Characterization and Establishment of an Immortalized Rabbit Melanocyte Cell Line Using the SV40 Large T Antigen

Quantification of intraepithelial canine melanocytes in different somatic areas

BACKGROUND

In humans, the presence of an even distribution of melanocytes within the epidermal basal layer allows for uniform pigmentation in healthy and young individuals. Moreover, despite high variability in skin colours and tones, interindividual melanocyte density variability is low. However, dogs display a high intraindividual pigmentary variability in different anatomical areas.

HYPOTHESIS/OBJECTIVE

Data on canine melanocytes, including their distribution and density, are limited. This study aimed to assess melanocyte density across different anatomical areas in dogs of various breeds.

MATERIALS AND METHODS

Samples were harvested postmortem from 22 dogs of different breeds and ages. Samples were collected from the following: haired skin (back, ventral abdomen, head and pinnae), oral and conjunctival mucocutaneous junctions, oral mucosa (buccal mucosa, gingiva, palate) and nose. Immunohistochemical investigation using a cocktail containing Melan-A and SOX-10 antibodies was performed to evaluate the melanocytes:keratinocytes ratio (M:K ratio).

RESULTS

Variable melanocyte density was recorded in different anatomical areas, with a higher M:K ratio on the eyelid (median: 1:4; interquartile range [IQR]: 1:3.8-1:5.1) and on the nose (median: 1:6.5; IQR: 1:5.2-1:9.6). Lower ratios were observed on the haired skin, particularly on the head (median: 1:113.6; IQR: 1:37.8-1:255.1).

CONCLUSIONS AND CLINICAL RELEVANCE

Together with different melanocyte densities in different anatomical areas, dogs showed a high interindividual variability, particularly on haired skin. This finding could be associated with colour phenotype, sun exposure, and breed. Variable densities of melanocytes also might justify different incidence of melanocytic tumours in hyperpigmented breeds and in different somatic areas, as well as provide an increased protective effect in chronically sun-exposed areas.

Establishment and characterization of a novel immortalized human aortic valve interstitial cell line

Primary human aortic valvular interstitial cells (pHAVICs) play crucial roles in maintaining the mechanical structure and microenvironmental homeostasis of aortic valves. Pathologic processes such as inflammation, senescence, apoptosis, and metabolic disorders of valvular interstitial cells often lead to calcified aortic valve disease (CAVD). However, the lack of clinically relevant cellular models has impeded our understanding of CAVD. Here, we immortalized primary HAVICs with SV40 LTA. The iHAVICs (immortalized human aortic valvular interstitial cells) were maintained in a nonsenescent state and still had the potential to be induced into a senescent phenotype. In calcification induction experiments, iHAVICs can be induced to transform into osteogenic phenotypes via different stimuli via different pathways, accompanied by variations in different markers. In conclusion, we established and characterized a novel human immortalized aortic valve interstitial cell line as a practical in vitro experimental tool for the study of aortic valve calcification disease.

Establishment of immortalized rabbit bone marrow mesenchymal stem cells and a preliminary study of their osteogenic differentiation capability

BACKGROUND

A stable and standardized source of mesenchymal stem cells is a prerequisite for bone repair tissue engineering research and application. We aimed to establish a stable cell line of bone marrow mesenchymal stem cells from New Zealand rabbits and explore their osteogenic differentiation capacity.

METHODS

Primary rabbit bone marrow mesenchymal stem cells (RBMSCs) were isolated and immortalized via retroviral expression of SV40 Large T antigen (LTA). To assess the osteogenic differentiation capacity of the cells in vitro, we studied the alkaline phosphatase (ALP) expression level and calcium deposition in bone morphogenetic protein 9 (BMP9)-induced immortalized cells using ALP staining and quantification, as well as alizarin red staining. Ectopic bone formation by the cells was assessed using micro-computed tomography (μCT) and histological examination.

