Electric field-induced cell-to-cell fusion

Fundamentals of System Design for Cardiac Pulsed Field Ablation: Optimization of Safety, Efficacy, and Usability

The goal of a cardiac pulsed field ablation (PFA) system is to provide safe, effective, and usable therapy for the treatment of cardiac arrhythmias. Achieving this goal is a complex exercise in system design, requiring optimization of catheter, waveform, and dosing. This optimization is often iterative, as myriad design factors are balanced to achieve the goal while making use of computational modeling, bench testing, preclinical animal studies, and human clinical studies to evaluate system performance. It is important for both engineers and clinicians to understand the fundamentals of cardiac PFA system design in order to partner to continuously improve performance of this expanding ablation modality.

Novel electroporation microchip with field constriction enhances transfection efficiency and survival rates of feline embryos

This study introduces a low-voltage electroporation microchip designed for transfection in cat embryos, featuring real-time impedance monitoring. The microchip uses a field constriction strategy, which localises the electric field to the membrane region in contact with the micro-orifice, enhancing electroporation efficiency while minimising damage. Embryos were positioned on the orifice, and a series of voltage pulses (10, 15, and 20 V) were applied. Electroporation efficacy was assessed using fluorescent dyes, followed by real-time impedance measurements to monitor the membrane resealing time. It provided valuable insights into membrane recovery times, essential for optimizing gene editing conditions to ensure efficient delivery and maintain cell integrity. The results demonstrated that the microchip with 15 V achieved a 69.5% higher electroporation rate and 100% of survival compared to conventional devices (p < 0.05). Additionally, the microchip successfully facilitated the transfer of green fluorescent protein genes into embryos, achieving a 78.5% success rate significantly greater compared to 53.6% with the conventional device (p < 0.05). This innovative microchip provides transformative transfection technology for safer and more efficient genomic modifications in embryos. It holds promising applications across species and therapeutic interventions, paving the way for future studies in advanced genomic research.

Optical tweezer-assisted cell pairing and fusion for somatic cell nuclear transfer within an open microchannel

Somatic cell nuclear transfer (SCNT), referred to as somatic cell cloning, is a pivotal biotechnological technique utilized across various applications. Although robotic SCNT is currently available, the subsequent oocyte electrical activation/reconstructed embryo electrofusion is still manually completed by skilled operators, presenting challenges in efficient manipulation due to the uncontrollable positioning of the reconstructed embryo. This study introduces a robotic SCNT-electrofusion system to enable high-precision batch SCNT cloning. The proposed system integrates optical tweezers and microfluidic technologies. An optical tweezer is employed to facilitate somatic cells in precisely reaching the fusion site, and a specific polydimethylsiloxane (PDMS) chip is designed to assist in positioning and pairing oocytes and somatic cells. Enhancement in the electric field distribution between two parallel electrodes by PDMS pillars significantly reduces the required external voltage for electrofusion/electrical activation. We employed porcine oocytes and porcine fetal fibroblasts for SCNT experiments. The experimental results show that 90.56% of oocytes successfully paired with somatic cells to form reconstructed embryos, 76.43% of the reconstructed embryos successfully fused, and 70.55% of these embryos underwent cleavage. It demonstrates that the present system achieves the robotic implementation of oocyte electrical activation/reconstructed embryo electrofusion. By leveraging the advantages of batch operations using microfluidics, it proposes an innovative robotic cloning procedure that scales embryo cloning.

Developing Advanced Chimeric Cell Therapy for Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a lethal, X-linked disorder leading to muscle degeneration and premature death due to cardiopulmonary complications. Currently, there is no cure for DMD. We previously confirmed the efficacy of human Dystrophin-Expressing Chimeric (DEC) cells created via the fusion of myoblasts from normal and DMD-affected donors. The current study aimed to optimize the development of DEC therapy via the polyethylene glycol (PEG)-mediated fusion protocol of human myoblasts derived from normal, unrelated donors. The optimization of cell fusion assessed different factors influencing fusion efficacy, including myoblast passage number, the efficacy of PKH myoblast staining, the ratio of the single-stained myoblasts in the MIX, and PEG administration time. Additionally, the effect of PEG fusion procedure on cell viability was assessed. A correlation was found between the number of cells used for PKH staining and staining efficacy. Furthermore, the ratio of single-stained myoblasts in the MIX and PEG administration time correlated with fusion efficacy. There was no correlation found between the myoblast passage number and fusion efficacy. This study successfully optimized the myoblast fusion protocol for creation of human DEC cells, introducing DEC as a new Advanced Therapy Medicinal Product (ATMP) for DMD patients.

Enhancement of polyethylene glycol-cell fusion efficiency by novel application of transient pressure using a jet injector

Cell-cell fusion involves the fusion of somatic cells into a single hybrid cell. It is not only a physiological process but also an important cell engineering technology which can be applied to various fields, such as regenerative medicine, antibody engineering, genetic engineering, and cancer therapy. There are three major methods of cell fusion: electrical cell fusion, polyethylene glycol (PEG) cell fusion, and virus-mediated cell fusion. Although PEG cell fusion is the most economical approach and does not require expensive instrumentation, it has a poor fusion rate and induces a high rate of cell cytotoxicity. To improve the fusion rate of the PEG method, we combined it with the pyro-drive jet injector (PJI). PJI provides instant pressure instead of cell agitation to increase the probability of cell-to-cell contact and shorten the distance between cells in the process of cell fusion. Here, we report that this improved fusion method not only decreased cell cytotoxicity during the fusion process, but also increased fusion rate compared with the conventional PEG method. Furthermore, we tested the functionality of cells fused using the PJI-PEG method and found them to be comparable to those fused using the conventional PEG method in terms of their application for dendritic cell (DC)-tumor cell fusion vaccine production; in addition, the PJI-PEG method demonstrated excellent performance in hybridoma cell preparation. Taken together, our data indicate that this method improves cell fusion efficiency as compared to the PEG method and thus has the potential for use in various applications that require cell fusion technology.

