Mammary Gland Remodeling Research Articles

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.

Development of the Mammary Gland in Mouse: A Whole-Mount Microscopic Analysis.

The mammary gland undergoes functional, developmental, and structural changes that are essential for lactation and reproductive processes. An overview of such unique tissue can offer clearer insights into mammary development and tumorigenesis. Compared to traditional methods, mouse mammary gland whole mount is a pivotal technique that provides three-dimensional structural perspectives on gland morphology and developmental stages, offering an inexpensive and accessible approach. This protocol outlines the tissue isolation of the mouse mammary gland and provides detailed instructions for whole-mount staining and analysis. Mammary gland tissues are carefully dissected from euthanized mice and stained with Carmine Alum to highlight the ductal structures, enabling detailed visualization of the branching patterns and morphological changes. Light microscopy is used to capture a panoramic image of the stained mammary gland, enabling the quantitative analysis of terminal end buds (TEBs) and bifurcated TEBs to further investigate mammary gland remodeling. This method can provide invaluable insights, particularly in the study of mammary gland morphogenesis and tumorigenesis, underscoring its significance in both basic research and clinical applications. Key features • Monitor mammary gland development within 2 days using whole-mount staining.

Mature white adipocyte plasticity during mammary gland remodelling and cancer.

Mammary gland growth and differentiation predominantly rely on stromal-epithelial cellular communication. Specifically, mammary adipocytes play a crucial role in ductal morphogenesis, as well as in the proliferation and differentiation of mammary epithelial cells. The process of lactation entails a reduction in the levels of white adipose tissue associated with the MG, allowing for the expansion of milk-producing epithelial cells. Subsequently, during involution and the regression of the milk-producing unit, adipocyte layers resurface, occupying the vacated space. This dynamic phenomenon underscores the remarkable plasticity and expansion of adipose tissue. Traditionally considered terminally differentiated, adipocytes have recently been found to exhibit plasticity in certain contexts. Unraveling the significance of this cell type within the MG could pave the way for novel approaches to reduce the risk of breast cancer and enhance lactation performance. Moreover, a comprehensive understanding of adipocyte trans- and de-differentiation processes holds promise for the development of innovative therapeutic interventions targeting cancer, fibrosis, obesity, type 2 diabetes, and other related diseases. Additionally, adipocytes may find utility in the realm of regenerative medicine. This review article provides a comprehensive examination of recent advancements in our understanding of MG remodelling, with a specific focus on the tissue-specific functions of adipocytes and their role in the development of cancer. By synthesizing current knowledge in this field, it aims to consolidate our understanding of adipocyte biology within the context of mammary gland biology, thereby fostering further research and discovery in this vital area.

Lactation-associated macrophages exist in murine mammary tissue and human milk

Macrophages are involved in immune defense, organogenesis and tissue homeostasis. Macrophages contribute to the different phases of mammary gland remodeling during development, pregnancy and involution postlactation. Less is known about the dynamics of mammary gland macrophages in the lactation stage. Here, we describe a macrophage population present during lactation in mice. By multiparameter flow cytometry and single-cell RNA sequencing, we identified a lactation-induced CD11c+CX3CR1+Dectin-1+ macrophage population (liMac) that was distinct from the two resident F4/80hi and F4/80lo macrophage subsets present pregestationally. LiMacs were predominantly monocyte-derived and expanded by proliferation in situ concomitant with nursing. LiMacs developed independently of IL-34, but required CSF-1 signaling and were partly microbiota-dependent. Locally, they resided adjacent to the basal cells of the alveoli and extravasated into the milk. We found several macrophage subsets in human milk that resembled liMacs. Collectively, these findings reveal the emergence of unique macrophages in the mammary gland and milk during lactation.

102 Insights Into the Molecular Underpinnings of Disrupted Mammary Development and Function Arising from Late-Gestation Heat Stress

