Eph-ephrin signaling couples endothelial cell sorting and arterial specification.

Cell segregation allows the compartmentalization of cells with similar fates during morphogenesis, which can be enhanced by cell fate plasticity in response to local molecular and biomechanical cues. Endothelial tip cells in the growing retina, which lead vessel sprouts, give rise to arterial endothelial cells and thereby mediate arterial growth. Here, we have combined cell type-specific and inducible mouse genetics, flow experiments in vitro, single-cell RNA sequencing and biochemistry to show that the balance between ephrin-B2 and its receptor EphB4 is critical for arterial specification, cell sorting and arteriovenous patterning. At the molecular level, elevated ephrin-B2 function after loss of EphB4 enhances signaling responses by the Notch pathway, VEGF and the transcription factor Dach1, which is influenced by endothelial shear stress. Our findings reveal how Eph-ephrin interactions integrate cell segregation and arteriovenous specification in the vasculature, which has potential relevance for human vascular malformations caused by EPHB4 mutations.

Label-free separation of peripheral blood mononuclear cells from whole blood by gradient acoustic focusing.

Efficient techniques for separating target cells from undiluted blood are necessary for various diagnostic and research applications. This paper presents acoustic focusing in dense media containing iodixanol to purify peripheral blood mononuclear cells (PBMCs) from whole blood in a label-free and flow-through format. If the blood is laminated or mixed with iodixanol solutions while passing through the resonant microchannel, all the components (fluids and cells) rearrange according to their acoustic impedances. Red blood cells (RBCs) have higher effective acoustic impedance than PBMCs. Therefore, they relocate to the pressure node despite the dense medium, while PBMCs stay near the channel walls due to their negative contrast factor relative to their surrounding medium. By modifying the medium and thus tuning the contrast factor of the cells, we enriched PBMCs relative to RBCs by a factor of 3600 to 11,000 and with a separation efficiency of 85%. That level of RBC depletion is higher than most other microfluidic methods and similar to that of density gradient centrifugation. The current acoustophoretic chip runs up to 20 µl/min undiluted whole blood and can be integrated with downstream analysis.

A novel electrophoretic assisted hydrophobic microdevice for enhancing blood cell sorting: design and numerical simulation.

Microfluidic technology has great advantages in the precise manipulation of micro-nano particles, and the hybrid microfluidic separation technology has attracted much attention due to the advantages of both active and passive separation technology at the same time. In this paper, the hydrophoresis sorting technique is combined with the dielectrophoresis technique, and a dielectrophoresis-assisted hydrophoresis microdevice is studied to separate blood cells. By using the dielectrophoresis force to change the suspension position of the cells in the channel, the scope of the hydrophoresis device for sorting particles is expanded. At the same time, the effects of microchannel width, fluid velocity, and electrode voltage on cell sorting were discussed, and the cell separation process was simulated. This work has laid a certain theoretical foundation for the rapid diagnosis of diseases in practical applications.

Magnetic CAR T cell purification using an anti-G4S linker antibody.

Chimeric antigen receptor (CAR) redirected T cells are successfully employed in the combat against several hematological malignancies, however, are often compromised by low transduction rates making refinement of the CAR T cell products necessary. Here, we report a broadly applicable enrichment protocol relying on marking CAR T cells with an anti-glycine4-serine (G4S) linker antibody followed by magnetic activated cell sorting (MACS). The protocol is broadly applicable since the G4S peptide is an integral part of the vast majority of CARs as it links the VH and VL recognition domains. We demonstrate the feasibility by using the canonical second generation CARs specific for CEA and Her2, respectively, obtaining highly purified CAR T cell products in a one-step procedure without impairing cell viability. The protocol is also applicable to a dual specific CAR (tandem CAR). Except for CD39, T cell activation/exhaustion markers were not upregulated after separation. Purified CAR T cells retained their functionality with respect to antigen-specific cytokine secretion, cytotoxicity, and the capacity to proliferate and eliminate cognate tumor cells upon repetitive stimulation. Collectively, the one-step protocol for purifying CAR T cells extends the toolbox for preclinical research and specifically for clinical CAR T cell manufacturing.

