At the dawn of a new discovery: the potential of breast milk stem cells

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Postnatal reproductive development and the lactocrine hypothesis

Maternal effects on development can program cell fate and dictate offspring phenotype. Such effects do not end at birth, but extend into postnatal life through signals communicated from mother to offspring in first milk (colostrum). Transmission of bioactive factors from mother to offspring as a specific consequence of nursing defines a lactocrine mechanism. The female reproductive tract is not fully formed at birth (postnatal day = PND 0). Data for ungulates and mice indicate that disruption of development during neonatal life can have lasting effects on the form and function of uterine tissues. Uterine growth and histogenesis proceed in an ovary-independent manner shortly after birth, suggesting that extra-ovarian inputs are important in this process. Data for the pig indicate that lactocrine signals communicated within 12 to 48 h from birth constitute one source of such uterotrophic support. Disruption of lactocrine signaling, either naturally, by limited colostrum consumption, or experimentally, by milk replacer feeding, alters neonatal porcine uterine development and can have negative consequences for reproductive performance in adults. Substantial differences in endometrial and uterine gene expression between colostrum- and replacer-fed gilts were evident by PND 2, when RNA sequencing revealed over 800 differentially expressed, lactocrine-sensitive genes. Lactocrine-sensitive biological processes identified through transcriptomic studies and integrated microRNA-mRNA pathway analyses included those associated with both cell-cell and ESR1 signaling, and tissue development. Evidence for the pig indicates that colostrum consumption and lactocrine signaling are required to establish a normal uterine developmental program and optimal uterine developmental trajectory.

Reducing Incidence of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a multifactorial disease that occurs when multiple risk factors and/or stressors overlap, leading to profound inflammation and intestinal injury. Due to its multifactorial nature, there has been much uncertainty in identifying clear strategies for prevention of NEC. Despite these obstacles, the incidence of NEC has gradually been decreasing over the past 10 years, in part due to quality improvement (QI) initiatives to prevent NEC. Current QI strategies primarily target the various predisposing conditions. This article reviews the evidence on which QI interventions to prevent NEC have been based and provides examples of successful QI interventions.

Evaluation of the Safety of Drugs and Biological Products Used During Lactation: Workshop Summary

This report serves as a summary of a 2-day public workshop sponsored by the US Food and Drug Administration (FDA) to discuss the safety of drugs and biological products used during lactation. The aim of the workshop was to provide a forum to discuss the collection of data to inform the potential risks to breastfed infants with maternal use of medications during lactation. Discussions included the review of current approaches to collect data on medications used during lactation, and the considerations for future approaches to design and guide clinical lactation studies. This workshop is part of continuing efforts to raise the awareness of the public for women who choose to breastfeed their infants.

[Effect of breastfeeding versus formula milk feeding on preterm infants in the neonatal intensive care unit]

OBJECTIVE

To investigate the importance of breastfeeding in preterm infants with various gestational ages.

METHODS

A total of 639 preterm infants with a gestational age of 28⁺³-36⁺⁶ weeks were enrolled, and according to the feeding pattern, they were divided into exclusive breastfeeding group (n=237) and formula milk feeding group (fed with liquid milk for preterm infants; n=402). These two feeding patterns were compared in terms of their effects on weight gain, laboratory markers including albumin (Alb) and alkaline phosphatase (ALP), incidence rate of feeding intolerance, and incidence rates of complications including necrotizing enterocolitis (NEC) and retinopathy of prematurity (ROP).

