Animal cell culture is one of the major tools now in the field of life science. It is the in-vitro technique where the cells are grown in the laboratory conditions by providing a proper nutrient source, growth factors and the environmental factors for the cell growth and division. In the Animal cell culture, the cells are obtained by either enzymatic action like Trypsinization or mechanically by Mincing or Chopping.
The Animal cell culture, the cells form a monolayer in the solid media and suspension in the liquid media. The method of a cell or tissue culture first involves the production of “Primary cells” and followed by subculturing or passaging produces “Secondary cells” or “Cell-lines”.
Content: Animal cell culture
- History of Animal cell culture
- Definition of Animal cell culture
- Types of Animal cell culture
- Process of Animal cell culture
- Difference between Normal and Continuous cells
History of Animal cell culture
There are many discoveries which led to the invention of the technique named “Animal cell culture”. By the discovery of Animal cell culture, there are some other discoveries also which made the practical study of cell culture possible.
Firstly the antibiotics were developed to prevent contamination. Secondly, the cell obtaining techniques were introduced to produce cell lines by “Trypsin”. Then, standard media were introduced which made the growth of cells far easier and faster.
|1878||Claude Bernard||Discovered mechanisms to maintain the living state of the organism after its death|
|1885||Raux||Discovered the maintenance of the embryonic chick cells in the saline culture|
|1897||Loeb||Discovered the survival of the cell isolated from blood and connective tissue in the serum and plasma|
|1903||Jolly||Demonstrated the cell division of Salamander leucocytes by an in-vitro method.|
|1907||Harrison||Discovered the growth of nerve fibres by cultivating the frog nerve cell in a lymph clot by hanging drop method|
|1910||Burrows||Introduced the cultivation of chicken embryo-cell in the plasma clots|
|1911||Lewis||Introduced a liquid medium containing sea water, serum, embryo extract, salts and peptones|
|1913||Carrel||Introduced certain aseptic techniques for the long term culturing of cells|
|1916||Rous and Jones||Introduced trypsin (Proteolytic enzyme) for the subculturing of confluent cells|
|1923||Carrel and Baker||Developed “Carrel” or “T-shaped” culture vessel for the cell|
|1927||Carrel and Rivera||Introduced first viral vaccine “Vaccinia”|
|1933||Gey||Introduced Roller tube technique|
|1940||Introduction of antibiotics like penicillin and streptomycin in cell culture to avoid contamination|
|1948||Earle||Isolated L-fibroblasts from the clones of single cells|
|1948||Fischer||Introduced chemically defined medium CMRL 1066|
|1949||Enders||Reported the growth of polio virus on the human embryonic cells|
|1952||Gey||Discovered the growth of continuous cell line from Hela- cells|
|1952||Dulbecco||Discovered plaque assay technique for animal viruses using confluent monolayers of the cultured cells|
|1954||Abercrombie||Introduced the property of “Contract inhibition”|
|1955||Eagle||Introduced chemically defined medium for the cell culture|
|1961||Hay Flick and Moorhead||Showed finite cell culturing by isolating human fibroblast WI-38|
|1964||Littlefield||Introduced HAT-medium for cell selection|
|1965||Ham||Introduced serum free medium|
|1975||Kohler and Milstein||Produced hybridoma capable of producing monoclonal antibody|
|1978||Sato||Established the basis for development of serum free media|
|1982||Introduction of human insulin as a therapeutic agent|
|1986||Lymphoblastoidy γIFN has been licensed|
|1987||Introduction of Tpac (tissue type plasminogen activator)|
|1989||Introduction of erythropoietin|
|1990||Introduction of recombinant products (HBsAG, factor VIII, HIV gp 120, CD4)|
Definition of Animal cell culture
Animal cell culture can define as the type of cell culture where the cell grows and multiplies either in a solid or liquid medium as a “Cell monolayer” or “Cell suspension” respectively to produce the Primary cells. Then followed by subculturing of primary cells, it produces Secondary cells to a definite cell number for the normal cells and indefinite for the continuous cells.
Types of Animal cell culture
On the basis of cell growth and division, the cell culture is of two types:
- Primary cell culture
- Secondary cell culture
Primary cell culture
It can define as the culturing of the cells from the tissue of the host animal. The cells can obtain directly by the mechanical method and indirectly by the enzymatic action. Once, the cells are obtained, they have to be cultured on a suitable container which is provided with all the nutrients required for the cell division and growth. The growth of primary either occur as “Adherent monolayer” on solid medium or as a “Suspension” in a liquid medium.
