How cells respond to environmental cues - insights from bio-functionalized substrates

Mesenchymal cell migration on one-dimensional micropatterns

Quantitative studies of mesenchymal cell motion are important to elucidate cytoskeleton function and mechanisms of cell migration. To this end, confinement of cell motion to one dimension (1D) significantly simplifies the problem of cell shape in experimental and theoretical investigations. Here we review 1D migration assays employing micro-fabricated lanes and reflect on the advantages of such platforms. Data are analyzed using biophysical models of cell migration that reproduce the rich scenario of morphodynamic behavior found in 1D. We describe basic model assumptions and model behavior. It appears that mechanical models explain the occurrence of universal relations conserved across different cell lines such as the adhesion-velocity relation and the universal correlation between speed and persistence (UCSP). We highlight the unique opportunity of reproducible and standardized 1D assays to validate theory based on statistical measures from large data of trajectories and discuss the potential of experimental settings embedding controlled perturbations to probe response in migratory behavior.

Microfabrication approaches for oral research and clinical dentistry

Currently, there is a variety of laboratory tools and strategies that have been developed to investigate in-vivo processes using in-vitro models. Amongst these, microfabrication represents a disruptive technology that is currently enabling next-generation biomedical research through the development of complex laboratory approaches (e.g., microfluidics), engineering of micrometer scale sensors and actuators (micropillars for traction force microscopy), and the creation of environments mimicking cell, tissue, and organ-specific contexts. Although microfabrication has been around for some time, its application in dental and oral research is still incipient. Nevertheless, in recent years multiple lines of research have emerged that use microfabrication-based approaches for the study of oral diseases and conditions with micro- and nano-scale sensitivities. Furthermore, many investigations are aiming to develop clinically relevant microfabrication-based applications for diagnostics, screening, and oral biomaterial manufacturing. Therefore, the objective of this review is to summarize the current application of microfabrication techniques in oral sciences, both in research and clinics, and to discuss possible future applications of these technologies for in-vitro studies and practical patient care. Initially, this review provides an overview of the most employed microfabrication methods utilized in biomedicine and dentistry. Subsequently, the use of micro- and nano-fabrication approaches in relevant fields of dental research such as endodontic and periodontal regeneration, biomaterials research, dental implantology, oral pathology, and biofilms was discussed. Finally, the current and future uses of microfabrication technology for clinical dentistry and how these approaches may soon be widely available in clinics for the diagnosis, prevention, and treatment of relevant pathologies are presented.

Selective Positioning of Different Cell Types on 3D Scaffolds via DNA Hybridization

Three-dimensional (3D) microscaffolds for cell biology have shown their potential in mimicking physiological environments and simulating complex multicellular constructs. However, controlling the localization of cells precisely on microfabricated structures is still complex and usually limited to two-dimensional assays. Indeed, the implementation of an efficient method to selectively target different cell types to specific regions of a 3D microscaffold would represent a decisive step toward cell-by-cell assembly of complex cellular arrangements. Here, we use two-photon lithography (2PL) to fabricate 3D microarchitectures with functional photoresists. UV-mediated click reactions are used to functionalize their surfaces with single-stranded DNA oligonucleotides, using sequential repetition to decorate different scaffold regions with individual DNA addresses. Various immortalized cell lines and stem cells modified by grafting complementary oligonucleotides onto the phospholipid membranes can then be immobilized onto complementary regions of the 3D structures by selective hybridization. This allows controlled cocultures to be established with spatially separated arrays of eukaryotic cells in 3D.

Adaptation of cell spreading to varying fibronectin densities and topographies is facilitated by β1 integrins

Cells mechanical behaviour in physiological environments is mediated by interactions with the extracellular matrix (ECM). In particular, cells can adapt their shape according to the availability of ECM proteins, e.g., fibronectin (FN). Several in vitro experiments usually simulate the ECM by functionalizing the surfaces on which cells grow with FN. However, the mechanisms underlying cell spreading on non-uniformly FN-coated two-dimensional substrates are not clarified yet. In this work, we studied cell spreading on variously functionalized substrates: FN was either uniformly distributed or selectively patterned on flat surfaces, to show that A549, BRL, B16 and NIH 3T3 cell lines are able to sense the overall FN binding sites independently of their spatial arrangement. Instead, only the total amount of available FN influences cells spreading area, which positively correlates to the FN density. Immunocytochemical analysis showed that β1 integrin subunits are mainly responsible for this behaviour, as further confirmed by spreading experiments with β1-deficient cells. In the latter case, indeed, cells areas do not show a dependency on the amount of available FN on the substrates. Therefore, we envision for β1 a predominant role in cells for sensing the number of ECM ligands with respect to other focal adhesion proteins.

CNS Organoid Surpasses Cell-Laden Microgel Assembly to Promote Spinal Cord Injury Repair

The choice of therapeutic agents remains an unsolved issue in the repair of spinal cord injury. In this work, various agents and configurations were investigated and compared for their performance in promoting nerve regeneration, including bead assembly and bulk gel of collagen and Matrigel, under acellular and cell-laden conditions, and cerebral organoid (CO) as the in vitro preorganized agent. First, in Matrigel-based agents and the CO transplantations, the recipient animal gained more axon regeneration and the higher Basso, Beattie, and Bresnahan (BBB) scoring than the grafted collagen gels. Second, new nerves more uniformly infiltrated into the transplants in bead form assembly than the molded chunks. Third, the materials loaded the neural progenitor cells (NPCs) or the CO implantation groups received more regenerated nerve fibers than their acellular counterparts, suggesting the necessity to transplant exogenous cells for large trauma (e.g., a 5 mm long spinal cord transect). In addition, the activated microglial cells might benefit from neural regeneration after receiving CO transplantation in the recipient animals. The organoid augmentation may suggest that in vitro maturation of a microtissue complex is necessary before transplantation and proposes organoids as the premium therapeutic agents for nerve regeneration.

Mimicking the Natural Basement Membrane for Advanced Tissue Engineering

Advancements in the field of tissue engineering have led to the elucidation of physical and chemical characteristics of physiological basement membranes (BM) as specialized forms of the extracellular matrix. Efforts to recapitulate the intricate structure and biological composition of the BM have encountered various advancements due to its impact on cell fate, function, and regulation. More attention has been paid to synthesizing biocompatible and biofunctional fibrillar scaffolds that closely mimic the natural BM. Specific modifications in biomimetic BM have paved the way for the development of in vitro models like alveolar-capillary barrier, airway models, skin, blood-brain barrier, kidney barrier, and metastatic models, which can be used for personalized drug screening, understanding physiological and pathological pathways, and tissue implants. In this Review, we focus on the structure, composition, and functions of in vivo BM and the ongoing efforts to mimic it synthetically. Light has been shed on the advantages and limitations of various forms of biomimetic BM scaffolds including porous polymeric membranes, hydrogels, and electrospun membranes This Review further elaborates and justifies the significance of BM mimics in tissue engineering, in particular in the development of in vitro organ model systems.

