Cellular conservation of endangered midget buffalo (Lowland Anoa, Bubalus quarlesi) by establishment of primary cultured cell, and its immortalization with expression of cell cycle regulators

Controlled cell proliferation and immortalization of human dental pulp stem cells with a doxycycline-inducible expression system

Human dental pulp stem cells are a potentially useful resource for cell-based therapies and tissue repair in dental and medical applications. However, the primary culture of isolated dental pulp stem cells has notably been limited. A major requirement of an ideal human dental pulp stem cell culture system is the preservation of efficient proliferation and innate stemness over prolonged passaging, while also ensuring ease of handling through standard, user-friendly culture methods. In this study, we have engineered a novel human dental pulp stem cell line, distinguished by the constitutive expression of telomerase reverse transcriptase (TERT), and the conditional expression of the R24C mutant cyclin-dependent kinase 4 (CDK4R24C) and Cyclin D1. We have named this cell line Tet-off K4DT hDPSCs. Furthermore, we have conducted a comprehensive comparative analysis of their biological attributes in relation to a previously immortalized human dental pulp stem cells, hDPSC-K4DT, which were immortalized by the constitutive expression of CDK4R24C, Cyclin D1 and TERT. In Tet-off K4DT cells, the expression of the K4D genes can be precisely suppressed by the inclusion of doxycycline. Remarkably, Tet-off K4DT cells demonstrated an extended cellular lifespan, increased proliferative capacity, and enhanced osteogenic differentiation potential when compared to K4DT cells. Moreover, Tet-off K4DT cells had no observable genomic aberrations and also displayed a sustained expression of stem cell markers even at relatively advanced passages. Taken together, the establishment of this new cell line holds immense promise as powerful experimental tool for both fundamental and applied research involving dental pulp stem cells.

Characterization of Common Minke Whale (Balaenoptera Acutorostrata) Cell Lines Immortalized with the Expression of Cell Cycle Regulators

Primary cultured cells cannot proliferate infinite. The overcoming of this limit can be classified as immortalization. Bypass of p16 senescence protein induces efficient immortalization various types of mammalians is previously reported. However, the Cetacea species is not known. Here, that common minke whale-derived cells can be immortalized with a combination of human genes, mutant cyclin-dependent kinase 4 (CDK4R24C ), cyclin D1, and Telomerase Reverse Transcriptase (TERT) is reported. These results indicate that the function of cell cycle regulators in premature senescence is evolutionarily conserved. This study describes the conserved roles of cell cycle regulators in the immortalization of cells from humans to Cetacea species. Furthermore, using RNA-seq based on next-generation sequencing, the gene expression profiles of immortalized cells are compared with parental cells as well as those immortalized with SV40 large T antigen, which is once a popular method for cellular immortalization. The profiling results show that newly established common minke-whale-derived immortaliozed cells have completely different profiles from SV40 cells. This result indicates that the expression of mutant CDK4, cyclin D1, and TERT enables to establish immortalized cell lines with different biological nature from SV40 expressing cells.

Immortalization of American miniature horse-derived fibroblast by cell cycle regulator with normal karyotype

Immortalized cells serve as a crucial research tool that capitalizes on their robust proliferative properties for functional investigations of an organism. Establishing an immortalized American miniature horse cell line could yield valuable insights into these animals' genetic and physiological characteristics and susceptibility to health issues. To date, immortalized small horse cells with normal karyotypes have not been established. In this study, we successfully established primary and immortalized fibroblast cell lines through the combined expression of human-derived mutant cyclin-dependent kinase 4 (CDK4R24C), cyclin D1, and Telomerase Reverse Transcriptase (TERT), although CDK4R24C and cyclin D1, SV40T and TERT did not result in successful immortalization. Our comparison of the properties of these immortalized cells demonstrated that K4DT immortalized cells maintain a normal karyotype. Ultimately, our findings could pave the way for the development of targeted interventions to enhance the health and well-being of American miniature horses.

Sheep-derived cell immortalization through the expression of cell cycle regulators and biological characterization using transcriptomes

Sheep are important domestic animals for the production of wool and meat. Although numerous cultured cell lines from humans and mice have been established, the number of cell lines derived from sheep is limited. To overcome this issue, the efficient establishment of a sheep-derived cell line and its biological characterization is reported. Mutant cyclin-dependent kinase 4, cyclin D1, and telomerase reverse transcriptase were introduced into sheep muscle-derived cells in an attempt to immortalize primary cells using the K4DT method. Furthermore, the SV40 large T oncogene was introduced into the cells. The successful immortalization of sheep muscle-derived fibroblasts was shown using the K4DT method or SV40 large T antigen. Furthermore, the expression profile of established cells showed close biological characteristics of ear-derived fibroblasts. This study provides a useful cellular resource for veterinary medicine and cell biology.

