A Brief Overview of Animal Primary Cells

Animal Primary Cells

Animal primary cells are isolated and purified directly from animal tissues via a mechanical or enzymatic method, or a combination of both. They usually carry all the characteristics of the original animal cells from specific tissues such as brain, liver, pancreas, lung, heart muscle, kidney, breast, prostate, testis, thyroid, stomach, small intestine, colon, skeletal muscle, adipose tissue, and skin. Animal primary cells can be taken from either healthy or diseased animals with no other experiments being performed before tissue removal.

Once the target tissue is digested and dissected in sterile conditions, it will be submitted to filtration and centrifugation for further purification, resuspended primary cells will be counted and cryopreserved with cryopreservation media or plated in cell culture containers with their favorable natural (consisting of naturally occurring biological fluids, such as plasma, tissue extract, etc.) or artificial medium (made up of essential amino acids, vitamins, salts, serum, carbohydrates, cofactors, etc.) needed for their proper growth before incubation, medium will then be replaced after a few hours depending on specific cell types. As an example, Figure 1 shows the procedure of isolation and purification of primary hepatocytes from a mouse liver [1]. Animal primary cells purified under such a condition is named passage 0 (P0), they can either be cryopreserved in cryovials as stocks for a short period of time or delivered to our customers in culture flasks directly.

So far, AcceGen offers more than 900 different lots of Animal Primary Cells for research use, providing a wide variety of species for primary cells including Mouse Primary Cells, Rat Primary Cells, Bovine Primary Cells, Monkey Primary Cells, Rabbit Primary Cells, Porcine Primary Cells and Other Primary Cells consisting of primary cells from sheep, bird, chicken, guinea pig, turkey, horse, goat and feline. In addition, our animal primary cells also cover many different strains. For example, mouse primary cells provided by AcceGen include but are not limited to CD1, ICR, BALB/c, B129, CF1, C57BL/6, B6129SF2/J, C57BLKS/J, and DBA/2 strains.

Adherent vs. Suspension

Animal primary cells may grow either as adherent cultures or remain in suspension [2]. Adherent cells are anchorage dependent and proliferate as a monolayer requiring the attachment to a solid or semi-solid substrate for proliferation. Adherent animal primary cells adhere to the culture vessel with the help of their extracellular matrix, these cells usually derived from tissues that are immobile and present in the connective tissue networks, examples are epithelial cells and fibroblasts. As the bottom of such culture vessels are covered with a continuous layer of cells with one-cell thickness, they are also known as monolayer cultures. The majority of animal primary cells grow as adherent cultures. As they grow as single layers, it is convenient to transfer them directly to a cover slip during culture maintenance and examine them under microscopes at later stage of experiments.

Suspension cells, also called non-adherent or anchorage independent cells, are not attached to the surface of the culture vessels. Instead, they grow while floating in the culture medium. Suspension cells can be maintained in culture flasks that are not tissue-culture treated. However, to maintain adequate gas exchange the medium may require agitation which is usually achieved either with a magnetic stirrer or in a rotating spinner flask. Moreover, compare to adherent animal primary cells, suspension animal primary cells are easier to passage and have faster growth rate, they also do not require enzymatic dissociation with trypsin or collagenase, although daily cell counts and viability determination maybe required following their growth patterns. Hematopoietic stem cells (derived from blood, bone marrow, or spleen) and neural stem cells are two examples of suspension primary cells.

Advantages of Animal Primary Cells

Although animal primary cells have a finite lifespan, they provide several unique benefits to researchers. For one thing, since animal primary cells closely reflect in vivo conditions without laboratory modifications, they are an alternative for in vivo studying the biological functions of cells. As models for human systems, animal primary cells can be used to examine a wide range of disease mechanisms and evaluate novel treatments before applying the results to humans. The physiochemical and physiological conditions of animal primary cell cultures are all adjustable, such as pH, temperature, O₂/CO₂ concentration, and osmotic pressure of the culture media [3]. Such investigations offer key insights into a wide range of human diseases. For another, in vitro cultures of isolated cells from different animals have also helped deepen the understanding of different functions and mechanisms of operations of different cells. The study of cell metabolism and investigation of the physiology and biochemistry of cells among different species are good examples. Moreover, animal primary cells also serve as great models for cytotoxic assays. For example, the effect of various drugs or compounds on specific cell types such as neuronal or liver cells can be studied. Animal primary cells from neural, hepatic, pancreatic, pulmonary, cardiac, renal, gastric, intestinal, skeletal, adipose, dermal, and ocular systems are all commonly used models in biomedical research and drug discovery. Furthermore, by using animal primary cells, the ethical, moral, and legal questions for utilizing animals in experiments can be avoided.

To further address the unique advantages of animal primary cells, we have also summarized the different characteristics between primary cell cultures and continuous cell lines in Table 1.

Table 1. Differences between Primary Cell Cultures and Continuous Cell Lines.

Compare to primary cell cultures, continuous cell lines have an infinite number of cell generations. They grow faster and achieve higher cell densities in cultures. Additionally, since continuous cell cultures are immortal and tumorigenic, they have no contact inhibition and have lost the limitation of proliferation. They usually grow as multilayers or in suspension and have a potential to be cultured in large-scale bioreactors. Nevertheless, the major disadvantages of continuous cell lines compare to animal primary cells are their chromosomal instability, phenotypic variation, and the change in specific and characteristic markers in relation to the donor tissue [4]. Therefore, continuous cell lines cannot represent the in vivo state as primary cells.

Conclusions

Animal primary cells isolated directly from animal tissues maintain many of the important markers and functions as in vivo. However, the majority of them have a finite lifespan and limited expansion capacity. Therefore, it is crucial to use animal primary cells at low passage at all times. Although some animal primary cell types like neurons do not even have the ability to divide.

It is worth mentioning that animal primary cells are never 100% pure, so the higher passage of cells are used, the greater risk of having contaminating cells outgrow the cells of interest are taken. Meanwhile, even if for some primary cell types that can be passaged more times than others, phenotypic and genetic changes always occur with each passaging. These genetic changes will then lead to epigenetic changes. Therefore, we strongly encourage our customers to use animal primary cells as early passage as possible to prevent genetic drift.

At AcceGen, we always freeze and provide our animal primary cell products at the lowest passage – P0 to ensure that our customers can get the most biologically relevant animal primary cells. AcceGen offers authenticated animal primary cell products for global customers with the most reliable procedures and the highest manufacturing standards. You can explore the full list of products by clicking Animal Primary Cells.

Reference

[1] M. Charni-Natan, I. Goldstein, Protocol for Primary Mouse Hepatocyte Isolation, STAR Protoc 1(2) (2020) 100086.

[2] R.C. Dubey, Chapter 8 Animal Cell Culture, A Textbook Of Biotechnology For Class-XII S Chand (2018) 185-210.

[3] A. Verma, M. Verma, A. Singh, Chapter 14 Animal tissue culture principles and applications, Animal Biotechnology (2020), 269-293.

[4] D.E.H. Tee, Culture of Animal Cells: A Manual of Basic Technique, Journal of the Royal Society of Medicine 77 (1984) 902-903.