Lactoferrin expression in mammary epithelial cells is mediated by changes in cell shape and actin cytoskeleton

Host Antimicrobial Peptides: The Promise of New Treatment Strategies against Tuberculosis

Tuberculosis (TB) continues to be a devastating infectious disease and remerges as a global health emergency due to an alarming rise of antimicrobial resistance to its treatment. Despite of the serious effort that has been applied to develop effective antitubercular chemotherapies, the potential of antimicrobial peptides (AMPs) remains underexploited. A large amount of literature is now accessible on the AMP mechanisms of action against a diversity of pathogens; nevertheless, research on their activity on mycobacteria is still scarce. In particular, there is an urgent need to integrate all available interdisciplinary strategies to eradicate extensively drug-resistant Mycobacterium tuberculosis strains. In this context, we should not underestimate our endogenous antimicrobial proteins and peptides as ancient players of the human host defense system. We are confident that novel antibiotics based on human AMPs displaying a rapid and multifaceted mechanism, with reduced toxicity, should significantly contribute to reverse the tide of antimycobacterial drug resistance. In this review, we have provided an up to date perspective of the current research on AMPs to be applied in the fight against TB. A better understanding on the mechanisms of action of human endogenous peptides should ensure the basis for the best guided design of novel antitubercular chemotherapeutics.

Suspension of milking in dairy cows produces a transient increase in milk lactoferrin concentration and yield after resumption of milking

Lactoferrin is a multifunctional glycoprotein with a range of antimicrobial and immune-related properties that is found at >10-fold higher concentration in human milk (~1.7 g/L) relative to bovine milk (~0.15 g/L). Consumer demand is increasing for bovine lactoferrin through a wide range of nutritional and cosmetic consumer products. Increasing lactoferrin yield and concentration in bovine milk could assist in satisfying this increasing demand and may also help in increasing resistance to bovine mammary infection. Two experiments with cows in mid and late lactation were carried out to examine milking strategies to increase milk lactoferrin concentration and yield. Milking was suspended in cows normally milked twice daily, for periods of 2, 4, or 7d (mid lactation) or 2 or 4d (late lactation) after which cows were milked out and twice-daily milking resumed for 4d. In all groups, lactoferrin concentration was significantly increased during the remilking period, approaching concentrations similar to those found in human milk (~1 g/L). Lactoferrin yields were significantly higher in all treatment groups, although increasing the nonmilking period beyond 2d offered no advantage. Milk yield was lower initially after resumption of milking but recovered to preexperimental values by the fourth day of remilking in all groups, except the 4-d nonmilking group in late lactation. Milk somatic cell count was significantly elevated in all groups at the start of remilking but had substantially reduced by d 4 and reached a preexperimental level in the 2-d nonmilking group of mid-lactation cows. In summary, extended milking intervals can be used as a tool to produce a short-term increase in the concentration and yield of lactoferrin from bovine milk during established lactation, without any apparent long-term effects on milk yield and quality.

Anticancer effects of lactoferrin: underlying mechanisms and future trends in cancer therapy

Lactoferrin has been widely studied over the last 70 years, and its role in diverse biological functions is now well known and generally accepted by the scientific community. Usually, alterations of the lactoferrin gene in cells are associated with an increased incidence of cancer. Several studies suggest that exogenous treatment with lactoferrin and its derivatives can efficiently inhibit the growth of tumors and reduce susceptibility to cancer. None of these studies, however, reported a consistent outcome with regard to the mechanisms underlying the anticancer effects of lactoferrin. In this review, the association of lactoferrin with cancer is thoroughly discussed, from lactoferrin gene expression to the potential use of lactoferrin in cancer therapy. Lactoferrin cytotoxicity against several cancers is reported to occur in distinct ways under different conditions, namely by cell membrane disruption, apoptosis induction, cell cycle arrest, and cell immunoreaction. Based on these mechanisms, new strategies to improve the anticancer effects of the lactoferrin protein and/or its derivatives are proposed. The potential for lactoferrin in the field of cancer research (including as a chemotherapeutic agent in cancer therapy) is also discussed.

Effects of cell culture techniques on gene expression and cholesterol efflux in primary bovine mammary epithelial cells derived from milk and tissue

Primary bovine mammary epithelial cells (pbMEC) are often used in cell culture to study metabolic and inflammatory processes in the udder of dairy cows. The most common source is udder tissue from biopsy or after slaughter. However, it is also possible to culture them from milk, which is non-invasive, repeatable and yields less contamination with fibroblasts. Generally, not much is known about the influence of cell origin and cell culture techniques such as cryopreservation on pbMEC functionality. Cells were extracted from milk and udder tissue to evaluate if milk-derived pbMEC are a suitable alternative to tissue-derived pbMEC and to test what influence cryopreservation has. The cells were cultivated for three passages and stored in liquid nitrogen. The relative gene expression of the five target genes kappa-casein, lingual antimicrobial peptide (LAP), lactoferrin, lysozyme (LYZ1) and the prolactin receptor normalised with keratin 8 showed a tendency to decrease in the tissue cultures, but not in the milk-derived cultures, suggesting a greater influence of the cultivation process on tissue-derived cells, freezing lowered expression levels in both cultures. Overall expression of LAP and LYZ1 tended to be higher in milk cells. Cholesterol efflux was measured to compare passages one to seven in milk-derived cells. Passage number did not alter the efflux rate (p ≤ 0.05). We showed for the first time that the extraction of pbMEC from milk can be a suitable alternative to tissue extraction.