Immortalization of primary cells derived from the endangered Ryukyu long-furred rat

The Ryukyu long-furred rat is an endangered species confined to the southernmost three small islands of Japan (Amami-Oshima, Tokunoshima, and Okinawa). Its population is rapidly decreasing because of roadkill, deforestation, and feral animals. To date, its genomic and biological information are poorly understood. In this study, we successfully immortalized Ryukyu long-furred rat cells by expressing a combination of cell cycle regulators, mutant cyclin-dependent kinase 4 (CDK4^R24C) and cyclin D1, together with telomerase reverse transcriptase or an oncogenic protein, the Simian Virus large T antigen. The cell cycle distribution, telomerase enzymatic activity, and karyotype of these two immortalized cell lines were analyzed. The karyotype of the former cell line immortalized with cell cycle regulators and telomerase reverse transcriptase retained the nature of the primary cells, while that of the latter cell line immortalized with the Simian Virus large T antigen had many aberrant chromosomes. These immortalized cells would be valuable for studying the genomics and biology of Ryukyu long-furred rats.

Immortalization of cells derived from domestic dogs through expressing mutant cyclin-dependent kinase 4, cyclin D1, and telomerase reverse transcriptase

Dog is the first animal that was established as a close partner of human beings. Based on the vast genetic diversity and breeding, dogs exhibit unique genetic evolution and diversity from Chihuahua to St. Bernard. The safety tests of the pharmacological products also included domestic dogs as the test subjects. Although the safety confirmation test of chemicals for human use is important, the welfare of experimental animals requires special consideration. In this study, we cultured domestic dog-derived primary fibroblasts isolated from their muscle tissues. Furthermore, we successfully immortalized them through lentivirus-mediated gene transfer of mutant cyclin-dependent kinase 4 (CDK4), cyclin D1, and telomere reverse transcriptase (TERT). We further demonstrated that the established immortalized domestic dog-derived fibroblasts retained the characteristics of the original parental cells. These cells might act a suitable in vivo model system to replace the implication of animals for evaluating the potential toxicity of pharmacological chemicals.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10616-021-00504-0.

Establishment of human airway epithelial cells with doxycycline-inducible cell growth and fluorescence reporters

We previously reported the successful establishment of multiple immortalized cell lines that preserved the original nature of the primary cells via co-expression of R24C mutant cyclin-dependent kinase 4 (CDK4^R24C), Cyclin D1, and telomerase reverse transcriptase (TERT). However, as these genes are kind of oncogenes, tools to control their expression levels are favorable. In this study, we describe a new polycistronic lentiviral vector expressing proliferation factors, CDK4^R24C and Cyclin D1 along with enhanced green fluorescence protein (EGFP) under the control of doxycycline (Dox)-dependent transactivator (rtTA) and tetracycline response element (TRE). By introducing the Dox-inducible lentiviral vector into human airway epithelial cells, we established a novel human airway epithelial cell line harboring polycistronic Dox-inducible CDK4^R24C and Cyclin D1, referred to as Tet-on K4D cells. We showed that the cell growth of Tet-on K4D cells could be controlled by Dox. Furthermore, expression of K4D genes and rtTA gene can be independently monitored by fluorescent imaging. Cultured airway epithelial cells are useful as a tool for studying the pathogenesis of lung disorders. Altogether, our established human airway epithelial cells could be used for a variety of studies such as lung pathology and biology underlying the differentiation process to form the complex pseudostratified multicellular layers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-021-00477-0.

The transcriptome of wild-type and immortalized corneal epithelial cells

Cellular immortalization enables indefinite expansion of cultured cells. However, the process of cell immortalization sometimes changes the original nature of primary cells. In this study, we performed expression profiling of poly A-tailed RNA from primary and immortalized corneal epithelial cells expressing Simian virus 40 large T antigen (SV40) or the combination of mutant cyclin-dependent kinase 4 (CDK4), cyclin D1, and telomere reverse transcriptase (TERT). Furthermore, we studied the expression profile of SV40 cells cultured in medium with or without serum. The profiling of whole expression pattern revealed that immortalized corneal epithelial cells with SV40 showed a distinct expression pattern from wild-type cells regardless of the presence or absence of serum, while corneal epithelial cells with combinatorial expression showed an expression pattern relatively closer to that of wild-type cells.

