for FGF-2 Release

Cardiovascular diseases such as myocardial infarction or limb ischemia are characterized by regression of blood vessels. Local delivery of growth factors (GFs) involved in angiogenesis such as fibroblast blast growth factor-2 (FGF-2) has been shown to trigger collateral neovasculature and might lead to a therapeutic strategy. In vivo, heparin, a sulfated polysaccharide present in abundance in the extracellular matrix (ECM), has been shown to function as a local reservoir for FGF-2 by binding FGF-2 and other morphogens and it plays a role in the evolution of GF gradients. To access injectable biomaterials that can mimic such natural electrostatic interactions between soluble signals and macromolecules and mechanically tunable environments, the backbone of agarose, a thermogelling marine-algae-derived polysaccharide, was modified with sulfate, phosphate, and carboxylic moieties and the interaction and release of FGF-2 from these functionalized hydrogels was assessed by ELISA in vitro and CAM assay in ovo. Our findings show that FGF-2 remains active after release, and FGF-2 release profiles can be influenced by sulfated and phosphorylated agarose, and in turn, promote varied blood vessel formation kinetics. These modified agaroses offer a simple approach to mimicking electrostatic interactions experienced by GFs in the extracellular environment and provide a platform to probe the role of these interactions in the modulation of growth factor activity and may find utility as an injectable gel for promoting angiogenesis and as bioinks in 3D bioprinting.

Towards a more objective and high-throughput spheroid invasion assay quantification method

Multicellular spheroids embedded in 3D hydrogels are prominent in vitro models for 3D cell invasion. Yet, quantification methods for spheroid cell invasion that are high-throughput, objective and accessible are still lacking. Variations in spheroid sizes and the shapes of the cells within render it difficult to objectively assess invasion extent. The goal of this work is to develop a high-throughput quantification method of cell invasion into 3D matrices that minimizes sensitivity to initial spheroid size and cell spreading and provides precise integrative directionally-dependent metrics of invasion. By analyzing images of fluorescent cell nuclei, invasion metrics are automatically calculated at the pixel level. The initial spheroid boundary is segmented and automated calculations of the nuclear pixel distances from the initial boundary are used to compute common invasion metrics (i.e., the change in invasion area, mean distance) for the same spheroid at a later timepoint. We also introduce the area moment of inertia as an integrative metric of cell invasion that considers the invasion area as well as the pixel distances from the initial spheroid boundary. Further, we show that principal component analysis can be used to quantify the directional influence of a stimuli to invasion (e.g., due to a chemotactic gradient or contact guidance). To demonstrate the power of the analysis for cell types with different invasive potentials and the utility of this method for a variety of biological applications, the method is used to analyze the invasiveness of five different cell types. In all, implementation of this high-throughput quantification method results in consistent and objective analysis of 3D multicellular spheroid invasion. We provide the analysis code in both MATLAB and Python languages as well as a GUI for ease of use for researchers with a range of computer programming skills and for applications in a variety of biological research areas such as wound healing and cancer metastasis.

An Advanced Mechanically Active Osteoarthritis-on-Chip Model to Test Injectable Therapeutic Formulations: The SYN321 Case Study

Current treatments for osteoarthritis (OA) often fail to address the underlying pathophysiology and may have systemic side effects, particularly associated with long-term use of non-steroidal anti-inflammatory drugs (NSAIDs). Thus, researchers are currently directing their efforts toward innovative polymer-drug combinations, such as mixtures of hyaluronic acid viscoelastic hydrogels and NSAIDs like diclofenac, to ensure sustained release of the NSAID within the joint following intra-articular injection. However, the progress of novel injectable therapies for OA is hindered by the absence of preclinical models that accurately represent the pathology of the disease. The uBeat® MultiCompress platform is here presented as a novel approach for studying anti-OA injectable therapeutics on human mechanically-damaged OA cartilage microtissues, in a physiologically relevant environment. This platform can accommodate injectable therapeutic formulations and is successfully tested with SYN321, a novel diclofenac-sodium hyaluronate conjugate under development as a treatment for knee OA. Results indicate the platform's effectiveness in evaluating therapeutic potential, showing downregulation of inflammatory markers and reduction in matrix degradation in OA cartilage micro-tissues treated with SYN321. The uBeat® MultiCompress platform thus represents a valuable tool for OA research, offering a bridge between traditional in vitro studies and potential clinical applications, with implications for future drug discovery.

Low-dose tamoxifen treatment reduces collagen organisation indicative of tissue stiffness in the normal breast: results from the KARISMA randomised controlled trial

BACKGROUND

Tissue stiffness, dictated by organisation of interstitial fibrillar collagens, increases breast cancer risk and contributes to cancer progression. Tamoxifen is a standard treatment for receptor-positive breast cancer and is also aproved for primary prevention. We investigated the effect of tamoxifen and its main metabolites on the breast tissue collagen organisation as a proxy for stiffness and explored the relationship between mammographic density (MD) and collagen organisation.

