Mammary gland development--It's not just about estrogen

Hormonal regulation of miRNA during mammary gland development

The mammary gland is a unique organ as most of its development occurs after birth through stages of proliferation, differentiation and apoptosis that are tightly regulated by circulating hormones and growth factors. Throughout development, hormonal cues induce the regulation of different pathways, ultimately leading to differential transcription and expression of genes involved in this process, but also in the activation or inhibition of post-transcriptional mechanisms of regulation. However, the role of microRNAs (miRNAs) in the different phases of mammary gland remodeling is still poorly understood. The objectives of this study were to analyze the expression of miRNA in key stages of mammary gland development in mice and to determine whether it could be associated with hormonal variation between stages. To do so, miRNAs were isolated from mouse mammary glands at stages of adulthood, pregnancy, lactation and involution, and sequenced. Results showed that 490, 473, 419, and 460 miRNAs are detected in adult, pregnant, lactating and involuting mice, respectively, most of them being common to all four groups, and 58 unique to one stage. Most genes could be divided into six clusters of expression, including two encompassing the highest number of miRNA (clusters 1 and 3) and showing opposite profiles of expression, reaching a peak at adulthood and valley at lactation, or showing the lowest expression at adulthood and peaking at lactation. GO and KEGG analyses suggest that the miRNAs differentially expressed between stages influence the expression of targets associated with mammary gland homeostasis and hormone regulation. To further understand the links between miRNA expression and hormones involved in mammary gland development, miRNAs were then sequenced in breast cells exposed to estradiol, progesterone, prolactin and oxytocin. Four, 38, 24 and 66 miRNAs were associated with progesterone, estradiol, prolactin, and oxytocin exposure, respectively. Finally, when looking at miRNAs modulated by the hormones, differentially expressed during mammary gland development, and having a pattern of expression that could be correlated with the relative levels of hormones known to be found in vivo, 16 miRNAs were identified as likely regulated by circulating hormones. Overall, our study brings a better understanding of the regulation of miRNAs throughout mammary gland development and suggests that there is a relationship between their expression and the main hormones involved in mammary gland development. Future studies will examine this role more in detail.

Knockdown of PROX1 promotes milk fatty acid synthesis by targeting PPARGC1A in dairy goat mammary gland

Goat milk is rich in various fatty acids that are beneficial to human health. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) and RNA-seq analyses of goat mammary glands at different lactation stages revealed a novel lactation regulatory factor, Prospero homeobox 1 (PROX1). However, the mechanism whereby PROX1 regulates lipid metabolism in dairy goats remains unclear. We found that PROX1 exhibits the highest expression level during peak lactation period. PROX1 knockdown enhanced the expression of genes related to de novo fatty acid synthesis (e.g., SREBP1 and FASN) and triacylglycerol (TAG) synthesis (e.g., DGAT1 and GPAM) in goat mammary epithelial cells (GMECs). Consistently, intracellular TAG and lipid droplet contents were significantly increased in PROX1 knockdown cells and reduced in PROX1 overexpression cells, and we observed similar results in PROX1 knockout mice. Following PROX1 overexpression, RNA-seq showed a significant upregulation of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PPARGC1A) expression. Further, PPARGC1A knockdown attenuated the inhibitory effects of PROX1 on TAG contents and lipid-droplet formation in GMECs. Moreover, we found that PROX1 promoted PPARGC1A transcription via the PROX1 binding sites (PBSs) located in the PPARGC1A promoter. These results suggest a novel target for manipulating the goat milk-fat composition and improving the quality of goat milk.

SNAT2-mediated regulation of estrogen and progesterone in the proliferation of goat mammary epithelial cells

The development of the goat mammary gland is mainly under the control of ovarian hormones particularly estrogen and progesterone (P4). Amino acids play an essential role in mammary gland development and milk production, and sodium-coupled neutral amino acid transporter 2 (SNAT2) was reported to be expressed in the mammary gland of rats and bovine mammary epithelial cells, which may affect the synthesis of milk proteins or mammary cell proliferation by mediating prolactin, 17β-estradiol (E2) or methionine function. However, whether SNAT2 mediates the regulatory effects of E2 and P4 on the development of the ruminant mammary gland is still unclear. In this study, we show that E2 and P4 could increase the proliferation of goat mammary epithelial cells (GMECs) and regulate SNAT2 mRNA and protein expression in a dose-dependent manner. Further investigation revealed that SNAT2 is abundantly expressed in the mammary gland during late pregnancy and early lactation, while knockdown and overexpression of SNAT2 in GMECs could inhibit or enhance E2- and P4-induced cell proliferation as well as mammalian target of rapamycin (mTOR) signaling. We also found that the accelerated proliferation induced by SNAT2 overexpression in GMECs was suppressed by the mTOR signaling pathway inhibitor rapamycin. This indicates that the regulation of GMECs proliferation mediated by SNAT2 in response to E2 and P4 is dependent on the mTOR signaling pathway. Finally, we found that the total content of the amino acids in GMECs changed after knocking-down and overexpressing SNAT2. In summary, the results demonstrate that the regulatory effects of E2 and P4 on GMECs proliferation may be mediated by the SNAT2-transported amino acid pathway. These results may offer a novel nutritional target for improving the development of the ruminant mammary gland and milk production.