Using a modified piggyBac transposon-combined Cre/loxP system to produce selectable reporter-free transgenic bovine mammary epithelial cells for somatic cell nuclear transfer

Transposon systems are widely used for genetic engineering in various model organisms. PiggyBac (PB) has recently been confirmed to have highly efficient transposition in the mouse germ line and mammalian cell lines. In this study, we used a modified PB transposon system mediated by PB transposase (PBase) mRNA carrying the human lactoferrin gene driven by bovine β-casein promoter to transfect bovine mammary epithelial cells (BMECs), and the selectable reporter in two stable transgenic BMEC clones was removed using cell-permeant Cre recombinase. These reporter-free transgenic BMECs were used as donor cells for somatic cell nuclear transfer (SCNT) and exhibited a competence of SCNT embryos similar to stable transgenic BMECs and nontransgenic BMECs. The comprehensive information from this study provided a modified approach using an altered PB transposon system mediated by PBase mRNA in vitro and combined with the Cre/loxP system to produce transgenic and selectable reporter-free donor nuclei for SCNT. Consequently, the production of safe bovine mammary bioreactors can be promoted.

Manipulation of coacervate droplets with an electric field

Many biopolymers are highly charged, and as in the case of many polymer mixtures, they tend to phase separate as a natural consequence of chain connectivity and an associated relatively low entropy of polymer mixing. Recently, it has become appreciated that the phase-separated structures formed by such polyelectrolyte blends, called "complex coacervates," underlie numerous biological structures and processes essential to living systems, and there has been intense interest in understanding the unique physical features of this type of phase-separation process. In the present work, we are particularly concerned with the field responsiveness of stabilized coacervate droplets formed after the phase separation of polyelectrolyte blend solution and then exposed to deionized water, making the droplet interfacial layer acquire a viscoelastic character that strongly stabilizes it against coalescence. We show that we can precisely control the positions of individual droplets and arrays of them with relatively low-voltage electric fields (on the order of 10 V/cm) and that the imposition of an oscillatory field gives rise to chain formation with coarsening of these chains into long fibers. Such a phase-separation-like process is generally observed in electrorheological fluids of solid colloidal particles subjected to much larger field strengths. The key to these coacervates' electrorheological properties is the altered interfacial viscoelastic properties when the droplets are introduced into deionized water and the associated high polarizability of the droplets, similar to the properties of many living cells. Since many different molecular payloads can be incorporated into these stable droplets, we anticipate many applications.

Electric-field facilitated rapid and efficient dissociation of tissues Into viable single cells

Single-Cell Analysis is a growing field that endeavors to obtain genetic profiles of individual cells. Disruption of cell-cell junctions and digestion of extracellular matrix in tissues requires tissue-specific mechanical and chemical dissociation protocols. Here, a new approach for dissociating tissues into constituent cells is described. Placing a tissue biopsy core within a liquid-filled cavity and applying an electric field between two parallel plate electrodes facilitates rapid dissociation of complex tissues into single cells. Different solution compositions, electric field strengths, and oscillation frequencies are investigated experimentally and with COMSOL Multiphysics. The method is compared with standard chemical and mechanical approaches for tissue dissociation. Treatment of tissue samples at 100 V/cm 1 kHz facilitated dissociation of 95 ± 4% of biopsy tissue sections in as little as 5 min, threefold faster than conventional chemical-mechanical techniques. The approach affords good dissociation of tissues into single cells while preserving cell viability, morphology, and cell cycle progression, suggesting utility for sample preparation of tissue specimens for direct Single-Cell Analysis.

Effects of Trichostatin A on the Timing of the First Cleavage and In Vitro Developmental Potential of Bovine Somatic Cell Nuclear Transfer Embryos

This study examined the relationship between the timing of the first cleavage and in vitro development of bovine somatic cell nuclear transfer (SCNT) embryos treated with trichostatin A (TSA). SCNT embryos were visually assessed at 22, 26, and 48 hours after activation. Each embryo with two or more distinct blastomeres was transferred into a microwell and cultured until day 7. Irrespective of TSA treatment, approximately half of the cleaved embryos were observed at 22 hours, and a significantly higher blastocyst formation rate was shown in the SCNT embryos cleaved at 22 hours than those cleaved at ≥26 hours. The blastocyst formation rate of TSA-treated embryos cleaved at 22 hours (80%) was slightly higher than that of the control embryos (70%). In addition, interferon-τ (IFN-τ) expression was significantly lower in control SCNT embryos and late-cleaving (>26 hours) TSA-treated embryos than in in vitro fertilized (IVF) embryos. However, a significant difference was not observed between TSA-treated SCNT embryos cleaved at 22 and 26 hours, and IVF embryos. These results suggest that TSA treatment has no influence on the timing of the first cleavage of SCNT embryos; however, it slightly improves the blastocyst formation rate and the expression level of IFN-τ in early-cleaving embryos.

Formation of Large Intracellular Actin Networks Following Plasmonic Cell Fusion

Following fusion between two or more individual cells, the resulting cellular entity must undergo extensive restructuring of its plasma membrane and cytoskeleton in order to maintain its mechanical and physiological function. In artificial cell fusion that is executed by external triggering, such restructuring could be problematic due to the absence of preconditioning biological signals. In this work we study the reorganization of the actin filaments in adenocarcinoma cells that were fused using plasmonic triggering, i.e. the irradiation by resonant femtosecond laser pulses of cells specifically targeted by gold nanoparticles. Time-lapse confocal microscopy of the fusing cells has revealed the formation of large-scale actin networks that preserve the local orientations of the original actin cytoskeletons. The results confirm the local nature of the plasmonic interactions that were confined to the cells' plasma membranes and would help studying the development and dynamics of actin networks by offering a relatively stable, living cellular environment that supports large-scale actin growth.