Adherent cells: These cells adhere to the solid surface and produce a cell population in the monolayer pattern. Adherent cells sometimes refer as “Confluent cell”, where the cells merge or contract to fill the surface area. The properties of the adherent cell include:
- Adherent cells are “Anchorage-dependent”.
- Grow as a “Monolayer”.
- Growth occurs on a solid surface or we can say “solid media”.
- Adherent cells fill the entire surface area of the container or vessel as a monolayer.
- Adherent cells follow the property of “contract inhibition”, where the cell itself ceases the growth of more cells to maintain the synchronized state by the chemical signalling which does not permit the overgrowth once a monolayer is formed.
Examples: Fibroblasts and epithelial cells are examples of Adherent cells.
Suspension cells: These are the cells that do not adhere to the surface of the medium provided. Suspension cells are the type of cells that floats as the suspension in the liquid medium. The properties of the adherent cell include:
- Suspension cells are “Anchorage-independent”.
- Floats as a “Suspension of cells” in the liquid culture medium.
- Growth occurs in the liquid nutrient medium.
- Suspension cells grow much faster than the adherent cells.
- There is a short lag phase in the Suspension cells.
- Enzyme action is not required for the dissociation of cells.
Secondary cell culture
It can define as the subculturing of the primary cells from the primary cells which produce secondary cells or cell lines. The passaging or subculturing of the primary cell results into a phenotypic and genotypic uniformity of the cell population.
By the subculturing, the cell-line becomes different from the original cell. On the basis of the life span of the cell, the cell lines categorize into two types:
Finite cell lines: In finite cell lines, there is limited cell division and limited life span. Passaging value is less as after some time the cells lose the ability to grow or proliferate and enters into the phase of senescence or ageing.
Example: Normal cells produce finite cell lines.
Continuous cell lines: In continuous cell lines, the number of cell division and passaging value is indefinite. The passaging value is more for the continuous cells which do not lose the ability to divide i.e. these can grow and divide by an infinite number of times.
Example: Cancerous cells produce Infinite or continuous cell lines.
Process of Animal cell culture
The process of animal cell culture includes the following steps:
- Tissue explant
- Cell extraction
- Culturing in a nutrient medium
Therefore, the process of animal cell culture can be summarized in the following way:
Tissue explant: The removal of tissue from the organ refers to as “Tissue explant”.
Cell extraction: The cell can extract from the tissue either mechanically or enzymatically. The extraction is mostly carried out by the enzyme action or by the process of “Trypsinization”.
Culturing in a nutrient medium: After that, the cell is cultured either on solid nutrient medium or liquid nutrient medium.
In a solid nutrient medium, the primary cells form a monolayer whereas in liquid medium primary cells appears as a cell suspension.
Subculturing: It also refers to as “Passaging” of the cell. After the formation of primary cells, the subculturing is carried out that is important to continuously study or to grow the cells. This is the most important step in cell culture, which helps us to understand the cell type.
Normal cell: It has low passaging value because these lose their ability to divide after some time due to cell ageing. Therefore, the cell divides to produce definite cell lines.
Continuous cell: It has high passaging value because as from the name it is clear that these kind of cells are having an ability to continuously divide. Therefore, the cell divides to produce indefinite cell lines.
Passaging value is directly proportional to the cell type and cell division.
- For continuous cells, the passaging value increases by which the cell division will be more.
- For normal cells, the passaging value decreases by the ageing of a cell by which the cell division capacity will also decrease.
Difference between Normal and Continuous cells
- The normal cell produces a monolayer whereas the continuous cell does not.
- The continuous cell does not follow the property of contract inhibition where normal cells follow.
- A normal cell has a property to divide for definite times whereas the continuous cell has a property to divide again and again.
- Continuous cells are having high passage value whereas normal cells are having low passage value.
- The capacity of dividing in the continuous cell remains the same as the first passaging whereas the capacity of dividing decreases as a result of cell ageing in the normal cells.
- Animal cell culture makes the use of a low amount of reagents.
- Serial passaging maintains the homogeneity of the cell types.
- Provides controlled physiological conditions.
- Provides controlled physiochemical conditions like temperature, oxygen concentration, ph etc.
- Animal cell culture requires high technical skills to interpret and to regulate the animal cell culturing.
- It is a very expensive method to carry out.
The animal cell culture can act as a “Modal organism” which can help us to study the effects of drugs, biochemistry etc. of the cell. By animal cell culture, we can perform Tissue engineering.
It also helps us to identify the cancerous cell as both the normal and continuous cells can be grown in the animal cell culture. We can also study the replication and life cycle of the virus, thus plays an important role in the field of virology.
In animal cell culture, we can also study the effect of different drugs on different cell types, thus it also helps in Toxicity testing.