A nanowell platform to identify, sort and expand high antibody-producing cells.

Increased use of therapeutic monoclonal antibodies and the relatively high manufacturing costs fuel the need for more efficient production methods. Here we introduce a novel, fast, robust, and safe isolation platform for screening and isolating antibody-producing cell lines using a nanowell chip and an innovative single-cell isolation method. An anti-Her2 antibody producing CHO cell pool was used as a model. The platform; (1) Assures the single-cell origin of the production clone, (2) Detects the antibody production of individual cells and (3) Isolates and expands the individual cells based on their antibody production. Using the nanowell platform we demonstrated an 1.8-4.5 increase in anti-Her2 production by CHO cells that were screened and isolated with the nanowell platform compared to CHO cells that were not screened. This increase was also shown in Fed-Batch cultures where selected high production clones showed titers of 19-100 mg/L on harvest day, while the low producer cells did not show any detectable anti-Her2 IgG production. The screening of thousands of single cells is performed under sterile conditions and the individual cells were cultured in buffers and reagents without animal components. The time required from seeding a single cell and measuring the antibody production to fully expanded clones with increased Her-2 production was 4-6 weeks.

Microfluidics as an emerging paradigm for assisted reproductive technology: A sperm separation perspective.

Millions of people are subject to infertility worldwide and one in every six people, regardless of gender, experiences infertility at some period in their life, according to the World Health Organization. Assisted reproductive technologies are defined as a set of procedures that can address the infertility issue among couples, culminating in the alleviation of the condition. However, the costly conventional procedures of assisted reproduction and the inherent vagaries of the processes involved represent a setback for its successful implementation. Microfluidics, an emerging tool for processing low-volume samples, have recently started to play a role in infertility diagnosis and treatment. Given its host of benefits, including manipulating cells at the microscale, repeatability, automation, and superior biocompatibility, microfluidics have been adopted for various procedures in assisted reproduction, ranging from sperm sorting and analysis to more advanced processes such as IVF-on-a-chip. In this review, we try to adopt a more holistic approach and cover different uses of microfluidics for a variety of applications, specifically aimed at sperm separation and analysis. We present various sperm separation microfluidic techniques, categorized as natural and non-natural methods. A few of the recent developments in on-chip fertilization are also discussed.

One-step rapid tracking and isolation of senescent cells in cellular systems, tissues, or animal models via GLF16.

Identification and isolation of senescent cells is challenging, rendering their detailed analysis an unmet need. We describe a precise one-step protocol to fluorescently label senescent cells, for flow cytometry and fluorescence microscopy, implementing a fluorophore-conjugated Sudan Black-B analog, GLF16. Also, a micelle-based approach allows identification of senescent cells in vivo and in vitro, enabling live-cell sorting for downstream analyses and live in vivo tracking. Our protocols are applicable to cellular systems, tissues, or animal models where senescence is present. For complete details on the use and execution of this protocol, please refer to Magkouta et al.1.

A hydrodynamic-based dual-function microfluidic chip for high throughput discriminating tumor cells.

