Generating mammalian stable cell lines by electroporation

Advances in hybridoma preparation using electrofusion technology

As a rapidly developing cell engineering technique, cell electrofusion has been increasingly applied in the field of hybridoma preparation in recent years. However, it is difficult to completely replace the polyethylene glycol-mediated cell fusion using electrofusion due to the high operation requirements, high cost of electrofusion instruments, and lack of prior reference research work. The key elements limiting electrofusion in the field of hybridoma preparation also introduce practical complications, such as the use/choice of electrofusion instruments, setup/optimization of electrical parameters, and precise control of cells. This review summarizes the state of the art of cell electrofusion in hybridoma preparation based on recent published literature, mainly focusing on electrofusion instruments and their components, process control and characterization, and cell treatment. It also provides new information and insightful commentary critically important for further electrofusion development in the field of hybridoma preparation.

Selection of high-producing clones by a relative titer predictive model using image analysis

Background

The commercial success of monoclonal antibodies (Mabs) has made biological therapeutics attractive to pharmaceutical companies. The priority of biopharmaceutical companies is to acquire and develop cell lines that enable them to manufacture biologics quickly, consistently, and economically. Clone selection is a critical process for cell line development. However, the traditional clone selection process requires the evaluation of large numbers of clones using cell growth rate, cell densities and titer, product quality, and so on.

Methods

To improve efficiency of the clone selection strategies, we developed a relative titer (RT) prediction model by the quantitative information extracted from microscope images during the cell line development process. The performance of this RT prediction model was further evaluated with 50 clones from 5 different cell lines.

Results

The RT prediction model was able to predict high producers from a given data set when the same host cells were used. Although inaccurate prediction occurred when different host cell was used, this RT prediction model may serve as an excellent proof of concept study that quantitative information from cell line development images provides valuable information to facilitate the cell line development process.

Conclusions

Here, we present the first predictive model that can be used to estimate the relative productivity of Chinese hamster ovaries (CHO) clones during the cell line development. Additional experiments are currently in process to further improve the RT predictive model. Nevertheless, our current study will serve as a foundation for more prediction models for cell line development that can facilitate the selection of clones.

Microfluidic Based Physical Approaches towards Single-Cell Intracellular Delivery and Analysis

The ability to deliver foreign molecules into a single living cell with high transfection efficiency and high cell viability is of great interest in cell biology for applications in therapeutic development, diagnostics, and drug delivery towards personalized medicine. Various physical delivery methods have long demonstrated the ability to deliver cargo molecules directly to the cytoplasm or nucleus and the mechanisms underlying most of the approaches have been extensively investigated. However, most of these techniques are bulk approaches that are cell-specific and have low throughput delivery. In comparison to bulk measurements, single-cell measurement technologies can provide a better understanding of the interactions among molecules, organelles, cells, and the microenvironment, which can aid in the development of therapeutics and diagnostic tools. To elucidate distinct responses during cell genetic modification, methods to achieve transfection at the single-cell level are of great interest. In recent years, single-cell technologies have become increasingly robust and accessible, although limitations exist. This review article aims to cover various microfluidic-based physical methods for single-cell intracellular delivery such as electroporation, mechanoporation, microinjection, sonoporation, optoporation, magnetoporation, and thermoporation and their analysis. The mechanisms of various physical methods, their applications, limitations, and prospects are also elaborated.

Secular trends in testosterone- findings from a large state-mandate care provider

BACKGROUND

Several studies from the US and Europe have shown a population-level decline in serum testosterone in men from 1970's to early 2000's. However, to the best of our knowledge, no study examining population-level decline in testosterone has been published in more recent years. The study objective was therefore to examine secular trends in testosterone levels among Israeli men in the first and second decades of the twenty-first century, METHODS: All incident total testosterone performed between1/2006 and 3/2019 among 102,334 male members of a large health organization.

RESULTS

A significant (p < 0.001) and prominent trend of age-independent decline in the testosterone levels was recorded during the study period for most age groups.