Mechanotransduction and epigenetic control in autoimmune diseases

Differentiation of epithelial cells is required to define tissue architecture and appropriate function of these cells is associated with a specific pattern of gene expression. DNA methylation, post-translational modification of histones and chromatin remodeling are nuclear mechanisms implicated in epigenetic control of gene expression. All factors relevant to tissue differentiation, including cell adhesion and shape, extracellular stimuli and transcriptional control, modulate gene expression and, thus, some of them are likely to impact on nuclear mechanisms of epigenetic control. The epithelial cells of salivary glands from Sjögren's syndrome patients display alterations in cell adhesion and shape. In this review, we summarize how these alterations are thought to lead to chromatin remodeling and, in doing so, bring about changes in transcriptional patterns. Additionally, we discuss how mechanotransduction in cells with impaired structural organization is implicated in modifying gene expression in these patients.

miR-214 regulates lactoferrin expression and pro-apoptotic function in mammary epithelial cells

Lactoferrin (Lf) is an abundantly expressed protein in human milk. Lactoferrin exhibits several important biological functions, and its expression is regulated by multiple environmental factors. Cellular endogenous factors, however, have not been extensively studied with regard to lactoferrin gene expression. In this study, we showed that lactoferrin gene expression and function are directly targeted by miR-214 in HC11 and MCF7 cells. In the lactoferrin mRNA 3 prime untranslated region (UTR) of human, mouse, rat, pig, bovine, camel, and goat species, there is a conserved region that perfectly matches the seed region of miR-214. Transfection of miR-214 mimic in HEK293 cells dose-dependently inhibited the activity of pGL3-control vector containing lactoferrin mRNA 3 prime UTR downstream of the luciferase gene. In HC11 cells, miR-214 overexpression inhibited the induction of lactoferrin expression by beta -estradiol (E2) and dexamethasone-prolactin-insulin (DPI). Furthermore, in MCF7 cells, overexpression of miR-214 markedly decreased lactoferrin expression (P lt 0.05), and inhibition of endogenous miR-214 expression increased lactoferrin expression and cellular apoptotic activities (P lt 0.05). In summary, our data showed that miR-214 is directly involved in lactoferrin expression and lactoferrin mediated cancer susceptibility (proapoptotic activities) in mammary epithelial cells.

Three-dimensional culture conditions lead to decreased radiation induced cytotoxicity in human mammary epithelial cells

For both targeted and non-targeted exposures, the cellular responses to ionizing radiation have predominantly been measured in two-dimensional monolayer cultures. Although convenient for biochemical analysis, the true interactions in vivo depend upon complex interactions between cells themselves and the surrounding extracellular matrix. This study directly compares the influence of culture conditions on radiation induced cytotoxicity following exposure to low-LET ionizing radiation. Using a three-dimensional (3D) human mammary epithelial tissue model, we have found a protective effect of 3D cell culture on cell survival after irradiation. The initial state of the cells (i.e., 2D versus 3D culture) at the time of irradiation does not alter survival, nor does the presence of extracellular matrix during and after exposure to dose, but long term culture in 3D which offers significant reduction in cytotoxicity at a given dose (e.g. approximately 4-fold increased survival at 5Gy). The cell cycle delay induced following exposure to 2 and 5Gy was almost identical between 2D and 3D culture conditions and cannot account for the observed differences in radiation responses. However the amount of apoptosis following radiation exposure is significantly decreased in 3D culture relative to the 2D monolayer after the same dose. A likely mechanism of the cytoprotective effect afforded by 3D culture conditions is the down regulation of radiation induced apoptosis in 3D structures.

Premalignant breast neoplasia: a paradigm of interlesional and intralesional molecular heterogeneity and its biological and clinical ramifications

As is well established in invasive breast disease, it is becoming increasingly clear that molecular heterogeneity, both between and within lesions, is a prevalent, distinct phenotype of premalignant lesions of the breast. Key pathways of tumorigenesis modulate critical features of premalignant lesions such as proliferation, differentiation, stress response, and even the generation of diversity. Current studies show that evaluation of these lesions may provide clinically useful information on future tumor formation as well as biological insights into the origin and functional significance of this distinct phenotype.

Gene expression in the third dimension: the ECM-nucleus connection

Decades ago, we and others proposed that the dynamic interplay between a cell and its surrounding environment dictates cell phenotype and tissue structure. Whereas much has been discovered about the effects of extracellular matrix molecules on cell growth and tissue-specific gene expression, the nuclear mechanisms through which these molecules promote these physiological events remain unknown. Using mammary epithelial cells as a model, the purpose of this review is to discuss how the extracellular matrix influences nuclear structure and function in a three-dimensional context to promote epithelial morphogenesis and function in the mammary gland.

