Cephalin as an efficient fusogen in hybridoma technology: can it replace poly ethylene glycol?

Substantially Improved Electrofusion Efficiency of Hybridoma Cells: Based on the Combination of Nanosecond and Microsecond Pulses

As the initial antibody technology, the preparation of hybridoma cells has been widely used in discovering antibody drugs and is still in use. Various antibody drugs obtained through this technology have been approved for treating human diseases. However, the key to producing hybridoma cells is efficient cell fusion. High-voltage microsecond pulsed electric fields (μsHVPEFs) are currently one of the most common methods used for cell electrofusion. Nevertheless, the membrane potential induced by the external microsecond pulse is proportional to the diameter of the cell, making it difficult to fuse cells of different sizes. Although nanosecond pulsed electric fields (nsPEFs) can achieve the fusion of cells of different sizes, due to the limitation of pore size, deoxyribonucleic acid (DNA) cannot efficiently pass through the cell pores produced by nsPEFs. This directly causes the significant loss of the target gene and reduces the proportion of positive cells after fusion. To achieve an electric field environment independent of cell size and enable efficient cell fusion, we propose a combination of nanosecond pulsed electric fields and low-voltage microsecond pulsed electric fields (ns/μsLVPEFs) to balance the advantages and disadvantages of the two techniques. The results of fluorescence experiments and hybridoma culture experiments showed that after lymphocytes and myeloma cells were stimulated by a pulse (ns/μsLVPEF, μsHVPEF, and control), compared with μsHVPEF, applying ns/μsLVPEF at the same energy could increase the cell fusion efficiency by 1.5–3.0 times. Thus far, we have combined nanosecond and microsecond pulses and provided a practical solution that can significantly increase cell fusion efficiency. This efficient cell fusion method may contribute to the further development of hybridoma technology in electrofusion.

Lipid vesicles in pulsed electric fields: Fundamental principles of the membrane response and its biomedical applications

The present review focuses on the effects of pulsed electric fields on lipid vesicles ranging from giant unilamellar vesicles (GUVs) to small unilamellar vesicles (SUVs), from both fundamental and applicative perspectives. Lipid vesicles are the most popular model membrane systems for studying biophysical and biological processes in living cells. Furthermore, as vesicles are made from biocompatible and biodegradable materials, they provide a strategy to create safe and functionalized drug delivery systems in health-care applications. Exposure of lipid vesicles to pulsed electric fields is a common physical method to transiently increase the permeability of the lipid membrane. This method, termed electroporation, has shown many advantages for delivering exogenous molecules including drugs and genetic material into vesicles and living cells. In addition, electroporation can be applied to induce fusion between vesicles and/or cells. First, we discuss in detail how research on cell-size GUVs as model cell systems has provided novel insight into the basic mechanisms of cell electroporation and associated phenomena. Afterwards, we continue with a thorough overview how electroporation and electrofusion have been used as versatile methods to manipulate vesicles of all sizes in different biomedical applications. We conclude by summarizing the open questions in the field of electroporation and possible future directions for vesicles in the biomedical field.

A pathway from chromosome transfer to engineering resulting in human and mouse artificial chromosomes for a variety of applications to bio-medical challenges

Microcell-mediated chromosome transfer (MMCT) is a technique to transfer a chromosome from defined donor cells into recipient cells and to manipulate chromosomes as gene delivery vectors and open a new avenue in somatic cell genetics. However, it is difficult to uncover the function of a single specific gene via the transfer of an entire chromosome or fragment, because each chromosome or fragment contains a set of numerous genes. Thus, alternative tools are human artificial chromosome (HAC) and mouse artificial chromosome (MAC) vectors, which can carry a gene or genes of interest. HACs/MACs have been generated mainly by either a "top-down approach" (engineered creation) or a "bottom-up approach" (de novo creation). HACs/MACs with one or more acceptor sites exhibit several characteristics required by an ideal gene delivery vector, including stable episomal maintenance and the capacity to carry large genomic loci plus their regulatory elements, thus allowing the physiological regulation of the introduced gene in a manner similar to that of native chromosomes. The MMCT technique is also applied for manipulating HACs and MACs in donor cells and delivering them to recipient cells. This review describes the lessons learned and prospects identified from studies on the construction of HACs and MACs, and their ability to drive exogenous gene expression in cultured cells and transgenic animals via MMCT. New avenues for a variety of applications to bio-medical challenges are also proposed.