RESULTS

The immortalized cell line we established using SV40 LTA, which we termed iRBMSCs, was non-tumorigenic and maintained long-term proliferative activity. We further discovered that BMP9 (MOI = 30) effectively induced the osteogenic differentiation capacity of iRBMSCs in vitro, and there was a synergy with GelMA hydrogel in inducing osteogenic differentiation of the iRBMSCs in vivo.

CONCLUSION

We confirmed that iRBMSCs are promising as a stable cell line source for bone defect repair engineering.

Establishment of an immortalized sheep mammary epithelial cell line for studying milk fat and protein synthesis

The mammary gland, crucial for milk production in mammals, presents challenges for in vitro study due to its complex structure and limited cell lifespan. We addressed this by introducing the SV40 large T antigen into primary mammary epithelial cells (MECs) from sheep, creating an immortalized T-tag MEC line. This line, stable for over 50 passages, maintained typical epithelial cell morphology during long-term culture. Through transcriptome sequencing and validation, we discovered 3833 differentially expressed genes between MECs and T-tag MEC line, encompassing key biological processes and signaling pathways like cell cycle, p53, and cancer. The cell line, expressing MEC markers (KRT8, KRT18, proliferating cell nuclear antigen, SV40, CSN2, and acetyl-CoA carboxylase alpha), proved capable of synthesizing milk fat and protein. Despite its infinite proliferation potential, the T-tag MEC line showed no tumor formation in mice or cell migration in vitro, indicating stability. This development offers a valuable resource for studying MECs in dairy sheep, facilitating the advancement of long-term culture systems and in vitro lactation bioreactors.

Characterization and arbovirus susceptibility of cultured CERNI cells derived from sika deer (Cervus nippon)

Cervus nippon (sika deer) are widely distributed throughout eastern Asia. Deer possess a variety of antibodies against several zoonotic pathogens, indicating that they act as reservoir of zoonoses. In this study, we reported the characterization of cultured cells derived from sika deer and evaluated their susceptibility to arthropod-borne viruses to clarify their usefulness in virological studies. Cells derived from testicular tissue in Dulbecco's modified eagle medium with 16% fetal bovine serum started growing as primary cultured cells. The diploid cells consisted of 68 chromosomes, consistent with those of Japanese sika deer previously reported. The phylogenetic analysis showed the cells formed a robust clade with Japanese population of C. nippon, indicating that the cultured cells established in this study were originated from the Japanese sika deer. The cells immortalized by the simian virus 40 T-antigen were predominantly spindle-shaped cells exhibiting adhesive properties, and cultivated at 37°C and 5% CO2, which are common culture conditions for many mammalian cell lines. Western blotting analysis indicated that the cultured cells were multiple types of cells that coexist, including at least epithelial, fibroblast, and also Leydig cells. We confirmed that the cells have susceptibility to several arboviruses distributed in Japan: Getah virus, Japanese encephalitis virus, Oz virus, and severe fever with thrombocytopenia syndrome virus, but not to Tarumiz tick virus. From these results, the cells contribute to clarify the role of sika deer as a reservoir of zoonoses in nature and deer-associated experimental research at the cellular and molecular levels.

Characterization and establishment of an immortalized rabbit ovary granulosa cell line for reproductive biology experiments

Granulosa cells (GCs) are the key components of ovarian follicles and regulate the maturation, communication, growth, and development of oocytes. GCs have great potential as human therapeutic models and in livestock breeding. In this study, we established an immortalized cell line (Im-RGCs) by transforming primary rabbit granulosa cells (Pri-RGCs) with lentivirus-mediated simian virus 40 Large T (SV40LT). Morphologically, Im-RGCs were indistinguishable from Pri-RGCs and maintained intact cell structure as observed by H&E staining. Also, Im-RGCs exhibited no significant change in cell proliferation, viability, and growth. Furthermore, GC-specific markers, such as FSHR, StAR, CYP11A1, and CYP19A1, were examined by PCR, immunofluorescence, and Western blotting. ELISA and karyotype analysis showed that Im-RGCs can synthesize steroid hormones and maintain the normal number of chromosomes during the infinite passage. Furthermore, soft-agar cloning and nude mice tumorigenic experiments indicated the absence of any malignancy transformation in Im-RGCs. In conclusion, we successfully established the immortalized granulosa cell line of rabbit follicles that can be used for biological, animal husbandry, and female reproductive research.

