Subcloning the MAC-T bovine mammary epithelial cell line: morphology, growth properties, and cytogenetic analysis of clonal cells

On the Biocompatibility and Teat Retention of In Situ Gelling Intramammary Formulations: Cattle Mastitis Prevention and Treatment

Treatment and prevention of cattle mastitis remains a formidable challenge due to the anatomical and physiological constraints of the cow udder. In this study, we investigated polymeric excipients and solvents that can form, (when combined) novel, non-toxic and biocompatible in situ gelling formulations in the mammary gland of bovine cattle. We also report on a new approach to screen intramammary formulations using fresh excised cow teats. Fourteen hydrophilic polymers and six solvents were evaluated for in vitro cytotoxicity and biocompatibility towards cultured bovine mammary epithelial cells (MAC-T), microscopic and macroscopic examination upon contact with excised cow teats. No significant cytotoxicity (p > 0.05) was observed with polyethylene oxides, hydroxypropyl methylcellulose, carboxymethyl cellulose, sodium alginate and xanthan gum. Polycarbophil and carbopol polymers showed significantly higher cytotoxicity (p < 0.05). Concentration-dependent cytotoxicity was observed for glycerin, propylene glycol, polyethylene glycol 400, ethanol, N-methyl-2-pyrrolidone and 2-pyrrolidone, with the 2-pyrrolidone solvents showing higher cytotoxic effects (p < 0.05). In situ gelling formulations comprising hydroxypropyl methylcellulose or carboxymethyl cellulose and solvents in specific ratios were biocompatible at higher concentrations with MAC-T cells compared to alginates. All investigated formulations could undergo in situ sol-to-gel phase transformation, forming non-toxic gels with good biocompatibility in excised cow teats hence, showing potential for use as intramammary carriers for sustained drug delivery.

Sodium salicylate reduced mRNA abundance of hypoxia-associated genes in MAC-T cells

•

Sodium salicylate decreased abundance of transcripts involved in mammary development.

•

Knockdown of HIF-1α did not prevent hypoxia-induced glucose transporter 1 expression.

•

Few interactions between hypoxia and sodium salicylate were observed.

Hypoxia is an oxygen deficiency commonly found in growing tissues and is speculated to occur in the rapidly developing mammary gland in peripartum dairy cattle. Low oxygen concentrations can activate hypoxia-inducible factor-1 (HIF-1), which increases transcription of genes involved in angiogenesis (VEGFA) and glucose transport (GLUT1), among other processes. The mRNA stability of these genes is positively regulated by heterogeneous nuclear ribonucleoprotein D (HNRNPD; also known as AUF1). In our previous research, postpartum administration of sodium salicylate (SS) increased whole-lactation milk yield in multiparous cows but tended to reduce milk yield in primiparous cows. Because rapid mammary tissue development likely occurs in cows approaching first lactation, we hypothesized that SS inhibited the activation of HIF-1α and decreased transcription of downstream targets. MAC-T cells were treated with SS (100 μM) or control medium before incubation under either hypoxic (1% O₂) or normoxic conditions for 12 h. Additionally, cells were transfected with either HIF1A small interfering RNA (siRNA) or a scrambled siRNA negative control 48 h before hypoxia treatments. HIF1A, GLUT1, VEGFA, and HNRNPD were quantified relative to the internal control gene NENF. Transcript abundance was assessed using a linear mixed model with the fixed effects of SS, hypoxia, siRNA, and all 2- and 3-way interaction terms and the random effect of plate nested within hypoxia. Treatment with SS interacted with hypoxia for GLUT1, as SS reduced GLUT1 when MAC-T cells were cultured in normoxic conditions; however, no effect of SS was found in hypoxia-treated cells. Regardless of oxygen status, SS reduced HNRNPD and tended to decrease VEGFA mRNA relative to untreated cells. Hypoxia increased GLUT1, yet no effect was observed on VEGFA or HNRNPD. Small interfering RNA knocked down HIF1A, but no effect was found on GLUT1, VEGFA, or HNRNPD. In conclusion, SS reduced transcript abundance of genes involved with mammary gland development but generally did not interact with oxygen status.