A systematic review and meta-analysis on the prevalence of Dupuytren disease in the general population of Western countries

BACKGROUND

Dupuytren disease is a fibroproliferative disease of palmar fascia of the hand. Its prevalence has been the subject of several reviews; however, an accurate description of the prevalence range in the general population--and of the relation between age and disease--is lacking.

METHODS

Embase and PubMed were searched using database-specific Medical Subject Headings; titles and abstracts were searched for the words "Dupuytren," "incidence," and "prevalence." Two reviewers independently assessed the articles using inclusion and exclusion criteria, and rated the included studies with a quality assessment instrument. In a meta-analysis, the median prevalence, as a function of age by sex, was estimated, accompanied by 95 percent prediction intervals. The observed heterogeneity in prevalence was investigated with respect to study quality and geographic location.

RESULTS

Twenty-three of 199 unique identified articles were included. The number of participants ranged from 37 to 97,537, and age ranged from 18 to 100 years. Prevalence varied from 0.6 to 31.6 percent. The quality of studies differed but could not explain the heterogeneity among studies. Mean prevalence was estimated as 12, 21, and 29 percent at ages 55, 65, and 75 years, respectively, based on the relation between age and prevalence determined from 10 studies.

CONCLUSIONS

The authors describe a prevalence range of Dupuytren disease in the general population of Western countries. The relation between age and prevalence of Dupuytren disease is given according to sex, including 95 percent prediction intervals. It is possible to determine disease prevalence at a certain age for the total population, and for men and women separately.

A systematic review and meta-analysis on the prevalence of Dupuytren disease in the general population of Western countries

BACKGROUND

Dupuytren disease is a fibroproliferative disease of palmar fascia of the hand. Its prevalence has been the subject of several reviews; however, an accurate description of the prevalence range in the general population--and of the relation between age and disease--is lacking.

METHODS

Embase and PubMed were searched using database-specific Medical Subject Headings; titles and abstracts were searched for the words "Dupuytren," "incidence," and "prevalence." Two reviewers independently assessed the articles using inclusion and exclusion criteria, and rated the included studies with a quality assessment instrument. In a meta-analysis, the median prevalence, as a function of age by sex, was estimated, accompanied by 95 percent prediction intervals. The observed heterogeneity in prevalence was investigated with respect to study quality and geographic location.

RESULTS

Twenty-three of 199 unique identified articles were included. The number of participants ranged from 37 to 97,537, and age ranged from 18 to 100 years. Prevalence varied from 0.6 to 31.6 percent. The quality of studies differed but could not explain the heterogeneity among studies. Mean prevalence was estimated as 12, 21, and 29 percent at ages 55, 65, and 75 years, respectively, based on the relation between age and prevalence determined from 10 studies.

CONCLUSIONS

The authors describe a prevalence range of Dupuytren disease in the general population of Western countries. The relation between age and prevalence of Dupuytren disease is given according to sex, including 95 percent prediction intervals. It is possible to determine disease prevalence at a certain age for the total population, and for men and women separately.

Cell electrofusion using nanosecond electric pulses

Electrofusion is an efficient method for fusing cells using short-duration high-voltage electric pulses. However, electrofusion yields are very low when fusion partner cells differ considerably in their size, since the extent of electroporation (consequently membrane fusogenic state) with conventionally used microsecond pulses depends proportionally on the cell radius. We here propose a new and innovative approach to fuse cells with shorter, nanosecond (ns) pulses. Using numerical calculations we demonstrate that ns pulses can induce selective electroporation of the contact areas between cells (i.e. the target areas), regardless of the cell size. We then confirm experimentally on B16-F1 and CHO cell lines that electrofusion of cells with either equal or different size by using ns pulses is indeed feasible. Based on our results we expect that ns pulses can improve fusion yields in electrofusion of cells with different size, such as myeloma cells and B lymphocytes in hybridoma technology.

