Cell Lines

This cell line is an adenovirally transformed cell line produced by infecting human embryonic kidney cells with Ad5 DNA (Graham et al., 1977).

From: Advances in Pharmacology , 1999

Cell Lines

A.B. Ulrich , P.M. Pour , in Brenner's Encyclopedia of Genetics (Second Edition), 2001

Cell Culture and the Establishment of Cell Lines

Cell culture and cell lines have assumed an important role in studying physiological, pathophysiological, and differentiation processes of specific cells. It allows the examination of stepwise alterations in the structure, biology, and genetic makeup of the cell under controlled environments. This is especially valuable for complex tissues, such as the pancreas, which is composed of various cell types, where in vivo examination of individual cells is difficult, if not impossible. The extreme difficulties in the isolation and purification of individual epithelial cells from complex tissues by maintaining their native characteristics have hampered our understanding of their physiological, biological, growth, and differentiation characteristics.

Attempts have been made to culture almost every tissue, including neuronal cells, bone, cartilage, and hair cells. In general, animal cells, particularly fibroblasts, can be more successfully cultured than human cells, and human fibroblasts are easier to culture than epithelial cells. Also, different epithelial cells show different responses to culture conditions. Despite advances in culturing techniques, human epithelial cells could not be maintained in culture for long time periods. The problem is the tendency of human cells to undergo senescence after a certain cell division. Transfection of these cells with the E6E7 gene of human papilloma virus 16, or with the small and large T antigen of the simian virus 40, has partially overcome the senescence and has increased cell longevity in vitro but has not led to immortality of the cells. The resulting genetic manipulations limit the use of these cells for molecular biological studies, especially for defining genetic changes that occur during cell differentiation and transformation. The introduction of these foreign genes alters the function of the host's regulatory genes including the inactivation of the tumor suppressor protein p53 and retinoblastoma protein pRb. Even though these cell lines do not grow in soft agar, which would be a first sign of transformation, or when introduced into nude mice, the additional transfection with certain oncogenes such as k-ras has resulted in the malignant transformation of the cells.

The quality of the culture medium and the cell preparation technique are very important for the maintenance of human epithelial cells in culture. By using a defined culture medium and cell separation technique, human pancreatic epithelial cells have been kept in culture for more than 10 months. Another, recently discovered method to prolong the life span of human cell is the infection of cells with telomerase, an enzyme that prevents telomere loss by de novo addition. It restores the length of telomeres, which otherwise shorten with each cell proliferation, leading to senescence. So far, successful reports include immortalized fibroblasts and retinal and endothelial cells.

Attempts have been made to identify and culture stem cells of specific tissues because these cells can better adjust to the environmental conditions and can give rise to a variety of mature cells under specific environments. For example, it has been shown that cultured colon cells containing stem cells can give rise to either neuroendocrine cells, colon cells, or a mixture of them. Therefore, such cultures provide ample opportunity to investigate differentiation pathways and provide a unique tool to test the effects of natural and synthetic substances, including cytokines, growth factors, nutrients, and physical factors in the maturation or death of the cells.

The mechanisms of malignant transformation can be studied in vitro using cell lines treated with a carcinogen or radiation in culture. Gradual phenotypical, genetic (e.g., DNA adduct levels, alkylations, mutations), and chromosomal changes can be investigated. Specific markers associated with the transformation may be expressed, such as tumor growth factor-α (TGF-α) and epithelial growth factor receptor (EGFR). Unfortunately, it has not been possible to date to transform human epithelial cells in culture, so the need for animal models still exists. Rodents are much more susceptible to carcinogenicity than humans.

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Prospective Potency of TGF-β1 on Maintenance and Regeneration of Periodontal Tissue

Hidefumi Maeda , ... Akifumi Akamine , in International Review of Cell and Molecular Biology, 2013

6.1.2 Multipotency of PDLSC-like cell lines

Both cell lines had unique characteristics in multipotency in vitro: cell line 1–11 exhibited the potential to differentiate into osteoblastic and adipocytic cells, and cell line 1–17 performed osteoblastic, adipocytic, chondrocytic, and even neurocytic differentiations (Fujii et al., 2008; Tomokiyo et al., 2008). These cell lines intrinsically originated from the same donor; however, the differentiation range of cell line 1–17 was wider than that of cell line 1–11 (Fig. 6.6). This suggests that PDLSCs at the various differentiation stages are localized in PDL tissue. Based on the results described above, cell line 1–17 may be more immature than cell line 1–11, implying that these cell lines are PDL-committed stem cells unlike with BMMSCs.