RESULTS

Compared with the formula milk feeding group, the breastfeeding group had a significantly faster increase in body weight, a significantly lower incidence rate of NEC, a significantly higher ALP level, and a significantly lower Alb level in the preterm infants with a gestational age of 28-30 weeks (P<0.05); there were no significant differences between the two groups in the incidence rates of anemia, ROP, bronchopulmonary dysplasia (BPD), and nosocomial infection and length of hospital stay (P>0.05). For the preterm infants with a gestational age of 31-33 weeks, the breastfeeding group had a significantly faster increase in body weight, a significantly lower incidence rate of feeding intolerance, a significantly shorter length of hospital stay, and a significantly higher ALP level (P<0.05); there were no significant differences between the two groups in the incidence rates of NEC, anemia, ROP, BPD, and nosocomial infection and the Alb level (P>0.05). For the preterm infants with a gestational age of 34-36 weeks, there were no significant differences in these indices between the two groups (P>0.05).

CONCLUSIONS

Breastfeeding plays an important role in increasing body weight, reducing the incidence rates of feeding intolerance and NEC, and shortening the length of hospital stay in preterm infants with a gestational age of 28-33 weeks.

Influence of own mother's milk on bronchopulmonary dysplasia and costs

BACKGROUND

Human milk from the infant's mother (own mother's milk; OMM) feedings reduces the risk of several morbidities in very low birthweight (VLBW) infants, but limited data exist regarding its impact on bronchopulmonary dysplasia (BPD).

OBJECTIVE

To prospectively study the impact of OMM received in the neonatal intensive care unit (NICU) on the risk of BPD and associated costs.

DESIGN/METHODS

A 5-year prospective cohort study of the impact of OMM dose on growth, morbidity and NICU costs in VLBW infants. OMM dose was the proportion of enteral intake that consisted of OMM from birth to 36 weeks postmenstrual age (PMA) or discharge, whichever occurred first. BPD was defined as the receipt of oxygen and/or positive pressure ventilation at 36 weeks PMA. NICU costs included hospital and physician costs.

RESULTS

The cohort consisted of 254 VLBW infants with mean birth weight 1027±257 g and gestational age 27.8±2.5 weeks. Multivariable logistic regression demonstrated a 9.5% reduction in the odds of BPD for every 10% increase in OMM dose (OR 0.905 (0.824 to 0.995)). After controlling for demographic and clinical factors, BPD was associated with an increase of US$41 929 in NICU costs.

CONCLUSIONS

Increased dose of OMM feedings from birth to 36 weeks PMA was associated with a reduction in the odds of BPD in VLBW infants. Thus, high-dose OMM feeding may be an inexpensive, effective strategy to help reduce the risk of this costly multifactorial morbidity.

Postnatal Cytomegalovirus Infection Through Human Milk in Preterm Infants: Transmission, Clinical Presentation, and Prevention

Cytomegalovirus (CMV) is reactivated in the lactating breast in up to 96% of CMV seropositive mothers. There is a relevant entity of postnatally acquired symptomatic CMV infection and disease of preterm infants through raw breast milk (BM). Actual data support negative influence on long-term cognitive development. Concerning prevention, only heat inactivation eliminates virus infectivity, and short-term heat inactivation is most preservative; this can be applied effectively under routine conditions. Short-term heat inactivation for 5 minutes at 62°C maintains the benefits of feeding BM without the disadvantages of CMV transmission.

Breast Milk Stem Cells: Current Science and Implications for Preterm Infants

BACKGROUND

The benefits of breast milk are well described, yet the mechanistic details related to how breast milk protects against acute and chronic diseases and optimizes neurodevelopment remain largely unknown. Recently, breast milk was found to contain stem cells that are thought to be involved in infant development.

PURPOSE

The purpose of this review was to synthesize all available research involving the characterization of breast milk stem cells to provide a basis of understanding for what is known and what still needs further exploration.

METHODS/SEARCH STRATEGY

The literature search was conducted between August and October 2015 using the CINAHL, PubMed, and reference list searching. Nine studies addressed characterization of human breast milk stem cells.

FINDINGS/RESULTS

Five research teams in 4 countries have published studies on breast milk stem cells. Current research has focused on characterizing stem cells in full-term breast milk. The amount, phenotype, and expression of breast milk stem cells are known to vary between mothers, and they have been able to differentiate into all 3 germ layers (expressing pluripotent characteristics).

