Cells are regarded as the true biological atom
It has been well-documented that primary cells can only undergo a predetermined and finite number of cell divisions in culture, which is the biggest drawback of them. With the population doublings, primary cells enter a state where they can no longer divide called replicative senescence, identified by changes in cell morphology, gene expression, and metabolism. So, it’s important to establish immortalized cells in vitro to study cell growth, differentiation, and senescence.
Immortalized cells stand between these two types, having properties more like primary diploid cells but possessing unlimited dividing capacity.
The human cells that have been genetically modified to have the characteristics of both primary cells and continuous cell lines are called hTERT-immortalized cells. Human telomerase reverse transcriptase (hTERT) is a catalytic protein subunit of the enzyme telomerase, which is responsible for maintaining telomeres and the stability of the human genome.
They are a breakthrough in cell biology research and are commonly used in basic research and tissue engineering. hTERT-immortalized cells combine the in vivo nature of primary cells with traditional cell line’s ability to survive continuously in vitro. hTERT-immortalized cells derived by primary cells that bypass normal cellular senescence and have an extended life span.
Normal diploid cells have a limited lifespan in vitro, but immortal cells (such as cancer and immortalized) can divide infinitely, which facilitates their use in scientific research. Nevertheless, cancer cells usually possess aberrant karyotype and altered traits, while cultured primary cells retain a morphology and physiology similar to those of the cells in vivo. The important factor for in vitro experiments is, having properties more like primary diploid cells but possessing extended dividing capacity Immortalized cells. A head on comparison between hTERT-immortalized cells and Primary Cells is mentioned in Table 1.
Comparison between hTERT Immortalized Cells and Primary cells
| Primary Cells | hTERT-Immortalized | |
| Mimic in vivo Tissue Phenotype | √ √ √ √ | √ √ √ |
| Karyotypic Stability | Diploid | Diploid/Pseudodiploid |
| Proliferative Capacity | √ | √ √ √ |
| Supply | √ | √ √ √ |
| Inter-Experimental Reproducibility | Low | Good |
| Cost | HIGH | MEDIUM |
| Ease of Use | √ | √ √ |
How hTERT–immortalized cells are developed?
Approximately 85–90% of tumor cells acquire immortality through a telomerase-dependent mechanism.
Conditional immortalization uses inducible transgene technology to create cells that can be expanded in a consistent fashion when the transgene is active.
Permanent activation of transgene leads to continuously division of cells.
Telomerase enzyme comprising of two components called RNA component (i.e., hTERC or hTR) and a catalytic component (i.e. hTERT).
Catalytic component that is hTERT is responsible to restore the DNA base pairs lost from the telomeres during cell division. Active telomerase in cells maintain chromosomal length and the cells continue to divide without becoming senescent.
Transfection of hTERT into human primary cells leads to elongation and maintenance of the telomere ends of the chromosomes. In many instances, forced expression of hTERT alone enables the cells to repress replicative senescence and overcome the growth crisis, effectively leading to their immortalization.
Characteristics of hTERT–immortalized cells
Immortalized cells have to retain a normal karyotype, not have malignant and tumorigenic properties, and proliferation rate is optimum and possess similar characteristics (marker expression, morphology, and phenotype) as of source parent cells. Moreover, if cells are immortalized via hTERT stimulation, they must have hTERT activity which is different from the ancestors’ cells. The characteristics of cells after successful immortalization via the ectopic expression of hTERT are listed in Figure 1.
Applications of hTERT–immortalized cells
Immortalized cells are a valuable tool in cell biology, therefore, the development of immortalizing techniques and methods for characterizing immortalized cells is very important.
There are many situations in which the transient regeneration of cells is necessary. When large quantities of cells are required for biochemical analysis, genetic manipulations, or genetic screens.
The ectopic expression of hTERT has been reported to immortalize human skin keratinocytes, dermal fibroblasts, muscle satellite (stem) cells, vascular endothelial cells, myometrial cells, pigment retinal cells, and human mammary epithelial cells (HMECs). The applications of the hTERT cells are listed below in Figure 2.
Conclusion
hTERT immortalized cells faithfully represent the physiological properties of primary cells in vivo. hTERT-immortalized cells can be created by transferring an exogenous hTERT cDNA to primary human cells. This can prevent telomere shortening and block the onset of telomere-controlled senescence. We at Kosheeka provide various primary cells e.g. liver-derived cells, Primary Retinocytes , Vascular-Derived Cells, Reproductive System-Derived Cells , Skin-Derived Cells, Adipose Tissue-Derived Cells, Bone Marrow-Derived Cells, Extra Embryonic Fetal Tissue-Derived Cells, Blood-Derived Cells, Dental Pulp-Derived Cells to support groundbreaking research and therapeutic developments. We are capable of accommodate your research requirements and achieving desired goals of the study. If you want to know more about our services and products, please feel free to contact us. We look forward to collaborate with you in the future.
Frequently Asked Questions (FAQs)
Q1. What is hTERT-immortalized cells?
The human cells that have been genetically modified to have the characteristics of both primary cells and continuous cell lines are called hTERT-immortalized cells. Human telomerase reverse transcriptase (hTERT) is a catalytic protein subunit of the enzyme telomerase, which is responsible for maintaining telomeres and the stability of the human genome.
Q2. How are hTERT-immortalized cell lines are developed?
Transfection of hTERT into human primary cells leads to elongation and maintenance of the telomere ends of the chromosomes. In many instances, forced expression of hTERT alone enables the cells to repress replicative senescence and overcome the growth crisis, effectively leading to their immortalization.
Q3. What is the difference between hTERT-immortalized cells and Primary Cells
| Primary Cells | hTERT-Immortalized | |
| Mimic in vivo Tissue Phenotype | √ √ √ √ | √ √ √ |
| Karyotypic Stability | Diploid | Diploid/Pseudodiploid |
| Proliferative Capacity | √ | √ √ √ |
| Supply | √ | √ √ √ |
| Inter-Experimental Reproducibility | Low | Good |
| Cost | HIGH | MEDIUM |
| Ease of Use | √ | √ √ |
Q4. What are the Characteristics of hTERT–immortalized cells.
- Extended proliferative capacity
- Expression of specific markers like in parent primary cells
- Stable karyotyping
- Requirement of growth factors for proliferation
- Non-Malignancy, Normal cell cycle control
- Stability of cell morphology, retainment of parent cell morphology
- Continued expression of active hTERT
Q5. Applications of hTERT–immortalized cells.
- Tissue Engineering and transplantation
- Cell-based drug screening
- Long-term studies of biochemical and physiological aspects
- Invitro model for differentiation and carcinogenesis
- Biological functions of hTERT
- Genetic engineering and modifications
- Cancer research and studies of oncogenes