Conformation-specific monoclonal antibodies recognizing the native structure of G protein-coupled receptor (GPCR)

It is quite difficult to generate monoclonal antibodies that recognize the three-dimensional structures of the antigens of interest. To address this limitation, we developed a new hybridoma technology termed "optimized stereospecific targeting (SST)". Here we aimed at generating stereospecific monoclonal antibodies against a G protein-coupled receptor (GPCR). The optimized SST technique enabled the efficient production of conformation-specific monoclonal antibodies against human corticotropin-releasing hormone receptor 1 (huCRHR1). Hybridoma cells secreting stereospecific monoclonal antibodies were selectively cloned by a limiting dilution method and the target monoclonal antibodies were purified by protein A column chromatography. They specifically cross-reacted with native huCRHR1 expressed on the surface of CHO cells, whereas they showed no affinity for MDA-MB-231 cancer cells, which abundantly express EphA2 on the cell surface. Furthermore, immunofluorescence analysis revealed that treatment of huCRHR1-expressing CHO cells with 4% paraformaldehyde led to a decrease in the affinity of purified monoclonal antibodies for intact huCRHR1 on the cell surface. In addition, purified monoclonal antibodies showed no cross-reactivity with huCRHR1 expressed on Sf9 insect cells. These results strongly suggest that monoclonal antibodies generated by the optimized SST technique feature specific binding to the intact form of the target GPCR on mammalian cells.

Electrohydrodynamics of Vesicles and Capsules

Giant unilamellar vesicles (GUVs) made up of phospholipid bilayer membranes (liposomes) and elastic capsules with a cross-linked, polymerized membrane, have emerged as biomimetic alternatives to investigating biological cells such as leukocytes and erythrocytes. This feature article looks at the similarities and differences in the electrohydrodynamics (EHD) of vesicles and capsules under electric fields that determines their electromechanical response. The physics of EHD is illustrated through several examples such as the electrodeformation of single and compound, spherical and cylindrical, and charged and uncharged vesicles in uniform and nonuniform electric fields, and the relevance and challenges are discussed. Both small and large deformation results are discussed. The use of EHD in understanding complex interfacial kinetics in capsules and the synthesis of nonspherical capsules using electric fields are also presented. Finally, the review looks at the large electrodeformation of water-in-water capsules and the relevance of constitutive laws in their response.

Tools for the Genetic Manipulation of Herpetomonas muscarum

Trypanosomatid parasites are causative agents of important human and animal diseases such as sleeping sickness and leishmaniasis. Most trypanosomatids are transmitted to their mammalian hosts by insects, often belonging to Diptera (or true flies). With resistance to both vector-targeted pesticides and trypanocidal drugs being reported, there is a need for novel transmission blocking strategies to be developed. Studies using the blood-feeding vectors themselves are not broadly accessible, as such, new model systems are being developed to unpick insect-trypanosmatids interactions. One such case is the interactions between the model dipteran Dr osophila melanogaster and its natural trypanosomatid Herpetomonas muscarum Our previous work has found that much of the transcriptomic changes triggered in H. muscarum after ingestion by Drosophila reflect what is known for disease-causing trypanosomatids. Here we describe a set of tools to genetically manipulate the parasite and therefore create a truly tractable insect-parasite interaction system from both sides of this association. These include transgenic fluorescently tagged parasites to follow infection dynamics in the fly gut as well as iterations of plasmids that can be used for generating knock-in and knock-out strains. The tools presented in this short report will facilitate further characterization of trypanosomatid establishment in a model dipteran.

Timing of the First Cleavage and In Vitro Developmental Potential of Bovine Somatic Cell Nuclear Transfer Embryos Activated by Different Protocols

The objective of this study was to examine the relationship between the timing of the first cleavage and in vitro development of somatic cell nuclear transfer (SCNT) embryos produced by different activation protocols. SCNT embryos were activated with calcium ionophore A23187 and further treated with 6-dimethylaminopurine (DMAP group), cycloheximide (CHX group), or anisomycin (ANI group). The proportion of SCNT embryos that cleaved within 18 hours after activation was significantly higher in the DMAP group (20%) than that in the CHX and ANI groups (3% and 2%, respectively). More than 70% of the cleaved embryos were observed within 24 hours in the DMAP and CHX groups, and within 26 hours in the ANI group. The blastocyst formation rate of SCNT embryos decreased gradually as the time from activation to the first cleavage increased in the DMAP group. The blastocyst formation rate of SCNT embryos cleaved at 22 hours (>20 to ≤22 hours) in the CHX group or within 26 hours in the ANI group was significantly higher than that of SCNT embryos cleaved more than 26 hours in each group. These results indicate that the activation protocol affects the timing of the first cleavage and subsequent in vitro development potential of bovine SCNT embryos and that late-cleaving embryos have a low developmental potential irrespective of the activation protocol.