Abstract Exposure to heat stress during a dairy cow’s dry period disrupts mammary gland remodeling impairing milk production during the subsequent lactation. The dry period coincides with late gestation, and Intrauterine hyperthermia affects offspring growth, physiology, and performance into adulthood. This presentation will highlight histological and molecular adaptations of the mammary gland under heat stress, emphasizing the carry-over effects in the dam and her progeny. Pregnant dams were either cooled (CL, fans and water soakers) or heat-stressed (HS, lack of access to cooling devices) in a free-stall setting during the dry period (~46 d) in summer. Heifers gestated under maternal heat stress or cooling (in utero heat stressed, IUHS vs. in utero cooled, IUCL) were euthanized at birth or weaning, or were followed until the first lactation to collect mammary tissue for histological, proteomics, and methylation analyses. In the dam’s mammary gland, 251 proteins and 224 phosphorylated proteins were differentially abundant in HS compared to CL. Top functions were related to immune function, inflammation, amino acid metabolism, reactive oxygen species production, tissue remodeling, and stress response. Intrauterine hyperthermia derailed mammary gland development inducing alterations in the size and weight of the whole udder and parenchyma and fat pad mass. Epithelial structures within the parenchyma of IUHS heifers were significantly underdeveloped, with reduced proliferative capacity. These early-life alterations in tissue microstructure persist through the first lactation, evidenced by IUHS mammary glands with smaller alveoli and fewer mammary epithelial cells that exhibited reduced proliferation capacity. Further, in utero hyperthermia epigenetically programed the udder. Over 130 differentially methylated genes were identified in the IUHS mammary gland with roles in development, innate immune defense, cell signaling, and transcription and translation. These studies provide insights into the molecular underpinnings of disrupted mammary structure and function arising from prior exposure to dry period/late-gestation heat stress, which led to lower milk yields of the dam and her offspring.

G protein-coupled receptor 30 mediates cell proliferation of goat mammary epithelial cells via MEK/ERK&PI3K/AKT signaling pathway

ABSTRACT The mammary gland of mammals possesses the specific function of synthesizing, secreting, and delivering milk. Notably, mammary epithelial cells are considered to be central to control the expansion and remodeling of mammary gland into a milk-secretory organ. And the biological function of mammary gland is mainly regulated by the endocrine system, especially for estrogen. G protein-coupled receptor 30 (GPR30), an estrogen membrane receptor, mediates estrogen-induced functions of physiology and pathophysiology. However, the relationship between estrogen/GPR30 signaling and proliferation of goat mammary epithelial cells (gMECs) is still unclear. Herein, estrogen promoted cell proliferation than control, as evidence by upregulation of cell numbers, BrdU-positive cell counts, and cell viability. Of note, these activities were all obviously reduced by treatment with GPR30 antagonist G15, yet GPR30 agonist G1 increased cell proliferation than control. Further, GPR30 silencing inhibited cell proliferation than negative control. This inhibition was accompanied by a G2/M phase arrest and downregulation of cell cycle regulators. Meanwhile, estrogen increased the phosphorylation of ERK1/2 and AKT. Further, the protein level of p-ERK1/2 and p-AKT was enhanced by GPR30 agonist G1 but inhibited by GPR30 antagonist G15 and GPR30 silencing. Importantly, MEK inhibitor and PI3K inhibitor decreased the expression of cell cycle regulators, and repressed estrogen-induced and G1-driven promotion of cell proliferation, suggesting that estrogen regulated cell proliferation of gMECs through mechanisms involving cell cycle, dependent of GPR30 and MEK/ERK and PI3K/AKT signaling pathway. This may provide a strong theoretical basis for researching estrogen sustained-release drugs promoting breast development and improving lactation performance. Abbreviations: gMECs, goat mammary epithelial cells; E2, 17β-estradiol; GPR30, G protein-coupled receptor 30; shRNA, small hairpin RNA; CDK, cyclin-dependent kinase; PI3K, phosphatidylinositol 3-kinase; AKT, proteinkinase B; MAPK, mitogen-activated protein kinase; MEK, mitogen-activated protein kinase kinase; ERK1/2, extracellular signal-regulated kinase 1/2.

Carry-over effects of dry period heat stress on the mammary gland proteome and phosphoproteome in the subsequent lactation of dairy cows

Exposure to heat stress during a cow’s dry period disrupts mammary gland remodeling, impairing mammary function and milk production during the subsequent lactation. Yet, proteomic changes in the mammary gland underlying these effects are not yet known. We investigated alterations in the mammary proteome and phosphoproteome during lactation as a result of dry period heat stress using an isobaric tag for relative and absolute quantitation (iTRAQ)-based approach. Cows were cooled (CL; n = 12) with fans and water soakers in a free stall setting or were heat stressed through lack of access to cooling devices (HT; n = 12) during the entire dry period (approximately 46 days). All cows were cooled postpartum. Mammary biopsies were harvested from a subset of cows (n = 4 per treatment) at 14, 42, and 84 days in milk. Overall, 251 proteins and 224 phosphorylated proteins were differentially abundant in the lactating mammary gland of HT compared to CL cows. Top functions of differentially abundant proteins and phosphoproteins affected were related to immune function and inflammation, amino acid metabolism, reactive oxygen species production and metabolism, tissue remodeling, and cell stress response. Patterns of protein expression and phosphorylation are indicative of increased oxidative stress, mammary gland restructuring, and immune dysregulation due to prior exposure to dry period heat stress. This study provides insights into the molecular underpinnings of disrupted mammary function and health during lactation arising from prior exposure to dry period heat stress, which might have led to lower milk yields.