Quantitative determination of histone methylation via fluorescence resonance energy transfer (FRET) technology in immortalized bovine mammary alveolar epithelial cells supplemented with methionine

Methionine (Met) is an essential precursor of S-adenosylmethionine (SAM), which is the primary methyl donor required for biological processes such as DNA and histone methylation, which alter gene expression. In dairy cows, dietary Met has been observed to exert transcriptional alterations with beneficial effects on milk biosynthesis; however, the extent of these effects via SAM remains unknown. Therefore, we evaluated the effect of Met supply on histone methylation in lysine residues K9 and K27 in the histone tail H3 via a fluorescence resonance energy transfer (FRET) system in immortalized bovine mammary alveolar epithelial cells (MACT) incubated varying concentration of Met. The histone methylation data was complemented with global DNA methylation, cellular protein synthesis, and RT-qPCR analysis of genes related to Met cycle, DNA and histone methylation, AA transporters, and protein synthesis. The histone methylation data was performed on MACT cells seeded at 30,000 cells/well in 96-well plates 24 h prior to transfection. The transfections of FRET gene reporter plasmids H3K9 and H3K27 was performed with 0.3 μL/well of Lipofectamine® 3000 and 50 ng of plasmid DNA per well. At 24 h post-transfection, cells were treated with 0, 125, 250, and 500 μM of Met, and quantification of histone methylation was performed at 0, 12, and 24 h post-treatment as well as cell viability at 24 h using CellProfiler software. An inverted microscope for live imagining (EVOS^® FL Auto) equipped with a motorized scanning stage, and an environment-controlled chamber at 37˚C and 5.0% of CO₂ was used to take 4 pictures/well at 4x magnification. A more defined response on histone methylation was observed in H3K9 than H3K27 to Met supply, where maximal histone methylation in H3K9 was observed with 125 μM of Met. This greater histone methylation in H3K9 at 125 μM was accompanied by greater cellular protein concentration. The linear increase in Met supply causes a linear decrease in global DNA methylation, while linearly upregulating genes related to the Met cycle (i.e., MAT1A, PEMT, SAHH, and MTR). The histone methylation data suggest that, to some extent, methyl-donors such as Met may affect the methylation sites, H3K9 and H3K27, and consequently causing a different epigenetic alteration. In the context of the dairy cow, further refinement to this FRET assay to study histone methylation could lead to establishing novel potential mechanisms of how dietary methyl donors may control the structural conformation of the bovine genome and, by extension, gene expression.

Intracellular invasion and survival of Brucella neotomae, another possible zoonotic Brucella species

In 1967, Brucella neotomae was first isolated from Neotoma lepida, the dessert wood rat, in Utah. With little infection data since its discovery, the zoonotic potential of this Brucella species is largely unknown. Recent reports of isolation from human cerebrospinal fluid, along with current literature suggest that B. neotomae has the ability to infect various hosts and cell types. In this report we extend the knowledge of B. neotomae ATCC 23459’s intracellular invasion and survival abilities to a variety of cell lines through gentamicin protection assays. Some of the phagocytic and epithelial cell lines from various mammalian species represent characteristics of some cell types that could be encountered by Brucella in potential hosts. It was found that B. neotomae ATCC 23459 exhibits generally lower intracellular bacterial CFUs compared to the mouse-passaged strain of B. neotomae ATCC 23459, B. suis 1330, and B. abortus 2308. Ultimately, these observations provide a small piece of the puzzle in the investigation of the breadth of B. neotomae’s pathogenic potential.

TGF-beta signalling in bovine mammary gland involution and a comparative assessment of MAC-T and BME-UV1 cells as in vitro models for its study

