Mammalian Cell culture Techniques

What is the difference between primary and secondary cell lines?

What is cell line?

Cell line is established permanent culture, and having potential for indefinite growth in controlled environment i.e. culture media, Temperature and humidity. Cell lines are used in in vitro models for screening of toxicity and anticancer activities of the test item.

Cell lines are mainly two types:

  1. Primary cell lines
  2. Secondary cell lines

1. Primary cell lines

Primary cells are isolated directly from the tissue e.g. Human or Animal, using enzymatic or mechanical methods. Once isolated, cells are transferred in tissue flask with the appropriate medium, essential amino acid and protein source.

These primary cells could be identified as Adherent cells and Suspension cells.

Adherent cells or anchorage-independent cells are generally grow in the flat surface and attached to the bottom of the Tissue flask. Once it gets nourished with medium, essential amino acid and protein, cells will grow according to its cell cycle. Cell lines confluency can be checked twice in a day in the aseptic conditions by the inverted microscope. Once confluency is reached up to 70%, cell lines can be removed from the flask by the enzymatic digestion. 

Suspension cells are generally floating cells in the medium and do not required to attach to the surface of the tissue flask. Most of the suspension cells are obtained from the blood system.

Primary cell lines have limited life span and generally required of additional care in terms of passage and sub culture. These cell lines can be used in the experiment with additional details of the donor’s age, medical history, race, and sex. Examples of the primary cell lines are Astrocytes, Hepatocytes, Smooth Muscle, Chondrocytes, Adipocytes and Hair cells.

2. Secondary cell lines

Secondary cell lines are those cell lines, which have been passaged over a long period of time and having homogeneous genotypic and phenotypic characteristics.  These types of cell lines can be passaged up to 80 passages, and can be utilized for the experiment. However, these kinds of cells are less referred because they have lost the true characteristics of the original tissue from which they were isolated. Examples of the primary cell lines are HeLa, HEK293, CHO and Sf9.