Measurement(s)	Molecular Profiling
Technology Type(s)	RNA sequencing
Sample Characteristic - Organism	Homo sapiens

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14093807

Establishment, characterization, and cryopreservation of cell lines derived from red-rumped agouti (Dasyprocta leporina Linnaeus, 1758) - A study in a wild rodent

Somatic cells can be used for rescuing wild mammals of ecological and economic importance, such as red-rumped agouti, through their application in advanced technologies. Thus, appropriate cell isolation, culture, and storage through cryopreservation can ensure the future safe use of these cells. We aimed to establish and evaluate the effects of culture time (second, fifth, and eighth passages) and cryopreservation on the morphology, viability, metabolism, proliferative activity, reactive oxygen species (ROS) levels, mitochondrial membrane potential (ΔΨm), and apoptosis on somatic cells derived from red-rumped agouti skin. Initially, we identified six dermal fibroblast lines by morphology, immunophenotyping, and karyotyping assays. In vitro culture after the second, fifth, and eighth passages, as well as the cryopreservation conditions used did not affect the metabolism or level of apoptosis. Nevertheless, cells in the fifth passage featured a reduction in proliferative activity and an increase in ROS levels when compared to second and eighth passage cells. Moreover, cryopreservation resulted in reduced ΔΨm when compared to non-cryopreserved cells. Additionally, cryopreserved cells showed a reduction in viability immediately after thawing; nevertheless, the viability of these cells was re-established after 11 days of in vitro culture and was similar to that of non-cryopreserved cells. In conclusion, we have shown that viable fibroblasts can be obtained from red-rumped agouti skin, featuring minimal changes after eight passages in in vitro culture systems. Additionally, adjustments to the cryopreservation protocol are necessary to reduce cellular oxidative stress caused by low temperatures.

Establishment and characterization of cell lines from human endometrial epithelial and mesenchymal cells from patients with endometriosis

OBJECTIVE

To establish and characterize cell lines derived from human endometrial epithelial cells (ECs) and mesenchymal cells (MCs) from patients with and without endometriosis.

DESIGN

In vitro experimental study.

SETTING

University and national cancer center research institute.

PATIENT(S)

Two women with endometriosis and two women without endometriosis.

INTERVENTION(S)

Sampling of endometrial ECs and MCs.

MAIN OUTCOME MEASURE(S)

Establishing immortalized endometrial ECs and MCs with quantitative reverse transcription-polymerase chain reaction (qRT-PCR), immunocytochemical analysis, and RNA sequence profiling performed to characterize the immortalized cells and a cell proliferation assay, three-dimensional culture, and assays for hormone responses performed to characterize the features of ECs.

RESULT(S)

The qRT-PCR, immunocytochemical analysis, and Western blot analysis revealed that the ECs and MCs maintained their original features. Moreover, the immortalized cells were found to retain responsiveness to sex steroid hormones. The ECs formed a gland-like structure in three-dimensional culture, indicating the maintenance of normal EC phenotypes. The RNA sequence profiling, principal component analysis, and clustering analysis showed that the gene expression patterns of the immortalized cells were different from those of cancer cells. Several signaling pathways that were statistically significantly enriched in ECs and MCs with endometriosis were revealed.

CONCLUSION(S)

We successfully obtained four paired immortalized endometrial ECs and MCs from patients with and without endometriosis. Using these cells could help identify diagnostic and therapeutic targets for endometriosis. The cell lines established in this study will thus serve as powerful experimental tools in the study of endometriosis.

Human Derived Immortalized Dermal Papilla Cells With a Constant Expression of Testosterone Receptor

Androgenetic alopecia (AGA) is the most common type of hair loss, and is mainly caused by the biological effects of testosterone on dermal papilla cells (DPCs). In vitro culturing of DPCs might be a useful tool for the screening of target molecule of AGA. However, primary DPCs cannot continuously proliferate owing to cellular senescence and cell culture stress. In this study, we introduced mutant cyclin-dependent kinase 4 (CDK4), Cyclin D1, and telomerase reverse transcriptase (TERT) into DPCs. We confirmed protein expression of CDK4 and Cyclin D1, and enzymatic activity of TERT. Furthermore, we found the established cell line was free from cellular senescence. We also introduced the androgen receptor gene using a recombinant retrovirus, to compensate the transcriptional suppressed endogenous androgen receptor in the process of cell proliferation. Furthermore, we detected the efficient nuclear translocation of androgen receptor into the nucleus after the treatment of dihydrotestosterone, indicating the functionality of our introduced receptor. Our established cell line is a useful tool to identify the downstream signaling pathway, which activated by the testosterone.