CONCLUSIONS

There was a highly significant age-independent decline in total testosterone in the first and second decades of the twenty-first century. The decline was unlikely to be explained by increasing rates of obesity.

Current Trends of Microfluidic Single-Cell Technologies

The investigation of human disease mechanisms is difficult due to the heterogeneity in gene expression and the physiological state of cells in a given population. In comparison to bulk cell measurements, single-cell measurement technologies can provide a better understanding of the interactions among molecules, organelles, cells, and the microenvironment, which can aid in the development of therapeutics and diagnostic tools. In recent years, single-cell technologies have become increasingly robust and accessible, although limitations exist. In this review, we describe the recent advances in single-cell technologies and their applications in single-cell manipulation, diagnosis, and therapeutics development.

A Comparison of Techniques to Evaluate the Effectiveness of Genome Editing

Genome editing using engineered nucleases (meganucleases, zinc finger nucleases, transcription activator-like effector nucleases) has created many recent breakthroughs. Prescreening for efficiency and specificity is a critical step prior to using any newly designed genome editing tool for experimental purposes. The current standard screening methods of evaluation are based on DNA sequencing or use mismatch-sensitive endonucleases. They can be time-consuming and costly or lack reproducibility. Here, we review and critically compare standard techniques with those more recently developed in terms of reliability, time, cost, and ease of use.

Efficient and stable transformation of Dunaliella pseudosalina by 3 strains of Agrobacterium tumefaciens

Introduction: Several platforms including mammalian, plant and insect cells as well as bacteria, yeasts, and microalgae are available for the production of recombinant proteins. Low efficiency of delivery systems, extracellular and intracellular degradation of foreign genes during transformation, difficulties in targeting and importing into the nucleus, and finally problems in integration into nuclear genome are the most bottlenecks of classical plasmids for producing recombinant proteins. Owing to high growth rate, no common pathogen with humans, being utilized as humans’ food, and capability to perform N-glycosylation, microalgae are proposed as an ideal system for such biotechnological approaches. Here, Agrobacterium tumefaciens is introduced as an alternative tool for transformation of the microalga Dunaliella pseudosalina.

Methods: The transformation of gfp gene into the D. pseudosalina was evaluated by three strains including EHA101, GV3301 and GV3850 of A. tumefaciens. The integrating and expression of gfp gene were determined by PCR, RT-PCR, Q-PCR and SDS-PAGE analyses.

Results: The T-DNA of pCAMBIA1304 plasmid was successfully integrated into the genome of the microalgal cells. Although all of the strains were able to transform the algal cells, GV3301 possessed higher potential to transform the microalgal cells in comparison to EHA101 and GV3850 strains. Moreover, the stability of gfp gene was successfully established during a course of two months period in the microalgal genome.

Conclusion : Agrobacterium is introduced as a competent system for stable transformation of Dunaliella strains in order to produce eukaryotic recombinant proteins.

Effective isotope labeling of proteins in a mammalian expression system

Isotope labeling of biologically interesting proteins is a prerequisite for structural and dynamics studies by NMR spectroscopy. Many of these proteins require mammalian cofactors, chaperons, or posttranslational modifications such as myristoylation, glypiation, disulfide bond formation, or N- or O-linked glycosylation; and mammalian cells have the necessary machinery to produce them in their functional forms. Here, we describe recent advances in mammalian expression, including an efficient adenoviral vector-based system, for the production of isotopically labeled proteins. This system enables expression of mammalian proteins and their complexes, including proteins that require posttranslational modifications. We describe a roadmap to produce isotopically labeled (15)N and (13)C posttranslationally modified proteins, such as the outer domain of HIV-1 gp120, which has four disulfide bonds and 15 potential sites of N-linked glycosylation. These methods should allow NMR spectroscopic analysis of the structure and function of posttranslationally modified and secreted, cytoplasmic, or membrane-bound proteins.