FLECS technology for high-throughput screening of hypercontractile cellular phenotypes in fibrosis: A function-first approach to anti-fibrotic drug discovery.

The pivotal role of myofibroblast contractility in the pathophysiology of fibrosis is widely recognized, yet HTS approaches are not available to quantify this critically important function in drug discovery. We developed, validated, and scaled-up a HTS platform that quantifies contractile function of primary human lung myofibroblasts upon treatment with pro-fibrotic TGF-ß1. With the fully automated assay we screened a library of 40,000 novel small molecules in under 80 h of total assay run-time. We identified 42 hit compounds that inhibited the TGF-ß1-induced contractile phenotype of myofibroblasts, and enriched for 19 that specifically target myofibroblasts but not phenotypically related smooth muscle cells. Selected hits were validated in an ex vivo lung tissue models for their inhibitory effects on fibrotic gene upregulation by TGF-ß1. Our results demonstrate that integrating a functional contraction test into the drug screening process is key to identify compounds with targeted and diverse activity as potential anti-fibrotic agents.

Simplified, High-throughput Analysis of Single-cell Contractility using Micropatterned Elastomers.

Cellular contractile force generation is a fundamental trait shared by virtually all cells. These contractile forces are crucial to proper development, function at both the cellular and tissue levels,and regulate the mechanical systems in the body. Numerous biological processes are force-dependent, including motility, adhesion, and division of single-cells, as well as contraction and relaxation of organs such as the heart, bladder, lungs, intestines, and uterus. Given its importance in maintaining proper physiological function, cellular contractility can also drive disease processes when exaggerated or disrupted. Asthma, hypertension, preterm labor, fibrotic scarring, and underactive bladder are all examples of mechanically driven disease processes that could potentially be alleviated with proper control of cellular contractile force. Here, we present a comprehensive protocol for utilizing a novel microplate-based contractility assay technology known as fluorescently labeled elastomeric contractible surfaces (FLECS), that provides simplified and intuitive analysis of single-cell contractility in a massively scaled manner. Herein, we provide a step-wise protocol for obtaining two six-point dose-response curves describing the effects of two contractile inhibitors on the contraction of primary human bladder smooth muscle cells in a simple procedure utilizing just a single FLECS assay microplate, to demonstrate proper technique to users of the method. Using FLECS Technology, all researchers with basic biological laboratories and fluorescent microscopy systems gain access to studying this fundamental but difficult-to-quantify functional cell phenotype, effectively lowering the entry barrier into the field of force biology and phenotypic screening of contractile cell force.

Obesity increases airway smooth muscle responses to contractile agonists.

The asthma-obesity syndrome represents a major public health concern that disproportionately contributes to asthma severity and induces insensitivity to therapy. To date, no study has shown an intrinsic difference between human airway smooth muscle (HASM) cells derived from nonobese subjects and those derived from obese subjects. The objective of this study was to address whether there is a greater response to agonist-induced calcium mobilization, phosphorylation of myosin light chain (MLC), and greater shortening in HASM cells derived from obese subjects. HASM cells derived from nonobese and obese subjects were age and sex matched. Phosphorylation of MLC was measured after having been stimulated by carbachol. Carbachol- or histamine-induced mobilization of calcium and cell shortening were assessed in HASM cells derived from nonobese and obese donors. Agonist-induced MLC phosphorylation, mobilization of calcium, and cell shortening were greater in obese compared with non-obese-derived HASM cells. The MLC response was comparable in HASM cells derived from obese nonasthma and nonobese fatal asthma subjects. HASM cells derived from obese female subjects were more responsive to carbachol than HASM cells derived from obese male subjects. Insulin pretreatment had little effect on these responses. Our results show an increase in agonist-induced calcium mobilization associated with an increase in MLC phosphorylation and an increase in ASM cell shortening in favor of agonist-induced hyperresponsiveness in HASM cells derived from obese subjects. Our studies suggest that obesity induces a retained phenotype of hyperresponsiveness in cultured human airway smooth muscle cells.