Primary and immortalized cell lines derived from the Amami rabbit (Pentalagus furnessi) and evolutionally conserved cell cycle control with CDK4 and Cyclin D1

The Amami rabbit (Pentagulus furnessi) is a dark brown-furred rabbit classified as an endangered species and only found in the Amami Islands of Japan. They are often called living fossils because they retain primitive characteristics of ancient rabbits that lived approximately 1 million years ago, such as short feet and hind legs and small ears. Although the ancient rabbit has disappeared due to the competition with European rabbit (Oryctolagus cuniculus) in the most of the Asian area, Amami rabbit survived since Amami Islands has isolated from Japan and Taiwan. Although Amari rabbit is one of the protected animals, their population decreases each year due to human activities, such as deforestation and roadkill. In this study, we collected roadkill samples of Amami rabbits and established primary and immortalized fibroblast cell lines. Combined expression of human-derived mutant Cyclin-dependent kinase 4, Cyclin D1, and hTERT allowed us to immortalize fibroblasts successfully in three individuals of Amami rabbits. The immortalized fibroblasts dramatically extended the cell culture period, when it was compared with the cell culture period of wild type cells. Furthermore, the immortalized cells maintained their normal chromosomal pattern (2n = 46). Our results suggest that cellular senescence which mainly regulated by p16-RB signaling pathway is conserved in animal evolution at least from 1 million years ago.

Efficient immortalization of human dental pulp stem cells with expression of cell cycle regulators with the intact chromosomal condition

Clinical studies have recently demonstrated that autologous transplantation of mobilized dental pulp stem cells is a safe and efficacious potential therapy for pulp regeneration. However, some limitations need to be addressed, such as the high cost of the safety and quality control tests for isolated individual dental pulp cell products before transplantation. Therefore, more efficient in vitro culturing of human dental pulp stem cells might be useful for providing low cost and high reliability testing for pulp regeneration therapy. In this study, we established a novel immortalized dental pulp stem cell line by co-expressing a mutant cyclin-dependent kinase 4 (CDK4^R24C), Cyclin D1, and telomerase reverse transcriptase (TERT). The established cell line maintained its original diploid chromosomes and stemness characteristics and exhibited an enhanced proliferation rate. In addition, we showed the immortalized human dental pulp stem cells still keeps their osteogenic and adipogenic differentiation abilities under appropriate culture conditions even though the cell proliferation was accelerated. Taken together, our established cell lines could serve as a useful in vitro tool for pulp regeneration therapy, and can contribute to reproducibility and ease of cell handling, thereby saving time and costs associated with safety and quality control tests.

Establishment of immortalized primary cell from the critically endangered Bonin flying fox (Pteropus pselaphon)

The Bonin flying fox (Pteropus pselaphon) is one of the most critically endangered species of animals. The number of this species is estimated to be around 150; being classified at the top rank in the list by International Union of Animal Conservation. Our group previously showed that expression of CDK4, CYCLIN D1, and telomerase reverse transcriptase (TERT) efficiently induce immortalization of human, bovine, swine, monkey, and buffalo-derived cells. In this manuscript, we successfully established the primary cells from Bonin flying fox. We introduced CDK4, CYCLIN D1, and TERT into the primary cells. The established cells showed efficient expression of introduced genes at the protein level. Furthermore, the established cells were free from senescence, indicating it reached to immortalization. Moreover, we showed that interspecies somatic cell nuclear transfer of Bonin flying fox derived cell into bovine embryo allowed the development of the embryo to 8 cell stages. Our established cell has the potential to contribute to species conservation.

Human-Derived Corneal Epithelial Cells Expressing Cell Cycle Regulators as a New Resource for in vitro Ocular Toxicity Testing

The Draize test has been used on rabbits since the 1960s to evaluate the irritation caused by commercial chemicals in products such as cosmetics or hairdressing products. However, since 2003, such tests, including the Draize test for cosmetics, have been prohibited in European countries because they are considered problematic to animal welfare. For this reason, replacement of in vivo methods with the alternative in vitro methods has become an important goal. In this study, we established a corneal epithelial cell line co-expressing a mutant cyclin-dependent kinase 4 (CDK4), Cyclin D1, and telomerase reverse transcriptase (TERT). The established cell line maintained its original morphology and had an enhanced proliferation rate. Furthermore, the cells showed a significant, dose-dependent decrease in viability in an irritation test using glycolic acid and Benzalkonium chloride. These cells can now be shared with toxicology scientists and should contribute to increasing the reproducibility of chemical testing in vitro.