MATERIAL AND METHODS

This sub-study of the double-blinded dose-determination trial, KARISMA, included 83 healthy women randomised to 6 months of 20, 10, 5, 2.5, and 1 mg of tamoxifen or placebo. Ultrasound-guided core-needle breast biopsies collected before and after treatment were evaluated for collagen organisation by polarised light microscopy.

RESULTS

Tamoxifen reduced the amount of organised collagen and overall organisation, reflected by a shift from heavily crosslinked thick fibres to thinner, less crosslinked fibres. Collagen remodelling correlated with plasma concentrations of tamoxifen metabolites. MD change was not associated with changes in amount of organised collagen but was correlated with less crosslinking in premenopausal women.

CONCLUSIONS

In this study of healthy women, tamoxifen decreased the overall organisation of fibrillar collagens, and consequently, the breast tissue stiffness. These stromal alterations may play a role in the well-established preventive and therapeutic effects of tamoxifen. Trial registration ClinicalTrials.gov ID: NCT03346200. Registered November 1st, 2017. Retrospectively registered.

Association between the systemic immune-inflammation index and the outcome of liver fibrosis in patients with chronic hepatitis C

Background

Risk factors that influence the outcome of patients with chronic hepatitis C (CHC) are not fully understood. The systemic immune-inflammatory index (SII) is an independent prognostic factor for multiple diseases. However, the impact of the SII on the outcome of liver fibrosis is unclear.

Methods

This prospective real-world study enrolled patients with CHC treated with sofosbuvir/velpatasvir. Logistic regression models were used to investigate the relationship between the SII and the outcome of liver fibrosis in treatment-naive patients. Liver fibrosis was assessed using aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 index (FIB-4).

Results

Of the 288 participants, the SII was 238.2 (153.0-358.2). The non-improved outcomes of liver fibrosis assessed with APRI (non-improved APRI) and FIB-4 (non-improved FIB-4) were 83.0 and 87.5%, respectively. Adjusted models showed that the SII was positively associated with non-improved APRI (adjusted OR (95% CI): 1.013 (1.009-1.017), p < 0.001) and FIB-4 (adjusted OR (95% CI): 1.004 (1.001-1.007), p = 0.012). Similarly, a higher SII was associated with a higher risk of non-improved APRI (adjusted OR (95% CI): 13.53 (5.60-32.68), p < 0.001) and FIB-4 (adjusted OR (95% CI): 5.69 (2.17-14.90), p < 0.001). The association with non-improved APRI was much more remarkable in patients with alanine aminotransferase <2 ULN, and the association with non-improved FIB-4 was remarkable in patients aged <50 years. Multiple imputation analyses confirmed the robustness of these results.

Conclusion

Our findings suggested that the SII was positively associated with non-improved outcomes of liver fibrosis in patients with CHC. These results need to be validated in large-scale prospective cohorts.

Influence of viscosity on adipogenic and osteogenic differentiation of mesenchymal stem cells during 2D culture

Accumulatively, cellular behaviours triggered by biochemical cues have been widely explored and the focus of research is gradually shifting to biophysical cues. Compared to physical parameters such as stiffness, substrate morphology and viscoelasticity, the influence of viscosity on cellular behaviours is relatively unexplored and overlooked. Thus, in this study, the influence of viscosity on the adipogenic and osteogenic differentiation of human mesenchymal stem cells (hMSCs) was investigated by adjusting the viscosity of the culture medium. Viscosity exhibited different effects on adipogenic and osteogenic differentiation of hMSCs during two-dimensional (2D) culture. High viscosity facilitated osteogenic while inhibiting adipogenic differentiation. During adipogenic differentiation, the effect of viscosity on cell proliferation was negligible. However, during osteogenic differentiation, high viscosity decreased cell proliferation. The different influence of viscosity could be explained by the activation of mechanotransduction regulators of Yes-associated protein (YAP) and β-catenin. High viscosity could promote YAP and β-catenin nuclear translocation during osteogenic differentiation, which was responsible for the increased osteogenesis. High viscosity inhibited adipogenesis through promoting YAP nuclear translocation. This study could broaden the understanding of how viscosity can affect stem cell differentiation during 2D culture, which is valuable for tissue engineering.