Transcriptome profiling of the nonlactating mammary glands of dairy goats reveals the molecular genetic mechanism of mammary cell remodeling

The mammary gland redevelops to the prepregnancy state during involution, which shows the mammary cells have the characteristics of remodeling. The rapidity and degree of mammary gland involution vary across species (e.g., between model organism mice and dairy livestock). However, the molecular genetic mechanism of involution and remodeling of goat mammary gland has not yet been clarified. This work investigated the structural changes and transcriptome characteristics of the mammary gland tissue of nonlactating dairy goats during the late lactation (LL), the dry period (DP), and late gestation (LG). Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining revealed significant changes in the structure of the nonlactating goat mammary gland, and obvious cell apoptosis occurred at LL and DP. Sequencing identified 1,381 genes that are differentially expressed in mammary gland tissue at the 3 developmental stages. Genes related to cell growth, apoptosis, immunity, nutrient transport, synthesis, and metabolism exhibited adaptive transcriptional changes to meet the needs of a new set of mammary gland lactation functions. The significant enrichment of Gene Ontology terms such as humoral immune response, complement activation, and neutrophil-mediated immunity indicates that the innate immune system plays an important role in maintaining the health of degenerative mammary glands and eliminating apoptotic cells. The peroxisome proliferator-activated receptor signaling pathway plays an important regulatory role in lipid metabolism, especially the adaptive changes in expression of genes encoded lipid transport and enzymes, which promote the formation of milk fat during the lactation. The mammary gland development gene module revealed that pregnancy hormone receptors, cell growth factors and their receptors, and genes encoding insulin-like growth factor binding proteins regulate the physiological process of mammary gland involution through adaptive transcriptional changes. Interestingly, ERBB4 was identified as the hub gene of the network that regulates mammary gland growth and development. Overexpression of ERBB4 in mammary epithelial cells cultured in vitro can reduce cell cycle arrest in G1/S phase and apoptosis by regulating the PI3K/Akt signaling pathway and promote the proliferation of mammary epithelial cells. The gene ERBB4 also affects the expression of genes that initiate mammary gland involution and promote mammary gland remodeling. These findings contribute to an in-depth understanding of the molecular mechanisms involved in mammary gland involution and remodeling.

Longitudinal Intravital Microscopy Using a Mammary Imaging Window with Replaceable Lid

The branched structure of the mammary gland is highly dynamic and undergoes several phases of growth and remodeling after birth. Intravital microscopy in combination with skin flap surgery or implantation of imaging windows has been used to study the dynamics of the healthy mammary gland at different developmental stages. Most mammary imaging technologies are limited to a time frame of hours to days, whereas the majority of mammary gland remodeling processes occur in time frames of days to weeks. To study mammary gland remodeling, methods that allow optical access to the tissue of interest for extended time frames are required. Here, an improved version of the titanium mammary imaging window with a replaceable lid (R.MIW) is described that allows high-resolution imaging of the mammary gland with a cellular resolution for up to several weeks. Importantly, the R.MIW provides tissue access over the entire duration of the intravital imaging experiment and could therefore be used for local tissue manipulation, labeling, drug administration, or image-guided microdissection. Taken together, the R.MIW enables high-resolution characterization of the cellular dynamics during mammary gland development, homeostasis, and disease.

Longitudinal Intravital Microscopy Using a Mammary Imaging Window with Replaceable Lid.

The branched structure of the mammary gland is highly dynamic and undergoes several phases of growth and remodeling after birth. Intravital microscopy in combination with skin flap surgery or implantation of imaging windows has been used to study the dynamics of the healthy mammary gland at different developmental stages. Most mammary imaging technologies are limited to a time frame of hours to days, whereas the majority of mammary gland remodeling processes occur in time frames of days to weeks. To study mammary gland remodeling, methods that allow optical access to the tissue of interest for extended time frames are required. Here, an improved version of the titanium mammary imaging window with a replaceable lid (R.MIW) is described that allows high-resolution imaging of the mammary gland with a cellular resolution for up to several weeks. Importantly, the R.MIW provides tissue access over the entire duration of the intravital imaging experiment and could therefore be used for local tissue manipulation, labeling, drug administration, or image-guided microdissection. Taken together, the R.MIW enables high-resolution characterization of the cellular dynamics during mammary gland development, homeostasis, and disease.