Rat-derived feeder cells immortalized by expression of mutant CDK4, cyclin D, and telomerase can support stem cell growth

The maintenance of stem cells often requires the support of feeder cells. Primary mouse embryonic fibroblasts (MEFs) have traditionally been used as feeder cells, and although these MEF-derived feeder cells have exhibited a reasonable performance, they require repeated cell isolation, since MEFs cannot expand indefinitely. To overcome this limitation, immortalized cells, such as STO cells, have been used. However, one major disadvantage is that previously reported immortalized cells can only support stem cell cultures for a relatively short period, typically 4 to 7 days. In this study, we found that our newly established rat-derived fibroblasts immortalized by the expression of mutant cyclin-dependent kinase 4, cyclin D, and telomerase reverse transcriptase, can function as feeder cells for relatively long cell culture periods of approximately 14 days. The rat-derived immortalized cells developed in this study should be a useful source of feeder cells to support stem cell research.

Extended proliferation of chicken- and Okinawa rail-derived fibroblasts by expression of cell cycle regulators

Although immortalized cultured cells are useful for various functional assays or transcriptome analysis, highly efficient and reproducible immortalization methods have not been developed in avian-derived cells. We introduced the simian virus 40 T antigen (SV40T) and human papillomavirus (HPV)-E6E7 to chick and Okinawa rail (endangered species)derived fibroblast. As a result, neither the SV40T nor E6E7 genes could induce avian cell immortality. Accordingly, we attempted to use a recently developed immortalization method, which involved the coexpression of mutant cyclin-dependent kinase 4 (CDK4), Cyclin D, and TERT (K4DT method) in these avian cells. Although the K4DT method could not efficiently induce the efficient immortalization in mass cell population, cellular division until the senescence was significantly extended by K4DT, we succeeded to obtain the immortalized avian cells (chick K4DT: one clone, Okinawa rail K4DT: three clones, Okinawa rail K4DT + telomerase RNA component: one clone) with K4DT expression. We conclude that K4DT expression is used to extend the cell division and immortalization of avian-derived cells.

Efficient immortalization of cells derived from critically endangered Tsushima leopard cat (Prionailurus bengalensis euptilurus) with expression of mutant CDK4, Cyclin D1, and telomerase reverse transcriptase

Tsushima leopard cat is the subspecies of Amur cats, and it is classified as the most highest class of critically endangered animals. Although the protection activity is highly recognized, the number of animals is decreasing due to the human activity and invasion of domestic cats and infectious disease. In this study, we succeeded primary culture of normal fibroblasts derived from the Tsushima leopard cat (Prionailurus bengalensis euptilurus). Furthermore, we introduced the human derived mutant Cyclin Dependent Kinase 4, Cyclin D1, and telomere reverse transcriptase. We showed that the expression of these three genes efficiently immortalized cells derived from Tsushima leopard cat. Furthermore, we showed that the chromosome pattern of the established cells is identical with the original one. These data indicate that our method of immortalization is useful to establish cell lines from critically endangered cats, which potentially contributes to the re-generation of critically endangered animals from cultured cell with reproductive technique, such as somatic cloning.

Expression of human mutant cyclin dependent kinase 4, Cyclin D and telomerase extends the life span but does not immortalize fibroblasts derived from loggerhead sea turtle (Caretta caretta)

Conservation of the genetic resources of endangered animals is crucial for future generations. The loggerhead sea turtle (Caretta caretta) is a critically endangered species, because of human hunting, hybridisation with other sea turtle species, and infectious diseases. In the present study, we established primary fibroblast cell lines from the loggerhead sea turtle, and showed its species specific chromosome number is 2n = 56, which is identical to that of the hawksbill and olive ridley sea turtles. We first showed that intensive hybridization among multiple sea turtle species caused due to the identical chromosome number, which allows existence of stable hybridization among the multiple sea turtle species. Expressions of human-derived mutant Cyclin-dependent kinase 4 (CDK4) and Cyclin D dramatically extended the cell culture period, when it was compared with the cell culture period of wild type cells. The recombinant fibroblast cell lines maintained the normal chromosome condition and morphology, indicating that, at the G1/S phase, the machinery to control the cellular proliferation is evolutionally conserved among various vertebrates. To our knowledge, this study is the first to demonstrate the functional conservation to overcome the negative feedback system to limit the turn over of the cell cycle between mammalian and reptiles. Our cell culture method will enable the sharing of cells from critically endangered animals as research materials.