Establishment and initial characterization of the ovine mammary epithelial cell line NISH

Genetically modified animals for use in biopharmacology: from research to production

Introduction: In this review, the analysis of technologies for obtaining biologically active proteins from various sources is carried out, and the comparative analysis of technologies for creating producers of biologically active proteins is presented. Special attention is paid to genetically modified animals as bioreactors for the pharmaceutical industry of a new type. The necessity of improving the technology of development transgenic rabbit producers and creating a platform solution for the production of biological products is substantiated.

The advantages of using TrB for the production of recombinant proteins: The main advantages of using TrB are the low cost of obtaining valuable complex therapeutic human proteins in readily accessible fluids, their greater safety relative to proteins isolated directly from human blood, and the greater safety of the activity of the native protein.

The advantages of the mammary gland as a system for the expression of recombinant proteins: The mammary gland is the organ of choice for the expression of valuable recombinant proteins because milk is easy to collect in large volumes.

Methods for obtaining transgenic animals: The modern understanding of the regulation of gene expression and the discovery of new tools for gene editing can increase the efficiency of creating bioreactors for animals and help to obtain high concentrations of the target protein.

The advantages of using rabbits as bioreactors producing recombinant proteins in milk: The rabbit is a relatively small animal with a short duration of gestation, puberty and optimal size, capable of producing up to 5 liters of milk per year per female, receiving up to 300 grams of the target protein.

In vitro culture and evaluation of bovine mammary epithelial cells from Ukraine dairy cows

BACKGROUND

Mammary epithelial cells (MECs) have been widely-used over the years as models to understand the physiological function of mammary disease.

AIMS

This study aimed to establish a culture system and elucidate the unique characteristics of bovine mammary epithelial cells (BMECs) from the milk of Ukraine Holstein dairy cows in order to develop a general in vitro model.

METHODS

The milk from a three-year-old lactating dairy cow was used as a source of the epithelial cell, characteristics of BMECs were examined using real time cell assay (RTCA), immunocytochemistry (ICC), reverse transcription-polymerase chain reaction (RT-PCR), and Western blot (WB).

RESULTS

The results showed that BMECs can be recovered from milk, grown in culture, and exhibit the characteristic cobblestone morphology of epithelial cells.

CONCLUSION

The established BMECs retained MEC characteristics and secreted β-caseins even when grew on plastic substratum. Thus, the established cell line had normal morphology, growth characteristics, as well as secretory characteristics, and it could be considered as a model system and useful tool for understanding the biology of dairy cow mammary glands.

Transgenic bovine as bioreactors: Challenges and perspectives

The use of recombinant proteins has increased in diverse commercial sectors. Various systems for protein production have been used for the optimization of production and functional protein expression. The mammary gland is considered to be a very interesting system for the production of recombinant proteins due to its high level of expression and its ability to perform post-translational modifications. Cows produce large quantities of milk over a long period of lactation, and therefore this species is an important candidate for recombinant protein expression in milk. However, transgenic cows are more difficult to generate due to the inefficiency of transgenic methodologies, the long periods for transgene detection, recombinant protein expression and the fact that only a single calf is obtained at the end of each pregnancy. An increase in efficiency for transgenic methodologies for cattle is a big challenge to overcome. Promising methodologies have been proposed that can help to overcome this obstacle, enabling the use of transgenic cattle as bioreactors for protein production in milk for industry.

Establishment of mammary gland model in vitro: culture and evaluation of a yak mammary epithelial cell line

This study aimed to establish yak mammary epithelial cells (YMECs) for an in vitro model of yak mammary gland biology. The primary culture of YMECs was obtained from mammary gland tissues of lactating yak and then characterized using immunocytochemistry, RT-PCR, and western blot analysis. Whether foreign genes could be transfected into the YMECs were examined by transfecting the EGFP gene into the cells. Finally, the effect of Staphylococcus aureus infection on YMECs was determined. The established YMECs retained the mammary epithelial cell characteristics. A spontaneously immortalized yak mammary epithelial cell line was established and could be continuously subcultured for more than 60 passages without senescence. The EGFP gene was successfully transferred into the YMECs, and the transfected cells could be maintained for a long duration in the culture by continuous subculturing. The cells expressed more antimicrobial peptides upon S.aureus invasion. Therefore, the established cell line could be considered a model system to understand yak mammary gland biology.