A Co-Polymerizable Linker for the Covalent Attachment of Fibronectin Makes pHEMA Hydrogels Cell-Adhesive

Hydrogels are attractive biomaterials because their chemical and mechanical properties can be tailored to mimic those of biological tissues. However, many hydrogels do not allow cell or protein attachment. Therefore, they are post-synthetically functionalized by adding functional groups for protein binding, which then allows cell adhesion in cell culture substrates. However, the degree of functionalization and covalent binding is difficult to analyze in these cases. Moreover, the density of the functional groups and the homogeneity of their distribution is hard to control. This work introduces another strategy for the biofunctionalization of hydrogels: we synthesized a polymerizable linker that serves as a direct junction between the polymeric structure and cell adhesion proteins. This maleimide-containing, polymerizable bio-linker was copolymerized with non-functionalized monomers to produce a bioactive hydrogel based on poly(2-hydroxyethyl methacrylate) (pHEMA). Therefore, the attachment site was only controlled by the polymerization process and was thus uniformly distributed throughout the hydrogel. In this way, the bio-conjugation by a protein-binding thiol-maleimide Michael-type reaction was possible in the entire hydrogel matrix. This approach enabled a straightforward and highly effective biofunctionalization of pHEMA with the adhesion protein fibronectin. The bioactivity of the materials was demonstrated by the successful adhesion of fibroblast cells.

Engineering Three-Dimensional Vascularized Cardiac Tissues

Heart disease is one of the largest burdens to human health worldwide and has very limited therapeutic options. Engineered three-dimensional (3D) vascularized cardiac tissues have shown promise in rescuing cardiac function in diseased hearts and may serve as a whole organ replacement in the future. One of the major obstacles in reconstructing these thick myocardial tissues to a clinically applicable scale is the integration of functional vascular networks capable of providing oxygen and nutrients throughout whole engineered constructs. Without perfusion of oxygen and nutrient flow throughout the entire engineered tissue not only is tissue viability compromised, but also overall tissue functionality is lost. There are many supporting technologies and approaches that have been developed to create vascular networks such as 3D bioprinting, co-culturing hydrogels, and incorporation of soluble angiogenic factors. In this state-of-the-art review, we discuss some of the most current engineered vascular cardiac tissues reported in the literature and future directions in the field. Impact statement The field of cardiac tissue engineering is rapidly evolving and is now closer than ever to having engineered tissue models capable of predicting preclinical responses to therapeutics, modeling diseases, and being used as a means of rescuing cardiac function following injuries to the native myocardium. However, a major obstacle of engineering thick cardiac tissue remains to be the integration of functional vasculature. In this review, we highlight seminal and recently published works that have influenced and pushed the field of cardiac tissue engineering toward achieving vascularized functional tissues.

Principles for the design of multicellular engineered living systems

Remarkable progress in bioengineering over the past two decades has enabled the formulation of fundamental design principles for a variety of medical and non-medical applications. These advancements have laid the foundation for building multicellular engineered living systems (M-CELS) from biological parts, forming functional modules integrated into living machines. These cognizant design principles for living systems encompass novel genetic circuit manipulation, self-assembly, cell-cell/matrix communication, and artificial tissues/organs enabled through systems biology, bioinformatics, computational biology, genetic engineering, and microfluidics. Here, we introduce design principles and a blueprint for forward production of robust and standardized M-CELS, which may undergo variable reiterations through the classic design-build-test-debug cycle. This Review provides practical and theoretical frameworks to forward-design, control, and optimize novel M-CELS. Potential applications include biopharmaceuticals, bioreactor factories, biofuels, environmental bioremediation, cellular computing, biohybrid digital technology, and experimental investigations into mechanisms of multicellular organisms normally hidden inside the "black box" of living cells.

In Situ Agarose Microfabrication Technology Using Joule Heating of Micro Ionic Current for On-Chip Cell Network Analysis

Agarose microfabrication technology is one of the micropatterning techniques of cells having advantages of simple and flexible real-time fabrication of three-dimensional confinement microstructures even during cell cultivation. However, the conventional photothermal etching procedure of focused infrared laser on thin agarose layer has several limitations, such as the undesired sudden change of etched width caused by the local change of absorbance of the bottom surface of cultivation plate, especially on the indium-tin-oxide (ITO) wiring on the multi-electrode array (MEA) cultivation chip. To overcome these limitations, we have developed a new agarose etching method exploiting the Joule heating of focused micro ionic current at the tip of the micrometer-sized capillary tube. When 75 V, 1 kHz AC voltage was applied to the tapered microcapillary tube, in which 1 M sodium ion buffer was filled, the formed micro ionic current at the open end of the microcapillary tube melted the thin agarose layer and formed stable 5 μm width microstructures regardless the ITO wiring, and the width was controlled by the change of applied voltage squared. We also found the importance of the higher frequency of applied AC voltage to form the stable microstructures and also minimize the fluctuation of melted width. The results indicate that the focused micro ionic current can create stable local spot heating in the medium buffer as the Joule heating of local ionic current and can perform the same quality of microfabrication as the focused infrared laser absorption procedure with a simple set-up of the system and several advantages.

Developing biomaterials to mediate the spatial distribution of integrins

Innovation in material design to regulate cell behavior and function is one of the primary tasks in materials science. Integrins, a family of cell surface-adhesion receptors that mechanically connect the extracellular matrix (ECM) to the intracellular cytoskeleton, have long served as primary targets for the design of biomaterials because their activity is not only critical to a wide range of cell and tissue functions but also subject to very tight and complex regulations from the outside environment. To review the recent progress of material innovations targeting the spatial distribution of integrins, we first introduce the interaction mechanisms between cells and the ECM by highlighting integrin-based cell adhesions, describing how integrins respond to environmental stimuli, including variations in ligand presentation, mechanical cues, and topographical variations. Then, we overview the current development of soft materials in guiding cell behaviors and functions via spatial regulation of integrins. Finally, we discuss the current limitations of these technologies and the advances that may be achieved in the future. Undoubtedly, synthetic soft materials that mediate the spatial distribution of integrins play an important role in biomaterial innovations for advancing biomedical applications and addressing fundamental biological questions.

Evaluation of a Three-Dimensional Primary Human Hepatocyte Spheroid Model: Adoption and Industrialization for the Enhanced Detection of Drug-Induced Liver Injury

Drug-induced liver injury is a leading cause of compound attrition during both preclinical and clinical drug development, and early strategies are in place to tackle this recurring problem. Human-relevant in vitro models that are more predictive of hepatotoxicity hazard identification, and that could be employed earlier in the drug discovery process, would improve the quality of drug candidate selection and help reduce attrition. We present an evaluation of four human hepatocyte in vitro models of increasing culture complexity (i.e., two-dimensional (2D) HepG2 monolayers, hepatocyte sandwich cultures, three-dimensional (3D) hepatocyte spheroids, and precision-cut liver slices), using the same tool compounds, viability end points, and culture time points. Having established the improved prediction potential of the 3D hepatocyte spheroid model, we describe implementing this model into an industrial screening setting, where the challenge was matching the complexity of the culture system with the scale and throughput required. Following further qualification and miniaturization into a 384-well, high-throughput screening format, data was generated on 199 compounds. This clearly demonstrated the ability to capture a greater number of severe hepatotoxins versus the current routine 2D HepG2 monolayer assay while continuing to flag no false-positive compounds. The industrialization and miniaturization of the 3D hepatocyte spheroid complex in vitro model demonstrates a significant step toward reducing drug attrition and improving the quality and safety of drugs, while retaining the flexibility for future improvements, and has replaced the routine use of the 2D HepG2 monolayer assay at GlaxoSmithKline.

