Anchorage Dependent Animal Cell Culture
Animal Cell Culture: Its origin and importance
Prior to discussing about the anchorage dependence of animal cell cultures, let us first briefly discuss animal cell culture in general and its importance. Animal cell culture has a history of over 100 years when the first attempts to grow cells were made by Ross Harrison who was able to show the development of nerve fibres from frog embryo tissue cultured in a blood clot. Physiologist Alexis Carrel was able to keep fragments of chick embryo heart alive and beating for three months in vitro. With the help of subsequent research and technology development, animal cell cultures have been used for in vitro experimental studies and also for production of numerous useful products such as interferon, erythropoietin, tissue plasminogen activator and other biopharmaceuticals. More recently, interest has also developed in the application of stem cell technology for cell based therapy. Animal cell cultures have also been used as vehicles to grow viruses for development of vaccines and to study viral infections in mammals. Thus, animal cell culture technology has found wide application which makes it indispensable to understand the essential features of animal cell growth in culture. Animal cells, unlike microbial or plant cells, are very fastidious and complex in their nutritional requirements and require special incubators wherein the levels of CO2, O2 and humidity are maintained similar to those prevailing in the source animal’s body. Animal cells can grow as adherent cells or suspension cultures. Some of the important features of animal cell cultures are as follows:
Features of animal cell growth in culture
Animal cells, depending on the tissue they have been isolated from, can grow even in the best nutritive media to only limited generations. They divide and fill the surface of the container they are growing in and then stop growing. The cells comprising tissues and organs such as liver grow only to a certain size after which they cease to grow. This phenomenon is observed in the normal body as well as in cell culture and is known as Contact Inhibition. When animal cells are cultured, their environment is different from that in vivo due to absence of cell-cell interaction, cell-matrix interaction, lack of three dimensional architecture and alteration in hormonal and nutritional environment. These differences lead to alterations in the way the cells adhere to the culture vessels, the way cells proliferate and the shape of the cells. Some cells like cancerous cells do not show the property of senescence and capable of growing indefinitely, pile on each other due to uncontrolled growth. Transformed cell lines (continuous cell lines) also display the property of indefinite growth. They show abnormal ploidy (are either aneuploid or heteroploid), there is no contact inhibition and anchorage dependence. The main objective of this paper is to define and distinguish between Adherent and Suspension cultures and to discuss strategies that are being used for scale up of Adherent cell cultures.
Adherent Cell Culture vs. Suspension Cell culture
The characteristics of cells in culture usually depend on the tissue that they have been isolated from: Adherent cells are derived from tissues of organs such as kidney which are not mobile and are embedded in connective tissue. They grow adhering to the culture vessel. Within the tissues of intact animals, most cells tightly contact and interact specifically with other cells via various cellular junctions. The cells also contact the extracellular matrix, a complex network of secreted proteins and carbohydrates that fills the spaces between cells. The matrix, whose constituents are secreted by cells themselves, helps bind the cells in tissues together; it also provides a lattice through which cells can move, particularly during the early stages of animal differentiation. The extracellular...
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