Role of ovarian secretions in mammary gland development and function in ruminants

Current status and challenges for cell-cultured milk technology: a systematic review

Cellular agriculture is an innovative technology for manufacturing sustainable agricultural products as an alternative to traditional agriculture. While most cellular agriculture is predominantly centered on the production of cultured meat, there is a growing demand for an understanding of the production techniques involved in dairy products within cellular agriculture. This review focuses on the current status of cellular agriculture in the dairy sector and technical challenges for cell-cultured milk production. Cellular agriculture technology in the dairy sector has been classified into fermentation-based and animal cell culture-based cellular agriculture. Currently, various companies synthesize milk components through precision fermentation technology. Nevertheless, several startup companies are pursuing animal cell-based technology, driven by public concerns regarding genetically modified organisms in precision fermentation technology. Hence, this review offers an up-to-date exploration of animal cell-based cellular agriculture to produce milk components, specifically emphasizing the structural, functional, and productive aspects of mammary epithelial cells, providing new information for industry and academia.

Effect of LHCGR and FSHR gene polymorphisms on fertility traits and milk yield of cross-bred dairy cows in Sri Lanka

Single nucleotide polymorphism (SNP) analysis of fertility genes will be useful in improving the genetic potential of dairy cows. A population of 142 cross-bred dairy cows was screened for SNPs in bovine luteinizing hormone choriogonadotropin receptor (LHCGR) and bovine follicle stimulating hormone receptor (FSHR) genes. The effect of reported SNPs on selected fertility traits (average calving interval, average number of services per conception and age at first calving) and milk yield was determined. Altogether six SNPs were detected in animals screened under the present study. Among them, four SNPs (rs41256848, rs41256850, rs465790244, and rs45463781) were located in the exon 11 region of the LHCGR gene and two SNPs (rs43676359 and G-278-A (GU253337) were located in the five upstream region of the FSHR gene. Minor alleles identified for SNPs in the FSHR gene in the studied small population of cows differed from those reported in other research. In this study, only rs45463781 SNP at exon 11 of the LHCGR gene significantly affected the average milk yield in cross-bred cows. The nucleotide change from "G" to "A" negatively affected the average milk yield. Further investigations are needed to confirm the reported association with a larger sample size.

Mitophagy involved the biological processes of hormones

Mitochondria fulfill vital functions in energy production, maintaining ion balance, and facilitating material metabolism. Mitochondria are sacrificed to protect cells or induce apoptosis when the body is under stress. The regulatory pathways of mitophagy include both ubiquitin-dependent and non-dependent pathways. The involvement of mitophagy has been demonstrated in the onset and progression of numerous diseases, highlighting its significant role. Endocrine hormones are chemical substances secreted by endocrine organs or endocrine cells, which participate in the regulation of physiological functions and internal environmental homeostasis of the body. Imbalances in endocrine hormones contribute to the development of various diseases. However, the precise impact of mitophagy on the physiological and pathological processes involving endocrine hormones remains unclear. This article aims to comprehensively overview recent advancements in understanding the mechanisms through which mitophagy regulates endocrine hormones.

Postnatal exposure to a glyphosate-based herbicide interferes with the development and growth of the mammary gland of pre-pubertal Ewe lambs

The aim of the present study was to evaluate whether early postnatal exposure to a glyphosate-based herbicide (GBH) alters pre-pubertal mammary development in Friesian lambs. To this end, from postnatal day 1-14, ewe lambs were exposed subcutaneously or orally to GBH (2 mg/kg bw/day) or vehicle (control) and mammary gland biopsies were obtained at 45 days of age. GBH-exposed lambs exhibited larger mammary ducts and less area occupied by terminal duct lobular units than controls, accompanied by an increase in the area of adipocytes in the mammary stroma. Lambs subcutaneously exposed to GBH showed increased protein expression of estrogen receptor alpha; however, both GBH-exposed groups had decreased mRNA expression of this receptor. Control lambs showed nuclear progesterone receptor (PR) protein expression, whereas GBH-exposed animals showed cytoplasmic PR expression; both GBH-exposed groups exhibited decreased mRNA expression of PR. GBH-exposed lambs also had decreased epithelial cell proliferation. Regarding insulin-like growth factors, both groups showed similar IGF-1 mRNA and protein expression but decreased expression of its receptor, and increased IGFBP5 expression. In addition, phosphorylated AKT was only observed in the mammary gland of control lambs. Our results show that early postnatal exposure to GBH, regardless of the exposure route, affects the IGF-1 system and the AKT/protein kinase B pathway, interfering with steroid hormone receptor expression and cell proliferation. This consequently modifies the growth and development of the pre-pubertal mammary gland of Frisian lambs.