The goal of the dairy industry is ultimately to increase lactation persistency, which is the length of time during which peak milk yield is sustained. Lactation persistency is determined by the balance of cell apoptosis and cell proliferation; when the balance is skewed toward the latter, this results in greater persistency. Thus, we can potentially increase milk production in dairy cows through manipulating apoptogenic and antiproliferative cellular signaling that occurs in the bovine mammary gland. Transforming growth factor beta 1 (TGFβ1) is an antiproliferative and apoptogenic cytokine that is upregulated during bovine mammary gland involution. Here, we discuss possible applications of TGFβ1 signaling for the purposes of increasing lactation persistency. We also compare the features of mammary alveolar cells expressing SV-40 large T antigen (MAC-T) and bovine mammary epithelial cells-clone UV1 (BME-UV1) cells, two extensively used bovine mammary epithelial cell lines, to assess their appropriateness for the study of TGFβ1 signaling. TGFβ1 induces apoptosis and arrests cell growth in BME-UV1 cells, and this was reported to involve suppression of the somatotropic axis. Conversely, there is no proof that exogenous TGFβ1 induces apoptosis of MAC-T cells. In addition to TGFβ1's different effects on apoptosis in these cell lines, hormones and growth factors have distinct effects on TGFβ1 secretion and synthesis in MAC-T and BME-UV1 cells as well. MAC-T and BME-UV1 cells may behave differently in response to TGFβ1 due to their contrasting phenotypes; MAC-T cells have a profile indicative of both myoepithelial and luminal populations, while the BME-UV1 cells exclusively contain a luminal-like profile. Depending on the nature of the research question, the use of these cell lines as models to study TGFβ1 signaling should be carefully tailored to the questions asked.

Development and validation of immortalized bovine mammary epithelial cell line as an in vitro model for the study of mammary gland functions

This study aimed to develop a bovine mammary epithelial (BME) cell line model, which provides a possibility to determine functional properties of the bovine mammary gland. The primary cell culture was derived from bovine mammary gland tissues and processed enzymatically to obtain cell colonies with epithelial-like morphology. The cultures of BME cells were purified and optimally cultured at 37 °C in DMEM/F12 medium supplemented with 10% fetal bovine serum. The BME cells were identified as epithelial cell line by the evaluating the expression of keratin-18 using immunofluorescence staining. A novel gene expression system strongly enhances the expression of telomerase, has been used to immortalize BME cell line termed hTBME cell line. Interestingly, telomerase remained active even after over 60 passages of hTBME cell line, required for immortalization of BME cells. In addition, the hTBME cell line was continuously subcultured with a spontaneous epithelial-like morphology, with a great proliferation activity, and without evidence of apoptotic and necrotic effects. Further characterization showed that hTBME cell line can be continuously propagated in culture with constant chromosomal features and without tumorigenic properties. Finally, established hTBME cell line was evaluated for mammary gland specific functions. Our results demonstrated that the hTBME cell line was able to retain functional-morphological structure, and functional differentiation by expression of beta (β)-casein as in the bovine mammary gland in vivo. Taken together, our findings suggest that the established hTBME cell line can serve as a valuable tool for the study of bovine mammary gland functions.

Impact of Heat Stress on Cellular and Transcriptional Adaptation of Mammary Epithelial Cells in Riverine Buffalo (Bubalus Bubalis)

The present study aims to identify the heat responsive genes and biological pathways in heat stressed buffalo mammary epithelial cells (MECs). The primary mammary epithelial cells of riverine buffalo were exposed to thermal stress at 42°C for one hour. The cells were subsequently allowed to recover at 37°C and harvested at different time intervals (30 min to 48 h) along with control samples (un-stressed). In order to assess the impact of heat stress in buffalo MECs, several in-vitro cellular parameters (lactate dehydrogenase activity, cell proliferation assay, cellular viability, cell death and apoptosis) and transcriptional studies were conducted. The heat stress resulted in overall decrease in cell viability and cell proliferation of MECs while induction of cellular apoptosis and necrosis. The transcriptomic profile of heat stressed MECs was generated using Agilent 44 K bovine oligonucleotide array and at cutoff criteria of ≥3-or ≤3 fold change, a total of 153 genes were observed to be upregulated while 8 genes were down regulated across all time points post heat stress. The genes that were specifically up-regulated or down-regulated were identified as heat responsive genes. The upregulated genes in heat stressed MECs belonged to heat shock family viz., HSPA6, HSPB8, DNAJB2, HSPA1A. Along with HSPs, genes like BOLA, MRPL55, PFKFB3, PSMC2, ENDODD1, ARID5A, and SENP3 were also upregulated. Microarray data revealed that the heat responsive genes belonged to different functional classes viz., chaperons; immune responsive; cell proliferation and metabolism related. Gene ontology analysis revealed enrichment of several biological processes like; cellular process, metabolic process, response to stimulus, biological regulation, immune system processes and signaling. The transcriptome analysis data was further validated by RT-qPCR studies. Several HSP (HSP40, HSP60, HSP70, HSP90, and HSPB1), apoptotic (Bax and Bcl2), immune (IL6, TNFα and NF-kβ) and oxidative stress (GPX1 and DUSP1) related genes showed differential expression profile at different time points post heat stress. The transcriptional data strongly indicated the induction of survival/apoptotic mechanism in heat stressed buffalo MECs. The overrepresented pathways across all time points were; electron transport chain, cytochrome P450, apoptosis, MAPK, FAS and stress induction of HSP regulation, delta Notch signaling, apoptosis modulation by HSP70, EGFR1 signaling, cytokines and inflammatory response, oxidative stress, TNF-alpha and NF- kB signaling pathway. The study thus identified several genes from different functional classes and biological pathways that could be termed as heat responsive in buffalo MEC. The responsiveness of buffalo MECs to heat stress in the present study clearly suggested its suitability as a model to understand the modulation of buffalo mammary gland expression signature in response to environmental heat load.