Extracellular matrix, nuclear and chromatin structure, and gene expression in normal tissues and malignant tumors: a work in progress

Almost three decades ago, we presented a model where the extracellular matrix (ECM) was postulated to influence gene expression and tissue-specificity through the action of ECM receptors and the cytoskeleton. This hypothesis implied that ECM molecules could signal to the nucleus and that the unit of function in higher organisms was not the cell alone, but the cell plus its microenvironment. We now know that ECM invokes changes in tissue and organ architecture and that tissue, cell, nuclear, and chromatin structure are changed profoundly as a result of and during malignant progression. Whereas some evidence has been generated for a link between ECM-induced alterations in tissue architecture and changes in both nuclear and chromatin organization, the manner by which these changes actively induce or repress gene expression in normal and malignant cells is a topic in need of further attention. Here, we will discuss some key findings that may provide insights into mechanisms through which ECM could influence gene transcription and how tumor cells acquire the ability to overcome these levels of control.

Sustained co-cultivation with human placenta-derived MSCs enhances ALK5/Smad3 signaling in human breast epithelial cells, leading to EMT and differentiation

The interaction between mammary epithelial cells and their surrounding microenvironment are important in the development of the mammary gland. Thus, mesenchymal stem cells (MSCs), which retain pluripotency for various mesenchymal lineages, may provide a permissive environment for the morphologic alteration and differentiation of mammary epithelial cells. To this end, we investigated whether the interactions between mammary epithelial cells and human placenta-derived MSCs (hPMSC) affect the morphology, proliferation, and differentiation of epithelial cells in a co-culture system. We show that after co-culture with hPMSCs, human mammary epithelial cell lines (MCF-10F and HEMC) underwent significant morphologic alterations and a dramatic increase in ductal-alveolar branching, which was accompanied by a decrease or loss of the epithelial marker E-cadherin and a gain of the mesenchymal markers, alpha-SMA and vimentin. MCF-10F and HEMC proliferation was also inhibited in the presence of hPMSCs, and this retardation in growth was due to cell cycle arrest. Furthermore, in MCF-10F and HMEC cells, hPMSCs induced the production of lipid droplets, milk fat globule protein, and milk protein lactoferrin, which are markers of functional mammary differentiation. We also noticed an elevation in ALK5 and phosphorylated Smad3 protein levels upon hPMSC co-culture. Strikingly, the changes in morphology, proliferation, and differentiation were reversed by treatment with ALK5 or Smad3 knockdown in MCF-10F/hPMSC co-cultures. Collectively, our findings suggest that co-cultivation with hPMSCs leads to epithelial to mesenchymal transition (EMT) and differentiation of human breast epithelial cells through the ALK5/Smad3 signaling pathway.

Contributions of extracellular matrix signaling and tissue architecture to nuclear mechanisms and spatial organization of gene expression control

Post-translational modification of histones, ATP-dependent chromatin remodeling, and DNA methylation are interconnected nuclear mechanisms that ultimately lead to the changes in chromatin structure necessary to carry out epigenetic gene expression control. Tissue differentiation is characterized by a specific gene expression profile in association with the acquisition of a defined tissue architecture and function. Elements critical for tissue differentiation, like extracellular stimuli, adhesion and cell shape properties, and transcription factors all contribute to the modulation of gene expression and thus, are likely to impinge on the nuclear mechanisms of epigenetic gene expression control. In this review, we analyze how these elements modify chromatin structure in a hierarchical manner by acting on the nuclear machinery. We discuss how mechanotransduction via the structural continuum of the cell and biochemical signaling to the cell nucleus integrate to provide a comprehensive control of gene expression. The role of nuclear organization in this control is highlighted, with a presentation of differentiation-induced nuclear structure and the concept of nuclear organization as a modulator of the response to incoming signals.

Lactoferrin and cancer disease prevention

Lactoferrin (LF) is an iron-binding glycoprotein that is composed of the transferrin family and is predominantly found in the products of the exocrine glands located in the gateways of the digestive, respiratory, and reproductive systems, suggesting a role in the non-specific defence against invading pathogens. Additionally, several physiological roles have been attributed to LF, namely regulation of iron homeostasis, host defence against infection and inflammation, regulation of cellular growth, and differentiation and protection against cancer development and metastasis. These findings have suggested LF's great potential therapeutic use in cancer disease prevention and/or treatment, namely as a chemopreventive agent. This review looks at the recent advances in understanding the mechanisms underlying the multifunctional roles of LF and future perspectives on its potential therapeutic applications.