Detection and classification of neurons and glial cells in the MADM mouse brain using RetinaNet

The ability to automatically detect and classify populations of cells in tissue sections is paramount in a wide variety of applications ranging from developmental biology to pathology. Although deep learning algorithms are widely applied to microscopy data, they typically focus on segmentation which requires extensive training and labor-intensive annotation. Here, we utilized object detection networks (neural networks) to detect and classify targets in complex microscopy images, while simplifying data annotation. To this end, we used a RetinaNet model to classify genetically labeled neurons and glia in the brains of Mosaic Analysis with Double Markers (MADM) mice. Our initial RetinaNet-based model achieved an average precision of 0.90 across six classes of cells differentiated by MADM reporter expression and their phenotype (neuron or glia). However, we found that a single RetinaNet model often failed when encountering dense and saturated glial clusters, which show high variability in their shape and fluorophore densities compared to neurons. To overcome this, we introduced a second RetinaNet model dedicated to the detection of glia clusters. Merging the predictions of the two computational models significantly improved the automated cell counting of glial clusters. The proposed cell detection workflow will be instrumental in quantitative analysis of the spatial organization of cellular populations, which is applicable not only to preparations in neuroscience studies, but also to any tissue preparation containing labeled populations of cells.

Polarized, Amelogenin Expressing Ameloblast-Like Cells from Cervical Loop/Dental Pulp Cocultures in Bioreactors

The growth of long and polarized ameloblast-like cells has long been heralded as a major prerequisite for enamel tissue engineering. In this study, we have designed three-dimensional bioreactor/scaffold microenvironments to propagate and assess the ability of cervical loop derivatives to become long and polarized ameloblast-like cells. Our studies demonstrated that cervical loop/periodontal progenitor coculture in a growth-factor-enriched medium resulted in the formation of ameloblast-like cells expressing high levels of amelogenin and ameloblastin. Coculture of cervical loop cells with dental pulp cells on tailored collagen scaffolds enriched with leucine-rich amelogenin peptide (LRAP) and early enamel matrix resulted in singular, elongated, and polarized ameloblast-like cells that expressed and secreted ameloblastin and amelogenin enamel proteins. Bioreactor microenvironments enriched with enamel matrix and LRAP also proved advantageous for the propagation of HAT-7 cells, resulting in a ∼20-fold higher expression of amelogenin and ameloblastin enamel proteins compared with controls growing on plain scaffolds. Together, studies presented here highlight the benefits of microgravity culture systems combined with ameloblast-specific microenvironments and tailored scaffolds for the growth of ameloblast-like cells.

Distinct roles of nonmuscle myosin II isoforms for establishing tension and elasticity during cell morphodynamics

Nonmuscle myosin II (NM II) is an integral part of essential cellular processes, including adhesion and migration. Mammalian cells express up to three isoforms termed NM IIA, B, and C. We used U2OS cells to create CRISPR/Cas9-based knockouts of all three isoforms and analyzed the phenotypes on homogenously coated surfaces, in collagen gels, and on micropatterned substrates. In contrast to homogenously coated surfaces, a structured environment supports a cellular phenotype with invaginated actin arcs even in the absence of NM IIA-induced contractility. A quantitative shape analysis of cells on micropatterns combined with a scale-bridging mathematical model reveals that NM IIA is essential to build up cellular tension during initial stages of force generation, while NM IIB is necessary to elastically stabilize NM IIA-generated tension. A dynamic cell stretch/release experiment in a three-dimensional scaffold confirms these conclusions and in addition reveals a novel role for NM IIC, namely the ability to establish tensional homeostasis.

Quantitative developmental biology in vitro using micropatterning

Micropatterning encompasses a set of methods aimed at precisely controlling the spatial distribution of molecules onto the surface of materials. Biologists have borrowed the idea and adapted these methods, originally developed for electronics, to impose physical constraints on biological systems with the aim of addressing fundamental questions across biological scales from molecules to multicellular systems. Here, I approach this topic from a developmental biologist's perspective focusing specifically on how and why micropatterning has gained in popularity within the developmental biology community in recent years. Overall, this Primer provides a concise overview of how micropatterns are used to study developmental processes and emphasises how micropatterns are a useful addition to the developmental biologist's toolbox.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

Tuneable Hybrid Hydrogels via Complementary Self-Assembly of a Bioactive Peptide with a Robust Polysaccharide

Synthetic materials designed for improved biomimicry of the extracellular matrix must contain fibrous, bioactive, and mechanical cues. Self-assembly of low molecular weight gelator (LMWG) peptides Fmoc-DIKVAV (Fmoc-aspartic acid-isoleucine-lysine-valine-alanine-valine) and Fmoc-FRGDF (Fmoc-phenylalanine-arginine-glycine-aspartic acid-phenylalanine) creates fibrous and bioactive hydrogels. Polysaccharides such as agarose are biocompatible, degradable, and non-toxic. Agarose and these Fmoc-peptides have both demonstrated efficacy in vitro and in vivo. These materials have complementary properties; agarose has known mechanics in the physiological range but is inert and would benefit from bioactive and topographical cues found in the fibrous, protein-rich extracellular matrix. Fmoc-DIKVAV and Fmoc-FRGDF are synthetic self-assembling peptides that present bioactive cues "IKVAV" and "RGD" designed from the ECM proteins laminin and fibronectin. The work presented here demonstrates that the addition of agarose to Fmoc-DIKVAV and Fmoc-FRGDF results in physical characteristics that are dependent on agarose concentration. The networks are peptide-dominated at low agarose concentrations, and agarose-dominated at high agarose concentrations, resulting in distinct changes in structural morphology. Interestingly, at mid-range agarose concentration, a hybrid network is formed with structural similarities to both peptide and agarose systems, demonstrating reinforced mechanical properties. Bioactive-LMWG polysaccharide hydrogels demonstrate controllable microenvironmental properties, providing the ability for tissue-specific biomaterial design for tissue engineering and 3D cell culture.

Protein Micropatterning in 2.5D: An Approach to Investigate Cellular Responses in Multi-Cue Environments

The extracellular microenvironment is an important regulator of cell functions. Numerous structural cues present in the cellular microenvironment, such as ligand distribution and substrate topography, have been shown to influence cell behavior. However, the roles of these cues are often studied individually using simplified, single-cue platforms that lack the complexity of the three-dimensional, multi-cue environment cells encounter in vivo. Developing ways to bridge this gap, while still allowing mechanistic investigation into the cellular response, represents a critical step to advance the field. Here, we present a new approach to address this need by combining optics-based protein patterning and lithography-based substrate microfabrication, which enables high-throughput investigation of complex cellular environments. Using a contactless and maskless UV-projection system, we created patterns of extracellular proteins (resembling contact-guidance cues) on a two-and-a-half-dimensional (2.5D) cell culture chip containing a library of well-defined microstructures (resembling topographical cues). As a first step, we optimized experimental parameters of the patterning protocol for the patterning of protein matrixes on planar and non-planar (2.5D cell culture chip) substrates and tested the technique with adherent cells (human bone marrow stromal cells). Next, we fine-tuned protein incubation conditions for two different vascular-derived human cell types (myofibroblasts and umbilical vein endothelial cells) and quantified the orientation response of these cells on the 2.5D, physiologically relevant multi-cue environments. On concave, patterned structures (curvatures between κ = 1/2500 and κ = 1/125 μm^-1), both cell types predominantly oriented in the direction of the contact-guidance pattern. In contrast, for human myofibroblasts on micropatterned convex substrates with higher curvatures (κ ≥ 1/1000 μm^-1), the majority of cells aligned along the longitudinal direction of the 2.5D features, indicating that these cells followed the structural cues from the substrate curvature instead. These findings exemplify the potential of this approach for systematic investigation of cellular responses to multiple microenvironmental cues.

