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

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.

The effects of immortalization on the N-glycome and proteome of CDK4-transformed lung cancer cells

Biological experiments are often conducted in vitro using immortalized cells due to their accessibility and ease of propagation compared to primary cells and live animals. However, immortalized cells may present different proteomic and glycoproteomic characteristics from the primary cell source due to the introduction of genes that enhance proliferation (e.g. CDK4) or enable telomere lengthening. To demonstrate the changes in phenotype upon CDK4-transformation, we performed LC-MS/MS glycomic and proteomic characterizations of a human lung cancer primary cell line (DTW75) and a CDK4-transformed cell line (GL01) derived from DTW75. We observed that the primary and CDK4-transformed cells expressed significantly different levels of sialylated, fucosylated, and sialofucosylated N-glycans. Specifically, the primary cells expressed higher levels of hybrid- and complex-type sialylated N-glycans, while CDK4-transformed cells expressed higher levels of complex-type fucosylated and sialofucosylated N-glycans. Further, we compared the proteomic differences between the cell lines and found that CDK4-transformed cells expressed higher levels of RNA-binding and adhesion proteins. Further, we observed that the CDK4-transformed cells changed N-glycosylation after 31 days in cell culture, with a decrease in high-mannose and increase in fucosylated, sialylated, and sialofucosylated N-glycans. Identifying these changes between primary and CDK4-transformed cells will provide useful insight when adapting cell lines that more closely resemble in vivo physiological conditions.

Establishment of immortalized Egyptian Rousettus bat cell lines

The Egyptian Rousettus bat (Rousettus aegyptiacus) is a common fruit bat species that is distributed mainly in Africa and the Middle East. Bats serve as reservoir hosts for numerous pathogens. Human activities, such as hunting bats for food, managing vermin, and causing habitat loss, elevate the likelihood of transmission of bat pathogens to humans and other animals. Consequently, bat cell lines play a crucial role as research materials for investigating viral pathogens. However, the inherent limitation of finite cell division in primary cells necessitates the use of immortalized cells derived from various bat tissues. Herein, we successfully established six fibroblast cell lines derived from an infant bat heart and lungs and an elderly bat heart. Three of the six cell lines, called K4DT cells, were transduced by a combination of cell cycle regulators, mutant cyclin-dependent kinase 4, cyclin D1, and human telomerase reverse transcriptase. The other three cell lines, named SV40 cells, were transfected with simian virus 40 large T antigen. Transgene protein expression was detected in the transduced cells. All three K4DT cell lines and one lung-derived SV40 cell line were virtually immortalized and nearly maintained the normal diploid karyotypes. However, the two other heart-derived SV40 cell lines had aberrant karyotypes and the young bat-derived cell line stopped proliferating at approximately 40 population doublings. These bat cell lines are valuable for studying pathogen genomics and biology.

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.

HPV E6 inhibits E6AP to regulate epithelial homeostasis by modulating keratinocyte differentiation commitment and YAP1 activation

Human papillomaviruses (HPV) cause persistent infections by modulating epithelial homeostasis in cells of the infected basal layer. Using FUCCI and cell-cell competition assays, we have identifed regulatory roles for E6AP and NHERF1, which are the primary HPV11 E6 cellular targets, as well as being targets of the high-risk E6 proteins, in processes governing epithelial homeostasis (i.e. cell density, cell cycle entry, commitment to differentiation and basal layer delamination). Depletion of E6AP, or expression of HPV11 or 16E6 increased keratinocyte cell density and cell cycle activity, and delayed the onset of differentiation; phenotypes which were conspicuously present in HPV11 and 16 infected patient tissue. In line with proposed E6 functions, in HPV11 condyloma tissue, E6AP and NHERF1 were significantly reduced when compared to uninfected epithelium. In experimental systems, loss of HPV11 E6/E6AP binding abolished 11E6's homeostasis regulatory functions, while loss of E6/NHERF1 binding reduced the cell density threshold at which differentiation was triggered. By contrast, a NHERF1-binding mutant of 16E6 was not compromised in its homeostasis functions, while E6AP appeared essential. RNA sequencing revealed similar transcriptional profiles in both 11 and 16E6-expressing cells and E6AP-/- cells, with YAP target genes induced, and keratinocyte differentiation genes being downregulated. HPV11 E6-mediated Yap activation was observed in 2D and 3D (organotypic raft) cell culture systems and HPV-infected lesions, with both NHERF1, which is a regulator of the Hippo and Wnt pathways, and E6AP, playing an important role. As the conserved binding partner of Alpha group HPV E6 proteins, the precise role of E6AP in modulating keratinocyte phenotype and associated signalling pathways has not previously been defined. Our study suggests a model in which the preserved functions of the low and high-risk Alpha E6 proteins modulate epithelial homeostasis via E6AP activity, and lead to alteration of multiple downstream pathways, including those involving NHERF1 and YAP.

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.