IMPLICATIONS FOR PRACTICE

There is much to learn about breast milk stem cells. Given the potential impact of this research, healthcare professionals should be aware of their presence and ongoing research to determine benefits for infants.

IMPLICATIONS FOR RESEARCH

Extensive research is needed to further characterize stem cells in breast milk (full-term and preterm), throughout the stages of lactation, and most importantly, their role in the health of infants, and potential for use in regenerative therapies.

Leptin Levels Are Higher in Whole Compared to Skim Human Milk, Supporting a Cellular Contribution

Human milk (HM) contains a plethora of metabolic hormones, including leptin, which is thought to participate in the regulation of the appetite of the developing infant. Leptin in HM is derived from a combination of de novo mammary synthesis and transfer from the maternal serum. Moreover, leptin is partially lipophilic and is also present in HM cells. However, leptin has predominately been measured in skim HM, which contains neither fat nor cells. We optimised an enzyme-linked immunosorbent assay for leptin measurement in both whole and skim HM and compared leptin levels between both HM preparations collected from 61 lactating mothers. Whole HM leptin ranged from 0.2 to 1.47 ng/mL, whilst skim HM leptin ranged from 0.19 to 0.9 ng/mL. Whole HM contained, on average, 0.24 ± 0.01 ng/mL more leptin than skim HM (p < 0.0001, n = 287). No association was found between whole HM leptin and fat content (p = 0.17, n = 287), supporting a cellular contribution to HM leptin. No difference was found between pre- and post-feed samples (whole HM: p = 0.29, skim HM: p = 0.89). These findings highlight the importance of optimising HM leptin measurement and assaying it in whole HM to accurately examine the amount of leptin received by the infant during breastfeeding.

Effect of Breast Milk Calcium and Fluidity on Breast Cancer Cells: An In Vitro Cell Culture Study

AIM

The aims of this study were to investigate the effects of calcium at the same concentration as that found in human milk on the viability, proliferation, and adhesion of MCF-7 human breast ductal carcinoma cells by exposing them to calcium at the same frequency as in breastfeeding.

MATERIALS AND METHODS

High-concentration calcium was applied for 30 minutes every 4 hours for 24, 48, and 72 hours. Cell proliferation and viability were measured using a hemocytometer and the MTT cell viability assay. The effects of calcium treatment were evaluated by a comparison among a multiple-, single-dose calcium treatment, and a control group.

RESULTS

We show that calcium at the same concentration as that in milk caused a decrease in the number of cells but did not affect cell viability.

CONCLUSIONS

The results of this study suggest that calcium caused a lowering of the number of cells from the luminal surface of the breast by triggering proliferation under the condition of fluidity. Calcium and fluidity together serve to eliminate breast cancer stem cells during the lactation period. Effects of the other components of milk can be analyzed by the new method developed in this study.

[Research advances in breastfeeding]

Human breast milk is the most natural and ideal food for the baby. Breastfeeding provides benefits for maternal and child health, child immune function, growth and development, and society. The operation of human milk bank and the use of donor human milk undoubtedly provides a new way of nutrition support for the preterm infants without their own mother's milk and a new kind of treatment for other diseases. Present research on the composition of breast milk focuses on the variety and quantity of proteins, bioactive substances, probiotics and cell population.Future research may focus on the bioactive substances, the mechanism of regulation and effect of cell population, the application of probiotics and the clinical application of donor human milk.

[Research advances in breastfeeding]

Human breast milk is the most natural and ideal food for the baby. Breastfeeding provides benefits for maternal and child health, child immune function, growth and development, and society. The operation of human milk bank and the use of donor human milk undoubtedly provides a new way of nutrition support for the preterm infants without their own mother's milk and a new kind of treatment for other diseases. Present research on the composition of breast milk focuses on the variety and quantity of proteins, bioactive substances, probiotics and cell population.Future research may focus on the bioactive substances, the mechanism of regulation and effect of cell population, the application of probiotics and the clinical application of donor human milk.