Cell biology: Centrosomes in inner space

Centrosome positioning is essential for many processes in animal cells, in particular during development and migration. A new study using quantitative analysis of enucleated cells plated on adhesive micropatterns reveals that microtubules position the centrosome in the geometric center of the intracellular space defined by the actin cytoskeleton.

Expression of SSEA-4 and Oct-4 from somatic cells in primary mouse gastric cell culture induced by brief strong acid

Environmental changes can stress and alter biology at the molecular and cellular level. For example, metal-protein interaction is a classic physic and biological property of nature, which is fundamentally influenced by acidity. Here, we report a unique cellular reprogramming phenomenon in that a brief strong acid treatment induced the expression of pluripotent stem cell (PSC) markers. We used strong acid to briefly challenge mix-cultured gastric cells, and then subcultured survived cells in a normal cell culture medium. We found that survival acid-treated cells expressed PSC markers detected by commonly used pluripotent antibodies such as SSEA-4 and Oct4. In addition, we observed that the survived cells from the acid challenge grew faster during the second and third weeks of subculture and had a relative short doubling time (DT) than the controls. PSC marker-labeled 'older' cells also presented immature cell-like morphology with some having marker Oct4 in the nucleus. Finally, the expression of the markers appeared to be sensitive to metal ion chelation. Removal of the metals during a brief acid treatment reduced pluripotent marker-positive cells, suggesting the dissociation of metals from metal-binding proteins may be a factor involved in the induction of stem cell markers. Our findings reveal that somatic cells appear to possess a plasticity feature to express pluripotent marker proteins or to select cell subpopulations that express pluripotent marker proteins when cells are transiently exposed to strong acid. It opens new directions for understanding conserved regulatory mechanisms involved in cellular survival under stressful stimulation.

Targeting Lysyl Oxidase Family Meditated Matrix Cross-Linking as an Anti-Stromal Therapy in Solid Tumours

Simple Summary

To improve efficacy of solid cancer treatment, efforts have shifted towards targeting both the cancer cells and the surrounding tumour tissue they grow in. The lysyl oxidase (LOX) family of enzymes underpin the fibrotic remodeling of the tumour microenvironment to promote both cancer growth, spread throughout the body and modulate response to therapies. This review examines how the lysyl oxidase family is involved in tumour development, how they can be targeted, and their potential as diagnostic and prognostic biomarkers in solid tumours.

Abstract

The lysyl oxidase (LOX) family of enzymes are a major driver in the biogenesis of desmoplastic matrix at the primary tumour and secondary metastatic sites. With the increasing interest in and development of anti-stromal therapies aimed at improving clinical outcomes of cancer patients, the Lox family has emerged as a potentially powerful clinical target. This review examines how lysyl oxidase family dysregulation in solid cancers contributes to disease progression and poor patient outcomes, as well as an evaluation of the preclinical landscape of LOX family targeting therapeutics. We also discuss the suitability of the LOX family as a diagnostic and/or prognostic marker in solid tumours.

Imaging non-classical mechanical responses of lipid membranes using molecular rotors

Lipid packing in cellular membranes has a direct effect on membrane tension and microviscosity, and plays a central role in cellular adaptation, homeostasis and disease. According to conventional mechanical descriptions, viscosity and tension are directly interconnected, with increased tension leading to decreased membrane microviscosity. However, the intricate molecular interactions that combine to build the structure and function of a cell membrane suggest a more complex relationship between these parameters. In this work, a viscosity-sensitive fluorophore (‘molecular rotor’) is used to map changes in microviscosity in model membranes under conditions of osmotic stress. Our results suggest that the relationship between membrane tension and microviscosity is strongly influenced by the bilayer's lipid composition. In particular, we show that the effects of increasing tension are minimised for membranes that exhibit liquid disordered (L_d) – liquid ordered (L_o) phase coexistence; while, surprisingly, membranes in pure gel and L_o phases exhibit a negative compressibility behaviour, i.e. they soften upon compression.

Viscosity-sensitive molecular rotors demonstrate that the non-classical mechanical behaviour of model lipid membranes is able to buffer external stress.

Evaluation of Preosteoblast MC3T3-E1 Cells Cultured on a Microporous Titanium Membrane Fabricated Using a Precise Mechanical Punching Process

The surface topography of Titanium (Ti) combined toughness and biocompatibility affects the attachment and migration of cells. Limited information of morphological characteristics, formed by precise machining in micron order, is currently available on the Ti that could promote osteoconduction. In the present study, a pure Ti membrane was pierced with precise 25 μm square holes at 75 μm intervals and appear burrs at the edge of aperture. We defined the surface without burrs as the “Head side” and that with burrs as the “Tail side”. The effects of the machining microtopography on the proliferation and differentiation of the preosteoblasts (MC3T3-E1 cells) were investigated. The cells were more likely to migrate to, and accumulate in, the aperture of holes on the head side, but grew uniformly regardless of holes on the tail side. The topography on the both surfaces increased osteopontin gene expression levels. Osteocalcin expression levels were higher on the head side than one on the blank scaffold and tail side (p < 0.05). The osteocalcin protein expression levels were higher on the tail side than on the head side after 21 days of cultivation, and were comparable to the proportion of the calcified area (p < 0.05). These results demonstrate the capacity of a novel microporous Ti membrane fabricated using a precise mechanical punching process to promote cell proliferation and activity.

Inhibition of hypertrophy and improving chondrocyte differentiation by MMP-13 inhibitor small molecule encapsulated in alginate-chondroitin sulfate-platelet lysate hydrogel

BACKGROUND

Mesenchymal stem cells are a promising cell source for chondrogenic differentiation and have been widely used in several preclinical and clinical studies. However, they are prone to an unwanted differentiation process towards hypertrophy that limits their therapeutic efficacy. Matrix metallopeptidase 13 (MMP-13) is a well-known factor regulated during this undesirable event. MMP-13 is a collagen degrading enzyme, which is also highly expressed in the hypertrophic zone of the growth plate and in OA cartilage. Accordingly, we investigated the effect of MMP-13 inhibition on MSC hypertrophy.