Lactoferrin decreases primary bovine mammary epithelial cell viability and casein expression

The concentration of lactoferrin (LTF) in milk varies during lactation, rising sharply during involution. We proposed that LTF might have a regulatory role in involution and investigated its effects in vitro on the viability of bovine mammary epithelial cells (BMEC) and on casein expression in bovine mammospheres. Mammospheres capable of milk protein expression were formed by culturing primary BMEC on extracellular matrix in the presence of lactogenic hormones. Exogenously added LTF decreased β-casein and κ-casein mRNA expression in mammospheres while transfection of a short interfering RNA (siRNA) to suppress LTF expression resulted in increased casein mRNA expression. We believe that LTF exerts its effect on casein gene expression by up-regulating interleukin-1β (IL-1β) as IL-Iβ gene expression was elevated in mammospheres treated with LTF. LTF also decreased viability of BMEC grown as monolayers and as mammospheres. Interestingly, LTF was only effective in reducing casein mRNA expression and viability in mammospheres when added at concentrations found during early involution but was inactive when used at concentrations found in milk. We suggest that LTF has a regulatory role during early involution, decreasing casein expression and reducing BMEC viability.

Induction of actin gene expression in the mosquito midgut by blood ingestion correlates with striking changes of cell shape

Ingestion of a blood meal by the female mosquito Anopheles gambiae (L., Diptera: Culicidae), results in a dramatic distention of the midgut epithelium. Here, we report that these events correlate with a transient increase of actin mRNA and protein abundance. The newly synthesized actin may provide a pool of actin protein needed to remodel epithelial cell cytoarchitecture. We also document changes in midgut epithelial cell morphology. Upon blood ingestion, the columnar cells flatten accompanied by the loss of microvilli on the lumenal side and the unfolding of the labyrinth on the basal side. These changes correlate with the large increase of epithelial surface area needed to accommodate the blood meal. Actin gene expression, actin synthesis and cell morphology all return to the pre-feeding state by 24 h after blood intake.

Extracellular matrix-regulated gene expression requires cooperation of SWI/SNF and transcription factors

Extracellular cues play crucial roles in the transcriptional regulation of tissue-specific genes, but whether and how these signals lead to chromatin remodeling is not understood and subject to debate. Using chromatin immunoprecipitation assays and mammary-specific genes as models, we show here that extracellular matrix molecules and prolactin cooperate to induce histone acetylation and binding of transcription factors and the SWI/SNF complex to the beta- and gamma-casein promoters. Introduction of a dominant negative Brg1, an ATPase subunit of SWI/SNF complex, significantly reduced both beta- and gamma-casein expression, suggesting that SWI/SNF-dependent chromatin remodeling is required for transcription of mammary-specific genes. Chromatin immunoprecipitation analyses demonstrated that the ATPase activity of SWI/SNF is necessary for recruitment of RNA transcriptional machinery, but not for binding of transcription factors or for histone acetylation. Co-immunoprecipitation analyses showed that the SWI/SNF complex is associated with STAT5, CCAAT/enhancer-binding protein beta, and glucocorticoid receptor. Thus, extracellular matrix- and prolactin-regulated transcription of the mammary-specific casein genes requires the concerted action of chromatin remodeling enzymes and transcription factors.

HSG cells differentiated by culture on extracellular matrix involves induction of S-adenosylmethione decarboxylase and ornithine decarboxylase

The human salivary gland (HSG) epithelial cell line can differentiate when cultured on extracellular matrix preparations. We previously identified >30 genes upregulated by adhesion of HSG cells to extracellular matrix. In the current studies, we examined the role of one of these genes, the polyamine pathway biosynthetic enzyme S-adenosylmethionine decarboxylase (SAM-DC) and the related enzyme, ornithine decarboxylase (ODC), on HSG cell differentiation during culture on extracellular matrix. HSG cells cultured on fibronectin-, collagen I gel-, and Matrigel-coated substrates for 12-24 h upregulated SAM-DC and ODC mRNA expression and enzyme activity compared to cells cultured on non-precoated substrates. After 3-5 days, HSG cells grown on Matrigel- or collagen I gel-coated substrates acquired a differentiated phenotype: the cells showed changes in culture morphology and increased expression of salivary gland differentiation markers (vimentin, SN-cystatin, and alpha-amylase). Further, culturing the cells on substrates precoated with an anti-beta1-integrin-antibody promoted differentiation-like changes. HSG cells cultured on collagen I- or Matrigel-coated substrates rapidly entered the cell cycle but showed decreased cell proliferation at longer times. In contrast, cell proliferation was enhanced on fibronectin-coated substrates compared to cells on non-precoated substrates. Treatment with the polyamine synthesis inhibitors, difluoromethylornithine (DFMO), and methylglyoxal bis-(guanylhydrazone) (MGBG), inhibited cell proliferation and delayed (3)H-thymidine incorporation in HSG cells cultured on all of the substrates. Further, inclusion of DFMO and MGBG inhibited or delayed acquisition of the differentiated phenotype in HSG cells cultured on Matrigel- or collagen I gel-coated substrates. This suggests that the adhesion-dependent expression of SAM-DC and ODC contributes to extracellular matrix-dependent HSG cell differentiation.

