Immortalization of Fetal Bovine Colon Epithelial Cells by Expression of Human Cyclin D1, Mutant Cyclin Dependent Kinase 4, and Telomerase Reverse Transcriptase: An In Vitro Model for Bacterial Infection

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.

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.

Establishment methods and research progress of livestock and poultry immortalized cell lines: A review

An infinite cell line is one of the most favored experimental tools and plays an irreplaceable role in cell-based biological research. Primary cells from normal animal tissues undergo a limited number of divisions and subcultures in vitro before they enter senescence and die. On the contrary, an infinite cell line is a population of non-senescent cells that could proliferate indefinitely in vitro under the stimulation of external factors such as physicochemical stimulation, virus infection, or transfer of immortality genes. Cell immortalization is the basis for establishing an infinite cell line, and previous studies have found that methods to obtain immortalized cells mainly included physical and chemical stimulations, heterologous expression of viral oncogenes, increased telomerase activity, and spontaneous formation. However, some immortalized cells do not necessarily proliferate permanently even though they can extend their lifespan compared with primary cells. An infinite cell line not only avoids the complicated process of collecting primary cell, it also provides a convenient and reliable tool for studying scientific problems in biology. At present, how to establish a stable infinite cell line to maximize the proliferation of cells while maintaining the normal function of cells is a hot issue in the biological community. This review briefly introduces the methods of cell immortalization, discusses the related progress of establishing immortalized cell lines in livestock and poultry, and compares the characteristics of several methods, hoping to provide some ideas for generating new immortalized cell lines.

Establishment of bovine 3D enteroid-derived 2D monolayers

Three-dimensional (3D) intestinal enteroids are powerful in vitro models for studying intestinal biology. However, due to their closed structure direct access to the apical surface is impeded, limiting high-throughput applications of exogenous compounds and pathogens. In this study, we describe a method for generating confluent 2D enteroids from single-cell suspensions of enzymatically-dissociated ileum-derived bovine 3D enteroids. Confluent monolayers were first achieved using IntestiCult media but to establish a defined, cost-effective culture media, we also developed a bovine enteroid monolayer (BEM) medium. The monolayers cultured in BEM media proliferated extensively and formed confluent cell layers on both Matrigel-coated plastic plates and transwell inserts by day 3 of culture. The 2D enteroids maintained the epithelial cell lineages found in 3D enteroids and ileum tissue. In addition, the monolayers formed a functional epithelial barrier based on the presence of the adherens and tight junction proteins, E-cadherin and ZO-1, and electrical resistance across the monolayer was measured from day 3 and maintained for up to 7 days in culture. The method described here will provide a useful model to study bovine epithelial cell biology with ease of access to the apical surface of epithelial cells and has potential to investigate host-pathogen interactions and screen bioactive compounds.

Assessing Intestinal Health. In Vitro and Ex vivo Gut Barrier Models of Farm Animals: Benefits and Limitations

Animal performance is determined by the functionality and health of the gastrointestinal tract (GIT). Complex mechanisms and interactions are involved in the regulation of GIT functionality and health. The understanding of these relationships could be crucial for developing strategies to improve animal production yields. The concept of "gut health" is not well defined, but this concept has begun to play a very important role in the field of animal science. However, a clear definition of GIT health and the means by which to measure it are lacking. In vitro and ex vivo models can facilitate these studies, creating well-controlled and repeatable conditions to understand how to improve animal gut health. Over the years, several models have been developed and used to study the beneficial or pathogenic relationships between the GIT and the external environment. This review aims to describe the most commonly used animals' in vitro or ex vivo models and techniques that are useful for better understanding the intestinal health of production animals, elucidating their benefits and limitations.

Ammonia-based enrichment and long-term propagation of zone I hepatocyte-like cells

Ammonia has a cytotoxic effect and can therefore be used as a selection agent for enrichment of zone I hepatocytes. However, it has not yet been determined whether ammonia-treated hepatocyte-like cells are able to proliferate in vitro. In this study, we employed an ammonia selection strategy to purify hepatocyte-like cells that were differentiated from human embryonic stem cells (ESCs) and from induced pluripotent stem cells (iPSCs). The resistance to cytotoxicity or cell death by ammonia is likely attributable to the metabolism of ammonia in the cells. In addition to ammonia metabolism-related genes, ammonia-selected hepatocytes showed increased expression of the cytochrome P450 genes. Additionally, the ammonia-selected cells achieved immortality or at least an equivalent life span to human pluripotent stem cells without affecting expression of the liver-associated genes. Ammonia treatment in combination with in vitro propagation is useful for obtaining large quantities of hepatocytes.