Comparative study of the developmental competence of cloned pig embryos derived from spermatogonial stem cells and fetal fibroblasts

Spermatogonial stem cells (SSC) are promising resources for genetic preservation and restoration of male germ cells in humans and animals. However, no studies have used SSC as donor nuclei in pig somatic cell nuclear transfer (SCNT). This study investigated the potential for use of porcine SSC as a nuclei donor for SCNT and developmental competence of SSC-derived cloned embryos. In addition, demecolcine was investigated to determine whether it could prevent rupture of SSC during SCNT. When the potential of SSC to support embryonic development after SCNT was compared with that of foetal fibroblasts (FF), SSC-derived SCNT embryos showed a higher (p < .05) developmental competence to the blastocyst stage (47.8%) than FF-derived embryos (25.6%). However, when SSC were used as donor nuclei in the SCNT process, cell fusion rates were lower (p < .05) than when FF were used (61.9% vs. 75.8%). Treatment of SSC with demecolcine significantly (p < .05) decreased rupture of SSC during the SCNT procedure (7.5% vs. 18.8%) and increased fusion of cell-oocyte couplets compared with no treatment (74.6% vs. 61.6%). In addition, SSC-derived SCNT embryos showed higher blastocyst formation (48.4%) than FF-derived embryos without (28.4%) and with demecolcine treatment (17.4%), even after demecolcine treatment. Our results demonstrate that porcine SSC are a desirable donor cell type for production of SCNT pig embryos and that demecolcine increases production efficiency of cloned embryos by inhibiting rupture of nuclei donor SSC during SCNT.

Dielectrophoretic deformation of breast cancer cells for lab on a chip applications

This paper presents the development and experimental analysis of a curved microelectrode platform for the DEP deformation of breast cancer cells (MDA-MB-231). The platform is composed of arrays of curved DEP microelectrodes which are patterned onto a glass slide and samples containing MDA-MB-231 cells are pipetted onto the platform's surface. Finite element method is utilised to characterise the electric field gradient and DEP field. The performance of the system is assessed with MDA-MB-231 cells in a low conductivity 1% DMEM suspending medium. We applied sinusoidal wave AC potential at peak to peak voltages of 2, 5, and 10 V_pp at both 10 kHz and 50 MHz. We observed cell blebbing and cell shrinkage and analyzed the percentage of shrinkage of the cells. The experiments demonstrated higher percentage of cell shrinkage when cells are exposed to higher frequency and peak to peak voltage electric field.

Nuclear transplantation between allogeneic cells through topological reconnection of plasma membrane in a microfluidic system

Previous studies have demonstrated that somatic cells fused with pluripotent stem cells can be reprogrammed on the basis of reprogramming factors acquired from the latter. However, fusion-reprogrammed cells are deemed unsuitable for therapeutic applications mainly because conventional fusion techniques often yield tetraploid fusants that contain exogenous genes acquired from the fusion partners. Here, we present a novel cell-cell topological reconnection technique and demonstrate its application to nuclear transplantation between a somatic cell and a stem cell without nuclei mixing. As a proof of concept, a microfluidic fusion chip embodied with a microslit (4 μm in width) to prevent nuclei mixing was developed and used to perform one-to-one electrofusion of a target somatic cell (Jurkat cell) with an induced pluripotent stem (iPS) cell. To extract its cytoplasm, the target cell was first topologically connected to a sacrificial iPS cell by electrofusion via a microslit, followed by shear flow removal of the latter to obtain a cytoplasm-depleted nucleus of the target cell. Then, to replace the lost cytoplasm, topological reconnection to a second iPS cell was performed similarly by electrofusion, followed by shear flow separation of the target cell to enable it acquire most of the iPS cytoplasm, but without nuclei mixing. Microscopic observation of target cells harvested and cultured post hoc in a microwell confirmed that they manifested cell division. Taken together, these results demonstrate the potential application of the cell-cell topological reconnection technique to somatic cell nuclear transplantation for the generation of autologous pluripotent stem cells.

Electric field-responsive nanoparticles and electric fields: physical, chemical, biological mechanisms and therapeutic prospects

Electric fields are among physical stimuli that have revolutionized therapy. Occurring endogenously or exogenously, the electric field can be used as a trigger for controlled drug release from electroresponsive drug delivery systems, can stimulate wound healing and cell proliferation, may enhance endocytosis or guide stem cell differentiation. Electric field pulses may be applied to induce cell fusion, can increase the penetration of therapeutic agents into cells, or can be applied as a standalone therapy to ablate tumors. This review describes the main therapeutic trends and overviews the main physical, chemical and biological mechanisms underlying the actions of electric fields. Overall, the electric field can be used in therapeutic approaches in several ways. The electric field can act on drug carriers, cells and tissues. Understanding the multiple effects of this powerful tool will help harnessing its full therapeutic potential in an efficient and safe way.

A potential mechanism for first-person internal sensation of memory provides evidence for the relationship between learning and LTP induction

Studies conducted to verify learning-induced changes anticipated from Hebb's postulate led to the finding of long-term potentiation (LTP). Even though several correlations have been found between behavioural markers of memory retrieval and LTP, it is not known how memories are retrieved using learning-induced changes. In this context, the following non-correlated findings between learning and LTP induction provide constraints for discovering the mechanism: 1) Requirement of high stimulus intensity for LTP induction in contrast to what is expected for a learning mechanism, 2) Delay of at least 20 to 30 s from stimulation to LTP induction, in contrast to mere milliseconds for associative learning, and 3) A sudden drop in peak-potentiated effect (short-term potentiation) that matches with short-lasting changes expected during working memory and occurs only at the time of delayed LTP induction. When memories are viewed as first-person internal sensations, a newly uncovered mechanism provides explanation for the relationship between memory and LTP. This work interconnects large number of findings from the fields of neuroscience and psychology and provides a further verifiable mechanism of learning.

Comparison of Bipolar and Unipolar Pulses in Cell Electrofusion: Simulation and Experimental Research

OBJECTIVE

Unipolar pulses have been used in cell electrofusion over the last decades. However, the problem of high mortality with unipolar pulses has not been solved effectively. The cell fusion rate is restricted by cell mortality. By using the advantages of bipolar pulses which cause less cell damage, this paper attempts to use bipolar pulses to increase the cell fusion rate.

METHODS

the transmembrane voltage and pore density of cells subjected to unipolar/bipolar pulses were simulated in COMSOL software. In an experiment, two 40 μs unipolar and two 20-20 μs bipolar pulses with electric fields of 2, 2.5, and 3 kV/cm were applied to SP2/0 murine myeloma cells. To determine the cell fusion rate and cell mortality, cells were stained with Hoechst 33342 and propidium iodide.