Cryopreserved bovine mammary cells to model epithelial response to infection

Mammary gland epithelial cells are likely to be important effectors in defending against mastitis, yet little is known about their response mechanisms. Here, we describe a cryopreserved bovine mammary epithelial cell model to study the infection response. Primary cell cultures from four Holstein cows were prepared, and frozen after two passages. The cell cultures from each cow were then thawed and maintained separately, yet simultaneously, and exposed to treatments that included infection with Staphylococcus aureus or exposure to LPS from Escherichia coli. A clear inflammatory response was shown by a significant (P < 0.05), dose dependent, increase of lactoferrin and IL-8 secretion within 24h in response to S. aureus or LPS. Marked increases (P < 0.05) in lactoferrin, TNF-alpha and serum amyloid A (SAA) mRNA expression were also observed. The results indicate the usefulness of our model to study infection responses of mammary epithelial cells, where all cells are simultaneously exposed to the same infection pressure. These responses can be studied over time, and most importantly, biological replication is provided by the four different genotypes being investigated individually. Finally, the results indicate that mammary epithelial cells play an important role in inflammatory response, through the production of pro-inflammatory cytokines, an acute phase protein, and lactoferrin.

Collagen-IV and laminin-1 regulate estrogen receptor alpha expression and function in mouse mammary epithelial cells

The expression level and functional activity of estrogen receptor alpha is an important determinant of breast physiology and breast cancer treatment. However, it has been difficult to identify the signals that regulate estrogen receptor because cultured mammary epithelial cells generally do not respond to estrogenic signals. Here, we use a combination of two- and three-dimensional culture systems to dissect the extracellular signals that control endogenous estrogen receptor alpha. Its expression was greatly reduced when primary mammary epithelial cells were placed on tissue culture plastic; however, the presence of a reconstituted basement membrane in combination with lactogenic hormones partially prevented this decrease. Estrogen receptor alpha expression in primary mammary fibroblasts was not altered by these culture conditions, indicating that its regulation is cell type specific. Moreover, estrogen receptor-dependent reporter gene expression, as well as estrogen receptor alpha levels, were increased threefold in a functionally normal mammary epithelial cell line when reconstituted basement membrane was added to the medium. This regulatory effect of reconstituted basement membrane was reproduced by two of its components, collagen-IV and laminin-1, and it was blocked by antibodies against alpha2, alpha6 and beta1 integrin subunits. Our results indicate that integrin-mediated response to specific basement membrane components, rather than cell rounding or cell growth arrest induced by reconstituted basement membrane, is critical in the regulation of estrogen receptor alpha expression and function in mammary epithelial cells.

5'-flanking regions of camel milk genes are highly similar to homologue regions of other species and can be divided into two distinct groups

The concentrations of individual casein and whey proteins in camel milk differ markedly to respective protein concentrations in bovine milk. The ratio of beta-casein to kappa-casein is considerably higher in camel milk. beta-Lactoglobulin is absent, but whey acidic protein and peptidoglycan recognition protein have been detected. Genomic sequences upstream to milk-protein genes, which are known to regulate the expression of milk proteins to a great extent, were determined for 10 camel milk-protein genes and compared to respective sequences in other mammals. Multiple sequence alignment showed closest relationships to homologous sequences from other mammals. Comparison of milk protein regulative regions revealed two distantly related groups with pronouncedly different transcription factor site probabilities. The GC-content in sequences of the first group was considerably higher than in sequences of the second group and combined occurrence of CAAT and TATAA boxes was rare, suggesting that the first group represented mostly the housekeeping gene type, probably regulated by cellular signal transduction pathways, whereas the second group helped to regulate genes specifically expressed in terminally differentiated cells of the lactating alveolar epithelium. A core region of the composite response element, which primarily controls milk protein gene activity, was found by a search for elements conserved within all 5'-flanking sequences analyzed, and it is assumed, that the presence of this element determines gene expression in the lactating mammary gland, and binding sites for general activator and repressor factors, surrounding the milk protein gene specific element, are important for regulation of gene activity.

Lactoferrin gene expression and regulation: an overview

Lactoferrin is highly conserved among human, mouse, bovine, and porcine species. The numbers of amino acids encoded by 15 of the 17 exons in these species are identical, and in 12 locations, they have identical codon interruptions at the intron-exon splice junctions. However, lactoferrin expression is both ubiquitous and species, tissue, and cell-type specific. It is differentially regulated through multiple signaling pathways such as steroid hormone, growth factor, and kinase cascade pathways. Comparing the lactoferrin gene promoters from different species, common and different characteristics are observed. The human, mouse, bovine, porcine, and bubaline (African antelope) promoters all contain a noncanonical TATA box with an adjacent Sp1 site. Both human and mouse have multiple steroid hormone response elements, while none are found in the other species studied, suggesting that the lactoferrin gene is differentially regulated among different species by steroid hormones. Several transcription factors have been identified that are crucial for the expression of the lactoferrin gene during differentiation of the myeloid cells and in estrogen and epidermal growth factor regulation. This article provides an overview on lactoferrin expression and regulation in different species.