Establishment and functional characterization of immortalized rabbit dermal papilla cell lines

Hair follicle (HF) undergo periodic growth and development in mammals, which regulated by dermal papilla cells (DPCs) are reported to play an important role in HF morphogenesis and development. However, primary DPCs have low proliferative activity, age quickly, and fresh cell isolation is both time-consuming and laborious. In this study, we introduced the SV40 large T antigen (SV40T) into dissociated early passage rabbit vibrissae DPCs with lentiviral vectors and established seven immortalized DPC lines (R-1, R-2, R-3, R-4, R-5, R-6 and R-7). These cell lines displayed early passage morphology and high alkaline phosphatase activity. RT-PCR and immunofluorescence staining showed that all the immortalized cell lines expressed the DPC markers (α-SMA, IGF1, ALPL, FGF2, BMP2 and TGFβ2), but α-SMA was only expressed well in R-3, R-4, and R-7. Furthermore, it was found that R-7 was the only line to survive beyond 50 passages. Compared to melanoma cells, R-7 did not undergo malignant transformation. Karyotyping and cell growth viability analysis illustrated that the R-7 cell line preserved the basic characteristics of primary DPCs. The R-7 DPCs established have potential application for future hair research. The study provides the theoretical basis in the cell research of HF growth and development.

Construction and Characterization of Immortalized Fibroblast Cell Line from Bactrian Camel

Immortalized cell lines with many advantages are widely used in various experimental contexts by many different labs. However, the absence of available cell lines poses difficulties for research in some species, such as camels. To establish an immortalized Bactrian camel fibroblast (iBCF) cell line and understand its biological characteristics, primary fibroblast cells from Bactrian camels were isolated and purified using enzymatic digestion in this study, and telomerase reverse transcriptase (hTERT) vectors were introduced into primary BCF (pBCF) for continuous passage to 80 generations after screening with G418. The cell morphology of different generations was examined under a microscope. Cell cycle and viability were evaluated by flow cytometry and CCK-8 assay, respectively. Cellular genes expression was monitored by qPCR, immunofluorescence, and Western blot, respectively. Chromosomes were determined by karyotyping. The results showed that like most other cells, both pBCF and iBCF were sensitive to nutrient concentrations and adapted to culture in the medium with 4.5 g/L glucose and 10% fetal bovine serum (FBS) concentration. hTERT gene was introduced and stably expressed in iBCF cells, which promoted BCF cell immortalization. The fibroblast specific marker vimentin (VIM) is expressed in both pBCF and iBCF, but epithelial marker cytokeratin18 (CK18) expression is weak in BCF cells. Proliferation and viability detection showed that hTERT-induced iBCF exhibits faster growth rates and higher viability than pBCF. Karyotyping showed that iBCF maintained the same number and morphology of chromosomes as the pBCF. This study demonstrated that we have successfully constructed an immortalized Bactrian camel fibroblast cell line, which was named BCF23. The establishment of the BCF23 cell line provides a foundation for expanding camel-related research.

Canine melanocytes: Immunohistochemical expression of melanocytic markers in different somatic areas

BACKGROUND

Melanoblasts originate in the neural crest from where they migrate to peripheral tissues and differentiate into melanocytes. Alteration during melanocyte development and life can cause different diseases, ranging from pigmentary disorders and decreased visual and auditory functions, to tumours such as melanoma. Location and phenotypical features of melanocytes have been characterised in different species, yet data on dogs are lacking.

OBJECTIVE

This study investigates the expression of melanocytic markers Melan A, PNL2, TRP1, TRP2, SOX-10 and MITF in melanocytes of selected cutaneous and mucosal surfaces of dogs.

ANIMALS

At necropsy, samples from five dogs were harvested from oral mucosa, mucocutaneous junction, eyelid, nose and haired skin (abdomen, back, pinna, head).