RESULTS

the simulation in this paper showed that a high transmembrane voltage and a high pores density were concentrated only at the contact area of cells when bipolar pulses were used. The results of the cell staining experiment verified the simulation analysis. When bipolar pulses were applied, the cell mortality was significantly reduced. In addition, the cell fusion rate with bipolar pulses was almost two times higher than that with unipolar pulses.

CONCLUSION

for cell electrofusion, compared with unipolar pulses, bipolar pulses can not only reduce the cell mortality remarkably but also improve the cell fusion rate obviously.

SIGNIFICANCE

this paper introduces a novel way to increase the fusion rate of cells.

Synthesis, biophysical and functional studies of two BP100 analogues modified by a hydrophobic chain and a cyclic peptide

Antimicrobial peptides (AMPs) work as a primary defense against pathogenic microorganisms. BP100, (KKLFKKILKYL-NH₂), a rationally designed short, highly cationic AMP, acts against many bacteria, displaying low toxicity to eukaryotic cells. Previously we found that its mechanism of action depends on membrane surface charge and on peptide-to-lipid ratio. Here we present the synthesis of two BP100 analogs: BP100‑alanyl‑hexadecyl‑1‑amine (BP100-Ala-NH-C₁₆H₃₃) and cyclo(1‑4)‑d‑Cys¹, Ile², Leu³, Cys⁴-BP100 (Cyclo(1‑4)‑cILC-BP100). We examined their binding to large unilamellar vesicles (LUV), conformational and functional properties, and compared with those of BP100. The analogs bound to membranes with higher affinity and a lesser dependence on electrostatic forces than BP100. In the presence of LUV, BP100 and BP100-Ala-NH-C₁₆H₃₃ acquired α-helical conformation, while Cyclo(1‑4)‑cILC-BP100) was partly α-helical and partly β-turn. Taking in conjunction: 1. particle sizes and zeta potential, 2. effects on lipid flip-flop, 3. leakage of LUVs internal contents, and 4. optical microscopy of giant unilamellar vesicles, we concluded that at high concentrations, all three peptides acted by a carpet mechanism, while at low concentrations the peptides acted by disorganizing the lipid bilayer, probably causing membrane thinning. The higher activity and lesser membrane surface charge dependence of the analogs was probably due to their greater hydrophobicity. The MIC values of both analogs towards Gram-positive and Gram-negative bacteria were similar to those of BP100 but both analogues were more hemolytic. Confocal microscopy showed Gram-positive B. subtilis killing with concomitant extensive membrane damage suggestive of lipid clustering, or peptide-lipid aggregation. These results were in agreement with those found in model membranes.

Additional mitochondrial DNA influences the interactions between the nuclear and mitochondrial genomes in a bovine embryo model of nuclear transfer

We generated cattle embryos using mitochondrial supplementation and somatic cell nuclear transfer (SCNT), named miNT, to determine how additional mitochondrial DNA (mtDNA) modulates the nuclear genome. To eliminate any confounding effects from somatic cell mtDNA in intraspecies SCNT, donor cell mtDNA was depleted prior to embryo production. Additional oocyte mtDNA did not affect embryo development rates but increased mtDNA copy number in blastocyst stage embryos. Moreover, miNT-derived blastocysts had different gene expression profiles when compared with SCNT-derived blastocysts. Additional mtDNA increased expression levels of genes involved in oxidative phosphorylation, cell cycle and DNA repair. Supplementing the embryo culture media with a histone deacetylase inhibitor, Trichostatin A (TSA), had no beneficial effects on the development of miNT-derived embryos, unlike SCNT-derived embryos. When compared with SCNT-derived blastocysts cultured in the presence of TSA, additional mtDNA alone had beneficial effects as the activity of glycolysis may increase and embryonic cell death may decrease. However, these beneficial effects were not found with additional mtDNA and TSA together, suggesting that additional mtDNA alone enhances reprogramming. In conclusion, additional mtDNA increased mtDNA copy number and expression levels of genes involved in energy production and embryo development in blastocyst stage embryos emphasising the importance of nuclear-mitochondrial interactions.

Cell pairing and polyethylene glycol (PEG)-mediated cell fusion using two-step centrifugation-assisted single-cell trapping (CAScT)

Here a convenient and effective strategy of two-step centrifugation-assisted single-cell trapping (CAScT) based on an addressable truncated cone-shaped microwell array (TCMA) chip is developed for cell pairing. We describe the operation principles of the method and demonstrate its compatibility with polyethylene glycol (PEG)-mediated cell fusion. Compared with other methods, most of which rely on sophisticated devices and bulky subsidiary equipment, our method is more convenient and exhibits better or comparable performance. Using this method, up to around 6000 heterotypic cell pairs can be formed and addressed within a small area of 1 cm2. The paired cells are then treated with fusogenic PEG for cell fusion. Compared with traditional protocols, cell fusion using this approach is well defined with better control, which leads to an improved yield of heterotypic binucleated hybrids. Furthermore, we demonstrate the capability of our device for long-term cell culture and cell harvesting.

Liposome-encapsulated diacyl glycerol and inositol triphosphate-induced delayed oocyte activation and poor development of parthenotes

Objective:

To explore the ability of diacyl glycerol (DAG) and inositol triphosphate (IP3), two major secondary messengers in the calcium signaling pathway, in activating oocytes.

Material and Methods:

Oocyte cumulus complex obtained from superovulated Swiss albino mice were incubated in M16 medium with liposome-encapsulated 1,2-Dipalmitoyl-sn-glycerol (LEDAG) and/or IP3 for 3 h. Strontium chloride was used as positive control. The activation potential, ploidy status, and blastocyst rate was calculated.

