Surface Modification of Polystyrene with Boronic Acid for Immunoaffinity-Based Cell Enrichment.

Obtaining an enriched and phenotypically pure cell population from heterogeneous cell mixtures is important for diagnostics and biosensing. Existing techniques such as fluorescent-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) require preincubation with antibodies (Ab) and specialized equipment. Cell immunopanning removes the need for preincubation and can be done with no specialized equipment. The majority of the available antibody-mediated analyte capture techniques require a modification to the Abs for binding. In this work, no antibody modification is used because we take advantage of the carbohydrate chain in the Fc region of Ab. We use boronic acid as a cross-linker to bind the Ab to a modified surface. The process allows for functional orientation and cleavable binding of the Ab. In this study, we created an immunoaffinity matrix on polystyrene (PS), an inexpensive and ubiquitous plastic. We observed a 37% increase in Ab binding compared with that of a passive adsorption approach. The method also displayed a more consistent antibody binding with 17 times less variation in Ab loading among replicates than did the passive adsorption approach. Surface topography analysis revealed that a dextran coating reduced nonspecific antibody binding. Elemental analysis (XPS) was used to characterize the surface at different stages and showed that APBA molecules can bind upside-down on the surface. While upside-down antibodies likely remain functional, their elution behavior might differ from those bound in the desired way. Cell capture experiments show that the new surface has 43% better selectivity and 2.4-fold higher capture efficiency compared to a control surface of passively adsorbed Abs. This specific surface chemistry modification will allow the targeted capture of cells or analytes with the option of chemical detachment for further research and characterization.

GSK-3ß inhibition promotes engraftment of ex vivo-expanded hematopoietic stem cells and modulates gene expression.

Glycogen synthase kinase-3ß (GSK-3ß) has been identified as an important regulator of stem cell function acting through activation of the wingless (Wnt) pathway. Here, we report that treatment with an inhibitor of GSK-3ß, 6-bromoindirubin 3'-oxime (BIO) delayed cell cycle progression by increasing cell cycle time. BIO treatment resulted in the accumulation of late dividing cells enriched with primitive progenitor cells retaining the ability for sustained proliferation. In vivo analysis using a Non-obese diabetic/severe combined immunodeficient (NOD/SCID) transplantation model has demonstrated that pretreatment with BIO promotes engraftment of ex vivo-expanded hematopoietic stem cells. BIO enhanced the engraftment of myeloid, lymphoid and primitive stem cell compartments. Limiting dilution analysis of SCID repopulating cells (SRC) revealed that BIO treatment increased human chimerism without increasing SRC frequency. Clonogenic analysis of human cells derived from the bone marrow of transplant recipient mice demonstrated that a higher level of human chimerism and cellularity was related to increased regeneration per SRC unit. Gene expression analysis showed that treatment with BIO did not modulate the expression of canonical Wnt target genes upregulated during cytokine-induced cell proliferation. BIO increased the expression of several genes regulating Notch and Tie2 signaling downregulated during ex vivo expansion, suggesting a role in improving stem cell engraftment. In addition, treatment with BIO upregulated CDK inhibitor p57 and downregulated cyclin D1, providing a possible mechanism for the delay seen in cell cycle progression. We conclude that transient, pharmacologic inhibition of GSK-3ß provides a novel approach to improve engraftment of expanded HSC after stem cell transplantation.

Donor T cells for CAR T cell therapy.

Adoptive cell therapy using patient-derived chimeric receptor antigen (CAR) T cells redirected against tumor cells has shown remarkable success in treating hematologic cancers. However, wider accessibility of cellular therapies for all patients is needed. Manufacture of patient-derived CAR T cells is limited by prolonged lymphopenia in heavily pre-treated patients and risk of contamination with tumor cells when isolating T cells from patient blood rich in malignant blasts. Donor T cells provide a good source of immune cells for adoptive immunotherapy and can be used to generate universal off-the-shelf CAR T cells that are readily available for administration into patients as required. Genome editing tools such as TALENs and CRISPR-Cas9 and non-gene editing methods such as short hairpin RNA and blockade of protein expression are currently used to enhance CAR T cell safety and efficacy by abrogating non-specific toxicity in the form of graft versus host disease (GVHD) and preventing CAR T cell rejection by the host.