Biological underpinnings of breastfeeding challenges: the role of genetics, diet, and environment on lactation physiology

Lactation is a dynamic process that has evolved to produce a complex biological fluid that provides nutritive and nonnutritive factors to the nursing offspring. It has long been assumed that once lactation is successfully initiated, the primary factor regulating milk production is infant demand. Thus, most interventions have focused on improving breastfeeding education and early lactation support. However, in addition to infant demand, increasing evidence from studies conducted in experimental animal models, production animals, and breastfeeding women suggests that a diverse array of maternal factors may also affect milk production and composition. In this review, we provide an overview of our current understanding of the role of maternal genetics and modifiable factors, such as diet and environmental exposures, on reproductive endocrinology, lactation physiology, and the ability to successfully produce milk. To identify factors that may affect lactation in women, we highlight some information gleaned from studies in experimental animal models and production animals. Finally, we highlight the gaps in current knowledge and provide commentary on future research opportunities aimed at improving lactation outcomes in breastfeeding women to improve the health of mothers and their infants.

Human milk and breastfeeding: An intervention to mitigate toxic stress

The American Academy of Nursing has identified toxic stress in childhood as a health policy concern of high priority. Adult diseases (e.g., obesity, diabetes, hypertension and cardiovascular disease) should be viewed as developmental disorders that begin early in life that could be reduced with the alleviation of toxic stress in childhood. The provision of human milk/breastfeeding is an evidence-based intervention that may hold the greatest potential to mitigate the effects of toxic stress from the moment of birth. Assisting families to make an informed choice to initiate and continue breastfeeding from birth has the potential to address both the disparity in the quality of nutrition provided infants and the economic stress experienced by families who purchase formula. The Expert Panel on Breastfeeding endorses initiatives to improve the initiation, duration, and exclusivity of breastfeeding to mitigate the effects of toxic stress in this call to action for research to build the evidence to support these critical relationships.

Human Milk Cells Contain Numerous miRNAs that May Change with Milk Removal and Regulate Multiple Physiological Processes

Human milk (HM) is a complex biofluid conferring nutritional, protective and developmental components for optimal infant growth. Amongst these are maternal cells, which change in response to feeding and were recently shown to be a rich source of miRNAs. We used next generation sequencing to characterize the cellular miRNA profile of HM collected before and after feeding. HM cells conserved higher miRNA content than the lipid and skim HM fractions or other body fluids, in accordance with previous studies. In total, 1467 known mature and 1996 novel miRNAs were identified, with 89 high-confidence novel miRNAs. HM cell content was higher post-feeding (p < 0.05), and was positively associated with total miRNA content (p = 0.014) and species number (p < 0.001). This coincided with upregulation of 29 known and 2 novel miRNAs, and downregulation of 4 known and 1 novel miRNAs post-feeding, but no statistically significant change in expression was found for the remaining miRNAs. These findings suggest that feeding may influence the miRNA content of HM cells. The most highly and differentially expressed miRNAs were key regulators of milk components, with potential diagnostic value in lactation performance. They are also involved in the control of body fluid balance, thirst, appetite, immune response, and development, implicating their functional significance for the infant.

Expression of Active Fluorophore Proteins in the Milk of Transgenic Pigs Bypassing the Secretory Pathway

We describe the expression of recombinant fluorescent proteins in the milk of two lines of transgenic pigs generated by Sleeping Beauty transposon-mediated genetic engineering. The Sleeping Beauty transposon consisted of an ubiquitously active CAGGS promoter driving a fluorophore cDNA, encoding either Venus or mCherry. Importantly, the fluorophore cDNAs did not encode for a signal peptide for the secretory pathway, and in previous studies of the transgenic animals a cytoplasmic localization of the fluorophore proteins was found. Unexpectedly, milk samples from lactating sows contained high levels of bioactive Venus or mCherry fluorophores. A detailed analysis suggested that exfoliated cells of the mammary epithelium carried the recombinant proteins passively into the milk. This is the first description of reporter fluorophore expression in the milk of livestock, and the findings may contribute to the development of an alternative concept for the production of bioactive recombinant proteins in the udder.