Programming effects of late gestation heat stress in dairy cattle.

The final weeks of gestation represent a critical period for dairy cows that can determine the success of the subsequent lactation. Many physiological changes take place and additional exogenous stressors can alter the success of the transition into lactation. Moreover, this phase is pivotal for the final stage of intrauterine development of the fetus, which can have negative long-lasting postnatal effects. Heat stress is widely recognised as a threat to dairy cattle welfare, health, and productivity. Specifically, late gestation heat stress impairs the dam's productivity by undermining mammary gland remodelling during the dry period and altering metabolic and immune responses in early lactation. Heat stress also affects placental development and function, with relevant consequences on fetal development and programming. In utero heat stressed newborns have reduced birth weight, growth, and compromised passive immune transfer. Moreover, the liver and mammary DNA of in utero heat stressed calves show a clear divergence in the pattern of methylation relative to that of in utero cooled calves. These alterations in gene regulation might result in depressed immune function, as well as altered thermoregulation, hepatic metabolism, and mammary development jeopardising their survival in the herd and productivity. Furthermore, late gestation heat stress appears to exert multigenerational effects, influencing milk yield and survival up to the third generation.

Inhibition of cell proliferation and promotion of acinus-like structure formation from goat mammary epithelial cells via Wnt/β-catenin signaling.

Mammary epithelial cells have been suggested to be central to control the expansion and remodeling of mammary gland. Wnt/β-catenin signaling modulates cell fate in animals throughout their life span, and represents indispensable roles in tissue homeostasis, cell renewal, and regeneration in organs. Here, we utilized the small molecule 6-bromoindirubin-3'-oxime (BIO), an activator of Wnt/β-catenin signaling, and investigated whether Wnt/β-catenin signaling regulated the proliferation and acinus-like structure formation of goat mammary epithelial cells (GMECs). We showed that isolated GMECs displayed the typical epithelial cobblestone morphology and expressed specific markers of mammary epithelial cells. BIO inhibited the proliferation of GMECs and decreased the expression of proliferation marker c-myc and cell cycle protein cyclin D1. However, the ability of GMECs to form spheroids was accelerated, and the level of E-cadherin mRNA was upregulated with BIO treatment. E-cadherin showed a bright cytomembrane with DMSO treatment, yet E-cadherin was present in cytomembrane and cytoplasm in GMECs with BIO treatment. Meanwhile, BIO increased the protein level of β-catenin and enhanced the translocation of β-catenin into the nucleus in GMECs. Furthermore, the mRNA level of Axin2 was also upregulated. This study suggested that Wnt/β-catenin signaling may play an important role in the proliferation and the acinus-like formation of GMECs.

Laminin alpha 5 regulates mammary gland remodeling through luminal cell differentiation and Wnt4-mediated epithelial crosstalk.

ABSTRACTEpithelial attachment to the basement membrane (BM) is essential for mammary gland development, yet the exact roles of specific BM components remain unclear. Here, we show that Laminin α5 (Lama5) expression specifically in the luminal epithelial cells is necessary for normal mammary gland growth during puberty, and for alveologenesis during pregnancy. Lama5 loss in the keratin 8-expressing cells results in reduced frequency and differentiation of hormone receptor expressing (HR+) luminal cells. Consequently, Wnt4-mediated crosstalk between HR+ luminal cells and basal epithelial cells is compromised during gland remodeling, and results in defective epithelial growth. The effects of Lama5 deletion on gland growth and branching can be rescued by Wnt4 supplementation in the in vitro model of branching morphogenesis. Our results reveal a surprising role for BM-protein expression in the luminal mammary epithelial cells, and highlight the function of Lama5 in mammary gland remodeling and luminal differentiation.