Pre- and post-weaning nutrition status affects sheep mammary gland morphology and promotes differential gene expression

Little is known about how varying the plane of nutrition before and after weaning can influence gene expression that drives mammary gland development (MGD). Therefore, the aim of this study was to investigate this paradigm in a seasonal sheep breed. Forty pre-weaning 30-day old Kurdish female lambs were fed either a low-nutrient and protein (L; 2.0 Mcal ME/kg DM; 8.70% crude protein [CP]) or high-nutrient and protein diet (H; 2.5 Mcal ME/kg DM; 14.80% CP). At d 120 (weaning), lambs were allocated into a 2 × 2 arrangement based on pre- and post-weaning diets, resulting in four groups (LL, LH, HL, HH). On d 210, mammary biopsy samples were taken for histomorphological and gene expression studies. Alveoli were larger in HH compared with all other groups (p < 0.05). Whilst estrogen receptor-alpha, progesterone receptor, growth hormone receptor and insulin-like growth factor binding protein-1 gene expression was modulated depending on pre- or post-weaning nutritional levels (p < 0.01). Overall, a consistent high plane of nutrition promoted MGD, with more a complex relationship evident between the expression of genes critical for mammary gland function and development. These findings provide scope for future tailored nutritional strategies to optimize both liveweight gain and MGD.

Relationship between prolactin level and puberty in girls with early breast development

OBJECTIVES

Prolactin (PRL) stimulates the mammary glands development; however, it also inhibits gonadotropin-releasing hormone (GnRH) secretion. We evaluated the relationship between PRL levels and puberty in girls with precocious breast development.

METHODS

This study included 244 girls with breast development < 8 years of age. Patients were categorized as central precocious puberty (CPP) [peak luteinizing hormone (LH) levels ≥ 5 IU/L after GnRH stimulation] versus non-CPP (NPP) group. High PRL was defined as serum PRL > 17.9 ng/mL.

RESULTS

High PRL was more common in NPP than in CPP group (17.6 vs. 8.1%, p=0.025), although mean PRL levels did not differ. In NPP group, the high PRL group had lower peak LH/follicle-stimulating hormone (FSH) ratio, and later LH peak time after GnRH stimulation than normal PRL group (all p < 0.05). PRL levels of the subgroups according to the peak LH time (15, 30, 45, 60, and 90 min after GnRH stimulation) were different in NPP group, but not in CPP group. PRL levels tended to be higher as the peak LH time was delayed. High PRL was associated with decreased odds for CPP (OR=0.42, p=0.043).

CONCLUSIONS

Girls with NPP showed higher proportion of high PRL than CPP group. High PRL group showed more features of prepubertal response in NPP group, and associated with decreased odds for CPP, suggesting the possibility of PRL role on breast development while suppressing hypothalamic-pituitary-gonadal axis activation in NPP girls.

Killing two birds with one stone: Pregnancy is a sensitive window for endocrine effects on both the mother and the fetus

Pregnancy is a complex process requiring tremendous physiological changes in the mother in order to fulfill the needs of the growing fetus, and to give birth, expel the placenta and nurse the newborn. These physiological modifications are accompanied with psychological changes, as well as with variations in habits and behaviors. As a result, this period of life is considered as a sensitive window as impaired functional and physiological changes in the mother can have short- and long-term impacts on her health. In addition, dysregulation of the placenta and of mechanisms governing placentation have been linked to chronic diseases later-on in life for the fetus, in a concept known as the Developmental Origin of Health and Diseases (DOHaD). This concept stipulates that any change in the environment during the pre-conception and perinatal (in utero life and neonatal) period to puberty, can be "imprinted" in the organism, thereby impacting the health and risk of chronic diseases later in life. Pregnancy is a succession of events that is regulated, in large part, by hormones and growth factors. Therefore, small changes in hormonal balance can have important effects on both the mother and the developing fetus. An increasing number of studies demonstrate that exposure to endocrine disrupting compounds (EDCs) affect both the mother and the fetus giving rise to growing concerns surrounding these exposures. This review will give an overview of changes that happen during pregnancy with respect to the mother, the placenta, and the fetus, and of the current literature regarding the effects of EDCs during this specific sensitive window of exposure.

Hybrid Broussonetia papyrifera Fermented Feed Can Play a Role Through Flavonoid Extracts to Increase Milk Production and Milk Fatty Acid Synthesis in Dairy Goats