Human Milk Cells and Lipids Conserve Numerous Known and Novel miRNAs, Some of Which Are Differentially Expressed during Lactation

Human milk (HM) is rich in miRNAs, which are thought to contribute to infant protection and development. We used deep sequencing to profile miRNAs in the cell and lipid fractions of HM obtained post-feeding from 10 lactating women in months 2, 4, and 6 postpartum. In both HM fractions, 1,195 mature known miRNAs were identified, which were positively associated with the cell (p = 0.048) and lipid (p = 0.010) content of HM. An additional 5,167 novel miRNA species were predicted, of which 235 were high-confidence miRNAs. HM cells contained more known miRNAs than HM lipids (1,136 and 835 respectively, p<0.001). Although the profile of the novel miRNAs was very different between cells and lipids, with the majority conserved in the cell fraction and being mother-specific, 2/3 of the known miRNAs common between cells and lipids were similarly expressed (p>0.05). Great similarities between the two HM fractions were also found in the profile of the top 20 known miRNAs. These were largely similar also between the three lactation stages examined, as were the total miRNA concentration, and the number and expression of the known miRNAs common between cells and lipids (p>0.05). Yet, approximately a third of all known miRNAs were differentially expressed during the first 6 months of lactation (p<0.05), with more pronounced miRNA upregulation seen in month 4. These findings indicate that although the total miRNA concentration of HM cells and lipids provided to the infant does not change in first 6 months of lactation, the miRNA composition is altered, particularly in month 4 compared to months 2 and 6. This may reflect the remodeling of the gland in response to infant feeding patterns, which usually change after exclusive breastfeeding, suggesting adaptation to the infant’s needs.

Human milk miRNAs primarily originate from the mammary gland resulting in unique miRNA profiles of fractionated milk

Human milk (HM) contains regulatory biomolecules including miRNAs, the origin and functional significance of which are still undetermined. We used TaqMan OpenArrays to profile 681 mature miRNAs in HM cells and fat, and compared them with maternal peripheral blood mononuclear cells (PBMCs) and plasma, and bovine and soy infant formulae. HM cells and PBMCs (292 and 345 miRNAs, respectively) had higher miRNA content than HM fat and plasma (242 and 219 miRNAs, respectively) (p < 0.05). A strong association in miRNA profiles was found between HM cells and fat, whilst PBMCs and plasma were distinctly different to HM, displaying marked inter-individual variation. Considering the dominance of epithelial cells in mature milk of healthy women, these results suggest that HM miRNAs primarily originate from the mammary epithelium, whilst the maternal circulation may have a smaller contribution. Our findings demonstrate that unlike infant formulae, which contained very few human miRNA, HM is a rich source of lactation-specific miRNA, which could be used as biomarkers of the performance and health status of the lactating mammary gland. Given the recently identified stability, uptake and functionality of food- and milk-derived miRNA in vivo, HM miRNA are likely to contribute to infant protection and development.

Breastfeeding in the 21st century: epidemiology, mechanisms, and lifelong effect

The importance of breastfeeding in low-income and middle-income countries is well recognised, but less consensus exists about its importance in high-income countries. In low-income and middle-income countries, only 37% of children younger than 6 months of age are exclusively breastfed. With few exceptions, breastfeeding duration is shorter in high-income countries than in those that are resource-poor. Our meta-analyses indicate protection against child infections and malocclusion, increases in intelligence, and probable reductions in overweight and diabetes. We did not find associations with allergic disorders such as asthma or with blood pressure or cholesterol, and we noted an increase in tooth decay with longer periods of breastfeeding. For nursing women, breastfeeding gave protection against breast cancer and it improved birth spacing, and it might also protect against ovarian cancer and type 2 diabetes. The scaling up of breastfeeding to a near universal level could prevent 823,000 annual deaths in children younger than 5 years and 20,000 annual deaths from breast cancer. Recent epidemiological and biological findings from during the past decade expand on the known benefits of breastfeeding for women and children, whether they are rich or poor.