MAC-T cells as a tool to evaluate lentiviral vector construction targeting recombinant protein expression in milk

Prior to generating transgenic animals for bioreactors, it is important to evaluate the vector constructed to avoid poor protein expression. Mammary epithelial cells cultured in vitro have been proposed as a model to reproduce the biology of the mammary gland. In the present work, three lentiviral vectors were constructed for the human growth hormone (GH), interleukin 2 (IL2), and granulocyte colony-stimulating factor 3 (CSF3) genes driven by the bovine β-casein promoter. The lentiviruses were used to transduce mammary epithelial cells (MAC-T), and the transformed cells were cultured on polystyrene in culture medium with and without prolactin. The gene expression of transgenes was evaluated by PCR using cDNA, and recombinant protein expression was evaluated by Western-blotting using concentrated medium and cellular extracts. The gene expression, of the three introduced genes, was detected in both induced and non induced MAC-T cells. The human GH protein was detected in the concentrated medium, whereas CSF3 was detected in the cellular extract. Apparently, the cellular extract is more appropriate than the concentrated medium to detect recombinant protein, principally because concentrated medium has a high concentration of bovine serum albumin. The results suggest that MAC-T cells may be a good system to evaluate vector construction targeting recombinant protein expression in milk.

Lineage-specific markers of goat mammary cells in primary culture

The objective of this study was morphological and functional characterization of cells from the primary cell culture developed from lactating goat mammary gland, focusing on distribution of lineage-specific markers. Primary cells were grown on a thin layer of basement membrane matrix, a growth surface that resembles in vivo conditions. The cells in adherent conditions rapidly proliferated and showed cobblestone morphology, typical for epithelial cells. Under non-adherent conditions, goat mammary cells formed spherical, acini-like structures that resembled alveoli of lactating mammary gland. Immunofluorescence and RNA sequencing were employed to determine expression of lineage-specific markers. Presence of markers cytokeratin 14 and 18, integrin alpha 6, vimentin, estrogen receptor, smooth muscle actin, and cytokeratin 5 was detected using immunofluorescence. The greatest expression was observed for markers typical for myoepithelial cells, luminal cells, and mesenchymal cells. Based on our characterization, we can conclude that established primary culture was composed of mainly epithelial and stromal cells. These findings demonstrate that primary mammary cells express some of the most important functional and biochemical markers needed for their characterization. First, they grow in the characteristic cobblestone morphology of epithelial cells. Second, they express classical cytoplasmic network of cytokeratin fibers. Third, they express markers typical of mammary parenchyma and stroma. The established cell culture represents a good in vitro model for studies of mammary gland development, differentiation, and lactation. We suggest that herein revealed lineage markers are suitable for characterization of mammary cells of goat and possibly other mammalian species.

Validation of a recombinant human bactericidal/permeability-increasing protein (hBPI) expression vector using murine mammary gland tumor cells and the early development of hBPI transgenic goat embryos

Human bactericidal/permeability-increasing protein (hBPI) is the only antibacterial peptide which acts against both gram-negative bacteria and neutralizes endotoxins in human polymorphonuclear neutrophils; therefore, hBPI is of great value in clinical applications. In the study, we constructed a hBPI expression vector (pBC1-Loxp-Neo-Loxp-hBPI) containing the full-length hBPI coding sequence which could be specifically expressed in the mammary gland. To validate the function of the vector, in vitro cultured C127 (mouse mammary Carcinoma Cells) were transfected with the vector, and the transgenic cell clones were selected to express hBPI by hormone induction. The mRNA and protein expression of hBPI showed that the constructed vector was effective and suitable for future application in producing mammary gland bioreactor. Then, female and male goat fibroblasts were transfected with the vector, and two male and two female transgenic clonal cell lines were obtained. Using the transgenic cell lines as nuclear donors for somatic cell nuclear transfer, the reconstructed goat embryos produced from all four clones could develop to blastocysts in vitro. In conclusion, we constructed and validated an efficient mammary gland-specific hBPI expression vector, pBC1-Loxp-Neo-Loxp-hBPI, and transgenic hBPI goat embryos were successfully produced, laying foundations for future production of recombinant hBPI in goat mammary gland.