Elastomeric sensor surfaces for high-throughput single-cell force cytometry.

As cells with aberrant force-generating phenotypes can directly lead to disease, cellular force-generation mechanisms are high-value targets for new therapies. Here, we show that single-cell force sensors embedded in elastomers enable single-cell force measurements with ~100-fold improvement in throughput than was previously possible. The microtechnology is scalable and seamlessly integrates with the multi-well plate format, enabling highly parallelized time-course studies. In this regard, we show that airway smooth muscle cells isolated from fatally asthmatic patients have innately greater and faster force-generation capacity in response to stimulation than healthy control cells. By simultaneously tracing agonist-induced calcium flux and contractility in the same cell, we show that the calcium level is ultimately a poor quantitative predictor of cellular force generation. Finally, by quantifying phagocytic forces in thousands of individual human macrophages, we show that force initiation is a digital response (rather than a proportional one) to the proper immunogen. By combining mechanobiology at the single-cell level with high-throughput capabilities, this microtechnology can support drug-discovery efforts for clinical conditions associated with aberrant cellular force generation.

Publisher Correction: Elastomeric sensor surfaces for high-throughput single-cell force cytometry.

In the version of this Article originally published, in Fig. 1a, all cells in the top schematic were missing, and in the bottom-left schematic showing multiple pattern shapes, two cells were missing in the bottom-right corner. This figure has now been updated in all versions of the Article.

FLECS Technology for High-Throughput Single-Cell Force Biology and Screening.

Dr. Ivan Pushkarsky from the Department of Bioengineering at UCLA and Forcyte Biotechnologies, Inc. was awarded The President's Innovation Award at the Annual Society of Biomolecular Imaging and Informatics meeting held in San Diego, September 2017. All cell types produce mechanical forces to serve important physiological roles. Since aberrant force-generating phenotypes directly lead to disease, cellular force-generation mechanisms are high-value targets for new therapies. Despite knowledge of their significance in disease, drug developers have had limited access to force-generating cellular phenotypes, especially in the context of high-throughput screening. To serve this valuable need, we have developed a platform microtechnology called "FLECS" that can acquire robust contractility data from 1000s of uniformly patterned single cells simultaneously and seamlessly integrates with the 96- and 384-well plate formats to facilitate large-scale drug screens. This perspective discusses the challenges facing existing laboratory methods for measuring cellular force in the context of drug discovery. It then provides an overview of the FLECS platform, describes how it was designed to overcome many of these challenges, and discusses some exciting work already accomplished with FLECS. It concludes by highlighting the platform nature of the technology and the potential value that it promises for a myriad of drug development efforts.

Gα12 facilitates shortening in human airway smooth muscle by modulating phosphoinositide 3-kinase-mediated activation in a RhoA-dependent manner.

BACKGROUND AND PURPOSE: PI3K-dependent activation of Rho kinase (ROCK) is necessary for agonist-induced human airway smooth muscle cell (HASMC) contraction, and inhibition of PI3K promotes bronchodilation of human small airways. The mechanisms driving agonist-mediated PI3K/ROCK axis activation, however, remain unclear. Given that G12 family proteins activate ROCK pathways in other cell types, their role in M3 muscarinic acetylcholine receptor-stimulated PI3K/ROCK activation and contraction was examined. EXPERIMENTAL APPROACH: Gα12 coupling was evaluated using co-immunoprecipitation and serum response element (SRE)-luciferase reporter assays. siRNA and pharmacological approaches, as well as overexpression of a regulator of G-protein signaling (RGS) proteins were applied in HASMCs. Phosphorylation levels of Akt, myosin phosphatase targeting subunit-1 (MYPT1), and myosin light chain-20 (MLC) were measured. Contraction and shortening were evaluated using magnetic twisting cytometry (MTC) and micro-pattern deformation, respectively. Human precision-cut lung slices (hPCLS) were utilized to evaluate bronchoconstriction. KEY RESULTS: Knockdown of M3 receptors or Gα12 attenuated activation of Akt, MYPT1, and MLC phosphorylation. Gα12 coimmunoprecipitated with M3 receptors, and p115RhoGEF-RGS overexpression inhibited carbachol-mediated induction of SRE-luciferase reporter. p115RhoGEF-RGS overexpression inhibited carbachol-induced activation of Akt, HASMC contraction, and shortening. Moreover, inhibition of RhoA blunted activation of PI3K. Lastly, RhoA inhibitors induced dilation of hPCLS. CONCLUSIONS AND IMPLICATIONS: Gα12 plays a crucial role in HASMC contraction via RhoA-dependent activation of the PI3K/ROCK axis. Inhibition of RhoA activation induces bronchodilation in hPCLS, and targeting Gα12 signaling may elucidate novel therapeutic targets in asthma. These findings provide alternative approaches to the clinical management of airway obstruction in asthma.