METHODS

In this study, 5-bromoindole-2-carboxylic acid (BICA) was used as an inhibitory agent for MMP-13 expression. After identifying its optimal concentration, BICA was mixed into a hydrogel and the release rate was studied. To prepare the ideal hydrogel, chondroitin sulfate (CS) and platelet lysate (PL) were mixed with sodium alginate (Alg) at concentrations selected based on synergistic mechanical and rheometric properties. Then, four hydrogels were prepared by combining alginate (1.5%w/v) and/or CS (1%w/v) and/or PL (20%v/v). The chondrogenic potential and progression to hypertrophy of human bone marrow-derived mesenchymal stem cell (hBM-MSC)-loaded hydrogels were investigated under free swelling and mechanical loading conditions, in the presence and absence of BICA.

RESULTS

Viability of hBM-MSCs seeded in the four hydrogels was similar. qRT-PCR revealed that BICA could successfully inhibit MMP-13 expression, which led to an inhibition of Coll X and induction of Coll-II, in both free swelling and loading conditions. The GAG deposition was higher in the group combining BICA and mechanical stimulation.

CONCLUSIONS

It is concluded that BICA inhibition of MMP-13 reduces MSC hypertrophy during chondrogenesis.

Reversible elastic phase field approach and application to cell monolayers

Motion and generation of forces by single cells and cell collectives are essential elements of many biological processes, including development, wound healing and cancer cell migration. Quantitative wound healing assays have demonstrated that cell monolayers can be both dynamic and elastic at the same time. However, it is very challenging to model this combination with conventional approaches. Here we introduce an elastic phase field approach that allows us to predict the dynamics of elastic sheets under the action of active stresses and localized forces, e.g. from leader cells. Our method ensures elastic reversibility after release of forces. We demonstrate its potential by studying several paradigmatic situations and geometries relevant for single cells and cell monolayers, including elastic bars, contractile discs and expanding monolayers with leader cells.

Multistimuli Sensing Adhesion Unit for the Self-Positioning of Minimal Synthetic Cells

Cells have the ability to sense different environmental signals and position themselves accordingly in order to support their survival. Introducing analogous capabilities to the bottom-up assembled minimal synthetic cells is an important step for their autonomy. Here, a minimal synthetic cell which combines a multistimuli sensitive adhesion unit with an energy conversion module is reported, such that it can adhere to places that have the right environmental parameters for ATP production. The multistimuli sensitive adhesion unit senses light, pH, oxidative stress, and the presence of metal ions and can regulate the adhesion of synthetic cells to substrates in response to these stimuli following a chemically coded logic. The adhesion unit is composed of the light and redox responsive protein interaction of iLID and Nano and the pH sensitive and metal ion mediated binding of protein His-tags to Ni²⁺ -NTA complexes. Integration of the adhesion unit with a light to ATP conversion module into one synthetic cell allows it to adhere to places under blue light illumination, non-oxidative conditions, at neutral pH and in the presence of metal ions, which are the right conditions to synthesize ATP. Thus, the multistimuli responsive adhesion unit allows synthetic cells to self-position and execute their functions.

Novel Tunable Spatio-Temporal Patterns From a Simple Genetic Oscillator Circuit

Multicellularity, the coordinated collective behavior of cell populations, gives rise to the emergence of self-organized phenomena at many different spatio-temporal scales. At the genetic scale, oscillators are ubiquitous in regulation of multicellular systems, including during their development and regeneration. Synthetic biologists have successfully created simple synthetic genetic circuits that produce oscillations in single cells. Studying and engineering synthetic oscillators in a multicellular chassis can therefore give us valuable insights into how simple genetic circuits can encode complex multicellular behaviors at different scales. Here we develop a study of the coupling between the repressilator synthetic genetic ring oscillator and constraints on cell growth in colonies. We show in silico how mechanical constraints generate characteristic patterns of growth rate inhomogeneity in growing cell colonies. Next, we develop a simple one-dimensional model which predicts that coupling the repressilator to this pattern of growth rate via protein dilution generates traveling waves of gene expression. We show that the dynamics of these spatio-temporal patterns are determined by two parameters; the protein degradation and maximum expression rates of the repressors. We derive simple relations between these parameters and the key characteristics of the traveling wave patterns: firstly, wave speed is determined by protein degradation and secondly, wavelength is determined by maximum gene expression rate. Our analytical predictions and numerical results were in close quantitative agreement with detailed individual based simulations of growing cell colonies. Confirming published experimental results we also found that static ring patterns occur when protein stability is high. Our results show that this pattern can be induced simply by growth rate dilution and does not require transition to stationary phase as previously suggested. Our method generalizes easily to other genetic circuit architectures thus providing a framework for multi-scale rational design of spatio-temporal patterns from genetic circuits. We use this method to generate testable predictions for the synthetic biology design-build-test-learn cycle.

Transitioning from development to commercial: risk-based guidance for critical materials management in cell therapies

A key hurdle to ensuring patient access to cell and gene therapies (CGTs) and continued growth of the industry is the management of raw materials. The combination of rapid growth, individual product and process complexity and limited industry-specific guidance or awareness presents non-obvious risk mitigation challenges for transitioning from development to clinical application. Understanding, assessing and mitigating the varied raw material risks for CGT products during product and clinical development are critical for ensuring smooth transitions into commercialization and for preventing interruption of product supply to patients. This article presents a risk-based approach driven by concerns for patient safety that can help focus and coordinate efforts to address the most critical risk factors. Highlighted are some of the highest risk materials common to the manufacture of many CGTs, including the primary starting material, culture media, reagents and single-use components. Using a hypothetical gene-edited cell therapy as an example, we describe the general manufacturing process and subsequently incorporate the described methodology to perform a sample risk assessment. The practical approach described herein is intended to assist CGT manufacturers and suppliers in actively assessing materials early in development to provide a basic starting point for mitigating risks experienced when translating CGT products for clinical and long-term commercial application.

Extracellular Matrix Geometry and Initial Adhesive Position Determine Stress Fiber Network Organization during Cell Spreading

Three-dimensional matrices often contain highly structured adhesive tracks that require cells to turn corners and bridge non-adhesive areas. Here, we investigate these complex processes using micropatterned cell adhesive frames. Spreading kinetics on these matrices depend strongly on initial adhesive position and are predicted by a cellular Potts model (CPM), which reflects a balance between adhesion and intracellular tension. As cells spread, new stress fibers (SFs) assemble periodically and parallel to the leading edge, with spatial intervals of ∼2.5 μm, temporal intervals of ∼15 min, and characteristic lifetimes of ∼50 min. By incorporating these rules into the CPM, we can successfully predict SF network architecture. Moreover, we observe broadly similar behavior when we culture cells on arrays of discrete collagen fibers. Our findings show that ECM geometry and initial cell position strongly determine cell spreading and that cells encode a memory of their spreading history through SF network organization.

The Biophysics of Cell Migration: Biasing Cell Motion with Feynman Ratchets

The concepts and frameworks of soft matter physics and the laws of thermodynamics can be used to describe relevant developmental, physiologic, and pathologic events in which directed cell migration is involved, such as in cancer. Typically, this directionality has been associated with the presence of soluble long-range gradients of a chemoattractant, synergizing with many other guidance cues to direct the motion of cells. In particular, physical inputs have been shown to strongly influence cell locomotion. However, this type of cue has been less explored despite the importance in biology. In this paper, we describe recent in vitro works at the interface between physics and biology, showing how the motion of cells can be directed by using gradient-free environments with repeated local asymmetries. This rectification of cell migration, from random to directed, is a process reminiscent of the Feynman ratchet; therefore, this framework can be used to explain the mechanism behind directed cell motion.