Deciphering the Roles & Regulation of Estradiol Signaling during Female Mini-Puberty: Insights from Mouse Models

Mini-puberty of infancy is a short developmental phase occurring in humans and other mammals after birth. In females, it corresponds to transient and robust activation of the hypothalamo-pituitary-ovarian (HPO) axis revealed by high levels of gonadotropin hormones, follicular growth, and increased estradiol production by the ovary. The roles of estradiol signaling during this intriguing developmental phase are not yet well known, but accumulating data support the idea that it aids in the implementation of reproductive function. This review aims to provide in-depth information on HPO activity during this particular developmental phase in several mammal species, including humans, and to propose emerging hypotheses on the putative effect of estradiol signaling on the development and function of organs involved in female reproduction.

Critical Review on Physiological and Molecular Features during Bovine Mammary Gland Development: Recent Advances

The mammary gland is a unique organ with the ability to undergo repeated cyclic changes throughout the life of mammals. Among domesticated livestock species, ruminants (cattle and buffalo) constitute a distinct class of livestock species that are known milk producers. Cattle and buffalo contribute to 51 and 13% of the total milk supply in the world, respectively. They also play an essential role in the development of the economy for farming communities by providing milk, meat, and draft power. The development of the ruminant mammary gland is highly dynamic and multiphase in nature. There are six developmental stages: embryonic, prepubertal, pubertal, pregnancy, lactation, and involution. There has been substantial advancement in our understanding of the development of the mammary gland in both mouse and human models. Until now, there has not been a thorough investigation into the molecular processes that underlie the various stages of cow udder development. The current review sheds light on the morphological and molecular changes that occur during various developmental phases in diverse species, with a particular focus on the cow udder. It aims to explain the physiological differences between cattle and non-ruminant mammalian species such as humans, mice, and monkeys. Understanding the developmental biology of the mammary gland in molecular detail, as well as species-specific variations, will facilitate the researchers working in this area in further studies on cellular proliferation, differentiation, apoptosis, organogenesis, and carcinogenesis. Additionally, in-depth knowledge of the mammary gland will promote its use as a model organ for research work and promote enhanced milk yield in livestock animals without affecting their health and welfare.

The role of mitochondria and mitochondrial hormone receptors on the bioenergetic adaptations to lactation

The most recognized role of mitochondria is producing more than 90% of the total cellular energy in the form of ATP. In addition, mitochondrial function encompasses the maintenance of antioxidant balance, the regulation of intracellular calcium concentrations, the progression of cell death, and the biosynthesis of purines, hemes, lipids, amino acids and steroid hormones. Mitochondria are also important hormone targets. Estrogens, progestagens, and prolactin, are among the hormones that can impact mitochondrial function and modulate the underlying adaptations to changing bioenergetic and metabolic needs. Lactation represents a metabolic challenge with significant increases in energy requirements and fluctuating levels of hormones. To meet these bioenergetic demands, liver mitochondria increase their state 3 and 4 respiration, adjust superoxide dismutase activity, and elevate succinate dehydrogenase-related respiration. Skeletal muscle mitochondria respond by increasing their respiratory control ratio and adjusting catalase activity. In this review, these adaptations are described considering the lactation hormonal milieu.