Can widely used cell type markers predict the suitability of immortalized or primary mammary epithelial cell models?

Background

Mammary cell cultures are convenient tools for in vitro studies of mammary gland biology. However, the heterogeneity of mammary cell types, e.g., glandular milk secretory epithelial or myoepithelial cells, often complicates the interpretation of cell-based data. The present study was undertaken to determine the relevance of bovine primary mammary epithelial cells isolated from American Holstein (bMEC_US) or Swiss Holstein–Friesian (bMEC_CH) cows, and of primary bovine mammary alveolar epithelial cells stably transfected with simian virus-40 (SV-40) large T-antigen (MAC-T) for in vitro analyses. This was evaluated by testing their expression pattern of cytokeratin (CK) 7, 18, 19, vimentin, and α-smooth muscle actin (α-SMA).

Results

The expression of the listed markers was assessed using real-time quantitative PCR, flow cytometry and immunofluorescence microscopy. Characteristic markers of the mesenchymal (vimentin), myoepithelial (α-SMA) and glandular secretory cells (CKs) showed differential expression among the studied cell cultures, partly depending on the analytical method used. The relative mRNA expression of vimentin, CK7 and CK19, respectively, was lower (P < 0.05) in immortalized than in primary mammary cell cultures. The stain index (based on flow cytometry) of CK7 and CK19 protein was lower (P < 0.05) in MAC-T than in bMECs, while the expression of α-SMA and CK18 showed an inverse pattern. Immunofluorescence microscopy analysis mostly confirmed the mRNA data, while partly disagreed with flow cytometry data (e.g., vimentin level in MAC-T). The differential expression of CK7 and CK19 allowed discriminating between immortal and primary mammary cultures.

Conclusions

The expression of the selected widely used cell type markers in primary and immortalized MEC cells did not allow a clear preference between these two cell models for in vitro analyses studying aspects of milk composition. All tested cell models exhibited to a variable degree epithelial and mesenchymal features. Thus, based on their characterization with widely used cell markers, none of these cultures represent an unequivocal alveolar mammary epithelial cell model. For choosing the appropriate in vitro model additional properties such as the expression profile of specific proteins of interest (e.g., transporter proteins) should equally be taken into account.

Phenotypic and functional characterization of two bovine mammary epithelial cell lines in 2D and 3D models

Immortalized bovine mammary epithelial cells (BME-UV1) and immortalized bovine mammary alveolar cells (MAC-T) have been extensively used as in vitro cell models to understand milk production in dairy cows. Precise knowledge about their phenotype and performance remains, however, unknown. This study aims to characterize MAC-T and BME-UV1 profiles when cultured in two-dimensional adherent, three-dimensional adherent (Matrigel), and three-dimensional no adherent [ultralow attachment (ULA)] supports. MAC-T and BME-UV1 were compared according to their proliferation capacities and to specific cell surface markers CD24, CD326 [epithelial cell adhesion molecule (EpCAM)], CD10, and integrin CD49f (α-6). Cytokeratin (CK14 and CK19), signal transducer and activator of transcription 5, and other proteins (occludin and cadherin-1) were analyzed. BME-UV1 in ULA support expressed higher CD49f marker. A different intensity of CD49 staining allowed the discrimination between the two cell lines in adherent condition. CD10, EpCAM, and CK19 expressions show that BME-UV1 cells have luminal capacity, while MAC-T has a myoepithelial profile with a high expression of CK14. BME-UV1 cells possess a closer committed progenitor profile due to their higher expression in aldehyde dehydrogenase and EpCAM. We observed that BME-UV1 cells have a better capacity to form spherical structures, mammospheres, in Matrigel than MAC-T, which was confirmed by the higher mammosphere area. In the ULA condition, BME-UV1 proliferated over the 6 days of culture. Taken together, our results clearly confirm the BME-UV1 luminal profile and MAC-T ductal/myoepithelial-like phenotype.

