II General Introduction to Cells, Cell Lines and Cell Culture

Introduction

Cell and tissue culture technology holds a central position in modern biomedical research. Cells in culture are useful model systems for studying normal physiological and biochemical processes in cells and can even be used for diagnostic purposes. The main advantage of using cell culture systems is the consistency and reproducibility obtained.

In most situations cells or tissues have to be cultivated for longer periods to obtain sufficient numbers of cells for analysis. Alternatively, the same cells can be continuously propagated in the laboratory for use in repeated experiments. Normal cells (primary cells) usually divide only a limited number of times before entering into senescence. However, cells can be immortalized through transformation, a process that can occur spontaneously or by treating the cells with chemicals or viruses. Longterm culture of cells requires well established aseptic techniques to avoid contamination with bacteria, yeasts, molds or viruses. Contamination may cause erroneous results and eventually the loss of valuable cell material.

Usually, there are two different ways of growing cells in culture, either as cells attaching to the surface of the culture vessel, adherent cells, or as cells growing in suspension. Most cells from vertebrates, either in the form of primary cells or cell lines, adhere to the plastic surface of the culture vessel. Some cells adhere rather loosely and may require that the plastic of the culture tray is coated with a 1 % solution of gelatin, collagen or fibronectin before use. Most cells and cell lines of hemopoietic origin, typically lymphocytes, grow free-floating in the culture medium.

Salt Solutions

In vitro, tissue and cells should only be exposed to isotonic solutions at physiological pH, either in the form of balanced salt solutions or culture media. The simplest salt solutions are saline (0.9 % NaCl) or phosphate-buffered saline (PBS, 10–15 mM phosphate buffer in saline). Many balanced salt solutions (typically Earle's balanced salt solution (EBSS), Hank's balanced salt solution (HBSS), Dulbecco's phosphatebuffered saline (D-PBS) or similar) have been developed to provide optimal short term support for different cell types in vitro and for different culturing conditions.

Culture Media

Most culture media are based on balanced salt solutions with a variable number of additions in the form of amino acids, vitamins, trace minerals, a pH indicator, and eventually antibiotics. Such media are called basal media. Typical examples are RPMI 1640 (Roswell Park Memorial Institute 1640) and DMEM (Dulbecco's Modified Eagle Medium), eventually with the Ham's F12 nutrient mixture (DMEM/ F12). In addition to the basal media special medium formulations that require less serum addition, so called Reduced Serum Media, alternatively Serum-Free Media (SFM), are available for special cell types and special applications.

The culture medium is absolutely crucial for successful cell culture experiments. In general, recommendations are available for each particular cell line or cell type. However, different media may satisfy the required conditions for a particular cell type. Thus, personal experience could be valuable when choosing medium. Such personal experience may also include observed beneficial effects due to the addition of non-essential amino acids, pyruvate, reducing agents etc. It is extremely important to know that any addition to ready-made media requires components that have been tested and certified for cell culture work. Even chemicals of pro analysi quality may contain traces of toxic compounds that can be detrimental to cells in culture.

 
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