Figure 6.6. Schema explaining the differentiation potency of two cell lines. Cell line 1–11 differentiated into osteoblasts and adipocytes in vitro, while cell line 1–17 exhibited osteoblastic, adipocytic, neurocytic, and chondrocytic differentiation. When these cell lines were transplanted into periodontal defects experimentally prepared in immunodeficient rat molar, cell line 1–11 displayed osteoblastic, cementoblastic, and fibroblastic behavior, whereas cell line 1–17 showed the only fibroblastic behavior.

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CELLULAR, MOLECULAR, GENOMICS, AND BIOMEDICAL APPROACHES | Culture of Fish Cell Lines

N.C. Bols , ... L.E.J. Lee , in Encyclopedia of Fish Physiology, 2011

Introduction

Cell lines are cultures of animal cells that can be propagated repeatedly and sometimes indefinitely. They arise from primary cell cultures. Primary cultures are initiated directly from the cells, tissues, or organs of animals and are typically used in experiments within a few days. By convention, the passaging or subcultivation of a primary culture begins a cell line. However, not all primary cultures yield cell lines. Instead, the cells of some subcultivated cultures die off slowly. Why the cells of other cultures keep on growing and allow these cultures to be continuously subcultivated is a complex and incompletely understood subject. The subject is intensively studied with mammalian cells because of the relevance of this to the mechanisms of cellular senescence and the origins of cancer cells. In the case of mammalian cell lines, some are finite. They can only be subcultivated a limited number of times before they senesce. Yet other mammalian cell lines are continuous or immortal and can be grown indefinitely. Continuing with the case of mammals, some primary cultures or finite cell lines can be experimentally immortalized to become continuous cell lines.

By contrast, with fish, little is known about cellular senescence and immortalization. Fortunately and surprisingly, many fish cell cultures have been subcultivated indefinitely. These cell lines are said to have become spontaneously immortalized. This is how nearly all fish cell lines have arisen. Most of these have been derived from bony fish, but they are called simply fish or piscine cell lines. The development of fish cell lines is described elsewhere (see the 'Further reading' section). Here, the sources and types of fish cell lines are noted and what is needed to maintain these cell lines is described, ending with a brief overview of how the cell lines are being used.

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Diagnosis and Methods

Wang-Shick Ryu , in Molecular Virology of Human Pathogenic Viruses, 2017

Cell lines are the most convenient methods for virus cultivation in a laboratory. However, in a case where cell lines susceptible to the virus infection are unavailable, primary cells explanted directly from a living animal or human are the only choice for virus cultivation. What are the characteristic differences between primary cells and cell lines?

A diagram depicting steps involved in preparation of primary cell versus immortalized cell line.

Cell strains are cells that have a limited proliferation capability and can be immortalized. Cell line can be directly prepared from cancerous cells that are already immortalized during cancer development.

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Animal Tissue Culture

Anju Verma , in Animal Biotechnology, 2014

Indefinite Cell Lines

Cell lines obtained from in vitro transformed cell lines or cancerous cells are indefinite cell lines and can be grown in monolayer or suspension form. These cells divide rapidly with a generation time of 12 to 14 hours and have a potential to be sub-cultured indefinitely. The cell lines may exhibit aneuploidy (Bhat, 2011) or heteroploidy due to an altered chromosome number. Immortalized cell lines are transformed cells with altered growth properties. HeLa cells are an example of an immortal cell line. These are human epithelial cells obtained from fatal cervical carcinoma transformed by human papilloma virus 18 (HPV18). Indefinite cell lines are easy to manipulate and maintain. However these cell lines have a tendency to change over a period of time.

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Medical Biotechnology and Healthcare

Z. Li , in Comprehensive Biotechnology (Second Edition), 2011

5.43.2.2.2 Cell line

Cell line is a general term that applies to a defined population of cells that can be maintained in culture for an extended period of time, retaining stability of certain phenotypes and functions. Cell lines are usually clonal, meaning that the entire population originated from a single common ancestor cell. There are a number of advantages that make cell lines useful as in vitro model. First, cell lines provide a homogenous population of cells. Second, they are relatively easy to grow and can be continuously subcultured through an acceptable number of passages to provide large numbers of cells in a short period of time. These have made cell lines an attractive model for high-throughput drug screening through the consequent output of reproducible and consistent data on toxicity testing. However, the main disadvantage is that their functional levels are frequently different from those found in primary cells and some important functions are missed due to transformation. Moreover, as cell lines are originated from a single donor, they cannot be utilized for evaluation of genotypic and phonotypic differences in response to drugs in humans.