Towards a More Objective and High-throughput Spheroid Invasion Assay Quantification Method

Multicellular spheroids embedded in 3D hydrogels are prominent in vitro models for 3D cell invasion. Yet, quantification methods for spheroid cell invasion that are high throughput, objective and accessible are still lacking. Variations in spheroid sizes and the shapes of the cells within render it difficult to objectively assess invasion extent. The goal of this work is to develop a high-throughput quantification method of cell invasion into 3D matrices that minimizes sensitivity to initial spheroid size and cell spreading and provides precise integrative directionally-dependent metrics of invasion. By analyzing images of fluorescent cell nuclei, invasion metrics are automatically calculated at the pixel level. The initial spheroid boundary is segmented and automated calculations of the nuclear pixel distances from the initial boundary are used to compute common invasion metrics (i.e., the change in invasion area, mean distance) for the same spheroid at a later timepoint. We also introduce the area moment of inertia as an integrative metric of cell invasion that considers the invasion area as well as the pixel distances from the initial spheroid boundary. Further, we show that principal component analysis can be used to quantify the directional influence of a stimuli to invasion (e.g., due to a chemotactic gradient or contact guidance). To demonstrate the power of the analysis for cell types with different invasive potentials and the utility of this method for a variety of biological applications, the method is used to analyze the invasiveness of five different cell types. In all, implementation of this high throughput quantification method results in consistent and objective analysis of 3D multicellular spheroid invasion. We provide the analysis code in both MATLAB and Python languages as well as a GUI for ease of use for researchers with a range of computer programming skills and for applications in a variety of biological research areas such as wound healing and cancer metastasis.

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.

GAN-WGCNA: Calculating gene modules to identify key intermediate regulators in cocaine addiction

Understanding time-series interplay of genes is essential for diagnosis and treatment of disease. Spatio-temporally enriched NGS data contain important underlying regulatory mechanisms of biological processes. Generative adversarial networks (GANs) have been used to augment biological data to describe hidden intermediate time-series gene expression profiles during specific biological processes. Developing a pipeline that uses augmented time-series gene expression profiles is needed to provide an unbiased systemic-level map of biological processes and test for the statistical significance of the generated dataset, leading to the discovery of hidden intermediate regulators. Two analytical methods, GAN-WGCNA (weighted gene co-expression network analysis) and rDEG (rescued differentially expressed gene), interpreted spatiotemporal information and screened intermediate genes during cocaine addiction. GAN-WGCNA enables correlation calculations between phenotype and gene expression profiles and visualizes time-series gene module interplay. We analyzed a transcriptome dataset of two weeks of cocaine self-administration in C57BL/6J mice. Utilizing GAN-WGCNA, two genes (Alcam and Celf4) were selected as missed intermediate significant genes that showed high correlation with addiction behavior. Their correlation with addictive behavior was observed to be notably significant in aspect of statistics, and their expression and co-regulation were comprehensively mapped in terms of time, brain region, and biological process.

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.

Restoring mechanophenotype reverts malignant properties of ECM-enriched vocal fold cancer

Increased extracellular matrix (ECM) and matrix stiffness promote solid tumor progression. However, mechanotransduction in cancers arising in mechanically active tissues remains underexplored. Here, we report upregulation of multiple ECM components accompanied by tissue stiffening in vocal fold cancer (VFC). We compare non-cancerous (NC) and patient-derived VFC cells - from early (mobile, T1) to advanced-stage (immobile, T3) cancers - revealing an association between VFC progression and cell-surface receptor heterogeneity, reduced laminin-binding integrin cell-cell junction localization and a flocking mode of collective cell motility. Mimicking physiological movement of healthy vocal fold tissue (stretching/vibration), decreases oncogenic nuclear β-catenin and YAP levels in VFC. Multiplex immunohistochemistry of VFC tumors uncovered a correlation between ECM content, nuclear YAP and patient survival, concordant with VFC sensitivity to YAP-TEAD inhibitors in vitro. Our findings present evidence that VFC is a mechanically sensitive malignancy and restoration of tumor mechanophenotype or YAP/TAZ targeting, represents a tractable anti-oncogenic therapeutic avenue for VFC.

Recent Advances in Nanomaterials for Modulation of Stem Cell Differentiation and Its Therapeutic Applications

Challenges in directed differentiation and survival limit the clinical use of stem cells despite their promising therapeutic potential in regenerative medicine. Nanotechnology has emerged as a powerful tool to address these challenges and enable precise control over stem cell fate. In particular, nanomaterials can mimic an extracellular matrix and provide specific cues to guide stem cell differentiation and proliferation in the field of nanotechnology. For instance, recent studies have demonstrated that nanostructured surfaces and scaffolds can enhance stem cell lineage commitment modulated by intracellular regulation and external stimulation, such as reactive oxygen species (ROS) scavenging, autophagy, or electrical stimulation. Furthermore, nanoframework-based and upconversion nanoparticles can be used to deliver bioactive molecules, growth factors, and genetic materials to facilitate stem cell differentiation and tissue regeneration. The increasing use of nanostructures in stem cell research has led to the development of new therapeutic approaches. Therefore, this review provides an overview of recent advances in nanomaterials for modulating stem cell differentiation, including metal-, carbon-, and peptide-based strategies. In addition, we highlight the potential of these nano-enabled technologies for clinical applications of stem cell therapy by focusing on improving the differentiation efficiency and therapeutics. We believe that this review will inspire researchers to intensify their efforts and deepen their understanding, thereby accelerating the development of stem cell differentiation modulation, therapeutic applications in the pharmaceutical industry, and stem cell therapeutics.