Bovine mammary epithelial cell cultures for the study of mammary gland functions

In the present study, the analysis of epithelial cells derived from various sources was undertaken, beginning from the mammary gland tissue through the primary cultures and their subsequent passages. The objective of the study was the comparative analysis of the stage in which the epithelial cells obtained from individuals in different lactation cycles and disparate phases of cell culture growth are the most suitable for morphological research and analysis of gene expression activity. The cultures of primary bovine mammary epithelial cells and passages were identified morphologically using immunocytochemical methods. After positive identification, real-time PCRs were performed for the analysis of the expression level of casein genes, whey protein genes, and butyrophilin gene. The most stable reference genes in real-time PCRs for the mammary gland tissue and cell cultures were also determined. Of the reference genes, the UXT and GAPDH genes appeared to be the most stable ones for the mammary gland tissue samples and epithelial cell cultures. The results obtained allowed concluding that the mammary gland samples collected from heifers constituted the most effective material for the initiation of primary cultures. The primary cultures formed characteristic for the mammary gland tissue dome structures, which images were obtained using confocal microscopy. The highest levels of expression of the CSN1S1, CSN1S2, CSN2, and CSN3 genes were detected in primary cultures. The levels of expression of whey protein genes (LALBA and BGL) were highest in the second passage. The most abundant expression of the BTN1A1 gene was observed in primary cultures and the third passage. On the basis of the whole experiment, it can be concluded that primary cultures and cells of the second passage derived from heifer individuals appeared to be the best materials for the analysis of mammary gland function and gene expression activity.

Isolation, characterization, and EGFP expression in the buffalo (Bubalus bubalis) mammary gland epithelial cell line

This study was aimed to establish a buffalo mammary epithelial cells (BuMECs) line and maintain it for long-term by subculturing. BuMECs isolated from lactating buffalo mammary glands were cultured on a collagen matrix gel. BuMECs expressed significant amounts of the epithelial cell specific marker cytokeratin 18 as determined by immunohistochemistry. The BuMECs displayed monolayer, cobble-stone morphology, and formed lumen-, dome-, and duct-like structures. Furthermore, they were capable of synthesizing CSN2, BLG, ACACA, and BTN1A1, showed viability after thawing and expressed milk protein genes. The enhanced green fluorescent protein gene was transferred successfully into the BuMECs using lipofection method and the transfected cells could be maintained for long-term in culture by subculturing.

Differential expression pattern of ISG15 in different tissue explants and cells induced by various interferons

Interferon stimulated gene 15 (ISG15), an ubiquitin cross-reactive protein, can conjugate to target proteins. Unlike ubiquitination, protein modification by ISG15 does not target protein for degradation, but enhances the cellular response to interferon (IFN), which plays a key role in antiviral responses. In this study, Western blot and/or immunocytochemistry were performed to explore the ISG15 expression patterns in explants of bovine endometrium, mammary gland and kidney, as well as Madin-Darby bovine kidney (MDBK), endometrial and mammary cells stimulated by IFN-α, -β, and -τ. Western blot indicated that there are differential minimum antiviral units among recombinant bovine interferon-α (rbIFN-α, 10(2) IU/mL), rbIFN-β (10(3) IU/mL) and rbIFN-τ (10(4) IU/mL) in regard to stimulating saturation expression of free and ISG15-conjugated proteins by MDBK cells and endometrial and mammary explants. These results were further confirmed through immunocytochemical analysis of MDBK, endometrial and mammary cells. For the first time it has been shown that the expression pattern of ISG15-conjugated proteins occurs in a tissue-specific manner. Furthermore, the present findings provide the first evidence of 10- to 100-fold differences in minimum antiviral units of rbIFN-α, rbIFN-β, and rbIFN-τ in regard to stimulating saturation expression of ISG15.

Establishment and characterization of a buffalo (Bubalus bubalis) mammary epithelial cell line

BACKGROUND

The objective of this study was to establish the buffalo mammary epithelial cell line (BuMEC) and characterize its mammary specific functions.