In order to explore the effect of hybrid Broussonetia papyrifera fermented feed on milk production and milk quality of dairy goats, and to compare with alfalfa hay, three dairy goat diets were designed based on the principle of equal energy and equal protein. The goats in the control group were fed a basic TMR diet (CG group), and the other two groups were supplemented with 10% alfalfa hay (AH group) and 10% hybrid B. papyrifera fermented feed (BP group). The results showed that the dry matter intake and milk production of BP group increased significantly. The total amount of amino acids and the content of each amino acid in the milk of AH group and BP group were lower than those of CG group. The content of saturated fatty acids in the milk of BP group decreased while the content of unsaturated fatty acids increased. The contents of prolactin, estrogen and progesterone in BP goat serum were generally higher than those of AH goat and CG goat. Subsequently, this study separated and cultured mammary epithelial cells from breast tissue, and added flavone extracted from the leaves of hybrid B. papyrifera and alfalfa to their culture medium for comparison, which is one of their important bioactive components. The results showed that low-dose alfalfa flavone (AH) and hybrid B. papyrifera flavone (BP) can increase cell viability. They also can increase the accumulation of intracellular triglyceride and the formation of lipid droplets. Both AH flavone and BP flavone significantly up-regulated the expression of genes related to milk fat synthesis, including genes related to fatty acid de novo synthesis (ACACA, FASN, and SCD1), long-chain fatty acid activation and transport related genes (ACSL1), and genes related to transcription regulation (SREBP1). The three genes related to triglyceride synthesis (DGAT1, DGAT2, and GPAM) were all significantly increased by BP flavone. Both AH flavone and BP flavone significantly increased the protein expression of progesterone receptor and estrogen receptor in mammary epithelial cells but had no effect on prolactin receptor.

Novel insights linking BRCA1-IRIS role in mammary gland development to formation of aggressive PABCs: the case for longer breastfeeding

Pregnancy-associated breast cancer (PABC) is diagnosed during or shortly after pregnancy. Although rare, PABC is a serious occurrence often of the triple negative (TNBC) subtype. Here we show progesterone, prolactin, and RANKL upregulate BRCA1-IRIS (IRIS) in separate and overlapping subpopulations of human mammary epithelial cell lines, which exacerbates the proliferation, survival, and the TNBC-like phenotype in them. Conversely, vitamin D₃ reduces IRIS expression in TNBC cell lines, which attenuates growth, survival, and the TNBC-like phenotype in them. In the mouse, Brca1-Iris (Iris, mouse IRIS homolog) is expressed at low-level in nulliparous mice, increases ~10-fold in pregnant/lactating mice, to completely disappear in involuting mice, and reappears at low-level in regressed glands. Mice underwent 3 constitutive pregnancies followed by a forced involution (after 5 days of lactation) contained ~10-fold higher Iris in their mammary glands compared to those underwent physiological involution (after 21 days of lactation). While protein extracts from lactating glands promote proliferation in IRIS^low and IRIS overexpressing (IRISOE) cells, extracts from involuting glands promote apoptosis in IRIS^low, and aneuploidy in IRISOE cells. In a cohort of breast cancer patients, lack of breastfeeding was associated with formation of chemotherapy resistant, metastatic IRISOE breast cancers. We propose that terminal differentiation triggered by long-term breastfeeding reduces IRIS expression in mammary cells allowing their elimination by the inflammatory microenvironment during physiological involution. No/short-term breastfeeding retains in the mammary gland IRISOE cells that thrive in the inflammatory microenvironment during forced involution to become precursors for aggressive breast cancers shortly after pregnancy.

Late gestation hyperthermia: epigenetic programming of daughter's mammary development and function

Exposure to stressors during early developmental windows, such as prenatally (i.e., in utero), can have life-long implications for an animal's health and productivity. The mammary gland starts developing in utero and, like other developing tissues and organs, may undergo fetal programming. Previous research has implicated factors, such as prenatal exposure to endocrine disruptors or alterations in maternal diet (e.g., maternal over or undernutrition), that can influence the developmental trajectory of the offspring mammary gland in postnatal life. However, the direct links between prenatal insults and future productive outcomes are less documented in livestock species. Research on in utero hyperthermia effects on early-life mammary development is scarce. This review will provide an overview of key developmental milestones taking place in the bovine mammary gland during the pre- and postnatal stages. We will showcase how intrauterine hyperthermia, experienced by the developing fetus during the last trimester of gestation, derails postnatal mammary gland development and impairs its synthetic capacity later in life. We will provide insights into the underlying histological, cellular, and molecular mechanisms taking place at key postnatal developmental life stages, including birth, weaning and the first lactation, that might explain permanent detriments in productivity long after the initial exposure to hyperthermia. Collectively, our studies indicate that prenatal hyperthermia jeopardizes the normal developmental trajectory of the mammary gland from fetal development to lactation. Further, in utero hyperthermia epigenetically programs the udder, and possibly other organs critical to lactation, yielding a less resilient and less productive cow for multiple lactations.

Genistein Directly Represses the Phosphorylation of STAT5 in Lactating Mammary Epithelial Cells

Genistein is a soy isoflavone and shows various physiological activities, such as affinities for estrogen receptors (ERs) and inhibitory effects on the epidermal growth factor receptor (EGFR) pathway. A previous study reported that genistein downregulates milk production ability in mammary epithelial cells (MECs) while decreasing the phosphorylation of STAT5. The ER and EGFR pathways indirectly regulate STAT5. In this study, the repressing mechanism of genistein against the phosphorylation of STAT5 was investigated using a culture model of mouse MECs with milk production ability. The results revealed that genistein did not influence the behavior of ERα and ERβ, whereas genistein immediately repressed the phosphorylation of ERK1/2. However, the decrease in phosphorylated STAT5 occurred independent of the phosphorylation of EGFR. Genistein repressed new phosphorylation of STAT5 by prolactin without influencing the phosphorylation of JAK2. In conclusion, this study indicates that genistein directly inhibits the phosphorylation of STAT5 in lactating MECs.

