Cell Immortality: In Vitro Effective Techniques to Achieve and Investigate Its Applications and Challenges

Abstract

Cells are very important to researchers due to their use in various biological studies in in vitro and in vivo settings. This importance stems from the short lifespan of most cells under laboratory conditions, which can pose significant challenges, such as the difficulties associated with extraction from the source tissue, ethical concerns about separating cells from human or animal models, limited cell passage ability, and variation in results due to differences in the source of the obtained cells, among other issues. In general, cells in laboratory conditions can divide into a limited number, known as the Hayflick limit, due to telomere erosion at the end of each cellular cycle. Given this problem, researchers require cell lines that do not enter the senescence phase after a limited number of divisions. This can allow for more stable studies over time, prevent the laborious work associated with cell separation and repeated cultivation, and save time and money in research projects. The aim of this review is to summarize the function and effect of immortalization techniques, various methods, their advantages and disadvantages, and ultimately the application of immortalization and cell line production in various research fields.

Keywords: cell division; cell line; hTERT; immortalization; telomeres.

Figure 1

The Hayflick limit. Naturally, with each cell division, the telomeres at the ends of chromosomes become shorter, a phenomenon known as the Hayflick limit. The final stage is also known as cellular aging.

Figure 2

A look at some of the applications of immortalized cells in different types of research.

Figure 3

Telomerase components and TERT structure. Telomerase is composed of three main components—hTERT, hTERC, and DKC1. The hTERC is associated with DKC1 and small nucleolar RNPs, NOP10, NHP2, and GAR1. The sequence, by adding repetitive TTAGGG sequences to the end of the telomere, prevents its shortening and naturally prevents cell aging. The protein complex shelterin, or telosome, protects telomere ends. The shelterin complex is made up of telomeric repeat binding factors 1 and 2 (TERF1 and TERF2), repressor/activator protein 1 (RAP1), protection of telomeres 1 (POT1), TERF1 interacting nuclear factor 2 (TINF2), and TPP1.

Figure 4

An overview of various types of cell immortalization methods.