Cell lines is defined as the collection of cells originated from single cell. They are grown in the laboratory under environmental controlled conditions. Interestingly, they can be grown indefinitely. These days, cell lines have become an important tool to conduct medical and scientific research. In research, cell lines are replacing animal models but saving their life.
Types of Cell Lines –
There are three different types of cell lines : Primary, Immortalized and Continuous Cell lines.
Primary Cell Lines –
- They are obtained from tissue of an organism.
- Even after isolation and cultured in laboratory, they retain the physiological relevant characteristics of host organism or it’s tissue and hence serves as a good model to study biological processes.
- They show similar genotypic and phenotypic characteristics of the original tissue of an organisms.
- When primary cell lines are cultured, they have limited lifespan.
- They show senescence.
- Primary culture often consist of mixture of cells, hence they are heterogeneous.
Advantage –
Their physiological, genetic and phenotypic similarity to original tissue allows them to mimic in-vivo conditions. They are useful in testing drug toxicity and efficacy.
Limitations –
- They have limited lifespan making them difficult to culture for longer period of time.
- From their heterogenous nature, it is difficult to obtain cell culture of specific type.
- They are also very susceptive to contamination.
Immortalized Cell Clines –
- They are the populations of cells obtained from multicellular organisms that have undergone genetic mutations that allows them to bypass senescence (cellular ageing).
- Hence, they exhibit extended lifespan than primary or original cells.
- They may retain some characteristics of the original tissue.
- They are homogenous i.e. consisting of single type of cells.
Advantages –
- As they can be consistently cultured they assure constant supply of cells for research purpose.
- Their homogenous nature allow to obtain reproducible results.
- They are less sensitive to contamination as compared to primary cell lines.
Limitations –
- They are genetically unstable and hence during culturing, they may accumulated more mutations changing their genetic composition and altering their phenotype.
- Because of mutations, the immortal cell lines may loose their original characteristics.
Continous Cell Lines –
- They are derived from tumor cells or who have undergone spontaneous or induced mutations resulting in immortaility.
- The induced mutation can be obtained by activating oncogenes, viral infection or telomerase activation.
- They have unlimited lifespan.
- They may have abnormal number of chromosomes.
- The mutations make alteration in their genetic makeup and phenotypic behaviour.
- Example – HeLa cells (derived from cervical cancer, HEK293 cells (derived from human embryonic kidney)
Advantages –
- They grow at very faster rate than normal cell lines.
- They are easy grow in-vitro conditions.
- They are less susceptible to contamination.
Limitations –
- They are genetically unstable and hence during culturing, they may accumulated more mutations changing their genetic composition and altering their phenotype.
- Because of mutations, they may loose their original characteristics.
Stem Cell Line Culture –
The stem cells are the undifferentiated cells which has the potential to renew themselves and to differentiate into various types of special cells. When such stem cells are cultured in the laboratory under controlled conditions then it is called stem cell lines. There are different types of stem cell lines –
- Embryonic Stem cells – They are obtained from the inner mass of the blastocyst. The are totipotent meaning they can be differentiated into any cell type.
- Adult Stem Cells – These stem cells are pluripotent meaning they can be differentiated into few types of cells. example – hematopoietic stem cells, mesenchymal stem cells and neural stem cells.
- Induced Pluripotent Stem Cells (iPSCs) – The adult stem cells are reprogrammed to act like embryonic stem cells.
Morphological types of Cell lines –
On the basis of cell structure and cell shape, the cell lines are of following types
- Epithelial Cells – They are polygonal in shape, have well defined cell borders. They grow as monolayer. Ex – Hela and MDCK.
- Fibroblast Cells like – They are elongated and spindle shaped. They need substrate to grow hence, their growth pattern is adherent type. They also contact inhibition phenomenon where they stop growing when they come in contact with each other. Ex. MRC – 5 cells and NIH3T3 cells.
- Endothelial Cells – They are flat and have polygonal shape. They grow as monolayer and forms sheet like layer. Ex. Human umbilical vein endothelial cells.
- Lymphoblast like – They are spherical and grow in suspension. Ex. hybridoma cells.
What are the sources to get Cell lines:
- ATCC (American Type Culture Collection): It is the world’s top-notch institute who offers most extensive cell lines of human and animal for research purposes. Their cell biology collection provides more than 4,000 cell lines with different types.
- ECACC (The European Collection of Authenticated Cell Cultures): It is one of the world’s larger cell line collection institutes who provides more than 3,000 cell lines.
How to store Cell lines –
Storing is necessary in order to maintain the cell’s genetical integrity and viability. The most common method of storing cell lines is Cryopreservation. In cryopreservation, the cells are freezed at extremely low temperatures. But we need to ensure their survival by following these steps –
- The medium used to preserve cell lines contain cryoprotectant solution such as dimethyl sulfoxide (DMSO). it prevent crystalization of water that could damage the cells.
- The cells need to store at gradual decreasing temperature.
- At last, the cell lines are stored in special vials called cryovials. They are stored in liquid nitrogen (-196°C).
Applications of Cell Lines –
- The cells lines are used to test the efficiency and toxicity of new drugs.
- To study the gene expression.
- To develop and test vaccines.
- To understand molecular mechanism of cancer and find appropriate treatment against it.
- To check toxicity of pollutant on cells.