Farm Animal-derived Models of the Intestinal Epithelium: Recent Advances and Future Applications of Intestinal Organoids

Farm animals play an important role in translational research as large animal models of the gastrointestinal (GI) tract. The mechanistic investigation of zoonotic diseases of the GI tract, in which animals can act as asymptomatic carriers, could provide important information for therapeutic approaches. In veterinary medicine, farm animals are no less relevant, as they can serve as models for the development of diagnostic and therapeutic approaches of GI diseases in the target species. However, farm animal-derived cell lines of the intestinal epithelium are rarely available from standardised cell banks and, in addition, are not usually specific for certain sections of the intestine. Immortalised porcine or bovine enterocytic cell lines are more widely available, compared to goat or sheep-derived cell lines; no continuous cell lines are available from the chicken. Other epithelial cell types with intestinal section-specific distribution and function, such as goblet cells, enteroendocrine cells, Paneth cells and intestinal stem cells, are not represented in those cell line-based models. Therefore, intestinal organoid models of farm animal species, which are already widely used for mice and humans, are gaining importance. Crypt-derived or pluripotent stem cell-derived intestinal organoid models offer the possibility to investigate the mechanisms of inter-cell or host-pathogen interactions and to answer species-specific questions. This review is intended to give an overview of cell culture models of the intestinal epithelium of farm animals, discussing species-specific differences, culture techniques and some possible applications for intestinal organoid models. It also highlights the need for species-specific pluripotent stem cell-derived or crypt-derived intestinal organoid models for promotion of the Three Rs principles (replacement, reduction and refinement).

Characterization of bovine ileal epithelial cell line for lectin binding, susceptibility to enteric pathogens, and TLR mediated immune responses

In this study, primary and immortalized bovine intestinal epithelial cells (BIECs) were characterized for the expression of surface carbohydrate moieties. Primary BIEC-c4 cells showed staining greater than 90 % for 16 lectins but less than 50 % staining for four lectins. Immortalized BIECs showed significantly different lectin binding profile for few lectins compared to BIEC-c4 cells. BIEC-c4 cells were studied for infectivity to E. coli, Salmonella enterica, bovine rotavirus, bovine coronavirus, and bovine viral diarrhea virus. Bovine strain E. coli B41 adhered to BIEC-c4 cells and Salmonella strains S. Dublin and S. Mbandaka showed strong cell invasion. BIEC-c4 cells were susceptible to bovine rotavirus. LPS stimulation upregulated IL-10, IL-8, and IL-6 expression and Poly I:C upregulated TLR 8 and TLR 9 expression. This study provides important knowledge on the glycoconjugate expression profile of primary and immortalized BIECs and infectivity and immune responses of primary BIECs to bacterial and viral pathogens or ligands.

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.

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.

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.

Development of in vitro enteroids derived from bovine small intestinal crypts

Cattle are an economically important domestic animal species. In vitro 2D cultures of intestinal epithelial cells or epithelial cell lines have been widely used to study cell function and host-pathogen interactions in the bovine intestine. However, these cultures lack the cellular diversity encountered in the intestinal epithelium, and the physiological relevance of monocultures of transformed cell lines is uncertain. Little is also known of the factors that influence cell differentiation and homeostasis in the bovine intestinal epithelium, and few cell-specific markers that can distinguish the different intestinal epithelial cell lineages have been reported. Here we describe a simple and reliable procedure to establish in vitro 3D enteroid, or "mini gut", cultures from bovine small intestinal (ileal) crypts. These enteroids contained a continuous central lumen lined with a single layer of polarized enterocytes, bound by tight junctions with abundant microvilli on their apical surfaces. Histological and transcriptional analyses suggested that the enteroids comprised a mixed population of intestinal epithelial cell lineages including intestinal stem cells, enterocytes, Paneth cells, goblet cells and enteroendocrine cells. We show that bovine enteroids can be successfully maintained long-term through multiple serial passages without observable changes to their growth characteristics, morphology or transcriptome. Furthermore, the bovine enteroids can be cryopreserved and viable cultures recovered from frozen stocks. Our data suggest that these 3D bovine enteroid cultures represent a novel, physiologically-relevant and tractable in vitro system in which epithelial cell differentiation and function, and host-pathogen interactions in the bovine small intestine can be studied.

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.

Establishment and characterization of cell lines derived from complete hydatidiform mole

Gestational trophoblastic diseases (GTDs) are a group of diseases characterized by abnormal cellular proliferation of atypical trophoblasts. A hydatidiform mole is an abnormal pregnancy caused by genetic fertilization disorders, and it can be classified as a complete hydatidiform mole (CHM) or a partial hydatidiform mole. The aim of this study was to establish cell lines from CHMs and to characterize the cells for future studies concerning GTD. HMol1-2C, HMol1-3B, HMol1-8 and HMol3-1B were established from primary cultures of CHM explants following the introduction of different combinations of genes including human telomerase reverse transcriptase (hTERT), a mutant form of CDK (CDK4R24C), cyclin D1, p53C234, MYC and HRAS. HMol1-2C, HMol1-3B, and HMol3-1B were confirmed to originate from trophoblasts of androgenic, homozygous CHMs. These three cell lines exhibited low human chorionic gonadotropin secretion, low migration and invasion abilities, and the potential to differentiate into syncytiotrophoblastic cells via forskolin treatment. These results suggest that these cells exhibit characteristics of trophoblastic cells, especially cytotrophoblastic cells. HMol1-8 was found to consist of diploid cells and originated from maternal cells, suggesting that they were derived from decidual cells. In conclusion, we successfully established three cell lines from CHMs by introduction of hTERT and other genes. Analysis revealed that the genetic origin of each cell line was identical with that of the original molar tissue, and the cell lines exhibited characteristics of trophoblastic cells, which are similar to undifferentiated cytotrophoblasts.