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.

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.

A proteomic analysis of the effect of growth hormone on mammary alveolar cell-T (MAC-T) cells in the presence of lactogenic hormones

The bovine mammary alveolar cell-T (MAC-T) cell line is able to uniformly differentiate and secrete casein proteins in response to dexamethasone, insulin, and prolactin and is extensively used to study bovine mammary epithelial cell (MEC) function. Somatotropin, or growth hormone (GH), has been shown to increase milk protein synthesis both in vivo and in mammary cell models and to induce cytoskeletal rearrangement in a 3T3 fibroblast cell line and a Chinese hamster ovary cell line. To identify the nature of the effects of GH in MECs cultured with lactogenic hormones, changes in global protein expression were assessed in the MAC-T cell line with the use of two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization tandem time of flight mass spectrometry. Forty proteins were differentially expressed in response to GH (P < 0.05) and were related to metabolism, the cytoskeleton, protein folding, RNA and DNA processing, and oxidant stress. These widespread changes in protein expression are indicative of a global role of GH in overall cellular differentiation that may underlie the direct modulation of milk component synthesis in MEC models that have been described to date.

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.

Cytogenetic and molecular characterization of Y isochromosome in a 63XO/64Xi(Yq) mosaic karyotype of an intersex horse

Sex chromosome aberrations commonly lead to abnormal sexual development. Here we cytogenetically and molecularly characterized Y isochromosome in an intersex horse. Blood lymphocyte analysis showed a mosaic karyotype with 96% 63,XO and 4% 64,Xi(Y) cells. Molecular analysis of the isochromosome was carried out by fluorescence in situ hybridization and polymerase chain reaction with male-specific and pseudoautosomal markers from the horse Y chromosome. We found that the isochromosome was monocentric, composed of 2 long arms, carrying 2 sets of genes of the pseudoautosomal region (PAR) and the male-specific region of the Y (MSY), including the SRY - thus being genetically equivalent to Y disomy. Sequence analysis of a 1,955-bp region including the SRY exon, the promoter and the UTRs, revealed no mutations in the aberrant Y. The presence of an intact SRY in a small proportion of cells is the proposed cause for the intersex phenotype. Given that the i(Yq) was present in a mosaic form, both post-zygotic and meiotic mechanisms of its origin were proposed. We speculated that nonmosaic 64,Xi(Yq) karyotypes might be rare or absent because of the likely instability of the i(Yq) during cell division. Genetic and phenotypic implications of Y isochromosome formation in other mammals are discussed in the light of the diversity of Y chromosome organization between species.

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.

In vitro culture and characterization of a mammary epithelial cell line from Chinese Holstein dairy cow

Background

The objective of this study was to establish a culture system and elucidate the unique characteristics of a bovine mammary epithelial cell line in vitro.

Methodology

Mammary tissue from a three year old lactating dairy cow (ca. 100 d relative to parturition) was used as a source of the epithelial cell line, which was cultured in collagen-coated tissue culture dishes. Fibroblasts and epithelial cells successively grew and extended from the culturing mammary tissue at the third day. Pure epithelial cells were obtained by passages culture.

Principal Findings

The strong positive immunostaining to cytokeratin 18 suggested that the resulting cell line exhibited the specific character of epithelial cells. Epithelial cells cultured in the presence of 10% FBS, supraphysiologic concentrations of insulin, and hydrocortisone maintained a normal diploid chromosome modal number of 2n = 60. Furthermore, they were capable of synthesizing β-casein (CSN2), acetyl-CoA carboxylase-α (ACACA) and butyrophilin (BTN1A1). An important finding was that frozen preservation in a mixture of 90% FBS and 10% DMSO did not influence the growth characteristics, chromosome number, or protein secretion of the isolated epithelial cell line.