A hydrodynamic-based microfluidic chip consisted of two function units that could not only separate tumor cells (TCs) from whole blood but also remove residual blood cells was designed. The separation of TCs was achieved by a straight contraction-expansion array (CEA) microchannel on the front end of the chip. The addition of contractive structure brought a micro-vortex like Dean vortex that promoted cell focusing in the channel, while when cells entered the dilated region, the wall-induced lift force generated by the channel wall gave cells a push away from the wall. As the wall-induced lift force is proportional to the third power of the cell diameter, TCs with larger diameter will have a larger lateral migration under the wall-induced lift force, realizing the separation of TCs from blood sample. Fluorescent particles with diameters of 19.3 µm and 4.5 µm were used to simulate TCs and red blood cells, respectively, to verify the separation capacity of the proposed CEA microchannel for particles with different diameter. And a separation efficiency 98.7% for 19.3 µm particles and a removal rate 96.2% for 4.5 µm particles was observed at sample flow rate of 10 µL min-1 and sheath flow rate of 190 µL min-1. In addition, a separation efficiency about 96.1% for MCF-7 cells (stained with DiI) and removal rates of 96.2% for red blood cells (RBCs) and 98.7% for white blood cells (WBCs) were also obtained under the same condition. However, on account of the large number of blood cells in the blood, there will be a large number of blood cells remained in the isolated TCs, so a purification unit based on hydrodynamic filtration (HDF) was added after the separation microchannel. The purification channel is a size-dictated cell filter that can remove residual blood cells but retain TCs, thus achieving the purification of TCs. Combined the CEA microchannel and the purifier, the microchip facilitates sorting of MCF-7 cells from whole blood with a separation rate about 95.3% and a removal rate over 99.99% for blood cells at a sample flow rate of 10 µL min-1, sheath flow rate of 190 µL min-1 and washing flow rate of 63 µL min-1.

Surface Markers for the Identification of Cancer Stem Cells.

Cancer stem cells have genetic and functional characteristics which can turn them resistant to standard cancer therapeutic targets. Identification of these cells is challenging and is done mainly by detecting the expression of antigens specific to stem cells. Currently, there is a significant number of surface markers available which can detect cancer stem cells by directly targeting the specific antigens present in cells. These markers possess differential expression patterns and sub-localizations in cancer stem cells compared to nonneoplastic and somatic cells. In addition to these biomarkers, multiple analytical methods and techniques, including functional assays, cell sorting, filtration approaches, and xenotransplantation methods, are used to identify cancer stem cells. This chapter will overview the functional significance of cancer stem cells, their biological correlations, specific markers, and detection methods.

Deep learning-enabled detection of rare circulating tumor cell clusters in whole blood using label-free, flow cytometry.

Metastatic tumors have poor prognoses for progression-free and overall survival for all cancer patients. Rare circulating tumor cells (CTCs) and rarer circulating tumor cell clusters (CTCCs) are potential biomarkers of metastatic growth, with CTCCs representing an increased risk factor for metastasis. Current detection platforms are optimized for ex vivo detection of CTCs only. Microfluidic chips and size exclusion methods have been proposed for CTCC detection; however, they lack in vivo utility and real-time monitoring capability. Confocal backscatter and fluorescence flow cytometry (BSFC) has been used for label-free detection of CTCCs in whole blood based on machine learning (ML) enabled peak classification. Here, we expand to a deep-learning (DL)-based, peak detection and classification model to detect CTCCs in whole blood data. We demonstrate that DL-based BSFC has a low false alarm rate of 0.78 events per min with a high Pearson correlation coefficient of 0.943 between detected events and expected events. DL-based BSFC of whole blood maintains a detection purity of 72% and a sensitivity of 35.3% for both homotypic and heterotypic CTCCs starting at a minimum size of two cells. We also demonstrate through artificial spiking studies that DL-based BSFC is sensitive to changes in the number of CTCCs present in the samples and does not add variability in detection beyond the expected variability from Poisson statistics. The performance established by DL-based BSFC motivates its use for in vivo detection of CTCCs. Using transfer learning, we additionally validate DL-based BSFC on blood samples from different species and cancer cell types. Further developments of label-free BSFC to enhance throughput could lead to critical applications in the clinical detection of CTCCs and ex vivo isolation of CTCC from whole blood with minimal disruption and processing steps.

Isolation and Immunophenotyping of Leukocytes from the Human Maternal-Fetal Interface.