Intra-volume processing of gelatine hydrogel by femtosecond laser-induced cavitation

Cell oxygenation and nutrition are crucial for the viability of tissue-engineered constructs, and different alternatives are currently being developed to achieve an adequate vascularisation of the engineered tissue. One of the alternatives is the generation of channel-like patterns in a bioconstruct. Here, the formation of full-formed channels inside hydrogels by laser-induced cavitation was investigated. A near-infrared, femtosecond laser beam focused with a high numerical aperture was employed to obtain intra-volume modifications of a block of gelatine hydrogel. Characterisation of the laser-processed gelatine was carried out by optical microscopy and epifluorescence microscopy right after and 24 h after the laser process. Rheology analyses on the unprocessed gelatine blocks were conducted to better understand the cavitation mechanism taking place during the intense laser interaction. Different cavitation patterns were observed at varying dose values by changing the repetition rate and the overlap between successive pulses while keeping the laser fluence and the number of passes fixed. This way, cavitation bubble features and behaviour can be controlled to optimise the formation of intra-volume channels in the gelatine volume. Results showed that the generation of fully formed channels was linked to the formation of large non-spherical cavitation bubbles during the laser interaction at high dose and low repetition rates. In conclusion, the formation of fully formed channels was made possible with a near-infrared, femtosecond laser beam strongly focused inside gelatine hydrogel blocks through laser-induced cavitation at high dose and low repetition rates.

Polystyrene Topography Sticker Array for Cell-Based Assays

Cells can respond to different topographical cues in their natural microenvironment. Hence, scientists have employed microfabrication techniques and materials to generate culture substrates containing topographies for cell-based assays. However, one of the limitations of custom topographical platforms is the lack of adoption by the broad research community. These techniques and materials have high costs, require high technical expertise, and can leach components that may introduce artifacts. In this study, we developed an array of culture surfaces on polystyrene using razor printing and sanding methods to examine the impact of microscale topographies on cell behavior. The proposed technology consists of culture substrates of defined roughness, depth, and curvature on polystyrene films bound to the bottom of a culture well using double-sided medical-grade tape. Human monocytes and adult mesenchymal stem cells (hMSCs) were used as test beds to demonstrate the applicability of the array for cell-based assays. An increase in cell elongation and Arg-1 expression was detected in macrophages cultured in grooves and on rough substrates as compared to flat surfaces. Also, substrates with enhanced roughness stimulated the proliferation of hMSCs. This effect correlated with the secretion of proteins involved in cell proliferation and the downregulation of those associated with cell differentiation. Our results showed that the polystyrene topography sticker array supports cellular changes guided by microscale surface roughness and geometries. Consequently, microscale surface topographies on polished and razor-printed polystyrene films could leverage the endogenous mechanisms of cells to stimulate cellular changes at the functional level for cell-based assays.

The stressful tumour environment drives plasticity of cell migration programmes, contributing to metastasis

Tumours evolve to cope with environmental stresses or challenges such as nutrient starvation, depletion of survival factors, and unbalanced mechanical forces. The uncontrolled growth and aberrant deregulation of core cell homeostatic pathways induced by genetic mutations create an environment of stress. Here, we explore how the adaptations of tumours to the changing environment can drive changes in the motility machinery of cells, affecting migration, invasion, and metastasis. Tumour cells can invade individually or collectively, or they can be extruded out of the surrounding epithelium. These mechanisms are thought to be modifications of normal processes occurring during development or tissue repair. Therefore, tumours may activate these pathways in response to environmental stresses, enabling them to survive in hostile environments and spread to distant sites. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Cellular Geometry Sensing at Different Length Scales and its Implications for Scaffold Design

Geometrical cues provided by the intrinsic architecture of tissues and implanted biomaterials have a high relevance in controlling cellular behavior. Knowledge of how cells sense and subsequently respond to complex geometrical cues of various sizes and origins is needed to understand the role of the architecture of the extracellular environment as a cell-instructive parameter. This is of particular interest in the field of tissue engineering, where the success of scaffold-guided tissue regeneration largely depends on the formation of new tissue in a native-like organization in order to ensure proper tissue function. A well-considered internal scaffold design (i.e., the inner architecture of the porous structure) can largely contribute to the desired cell and tissue organization. Advances in scaffold production techniques for tissue engineering purposes in the last years have provided the possibility to accurately create scaffolds with defined macroscale external and microscale internal architectures. Using the knowledge of how cells sense geometrical cues of different size ranges can drive the rational design of scaffolds that control cellular and tissue architecture. This concise review addresses the recently gained knowledge of the sensory mechanisms of cells towards geometrical cues of different sizes (from the nanometer to millimeter scale) and points out how this insight can contribute to informed architectural scaffold designs.

Cell alignment by smectic liquid crystal elastomer coatings with nanogrooves

Control of cells behavior through topography of substrates is an important theme in biomedical applications. Among many materials used as substrates, polymers show advantages since they can be tailored by chemical functionalization. Fabrication of polymer substrates with nano- and microscale topography requires processing by lithography, microprinting, etching, and so forth. In this work, we introduce a different approach based on anisotropic elastic properties of polymerized smectic A (SmA) liquid crystal elastomer (LCE). When the SmA liquid crystal coating is deposited onto a substrate with planar alignment of the molecules, it develops nanogrooves at its free surface. After photopolymerization, these nanogrooves show an excellent ability to align human dermal fibroblasts over large areas. The alignment quality is good for both bare SmA LCE substrates and for substrates coated with fibronectin. The SmA LCE nano-topographies show a high potential for tissue engineering.

Bi-Layered Polymer Carriers with Surface Modification by Electrospinning for Potential Wound Care Applications

Polymeric wound dressings with advanced properties are highly preferred formulations to promote the tissue healing process in wound care. In this study, a combinational technique was investigated for the fabrication of bi-layered carriers from a blend of polyvinyl alcohol (PVA) and sodium alginate (SA). The bi-layered carriers were prepared by solvent casting in combination with two surface modification approaches: electrospinning or three-dimensional (3D) printing. The bi-layered carriers were characterized and evaluated in terms of physical, physicochemical, adhesive properties and for the safety and biological cell behavior. In addition, an initial inkjet printing trial for the incorporation of bioactive substances for drug delivery purposes was performed. The solvent cast (SC) film served as a robust base layer. The bi-layered carriers with electrospun nanofibers (NFs) as the surface layer showed improved physical durability and decreased adhesiveness compared to the SC film and bi-layered carriers with patterned 3D printed layer. Thus, these bi-layered carriers presented favorable properties for dermal use with minimal tissue damage. In addition, electrospun NFs on SC films (bi-layered SC/NF carrier) provided the best physical structure for the cell adhesion and proliferation as the highest cell viability was measured compared to the SC film and the carrier with patterned 3D printed layer (bi-layered SC/3D carrier). The surface properties of the bi-layered carriers with electrospun NFs showed great potential to be utilized in advanced technical approach with inkjet printing for the fabrication of bioactive wound dressings.