Inhibition of PI3K promotes dilation of human small airways in a rho kinase-dependent manner.

BACKGROUND AND PURPOSE: Asthma manifests as a heterogeneous syndrome characterized by airway obstruction, inflammation and hyperresponsiveness (AHR). Although the molecular mechanisms remain unclear, activation of specific PI3K isoforms mediate inflammation and AHR. We aimed to determine whether inhibition of PI3Kδ evokes dilation of airways and to elucidate potential mechanisms. EXPERIMENTAL APPROACH: Human precision cut lung slices from non-asthma donors and primary human airway smooth muscle (HASM) cells from both non-asthma and asthma donors were utilized. Phosphorylation of Akt, myosin phosphatase target subunit 1 (MYPT1) and myosin light chain (MLC) were assessed in HASM cells following either PI3K inhibitor or siRNA treatment. HASM relaxation was assessed by micro-pattern deformation. Reversal of constriction of airways was assessed following stimulation with PI3K or ROCK inhibitors. KEY RESULTS: Soluble inhibitors or PI3Kδ knockdown reversed carbachol-induced constriction of human airways, relaxed agonist-contracted HASM and inhibited pAkt, pMYPT1 and pMLC in HASM. Similarly, inhibition of Rho kinase also dilated human PCLS airways and suppressed pMYPT1 and pMLC. Baseline pMYPT1 was significantly elevated in HASM cells derived from asthma donors in comparison with non-asthma donors. After desensitization of the ß2 -adrenoceptors, a PI3Kδ inhibitor remained an effective dilator. In the presence of IL-13, dilation by a ß agonist, but not PI3K inhibitor, was attenuated. CONCLUSION AND IMPLICATIONS: PI3Kδ inhibitors act as dilators of human small airways. Taken together, these findings provide alternative approaches to the clinical management of airway obstruction in asthma.

Research highlights: manipulating cells inside and out.

We highlight recent work manipulating cells: from whole cells, to intracellular content, and even subcellular gradients in proteins. In the first manuscript, using interdigitated electrode arrays at a controlled tilt angle to a microchannel allows for an array of acoustic nodes that apply force and isolate larger circulating tumor cells from remaining cells in RBC-lysed blood. Moving to the subcellular scale, recent work shows the ability to use rapid bubble generation induced by a pulsed laser to transfect hundreds of thousands of cells in parallel, especially with larger cargo, such as live bacteria. Manipulating at an even finer level, our third highlighted paper applies magnetic nanoparticle-based techniques to the localization of proteins within the cytoplasm in gradient configurations. A recurring theme in the literature is how interfacing at the cellular scale is a key feature enabled by micro & nanotechnology. This feature can be exploited to achieve new capabilities for cell biologists which opens up new fundamental cell biology questions. This matching of scales and the unique advantages are well demonstrated in the articles highlighted.

Research highlights: aptamers on a chip.