Immortalized Canine Adipose-Derived Mesenchymal Stem Cells as a Novel Candidate Cell Source for Mesenchymal Stem Cell Therapy

Mesenchymal stem cells are expected to be a cell source for stem cell therapy of various diseases in veterinary medicine. However, donor-dependent cell heterogenicity has been a cause of inconsistent therapeutic efficiency. Therefore, we established immortalized cells from canine adipose tissue-derived mesenchymal stem cells (ADSCs) to minimize cellular heterogeneity by reducing the number of donors, evaluated their properties, and compared them to the primary cells with RNA-sequencing. Immortalized canine ADSCs were established by transduction with combinations of the R24C mutation of human cyclin-dependent kinase 4 (CDKR24C), canine cyclin D1, and canine TERT. The ADSCs transduced with CDK4R24C, cyclin D1, and TERT (ADSC-K4DT) or with CDK4R24C and cyclin D1 (ADSC-K4D) showed a dramatic increase in proliferation (population doubling level >100) without cellular senescence compared to the primary ADSCs. The cell surface markers, except for CD90 of the ADSC-K4DT and ADSC-K4D cells, were similar to those of the primary ADSCs. The ADSC-K4DT and ADSC-K4D cells maintained their trilineage differentiation capacity and chromosome condition, and did not have a tumorigenic development. The ability to inhibit lymphocyte proliferation by the ADSC-K4D cells was enhanced compared with the primary ADSCs and ADSC-K4DT cells. The pathway analysis based on RNA-sequencing revealed changes in the pathways mainly related to the cell cycle and telomerase. The ADSC-K4DT and ADSC-K4D cells had decreased CD90 expression, but there were no obvious defects associated with the decreased CD90 expression in this study. Our results suggest that ADSC-K4DT and ADSC-K4D cells are a potential novel cell source for mesenchymal stem cell therapy.

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.

KAv-1 is Better Suited to Chick Fibroblast Culture than DMEM or 199 Media

Cultured cells are a useful resource for poultry scientists, since these cells allow scientists to evaluate biological responses to conditions such as infectious diseases in vitro while mimicking the whole-body response in birds. However avian cell culture requires an optimized basal medium, and there are currently relatively few options for this basal medium (medium 199 and KAv-1). This means that there is still room for the development of an optimal basal medium for avian cell culture. Here we compare KAv-1 medium, Dulbecco's modified Eagle medium (DMEM) and medium 199 during the culture of chick fibroblasts and determine that KAv-1 remains the optimal medium for these assays. Our results show that DNA damage is reduced in fibroblasts cultured in the KAv-1 medium, when compared to both DMEM and Medium 199 and that these cells also display improved growth dynamics in KAv-1 medium when compared to both DMEM and medium 199. To the best of our knowledge, this is the first study to describe a comparative analysis of culture media for avian cells, which would provide useful information for poultry scientists.

Establishment and genetic characterization of cell lines derived from proliferating nasal polyps and sinonasal inverted papillomas

To better understand the pathogenesis of nasal polyps (NPs) and sinonasal inverted papillomas (SIPs), we aimed to establish cell lines from fresh tissues of NPs and SIPs and characterize them. Primary cell cultures were obtained from two NP tissues (NP2 and NP3) and one SIP tissue (IP4). All the cells were polygonal in shape, expressed cytokeratin 14, and had normal diploid chromosome status. HPV58 DNA was detected in NP3. To obtain immortal primary cells, NP2 and IP4 cells were transduced with a combination of mutant CDK4, cyclinD1 and TERT. These cells were thereafter named NP2/K4DT and IP4/K4DT, respectively. HPV58-positive NP3 cells were transduced with TERT alone, the resulting cells named NP3/T. Phenotypic and genotypic identity of original tissues and derived cells was investigated. All the cell cultures with transgenes were confirmed to be derived from their parental cells and primary tumor tissues by analysis of short tandem repeats (STR) and maintained in vitro growth, genetic profiles and gene expression characteristics of the primary cells. These virtually immortalized cells, as well as the primary cells, have potential as in vitro models for studying the pathogenesis of NPs and SIPs and for preclinical study to develop new therapeutic agents.

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.

Combinatorial expression of cell cycle regulators is more suitable for immortalization than oncogenic methods in dermal papilla cells

The immortalized cell is an essential research tool that uses robust growth properties for the functional investigation of gene products. Immortalized mammalian cells have mainly been established using three methods: expression of simian vacuolating virus 40 T antigen (the SV40 method); human papilloma virus-derived oncoprotein E6/E7 (the E6/E7 method); or combinatorial expression of R24C mutant cyclin-dependent kinase 4, cyclin D1, and telomerase reverse transcriptase (the K4DT method). However, it is unclear as to which method is optimal for an in vitro model. Here, we compared the biological characteristics and genome-wide expression profiles of immortalized human dermal papilla cells generated by the SV40, E6/E7, or K4DT method. To our knowledge, this is the first study to comprehensively compare expression profiles to determine the optimal immortalization method for maintaining the original nature of the wild-type cells. These data would be valuable to scientists aiming to establish new immortalized cell lines.

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.

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

[This corrects the article DOI: 10.1371/journal.pone.0221364.].

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.