Nutritional strategies for heifers under grazing system: productive and nutritional performance, metabolic profile and ovarian activity

The objective of this study was to evaluate the effects of nutritional strategies on productive and nutritional performance, metabolic profile, and ovarian activity in heifers under grazing in the tropics in Brazil. Forty Nellore heifers averaging 8.5 ± 0.06 months and 248.6 ± 3.3 kg body weight (BW) were distributed in a completely randomized 2 × 2 factorial design with four treatments and ten replicates. The evaluated strategies consisted of different amounts of energetic-protein supplement: (1) 4 g/kg of BW of supplement in the pre-weaning and post-weaning; (2) 4 g/kg of BW of supplement pre-weaning and 6 g/kg in the post-weaning; (3) 6 g/kg of BW of supplement in the pre-weaning and 4 g/kg of BW in the post-weaning and; (4) 6 g/kg of BW of supplement in the pre-weaning and post-weaning. Crude protein (CP) and organic matter (OM) intake were increased (P < 0.05) by increasing the amounts of supplement in the post-weaning. Additionally, increasing supplement amounts in the post-weaning increased the digestibility of OM and CP (P < 0.05). Means insulin and glucose concentrations were greater (P < 0.05) for heifers that received higher amounts of supplement in the post-weaning. Average daily gain and fat thickness in the rump were increased (P < 0.05) by increasing supplement amounts in the post-weaning. Amounts of supplement did not influence the body growth of heifers. However, follicular number, diameter, and progesterone concentration were greater (P < 0.05) for heifers that received higher amounts of supplement in the post-weaning. In summary, increasing supplement amounts in the post-weaning improve the performance, energy and metabolic status, and ovarian activity in beef heifers under grazing in the tropics. Due to higher intake of supplement, the heifers receiving 6 g/kg of BW post-weaning had greater responses, independently of the supplement amount received pre-weaning.

Comparative biochemical profiles, production and reproduction status of the post-partum dairy cows with and without purulent vaginal discharge

Purulent vaginal discharge (PVD) is a prevalent uterine disease of dairy cows during the puerperium that affects the milk production and affects the profitability of farms. The objectives of this study were to evaluate the biochemical profile, the body condition score, the milk production of cows with PVD and the effects PVD on reproductive performance. A total of 338 Holstein dairy cows aged from 3 to 5 years, from three commercial dairy farms, from Brazil, were used. Blood samples were collected within 25 ± 3 days post-partum from Holstein dairy cows without PVD (control cows, n = 242) and cows with PVD (n = 96), based on scoring of the vaginal discharge. The body condition score and milk production were recorded on the day of sampling. The biochemical profile encompassed albumin, urea, gamma-glutamyl transferase, calcium, fibrinogen and cholesterol concentrations. The number of services per pregnancy was lower (p < 0.01), and the number of days until first insemination and the median time to pregnancy were higher in cows with PVD (p < 0.01) when compared with control cows. Milk production and body condition score were lower (p < 0.01) in cows with PVD than in control group. Cows with PVD had lower (p < 0.05) serum albumin, urea, calcium and cholesterol concentrations, and higher serum gamma-glutamyl transferase activity and fibrinogen concentration than cows without PVD. Our results show that cows with PVD have changes in the biochemical profile and negative effects on production and reproduction performance.

Molecular signature of the putative stem/progenitor cells committed to the development of the bovine mammary gland at puberty

Milk production is highly dependent on the extensive development of the mammary epithelium, which occurs during puberty. It is therefore essential to distinguish the epithelial cells committed to development from the related epithelial hierarchy. Using cell phenotyping and sorting, we highlighted four cell sub-populations within the bovine mammary gland at puberty. The CD49_f^highCD24^neg cells expressing CD10, KRT14, vimentin and PROCR corresponded to cells committed to the basal lineage. The CD49_f^low sub-population contained two cell subsets (CD49_f^lowCD24^neg and CD49_f^lowCD24^pos). Both subsets expressed hormone receptors including ER, PR and PRLR, as well as ALDH1 activity but only the CD49_f^lowCD24^pos subset expressed ELF5. These data indicated that the CD49_f^low sub-population is mainly composed of cells displaying a luminal phenotype and that this population comprises two luminal cell subsets, namely the CD24^neg and CD24^pos cells, likely committed to ductal and alveolar lineage, respectively. The putative mammary stem cell (MaSC) fraction was recovered in the CD49_f^highCD24^pos sub-population which were shown to form mammospheres in vitro. These cells differentially expressed CD10, KRT14 and KRT7, suggesting the existence of several putative MaSC sub-fractions. In-depth characterization of these epithelial sub-populations provides new insights into the bovine mammary epithelial cell lineage and suggests a common developmental lineage in mammals.