Aptamers, oligonucleic acid or peptide molecules with binding affinity to a specific molecule, have gained broad scientific attention due to their stability, ease of production and modification, and durability, and therefore have been employed in a wide range of applications both in basic research and clinical science. Recent advances in high-throughput sequencing are poised to revolutionize the selection of aptamers, while microfluidic and microarray approaches have helped automate these processes of selection. Here we highlight work addressing several challenges in using aptamers more widely. We discuss array-based discovery of multivalent aptamers which is used to develop high affinity or paired aptamers by cleverly selecting new aptamers that bind to previously aptamer-bound proteins. Other highlighted work is addressing problems in analyzing local cell secretions, as well as refreshable sensors that detect signals over hundreds of cycles and can be refreshed with DI water scavenged from the air, leading to less reagent storage towards wearable sensors.

Research highlights: micro-engineered therapies.

Lab on a chip systems have often focused on diagnostic, chemical, and cell analysis applications, however, more recently the scale and/or precision of micro-engineered systems has been applied in developing new therapies. In this issue we highlight recent work using microfluidic and micro-engineered systems in therapeutic applications. We discuss two approaches that use microfluidic precision to address challenges in filtering blood--to both remove unwanted pathogens and toxins and isolate rare cells of interest that have therapeutic potential. In both cases chemically-modified surfaces, a bioengineered mannose binding lectin on magnetic particles and antibody-functionalized reversibly degradable alginate film, provide the functionality to remove (or isolate) target cells of interest. The third paper we highlight generates microscale gels as protective niches for cell-based therapies. Importantly, the microgels are designed to have controlled porosity but also mechanical rigidity to protect housed therapeutic cells, like mesenchymal stem cells. We expect continued progress in micro- & nano-enabled therapies facilitated by the fabrication of new microstructured materials, precise separations, and closed-loop sensing and drug delivery.

Metallization and biopatterning on ultra-flexible substrates via dextran sacrificial layers.

Micro-patterning tools adopted from the semiconductor industry have mostly been optimized to pattern features onto rigid silicon and glass substrates, however, recently the need to pattern on soft substrates has been identified in simulating cellular environments or developing flexible biosensors. We present a simple method of introducing a variety of patterned materials and structures into ultra-flexible polydimethylsiloxane (PDMS) layers (elastic moduli down to 3 kPa) utilizing water-soluble dextran sacrificial thin films. Dextran films provided a stable template for photolithography, metal deposition, particle adsorption, and protein stamping. These materials and structures (including dextran itself) were then readily transferrable to an elastomer surface following PDMS (10 to 70∶1 base to crosslinker ratios) curing over the patterned dextran layer and after sacrificial etch of the dextran in water. We demonstrate that this simple and straightforward approach can controllably manipulate surface wetting and protein adsorption characteristics of PDMS, covalently link protein patterns for stable cell patterning, generate composite structures of epoxy or particles for study of cell mechanical response, and stably integrate certain metals with use of vinyl molecular adhesives. This method is compatible over the complete moduli range of PDMS, and potentially generalizable over a host of additional micro- and nano-structures and materials.

Automated single-cell motility analysis on a chip using lensfree microscopy.

Quantitative cell motility studies are necessary for understanding biophysical processes, developing models for cell locomotion and for drug discovery. Such studies are typically performed by controlling environmental conditions around a lens-based microscope, requiring costly instruments while still remaining limited in field-of-view. Here we present a compact cell monitoring platform utilizing a wide-field (24 mm(2)) lensless holographic microscope that enables automated single-cell tracking of large populations that is compatible with a standard laboratory incubator. We used this platform to track NIH 3T3 cells on polyacrylamide gels over 20 hrs. We report that, over an order of magnitude of stiffness values, collagen IV surfaces lead to enhanced motility compared to fibronectin, in agreement with biological uses of these structural proteins. The increased throughput associated with lensfree on-chip imaging enables higher statistical significance in observed cell behavior and may facilitate rapid screening of drugs and genes that affect cell motility.