Optimization of Pulsation Rate of the Milking System for the Mammary Gland Remodeling during Involution in Thai Crossbred Holstein Cows

This study aimed to investigate the effects of pulsation rate of the milking machine on the proteinous components and gelatinase activity in the mammary secretion for optimal tissue remodeling during the dry period in tropical dairy cows. Nine healthy primiparous Thai crossbred Holstein cows (75%HF) were milked with various pulsation rates (50, 60, and 70 cycles/min) one week after calving. The total protein contents of the secretions increased along the time course in 50 and 60 cycles/min groups but not in 70 cycles/min group and were not different among the 3 groups along the time course. Lactoferrin and BSA abundance of the 3 groups as well as γ-globulin in 50 and 70 cycles/min groups also increased in a time-dependent manner, in which only γ-globulin abundance in 60 cycles/min group 14 days before drying off and lactoferrin in 50 cycles/min group 14 days after drying off were significantly higher than those of the other 2 groups. In tissue remodeling by gelatinase activity analysis, 50 cycles/min group showed dramatic increases of Matrix metalloproteinase-9 (MMP-9) and MMP-2 activities after drying off, whereas 60 and 70 cycles/min groups had a significant but a smaller change (p<0.05) along the time course. Cows with 60 cycles/min exhibited dramatic increases of MMP-9 and MMP-2 activities than the other groups before drying off (p<0.05). The findings suggested that milking pulsation rate at 60 cycles/min resulted in higher activity of remodeling during mammary involution and thus may benefit the renewal and health of the udder in the long run.

Endocrine Signals Altered by Heat Stress Impact Dairy Cow Mammary Cellular Processes at Different Stages of the Dry Period.

Simple SummaryLate-gestation heat stress increases blood prolactin and decreases oestrogen concentrations in dry cows. These hormonal alterations may disturb mammary gland remodelling during the dry period, thereby being potentially responsible for the observed production impairments during the subsequent lactation. This project aimed to better understand the molecular mechanisms underlying subsequent impairments in mammary performance after dry period heat stress. For this, we studied the expression of genes encompassing prolactin and oestrogen pathways and key cellular process pathways under different thermal environments and in vitro hormonal milieus. The results of this study revealed that late-gestation heat stress impacted the expression of genes in the mammary gland involved in key cellular processes occurring during the dry period. Furthermore, our results indicated that these modifications are in part modulated by alterations of oestrogen and prolactin signalling.Hormonal alterations occurring under late gestation heat stress may disturb mammary gland remodelling, resulting in a reduced milk yield during the subsequent lactation. We investigated the effects of an altered endocrine environment on mammary gene expression at different stages of the dry period. Mammary gland biopsies from in vivo-cooled (CL) or heat-stressed (HT) cows were collected at d 3 and 35 relative to dry-off and divided into explants. Explants were incubated in vitro for 24 h in one of three media: Basal: no prolactin or estrogen; CL-mimic: Basal + low prolactin + high 17β-estradiol, or HT-mimic: Basal + high prolactin + low 17β-estradiol. Real time qPCR was used to quantify gene expression. We established that late-gestation heat stress changes the expression of prolactin and oestrogen receptors, downregulates genes involved in apoptosis, autophagy and proliferation at d 3 and upregulates genes related to those cellular processes at d 35. Moreover, compared with in vivo treatments, we showed that the expression of fewer genes was impacted by in vitro treatments which aimed to mimic the hormonal response of cows exposed to a different environment. Further research will continue to uncover the mechanisms behind the production impairments caused by late-gestation heat stress.

Gene expression profile of normal breast tissue and body mass index.

In human breast, adipose tissue represents up to 80% of the total volume and plays a critical role in mammary gland remodeling. Given the emerging role of obesity in breast cancer growth and development, we explored the relationship between body mass index (BMI), as a proxy of woman's obesity status, and the expression in normal breast tissue from healthy women of a selected panel of genes, known to be involved in mammary gland homeostasis. Two independent publicly available datasets, composed of 180 specimens of normal breast tissue from reduction mammoplasty were interrogated. Differential gene expression among BMI classes was evaluated by ANOVA, and partial correlation coefficient was used to assay the correlation between genes controlling for BMI. Despite the differences in microarray platforms and analytical procedures, the two datasets shared a core of 9 genes differentially expressed in BMI classes and significantly correlated with BMI. Four (44%) of these genes belong to the functional class of cytokines and cytokine receptors (IL1R1, IL2RA, IL12A, and IL12RB2). The others belong to the functional class of the epigenetic regulation (MEDAG and SETD7), signal transduction (STAT1), cell adhesion (ITGAV), and enzymatic activity (STS). Although exploratory, present findings are in agreement with the role of inflammation modulators in the homeostasis of normal breast tissue and the believe that an increase in body adipose tissue may have a potentially dangerous local effect, through the increased expression of inflammation-related genes and the establishment of a low-grade chronic inflammation.

Distinct Expression Patterns of Fibrillar Collagen Types I, III, and V in Association with Mammary Gland Remodeling during Pregnancy, Lactation and Weaning.