Conclusions

The obtained mammary epithelial cell line had normal morphology, growth characteristics, cytogenetic and secretory characteristics, thus, it might represent an useful tool for studying the function of Chinese Holstein dairy cows mammary epithelial cell (CMECs).

Robertsonian translocation as a result of telomere shortening during replicative senescence and immortalization of bovine oviduct epithelial cells

We investigated chromosome (Chr) aberrations in the process of replicative senescence and immortalization of cultured bovine oviduct epithelial cells (BOEC) before and after transfecting vectors SV40 large T or human telomerase reverse transcriptase (hTERT). We found that a gradual increase in the number of metacentric chromosomes occurred during replicative senescence but not immortalization of BOEC. The accumulation of metacentric chromosomes was concomitant with decreases in the number of acrocentric autosomes, strongly suggesting that Robertsonian (Rb) translocation frequently occurred in cultured BOEC. The process was also correlated with an accumulation of extremely shortened telomeres (<4 kb). The maximum number of metacentric chromosomes reached a plateau (8.75 +/- 0.53) in the senescent BOEC (approximately 48 population doublings), and the value was stably maintained in all immortalized lines. These results suggest that not all autosomes may be involved in Rb translocation. Fluorescence in situ hybridization analysis using probes specific for Chr1, Chr29, telomeres, and x-chromosomes of bovine confirmed the presence of t(1;29) with other unidentified fused chromosomes. There was no evidence for duplication of sex chromosomes. Because no detectable fluorescence in situ hybridization signals at the centromere for telomeres were indicative of no direct integration of telomere sequences in the Rb translocated chromosomes, these results raise a possibility that Rb translocation between certain autosomes of bovine cells is partly but critically dependent upon a physical state of telomere attrition. The cells and cell lines established in this study could provide a promising system for further studies on the mechanisms of chromosomal translocation because of centromeric fusion in bovine cells.

EGFP expression in goat mammary epithelial cells

Primary culture of goat mammary gland cells was achieved by outgrowth of migrating cells from fragments of tissue. The fibroblast and epithelial cells were purified according to their different sensitivity to trypsin and the characteristics of goat mammary epithelial cells were observed under a light microscope. The results showed that the purified goat mammary epithelial cells retained normal characteristics until the 15th passage. The purified mammary epithelial cells propagated and formed a dome-like structure that resembled a nipple and was called a ‘milk orb’. The mammary epithelial cells could produce and secrete milk. There were different cell types: the majority were short shuttle-like or polygons, resembling a beehive; while some were large, flat and round; and others were elongated. The enhanced green fluorescent protein (EGFP) gene was transferred successfully into the goat mammary epithelial cells using electrotransfection, and its expression was observed under a fluoroscope.

In vivo expression of the antimicrobial defensin and lactoferrin proteins allowed by the strategic insertion of introns adequately spliced

A major limitation of conventional shuttle expression system, when cloning a bactericidal gene, is the basal expression level in bacteria, which is lethal. Although the expression level is low, the bactericidal feature inherent to the molecule leads to subsequent failure to recover intact transformants when the related gene is cloned into a conventional expression vector. Contrary to popular belief, the human cytomegalovirus immediate-early region 1 promoter (CMV), which is to date one of the most powerful promoters for eukaryotic expression, is active in bacteria. In this study, bactericidal genes were cloned into a conventional shuttle eukaryote expression vector harbouring the CMV promoter, but were interrupted with a sequence independent splicing element (SISE), thus inhibiting lethal gene expression in bacteria. The insertion strategy of the intron uses a universal restriction site-free cloning approach, which has been developed to insert a DNA fragment into a specific location of a gene, through a PCR-based cloning technique. We have found that one intervening sequence, which derives from an adenovirus, can be spliced in a mammalian system without respect to its location, thus the bactericidal protein is synthesized only when transfected into mammalian cells. Therein, lactoferrin and defensin proteins were produced in vivo without the necessity of complex expression systems. By introducing the adeno SISE within the coding sequence of the bactericidal genes, such genes can be easily synthesized in vitro through cloning into bacteria and still are able to express biologically active proteins when introduced into mammalian cells.

