Animal Cell Culture as a Substitute for Animal Experiments- Dr C R Meera

 

Animals are extensively used for research purposes. They are mainly used for efficacy testing and toxicological screening of drugs for different infectious and non-infectious diseases and for screening of carcinogens. Animals are also sacrificed for medical and surgical experiments. They are also widely used for production of vaccines, antibiotics etc. The number of animals used for experiments have increased considerably with advancement in medical technology & research. Millions of experimental animals are exploited or sacrificed all over the world every year.  Various animals are used for this purpose which include rodents (mice, rats, hamsters, rabbits, guinea pigs), fishes (zebra fish, trout), birds (mainly chicken), amphibians (xenopus frogs), primates, dogs, cats etc. Many animals die during experiment and others are sacrificed at the end of experiments. The pain, distress and death experienced by the animals during scientific experiments have been a debating issue for a long time. Various acts and laws have been passed to bring the control over unethical use of animals and minimize the pain to animals during experimentation. Regulations put forward by the Animal Ethics Committee have to be strictly followed for conducting animal experiments.

 

Animal cell culture, growing cells in dishes is an excellent alternate for animal experiments. It has many advantages over animal experiments.

1. Cost and space required are more in animal experiments. Cost of animal experiments are high as breeding, maintenance and care of animals are to be done according to Government rules. Animals have to be maintained in specific breeding centers occupying large areas associated with the research centers. Cell culture is less expensive compared to animal experiments and cells can be grown in small containers. Space consumed for cell culture lab is also very less or even we can work with cell lines on a bench top.
2. Animal experiments are difficult to perform and require skilled/trained manpower is required to handle the experiments. Cell culture techniques are easy to perform and less manpower required.

3.       In animal experiments, the number of animals required for a single experiment is many. But in cell culture, many experiments can be done using one animal by dividing the tissue into different experimental groups. Thus multiples of the test can be easily performed.  

   E.g.: Almost all cosmetics, drugs and chemicals are tested for their toxicity and efficacy before commercialization. For example, irritancy test. To check the irritancy of cosmetics/chemicals previously Draize test was used, which requires animals (mainly rabbit). It is very painful and every time a new animal is used. The procedure involves applying 0.5 mL or 0.5 g of a test substance to the eye or skin of a restrained, conscious animal, and then leaving it for set amount of time before rinsing it out and recording its effects. The animals are observed for up to 14 days for signs of erythema and edema in the skin test, and redness, swelling, discharge, ulceration, hemorrhaging, cloudiness, or blindness in the tested eye.  Cell culture replaced it with Corneal organ culture. The bovine cornea is cultured up to three weeks in laboratory and various analytical methods are used to evaluate the toxicological effect of test chemical irritancy in vitro.              Live animals and embryos are used to study effects of some compounds on embryo development. In vitro embryonic stem cell culture test helps to reduce the number of live embryo used and the compounds which are toxic toward developing. 

4. Another advantage of cell culture is time. Animals experiments have time consuming lengthy protocols and takes considerable time. It usually takes a whole day to do one experiment. Organ or tissue culture experiments are of shorter duration compared animal experiments and done with multiple samples at one time.

5. .   Tissue culture is having controlled physiochemical environment (pH, temperature, osmotic pressure, O₂, CO₂ tension etc.) as well as physiological conditions within the system which cannot be controlled in animal experiments. Hence results of tissue culture are more reliable than animal experiments.

6.     Cell cultures are more suitable for screening the efficacy or toxicity of drugs, carcinogens and chemicals.  In cell culture, the compound to be screened is cultured with isolated organ, tissue or cells. In such systems, it is easy to understand the response of cell line towards the drug. In the whole animal, it is not easy to determine the specific effect of a particular drug. Because, it is possible that known or unknown endogenous substances in the animal body may be interacting with the exogenous material being tested.

7.         Also less reagents are required in cell culture which are readily available to target cells. In animal experiments, 90% injected chemical is lost by excretion and distribution to tissues other than target cells. In cell culture, cells are exposed directly to the reagent at a lower and defined concentration and with direct access to the target cells.

8.     In vitro cell culture is a good way to screen the compounds at preliminary stages. For example, use of the human hepatocyte culture gives the information about how a drug would be metabolized and eliminated from the body. Such experiments help to eliminate unsuitable compounds from further studies and thus minimizes the use of animals in further experiments.

9.       Tissue samples collected from animals for experiments are invariably heterogeneous. But cultured cell lines, after one or two serial passages assume a homogeneous or uniform constitution which reduces the need for statistical analysis of variance.