Initial interaction of U2OS cells with noncoated and calcium phosphate coated titanium substrates

From previous studies, we know that calcium phosphate (CaP) coated implants stimulate bone formation compared to uncoated implants. Nevertheless, the mechanism by which substrate surface characteristics affect cell function is unclear. In this study, we examined the initial interaction (30 min to 24 h) of U2OS cells with titanium substrates with or without a CaP coating. The effect of substrate roughness was also studied. When cell attachment was studied, we found that cells attached more readily to rough than to smooth surfaces. Also, more cells attached to the uncoated than to the CaP coated surface. After 24 h, cell numbers were similar for all substrate surfaces. Further, cells spread to a larger area on noncoated titanium than on the CaP coated substrates. At 24 h, the sequence of cell size was smooth titanium > rough titanium > CaP coated titanium. Shape measurements showed differences in cell shape between the cells on the different materials only at 7 h, not at different culture times. Cells expressed alpha2, alpha3, alpha5, alpha6, alphav, and beta1 subunits. Expression of alpha1, alpha4, alphavbeta3, beta3, beta4, and beta7 was extremely low or was not found. The beta1 integrin expression was higher on the coated than on the noncoated titanium at 3 h, but not on the other studied times. Expression of alpha2, alpha5, alpha6, and alphav expression was found to be upregulated at 24 h compared to earlier culture times on coated titanium, but not on uncoated titanium substrates. From this we conclude that the surface characteristics of a material (roughness and composition) can affect the initial interaction of cells with the material.

Initial interaction of rat bone marrow cells with non-coated and calcium phosphate coated titanium substrates

Initial interactions of rat bone marrow (RBM) cells with smooth titanium, rough titanium or calcium phosphate coated substrates were tested. Cells were seeded onto the substrates, and attachment, integrin expression and spreading and morphology were studied. We found no difference in attachment of RBM cells to the different materials. We did find differences in the percentage of attached cells within a certain time between replicate runs of the experiments. RBM cells on all materials express alpha1, alpha3, alpha5, alpha6 and beta1 subunits. Again there was a large difference in expression patterns on RBM cells in different runs. No difference was found in expression on the various materials. For alpha1, alpha5, alpha6 and beta1, no difference was found in expression between attached and unattached cells. Expression of alpha3 was similar on attached and unattached cells during early culture. At the end of culture, alpha3 expression was downregulated for attached cells and not for unattached cells. This resulted in a higher expression of alpha3 for unattached cells compared to attached cells. Cells did spread on all materials, and reached a larger cell size on smooth titanium than on the rough materials. Morphology of the cells on the materials differed. On smooth titanium, cells usually showed a compact cell body with short cellular extensions. On the rough materials, cells often showed elongated shapes, with many thin cellular extensions. From this we conclude that the substrate surface characteristics of the materials we used do not influence attachment or integrin expression during the initial cell-material interactions. On the other hand, spreading behavior and cell morphology do depend on substrate surface characteristics.

PMC42, a novel model for the differentiated human breast

Cultured human breast carcinoma cell lines are important models for investigating the pathogenesis of breast cancer. Their use, however, is limited because of loss of expression of breast-specific markers and the development of a dedifferentiated phenotype after continuous culture. PMC42 is a unique human breast carcinoma line, previously shown to express secretory and myoepithelial markers. We have induced PMC42 cells to form hollow organoids in culture, similar to in vivo breast structures, using a combination of hormones including estrogen, progesterone, dexamethasone, insulin, and prolactin in combination with a permeable extracellular matrix. The organoids comprised polarized cells located around a central lumen. Expression of beta-casein was demonstrated in cells within organoids using reverse transcriptase-polymerase chain reaction, Western blot analysis, and confocal immunofluorescence. In this in vitro system, milk-specific gene expression was induced through hormone and matrix interactions which may be similar to those operating in vivo. PMC42 is a novel model for investigations into the molecular mechanisms of carcinogenesis and differentiation in the human breast.

Phosphatidylinositol 3-kinase is required for adherens junction-dependent mammary epithelial cell spheroid formation

Adherens junctions facilitate and maintain epithelial cell-cell adhesion. This is true of mammary epithelial cells, both in two dimensional monolayers and in three-dimensional basement membrane cultures. Using the immortalized, functional mouse mammary epithelial scp2 cell line, we found that pharmacological inhibition of phosphatidylinositol 3-kinase (PI3-kinase) disrupted adherens junctions. In monolayers, this disruption was associated with decreased E-cadherin and beta-catenin at sites of cell-cell contact and decreased association of both proteins with the cytoskeleton. Changes in the distribution of f-actin after PI3-kinase inhibition suggest that this disruption of adherens junctions may be mediated by alterations to the cytoskeleton. In basement membrane cultures, PI3-kinase inhibition reversibly prevented adherens junction-dependent spheroid formation and differentiative milk protein gene expression, both in scp2 cells and in a second mouse mammary epithelial cell line, EpH4. Decreasing the calcium concentration in the culture medium produced similar, although less dramatic, phenotypic effects. These data indicate that adherens junctions contribute, at least in part, to the efficient induction of basement membrane-dependent differentiation of mammary epithelial cells.