Mesenchymal stem cells biological and biotechnological advances: Implications for clinical applications

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem cells that are able to differentiate into multiple lineages including bone, cartilage, muscle and fat. They hold immunomodulatory properties and therapeutic ability to treat multiple diseases, including autoimmune and chronic degenerative diseases. In this article, we reviewed the different biological properties, applications and clinical trials of MSCs. Also, we discussed the basics of manufacturing conditions, quality control, and challenges facing MSCs in the clinical setting.

METHODS

Extensive review of the literature was conducted through the databases PubMed, Google Scholar, and Cochrane. Papers published since 2015 and covering the clinical applications and research of MSC therapy were considered. Furthermore, older papers were considered when referring to pioneering studies in the field.

RESULTS

The most widely studied stem cells in cell therapy and tissue repair are bone marrow-derived mesenchymal stem cells. Adipose tissue-derived stem cells became more common and to a lesser extent other stem cell sources e.g., foreskin derived MSCs. MSCs therapy were also studied in the setting of COVID-19 infections, ischemic strokes, autoimmune diseases, tumor development and graft rejection. Multiple obstacles, still face the standardization and optimization of MSC therapy such as the survival and the immunophenotype and the efficiency of transplanted cells. MSCs used in clinical settings displayed heterogeneity in their function despite their extraction from healthy donors and expression of similar surface markers.

CONCLUSION

Mesenchymal stem cells offer a rising therapeutic promise in various diseases. However, their potential use in clinical applications requires further investigation.

Water fluxes pattern growth and identity in shoot meristems

In multicellular organisms, tissue outgrowth creates a new water sink, modifying local hydraulic patterns. Although water fluxes are often considered passive by-products of development, their contribution to morphogenesis remains largely unexplored. Here, we mapped cell volumetric growth across the shoot apex in Arabidopsis thaliana. We found that, as organs grow, a subpopulation of cells at the organ-meristem boundary shrinks. Growth simulations using a model that integrates hydraulics and mechanics revealed water fluxes and predicted a water deficit for boundary cells. In planta, a water-soluble dye preferentially allocated to fast-growing tissues and failed to enter the boundary domain. Cell shrinkage next to fast-growing domains was also robust to different growth conditions and different topographies. Finally, a molecular signature of water deficit at the boundary confirmed our conclusion. Taken together, we propose that the differential sink strength of emerging organs prescribes the hydraulic patterns that define boundary domains at the shoot apex.

Comprehensive analysis, diagnosis, prognosis, and cordycepin (CD) regulations for GSDME expressions in pan-cancers

The Gasdermin E gene (GSDME) plays roles in deafness and cancers. However, the roles and mechanisms in cancers are complex, and the same gene exhibits different mechanisms and actions in different types of cancers. Online databases, such as GEPIA2, cBioPortal, and DNMIVD, were used to comprehensively analyze GSDME profiles, DNA methylations, mutations, diagnosis, and prognosis in patients with tumor tissues and matched healthy tissues. Western blotting and RT-PCR were used to monitor the regulation of GSDME by Cordycepin (CD) in cancer cell lines. We revealed that GSDME expression is significantly upregulated in eight cancers (ACC, DLBC, GBM, HNSC, LGG, PAAD, SKCM, and THYM) and significantly downregulated in seven cancers (COAD, KICH, LAML, OV, READ, UCES, and UCS). The overall survival was longer only in ACC, but shorter in four cancers, including COAD, KIRC, LIHC, and STAD, when GSDME was highly expressed in cancers compared with the corresponding normal tissues. Moreover, the high expression of GSDME was negatively correlated with the poor prognosis of ACC, while the low expression of GSDME was negatively correlated with the poor prognosis of COAD, suggesting that GSDME might serve as a good prognostic factor in these two cancer types. Accordingly, results indicated that the DNA methylations of those 7 CpG sites constitute a potentially effective signature to distinguish different tumors from adjacent healthy tissues. Gene mutations for GSDME were frequently observed in a variety of tumors, with UCES having the highest frequency. Moreover, CD treatment inhibited GSDME expression in different cancer cell lines, while overexpression of GSDME promoted cell migration and invasion. Thus, we have systematically and successfully clarified the GSDME expression profiles, diagnostic values, and prognostic values in pan-cancers. Targeting GSDME with CD implies therapeutic significance and a mechanism for antitumor roles in some types of cancers via increasing the sensitivity of chemotherapy. Altogether, our study may provide a strategy and biomarker for clinical diagnosis, prognostics, and treatment of cancers by targeting GSDME.

