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Only a handful of US Food and Drug Administration (FDA) Emergency Use Authorizations exist for drug and biologic therapeutics that treat severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2) infection. Potential therapeutics include repurposed drugs, some with cardiac liabilities. We report on a chronic preclinical drug screening platform, a cardiac microphysiological system (MPS), to assess cardiotoxicity associated with repurposed hydroxychloroquine (HCQ) and azithromycin (AZM) polytherapy in a mock phase I safety clinical trial. The MPS contained human heart muscle derived from induced pluripotent stem cells. The effect of drug response was measured using outputs that correlate with clinical measurements, such as QT interval (action potential duration) and drug‐biomarker pairing. Chronic exposure (10 days) of heart muscle to HCQ alone elicited early afterdepolarizations and increased QT interval past 5 days. AZM alone elicited an increase in QT interval from day 7 onward, and arrhythmias were observed at days 8 and 10. Monotherapy results mimicked clinical trial outcomes. Upon chronic exposure to HCQ and AZM polytherapy, we observed an increase in QT interval on days 4–8. Interestingly, a decrease in arrhythmias and instabilities was observed in polytherapy relative to monotherapy, in concordance with published clinical trials. Biomarkers, most of them measurable in patients' serum, were identified for negative effects of monotherapy or polytherapy on tissue contractile function, morphology, and antioxidant protection. The cardiac MPS correctly predicted clinical arrhythmias associated with QT prolongation and rhythm instabilities. This high content system can help clinicians design their trials, rapidly project cardiac outcomes, and define new monitoring biomarkers to accelerate access of patients to safe coronavirus disease 2019 (COVID‐19) therapeutics. [ABSTRACT FROM AUTHOR]

Soft lithography techniques using polydimethylsiloxane (PDMS) are a cornerstone of microfluidic microdevices and emerging technologies such as microphysiological systems (MPS). Most of these systems employ hydrophobic small molecules during either stem cell differentiation, drug screening, or organoid development. However, due to PDMS's structure and hydrophobicity, lipophilic molecules are strongly absorbed creating unpredictable concentrations of mitogens, drugs, differentiation factors, and analytes, which is a major limitation in its use for biological applications. In this study, several catechol‐functionalized calix[4]arene based macrocyclic polyphenols (MPPs) are synthesized and coated on PDMS through a dip‐coating or flow through process. One molecule, MPP5cone, synthesized from catechol and resorcinol in its cone isomer form, increases the hydrophilicity of PDMS and drastically reduces the absorption of a number of hydrophobic drug surrogates, while preserving high oxygen permeability, good cell viability and function. However, simple rules of molecular absorption based on Log P are not observed, suggesting screening barrier coatings for PDMS with single probes is not sufficient. The coating procedure is easily translated to microfluidic devices by infusion through channels with a pump, and therefore should find use in applications where molecular absorption into PDMS is a significant problem. [ABSTRACT FROM AUTHOR]

The decrease in contractility in myocardium adjacent (border zone; BZ) to a myocardial infarction (MI) is correlated with an increase in reactive oxygen species (ROS). We hypothesized that injection of a thermoresponsive hydrogel, with ROS scavenging properties, into the MI would decrease ROS and improve BZ function. Fourteen sheep underwent antero‐apical MI. Seven sheep had a comb‐like copolymer synthesized from N‐isopropyl acrylamide (NIPAAm) and 1500 MW methoxy poly(ethylene glycol) methacrylate, (NIPAAm‐PEG1500), injected (20 × 0.5 mL) into the MI zone 40 min after MI (MI + NIPAAm‐PEG1500) and seven sheep were MI controls. Cardiac MRI was performed 2 weeks before and 6 weeks after MI + NIPAAm‐PEG1500. BZ wall thickness at end systole was significantly higher for MI + NIPAAm‐PEG1500 (12.32 ± 0.51 mm/m2 MI + NIPAAm‐PEG1500 vs. 9.88 ± 0.30 MI; p =.023). Demembranated muscle force development for BZ myocardium 6 weeks after MI was significantly higher for MI + NIPAAm‐PEG1500 (67.67 ± 2.61 mN/m2 MI + NIPAAm‐PEG1500 vs. 40.53 ± 1.04 MI; p <.0001) but not significantly different from remote myocardium or BZ or non‐operated controls. Levels of ROS in BZ tissue were significantly lower in the MI + NIPAAm‐PEG1500 treatment group (hydroxyl p =.0031; superoxide p =.0182). We conclude that infarct injection of the NIPAAm‐PEG1500 hydrogel with ROS scavenging properties decreased ROS and improved contractile protein function in the border zone 6 weeks after MI. [ABSTRACT FROM AUTHOR]

Abstract: Quantification of abnormal contractile motions of cardiac tissue has been a noteworthy challenge and significant limitation in assessing and classifying the drug‐induced arrhythmias (i.e., Torsades de pointes). To overcome these challenges, researchers have taken advantage of computational image processing tools to measure contractile motion from cardiomyocytes derived from human induced pluripotent stem cells (hiPSC‐CMs). However, the amplitude and frequency analysis of contractile motion waveforms does not produce sufficient information to objectively classify the degree of variations between two or more sets of cardiac contractile motions. In this paper, we generated contractile motion data from beating hiPSC‐CMs using motion tracking software based on optical flow analysis, and then implemented a computational algorithm, phase space reconstruction (PSR), to derive parameters (embedding, regularity, and fractal dimensions) to further characterize the dynamic nature of the cardiac contractile motions. Application of drugs known to cause cardiac arrhythmia induced significant changes to these resultant dimensional parameters calculated from PSR analysis. Integrating this new computational algorithm with the existing analytical toolbox of cardiac contractile motions will allow us to expand current assessments of cardiac tissue physiology into an automated, high‐throughput, and quantifiable manner which will allow more objective assessments of drug‐induced proarrhythmias. [ABSTRACT FROM AUTHOR]