Fiber stiffness, pore size and adhesion control migratory phenotype of MDA-MB-231 cells in collagen gels

Cancer cell migration is influenced by cellular phenotype and behavior as well as by the mechanical and chemical properties of the environment. Furthermore, many cancer cells show plasticity of their phenotype and adapt it to the properties of the environment. Here, we study the influence of fiber stiffness, confinement, and adhesion properties on cancer cell migration in porous collagen gels. Collagen gels with soft fibers abrogate migration and promote a round, non-invasive phenotype. Stiffer collagen fibers are inherently more adhesive and lead to the existence of an adhesive phenotype and in general confined migration due to adhesion. Addition of TGF-β lowers adhesion, eliminates the adhesive phenotype and increases the amount of highly motile amoeboid phenotypes. Highest migration speeds and longest displacements are achieved in stiff collagen fibers in pores of about cell size by amoeboid phenotypes. This elucidates the influence of the mechanical properties of collagen gels on phenotype and subsequently migration and shows that stiff fibers, cell sized pores, and low adhesion, are optimal conditions for an amoeboid phenotype and efficient migration.

The Protein Mat(ters)-Revealing the Biologically Relevant Mechanical Contribution of Collagen- and Fibronectin-Coated Micropatterns

Understanding cell-material interactions requires accurate characterization of the substrate mechanics, which are generally measured by indentation-type atomic force microscopy. To facilitate cell-substrate interaction, model extracellular matrix coatings are used although their tensile mechanical properties are generally unknown. In this study, beyond standard compressive stiffness estimation, we performed a novel tensile mechanical characterization of collagen- and fibronectin-micropatterned polyacrylamide hydrogels. We further demonstrate the impact of the protein mat on the tensile stiffness characterization of adherent cells. To our knowledge, our study is the first to uncover direction-dependent mechanical behavior of the protein coatings and to demonstrate that it affects cellular response relative to substrate mechanics.

Scaffold-free bioprinted osteogenic and chondrogenic systems to model osteochondral physiology

Three-dimensional bioprinted culture platforms mimic the native microenvironment of tissues more accurately than two-dimensional cell cultures or animal models. Scaffold-free bioprinting eliminates many complications associated with traditional scaffold-dependent printing as well as provides better cell-to-cell interactions and long-term functionality. In this study, constructs were produced from bone marrow derived mesenchymal stem cells (BM-MSCs) using a scaffold-free bioprinter. These constructs were cultured in either osteogenic, chondrogenic, a 50:50 mixture of osteogenic and chondrogenic ('osteo-chondro'), or BM-MSC growth medium. Osteogenic and chondrogenic differentiation capacity was determined over an 8-week culture period using histological and immunohistochemical staining and RT-qPCR (Phase I). After 6 weeks in culture, individual osteogenic and chondrogenic differentiated constructs were adhered to create a bone-cartilage interaction model. Adhered differentiated constructs were cultured for an additional 8 weeks in either chondrogenic or osteo-chondro medium to evaluate sustainability of lineage specification and transdifferentiation potential (Phase II). Constructs cultured in their respective osteogenic and/or chondrogenic medium differentiated directly into bone (model of intramembranous ossification) or cartilage. Positive histological and immunohistochemical staining for bone or cartilage identification was shown after 4 and 8 weeks in culture. Expression of osteogenesis and chondrogenesis associated genes increased between weeks 2 and 6. Adhered individual osteogenic and chondrogenic differentiated constructs sustained their differentiated phenotype when cultured in chondrogenic medium. However, adhered individual chondrogenic differentiated constructs cultured in osteo-chondro medium were converted to bone (model of metaplastic transformation). These bioprinted models of bone-cartilage interaction, intramembranous ossification, and metaplastic transformation of cartilage into bone offer a useful and promising approach for bone and cartilage tissue engineering research. Specifically, these models can be potentially used as functional tissue systems for studying osteochondral defect repair, drug discovery and response, and many other potential applications.

Cell-Perceived Substrate Curvature Dynamically Coordinates the Direction, Speed, and Persistence of Stromal Cell Migration

Adherent cells residing within tissues or biomaterials are presented with 3D geometrical cues from their environment, often in the form of local surface curvatures. While there is growing evidence that cellular decision-making is influenced by substrate curvature, the effect of physiologically relevant, cell-scale anisotropic curvatures remains poorly understood. This study systematically explores the migration behavior of human bone marrow stromal cells (hBMSCs) on a library of anisotropic curved structures. Analysis of cell trajectories reveals that, on convex cylindrical structures, hBMSC migration speed and persistence are strongly governed by the cellular orientation on the curved structure, while migration on concave cylindrical structures is characterized by fast but non-aligned and non-persistent migration. Concurrent presentation of concave and convex substrates on toroidal structures induces migration in the direction where hBMSCs can most effectively avoid cell bending. These distinct migration behaviors are found to be universally explained by the cell-perceived substrate curvature, which on anisotropic curved structures is dependent on both the temporally varying cell orientation and the 3D cellular morphology. This work demonstrates that cell migration is dynamically guided by the perceived curvature of the underlying substrate, providing an important biomaterial design parameter for instructing cell migration in tissue engineering and regenerative medicine.

Nanotopographical regulation of pancreatic islet-like cluster formation from human pluripotent stem cells using a gradient-pattern chip

Bioengineering approaches to regulate stem cell fates aim to recapitulate the in vivo microenvironment. In recent years, manipulating the micro- and nano-scale topography of the stem cell niche has gained considerable interest for the purposes of controlling extrinsic mechanical cues to regulate stem cell fate and behavior in vitro. Here, we established an optimal nanotopographical system to improve 3-dimensional (3D) differentiation of pancreatic cells from human pluripotent stem cells (hPSCs) by testing gradient-pattern chips of nano-scale polystyrene surface structures with varying sizes and shapes. The optimal conditions for 3D differentiation of pancreatic cells were identified by assessing the expression of developmental regulators that are required for pancreatic islet development and maturation. Our results showed that the gradient chip of pore-part 2 (Po-2, 200-300 nm diameter) pattern was the most efficient setting to generate clusters of pancreatic endocrine progenitors (PDX1+ and NGN3+) compared to those of other pore diameters (Po-1, 100-200 or Po-3, 300-400 nm) tested across a range of pillar patterns and flat surfaces. Furthermore, the Po-2 gradient pattern-derived clusters generated islet-like 3D spheroids and tested positive for the zinc-chelating dye dithizone. The spheroids consisted of more than 30% CD200 + endocrine cells and also expressed NKX6.1 and NKX2.2. In addition, pancreatic β- cells expressing insulin and polyhormonal cells expressing both insulin and glucagon were obtained at the final stage of pancreatic differentiation. In conclusion, our data suggest that an optimal topographical structure for differentiation to specific cell types from hPSCs can be tested efficiently by using gradient-pattern chips designed with varying sizes and surfaces. STATEMENT OF SIGNIFICANCE: Our study provides demonstrates of using gradient nanopatterned chips for differentiation of pancreatic islet-like clusters. Gradient nanopatterned chips are consisted of two different shapes (nanopillar and nanopore) in three different ranges of nano sizes (100-200, 200-300, 300-400 nm). We found that optimal nanostructures for differentiation of pancreatic islet-like clusters were 200-300 nm nano pores. Cell transplantation is one of the major therapeutic option for type 1 diabetes mellitus (DM) using stem cell-derived β-like cells. We generated 50 um pancreatic islet-like clusters in size, which would be an optimal size for cell transplantation. Futuremore, the small clusters provide a powerful source for cell therapy. Our findings suggest gradient nanopatterned chip provides a powerful tool to generate specific functional cell types of a high purity for potential uses in cell therapy development.