The significant role of amino acid metabolic reprogramming in cancer

Amino acid metabolism plays a pivotal role in tumor microenvironment, influencing various aspects of cancer progression. The metabolic reprogramming of amino acids in tumor cells is intricately linked to protein synthesis, nucleotide synthesis, modulation of signaling pathways, regulation of tumor cell metabolism, maintenance of oxidative stress homeostasis, and epigenetic modifications. Furthermore, the dysregulation of amino acid metabolism also impacts tumor microenvironment and tumor immunity. Amino acids can act as signaling molecules that modulate immune cell function and immune tolerance within the tumor microenvironment, reshaping the anti-tumor immune response and promoting immune evasion by cancer cells. Moreover, amino acid metabolism can influence the behavior of stromal cells, such as cancer-associated fibroblasts, regulate ECM remodeling and promote angiogenesis, thereby facilitating tumor growth and metastasis. Understanding the intricate interplay between amino acid metabolism and the tumor microenvironment is of crucial significance. Expanding our knowledge of the multifaceted roles of amino acid metabolism in tumor microenvironment holds significant promise for the development of more effective cancer therapies aimed at disrupting the metabolic dependencies of cancer cells and modulating the tumor microenvironment to enhance anti-tumor immune responses and inhibit tumor progression.

Viscoelasticity in 3D Cell Culture and Regenerative Medicine: Measurement Techniques and Biological Relevance

The field of mechanobiology is gaining prominence due to recent findings that show cells sense and respond to the mechanical properties of their environment through a process called mechanotransduction. The mechanical properties of cells, cell organelles, and the extracellular matrix are understood to be viscoelastic. Various technologies have been researched and developed for measuring the viscoelasticity of biological materials, which may provide insight into both the cellular mechanisms and the biological functions of mechanotransduction. Here, we explain the concept of viscoelasticity and introduce the major techniques that have been used to measure the viscoelasticity of various soft materials in different length- and timescale frames. The topology of the material undergoing testing, the geometry of the probe, the magnitude of the exerted stress, and the resulting deformation should be carefully considered to choose a proper technique for each application. Lastly, we discuss several applications of viscoelasticity in 3D cell culture and tissue models for regenerative medicine, including organoids, organ-on-a-chip systems, engineered tissue constructs, and tunable viscoelastic hydrogels for 3D bioprinting and cell-based therapies.

A Self-Assembled 3D Model Demonstrates How Stiffness Educates Tumor Cell Phenotypes and Therapy Resistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense and stiff extracellular matrix (ECM) associated with tumor progression and therapy resistance. To further the understanding of how stiffening of the tumor microenvironment (TME) contributes to aggressiveness, a three-dimensional (3D) self-assembling hydrogel disease model is developed based on peptide amphiphiles (PAs, PA-E3Y) designed to tailor stiffness. The model displays nanofibrous architectures reminiscent of native TME and enables the study of the invasive behavior of PDAC cells. Enhanced tuneability of stiffness is demonstrated by interacting thermally annealed aqueous solutions of PA-E3Y (PA-E3Yh) with divalent cations to create hydrogels with mechanical properties and ultrastructure similar to native tumor ECM. It is shown that stiffening of PA-E3Yh hydrogels to levels found in PDAC induces ECM deposition, promotes epithelial-to-mesenchymal transition (EMT), enriches CD133+/CXCR4+ cancer stem cells (CSCs), and subsequently enhances drug resistance. The findings reveal how a stiff 3D environment renders PDAC cells more aggressive and therefore more faithfully recapitulates in vivo tumors.

Control of epiblast cell fate by mechanical cues

In amniotes, embryonic tissues originate from multipotent epiblast cells, arranged in a mosaic of presumptive territories. How these domains fated to specific lineages become segregated during body formation remains poorly understood. Using single cell RNA sequencing analysis and lineage tracing in the chicken embryo, we identify epiblast cells contributing descendants to the neural tube, somites and lateral plate after completion of gastrulation. We show that intercalation after cell division generates important movements of epiblast cells which lead to their relocation to different presumptive territories, explaining this broad spectrum of fates. This tissue remodeling phase is transient, being soon followed by the establishment of boundaries restricting cell movements therefore defining the presumptive territories of the epiblast. Finally, we find that the epiblast faces distinct mechanical constraints along the antero-posterior axis, leading to cell fate alterations when challenged. Together, we demonstrate the critical role of mechanical cues in epiblast fate determination.

Interplay between hormonal and mechanical signals in mammary morphodynamics

Mammographic density is a well-established risk factor for breast cancer. In a recent study, Northey et al. reveal that the associated increase in tissue stiffness elevates extracellular signal-regulated kinase (ERK) activity, promoting progesterone receptor-dependent receptor activator of nuclear factor κβ (RANK) signaling. Thus, stiffness alters the context of hormonal signaling and increases mammary stem cells. This mechanism suggests potential treatments for breast cancer.