Supplementing lycopene combined with corn improves circulating IgG concentration in pregnant ewes and their lambs

Lycopene (C₄₀H₅₆, a non-provitamin A carotenoid) is a lipid-soluble pigment and a natural antioxidant with immunomodulatory activities. The objective of this study was to investigate the effects of lycopene with or without corn supplementation on circulating hormones, white blood cells, immunoglobulin G (IgG) concentrations, quality of colostrum in pregnant ewes, and IgG concentrations in newborn lambs. Forty multiparous single-bearing ewes (68 ± 8.4 kg body weight, mean ± SD) were fed in four groups of CONTROL (fed a basal diet (BD)), CORN (BD + 300 g/day corn), LYCOP(BD + 100 mg/day lycopene), and LYCORN (BD + 300 g/day corn + 100 mg/day lycopene). The quantity and chemical composition of colostrum were determined. Blood samples were taken from ewes right after lambing and from lambs at 3 and 24 h of age. Results showed that corn supplementation increased (P < 0.05) udder volume, the quantity of colostrum, as well as percentage of lactose, and protein in colostrum. Corn-supplemented ewes had higher circulating glucose, prolactin, and estradiol but lower urea and progesterone than control ewes. The ratio of progesterone to estradiol (P₄/E₂) in the blood of pregnant ewes decreased (P < 0.05) after corn supplementation. Lycopene, irrespective of corn, increased the percentage of lymphocyte cells in pregnant ewes. Both corn and lycopene increased circulating IgG concentrations and subsequently increased the total IgG in colostrum at 6 h post-partum. Lycopene significantly elevated the circulating IgG at 24 h of age in lambs. In conclusion, lycopene along with corn supplementation additively increased concentrations of IgG in the blood of ewes and in the colostrum, which resulted in an enhancement of passive immune transfer to the newborn lambs.

Common pathways and functional profiles reveal underlying patterns in Breast, Kidney and Lung cancers

Background

Cancer is a major health problem which presents a high heterogeneity. In this work we explore omics data from Breast, Kidney and Lung cancers at different levels as signalling pathways, functions and miRNAs, as part of the CAMDA 2019 Hi-Res Cancer Data Integration Challenge. Our goal is to find common functional patterns which give rise to the generic microenvironment in these cancers and contribute to a better understanding of cancer pathogenesis and a possible clinical translation down further studies.

Results

After a tumor versus normal tissue comparison of the signaling pathways and cell functions, we found 828 subpathways, 912 Gene Ontology terms and 91 Uniprot keywords commonly significant to the three studied tumors. Such features interestingly show the power to classify tumor samples into subgroups with different survival times, and predict tumor state and tissue of origin through machine learning techniques. We also found cancer-specific alternative activation subpathways, such as the ones activating STAT5A in ErbB signaling pathway. miRNAs evaluation show the role of miRNAs, such as mir-184 and mir-206, as regulators of many cancer pathways and their value in prognoses.

Conclusions

The study of the common functional and pathway activities of different cancers is an interesting approach to understand molecular mechanisms of the tumoral process regardless of their tissue of origin. The existence of platforms as the CAMDA challenges provide the opportunity to share knowledge and improve future scientific research and clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13062-021-00293-8.

Long Intergenic Non-Coding RNAs in the Mammary Parenchyma and Fat Pad of Pre-Weaning Heifer Calves: Identification and Functional Analysis

Enhanced plane of nutrition at pre-weaning stage can promote the development of mammary gland especially heifer calves. Although several genes are involved in this process, long intergenic non-coding RNAs (lincRNAs) are regarded as key regulators in the regulated network and are still largely unknown. We identified and characterized 534 putative lincRNAs based on the published RNA-seq data, including heifer calves in two groups: fed enhanced milk replacer (EH, 1.13 kg/day, including 28% crude protein, 25% fat) group and fed restricted milk replacer (R, 0.45 kg/day, including 20% crude protein, 20% fat) group. Sub-samples from the mammary parenchyma (PAR) and mammary fat pad (MFP) were harvested from heifer calves. According to the information of these lincRNAs' quantitative trait loci (QTLs), the neighboring and co-expression genes were used to predict their function. By comparing EH vs R, 79 lincRNAs (61 upregulated, 18 downregulated) and 86 lincRNAs (54 upregulated, 32 downregulated) were differentially expressed in MFP and PAR, respectively. In MFP, some differentially expressed lincRNAs (DELs) are involved in lipid metabolism pathways, while, in PAR, among of DELs are involved in cell proliferation pathways. Taken together, this study explored the potential regulatory mechanism of lincRNAs in the mammary gland development of calves under different planes of nutrition.