Mimicry of embryonic circulation enhances the hoxa hemogenic niche and human blood development.

Precursors of the adult hematopoietic system arise from the aorta-gonad-mesonephros (AGM) region shortly after the embryonic circulation is established. Here, we develop a microfluidic culture system to mimic the primitive embryonic circulation and address the hypothesis that circulatory flow and shear stress enhance embryonic blood development. Embryonic (HOXA+) hematopoiesis was derived from human pluripotent stem cells and induced from mesoderm by small-molecule manipulation of TGF-ß and WNT signaling (SB/CHIR). Microfluidic and orbital culture promoted the formation of proliferative CD34+RUNX1C-GFP+SOX17-mCHERRY+ precursor cells that were released into the artificial circulation from SOX17+ arterial-like structures. Single-cell transcriptomic analysis delineated extra-embryonic (yolk sac) and HOXA+ embryonic blood differentiation pathways. SB/CHIR and circulatory flow enhance hematopoiesis by the formation of proliferative HOXA+RUNX1C+CD34+ precursor cells that differentiate into monocyte/macrophage, granulocyte, erythrocyte, and megakaryocyte progenitors.

Formation of an adherent hematopoietic expansion culture using fucoidan.

Expansion of transplantable cord blood (CB) progenitors using a stroma requires provision of an exogenous cell source because of the low frequency of stromal precursor cells in CB. A simpler approach from a clinical regulatory perspective would be to provide synthetic extracellular matrix. The aim of this study was to characterize the effect on hematopoietic cell culture of fucoidan. The modulation of cytokine-driven hematopoietic cell expansion by fucoidan was investigated using two-level fractional and full factorial experimental designs. Mobilized peripheral blood (PB) CD34(+) cells were grown over 10 days in various combinations of FL, SCF, TPO, G-CSF, and SDF-1. Cultures were analyzed by immunophenotype. The effect of fucoidan on the divisional recruitment of CD34(+) cells was studied by CFDA-SE division tracking. Fucoidan was adsorbed by polystyrene to tissue culture plates and promoted formation of an adherent hematopoietic culture. Factorial design experiments with mobilized PB-CD34(+) cells showed that fucoidan reduced the production of CD34(+) cells and CD34(+)CXCR4(+) ratio but did not affect the production of monocytic, granulocytic, or megakaryocytic cells. The inhibitory effect of fucoidan on expansion of CB-CD34(+) cells was greater than mobilized PB. Division tracking analysis showed that CD34(+) cell generation times were lengthened by fucoidan. Fucoidan binds growth factors via their heparin-binding domain. The formation of an adherent hematopoietic culture system by fucoidan is most likely mediated by the binding of L-selectin and integrin-αMß2 on myeloids. Fucoidan deserves further investigation as glycan scaffold that is suitable for immobilization of other matrix molecules thought to comprise blood stem cell niche.

Multi-type branching models to describe cell differentiation programs.

Cell proliferation and differentiation is described by a multi-type branching process, a probability model that defines the inheritance of cell type. Cell type is defined by (i) a repression index related to the time required for S-phase entry and (ii) phenotype as determined by cell markers and division history. The inheritance of cell type is expressed as the expected number and type of progeny cells produced by a mother cell given her type. Expressions for the expected number and type of cells produced by a multi-cellular (bulk culture) system are derived from the general model by making the simplifying assumption that cell generation times are independent. The multi-type Smith-Martin model (MSM) makes the further assumption that cell generation times are lag-exponentially distributed with phenotype transitions occurring just before entry into S-phase. The inheritance-modified MSM (IMSM) model includes the influence of generation time memory so that mother and daughter generation times are correlated. The expansion of human cord blood CD34(+) cells by haematopoietic growth factors was division tracked in bulk culture using carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE). The MSM model was fitted to division tracking data to identify cell cycle length, and the rates of CD34 antigen down-regulation and apoptosis. The IMSM model was estimated for mouse granulocyte-macrophage progenitors using live cell imaging data. Multi-type branching models describe cell differentiation dynamics at both single- and multi-cell scales, providing a new paradigm for systematic analysis of stem and progenitor cell development.