Results:

Both DAG and IP3, individually, induced activation in ~98% of oocytes, which was significantly higher (p<0.01) than activation induced by strontium chloride (60%). Delayed pronucleus formation and a higher percentage of diploid parthenotes was observed in oocytes activated with LEDAG and/or IP3. However, these embryos failed to progress beyond the 6-8–cell stage. Only when the medium was supplemented with LEDAG (5 μg/mL) and IP3 (10 μg/mL) could activated oocytes progress till the blastocyst stage (5.26%), which was lower than the blastocyst rate in the positive controls (13.91%).

Conclusion:

The results of the present study indicate that DAG and IP3 can induce delayed oocyte activation and poor development of parthenotes in vitro.

Manipulating the Mitochondrial Genome To Enhance Cattle Embryo Development

The mixing of mitochondrial DNA (mtDNA) from the donor cell and the recipient oocyte in embryos and offspring derived from somatic cell nuclear transfer (SCNT) compromises genetic integrity and affects embryo development. We set out to generate SCNT embryos that inherited their mtDNA from the recipient oocyte only, as is the case following natural conception. While SCNT blastocysts produced from Holstein (Bos taurus) fibroblasts were depleted of their mtDNA, and oocytes derived from Angus (Bos taurus) cattle possessed oocyte mtDNA only, the coexistence of donor cell and oocyte mtDNA resulted in blastocysts derived from nondepleted cells. Moreover, the use of the reprogramming agent, Trichostatin A (TSA), further improved the development of embryos derived from depleted cells. RNA-seq analysis highlighted 35 differentially expressed genes from the comparison between blastocysts generated from nondepleted cells and blastocysts from depleted cells, both in the presence of TSA. The only differences between these two sets of embryos were the presence of donor cell mtDNA, and a significantly higher mtDNA copy number for embryos derived from nondepleted cells. Furthermore, the use of TSA on embryos derived from depleted cells positively modulated the expression of CLDN8, TMEM38A, and FREM1, which affect embryonic development. In conclusion, SCNT embryos produced by mtDNA depleted donor cells have the same potential to develop to the blastocyst stage without the presumed damaging effect resulting from the mixture of donor and recipient mtDNA.

Time-dependent electrohydrodynamics of a compressible viscoelastic capsule in the small-deformation limit

A theoretical analysis of the time-dependent electrohydrodynamics of a viscoelastic compressible capsule, characterized by the two-dimensional Young's modulus and surface viscosity, is studied in the small-deformation limit. A systematic ac electrohydrodynamics analysis is conducted, and time-independent and time-periodic deformations are related to the electric capillary number and the membrane properties. Additionally, the relaxation of a capsule stretched by a dc electric field is also presented. This necessitates an accurate estimation of the initial strain field in the stretched capsule. Both an oscillatory analysis and an analysis of the relaxation of a stretched capsule are presented for a capsule containing an aqueous phase, modeled as a perfect conductor, and suspended in a perfect dielectric with an infinitesimally thin viscoelastic membrane separating the two. The membrane is assumed to be a perfect dielectric with no electrical contrast with the suspending fluid.

Effects of duration of electric pulse on in vitro development of cloned cat embryos with human artificial chromosome vector

The current applications for cat cloning include production of models for the study of human and animal diseases. This study was conducted to investigate the optimal fusion protocol on in vitro development of transgenic cloned cat embryos by comparing duration of electric pulse. Cat fibroblast cells containing a human artificial chromosome (HAC) vector were used as genetically modified nuclear donor cells. Couplets were fused and activated simultaneously with a single DC pulse of 3.0 kV/cm for either 30 or 60 μs. Low rates of fusion and embryo development to the blastocyst stage were observed in the reconstructed HAC-transchromosomic embryos, when the duration of fusion was prolonged to 60 μs. In contrast, the prolongation of electric pulse duration improved the embryo development and quality in the reconstructed control embryos without HAC vector. Our results suggested that the optimal parameters of electric pulses for fusion in cat somatic cell nuclear transfer vary among the types used for donor cells.

Optically-Induced Cell Fusion on Cell Pairing Microstructures

Cell fusion is a critical operation for numerous biomedical applications including cell reprogramming, hybridoma formation, cancer immunotherapy, and tissue regeneration. However, unstable cell contact and random cell pairings have limited efficiency and yields when utilizing traditional methods. Furthermore, it is challenging to selectively perform cell fusion within a group of cells. This study reports a new approach called optically-induced cell fusion (OICF), which integrates cell-pairing microstructures with an optically-induced, localized electrical field. By projecting light patterns onto a photoconductive film (hydrogen-rich, amorphous silicon) coated on an indium-tin-oxide (ITO) glass while an alternating current electrical field was applied between two such ITO glass slides, “virtual” electrodes could be generated that could selectively fuse pairing cells. At 10 kHz, a 57% cell paring rate and an 87% fusion efficiency were successfully achieved at a driving voltage of 20  V_pp, suggesting that this new technology could be promising for selective cell fusion within a group of cells.

Cell Electrofusion in Centrifuged Erythrocyte Pellets Assessed by Dielectric Spectroscopy

We have characterized cell electrofusion in cell pellets by dielectric spectroscopy. Cell pellets were formed from horse erythrocyte suspensions by centrifugation and were subjected to intense AC pulses. The dielectric spectra of the pellets were measured over a frequency range of 10 Hz to 10 MHz. The application of AC pulses caused low-frequency (LF) dielectric relaxation below about 100 kHz. The LF dielectric relaxation was markedly affected not only by pretreatment of cells at 50 °C, which disrupts the spectrin network of erythrocytes, but also by the parameters of the AC pulses (frequency of the sine wave and repeat count of the pulses). The occurrence of the LF dielectric relaxation was qualitatively accounted for by modeling fusion products in the pellet by prolate spheroidal cells whose long axes run parallel to the applied electric field.