The mammary gland structurally and functionally remodels during pregnancy, during lactation and after weaning. There are three types of fibrillar collagens, types I, III, and V, in mammary stromal tissue. While the importance of the fibrillar structure of collagens for mammary morphogenesis has been suggested, the expression patterns of each type of fibrillar collagen in conjunction with mammary remodeling remain unclear. In this study, we investigated their expression patterns during pregnancy, parturition, lactation and involution. Type I collagen showed a well-developed fibril structure during pregnancy, but the fibrillar structure of type I collagen then became sparse at parturition and during lactation, which was concurrent with the downregulation of its mRNA and protein levels. The well-developed fibrillar structure of type I collagen reappeared after weaning. On the other hand, type V collagen showed a well-developed fibrillar structure and upregulation in the lactation period but not in the periods of pregnancy and involution. Type III collagen transiently developed a dense fibrillar network at the time of parturition and exhibited drastic increases in mRNA expression. These results indicate that each type of fibrillar collagen is distinctly involved in structural and functional remodeling in mammary glands during pregnancy, parturition, lactation, and involution after weaning. Furthermore, in vitro studies of mammary epithelial cells showed regulatory effects of type I collagen on cell adhesion, cell proliferation, ductal branching, and β-casein secretion. Each type of fibrillar collagen may have different roles in defining the cellular microenvironment in conjunction with structural and functional mammary gland remodeling.

Abstract LB-133: Tumor-promoting activity of CCL8 in involution-associated breast cancer

Abstract Postpartum breast cancers that develop within 5 years after child birth have a poor prognosis because of increased risk of metastasis and remain a principal cause of mortality for young women. Therefore understanding the molecular physiology of postpartum breast cancers is imperative as it may provide novel therapeutic options. The increased risk for breast cancer immediately after pregnancy is linked to the extensive remodeling of the mammary gland that is designated as mammary involution. Immune cells such as macrophages and neutrophils, activated by a chemokine and cytokine cascade during involution, are actively involved in mammary gland remodeling and contribute to the disease development. Among the various chemokines activated in involution, the role of CCL8 in the development of postpartum breast cancer has not been addressed despite recent evidence demonstrating its role in metastatic disease. Our results show that CCL8 mRNA and protein levels increase in mammary gland during involution. Tumor growth studies involving CCL8-deficient animals that had been implanted with cancer cells prior to pregnancy or during involution indicated that CCL8 is tumor-promoting specifically following lactation, during involution. CCL8 is responsible for recruiting F4/80-positive macrophages to the mammary gland during the second phase of involution. Thus we asked if CCL8 promotes tumor development by recruiting macrophages in the involuting mammary gland. Our studies showed that CCL8 attracts primarily M2 type macrophages and that depletion of macrophages by liposomal clodronate abolished the tumor-promoting effect of CCL8 in the wt animals but did not affect CCL8KO animals, at which the M2 macrophages were already absent. These results illustrate the role of CCL8 in the development of postpartum breast cancer by recruiting M2 macrophages and suggest the potential value of targeting CCL8 for disease management. Citation Format: Eleni Farmaki, Vimala Kaza, Ioulia Chatzistamou, Hippokratis Kiaris. Tumor-promoting activity of CCL8 in involution-associated breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-133.

Mammary Stem Cells in Domestic Animals: The Role of ROS.

Reactive oxygen species (ROS) are produced as a natural byproduct of the normal metabolism of oxygen and play significant roles in cell signaling and homeostasis. Although ROS have been involved in pathological processes as diverse as cancer, cardiovascular disease, and aging, they may to exert an effect even in a physiological context. In the central nervous system, stem cells and hematopoietic stem cells are early progenitors that contain lower levels of ROS than their more mature progeny. These different concentrations have been reported to be crucial for maintaining stem cell function. Mammary gland remodeling has been proposed to be organized through the activation and regulation of cells with stemness, either considered real stem cells or primitive precursors. Given the state of oxidative stress in the mammary gland tissue induced by high milk production, in particular in highly productive dairy cows; several studies have focused on the relationship between adult mammary stem cells and the oxidative state of the gland. The oxidative state of the mammary gland appears to be involved in the initial development and metastasis of breast cancer through interference with mammary cancerous stem cells. This review summarizes some links between the mammary stem and oxidative state of the gland.

Rearing performance of piglets from the aspect of mammary gland remodeling in sows of two genotypes

Rearing performance of piglets from the aspect of mammary gland remodeling in sows of two genotypes