Page 185 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

152 SECTION | I General

VetBooks.ir cultures need to be prepared and maintained under sterile compared to animals and they are amenable to cryopreser-
vation under liquid nitrogen. However, if maintained
conditions in order to reduce microbial contamination.
through high numbers of divisions, there is an increasing
Cells are maintained under defined conditions of humidity,
pH, and temperature. They are grown in a specific growth likelihood of genetic drift that might affect phenotypic
medium, which may have a number of supplements, such properties of relevance to toxicity testing.
as antibiotics, glutamine, serum, etc., which are different Finite cell lines are normally derived from primary
for each cell line. Growth conditions should be optimized cultures (see below) and can survive for 40 50 divisions
prior to experimental work. Excellent reviews on practical before finally dying (e.g., fibroblasts). Established cell
aspects of cell culture can be found in the following lines are effectively immortal, having been transformed
sources: Cohen and Wilkin (1996), Shaw (1996), Masters with a virus, a mutagen or spontaneously. These are gen-
(2000), Davis (2002), Gardner et al. (2004). erally tumor like in nature; some widely used examples
There are several types of cell cultures available for include mouse 3T3 fibroblasts, HeLa cells, and Chinese
in vitro testing that offer various degrees of complexity hamster ovary cells. However, many cell lines can be
and relatedness to the in vivo situation. In order of induced to differentiate, making them potentially useful
increasing complexity and genetic similarity to the tissue models of specific stages of development. For example,
of origin, these include permanent cell lines, primary the use of nerve growth factor or retinoic acid to induce a
cultures, stem cells, and organotypic cultures (Fig. 9.2) neuronal phenotype in cultures of rat PC12 pheochromo-
(Noraberg, 2004; Spielmann, 2005; Sundstrom et al., cytoma and human SH-SY5Y neuroblastoma cells,
2005; Efthymiou et al., 2014; Peters et al., 2015; Van respectively (Fujita et al., 1989; Presgraves et al., 2004).
Duinan et al., 2015). Additionally, embryonic, progenitor, and adult stem cell
Permanent cell lines are mitotic and can be finite, lines can be immortalized and some are commercially
established or clonal in nature. They have the advantage available (Cocks et al., 2013). The advantage of such cell
of being relatively easy and inexpensive to maintain models is that they may replicate developmental events

Culture Type Suitability/Limitations

Mitotic cell lines Medium to high throughput studies of basal
Increasing complexity and similarity to in vivo systems
toxicity (e.g., membrane damage, viability, etc.)
and cell proliferation. If immortalized, many cell
lines are tumor-like. Limited cell–cell
interactions and drug metabolism.

Differentiating cell lines Medium to high throughput screening and
mechanistic studies of developmental toxicity
and target cell specific toxicity. Often short-lived.
Limited cell–cell interactions and drug metabolism.

Primary cell cultures Developmental or target cell-specific toxicity.
Genetically more similar to target system but
generally heterogeneous and short-lived. Can be
used as coculture systems (e.g., reaggregates) to
simulate cell–cell interactions of target tissue but
usually have limited drug metabolism.

Organotypic/whole These are tissue slices or cultures organs that can
organ cultures maintain cell interactions and tissue function.
Generally unsuitable for medium to high
throughput analysis and may exhibit limited drug
metabolism.

FIGURE 9.2 Organization of a tiered system for in vitro toxicity testing.