Response of single cell with acute angle exposed to an external electric field

It is known that the electric field incurs effects on the living cells. Predicting the response of single cell or multilayer cells to induced alternative or static eclectic field has permanently been a challenge. In the present study a first order single cell with acute angle under the influence of external electric field is considered. The cell division stage or the special condition of reshaping is modelled with a cone being connected. In the case of cell divisions, anaphase, it can be considered with two cones that connected nose-to-nose. Each cone consists of two regions. The first is the membrane modelled with a superficial layer, and the second is cytoplasm at the core. A Laplace equation is written for this model and the distribution of its electric field is a sharp point in the single cell for which an acute angle model is calculated.

Tripolar mitosis in human cells and embryos: occurrence, pathophysiology and medical implications

Tripolar mitosis is a specific case of cell division driven by typical molecular mechanisms of mitosis, but resulting in three daughter cells instead of the usual count of two. Other variants of multipolar mitosis show even more mitotic poles and are relatively rare. In nature, this phenomenon was frequently observed or suspected in multiple common cancers, infected cells, the placenta, and in early human embryos with impaired pregnancy-yielding potential. Artificial causes include radiation and various toxins. Here we combine several pieces of the most recent evidence for the existence of different types of multipolar mitosis in preimplantation embryos together with a detailed review of the literature. The related molecular and cellular mechanisms are discussed, including the regulation of centriole duplication, mitotic spindle biology, centromere functions, cell cycle checkpoints, mitotic autocorrection mechanisms, and the related complicating factors in healthy and affected cells, including post-mitotic cell-cell fusion often associated with multipolar cell division. Clinical relevance for oncology and embryo selection in assisted reproduction is also briefly discussed in this context.

Controllable electrofusion of lipid vesicles: initiation and analysis of reactions within biomimetic containers

We present a microfluidic device that is able to trap multiple giant unilamellar vesicles (GUVs) and initiate electrofusion via integrated microelectrodes. PDMS posts were designed to trap and isolate two or more vesicles. Electrodes patterned onto the glass surface of the microchannels are able to apply a short, high voltage pulse across the traps for controllable electrofusion of the GUVs. The entire array of traps and electrodes are designed such that an average of 60 individual fusion experiments can be performed on-chip. An assay based on Förster resonance energy transfer (FRET) is performed to show successful lipid mixing. Not only can the device be used to record the dynamics of lipid membrane fusion, but it can be used for reaction monitoring by fusing GUVs containing reactants. We demonstrate this by fusing vesicles encapsulating femtolitre volumes of cobalt chloride or EDTA and monitoring the amount of the complexation product over time.

Cell pairing using microwell array electrodes based on dielectrophoresis

We report a simple device with an array of 10,000 (100 × 100) microwells for producing vertical pairs of cells in individual microwells with a rapid manipulation based on positive dielectrophoresis (p-DEP). The areas encircled with micropoles which fabricated from an electrical insulating photosensitive polymer were used as microwells. The width (14 μm) and depth (25 μm) of the individual microwells restricted the size to two vertically aligned cells. The DEP device for the manipulation of cells consisted of a microfluidic channel with an upper indium tin oxide (ITO) electrode and a lower microwell array electrode fabricated on an ITO substrate. Mouse myeloma cells stained in green were trapped within 1 s in the microwells by p-DEP by applying an alternating current voltage between the upper ITO and the lower microwell array electrode. The cells were retained inside the wells even after switching off the voltage and washing with a fluidic flow. Other myeloma cells stained in blue were then trapped in the microwells occupied by the cells stained in green to form the vertical cell pairing in the microwells. Cells stained in different colors were paired within only 1 min and a pairing efficiency of over 50% was achieved.

Effects of trichostatin A on In vitro development and DNA methylation level of the satellite I region of swamp buffalo (Bubalus bubalis) cloned embryos

Trichostatin A (TSA), a histone deacetylase inhibitor, has been widely used to improve the cloning efficiency in several species. This brings our attention to investigation of the effects of TSA on developmental potential of swamp buffalo cloned embryos. Swamp buffalo cloned embryos were produced by electrical pulse fusion of male swamp buffalo fibroblasts with swamp buffalo enucleated oocytes. After fusion, reconstructed oocytes were treated with 0, 25 or 50 nM TSA for 10 h. The results showed that there was no significant difference in the rates of fusion (82–85%), cleavage (79–84%) and development to the 8-cell stage (59–65%) among treatment groups. The highest developmental rates to the morula and blastocyst stages of embryos were found in the 25 nM TSA-treated group (42.7 and 30.1%, respectively). We also analyzed the DNA methylation level in the satellite I region of donor cells and in in vitro fertilized (IVF) and cloned embryos using the bisulfite DNA sequencing method. The results indicated that the DNA methylation levels in cloned embryos were significantly higher than those of IVF embryos but approximately similar to those of donor cells. Moreover, there was no significant difference in the methylation level among TSA-treated and untreated cloned embryos. Thus, TSA treatments at 25 nM for 10 h could enhance the in vitro developmental potential of swamp buffalo cloned embryos, but no beneficial effect on the DNA methylation level was observed.