The TRIP6/LATS1 complex constitutes the tension sensor of α-catenin/vinculin at both bicellular and tricellular junctions

Cell-cell mechanotransduction regulates tissue development and homeostasis. α-catenin, the core component of adherens junctions, functions as a tension sensor and transducer by recruiting vinculin and transducing signals that influence cell behaviors. α-catenin/vinculin complex-mediated mechanotransduction regulates multiple pathways, such as Hippo pathway. However, their associations with the α-catenin-based tension sensors at cell junctions are still not fully addressed. Here, we uncovered the TRIP6/LATS1 complex co-localizes with α-catenin/vinculin at both bicellular junctions (BCJs) and tricellular junctions (TCJs). The localization of TRIP6/LATS1 complex to both TCJs and BCJs requires ROCK1 and α-catenin. Treatment by cytochalasin B, Y-27632 and blebbistatin all impaired the BCJ and TCJ junctional localization of TRIP6/LATS1, indicating that the junctional localization of TRIP6/LATS1 is mechanosensitive. The α-catenin/vinculin/TRIP6/LATS1 complex strongly localized to TCJs and exhibited a discontinuous button-like pattern on BCJs. Additionally, we developed and validated an α-catenin/vinculin BiFC-based mechanosensor that co-localizes with TRIP6/LATS1 at BCJs and TCJs. The mechanosensor exhibited a discontinuous distribution and motile signals at BCJs. Overall, our study revealed that TRIP6 and LATS1 are novel compositions of the tension sensor, together with the core complex of α-catenin/vinculin, at both the BCJs and TCJs.

Membrane to cortex attachment determines different mechanical phenotypes in LGR5+ and LGR5- colorectal cancer cells

Colorectal cancer (CRC) tumors are composed of heterogeneous and plastic cell populations, including a pool of cancer stem cells that express LGR5. Whether these distinct cell populations display different mechanical properties, and how these properties might contribute to metastasis is poorly understood. Using CRC patient derived organoids (PDOs), we find that compared to LGR5- cells, LGR5+ cancer stem cells are stiffer, adhere better to the extracellular matrix (ECM), move slower both as single cells and clusters, display higher nuclear YAP, show a higher survival rate in response to mechanical confinement, and form larger transendothelial gaps. These differences are largely explained by the downregulation of the membrane to cortex attachment proteins Ezrin/Radixin/Moesin (ERMs) in the LGR5+ cells. By analyzing single cell RNA-sequencing (scRNA-seq) expression patterns from a patient cohort, we show that this downregulation is a robust signature of colorectal tumors. Our results show that LGR5- cells display a mechanically dynamic phenotype suitable for dissemination from the primary tumor whereas LGR5+ cells display a mechanically stable and resilient phenotype suitable for extravasation and metastatic growth.

Host response during unresolved urinary tract infection alters female mammary tissue homeostasis through collagen deposition and TIMP1

Exposure to pathogens throughout a lifetime influences immunity and organ function. Here, we explore how the systemic host-response to bacterial urinary tract infection (UTI) induces tissue-specific alterations to the mammary gland. Utilizing a combination of histological tissue analysis, single cell transcriptomics, and flow cytometry, we identify that mammary tissue from UTI-bearing mice displays collagen deposition, enlarged ductal structures, ductal hyperplasia with atypical epithelial transcriptomes and altered immune composition. Bacterial cells are absent in the mammary tissue and blood of UTI-bearing mice, therefore, alterations to the distal mammary tissue are mediated by the systemic host response to local infection. Furthermore, broad spectrum antibiotic treatment resolves the infection and restores mammary cellular and tissue homeostasis. Systemically, unresolved UTI correlates with increased plasma levels of the metalloproteinase inhibitor, TIMP1, which controls extracellular matrix remodeling and neutrophil function. Treatment of nulliparous and post-lactation UTI-bearing female mice with a TIMP1 neutralizing antibody, restores mammary tissue normal homeostasis, thus providing evidence for a link between the systemic host response during UTI and mammary gland alterations.

Fabrication of gradient hydrogels using a thermophoretic approach in microfluidics

The extracellular matrix presents spatially varying physical cues that can influence cell behavior in many processes. Physical gradients within hydrogels that mimic the heterogenous mechanical microenvironment are useful to study the impact of these cues on cellular responses. Therefore, simple and reliable techniques to create such gradient hydrogels are highly desirable. This work demonstrates the fabrication of stiffness gradient Gellan gum (GG) hydrogels by applying a temperature gradient across a microchannel containing hydrogel precursor solution. Thermophoretic migration of components within the precursor solution generates a concentration gradient that mirrors the temperature gradient profile, which translates into mechanical gradients upon crosslinking. Using this technique, GG hydrogels with stiffness gradients ranging from 20 to 90 kPa over 600µm are created, covering the elastic moduli typical of moderately hard to hard tissues. MC3T3 osteoblast cells are then cultured on these gradient substrates, which exhibit preferential migration and enhanced osteogenic potential toward the stiffest region on the gradient. Overall, the thermophoretic approach provides a non-toxic and effective method to create hydrogels with defined mechanical gradients at the micron scale suitable forin vitrobiological studies and potentially tissue engineering applications.