The oxytocin receptor signalling system and breast cancer: a critical review

Breast cancer is making up one-quarter of all new female cancer cases diagnosed worldwide. Breast cancer surgeries, radiation therapies, cytotoxic chemotherapies and targeted therapies have made significant progress and play a dominant role in breast cancer patient management. However, many challenges remain, including resistance to systemic therapies, tumour recurrence and metastasis. The cyclic neuropeptide oxytocin (OT) elicits a plethora of biological responses via the oxytocin receptor (OTR) in both the central and peripheral nervous system, including social bonding, stress, maternal behaviour, sexual activity, uterus contraction, milk ejection and cancer. As a typical member of the G protein-coupled receptor family, OTR represents also an intriguing target for cancer therapy. There is emerging evidence that OTR plays a role in breast cancer development and progression, and several breast cancer cell lines express OTR. However, despite supporting evidence that OT lowers breast cancer risks, its mechanistic role in breast cancer development and the related signalling pathways are not fully understood. Here, we review the current knowledge of the OT/OTR signalling system in healthy breast tissue as well as in breast cancer, and discuss OTR as a potential therapeutic target for breast cancer management.

Prolactin and Estradiol are Epigenetic Modulators in Bovine Mammary Epithelial Cells during Staphylococcus aureus Infection

Changes in the levels of reproductive hormones compromise the bovine innate immune response (IIR). Changes in 17β-estradiol (E2) and prolactin (bPRL) levels affect the IIR of bovine mammary epithelial cells (bMECs), the target tissue of these hormones. In this work, we explored the effect of the combined hormones on bMEC IIR during Staphylococcus aureus infection, and if they can modulate epigenetic marks. By gentamicin protection assays, we determined that combined hormones (bPRL (5 ng/mL) and E2 (50 pg/mL)] decrease S. aureus internalization into bMECs (~50%), which was associated with a reduction in integrin α5β1 membrane abundance (MA) (~80%) determined by flow cytometry. Additionally, combined hormones increased Toll-like receptor 2 (TLR2) MA (~25%). By RT-qPCR, we showed that combined hormones induce the expression of pro- and anti-inflammatory cytokine genes, as well as up-regulate antimicrobial peptide gene expression. The combined hormones induced H3K9Ac at 12 h of treatment, which coincides with the reduction in histone deacetylase (HDAC, ~15%) activity. In addition, hormones increased the H3K9me2 mark at 12 h, which correlates with a reduction in the expression of KDM4A. In conclusion, bPRL and E2 modulate the IIR of bMECs, an effect that can be related to the regulation of histone H3 modifications such as H3K9Ac and H3K9me2.

BRCA1 represses DNA replication initiation through antagonizing estrogen signaling and maintains genome stability in parallel with WEE1-MCM2 signaling during pregnancy

The mammary gland undergoes fast cell proliferation during early pregnancy, yet the mechanism to ensure genome integrity during this highly proliferative stage is largely unknown. We show that pregnancy triggers replicative stresses leading to genetic instability in mice carrying a mammary specific disruption of breast cancer associated gene-1 (BRCA1). The fast cell proliferation was correlated with enhanced expression of most genes encoding replisomes, which are positively regulated by estrogen/ERα signaling but negatively regulated by BRCA1. Our further analysis revealed two parallel signaling pathways, which are mediated by ATR-CHK1 and WEE1-MCM2 and are responsible for regulating DNA replication checkpoint. Upon DNA damage, BRCA1 deficiency markedly enhances DNA replication initiation and preferably impairs DNA replication checkpoint mediated by ATR and CHK1. Meanwhile, DNA damage also activates WEE1-MCM2 signaling, which inhibits DNA replication initiation and enables BRCA1-deficient cells to avoid further genomic instability. Finally, we demonstrated that overriding this defense by WEE1 inhibition in combination with cisplatin, which causes DNA damage, serves as a promising therapeutic approach for killing BRCA1-deficient cancer cells.

chi-miR-143-3p Promotes Apoptosis of Mammary Gland Epithelial Cells from Dairy Goats by Targeting Ndfip1

The mammary gland is an important organ for lactation in dairy goats. Mammary gland development and lactation functions are primarily regulated by natural hormones and certain crucial regulatory factors. Nedd4 family-interacting protein 1 (Ndfip1) can specifically bind to neural precursor cell-expressed, developmentally downregulated protein 4 (Nedd4) family members to participate in ubiquitination, which in turn regulates a range of biological processes in the body. However, the effects of Ndfip1 expression regulation at the post-transcriptional level on the development of mammary gland cells have not been previously reported. To study the regulation of Ndfip1 at post-transcriptional level, the overexpression and interference vectors of Ndfip1 were constructed, and co-transfected into the primary mammary gland epithelial cells cultured in vitro with miR-143 mimics and inhibitor. Dual luciferase reporter gene system, real-time quantitative polymerase chain reaction, western blotting, cholecystokinin octapeptide assays, and flow cytometry were used to identify their regulation and function. As a result, Ndfip1 was targeted and regulated by miR-143, which influences the development of mammary gland epithelial cells in dairy goats cultured in vitro. This study will lay an experimental foundation for further understanding the functions of Ndfip1 and miR-143.