MATERIALS AND METHODS

Immunohistochemical and immunofluorescence analyses were performed to assess marker expression.

RESULTS

Results showed variable expression of melanocytic markers in different anatomical sites, particularly within epidermis of haired skin and dermal melanocytes. Melan A and SOX-10 were the most specific and sensitive melanocytic markers. PNL2 was less sensitive, while TRP1 and TRP2 were seldomly expressed by intraepidermal melanocytes in haired skin. MITF had a good sensitivity, yet the expression often was weak.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results indicate a variable expression of melanocytic markers in different sites, suggesting the presence of subpopulations of melanocytes. These preliminary results pave the way to understanding the pathogenetic mechanisms involved in degenerative melanocytic disorders and melanoma. Furthermore, the possible different expression of melanocyte markers in different anatomical sites could influence their sensitivity and specificity when used for diagnostic purposes.

Establishment and characterization of an immortalized bovine intestinal epithelial cell line

Primary bovine intestinal epithelial cells (PBIECs) are an important model for studying the molecular and pathogenic mechanisms of diseases affecting the bovine intestine. It is difficult to obtain and grow PBIECs stably, and their short lifespan greatly limits their application. Therefore, the purpose of this study was to create a cell line for exploring the mechanisms of pathogen infection in bovine intestinal epithelial cells in vitro. We isolated and cultured PBIECs and established an immortalized BIEC line by transfecting PBIECs with the pCI-neo-hTERT (human telomerase reverse transcriptase) recombinant plasmid. The immortalized cell line (BIECs-21) retained structure and function similar to that of the PBIECs. The marker proteins characteristic of epithelial cells, cytokeratin 18, occludin, zonula occludens protein 1 (ZO-1), E-cadherin and enterokinase, were all positive in the immortalized cell line, and the cell structure, growth rate, karyotype, serum dependence and contact inhibition were normal. The hTERT gene was successfully transferred into BIECs-21 where it remained stable and was highly expressed. The transport of short-chain fatty acids and glucose uptake by the BIECs-21 was consistent with PBIECs, and we showed that they could be infected with the intestinal parasite, Neospora caninum. The immortalized BIECs-21, which have exceeded 80 passages, were structurally and functionally similar to the primary BIECs and thus provide a valuable research tool for investigating the mechanism of pathogen infection of the bovine intestinal epithelium in vitro.

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.

CDK1 promotes the proliferation of melanocytes in Rex rabbits

BACKGROUND

The fur color constitutes one of the most important economic characteristics of fur animals and is determined by the content of melanin. A previous study has shown that the cyclin-dependent kinase 1 (CDK1) is a member of the protein kinase family, involved in forming the color of the fur in Rex rabbits. However, its effect on the melanocytes remains unclear.

OBJECTIVE

This study aimed to provide evidence for the role of CDK1 in melanogenesis.

METHODS

This study measured the expression of CDK1 in Rex rabbit skins of six coat colors using qRT-PCR. The CDK1-mediated regulation of the pigmentation-related genes and cyclin-dependent kinases were analyzed. The melanin content, proliferation, and apoptosis of the melanocytes were analyzed using the NaOH, CCK8, and Annexin V-FITC methods.

RESULTS

The CDK1 expression in the skin of the rex rabbits with different coat colors was found to be regular, and the expression level was found to be the highest in the skin of the black rex rabbits (P < 0.05). The overexpression/knockdown of CDK1 was found to significantly increase/decrease the melanin content in the melanocytes (P < 0.01). Besides, CDK1 was found to significantly promote the proliferation of the melanocyte and inhibit apoptosis (P < 0.01). Furthermore, the overexpression of CDK1 was found to significantly affect the expression of the other melanin-related genes like TYR, PMEL, DCT, as well as the mRNA expression of the cyclin-dependent kinases CDK4, CDK6, CDK8, CCNB1.

CONCLUSIONS

The results indicated that CDK1 can serve as a key gene regulating melanogenesis, melanocyte proliferation, and apoptosis, providing a new theoretical basis for studying the mechanism by which the different colors of the fur evolve in mammals.

