Primary cells, in vitro models of physiological relevance

Brian A. Shapiro, Ph.D.

I have recently joined ATCC as a Technical Writer, and have 14 years of experience growing a wide variety of cells. In the coming months, I will address topics such as how to choose the right cell type for your experiments, cell line cross-contamination, and microbial contamination in this blog.

Biomedical scientists often rely on in vitro cell models for the study of human physiology and the pathogenesis of disease. Human primary cells (HPCs) are frequently disregarded as a choice for cell cultures, as they typically require more technical expertise to establish in the laboratory than other cell types and must be used in early passage. While HPCs may be challenging to generate, they have much in common with cells in vivo; therefore HPCs may be the perfect addition to your experiments.

HPCs can be used to represent normal tissue physiology as they retain many of the secretory, barrier, contractile, and other physiological functions of their in vivo condition. Further, HPCs usually have normal expression of tumor suppressor genes and proto-oncogenes; this allows HPCs to display normal cell cycle controls. The fact that HPCs possess gene expression patterns similar to cells in vivo indicates that they would be excellent controls in experiments using tumorigenic cell lines or cell lines derived from diseased tissue in the study of cancer, Parkinson’s disease, or microbial infection. 

Beyond their use as controls for pathological studies, HPCs can be applied in a wide range of experiments that examine normal tissue and organ physiology. For example, primary human bronchial/tracheal epithelial cells, when cultured in an air-liquid interface culture system, have been observed to form airway epithelium, which secretes mucus and exhibit waving cilia¹. In addition, more than one primary cell type may be co-cultured to form complex tissue systems. For instance, primary human neonatal foreskin keratinocytes cultured on fibroblasts differentiate into the four functional layers of the epidermis². Because organs are 3-D and boast multiple cell types, these co-culture and 3-D culture systems come close to mimicking physiological organ systems. The similarity to in vivo tissue and organ systems suggest that these 3-D culture systems have applications in toxicity, tissue development, carcinogenesis, cosmetic testing, and wound repair studies.

HPC maintenance is similar to that of any other cell line, thanks to the availability of optimized media and reagent formulations, affordable cell matrix solutions, and detailed protocols. An alternative to isolating the cells yourself is through ordering the cells from a well-known biological resource center, such as ATCC. ATCC supplies cells from a broad range of tissue sources and uses cell-specific markers to ensure a high level of purity post-isolation. In addition, ATCC tests HPCs for viability, as well as contamination by mycoplasma, bacteria, and yeast. Thus, when the HPCs arrive in your laboratory, you simply thaw and plate the cells in the appropriate culture medium. The HPCs can then be treated to stimulate the desired cellular responses at any time during the maintenance phase. 

Considering the required technical expertise, the expense, and the inaccessibility of source tissue, the addition of HPCs to a laboratory’s inventory of in vitro models may seem daunting. However, the rewards to your research are more than worth the trouble. Because HPCs are untransformed, have similar gene expression as the cells in situ, and exhibit similar physiologic function as in vivo cells, they are indispensable for a wide range of experiments that examine normal physiology or disease pathology.

References

1.  Berube K, et al. Human primary bronchial lung cell constructs: the new respiratory models. Toxicology 278(3):311-8, 2010.

2.  Gangatirkar P, et al. Establishment of 3D organotypic cultures using human neonatal epidermal cells. Nat Protoc 2(1):178-86, 2007.