During human pregnancy, leukocytes that infiltrate the maternal-fetal interface play a major role in establishing a delicate balance between immune tolerance and functional response and setting the inflammatory process that leads to labor. Here we describe two methods for isolating immune cells from the chorioamniotic membranes (decidua parietalis) and placental blood (decidua basalis) that combine gentle enzymatic digestion, magnetic cell sorting, and density gradient. Isolated leukocytes can be immunophenotypified by flow cytometry, and both isolation methods are compatible with downstream cellular and molecular applications, such as cell culture, transcriptome, and proteome analyses.

Placental Trophoblast Cell Isolation from the Term Placenta.

Multiple cell lines have been utilized over time in studying placental biology. Still, most of them rely on choriocarcinoma cells or immortalized trophoblast cells that may not be entirely comparable with actual human placental trophoblast cells. Term placentas can be a source of primary villous trophoblasts. However, challenges remain in isolating them and maintaining them in extended culture. This manuscript describes our three-phase protocol utilizing enzymatic/mechanical digestion, modified Percoll gradient density separation, and immunopurification using magnetic beads. The resulting trophoblast culture remains viable for an extended period and highly pure after initial passaging.

Microfluidic System Consisting of a Magnetic 3D-Printed Microchannel Filter for Isolation and Enrichment of Circulating Tumor Cells Targeted by Anti-HER2/MOF@Ferrite Core-Shell Nanostructures: A Theranostic CTC Dialysis System.

Low number of circulating tumor cells (CTCs) in the blood samples and time-consuming properties of the current CTC isolation methods for processing a small volume of blood are the biggest obstacles to CTC usage in practice. Therefore, we aimed to design a CTC dialysis system with the ability to process cancer patients' whole blood within a reasonable time. Two strategies were employed for developing this dialysis setup, including (i) synthesizing novel in situ core-shell Cu ferrites consisting of the Cu-CuFe2O4 core and the MIL-88A shell, which are targeted by the anti-HER2 antibody for the efficient targeting and trapping of CTCs; and (ii) fabricating a microfluidic system containing a three-dimensional (3D)-printed microchannel filter composed of a polycaprolactone/Fe3O4 nanoparticle composite with pore diameter less than 200 µm on which a high-voltage magnetic field is focused to enrich and isolate the magnetic nanoparticle-targeted CTCs from a large volume of blood. The system was assessed in different aspects including capturing the efficacy of the magnetic nanoparticles, CTC enrichment and isolation from large volumes of human blood, side effects on blood cells, and the viability of CTCs after isolation for further analysis. Under the optimized conditions, the CTC dialysis system exhibited more than 80% efficacy in the isolation of CTCs from blood samples. The isolated CTCs were viable and were able to proliferate. Moreover, the CTC dialysis system was safe and did not cause side effects on normal blood cells. Taken together, the designed CTC dialysis system can process a high volume of blood for efficient dual diagnostic and therapeutic purposes.

Single-Cell Proteomics by Barcoded Phage-Displayed Screening via an Integrated Microfluidic Chip.

Recent advancements in the profiling of proteomes at the single-cell level necessitate the development of quantitative and versatile platforms, particularly for analyzing rare cells like circulating tumor cells (CTCs). In this chapter, we present an integrated microfluidic chip that utilizes magnetic nanoparticles to capture single tumor cells with exceptional efficiency. This chip enables on-chip incubation and facilitates in situ analysis of cell-surface protein expression. By combining phage-based barcoding with next-generation sequencing technology, we successfully monitored changes in the expression of multiple surface markers induced by CTC adherence. This innovative platform holds significant potential for comprehensive screening of multiple surface antigens simultaneously in rare cells, offering single-cell resolution. Consequently, it will contribute valuable insights into biological heterogeneity and human disease.

Practicalities of Cell Sorting.

