Introduction: Collagen type VIII alpha 1 is enriched in atherosclerotic lesions and vascular remodeling, but its contribution to endothelial mechanics and signaling is not well defined. Hypothesis: We tested the hypothesis that collagen type VIII alpha 1 (COL8A1) regulates endothelial cytoskeletal organization, mechanical stiffness, and delta-like ligand 4 (DLL4)-related NOTCH signaling. Methods: Single-cell RNA sequencing of human atherosclerotic carotid artery endothelium was used to identify COL8A1-associated endothelial populations. Functional studies were performed in cultured human aortic endothelial cells using COL8A1 knockdown and recombinant COL8A1. Cytoskeletal organization, cellular stiffness, and deformability were assessed by immunofluorescence, atomic force microscopy, and microfiltration or microfluidic deformation assays, with measurements performed on multiple cells per condition. Transcriptomic profiling was used to assess pathway-level changes. Results: COL8A1 expression was enriched in endothelial subpopulations exhibiting angiogenic, migratory, inflammatory, and cytoskeletal transcriptional programs. COL8A1 knockdown impaired endothelial migration, disrupted actin and microtubule organization, reduced PI3K/Akt signaling, decreased cellular stiffness, and increased deformability. These mechanical defects were partially rescued by recombinant COL8A1, consistent with a matrix-dependent contribution to endothelial biomechanics. Recombinant COL8A1 increased expression of axon guidance-related genes, VEGFR2, PECAM1, and cytoskeletal fiber-associated transcripts. COL8A1 also altered NOTCH signaling, characterized by increased DLL4 expression with reduced nuclear NOTCH intracellular domain levels, consistent with a tip cell-like endothelial state. Conversely, COL8A1 knockdown attenuated VEGFA-induced DLL4 expression. Disruption of actomyosin contractility with blebbistatin suppressed recombinant COL8A1-induced DLL4 upregulation. Conclusions: In conclusion, COL8A1 expression is associated with endothelial cytoskeletal organization, mechanical stiffness, and DLL4 expression in endothelial activation, suggesting a role in matrix-dependent regulation of endothelial mechanics during vascular remodeling.

Background: Patients with systemic sclerosis have a significantly increased incidence of developing various solid malignancies within a few years of systemic sclerosis onset, but the mechanism of tumor promotion is not well understood. The tight skin (TSK) mouse has been a valuable model for investigating systemic sclerosis-related pathologies due to increased extracellular matrix deposition, fibrosis in connective tissues, and altered immune cell activation. Despite the role of extracellular matrix and fibrosis in cancer progression, the potential of the TSK mouse as a model for cancer studies is unexplored. Methods: To investigate the impact of the altered microenvironment in TSK mice on cancer progression, we compared the tumor-forming capabilities (by subcutaneous and intraperitoneal injection) in TSK mice and WT mice using syngeneic breast cancer, melanoma, and ovarian cancer cell lines. We used bulk and single-cell RNA sequencing to characterize these tumors and identify the changes in the TSK microenvironment that promote cancer formation. Results: In all three cancer types, TSK mice exhibited more invasive subcutaneous tumors in comparison to WT controls, underscoring the role of the TSK subcutaneous microenvironment in promoting cancer progression. Furthermore, the heightened invasiveness of ovarian tumors implanted intraperitoneally suggests that the peritoneal microenvironment in TSK mice also promotes tumor progression. Single-cell RNA sequencing analyses of subcutaneous tumors from TSK and WT mice revealed tumor-specific changes in the composition and phenotype of various cell populations. The most consistent alteration in TSK mice included a higher neutrophil-to-lymphocyte ratio and an enrichment in profibrotic subpopulations of myofibroblasts and macrophages. Conclusions: Our research unveils the TSK mouse as a valuable model for studying the intricate connections between systemic sclerosis and cancer

The ability of cancer cells to deform and generate force is implicated in metastasis. We previously showed that β-adrenergic agonists increase cancer cell stiffness, which was associated with enhanced motility and invasion. Here, we investigate how β-adrenoceptor (βAR) activation alters the mechanical behaviors of triple-negative breast cancer cells. We find that βAR activation increases traction forces in metastatic MDA-MB-231HM and MDA-MB-468 cells, but not in non-tumorigenic MCF10A cells. Using computational modeling, we show that βAR activation increases the number of active myosin motors via myosin light chain phosphorylation. To identify molecular regulators, we use a deformability assay to screen for pharmacologic and genetic perturbations. Our results define a βAR-RhoA-ROCK-non-muscle myosin II (NMII) signaling axis that modulates the mechanical behaviors of MDA-MB-231HM and MDA-MB-468 cells. These findings provide insight into how stress signaling regulates cancer cell mechanics and suggest potential targets to block metastasis in triple-negative breast cancer.