METHODOLOGY

Buffalo mammary tissue collected from the slaughter house was processed enzymatically to obtain a heterogenous population of cells containing both epithelial and fibroblasts cells. Epithelial cells were purified by selective trypsinization and were grown in a plastic substratum. The purified mammary epithelial cells (MECs) after several passages were characterized for mammary specific functions by immunocytochemistry, RT-PCR and western blot.

PRINCIPAL FINDINGS

The established buffalo mammary epithelial cell line (BuMEC) exhibited epithelial cell characteristics by immunostaining positively with cytokeratin 18 and negatively with vimentin. The BuMEC maintained the characteristics of its functional differentiation by expression of β-casein, κ-casein, butyrophilin and lactoferrin. BuMEC had normal growth properties and maintained diploid chromosome number (2n = 50) before and after cryopreservation. A spontaneously immortalized buffalo mammary epithelial cell line was established after 20 passages and was continuously subcultured for more than 60 passages without senescence.

CONCLUSIONS

We have established a buffalo mammary epithelial cell line that can be used as a model system for studying mammary gland functions.

Establishment and characterization of a lactating dairy goat mammary gland epithelial cell line

To study milk synthesis in dairy goat mammary gland, we had established an in vitro lactating dairy goat mammary epithelial cell (DGMEC) line. Mammary tissues of Guan Zhong dairy goats at 35 d of lactation were dispersed and cultured in a medium containing epithelial growth factor, insulin-like growth factor-1, insulin transferrin serum, and fetal bovine serum. Epithelial cells were enriched by digesting with 0.25% trypsin repeatedly to remove fibroblast cells and were identified as epithelial origin by staining with antibody against cytokeratine 18. The DGMECs displayed monolayer, cobble-stone, epithelial-like morphology, and formed alveoli-like structures and island monolayer aggregates which were the typical characteristics of mammary epithelial cells. A one-half logarithmically growth curve and cytoplasmic lipid droplets in these cells were observed. In this paper, we also studied the lactating function of DGMECs. Results showed that DGMECs could secrete lactose and β-casein. Lactating function of the cells had no obvious change after 48 h treated by insulin, while prolactin could obviously raise the secretion of milk proteins and lactose.

Establishment and characterization of a lactating bovine mammary epithelial cell model for the study of milk synthesis

This study sought to establish an in vitro lactating BMEC (bovine mammary epithelial cell) model, which may maintain the native function for a period of time. Mammary tissues of midlactation Holstein dairy cows were dispersed and cultured in a medium containing insulin, prolactin, hydrocortisone, transferrin, epidermal growth factor and fetal calf serum. After the cells migrating from the tissue reached approximately 80% of confluency, the tissues were removed, and secretory epithelial cells were enriched by digesting with 0.25% trypsin repeatedly to remove fibroblasts. The BMEC cells plated on plastic dishes displayed a monolayer, cobblestone, epithelial-like morphology and formed alveoli-like structures and island monolayer aggregates which are the typical characteristics of the mammary epithelial cells. The isolated cells were identified as of epithelial origin by staining with antibody against cytokeratin 18. A one-half logarithmically growth curve and abundant microvilli and cytoplasmic lipid droplets were observed in these cells. The transcription of the alphas1 casein gene and synthesis of alphas caseins were also detected in the model. Thus, our lactating BMEC model can be an effective model in vitro for studies of milk synthesis in the bovine mammary gland.

Characteristics and EGFP expression of porcine mammary gland epithelial cells

The aims of this study were to establish a porcine mammary gland epithelial (PMGE) cell line, and to determine if these PMGE cells could be maintained long-term in culture by continuous subculturing following transfection with a reporter gene, enhanced green fluorescence protein (EGFP). Primary culture of PMGE cells was achieved by outgrowth of migrating cells from the fragments of the mammary gland tissue of a lactating pig. The passage sixteen PMGE cells were transfected with EGFP gene using lipofection. The expression of Cell keratins of epithelial cells in PMGE cells was tested by immunofluorescence. Βeta-Casein gene mRNA was tested for PMGE cells by RT-PCR. The results showed that PMGE cells could form dome-like structure which looked like nipple, and the cells contained different cell types. The expression of Cell keratins demonstrated the property of epithelial cells, and the PMGE cells could express transcript encoding a Βeta-Casein protein. EGFP gene was successfully transferred into the PMGE cells, and the transfected cells could be maintained long-term in culture by continuous subculturing. In conclusion, we have established a EGFP gene transfected porcine mammary gland epithelial (ET-PMGE) cell line.