Emergence of nanoscale viscoelasticity from single cancer cells to established tumors

Tumors are complex materials whose physical properties dictate growth and treatment outcomes. Recent evidence suggests time-dependent physical properties, such as viscoelasticity, are crucial, distinct mechanical regulators of cancer progression and malignancy, yet the genesis and consequences of tumor viscoelasticity are poorly understood. Here, using Wide-bandwidth AFM-based ViscoElastic Spectroscopy (WAVES) coupled with mathematical modeling, we probe the origins of tumor viscoelasticity. From single carcinoma cells to increasingly sized carcinoma spheroids to established tumors, we describe a stepwise evolution of dynamic mechanical properties that create a nanorheological signature of established tumors: increased stiffness, decreased rate-dependent stiffening, and reduced energy dissipation. We dissect this evolution of viscoelasticity by scale, and show established tumors use fluid-solid interactions as the dominant mechanism of mechanical energy dissipation as opposed to fluid-independent intrinsic viscoelasticity. Additionally, we demonstrate the energy dissipation mechanism in spheroids and established tumors is negatively correlated with the cellular density, and this relationship strongly depends on an intact actin cytoskeleton. These findings define an emergent and targetable signature of the physical tumor microenvironment, with potential for deeper understanding of tumor pathophysiology and treatment strategies.

A Hierarchical Mechanotransduction System: From Macro to Micro

Mechanotransduction is a strictly regulated process whereby mechanical stimuli, including mechanical forces and properties, are sensed and translated into biochemical signals. Increasing data demonstrate that mechanotransduction is crucial for regulating macroscopic and microscopic dynamics and functionalities. However, the actions and mechanisms of mechanotransduction across multiple hierarchies, from molecules, subcellular structures, cells, tissues/organs, to the whole-body level, have not been yet comprehensively documented. Herein, the biological roles and operational mechanisms of mechanotransduction from macro to micro are revisited, with a focus on the orchestrations across diverse hierarchies. The implications, applications, and challenges of mechanotransduction in human diseases are also summarized and discussed. Together, this knowledge from a hierarchical perspective has the potential to refresh insights into mechanotransduction regulation and disease pathogenesis and therapy, and ultimately revolutionize the prevention, diagnosis, and treatment of human diseases.

The Role of Mechanotransduction in Contact Inhibition of Locomotion and Proliferation

Contact inhibition (CI) represents a crucial tumor-suppressive mechanism responsible for controlling the unbridled growth of cells, thus preventing the formation of cancerous tissues. CI can be further categorized into two distinct yet interrelated components: CI of locomotion (CIL) and CI of proliferation (CIP). These two components of CI have historically been viewed as separate processes, but emerging research suggests that they may be regulated by both distinct and shared pathways. Specifically, recent studies have indicated that both CIP and CIL utilize mechanotransduction pathways, a process that involves cells sensing and responding to mechanical forces. This review article describes the role of mechanotransduction in CI, shedding light on how mechanical forces regulate CIL and CIP. Emphasis is placed on filamin A (FLNA)-mediated mechanotransduction, elucidating how FLNA senses mechanical forces and translates them into crucial biochemical signals that regulate cell locomotion and proliferation. In addition to FLNA, trans-acting factors (TAFs), which are proteins or regulatory RNAs capable of directly or indirectly binding to specific DNA sequences in distant genes to regulate gene expression, emerge as sensitive players in both the mechanotransduction and signaling pathways of CI. This article presents methods for identifying these TAF proteins and profiling the associated changes in chromatin structure, offering valuable insights into CI and other biological functions mediated by mechanotransduction. Finally, it addresses unanswered research questions in these fields and delineates their possible future directions.

Tension-induced adhesion mode switching: the interplay between focal adhesions and clathrin-containing adhesion complexes

Integrin-based adhesion complexes are crucial in various cellular processes, including proliferation, differentiation, and motility. While the dynamics of canonical focal adhesion complexes (FAs) have been extensively studied, the regulation and physiological implications of the recently identified clathrin-containing adhesion complexes (CCACs) are still not well understood. In this study, we investigated the spatiotemporal mechanoregulations of FAs and CCACs in a breast cancer model. Employing single-molecule force spectroscopy coupled with live-cell fluorescence microscopy, we discovered that FAs and CCACs are mutually exclusive and inversely regulated complexes. This regulation is orchestrated through the modulation of plasma membrane tension, in combination with distinct modes of actomyosin contractility that can either synergize with or counteract this modulation. Our findings indicate that increased membrane tension promotes the association of CCACs at integrin αVβ5 adhesion sites, leading to decreased cancer cell proliferation, spreading, and migration. Conversely, lower membrane tension promotes the formation of FAs, which correlates with the softer membranes observed in cancer cells, thus potentially facilitating cancer progression. Our research provides novel insights into the biomechanical regulation of CCACs and FAs, revealing their critical and contrasting roles in modulating cancer cell progression.