To illustrate how physics concepts play a role in cell biology and tissue formation, cell mechanics and mechanobiology are fascinating educational topics. However, the field currently lacks hands-on activities that engage students in learning science in these topics. One example is the creation of hands-on modules that would allow students to actively observe morphological aspects of cells and connect them to fundamental physics principles. In this talk, I will describe a workflow that engages students in studying epithelial cell mechanics using commercial histology slides of frog skin.

Tuning of genome structure and function is accomplished by chromatin-binding proteins, which determine the transcriptome and phenotype of the cell. Here we investigate how communication between extracellular stress and chromatin structure may regulate cellular mechanical behaviors. We demonstrate that histone H1.0, which compacts nucleosomes into higher-order chromatin fibers, controls genome organization and cellular stress response. We show that histone H1.0 has privileged expression in fibroblasts across tissue types and that its expression is necessary and sufficient to induce myofibroblast activation. Depletion of histone H1.0 prevents cytokine-induced fibroblast contraction, proliferation and migration via inhibition of a transcriptome comprising extracellular matrix, cytoskeletal and contractile genes, through a process that involves locus-specific H3K27 acetylation. Transient depletion of histone H1.0 in vivo prevents fibrosis in cardiac muscle. These findings identify an unexpected role of linker histones to orchestrate cellular mechanical behaviors, directly coupling force generation, nuclear organization and gene transcription. Hu et al. describe how histone H1.0 regulates myofibroblast activation, linking force generation to nuclear organization and gene transcription.

There is increasing consumer demand for alternative animal protein products that are delicious and sustainably produced to address concerns about the impacts of mass-produced meat on human and planetary health. Cultured meat has the potential to provide a source of nutritious dietary protein that both is palatable and has reduced environmental impact. However, strategies to support the production of cultured meats at the scale required for food consumption will be critical. In this review, we discuss the current challenges and opportunities of using edible scaffolds for scaling up the production of cultured meat. We provide an overview of different types of edible scaffolds, scaffold fabrication techniques, and common scaffold materials. Finally, we highlight potential advantages of using edible scaffolds to advance cultured meat production by accelerating cell growth and differentiation, providing structure to build complex 3D tissues, and enhancing the nutritional and sensory properties of cultured meat.

A new device termed "Optomagnetic Micromirror Arrays" (OMA) is demonstrated capable of mapping the stiffness distribution of biomimetic materials across a 5.1 mm x 7.2 mm field of view with cellular resolution. The OMA device comprises an array of 50 000 magnetic micromirrors with optical grating structures embedded beneath an elastic PDMS film, with biomimetic materials affixed on top. Illumination of a broadband white light beam onto these micromirrors results in the reflection of microscale rainbow light rays on each micromirror. When a magnetic field is applied, it causes each micromirror to tilt differently depending on the local stiffness of the biomimetic materials. Through imaging these micromirrors with low N.A. optics, a specific narrow band of reflection light rays from each micromirror is captured. Changing a micromirror's tilt angle also alters the color spectrum it reflects back to the imaging system and the color of the micromirror image it represents. As a result, OMA can infer the local stiffness of the biomimetic materials through the color change detected on each micromirror. OMA offers the potential for high-throughput stiffness mapping at the tissue-level while maintaining spatial resolution at the cellular level.