Characterization of an epithelial cell line from bovine mammary gland

Elucidation of the bovine mammary gland's unique characteristics depends on obtaining an authentic cell line that will reproduce its function in vitro. Representative clones from bovine mammary cell populations, differing in their attachment capabilities, were cultured. L-1 cells showed strong attachment to the plate, whereas H-7 cells detached easily. Cultures established from these clones were nontumorigenic upon transplantation to an immunodeficient host; they exhibited the epithelial cell characteristics of positive cytokeratin but not smooth muscle actin staining. Both cell lines depended on fetal calf serum for proliferation. They exhibited distinct levels of differentiation on Matrigel in serum-free, insulin-supplemented medium on the basis of their organization and beta-lactoglobulin (BLG) secretion. H-7 cells organized into mammospheres, whereas L-1 cells arrested in a duct-like morphology. In both cell lines, prolactin activated phosphorylation of the signal transducer and activator of transcription, Stat5-a regulator of milk protein gene transcription, and of PHAS-I-an inhibitor of translation initiation in its nonphosphorylated form. De novo synthesis and secretion of BLG were detected in differentiated cultures: in L-1 cells, BLG was dependent on lactogenic hormones for maximal induction but was less stringently controlled than was beta-casein in the mouse CID-9 cell line. L-1 cells also encompassed a near-diploid chromosomal karyotype and may serve as a tool for studying functional characteristics of the bovine mammary gland.

Establishment and characterisation of ovine blood monocyte-derived cell lines

Studies of the important functions in host defense assured by macrophages, both as functional elements and as potential targets for intracellular pathogens, are often inhibited by the lack of a source of large numbers of uniform, well-characterised cells. To address this lack for ovine studies, we have established cell lines from spontaneously-proliferating adherent mononuclear cells from sheep blood. Eight such lines which have been continuously cultured for over 400 passages have phagocytic activities and cytochemical characteristics indicating that they retain the nature of mononuclear phagocytes. They display typical functional membrane proteins such as CD14, Fc receptors and MHC class II. Such cells can facilitate in vitro studies of pathogen-monocyte interactions and can furnish copious amounts of cells for transfer experiments.

Establishment and characterization of a caprine mammary epithelial cell line (CMEC)

We describe the establishment of a continuous, nontransformed cell line obtained from primary culture of a lactating (114 days postparturition) Anglo-Nubian (Capra hircus) goat mammary gland biopsy. These cells (CMEC), have been cultured in the presence of supraphysiologic concentrations of insulin and hydrocortisone for more than 560 population doublings (over 80 passages) without any sign of senescence while maintaining a normal/near-normal diploid chromosome modal number of 2n = 60 and are responsive to contact inhibition of proliferation. Cytoskeletal analysis indicates that CMECs are epithelial, without detectable fibroblastic or myoepithelial cells. When grown at low density on plastic substratum, the cells tend to form island monolayer aggregates with the characteristic cobblestone morphology of epithelial cells. With increasing density, the cells organize into lumen-like structures with various morphology consisting of large and small vacuolized and nonvacuolized cells. Postconfluent cultures form epithelial raised dome-like structures, implying a process of contact-induced differentiation. This is corroborated by positive immunocytochemistry to lactation-specific proteins: beta-casein and alpha-lactalbumin, which were predominantly expressed in dome-forming cells. We also observed an overall modulation of cytokeratin 18/19 expression associated with number of days post subculture and with the expression of lactation-specific proteins. Postconfluent cultures which contain lactation-specific, antibody-reactive, dome-like structures showed a decreased expression of keratin 18 and no (null) expression for keratin 19. Lastly, cells cultured within a collagen matrix show morphological differentiation with the organization of branching duct-like and acini-like structures. This study suggests that CMECs are a useful in vitro model for study of mammary gland development and differentiation, in particular, direct modulation of epithelial cells grown on plastic substratum or extracellular matrix without the influence of stromal elements or the necessity and variability associated with primary cell culture or tissue explants.