Effects of feeding treatment on growth rates, metabolic profiles and age at puberty, and their relationships in dairy heifers

Puberty attainment in dairy heifers has been widely studied from a hormonal point of view, but few studies have focussed on puberty-blood profile relationships during growth. We led experiments to determine the effects of feeding treatments on growth parameters, age at puberty and plasma biochemical profiles, and the relationships between age at puberty and metabolic profiles at 6, 9, 12 and 15 months (mo) of age. Blood samples were collected from 67 Holstein heifers, born between September 2011 and February 2012, every 10 days from 5.5 mo of age until heifers were considered pubertal (plasma progesterone concentration greater than 1.0 ng/ml) or oestrus synchronisation (November 2012; 11 to 15 mo of age). Heifers born before 30 November were fed either a standard diet (SD, n=27) or an intensive-plane diet (ID1, n=27) from 0 to 6 mo of age. This strategy aimed to reach 190 to 200 kg (SD) or 220 to 230 kg (ID1) BW at 6 mo of age. All heifers born after 1 December received an intensive-plane diet (ID2, n=13) from birth until oestrus synchronisation, in order to reach a similar BW at first insemination as heifers born before 1 December. Only 56 heifers reached puberty before oestrus synchronisation, at an average age of 10.3±2.2 mo (6.2 to 14.4 mo) and a BW of 296±40 kg (224 to 369 kg). There was no difference among the three feeding treatments until 6 mo, but at 9, 12 and 15 mo of age, ID2 (n=11) heifers weighed 37, 52 and 30 kg more than SD (n=22) and ID1 (n=23) heifers (P&lt;0.001), respectively. Glucose, non-esterified fatty acids, albumin, aspartate aminotransferase, alkaline phosphatase and tartrate-resistant acid phosphatase, calcium, phosphorus, potassium and iron decreased with age, whereas β-hydroxybutyric acid, total cholesterol, creatinine, the creatinine : albumin ratio, alanine aminotransferase and chloride increased. The feeding treatment significantly affected creatinine, the creatinine : albumin ratio, and phosphorus and sodium levels, which were higher for ID2 heifers compared with SD and ID1. A logistic regression based on plasma metabolites at 6 mo of age to explain puberty attainment before or at 12 mo of age showed a positive relationship with plasma cholesterol (odds ratio=9.05). In conclusion, the feeding treatment had minor consequences on plasma metabolites, but it did affect growth performance.

Histochemical properties of bovine and ovine mammary glands during fetal development

In order to obtain more information on the development of bovine and ovine fetal mammary glands, a series of mammary glands from fetuses of different ages were analyzed. A total of 16 bovine fetuses with curved crown rump lengths ranging from 12 cm (80 days) to 75 cm (240 days) and 15 ovine fetuses ranging from 55 days to 131 days were examined. We used hematoxylin and eosin stain and Oil-Red-O stain to analyze the developmental and morphogenetic processes of mammary glands. In addition, we used immunohistochemical staining to determine the pattern of expression of cytokeratin 18 (CK18) during luminal epithelial differentiation, α-smooth-muscle actin (α-SMA) for myoepithelial differentiation, Ki-67 for cell proliferation, and estrogen receptor α (ERα). Our analyzes showed: (a) The primary mammary duct begin to proliferate in a lengthwise within the teat at 90 days in bovine fetuses and 63 days in ovine fetus; (b) luminal epithelial cells and myoepithelial cells appeared from 90 days in bovine fetuses and 63 days in ovine fetus; (c) proliferation of epithelial cells appeared to coincide with the development of the primary and secondary ducts; and (d) ERα was not found in the fetal mammary gland, but adipocytes showed the presence of ERα. Overall, these results indicate that the sequence of events in the prenatal development of the mammary gland of sheep is similar to that of cattle.