The method to generate pulsatile circulatory fluid flow using microfluidics.

Microfluidic chips provide versatile tools to mimic the biological effect of blood flow on pluripotent stem cells (PSC). This paper presents methods for the use of microfluidics to model embryonic circulation using differentiated PSC. Pulsatile circulatory flow is created with a microfluidics device with pressure-driven microvalves and ventricles. Silicone rubber devices are cast from moulds manufactured using standard and 3D laser lithography. The surface chemistry is modified to support the growth of human umbilical vein endothelial cells and pluripotent stem cells. Pulsatile circulatory fluid flow can be applied at specific stages of cell differentiation with direct observation of cellular responses by time-lapse fluorescent microscopy.•Replicable manufacturing protocol of lab scale microfluidic device generating pulsatile fluid flow mimicry embryonic blood circulation.•Integration of human cell lines on microfluidic chip.

Microfluidic Obstacle Arrays Induce Large Reversible Shape Change in Red Blood Cells.

Red blood cell (RBC) shape change under static and dynamic shear stress has been a source of interest for at least 50 years. High-speed time-lapse microscopy was used to observe the rate of deformation and relaxation when RBCs are subjected to periodic shear stress and deformation forces as they pass through an obstacle. We show that red blood cells are reversibly deformed and take on characteristic shapes not previously seen in physiological buffers when the maximum shear stress was between 2.2 and 25 Pa (strain rate 2200 to 25,000 s-1). We quantify the rates of RBC deformation and recovery using Kaplan-Meier survival analysis. The time to deformation decreased from 320 to 23 milliseconds with increasing flow rates, but the distance traveled before deformation changed little. Shape recovery, a measure of degree of deformation, takes tens of milliseconds at the lowest flow rates and reached saturation at 2.4 s at a shear stress of 11.2 Pa indicating a maximum degree of deformation was reached. The rates and types of deformation have relevance in red blood cell disorders and in blood cell behavior in microfluidic devices.

FACS Enrichment of Total Interstitial Cells and Fibroblasts from Adult Mouse Ventricles.

Besides cardiomyocytes, the heart contains numerous interstitial cell types, including cardiac fibroblasts, endothelial cells, immune (myeloid and lymphoid) cells, and mural cells (pericytes and vascular smooth muscle cells), which play key roles in heart repair, regeneration, and disease. We recently published a comprehensive map of cardiac stromal cell heterogeneity and flux in healthy and infarcted hearts using single-cell RNA sequencing (scRNA-seq) ( Farbehi et al., 2019 ). Here, we describe the FACS (Fluorescent Activated Cell Sorting)-based method used in that study for isolation of two cardiac cell fractions from adult mouse ventricles: the total interstitial cell population (TIP; non-cardiomyocytes) and enriched (Pdgfra-GFP+) cardiac fibroblasts.

Correction: Non-reversible heat-induced gelation of a biocompatible Fmoc-hexapeptide in water.

Correction for 'Non-reversible heat-induced gelation of a biocompatible Fmoc-hexapeptide in water' by Jonathan P. Wojciechowski et al., Nanoscale, 2020, 12, 8262-8267, DOI: .

Non-reversible heat-induced gelation of a biocompatible Fmoc-hexapeptide in water.