Cell sorting is a technique commonly used in academic and biotechnology laboratories in order to separate out cells or particles of interest from heterogeneous populations. Cell sorters use the same principles as flow cytometry analyzers, but instead of cell populations passing to the waste of the instrument, they can be collected for further studies including DNA sequencing as well as other genomic, in vitro and in vivo experiments. This chapter aims to give an overview of cell sorting, the different types of cell sorters, details on how a cell sorter works, as well as protocols that are useful when embarking on a journey with cell sorting.

Image-Enabled Cell Sorting Using the BD CellView Technology.

This chapter is an extension of the original publication by Schraivogel et al. (Science 375:315-320, 2022) which described, for the first time, image-enabled and high-speed cell sorting based on the BD CellView technology. It summarizes the technical aspects of the instrument in an easy-to-digest form and provides example-based guidance toward implementation of the CellView-based image cell sorting technology. As an example, it explains how to use the image-enabled cell sorter to analyze the chemically induced fragmentation of the Golgi apparatus in HeLa cells-an experiment that was alluded to in the original publication but was not included in the manuscript due to space constraints. The chemically induced Golgi fragmentation sort illustrates an elegant example of the utility of image-enabled cell sorting as a significant expansion of the single-cell toolbox. It is such a striking phenotype when analyzed with image cytometry but undetectable when using conventional flow cytometry. Described in a straightforward and concise manner, this experiment serves as a standard system assurance for image-based cell sorters.

Co-staining with Fluorescent Antibodies and Antibody-Derived Tags for Cell Sorting Prior to CITE-Seq.

The paired detection of the transcriptome and proteome at single-cell resolution provides exquisite insight to immune mechanisms in health and disease. Here, we describe a detailed protocol wherein we combine cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq), a technique utilizing antibody-derived tags (ADTs) to profile mRNA and proteins simultaneously via sequencing, with fluorescence-activated cell sorting to enrich cell populations. Our protocol provides step-by-step guidance on co-staining cells with both fluorescent antibodies and ADTs simultaneously, instructions on cell sorting and an overview of the single-cell capture workflow using the BD Rhapsody™ system. This method is useful for in-depth single-cell characterization on sorted rare cell populations.

Pooled CRISPR screening of high-content cellular phenotypes using ghost cytometry.

Recent advancements in image-based pooled CRISPR screening have facilitated the mapping of diverse genotype-phenotype associations within mammalian cells. However, the rapid enrichment of cells based on morphological information continues to pose a challenge, constraining the capacity for large-scale gene perturbation screening across diverse high-content cellular phenotypes. In this study, we demonstrate the applicability of multimodal ghost cytometry-based cell sorting, including both fluorescent and label-free high-content phenotypes, for rapid pooled CRISPR screening within vast cell populations. Using the high-content cell sorter operating in fluorescence mode, we successfully executed kinase-specific CRISPR screening targeting genes influencing the nuclear translocation of RelA. Furthermore, using the multiparametric, label-free mode, we performed large-scale screening to identify genes involved in macrophage polarization. Notably, the label-free platform can enrich target phenotypes without requiring invasive staining, preserving untouched cells for downstream assays and expanding the potential for screening cellular phenotypes even when suitable markers are absent.

Feline Adult Adipose Tissue-Derived Multipotent Stromal Cell Isolation and Differentiation.

Cats are among the most popular household pets. However, compared to other species, there is little information specific to feline adult mesenchymal stromal/stem cells. Despite the phylogenetic distance between domesticated cats, Felis silvestris catus, and humans, they share some similar health challenges like kidney disease, asthma, and diabetes. Investigative efforts have been focused on adult adipose-derived stromal/stem cell (ASC) therapies to address feline illnesses, including de novo pancreatic tissue generation for diabetes treatment. Given the relatively small size of domestic cats, optimized cell isolation from small quantities of adipose tissue is important in the development of feline ASC-based therapies. Additionally, there are unique features of feline ASC culture conditions and characterization. This chapter contains a few of the novel aspects of feline ASC isolation, culture, preservation, and differentiation.