Human embryonic stem (hES) cells are pluripotent, capable of differentiating into any cell type of the body, and therefore have the ability to provide insights into mechanisms of human development and disease, as well as to provide a potentially unlimited supply of cells for cell-based therapy and diagnostics. Knowledge of the adhesion receptors that hES cells employ to engage extracellular matrix (ECM) proteins is of basic biological interest and can enhance the design of cell culture and implantation systems to enable these biomedical applications. Although hES cells express a variety of cell surface receptors, little is known about which integrins are involved during subculture and passage. Matrigel is broadly used as a cell adhesive matrix for hES cell culture. Here, we sought to identify which integrins hES cells exploit for adhesion to Matrigel-coated surfaces in defined medium conditions. Using RT-PCR, flow cytometry, and fluorescence immunochemistry, we found that numerous integrins were expressed by H1 hES cells; however, antibody blocking assays indicated that only αv β3, α6, β1, and α2 β1, played a significant role in the initial adhesion of the hES cells to Matrigel in defined medium conditions. We subsequently identified a cohort of synthetic peptides that, when adsorbed to the culture surface, promoted H1 hES cell attachment and proliferation, as well as maintained a pluripotent phenotype. Peptides designed to engage with αv β3, α6, β1, and α2 β1 integrins and syndecan-1 were tested both individually and in various combinations. A combination of two integrin-engaging peptides (AG-10, C-16) and one syndecan-engaging peptide (AG-73) was sufficient to promote hES cell adhesion, maintenance, and proliferation. We propose that a specific integrin "fingerprint" is necessary for maintenance of hES cell self-renewal, and synthetic culture systems must capture this engagement profile for hES cells to remain undifferentiated. [ABSTRACT FROM AUTHOR]

A number of techniques currently exist that allow researchers to generate spatially resolved patterns of chemistry and topography on the nanometer length scale. Both chemically and topographically nanopatterned surfaces can be generated to more accurately mimic the natural extracellular environment. Chemically patterned surfaces can also be used to study tightly controlled and highly specific cell--cell and cell-substrate interactions or to create increasingly densely packed biosensors. From a biological standpoint, these methods enable fabrication of elaborate interfaces to mechanistically study the effects of cell adhesion ligand density, spacing, clustering, and spatial distribution on cell fate and function. The most commonly used nanopatterning techniques in the biomaterials arena are reviewed here, including scanning probe, electron beam, colloidal, and imprint lithographies, critically examining the resolution available and the scalability of the technique for generating the number of surfaces necessary for statistically relevant cell culture studies. [ABSTRACT FROM AUTHOR]

The signaling domain of Sonic hedgehog (Shh), a potent upstream regulator of cell fate that has been implicated in osteoblast differentiation from undifferentiated mesenchymal cells in its endogenous form, was investigated in an immobilized form as a means for accelerating differentiation of uncommitted cells to the osteoblast phenotype. A recombinant cysteine‐modified N‐terminal Shh (mShh) was synthesized, purified, and immobilized onto interpenetrating polymer network (IPN) surfaces also grafted with a bone sialoprotein‐derived peptide containing the Arg‐Gly‐Asp (RGD) sequence (bsp‐RGD (15)), at calculated densities of 2.42 and 10 pmol/cm2, respectively. The mitogenic effect of mShh was dependent on the mode of presentation, as surfaces with immobilized mShh and bsp‐RGD (15) had no effect on the growth rate of rat bone marrow‐derived mesenchymal stem cells (BMSCs), while soluble mShh enhanced cell growth compared to similar surface without mShh supplementation. In conjunction with media supplemented with bone morphogenetic protein‐2 and ‐4, mShh and bsp‐RGD (15)‐grafted IPN surfaces enhanced the alkaline phosphatase activity of BMSCs compared with tissue culture polystyrene and bsp‐RGD (15)‐grafted IPN surfaces supplemented with soluble mShh, indicating enhanced osteoblast differentiation. The adhesive peptide bsp‐RGD (15) was necessary for cell attachment and proliferation, as well as differentiation in response to immobilized mShh. The addition of immobilized Shh substantially improved the differentiation of uncommitted BMSCs to the osteoblast lineage, and therefore warrants further testing in vivo to examine the effect of the stated biomimetic system on peri‐implant bone formation and implant fixation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007 [ABSTRACT FROM AUTHOR]

Interpenetrating polymer networks (IPNs) of poly(acrylamide- co-ethylene glycol/acrylic acid) [p(AAm- co-EG/AAc)] functionalized with an -Arg-Gly-Asp- containing peptide derived from rat bone sialoprotein [bsp-RGD(15)] were grafted to titanium implants in an effort to modulate osteoblast behavior in vitro. Surface characterization data were consistent with the presence of an IPN, and ligand density measurements established that the range of peptide density on the modified implants spanned three orders of magnitude (0.01-20 pmol/cm2). In vitro biological characterization of the modified implants employing the primary rat calvarial osteoblast (RCO) model resulted in the identification of a critical ligand density (0.01 < Γcrit < 0.1 pmol/cm2) for maximal support of the osteoblast phenotype. After 14 and 21 days, mineralization was greater on the 0.1 and 10 pmol/cm2 bsp-RGD(15) modified implants compared to the base titanium and other control surfaces. The observed effects were attributed to specific interactions with bsp-RGD(15) and support the concept that peptide-modified implants can enhance the kinetics of differentiation of the cells they contact. These results suggest that in vivo biological performance evaluation of these biomimetic implant surfaces is merited. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1366-1376, 2006 [ABSTRACT FROM AUTHOR]