Regulation of protein synthesis and stability by mechanical cues and its implications in cancer

Elevated tissue stiffness is a common feature of many solid tumors and the downstream mechanical signaling affects many cellular processes and contributes to cancer progression. Significant progress has been made in understanding how the mechanical properties of the matrix affect cancer cell behavior as well as transcription. However, how the same mechanical cues impact protein synthesis and stability and how this may contribute to disease is less well understood. Here, we present emerging evidence that cancer progression is frequently supported by gene regulation acting beyond the mRNA level and highlight some of the known crosstalk between this type of regulation and mechanotransduction in cancer as well as in other contexts. We suggest that future systematic approaches to define mechanosensitive translatomes and proteomes and how these are controlled may provide novel targets for cancer therapy.

Spatial Transcriptomics Suggests That Alterations Occur in the Preneoplastic Breast Microenvironment of BRCA1/2 Mutation Carriers

Breast cancer is the most common cancer in females, affecting one in every eight women and accounting for the majority of cancer-related deaths in women worldwide. Germline mutations in the BRCA1 and BRCA2 genes are significant risk factors for specific subtypes of breast cancer. BRCA1 mutations are associated with basal-like breast cancers, whereas BRCA2 mutations are associated with luminal-like disease. Defects in mammary epithelial cell differentiation have been previously recognized in germline BRCA1/2 mutation carriers even before cancer incidence. However, the underlying mechanism is largely unknown. Here, we employ spatial transcriptomics to investigate defects in mammary epithelial cell differentiation accompanied by distinct microenvironmental alterations in preneoplastic breast tissues from BRCA1/2 mutation carriers and normal breast tissues from noncarrier controls. We uncovered spatially defined receptor-ligand interactions in these tissues for the investigation of autocrine and paracrine signaling. We discovered that β1-integrin-mediated autocrine signaling in BRCA2-deficient mammary epithelial cells may differ from BRCA1-deficient mammary epithelial cells. In addition, we found that the epithelial-to-stromal paracrine signaling in the breast tissues of BRCA1/2 mutation carriers is greater than in control tissues. More integrin-ligand pairs were differentially correlated in BRCA1/2-mutant breast tissues than noncarrier breast tissues with more integrin receptor-expressing stromal cells.

IMPLICATIONS

These results suggest alterations in the communication between mammary epithelial cells and the microenvironment in BRCA1 and BRCA2 mutation carriers, laying the foundation for designing innovative breast cancer chemo-prevention strategies for high-risk patients.

Loss of NAT10 disrupts enhancer organization via p300 mislocalization and suppresses transcription of genes necessary for metastasis progression

Acetylation of protein and RNA represent a critical event for development and cancer progression. NAT10 is the only known RNA acetylase that catalyzes the N4-actylcytidine (ac4C) modification of RNAs. Here, we show that the loss of NAT10 significantly decreases lung metastasis in allograft and genetically engineered mouse models of breast cancer. NAT10 interacts with a mechanosensitive, metastasis susceptibility protein complex at the nuclear pore. In addition to its canonical role in RNA acetylation, we find that NAT10 interacts with p300 at gene enhancers. NAT10 loss is associated with p300 mislocalization into heterochromatin regions. NAT10 depletion disrupts enhancer organization, leading to alteration of gene transcription necessary for metastatic progression, including reduced myeloid cell-recruiting chemokines that results in a less metastasis-prone tumor microenvironment. Our study uncovers a distinct role of NAT10 in enhancer organization of metastatic tumor cells and suggests its involvement in the tumor-immune crosstalk dictating metastatic outcomes.

Mechanosensitive hormone signaling promotes mammary progenitor expansion and breast cancer risk

Tissue stem-progenitor cell frequency has been implicated in tumor risk and progression, but tissue-specific factors linking these associations remain ill-defined. We observed that stiff breast tissue from women with high mammographic density, who exhibit increased lifetime risk for breast cancer, associates with abundant stem-progenitor epithelial cells. Using genetically engineered mouse models of elevated integrin mechanosignaling and collagen density, syngeneic manipulations, and spheroid models, we determined that a stiff matrix and high mechanosignaling increase mammary epithelial stem-progenitor cell frequency and enhance tumor initiation in vivo. Augmented tissue mechanics expand stemness by potentiating extracellular signal-related kinase (ERK) activity to foster progesterone receptor-dependent RANK signaling. Consistently, we detected elevated phosphorylated ERK and progesterone receptors and increased levels of RANK signaling in stiff breast tissue from women with high mammographic density. The findings link fibrosis and mechanosignaling to stem-progenitor cell frequency and breast cancer risk and causally implicate epidermal growth factor receptor-ERK-dependent hormone signaling in this phenotype.