Mammary Epithelial Cell Lineage Changes During Cow's Life

Milk production is highly dependent on the optimal development of the mammary epithelium. It is therefore essential to better understand mammary epithelial cell growth and maintenance from the related epithelial lineage during the animal life. Here, we characterized the epithelial lineage at puberty, lactation and dry-off in bovine using the cell surface markers CD49_f, CD24, and CD10. The pubertal period was characterized by a high proportion of CD49_f^pos cells corresponding to various epithelial subpopulations, notably the CD24^pos subpopulations. The proportion of CD49_f^pos cells was weaker during lactation and dry-off, and CD24^pos cells were relatively few. Of note, the (sub)population profile at dry-off appeared close to that during lactation. Using a targeted gene approach, we associated specific genes with epithelial subpopulations, their expression level varying, or not, according to physiological stages. Caseins were only expressed in the CD49_f^medCD24^neg subpopulation. Basal marker genes (keratin(KRT)5, KRT14 and αSMA) were found in the CD49_f^highCD24^neg subpopulations. Luminal gene markers (KRT7, KRT8 and KRT19, CDH1 and the PRLR) were expressed in the CD49_f^lowCD24^neg subpopulation. The CD49_f^lowCD24^pos subpopulation, only abundant at puberty, expressed luminal gene markers and KI67 at high level. In contrast to others, the CD49_f^highCD24^pos cells accounted for a small proportion of total cells, decreasing from puberty to dry-off. They were characterized by expression of luminal and basal gene markers and low KI67 level. Interestingly, this subpopulation showed a remarkable stability of gene expression profile throughout physiological stages and bear the hallmark of quiescence that designate them as the potential bovine mammary stem cells.

TRIENNIAL LACTATION SYMPOSIUM/BOLFA: Plasticity of mammary development in the prepubertal bovine mammary gland

Although peripubertal mammary development represents only a small fraction of the total mass of mammary parenchyma present in the udder at the end of gestation and into lactation, there is increasing evidence that the tissue foundations created in early life can affect future mammary development and function. Studies on expression of estrogen and progesterone receptors seem to confirm the relevance of these steroids in prepubertal mammary development, but connections with other growth factors, hormones, and local tissue factors remain elusive. Enhanced preweaning feeding in the bovine appears to enhance the capacity of mammary tissue to response to mammogenic stimulation. This suggests the possibility that improved early nutrition might allow for creation of stem or progenitor cell populations to better support the massive ductal growth and lobulo-alveolar development during gestation. Increasing evidence that immune cells are involved in mammary development suggests there are unexpected and poorly understood connections between the immune system and mammary development. This is nearly unexplored in ruminants. Development of new tools to identify, isolate, and characterize cell populations within the developing bovine mammary gland offer the possibility of identifying and perhaps altering populations of mammary stem cells or selected progenitor cells to modulate mammary development and, possibly, mammary function.

Comparison of methods to assess onset of breast development in the LEGACY Girls Study: methodological considerations for studies of breast cancer

Background

Younger age at onset of breast development, which has been declining in recent decades, is associated with increased breast cancer risk independent of age at menarche. Given the need to study the drivers of these trends, it is essential to validate methods to assess breast onset that can be used in large-scale studies when direct clinical assessment of breast onset is not feasible.

Methods

Breast development is usually measured by Tanner stages (TSs), assessed either by physical examination or by mother’s report using a picture-based Sexual Maturation Scale (SMS). As an alternative, a mother-reported Pubertal Development Scale (PDS) without pictures has been used in some studies. We compared agreement of SMS and PDS with each other (n = 1022) and the accuracy of PDS with clinical TS as a gold standard for the subset of girls with this measure (n = 282) using the LEGACY cohort. We further compared prediction of breast onset using ROC curves and tested whether adding urinary estrone 1-glucuronide (E1G) improved the AUC.

Results

The agreement of PDS with SMS was high (kappa = 0.80). The sensitivity of PDS vs clinical TS was 86.6%. The AUCs for PDS alone and SMS alone were 0.88 and 0.79, respectively. Including E1G concentrations improved the AUC for both methods (0.91 and 0.86 for PDS and SMS, respectively).

Conclusions

The PDS without pictures is a highly accurate, sensitive, and specific method for assessing breast onset, especially in settings where clinical TS is not feasible. In addition, it is comparable to SMS methods with pictures and thus easier to implement in large-scale studies, particularly phone-based interviews where pictures may not be available. Urinary E1G can improve accuracy over than PDS or SMS alone.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-0943-9) contains supplementary material, which is available to authorized users.