The recurrence of cancer following chemotherapy treatment is a major cause of death across solid and hematologic cancers. In B-cell acute lymphoblastic leukemia (B-ALL), relapse after initial chemotherapy treatment leads to poor patient outcomes. Here we test the hypothesis that chemotherapy-treated versus control B-ALL cells can be characterized based on cellular physical phenotypes. To quantify physical phenotypes of chemotherapy-treated leukemia cells, we use cells derived from B-ALL patients that are treated for 7 days with a standard multidrug chemotherapy regimen of vincristine, dexamethasone, and L-asparaginase (VDL). We conduct physical phenotyping of VDL-treated versus control cells by tracking the sequential deformations of single cells as they flow through a series of micron-scale constrictions in a microfluidic device; we call this method Quantitative Cyclical Deformability Cytometry. Using automated image analysis, we extract time-dependent features of deforming cells including cell size and transit time (TT) with single-cell resolution. Our findings show that VDL-treated B-ALL cells have faster TTs and transit velocity than control cells, indicating that VDL-treated cells are more deformable. We then test how effectively physical phenotypes can predict the presence of VDL-treated cells in mixed populations of VDL-treated and control cells using machine learning approaches. We find that TT measurements across a series of sequential constrictions can enhance the classification accuracy of VDL-treated cells in mixed populations using a variety of classifiers. Our findings suggest the predictive power of cell physical phenotyping as a complementary prognostic tool to detect the presence of cells that survive chemotherapy treatment. Ultimately such complementary physical phenotyping approaches could guide treatment strategies and therapeutic interventions. Insight box Cancer cells that survive chemotherapy treatment are major contributors to patient relapse, but the ability to predict recurrence remains a challenge. Here we investigate the physical properties of leukemia cells that survive treatment with chemotherapy drugs by deforming individual cells through a series of micron-scale constrictions in a microfluidic channel. Our findings reveal that leukemia cells that survive chemotherapy treatment are more deformable than control cells. We further show that machine learning algorithms applied to physical phenotyping data can predict the presence of cells that survive chemotherapy treatment in a mixed population. Such an integrated approach using physical phenotyping and machine learning could be valuable to guide patient treatments.

Epithelial mechanics and mechanobiology have become 2 important research fields in life sciences and bioengineering. These fields investigate how physical factors induced by cell adhesion and collective behaviors can directly regulate biologic processes, such as organ development and disease progression. Cell mechanics and mechanobiology thus make exciting biophysics education topics to illustrate how fundamental physics principles play a role in regulating cell biology. However, the field currently lacks hands-on activities that engage students in learning science and outreach programs in these topics. One such area is the development of robust hands-on modules that allow students to observe features of cell shape and mechanics and connect them to fundamental physics principles. Here, we demonstrate a workflow that engages students in studying epithelial cell mechanics by using commercial histology slides of frog skin. We show that by using recently developed artificial intelligence-based image-segmentation tools, students can easily quantify different cell morphologic features in a high-throughput manner. Using our workflow, students can reproduce 2 essential findings in cell mechanics: the common gamma distribution of normalized cell aspect ratio in jammed epithelia and the constant ratio between the nuclear and cellular area. Importantly, because the only required instrument for this active learning module is a readily available light microscope and a computer, our module is relatively low cost, as well as portable. These features make the module scalable for students at various education levels and outreach programs. This highly accessible education module provides a fun and engaging way to introduce students to the world of epithelial tissue mechanics.

The integration of intramuscular fat-or marbling-into cultured meat will be critical for meat texture, mouthfeel, flavor, and thus consumer appeal. However, culturing muscle tissue with marbling is challenging since myocytes and adipocytes have different media and scaffold requirements for optimal growth and differentiation. Here, we present an approach to engineer multicomponent tissue using myogenic and adipogenic microtissues. The key innovation in our approach is the engineering of myogenic and adipogenic microtissues using scaffolds with customized physical properties; we use these microtissues as building blocks that spontaneously adhere to produce multicomponent tissue, or marbled cultured meat. Myocytes are grown and differentiated on gelatin nanofiber scaffolds with aligned topology that mimic the aligned structure of skeletal muscle and promotes the formation of myotubes in both primary rabbit skeletal muscle and murine C2C12 cells. Preadipocytes are cultured and differentiated on edible gelatin microbead scaffolds, which are customized to have a physiologically-relevant stiffness, and promote lipid accumulation in both primary rabbit and murine 3T3-L1 pre-adipocytes. After harvesting and stacking the individual myogenic and adipogenic microtissues, we find that the resultant multicomponent tissues adhere into intact structures within 6-12 h in culture. The resultant multicomponent 3D tissue constructs show behavior of a solid material with a Young's modulus of -2 & PLUSMN; 0.4 kPa and an ultimate tensile strength of -23 & PLUSMN; 7 kPa without the use of additional crosslinkers. Using this approach, we generate marbled cultured meat with -mm to -cm thickness, which has a protein content of -4 & PLUSMN; 2 g/100 g that is comparable to a conventionally produced Wagyu steak with a protein content of -9 & PLUSMN; 4 g/ 100 g. We show the translatability of this layer-by-layer assembly approach for microtissues across primary rabbit cells, murine cell lines, as well as for gelatin and plant-based scaffolds, which demonstrates a strategy to generate edible marbled meats derived from different species and scaffold materials.