Perturbation of the actin cytoskeleton induces PAI-1 gene expression in cultured epithelial cells independent of substrate anchorage

Perturbation of cellular architecture with agents that alter cytoskeletal organization provides a means to assess the relationship between cell shape and gene expression. Induced transcription of the plasminogen activator inhibitor type-1 (PAI-1) gene in serum-free cultures of normal rat kidney (NRK-52E) cells following disruption of actin microfilament structures with cytochalasin D (CD) provides a simple model to probe mechanisms underlying shape-related expression control. Transition from the typical flat epithelial cell shape to an "arborized" phenotype was a concomitant of the PAI-1 inductive response. Stimulated expression occurred rapidly (i.e., within 2 h of CD addition), involved increases in both PAI-1 mRNA abundance and de novo protein synthesis, and was dependent upon the concentration of CD used. A series of culture conditions were designed (e.g., use of bacteriological surfaces, poly-HEMA coated surfaces, maintenance in suspension on agarose) to discriminate cell shape from adhesive influences on CD-stimulated PAI-1 expression. Cytoskeletal disruption, and not simply changes in cell shape, was a critical aspect of CD-mediated PAI-1 expression in NRK cells cultured under serum-free conditions; induced expression was independent of substrate anchorage. Low concentrations of CD (1-2 microM) failed to cause cell arborization or increase either relative PAI-1 mRNA/protein abundance levels suggesting, however, that cell rounding may be a necessary but not sufficient aspect in CD-mediated PAI-1 induction. Transfection of PAI-1 promoter-CAT reporter constructs into NRK cells followed by stimulation with CD or serum additionally indicated that CD-induced PAI-1 expression did not utilize the same functional complement of serum-responsive promoter sequences, thus, further defining differences in the growth factor- and cytoskeletal-mediated pathways of PAI-1 gene regulation.

Sialomucin complex (rat Muc4) is regulated by transforming growth factor beta in mammary gland by a novel post-translational mechanism

Sialomucin complex (SMC, rat Muc4) is a heterodimeric glycoprotein complex consisting of a mucin subunit ASGP-1 (for ascites sialoglycoprotein-1) and a transmembrane subunit ASGP-2, produced from a single gene and precursor. SMC expression is tightly regulated in mammary gland; the level in lactating mammary gland is about 100-fold that in virgin gland. In rat mammary epithelial cells, SMC is post-transcriptionally regulated by Matrigel by inhibition of SMC precursor synthesis. SMC is also post-transcriptionally regulated by transforming growth factor-beta (TGFbeta). The repression of SMC expression by TGFbeta is rapid, is independent of TGFbeta-induced cell cycle arrest, and does not require new protein synthesis. Unlike Matrigel, TGFbeta does not reduce SMC protein synthesis, as SMC precursor accumulation is equivalent in TGFbeta-treated and untreated cells. Instead, SMC precursor in TGFbeta-treated cells is more persistent and does not become processed as rapidly into mature ASGP-1 and ASGP-2, indicating that TGFbeta disrupts processing of SMC precursor. These results indicate that SMC, a product of normal mammary gland and milk, is regulated by TGFbeta by a novel post-translational mechanism. Thus, SMC is regulated by multiple post-transcriptional mechanisms, which serve to repress potential deleterious effects of overexpression.

Protein adsorption and cell attachment to patterned surfaces

To better understand the events involved in the generation of defined tissue architectures on biomaterials, we have examined the mechanism of attachment of human bone-derived cells (HBDC) to surfaces with patterned surface chemistry in vitro. Photolithography was used to generate alternating domains of N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) and dimethyldichlorosilane (DMS). At 90 min after seeding, HBDC were localized preferentially to the EDS regions of the pattern. Using sera specifically depleted of adhesive glycoproteins, this spatial organization was found to be mediated by adsorption of vitronectin (Vn) from serum onto the EDS domains. In contrast, fibronectin (Fn) was unable to adsorb in the face of competition from other serum components. These results were confirmed by immunostaining, which also revealed that both Vn and Fn were able to adsorb to EDS and DMS regions when coated from pure solution, i.e., in the absence of competition. In this situation, each protein was able to mediate cell adhesion across a range of surface densities. Cell spreading was constrained on the EDS domains, as indicated by cell morphology and the lack of integrin receptor clustering and focal adhesion formation. This spatial constraint may have implications for the subsequent expression of differentiated function.