Large-Area Biomolecule Nanopatterns on Diblock Copolymer Surfaces for Cell Adhesion Studies

Cell membrane receptors bind to extracellular ligands, triggering intracellular signal transduction pathways that result in specific cell function. Some receptors require to be associated forming clusters for effective signaling. Increasing evidences suggest that receptor clustering is subjected to spatially controlled ligand distribution at the nanoscale. Herein we present a method to produce in an easy, straightforward process, nanopatterns of biomolecular ligands to study ligand⁻receptor processes involving multivalent interactions. We based our platform in self-assembled diblock copolymers composed of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) that form PMMA nanodomains in a closed-packed hexagonal arrangement. Upon PMMA selective functionalization, biomolecular nanopatterns over large areas are produced. Nanopattern size and spacing can be controlled by the composition of the block-copolymer selected. Nanopatterns of cell adhesive peptides of different size and spacing were produced, and their impact in integrin receptor clustering and the formation of cell focal adhesions was studied. Cells on ligand nanopatterns showed an increased number of focal contacts, which were, in turn, more matured than those found in cells cultured on randomly presenting ligands. These findings suggest that our methodology is a suitable, versatile tool to study and control receptor clustering signaling and downstream cell behavior through a surface-based ligand patterning technique.

Nanotopography-based engineering of retroviral DNA integration patterns

Controlling the interactions between cells and viruses is critical for treating infected patients, preventing viral infections, and improving virus-based therapeutics. Chemical methods using small molecules and biological methods using proteins and nucleic acids are employed for achieving this control, albeit with limitations. We found, for the first time, that retroviral DNA integration patterns in the human genome, the result of complicated interactions between cells and viruses, can be engineered by adapting cells to the defined nanotopography of silica bead monolayers. Compared with cells on a flat glass surface, cells on beads with the highest curvature harbored retroviral DNAs at genomic sites near transcriptional start sites and CpG islands during infections at more than 50% higher frequencies. Furthermore, cells on the same type of bead layers contained retroviral DNAs in the genomic regions near cis-regulatory elements at frequencies that were 2.6-fold higher than that of cells on flat glass surfaces. Systems-level genetic network analysis showed that for cells on nanobeads with the highest curvature, the genes that would be affected by cis-regulatory elements near the retroviral integration sites perform biological functions related to chromatin structure and antiviral activities. Our unexpected observations suggest that novel engineering approaches based on materials with specific nanotopography can improve control over viral events.

Randomly Distributed K14+ Breast Tumor Cells Polarize to the Leading Edge and Guide Collective Migration in Response to Chemical and Mechanical Environmental Cues

Collective cell migration is an adaptive, coordinated interactive process involving cell-cell and cell-extracellular matrix (ECM) microenvironmental interactions. A critical aspect of collective migration is the sensing and establishment of directional movement. It has been proposed that a subgroup of cells known as leader cells localize at the front edge of a collectively migrating cluster and are responsible for directing migration. However, it is unknown how and when leader cells arrive at the front edge and what environmental cues dictate leader cell development and behavior. Here, we addressed these questions by combining a microfluidic device design that mimics multiple tumor microenvironmental cues concurrently with biologically relevant primary, heterogeneous tumor cell organoids. Prior to migration, breast tumor leader cells (K14⁺) were present throughout a tumor organoid and migrated (polarized) to the leading edge in response to biochemical and biomechanical cues. Impairment of either CXCR4 (biochemical responsive) or the collagen receptor DDR2 (biomechanical responsive) abrogated polarization of leader cells and directed collective migration. This work demonstrates that K14⁺ leader cells utilize both chemical and mechanical cues from the microenvironment to polarize to the leading edge of collectively migrating tumors. SIGNIFICANCE: These findings demonstrate that pre-existing, randomly distributed leader cells within primary tumor organoids use CXCR4 and DDR2 to polarize to the leading edge and direct migration.

Adhesion to nanofibers drives cell membrane remodeling through one-dimensional wetting

The shape of cellular membranes is highly regulated by a set of conserved mechanisms that can be manipulated by bacterial pathogens to infect cells. Remodeling of the plasma membrane of endothelial cells by the bacterium Neisseria meningitidis is thought to be essential during the blood phase of meningococcal infection, but the underlying mechanisms are unclear. Here we show that plasma membrane remodeling occurs independently of F-actin, along meningococcal type IV pili fibers, by a physical mechanism that we term 'one-dimensional' membrane wetting. We provide a theoretical model that describes the physical basis of one-dimensional wetting and show that this mechanism occurs in model membranes interacting with nanofibers, and in human cells interacting with extracellular matrix meshworks. We propose one-dimensional wetting as a new general principle driving the interaction of cells with their environment at the nanoscale that is diverted by meningococci during infection.

Identification of a Novel Small RNA srvg23535 in Vibrio alginolyticus ZJ-T and Its Characterization With Phenotype MicroArray Technology

Small non-coding RNAs (sRNAs) are important modulators of gene expression and are involved in the pathogenesis and survival of prokaryotes. However, few studies have been conducted with Vibrio alginolyticus, which limits our ability to probe the regulation of virulence and environmental adaptation by sRNAs in this opportunistic pathogen. In this study, the sRNA candidate srvg23535 was identified in V. alginolyticus ZJ-T. The precise transcript end, secondary structure, and sequence conservation were determined. A srvg23535 null mutant was constructed and characterized by using Phenotype MicroArray (PM) technology. In silico target prediction was conducted by IntaRNA and TargetRNA2. Subsequently, a 107 nt transcript was validated with a sigma70 promoter at the 5' end and a Rho-independent terminator at the 3' end. The sRNA srvg23535 had four stem-loop structures and was conserved among Vibrio harveyi, Vibrio parahaemolyticus, and Vibrio splendidus. Deletion of srvg23535 in V. alginolyticus ZJ-T led to a weaker utilization of D-mannose, D-melibiose, lactulose, and inosine as carbon sources but stronger utilization of L-cysteine as nitrogen source. Moreover, the srvg2353 mutant showed stronger resistance to osmotic stress but weaker resistance to pH stress. Additionally, a total of 22 common targets were identified and several were related to the observed phenotype of the mutant. This study indicated that the novel sRNA, srvg23535, is conserved and restricted to Vibrio spp., affecting the utilization of several carbon and nitrogen sources and the response to osmotic and pH stress. These results extend our understanding of sRNA regulation in V. alginolyticus and provide a significant resource for the further study of the precise target mRNAs of srvg23535, which may provide targets for antibacterial therapeutic or attenuated vaccines against Vibrio spp.