Effects of rumen-undegradable protein on intake, performance, and mammary gland development in prepubertal and pubertal dairy heifers

The objective of this study was to evaluate the influence of different amounts of rumen-undegradable protein (RUP) on intake, N balance, performance, mammary gland development, carcass traits, and hormonal status of Holstein heifers at different physiological stages (PS). Sixteen prepubertal (PRE) heifers (initial BW = 106 ± 7.6 kg; age = 4.3 ± 0.46 mo) and 16 pubertal (PUB) heifers (initial BW = 224 ± 7.9 kg; age = 12.6 ± 0.45 mo) were used in an experiment over a period of 84 d. Four diets with increasing RUP contents (38, 44, 51, and 57% of dietary crude protein) and heifers at 2 PS (PRE or PUB) were used in a 4 × 2 factorial arrangement of treatments in a completely randomized design. Throughout the experiment, 2 digestibility trials were performed over 5 consecutive days (starting at d 36 and 78) involving feed and ort sampling and spot collections of feces and urine. At d 0 and 83, body ultrasound images were obtained for real-time carcass trait evaluation. The mammary gland was ultrasonically scanned at d 0 and every 3 wk during the experiment. Blood samples were taken at d 0 and 84 to determine serum concentrations of progesterone, estrogen, insulin-like growth factor I (IGF-I), and insulin. No interaction between PS and the level of RUP was found for any trait. Apparent digestibility of dry matter, organic matter, and neutral detergent fiber corrected for ash and protein was not affected by RUP level but was lower for PRE compared with PUB heifers. Sorting against neutral detergent fiber corrected for ash and protein (tendency only) and for crude protein was greater for PUB than PRE heifers. Pubertal heifers had greater average daily gain (905 vs. 505 g/d) and N retention (25.9 vs. 12.5 g/d) than PRE heifers. In addition, average daily gain and N retention were greatest at 51% RUP of dietary protein. Mammary ultrasonography indicated no effects of RUP amounts on mammary gland composition, whereas PRE heifers had greater pixel values than PUB, indicating higher contents of fat rather than protein in the mammary glands of PRE heifers. Serum progesterone and IGF-I concentration was affected only by PS, and PRE heifers had greater values of progesterone and IGF-I concentrations than PUB heifers. Serum insulin concentration was unaffected by PS but tended to be higher at 51% of RUP. In conclusion, an RUP level of 51% increases body weight, average daily gain, feed efficiency, and N retention in heifers regardless of the PS. In addition, PRE heifers have a lower sorting ability and reduced intake, total-tract digestibility, and N retention. They also have higher amounts of fat in their mammary glands, even at moderate growth rates.

Cerasomal Lovastatin Nanohybrids for Efficient Inhibition of Triple-Negative Breast Cancer Stem Cells To Improve Therapeutic Efficacy

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a higher risk in younger women and a poorer prognosis and without targeted therapies available currently. Cancer stem cells (CSCs) are increasingly recognized as the main cause of treatment failure and tumor recurrence. The present paper reports the encapsulation of lovastatin (LV) into cerasomes. Compared with free LV, cerasome-encapsulated LV (C-LV) nanohybrids showed cytotoxicity to MDA-MB-231 CSCs in a dose- and time-dependent manner. Furthermore, intravenous injection of C-LV nanohybrids resulted in a significant tumor size reduction in a dose-dependent manner in xenograft tumors derived from subcutaneous inoculation of MDA-MB-231 cells. Furthermore, histopathological and/or immunohistochemical analysis revealed that C-LV nanohybrids significantly induced mammary gland formation and apoptosis and inhibited angiogenesis, the CSC phenotype, and the epithelial-to-mesenchymal transition in xenograft tumors. Most importantly, C-LV nanohybrids were found to be more effective than free LV in inhibiting the growth of breast cancer xenografts and the stemness properties in vivo. To the best of our knowledge, ours is the first demonstration of nanohybrids for efficient inhibition of CSCs derived from TNBC, offering a new option for the TNBC treatment.

TRIENNIAL LACTATION SYMPOSIUM/BOLFA:Historical perspectives of lactation biology in the late 20th and early 21st centuries

The latter half of the 20th century and the early portion of the 21st century will be recognized as the "Golden Age" of lactation biology. This period corresponded with the rise of systemic, metabolomic, molecular, and genomic biology. It includes the discovery of the structure of DNA and ends with the sequencing of the complete genomes of humans and all major domestic animal species including the dairy cow. This included the ability to identify polymorphisms in the nucleic acid sequence, which can be tied to specific differences in cellular, tissue, and animal performance. Before this period, classical work using endocrine ablation and replacement studies identified the mammary gland as an endocrine-dependent organ. In the early 1960s, the development of RIA and radioreceptor assays permitted the study of the relationship between endocrine patterns and mammary function. The ability to measure nucleic acid content of tissues opened the door to study of the factors regulating mammary growth. The development of high-speed centrifugation in the 1960s allowed separation of specific cell organelles and their membranes. The development of transmission and scanning electron microscopy permitted the study of the relationship between structure and function in the mammary secretory cell. The availability of radiolabeled metabolites provided the opportunity to investigate the metabolic pathways and their regulation. The development of concepts regarding the coordination of metabolism to support lactation integrated our understanding of nutrient partitioning and homeostasis. The ability to produce recombinant molecules and organisms permitted enhancement of lactation in farm animal species and the production of milk containing proteins of value to human medicine. These discoveries and others contributed to vastly increased dairy farm productivity in the United States and worldwide. This review will include the discussion of the centers of excellence and scientists who labored in these fields to produce the harvest of knowledge we enjoy today.