FcRn overexpression in transgenic mice results in augmented APC activity and robust immune response with increased diversity of induced antibodies

Our previous studies have shown that overexpression of bovine FcRn (bFcRn) in transgenic (Tg) mice leads to an increase in the humoral immune response, characterized by larger numbers of Ag-specific B cells and other immune cells in secondary lymphoid organs and higher levels of circulating Ag-specific antibodies (Abs). To gain additional insights into the mechanisms underlying this increase in humoral immune response, we further characterized the bFcRn Tg mice. Our Western blot analysis showed strong expression of the bFcRn transgene in peritoneal macrophages and bone marrow derived dendritic cells; and a quantitative PCR analysis demonstrated that the expression ratios of the bFcRn to mFcRn were 2.6- and 10-fold in these cells, respectively. We also found that overexpression of bFcRn enhances the phagocytosis of Ag-IgG immune complexes (ICs) by both macrophages and dendritic cells and significantly improves Ag presentation by dendritic cells. Finally, we determined that immunized bFcRn mice produce a much greater diversity of Ag-specific IgM, whereas only the levels, but not the diversity, of IgG is increased by overexpression of bFcRn. We suggest that the increase in diversity of IgG in Tg mice is prevented by a selective bias towards immunodominant epitopes of ovalbumin, which was used in this study as a model antigen. These results are also in line with our previous reports describing a substantial increase in the levels of Ag-specific IgG in FcRn Tg mice immunized with Ags that are weakly immunogenic and, therefore, not affected by immunodominance.

Exploitation of the interaction of measles virus fusogenic envelope proteins with the surface receptor CD46 on human cells for microcell-mediated chromosome transfer

Background

Microcell-mediated chromosome transfer (MMCT) is a technique by which a chromosome(s) is moved from donor to recipient cells by microcell fusion. Polyethylene glycol (PEG) has conventionally been used as a fusogen, and has been very successful in various genetic studies. However, PEG is not applicable for all types of recipient cells, because of its cell type-dependent toxicity. The cytotoxicity of PEG limits the yield of microcell hybrids to low level (10^-6 to 10^-5 per recipient cells). To harness the full potential of MMCT, a less toxic and more efficient fusion protocol that can be easily manipulated needs to be developed.

Results

Microcell donor CHO cells carrying a human artificial chromosome (HAC) were transfected with genes encoding hemagglutinin (H) and fusion (F) proteins of an attenuated Measles Virus (MV) Edmonston strain. Mixed culture of the CHO transfectants and MV infection-competent human fibrosarcoma cells (HT1080) formed multinucleated syncytia, suggesting the functional expression of the MV-H/F in the CHO cells. Microcells were prepared and applied to HT1080 cells, human immortalized mesenchymal stem cells (hiMSC), and primary fibroblasts. Drug-resistant cells appeared after selection in culture with Blasticidin targeted against the tagged selection marker gene on the HAC. The fusion efficiency was determined by counting the total number of stable clones obtained in each experiment. Retention of the HAC in the microcell hybrids was confirmed by FISH analyses. The three recipient cell lines displayed distinct fusion efficiencies that depended on the cell-surface expression level of CD46, which acts as a receptor for MV. In HT1080 and hiMSC, the maximum efficiency observed was 50 and 100 times greater than that using conventional PEG fusion, respectively. However, the low efficiency of PEG-induced fusion with HFL1 was not improved by the MV fusogen.

Conclusions

Ectopic expression of MV envelope proteins provides an efficient recipient cell-oriented MMCT protocol, facilitating extensive applications for studies of gene function and genetic corrections.

An extreme strategy for the production of hybridoma

The ethical issues surrounding human immunization hamper the production of human monoclonal antibody through scarcity of immunized B cells in peripheral blood. This defect can be compensated in part by improvement of hybridoma production techniques. We have developed a new strategy to bypass the toxic effects of polyethylene glycol (PEG) as fusogenic reagent and hypoxanthine aminoptrin thymidine (HAT) as selective medium on newly fused cells. The Epstein-Barr virus (EBV) transformed peripheral blood mononuclear cells (PBMC) of accidentally Rh antigen sensitized persons were fused using cephalin as fugenic reagent, with emetine and actinomycin D pretreated heteromyeloma cells. Our results showed that 19-34% of EBV-transformed B cells were grown as hybridoma clones following selection. This extreme improvement in hybridoma production rate may end the fusion efficiency problem and make hybridoma production a plug-and-play technology.