Hydrogel materials which respond to changes in temperature are widely applicable for injectable drug delivery or tissue engineering applications. Here, we report the unsual heat-induced gelation behaviour of a low molecular weight gelator based on an Fmoc-hexapeptide, Fmoc-GFFRGD. We show that Fmoc-GFFRGD forms kinetically stable fibres when mixed with divalent cations (e.g. Ca2+). Gelation of the mixture occurs upon heating of the mixture which enables electrostatic screening by the divalent cations and hydrophobic collapse of the fibres to give a self-supporting hydrogel network that shows good biocompatibility with L929 fibroblast cells. This work highlights a unique mechanism to initiate heat-induced gelation which should find opportunities as a gelation trigger for injectable hydrogels or fundamental self-assembly applications.

Molecular engineering of the cellulosome complex for affinity and bioenergy applications.

The cellulosome complex has evolved to degrade plant cell walls and, as such, combines tenacious binding to cellulose with diverse catalytic activities against amorphous and crystalline cellulose. Cellulolytic microorganisms provide an extensive selection of domains; those with affinity for cellulose, cohesins and their dockerin binding partners that define cellulosome stoichiometry and architecture, and a range of catalytic activities against carbohydrates. These robust domains provide the building blocks for molecular design. This review examines how protein modules derived from the cellulosome have been incorporated into chimaeric proteins to provide biosynthetic tools for research and industry. These applications include affinity tags for protein purification, and non-chemical methods for immobilisation and presentation of recombinant protein domains on cellulosic substrates. Cellulosomal architecture provides a paradigm for design of enzymatic complexes that synergistically combine multiple catalytic subunits to achieve higher specific activity than would be obtained using free enzymes. Multimeric enzymatic complexes may have industrial applications of relevance for an emerging carbon economy. Biocatalysis will lead to more efficient utilisation of renewable carbon-fixing energy sources with the added benefits of reducing chemical waste streams and reliance on petroleum.

Droplet-based single cell RNAseq tools: a practical guide.

Droplet based scRNA-seq systems such as Drop-seq, inDrop and Chromium 10X have been the catalyst for the wide adoption of high-throughput scRNA-seq technologies in the research laboratory. In order to understand the capabilities of these systems to deeply interrogate biology; here we provide a practical guide through all the steps involved in a typical scRNA-seq experiment. Through comparing and contrasting these three main droplet based systems (and their derivatives), we provide an overview of all critical considerations in obtaining high quality and biologically relevant data. We also discuss the limitations of these systems and how they fit into the emerging field of Genomic Cytometry.

Single-cell expression profiling reveals dynamic flux of cardiac stromal, vascular and immune cells in health and injury.

Besides cardiomyocytes (CM), the heart contains numerous interstitial cell types which play key roles in heart repair, regeneration and disease, including fibroblast, vascular and immune cells. However, a comprehensive understanding of this interactive cell community is lacking. We performed single-cell RNA-sequencing of the total non-CM fraction and enriched (Pdgfra-GFP+) fibroblast lineage cells from murine hearts at days 3 and 7 post-sham or myocardial infarction (MI) surgery. Clustering of >30,000 single cells identified >30 populations representing nine cell lineages, including a previously undescribed fibroblast lineage trajectory present in both sham and MI hearts leading to a uniquely activated cell state defined in part by a strong anti-WNT transcriptome signature. We also uncovered novel myofibroblast subtypes expressing either pro-fibrotic or anti-fibrotic signatures. Our data highlight non-linear dynamics in myeloid and fibroblast lineages after cardiac injury, and provide an entry point for deeper analysis of cardiac homeostasis, inflammation, fibrosis, repair and regeneration.

Chimeric protein for selective cell attachment onto cellulosic substrates.