Pregnancy and Breast Cancer

Breast cancer is the most commonly diagnosed type of cancer among women worldwide. The majority of breast cancers are sporadic and the etiology is not well understood. Several factors have been attributed to altering the risk of breast cancer. A full-term pregnancy is a crucial factor in altering the risk. Early full-term pregnancy has been shown to reduce the lifetime risk of breast cancer, while a later first full-term pregnancy increases breast cancer risk. Epidemiological and experimental data demonstrate that spontaneous or induced abortions do not significantly alter the risk of breast cancer. In this study, we briefly discuss the different types and stages of breast cancer, various risk factors, and potential mechanisms involved in early full-term pregnancy-induced protection against breast cancer. Understanding how early full-term pregnancy induces protection against breast cancer will help design innovative preventive and therapeutic strategies. This understanding can also help in the development of molecular biomarkers that can be of tremendous help in predicting the risk of breast cancer in the general population.

Role of Growth Hormone in Breast Cancer

Breast cancer is one of the most common cancers diagnosed in women. Approximately two-thirds of all breast cancers diagnosed are classified as hormone dependent, which indicates that hormones are the key factors that drive the growth of these breast cancers. Ovarian and pituitary hormones play a major role in the growth and development of normal mammary glands and breast cancer. In particular, the effect of the ovarian hormone estrogen has received much attention in regard to breast cancer. Pituitary hormones prolactin and growth hormone have also been associated with breast cancer. Although the role of these pituitary hormones in breast cancers has been studied, it has not been investigated extensively. In this review, we attempt to compile basic information from most of the currently available literature to understand and demonstrate the significance of growth hormone in breast cancer. Based on the available literature, it is clear that growth hormone plays a significant role in the development, progression, and metastasis of breast cancer by influencing tumor angiogenesis, stemness, and chemoresistance.

Conjugated Linoleic Acid Administration Induces Amnesia in Male Sprague Dawley Rats and Exacerbates Recovery from Functional Deficits Induced by a Controlled Cortical Impact Injury

Long-chain polyunsaturated fatty acids like conjugated linoleic acids (CLA) are required for normal neural development and cognitive function and have been ascribed various beneficial functions. Recently, oral CLA also has been shown to increase testosterone (T) biosynthesis, which is known to diminish traumatic brain injury (TBI)-induced neuropathology and reduce deficits induced by stroke in adult rats. To test the impact of CLA on cognitive recovery following a TBI, 5-6 month old male Sprague Dawley rats received a focal injury (craniectomy + controlled cortical impact (CCI; n = 17)) or Sham injury (craniectomy alone; n = 12) and were injected with 25 mg/kg body weight of Clarinol® G-80 (80% CLA in safflower oil; n = 16) or saline (n = 13) every 48 h for 4 weeks. Sham surgery decreased baseline plasma progesterone (P4) by 64.2% (from 9.5 ± 3.4 ng/mL to 3.4 ± 0.5 ng/mL; p = 0.068), T by 74.6% (from 5.9 ± 1.2 ng/mL to 1.5 ± 0.3 ng/mL; p < 0.05), 11-deoxycorticosterone (11-DOC) by 37.5% (from 289.3 ± 42.0 ng/mL to 180.7 ± 3.3 ng/mL), and corticosterone by 50.8% (from 195.1 ± 22.4 ng/mL to 95.9 ± 2.2 ng/mL), by post-surgery day 1. CCI injury induced similar declines in P4, T, 11-DOC and corticosterone (58.9%, 74.6%, 39.4% and 24.6%, respectively) by post-surgery day 1. These results suggest that both Sham surgery and CCI injury induce hypogonadism and hypoadrenalism in adult male rats. CLA treatment did not reverse hypogonadism in Sham (P4: 2.5 ± 1.0 ng/mL; T: 0.9 ± 0.2 ng/mL) or CCI-injured (P4: 2.2 ± 0.9 ng/mL; T: 1.0 ± 0.2 ng/mL, p > 0.05) animals by post-injury day 29, but rapidly reversed by post-injury day 1 the hypoadrenalism in Sham (11-DOC: 372.6 ± 36.6 ng/mL; corticosterone: 202.6 ± 15.6 ng/mL) and CCI-injured (11-DOC: 384.2 ± 101.3 ng/mL; corticosterone: 234.6 ± 43.8 ng/mL) animals. In Sham surgery animals, CLA did not alter body weight, but did markedly increase latency to find the hidden Morris Water Maze platform (40.3 ± 13.0 s) compared to saline treated Sham animals (8.8 ± 1.7 s). In CCI injured animals, CLA did not alter CCI-induced body weight loss, CCI-induced cystic infarct size, or deficits in rotarod performance. However, like Sham animals, CLA injections exacerbated the latency of CCI-injured rats to find the hidden MWM platform (66.8 ± 10.6 s) compared to CCI-injured rats treated with saline (30.7 ± 5.5 s, p < 0.05). These results indicate that chronic treatment of CLA at a dose of 25 mg/kg body weight in adult male rats over 1-month 1) does not reverse craniectomy- and craniectomy + CCI-induced hypogonadism, but does reverse craniectomy- and craniectomy + CCI-induced hypoadrenalism, 2) is detrimental to medium- and long-term spatial learning and memory in craniectomized uninjured rats, 3) limits cognitive recovery following a moderate-severe CCI injury, and 4) does not alter body weight.