The Terminal End Bud: the Little Engine that Could

The mammary gland is one of the most regenerative organs in the body, with the majority of development occurring postnatally and in the adult mammal. Formation of the ductal tree is orchestrated by a specialized structure called the terminal end bud (TEB). The TEB is responsible for the production of mature cell types leading to the elongation of the subtending duct. The TEB is also the regulatory control point for basement membrane deposition, branching, angiogenesis, and pattern formation. While the hormonal control of TEB growth is well characterized, the local regulatory factors are less well understood. Recent studies of pubertal outgrowth and ductal elongation have yielded surprising details in regards to ongoing processes in the TEB. Here we summarize the current understanding of TEB biology, discuss areas of future study, and discuss the use of the TEB as a model for the study of breast cancer.

Serotoninergic and Circadian Systems: Driving Mammary Gland Development and Function

Since lactation is one of the most metabolically demanding states in adult female mammals, beautifully complex regulatory mechanisms are in place to time lactation to begin after birth and cease when the neonate is weaned. Lactation is regulated by numerous different homeorhetic factors, all of them tightly coordinated with the demands of milk production. Emerging evidence support that among these factors are the serotonergic and circadian clock systems. Here we review the serotoninergic and circadian clock systems and their roles in the regulation of mammary gland development and lactation physiology. We conclude by presenting our hypothesis that these two systems interact to accommodate the metabolic demands of lactation and thus adaptive changes in these systems occur to maintain mammary and systemic homeostasis through the reproductive cycles of female mammals.

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

The mammary gland (MG) is one of a few organs that undergoes most of its growth after birth. Much of this development occurs concurrently with specific reproductive states, such that the ultimate goal of milk synthesis and secretion is coordinated with the nutritional requirements of the neonate. Central to the reproductive-MG axis is its endocrine regulation, and pivotal to this regulation is the ovarian secretion of estrogen (E). Indeed, it is widely accepted that estrogens are essential for growth of the MG to occur, both for ductal elongation during puberty and for alveolar development during gestation. As the factors regulating MG development continually come to light from the fields of developmental biology, lactation physiology, and breast cancer research, a growing body of evidence serves as a reminder that the MG are not as exclusively dependent on estrogens as might have been thought. The objective of this review is to summarize the state of information regarding our understanding of how estrogen (E) has been implicated as the key regulator of MG development, and to highlight some of the alternative E-independent mechanisms that have been discovered. In particular, we review our findings that dietary trans-10,cis-12 conjugated linoleic acid promotes ductal elongation and that the combination of progesterone (P) and prolactin (PRL) can stimulate branching morphogenesis in the absence of E. Ultimately, these examples stand as a healthy challenge to the question of just how important estrogens are for MG development. Answers to this question, in turn, increase our understanding of MG development across all mammals and the ways in which it can affect milk production.

Weaknesses and Pitfalls of Using Mice and Rats in Cancer Chemoprevention Studies

Many studies, using different chemical agents, have shown excellent cancer prevention efficacy in mice and rats. However, equivalent tests of cancer prevention in humans require decades of intake of the agents while the rodents' short lifespans cannot give us information of the long-term safety. Therefore, animals with a much longer lifespan should be used to bridge the lifespan gap between the rodents and humans. There are many transgenic mouse models of carcinogenesis available, in which DNA promoters are used to activate transgenes. One promoter may activate the transgene in multiple cell types while different promoters are activated at different ages of the mice. These spatial and temporal aspects of transgenes are often neglected and may be pitfalls or weaknesses in chemoprevention studies. The variation in the copy number of the transgene may widen data variation and requires use of more animals. Models of chemically-induced carcinogenesis do not have these transgene-related defects, but chemical carcinogens usually damage metabolic organs or tissues, thus affecting the metabolism of the chemopreventive agents. Moreover, many genetically edited and some chemically-induced carcinogenesis models produce tumors that exhibit cancerous histology but are not cancers because the tumor cells are still mortal, inducer-dependent, and unable to metastasize, and thus should be used with caution in chemoprevention studies. Lastly, since mice prefer an ambient temperature of 30-32°C, it should be debated whether future mouse studies should be performed at this temperature, but not at 21-23°C that cold-stresses the animals.