Protective Effect of Resveratrol on Immortalized Duck Intestinal Epithelial Cells Exposed to H2O2

Resveratrol is a polyphenolic compound with anti-oxidation effects. The mechanisms underlying the antioxidant effects of resveratrol in duck intestinal epithelial cells remain unclear. The protective effects of resveratrol against oxidative stress induced by H2O2 on immortalized duck intestinal epithelial cells (IDECs) were investigated. IDECs were established by transferring the lentivirus-mediated simian virus 40 large T (SV40T) gene into small intestinal epithelial cells derived from duck embryos. IDECs were morphologically indistinguishable from the primary intestinal epithelial cells. The marker protein cytokeratin 18 (CK18) was also detected in the cultured cells. We found that resveratrol significantly increased the cell viability and activity of catalase and decreased the level of intracellular reactive oxygen species and malondialdehyde, as well as the apoptosis rate induced by H2O2 (p < 0.05). Resveratrol up-regulated the expression of NRF2, p-NRF2, p-AKT, and p-P38 proteins and decreased the levels of cleaved caspase-3 and cleaved caspase-9 and the ratio of Bax to Bcl-2 in H2O2-induced IDECs (p < 0.05). Our findings revealed that resveratrol might alleviate oxidative stress by the PI3K/AKT and P38 MAPK signal pathways and inhibit apoptosis by altering the levels of cleaved caspase-3, cleaved caspase-9, Bax, and Bcl-2 in IDECs exposed to H2O2.

Establishment of a New Cryopreservation Solution for Chimeric Antigen Receptor T Cells

Preservation and transportation are essential for the clinical application of chimeric antigen receptor T (CAR-T) cells. This study aimed to optimize a cryopreservation solution for CAR-T cells and evaluate the antitumor efficiency of CAR-T cells using this optimized solution in vitro and in vivo. First, the stability of the cryopreservation solution for CAR-T infusion was detected by the L27 (3⁷) orthogonal experiment. Subsequently, osmolality and pH were analyzed for the preservation reagent. Additionally, apoptosis and CAR expression of CAR-T cells were measured by flow cytometry, and the cytotoxicity was determined by calcein-AM staining. The results showed that cryopreservation solutions used in this study demonstrated high chemical stability, which induced only 2% CAR-T cells apoptosis in optimal solutions, which were slightly lower than other commercial solutions. Moreover, the CAR expression was not significantly affected by preservation with these solutions. There were no significant differences in the cytotoxicity between fresh and thawed CAR-T cells cryopreserved in the cryopreservation solutions in vivo and in vitro. This study developed a new cryopreservation solution for CAR-T cells, and it was safe and also had negligible effects on the CAR-T cells antitumor activity.

Immunostimulatory Activity of Synbiotics Using Lactococcus lactis SG-030 and Glucooligosaccharides from Weissella cibaria YRK005

Much attention has been recently paid to the health benefits of synbiotics, a combination of probiotics and prebiotics. In this study, synbiotics were prepared by combining lactic acid bacteria with potential as probiotics and purified glucooligosaccharides, and their immunostimulatory activity was evaluated using RAW 264.7 macrophage cells. A lactic acid bacteria strain with high antioxidant activity, acid and bile salt tolerance, adhesion to Caco-2 cells, and nitric oxide (NO) production was selected as a potential probiotic strain. The selected strain, isolated from forsythia, was identified as Lactococcus lactis SG-030. The purified glucooligosaccharides produced from Weissella cibaria YRK005 were used as prebiotics. RAW 264.7 cells were treated with synbiotics in two ways. One way was a simultaneous treatment with lactic acid bacteria and glucooligosaccharides. The other way was to pre-culture the lactic acid bacteria with glucooligosaccharides followed by treatment with synbiotic culture broth or synbiotic culture supernatant. In both cases, synbiotics synergistically increased NO production in RAW 264.7 cells. In addition, synbiotics treatment increased the expression of tissue necrosis factor-α, interleukin (IL)-1β, IL-6, and inducible nitric oxide synthase genes. Synbiotics also increased the expression of P38, extracellular signal-regulated kinases, c-Jun N-terminal kinases, phosphoinositide 3-kinase, and Akt proteins. The results confirmed that the synbiotics prepared in this study exhibited synergistic immunostimulatory activity.