Role of the insulin-like growth factors and their binding proteins in lactation

Insulin-like growth factor (IGF)-I is thought to mediate a portion of the effects of bST on lactation in dairy cows. Serum concentrations of IGF-I are increased in lactating cows that were treated with bST, and IGF-I receptors are present in bovine mammary tissue. In addition, close arterial infusion of IGF-I into the mammary gland of goats increases milk yield. Little evidence exists to support a direct galactopoietic effect of IGF-I in ruminants. However, IGF-I is a potent mitogen for mammary epithelial cells and may also influence the inhibition of apoptosis of this cell type. The IGF are found in association with a family of individual binding proteins. The high affinity of the IGF for these proteins relative to the IGF receptor allows them to modulate IGF-I bioactivity in the mammary gland at the cellular level. Mammary epithelial cells synthesize multiple forms of IGF binding proteins, and one of these, IGF binding protein-3, is specifically regulated by the IGF. Stimulation of DNA synthesis by IGF-I is enhanced in bovine mammary epithelial cells that overexpress the IGF binding protein-3. These data indicate that IGF-I can stimulate the synthesis of an IGF binding protein, which enhances its own mitogenic activity. However, whether this mechanism is operative in the lactating mammary gland in vivo is unknown. Given the complexity of the interactions between the IGF and their binding proteins, more information is needed before the role of these growth factors in regulating growth, differentiation, and apoptosis of mammary epithelial cells is delineated.

An in vitro approach to ruminant mammary gland biology

This review discusses both fundamental and applied in vitro studies on ruminant mammary gland biology and summarizes progress made over the last decade in development of in vitro techniques to study growth, function and pathology of the mammary gland. The advantages and limitations of different in vitro systems are considered including explant cultures, primary cell cultures and immortalized lines of mammary-derived cells from cow, sheep and goat. The cell growth, differentiation and response to lactogenic hormones and growth factors are discussed as well as the relevance of the cell behavior in different culture conditions.

Plasminogen activator system: implications for mammary cell growth and involution

Several tissue remodeling events that require extracellular proteolysis are thought to be mediated by plasminogen activators that convert the inactive proenzyme plasminogen to active plasmin. The involvement of plasminogen activator in many biological phenomena reflects the ubiquitous presence of plasminogen and the ability of numerous cell types to synthesize plasminogen activator in a highly regulated manner. Increased plasmin and plasminogen activator in bovine milk are correlated with gradual involution (the declining phase of lactation). Treatment with bST prevented the increase in plasmin during gradual involution, indicating that bST interferes with conversion of plasminogen to plasmin. Concentrations of plasminogen activator in mammary tissue are high after cessation of milking. These results reinforce the association of the plasmin-plasminogen system with gradual involution postlactation. Recently, a role has been proposed for plasminogen activator in cell proliferation in several cellular systems. Insulin and IGF-I increased synthesis of urokinase plasminogen activator and enhanced proliferation of cultured bovine mammary epithelial cells. In contrast, phorbol myristate acetate, which increased expression of urokinase plasminogen activator mRNA by mammary epithelial and myoepithelial cells, stimulated proliferation of myoepithelial cells, but not epithelial cells. Thus, expression of plasminogen activator is not simply related to mitogenesis but is likely to serve multiple functions in bovine mammary epithelial cells.

Establishment and characterization of a bovine mammary epithelial cell line with unique properties

Clonal cell lines (BME-UV) were established from primary epithelial cells by stable transfection with a plasmid, carrying the sequence of the simian virus 40 early region mutant tsA58, encoding the thermolabile large T antigen. The BME-UV cells have undergone more than 300 population doublings and produce intranuclear large T antigen. At low confluency, growing islands of cells are apparent exhibiting the characteristic cobblestone morphology of epithelial cells. The BME-UV cells expressed functional markers such as microvilli and desmosomes and biochemical markers of mammary epithelial cells such as a repertoire of cytokeratins. The BME-UV cells are capable of synthesizing low levels of alpha-lactalbumin and alpha s1-casein (50 ng/ml of medium/24 h). One of the cell lines, BME-UV1 showed enhanced proliferation in the presence of epidermal growth factor (EGF) and insulinlike growth factor I (IGF-I). The BME-UV1 cell line is the only known bovine mammary epithelial cell line responsive to EGF. The BME-UV cells grown on collagen at low confluency are capable of developing very long projections that most likely allow for communication between cells at a distance from each other. The BME-UV cells may become a valid model system to examine bovine mammary epithelial proliferation and differentiation and cell-to-cell communication.