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Bacterial Infections of Laboratory Mice

Charles B. Clifford , Kathleen R. Pritchett-Corning , in The Laboratory Mouse (Second Edition), 2012

Mycoplasma

Mycoplasma arginini

Although cell lines are frequently infected with mycoplasma [95, 96], these rarely have any ability to infect mice, and are of consequence primarily because of their effects on the cell cultures. For example, no reports of M. arthritidis, M. neurolyticum or M. collis infecting cell lines, and only a single abstract reporting M. pulmonis could be found [95]. However, M. arginini, which is occasionally found as a contaminant of cell lines, has recently been identified as a cause of pyogranulomatous arthritis in immunodeficient mice following inoculation with infected cell lines [97].

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Reprogramming the Genome: CRISPR-Cas-based Human Disease Therapy

Edina Poletto , Guilherme Baldo , in Progress in Molecular Biology and Translational Science, 2021

Abstract

Cell lines can be good models for the disease they are derived from but can also be used to study general physiological and pathological processes. They can also be used to generate cell models of diseases when primary cultures are not available. Recent genome editing tools have been very promising tools toward creating cell models to mimic diseases in vitro. In this chapter, we highlight techniques used to obtain genome-edited cell lines, including cell line selection, transfection and gene editing tools available, together with methods of phenotype characterization and, lastly, a few examples of how in vitro disease models were created using CRISPR-Cas9.

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Recombinant Protein Expression: Eukaryotic Hosts

Douglas Nmagu , ... Kelvin H. Lee , in Methods in Enzymology, 2021

2.1 Cell line development process

CLD is an important part of process development and results in the creation of specific mAb-producing cell lines (or clones). CLD is a multi-step process involving host cell line selection, transfection of the gene of interest (GOI), clonal isolation, selection, amplification, and finally, clonal expansion ( Lee et al., 2019).

The most prevalent host cell for biopharmaceutical production is CHO cells. However, production host cell lines may be viewed as being inherently heterogeneous owing to distinct genotypic and/or phenotypic characteristics. Structural changes include genetic variations such as single nucleotide polymorphism (SNPs), mutations, and chromosomal rearrangements (Bandyopadhyay et al., 2019; Vcelar et al., 2018; Wurm & Hacker, 2011). The variability in specific growth rates, product glycosylation, and biosynthetic capacities are functional variations contributing to the observed clonal variations.

Once a host cell line is chosen, the next step in creating a recombinant cell line is the integration of the GOI into the host cell genome. Classically, the chromosomal integration site for a GOI is random leading to the incorporation of the transgene in diverse genomic regions of the host cell line. The random integration of the transgene can also result in copy number variations (CNVs) and differences in the transcriptional capacity leading to heterogeneities in the productivity and product quality across the cell populations (Porter, Racher, Preziosi, & Dickson, 2010).

Clonally-derived recombinant cell lines can also undergo significant changes in the expression levels of the transgene during clonal expansion. This tendency is attributed in part to the loss or recombination of transgenes. Moreover, epigenetic changes such as promotor methylation or histone acetylation can also contribute to clonal variations in productivity (Weinguny et al., 2020).

Recent developments to address these issues include targeted strategies for gene insertion guided by a knowledge-based selection of the ideal integration sites (Shin & Lee, 2020). Examples of such strategies include recombinase-mediated targeted integration and programmable nuclease-mediated targeted integration (Baumann et al., 2017). While these methods have successfully addressed some of the limitations of early CLD activities, the field is still far from the ability to completely predict and control clone phenotypes.

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Studies of Neurotoxicity in Cellular Models

ELIZABETH McFARLANE ABDULLA , IAIN C. CAMPBELL , in In Vitro Methods in Pharmaceutical Research, 1997

2 Murine septal (SN56) lines, motor neurone (NSC19) lines and human neuroblastoma (LA-N-2) cells: use of differentiated cholinergic cells for evaluating acetylcholinesterase inhibitors

Cell lines (e.g. SN56 and NSC19) have also been developed to identify and/or characterize compounds that cause OPIDN. 39 SN56 cells are derived from the septal nucleus and closely resemble brain cholinergic neurones. They develop neuriies when treated with agents that increase intracellular cyclic AMP levels and, concomitantly, their acetylcholine (ACh) synthesis and release are enhanced. Retinoic acid causes a several-fold stimulation of ACh synthesis in these cells and this effect is additive to that of forskolin. NSC19 cells and LA-N-2 cells are similarly capable of synthesizing ACh. 39 These three cell lines have proved very useful in examining, for example, the effects of organophosphates (using diisopropyl phosphorofluoridate (DFP), a prototypical OPIDN-causing compound, and (paraoxon) an organophosphate that does not cause delayed neurotoxicity). The examination of several types of cholinergic cell line has identified cells that are particularly vulnerable to AChE inhibition, and the use of human and murine cell lines has allowed assessment of the importance for OPIDN.

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