Comparison of in vitro developmental competence of cloned caprine embryos using donor karyoplasts from adult bone marrow mesenchymal stem cells vs ear fibroblast cells

The aim of this study was to produce cloned caprine embryos using either caprine bone marrow-derived mesenchymal stem cells (MSCs) or ear fibroblast cells (EFCs) as donor karyoplasts. Caprine MSCs were isolated from male Boer goats of an average age of 1.5 years. To determine the pluripotency of MSCs, the cells were induced to differentiate into osteocytes, chondrocytes and adipocytes. Subsequently, MSCs were characterized through cell surface antigen profiles using specific markers, prior to their use as donor karyoplasts for nuclear transfer. No significant difference (p > 0.05) in fusion rates was observed between MSCs (87.7%) and EFCs (91.3%) used as donor karyoplasts. The cleavage rate of cloned embryos derived with MSCs (87.0%) was similar (p > 0.05) to those cloned using EFCs (84.4%). However, the in vitro development of MSCs-derived cloned embryos (25.3%) to the blastocyst stage was significantly higher (p < 0.05) than those derived with EFCs (20.6%). In conclusion, MSCs could be reprogrammed by caprine oocytes, and production of cloned caprine embryos with MSCs improved their in vitro developmental competence, but not in their fusion and cleavage rate as compared to cloning using somatic cells such as EFCs.

Intraspecific hybridization between Coprinus cinereus and Schizophyllum commune by PEG-induced protoplast fusion and electrofusion

Two irreversible inhibitors, iodoacetamide and diethylpyrocarbonate, were used to select intraspecific fusion products of two mushroom species, Coprinus cinereus and Schizophyllum commune. Iodoacetamide was the more suitable inhibitor because it gave a low breakage frequency and low survival rate of the cells in the inactivation experiments. Fusion-induced by polyethylene glycol and electro-fusion were compared and, under optimal conditions, gave fusion frequencies of 16.7% to 50.0% and 6.9% to 8.4%, respectively. All fusion progeny were heterokaryons (dikaryons) and had clamp connections. There were no differences in the morphology and fruiting ability of the fusion progeny and those of the heterokaryons generated from mating.

Specific activation requirements of zona-free sheep oocytes before and after somatic cell nuclear transfer

In this study, the effect of the steps involved in zona-free somatic cell nuclear transfer (SCNT) on oocyte transcripts was investigated in sheep. To establish the reliable combined electrical-chemical activation for zona-free oocytes, oocytes were first exposed to an electrical pulse and then treated with 18 chemical activation regimens designed through modifying duration and concentration of ionomycin and 6-dimethyl aminopurine (6-DMAP), which is routinely used for SCNT. Electrofusion-mediated nuclear transfer significantly reduced transcript abundances of CCNB1, POU5F1, NPM2, GMMN, and CX43 compared to intact oocytes. Maximum parthenogenetic blastocyst development was obtained when oocytes were submitted to electric pulse and then to (1) 5 μM ionomycin for 5 or 2.5 min, both followed by 2 h of incubation with 6-DMAP (41.7±1.1, and 42.4±1.4%, respectively), (2) 5 μM ionomycin for 1 min+6-DMAP for 4 h (43.1±1.4%), and (3) 2.5 μM ionomycin for 1 min+6-DMAP for 2 h (42.4±1.4%), with significant differences compared to all the other groups. Statistical assessment of interactions between duration and concentration of ionomycin and duration of 6-DMAP exposure revealed that (1) concentration of ionomycin may be a more important factor than its duration, (2) both a long exposure period and a low concentration of ionomycin had marked decreasing effects on parthenogenetic development of zona-free oocytes, and (3) high duration of exposure to 6-DMAP can reduce parthenogenetic development. Despite an activation preference of parthenogenetic oocytes, a significantly higher rate of cloned blastocyst development was observed when reconstructed oocytes were activated with 5 μM ionomycin for 5 min rather than 2.5 μM ionomycin for 1 min (8.8±2.5 vs. 1.25±2.2%). These results suggested that SCNT steps have determining effects on oocyte transcripts and activation preferences of the reconstituted oocytes compared to intact counterparts. In this sense, reconstituted oocytes may need a higher concentration of ionomycin for a longer period than intact oocytes.

Production of fertile offspring from oocytes grown in vitro by nuclear transfer in cattle

Because of recent advancements in reproductive technology, oocytes have attained an increasingly enriched value as a unique cell population in the production of offspring. The growing oocytes in the ovary are an immediate potential source that serve this need; however, complete oocyte growth before use is crucial. Our research objective was to create in vitro-grown (IVG) oocytes that would have the ability to perform specialized activities, including nuclear reprogramming, as an alternative to in vivo-grown oocytes. Bovine oocyte-granulosa cell complexes with a mean oocyte diameter of approximately 100 μm were cultured on Millicell membrane inserts, with culture medium supplemented with 4% polyvinylpyrrolidone (molecular weight, 360,000), 20 ng/ml androstenedione, 2 mM hypoxanthine, and 5 ng/ml bone morphogenetic protein 7. Oocyte viability after the 14-day culture period was 95%, and there was a 71% increase in oocyte volume. Upon induction of oocyte maturation, 61% of the IVG oocytes extruded a polar body. Eighty-four percent of the reconstructed IVG oocytes that used cumulus cells as donor cells underwent cleavage, and half of them became blastocysts. DNA methylation analyses of the satellite I and II regions of the blastocysts revealed a similar highly methylated status in the cloned embryos derived from in vivo-grown and IVG oocytes. Finally, one of the nine embryos reconstructed from the IVG oocytes developed into a living calf following embryo transfer. Fertility of the offspring was confirmed. In conclusion, the potential of a proportion of the IVG oocytes was comparable to that of in vivo-grown oocytes.

Molecular dynamic simulation of transmembrane pore growth

A molecular dynamic approach was applied for simulation of dynamics of pore formation and growth in a phospholipid bilayer in the presence of an external electric field. Processing the simulation results permitted recovery of the kinetic coefficients used in the Einstein-Smoluchowski equation describing the dynamics of pore evolution. Two different models of the bilayer membrane were considered: membrane consisting of POPC and POPE lipids. The simulations permitted us to find nonempirical values of the pore energy parameters, which are compared with empirical values. It was found that the parameters are sensitive to membrane type.