Differentiation of separated mouse mammary luminal epithelial and myoepithelial cells cultured on EHS matrix analyzed by indirect immunofluorescence of cytoskeletal antigens

We have previously demonstrated that purified virgin mouse mammary luminal epithelial and myoepithelial cells promiscuously express cell type-specific cytokeratins when they are cloned in vitro. Changes in cytokeratin expression may be indicators of the loss or change of the differentiated identity of a cell. To investigate the factors that may be responsible for the maintenance of differentiated cellular identity, specifically cell-cell and cell-matrix interactions, we cloned flow-sorted mouse mammary epithelial cells on the extracellular matrix (ECM) derived from the Engelbreth-Holm-Swarm murine sarcoma (EHS matrix). Changes in cell differentiation on EHS, compared with culture on glass, were analyzed by comparing patterns of cytokeratin expression. The results indicate that ECM is responsible for maintenance of the differentiated identity of basal/myoepithelial cells and prevents the inappropriate expression of luminal antigens seen on glass or plastic. Luminal cell identity in the form of retention of luminal markers and absence of basal/myoepithelial antigens, on the contrary, appears to depend on homotypic cell-cell contacts and interactions. The results also show that luminal cells (or a subpopulation of them) can generate a cell layer that expresses only basal cytokeratin markers (and no luminal cytokeratin markers) and may form a pluripotent compartment. (J Histochem Cytochem 47:1513-1524, 1999)

Regulation of lactoferrin gene expression by estrogen and epidermal growth factor: molecular mechanism

Lactoferrin (LF) is a member of the transferrin gene family. Its expression in the mouse uterus is regulated by estrogen and epidermal growth factor (EGF). The author et al. cloned the LF gene promoter/enhancer region, and demonstrated that multihormone signaling pathways are involved in modulating LF gene activity. Three short but complex modules, within 400 bp from the transcription initiation site of the mouse LF gene, contain the response elements that are responsible for estrogen, retinoic acid, mitogen, and growth factor stimulation. These elements have been identified and characterized, using reporter constructs transiently transfected into human endometrial carcinoma RL95-2 cells. The author et al. used molecular approaches, such as deletion, insertion, and site-directed mutagenesis, to determine the relationship between the response elements, and to fine-map the crucial nucleotides within them. This article reviews the characterization of the estrogen and EGF response elements of the mouse LF gene promoter.

Secretion of prosaposin, a multifunctional protein, by breast cancer cells

Western blotting and immunodetection with three antibodies were used to probe conditioned media of breast cancer cells (MDA231, MDA435, MCF-7) for prosaposin, a lysosomal protein that occurs in milk. It was readily detected in media from these cells, and from that of an sv40-transformed mammary epithelial cell, HBL100, but not from medium of human neural tumor cells (SK-N-MC). In cultures of MCF-7 cells, the prosaposin pattern of secretion over time closely resembled that of procathepsin D, another lysosomal protein occurring in milk. Supplementing medium with 17beta-estradiol (0. 1-100 nM) dose dependently increased secretion of both proteins after 48 h without changes in cell viability. The influence of 17beta-estradiol on secretion could play a role in the trophic activity of prosaposin in cellular differentiation and cell death protection. In concert with other lysosomal proteins in the tumor environment, such as procathepsin D, prosaposin may be a factor in eliminating barriers to tumor metastasis by facilitating hydrolysis of membrane glycolipids. The number of milk proteins known to be secreted by breast cancer cells is growing. There is evidence that at least some of these may be secreted in an endocrine manner in the normal, non-lactating breast.

Cellular control lies in the balance of forces

Mechanical tension generated within the cytoskeleton of living cells is emerging as a critical regulator of biological function in diverse situations ranging from the control of chromosome movement to the morphogenesis of the vertebrate brain. In this article, we review recent advances that have been made in terms of understanding how cells generate, transmit and sense mechanical tension, as well as how they use these forces to control their shape and behavior. An integrated view of cell regulation that incorporates mechanics and structure as well as chemistry is beginning to emerge.

Effect of substratum on growth, cell morphology and lactoferrin synthesis and secretion in bovine mammary cell culture

The role of extracellular matrix in morphology, growth and lactoferrin synthesis and secretion in bovine mammary cells from a developing gland is poorly defined. In this study, bovine mammary cells from a hormone-primed developing gland were isolated and cultured on plastic, collagen, embedded within collagen, or on EHS-matrix, with the hormones prolactin, insulin, and cortisol in the presence or absence of fetal calf serum. Mammary cells on plastic or collagen spread and formed confluent cells sheets, while those embedded within collagen or on EHS-matrix maintained their acinar-like structure. Histological and ultrastructural analysis of cells showed that cells on plastic and collagen grew in multilayers, while those embedded within collagen or on EHS-matrix lacked any lumen structure. The ultrastructure of cells on different substrata more resembled an undifferentiated phenotype. Mammary cells secreted lactoferrin in increasing concentrations throughout the culture period. The total amount secreted in culture was regulated by extracellular matrix and fetal calf serum. Cells embedded within collagen in serum-free cultures secreted the lowest amounts of lactoferrin (up to 619 ng/ml; day 14), while those on collagen and supplemented with fetal calf serum secreted up to 4920 ng/ml at day 14. Fetal calf serum induced higher lactoferrin secretion within each substratum on which the cells were cultured. No intracellular accumulation of lactoferrin was noted in cells on plastic or collagen or those embedded within collagen, whereas those on EHS-matrix accumulated more than 500 ng/ml of lactoferrin intracellularly/intracinarly. Furthermore, when cultured on a similar substratum, cells from a developing gland secreted higher lactoferrin than cells from a lactating gland.