A novel method to generate single-cell-derived cancer-associated fibroblast clones

BACKGROUND

Cancer-associated fibroblasts (CAFs) communicate with cancer cells to play important roles in tumor progression. However, CAFs have heterogeneous phenotypes and functions. To understand how much of this heterogeneity relates to different biological responses, a more efficient method of generating single-cell-derived CAF clones is required.

METHOD

We transduced two primary CAF cultures (CAFs-608 and CAFs-621) from lung adenocarcinoma with human telomerase reverse transcriptase (hTERT), mutant forms of cyclin dependent kinase 4 (CDK4R24C) independently and in combination (hTERT/CDK4R24C). After live imaging of each sorted-single cell, we evaluated the numbers of successfully established clones from CAFs-hTERT, CAFs-CDK4R24C, and CAFs-hTERT/CDK4R24C. Furthermore, we examined the expression levels of genes associated with tumor promoting pathways in established clones by qRT-PCR.

RESULTS

Overexpression of hTERT and CDK4R24C efficiently extended the lifespan of both CAFs-608 and CAFs-621. The number of established CAF clones was highest for CAFs-hTERT/CDK4R24C, with 57 and 62 clones established from CAFs-608 and CAFs-621, respectively. Conversely, 16 and 11 CAFs-hTERT clones were derived from CAFs-608 and CAFs-621, respectively and 10 and 8 CAFs-CDK4R24C clones were from CAFs-608 and CAFs-621, respectively. TGF-b, ATCA2, and HSF1 mRNA levels differed in individual clones established from CAFs-hTERT/CDK4R24C. The expression levels of ATCA2 and HSF1 were much higher in one clone than in the other established clones and the parental CAFs.

CONCLUSION

Our results show that combined exogenous expression of hTERT and mutant CDK4 is an effective method to generate single-cell-derived CAF clones. This provides an innovative and suitable approach to investigate the heterogeneous function and phenotype of CAFs.

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

Lowland Anoa has become endangered due to hunting and human activity. Protection and breeding of endangered species in a controlled environment is the best way of conservation. However, it is not possible to adopt this approach for all endangered species because of the cost involved and the ever-increasing number of critically endangered species. In consideration of these limitations to the conventional conservation methods, we established a primary cell culture of endangered buffalo (Lowland Anoa, Bubalus quarlesi), for the preservation of this biological resource. In addition, we introduced human derived, mutant cyclin dependent kinase 4 (CDK4), Cyclin D, and telomerase reverse transcriptase (TERT) into the primary cells. The successful introduction of these three genes was confirmed by western blot with specific antibodies, and enzymatic activity. We also showed that the expression of mutant CDK4, Cyclin D, and TERT allows us to efficiently establish an immortalized cell line, with an intact chromosome pattern, from Lowland Anoa. To the best of our knowledge, this study is the first investigation that established an immortalized cell line of an endangered wild animal species.

Functional structure and antimicrobial activity of persulcatusin, an antimicrobial peptide from the hard tick Ixodes persulcatus

Background

Antimicrobial peptides (AMPs) are considered promising candidates for the development of novel anti-infective agents. In arthropods such as ticks, AMPs form the first line of defense against pathogens in the innate immune response. Persulcatusin (IP) was found in the Ixodes persulcatus midgut, and its amino acid sequence was reported. However, the complete structure of IP has not been identified. We evaluated the relation between structural features and antimicrobial activity of IP, and its potential as a new anti-methicillin-resistant Staphylococcus aureus (MRSA) agent.

Methods

The structure of IP was predicted using homology modeling and molecular dynamics. IP and other tick AMPs were synthesized using a solid-phase method and purified by high-performance liquid chromatography. Methicillin-susceptible S. aureus (MSSA) and MRSA were used for the minimum inhibitory concentration (MIC) test and short-time killing assay of IP and other tick peptides. The influence of IP on mammalian fibroblasts and colon epithelial cells and each cell DNA and its hemolytic activity towards human erythrocytes were also examined.

Results

In the predicted IP structure, the structure with an S-S bond was more stable than that without an S-S bond. The MIC after 24 h of incubation with IP was 0.156–1.25 μg/mL for MSSA and 0.625–2.5 μg/mL for MRSA. Compared with the mammalian antimicrobial peptide and other tick peptides, IP was highly effective against MRSA. Moreover, IP showed a dose-dependent bactericidal effect on both MSSA and MRSA after 1 h of incubation. IP had no observable effect on mammalian cell growth or morphology, on each cell DNA and on human erythrocytes.

Conclusions

We predicted the three-dimensional structure of IP and found that the structural integrity was maintained by three S-S bonds, which were energetically important for the stability and for forming α helix and β sheet. IP has cationic and amphipathic properties, which might be related to its antimicrobial activity. Furthermore, the antimicrobial activity of IP against MRSA was stronger than that of other antimicrobial peptides without apparent damage to mammalian and human cells, demonstrating its possible application as a new anti-MRSA medicine.