We have developed a fusion protein (CBD-LG) incorporating a cellulose-binding domain and an antibody binding domain, protein LG, to provide an adaptor molecule for cell separation with regenerated cellulose hollow fiber arrays. A single hollow fiber cell adhesion assay utilizing a CD34+ cell line, KG1a, was used to investigate whether ligand affinity interactions were strong enough for cell attachment and separation. CBD-LG efficiently captured CD34+ cells labeled with the mouse IgG2a monoclonal antibody MHCD3400. However, it was not possible to bind CD34+ cells labeled with an IgG1 antibody (HPCA-2). The low affinity of HPCA-2 for LG was overcome by secondary antibodies: KG1a cells that were dual labeled with HPCA-2 followed by rat anti-mouse IgG1 adhered inside hollow fibers coated with CBD-LG. Alternatively, immobilized rabbit polyclonal anti-mouse IgG1 captured cells labeled with HPCA-2. The development of an adaptor molecule to display recombinant domains at the surface of hollow fibers will be an effective tool to investigate cellular ligand-receptor interactions, a necessary step in the development of hollow fiber bioreactors for manufacture of human cellular products.

Ex Vivo Expansion of Hematopoietic Stem Cells to Improve Engraftment in Stem Cell Transplantation.

The efficient use of hematopoietic stem cells (HSC) for transplantation is often limited by the relatively low numbers of HSC collected. The ex vivo expansion of HSC for clinical use is a potentially valuable and safe approach to increase HSC numbers thereby increasing engraftment and reducing the risk of morbidity from infection. Here, we describe a protocol for the robust ex vivo expansion of human CD34(+) HSC isolated from umbilical cord blood. The protocol described can efficiently generate large numbers of HSC. We also describe a flow cytometry-based method using high-resolution division tracking to characterize the kinetics of HSC growth and differentiation. Utilizing the guidelines discussed, it is possible for investigators to use this protocol as presented or to modify it for their specific needs.

High-fidelity replication of thermoplastic microneedles with open microfluidic channels.

Development of microneedles for unskilled and painless collection of blood or drug delivery addresses the quality of healthcare through early intervention at point-of-care. Microneedles with submicron to millimeter features have been fabricated from materials such as metals, silicon, and polymers by subtractive machining or etching. However, to date, large-scale manufacture of hollow microneedles has been limited by the cost and complexity of microfabrication techniques. This paper reports a novel manufacturing method that may overcome the complexity of hollow microneedle fabrication. Prototype microneedles with open microfluidic channels are fabricated by laser stereolithography. Thermoplastic replicas are manufactured from these templates by soft-embossing with high fidelity at submicron resolution. The manufacturing advantages are (a) direct printing from computer-aided design (CAD) drawing without the constraints imposed by subtractive machining or etching processes, (b) high-fidelity replication of prototype geometries with multiple reuses of elastomeric molds, (c) shorter manufacturing time compared to three-dimensional stereolithography, and (d) integration of microneedles with open-channel microfluidics. Future work will address development of open-channel microfluidics for drug delivery, fluid sampling and analysis.

Engineered proteins containing the cohesin and dockerin domains from Clostridium thermocellum provides a reversible, high affinity interaction for biotechnology applications.

The cohesin-dockerin interaction, which is responsible for the formation of the cellulosome complex of cellulolytic bacteria, is a calcium-dependent, high affinity interaction. In this study, the cohesin (Cip7) and dockerin (Doc) domains of Clostridium thermocellum were fused to the cellulose-binding domain (CBD) of C. cellulovorans and the antibody-binding domain, protein LG, respectively, to form CBD-Cip7 and LG-Doc. Immobilised CBD-Cip7 was able to bind LG-Doc and subsequently antibody as determined using surface plasmon resonance. Binding was reversed by the removal of Ca2+ with EDTA. The dockerin containing fusion protein was affinity purified using an immobilised cohesin domain. Elution of the LG-Doc from the cohesin column was with EDTA. This affinity chromatography was repeated using an LG-dockerin column for the purification of cohesin fusion protein. The fusion proteins created in this report have shown that the properties of the cohesin and dockerin domains can be transferred to other protein domains and that the interaction between the cohesin and dockerin is specific, Ca2+ -dependent and reversible. We have shown that the cohesin-dockerin interaction has several properties making it suitable for use in recombinant fusion protein production and purification.