The role of transcription factors and biomolecules in cell type conversion has been widely studied. Yet, it remains unclear whether and how intracellular mechanotransduction through focal adhesions (FAs) and the cytoskeleton regulates the epigenetic state and cell reprogramming. Here, it is shown that cytoskeletal structures and the mechanical properties of cells are modulated during the early phase of induced neuronal (iN) reprogramming, with an increase in actin cytoskeleton assembly induced by Ascl1 transgene. The reduction of actin cytoskeletal tension or cell adhesion at the early phase of reprogramming suppresses the expression of mesenchymal genes, promotes a more open chromatin structure, and significantly enhances the efficiency of iN conversion. Specifically, reduction of intracellular tension or cell adhesion not only modulates global epigenetic marks, but also decreases DNA methylation and heterochromatin marks and increases euchromatin marks at the promoter of neuronal genes, thus enhancing the accessibility for gene activation. Finally, micro- and nano-topographic surfaces that reduce cell adhesions enhance iN reprogramming. These novel findings suggest that the actin cytoskeleton and FAs play an important role in epigenetic regulation for cell fate determination, which may lead to novel engineering approaches for cell reprogramming.

3D image of nuclear membrane blebbing and emerin mislocalization in BT-549 DIAPH3-depleted cells. DNA (Hoechst, blue), emerin (FITC, green) and membrane (1,1'-Dioctadecyl-3,3,3',3'-Tetramethylindocarbocyanine Perchlorate, Dil, red) staining are shown.

With rising global demand for food proteins and significant environmental impact associated with conventional animal agriculture, it is important to develop sustainable alternatives to supplement existing meat production. Since fat is an important contributor to meat flavor, recapitulating this component in meat alternatives such as plant based and cell cultured meats is important. Here, we discuss the topic of cell cultured or tissue engineered fat, growing adipocytes in vitro that could imbue meat alternatives with the complex flavor and aromas of animal meat. We outline potential paths for the large scale production of in vitro cultured fat, including adipogenic precursors during cell proliferation, methods to adipogenically differentiate cells at scale, as well as strategies for converting differentiated adipocytes into 3D cultured fat tissues. We showcase the maturation of knowledge and technology behind cell sourcing and scaled proliferation, while also highlighting that adipogenic differentiation and 3D adipose tissue formation at scale need further research. We also provide some potential solutions for achieving adipose cell differentiation and tissue formation at scale based on contemporary research and the state of the field.

PODXL, a protein that is dysregulated in multiple cancers, plays an important role in promoting cancer metastasis. In this study, we report that RNA editing promotes the inclusion of a PODXL alternative exon. The resulting edited PODXL long isoform is more prone to protease digestion and has the strongest effects on reducing cell migration and cisplatin chemoresistance among the three PODXL isoforms (short, unedited long, and edited long isoforms). Importantly, the editing level of the PODXL recoding site and the inclusion level of the PODXL alternative exon are strongly associated with overall patient survival in Kidney Renal Clear Cell Carcinoma (KIRC). Supported by significant enrichment of exonic RNA editing sites in alternatively spliced exons, we hypothesize that exonic RNA editing sites may enhance proteomic diversity through alternative splicing, in addition to amino acid changes, a previously under-appreciated aspect of RNA editing function.