Establishment and characterization of an immortalized epicardial cell line

Recently, the increasing significance of the epicardium in cardiac development and regeneration is beginning to be recognized. However, because of the small proportion of primary epicardial cells and the limited cell culture time, further research on the mechanism of epicardial cells is hindered. Here, we transfected simian virus 40 Large T (SV40-LT) into primary epicardial cells to establish an immortalized cell line, named EpiSV40. We further demonstrated that EpiSV40 can be easy to culture and has the proliferation, migration and differentiation capacities comparable to primary epicardial cells. EpiSV40 can serve as an ideal in vitro model for epicardial cell research, which will booster the study of the epicardium in cardiac development and heart regeneration.

Characterization of POU2F1 Gene and Its Potential Impact on the Expression of Genes Involved in Fur Color Formation in Rex Rabbit

The naturally colorful fur of the Rex rabbit is becoming increasingly popular in the modern textile market. Our previous study found that POU class 2 homeobox 1 gene (POU2F1) potentially affects the expression of genes involved in fur color formation in the Rex rabbit, but the function and regulation of POU2F1 has not been reported. In this study, the expression patterns of POU2F1 in Rex rabbits of various colors, as well as in different organs, were analyzed by RT-qPCR. Interference and overexpression of POU2F1 were used to identify the potential effects of POU2F1 on other genes related to fur color formation. The results show that the levels of POU2F1 expression were significantly higher in the dorsal skin of the brown and protein yellow Rex rabbits, compared with that of the black one. POU2F1 mRNAs were widespread in the tissues examined in this study and showed the highest level in the lungs. By transfecting rabbit melanocytes with an POU2F1-overexpression plasmid, we found that the POU2F1 protein was located at the nucleus, and the protein showed the classic characteristics of a transcription factor. In addition, abnormal expression of POU2F1 significantly affected the expression of pigmentation-related genes, including SLC7A11, MITF, SLC24A5, MC1R, and ASIP, revealing the regulatory roles of POU2F1 on pigmentation. The results provide the basis for further exploration of the role of POU2F1 in fur color formation of the Rex rabbit.

Establishment of A Reversibly Inducible Porcine Granulosa Cell Line

Granulosa cells (GCs) are the key components of ovarian follicles for regulating oocyte maturation. Previous established GC lines have allowed prolonged proliferation, but lost some physiological features owing to long-term immortalization. This study was to establish an induced immortal porcine GC line with reversible proliferation status by the tetracycline inducible (Tet-on) 3G system. Our conditional immortal porcine GCs (CIPGCs) line steadily propagated for at least six months and displayed primary GC morphology when cultured in the presence of 50 ng/mL doxycycline [Dox (+)]. Upon Dox withdrawal [Dox (–)], Large T-antigen expression, reflected by mCherry fluorescence, gradually became undetectable within 48 h, accompanied by less proliferation and size increase. The levels of estradiol and progesterone, and the expression of genes associated with steroid production, such as CYP11A1 (cytochrome P450 family 11), 3β-HSD (3β-hydroxysteroid dehydrogenase), StAR (steroidogenic acute regulatory protein), and CYP19A1 (cytochrome P450 family 19 subfamily a member 1), were all significantly higher in the Dox (–) group than Dox (+) group. The CIPGCs could switch into a proliferative state upon Dox induction. Interestingly, the expression of StAR and CYP19A1 in the CIPGCs (–Dox) was significantly increased by adding porcine follicular fluid (PFF) to mimic an ovary follicle environment. Moreover, PFF priming the CIPGCs in Dox (–) group resulted in similar estradiol production as that of primary GC, and enabled this cell line to respond to gonadotrophins in estradiol production. Collectively, we have established an inducible immortal porcine GC line, which offers a unique and valuable model for future research on the regulation of ovarian functions.