Pluripotency Genes and Their Functions in the Normal and Aberrant Breast and Brain

Pluripotent stem cells (PSCs) attracted considerable interest with the successful isolation of embryonic stem cells (ESCs) from the inner cell mass of murine, primate and human embryos. Whilst it was initially thought that the only PSCs were ESCs, in more recent years cells with similar properties have been isolated from organs of the adult, including the breast and brain. Adult PSCs in these organs have been suggested to be remnants of embryonic development that facilitate normal tissue homeostasis during repair and regeneration. They share certain characteristics with ESCs, such as an inherent capacity to self-renew and differentiate into cells of the three germ layers, properties that are regulated by master pluripotency transcription factors (TFs) OCT4 (octamer-binding transcription factor 4), SOX2 (sex determining region Y-box 2), and homeobox protein NANOG. Aberrant expression of these TFs can be oncogenic resulting in heterogeneous tumours fueled by cancer stem cells (CSC), which are resistant to conventional treatments and are associated with tumour recurrence post-treatment. Further to enriching our understanding of the role of pluripotency TFs in normal tissue function, research now aims to develop optimized isolation and propagation methods for normal adult PSCs and CSCs for the purposes of regenerative medicine, developmental biology, and disease modeling aimed at targeted personalised cancer therapies.

MicroRNAs in Breastmilk and the Lactating Breast: Potential Immunoprotectors and Developmental Regulators for the Infant and the Mother

Human milk (HM) is the optimal source of nutrition, protection and developmental programming for infants. It is species-specific and consists of various bioactive components, including microRNAs, small non-coding RNAs regulating gene expression at the post-transcriptional level. microRNAs are both intra- and extra-cellular and are present in body fluids of humans and animals. Of these body fluids, HM appears to be one of the richest sources of microRNA, which are highly conserved in its different fractions, with milk cells containing more microRNAs than milk lipids, followed by skim milk. Potential effects of exogenous food-derived microRNAs on gene expression have been demonstrated, together with the stability of milk-derived microRNAs in the gastrointestinal tract. Taken together, these strongly support the notion that milk microRNAs enter the systemic circulation of the HM fed infant and exert tissue-specific immunoprotective and developmental functions. This has initiated intensive research on the origin, fate and functional significance of milk microRNAs. Importantly, recent studies have provided evidence of endogenous synthesis of HM microRNA within the human lactating mammary epithelium. These findings will now form the basis for investigations of the role of microRNA in the epigenetic control of normal and aberrant mammary development, and particularly lactation performance.

Immune cell-mediated protection of the mammary gland and the infant during breastfeeding

Breastfeeding has been regarded first and foremost as a means of nutrition for infants, providing essential components for their unique growth and developmental requirements. However, breast milk is also rich in immunologic factors, highlighting its importance as a mediator of protection. In accordance with its evolutionary origin, the mammary gland offers via the breastfeeding route continuation of the maternal to infant immunologic support established in utero. At birth, the infant's immune system is immature, and although it was exposed to the maternal microbial flora during pregnancy, it experiences an abrupt change in its microbial environment during and after birth, which is challenging and renders the infant highly susceptible to infection. Active and passive immunity protects the infant via breast milk, which is rich in immunoglobulins, lactoferrin, lysozyme, cytokines, and numerous other immunologic factors, including maternal leukocytes. Breast milk leukocytes provide active immunity and promote development of immunocompetence in the infant. Additionally, it has been speculated that they play a role in the protection of the mammary gland from infection. Leukocytes are thought to exert these functions via phagocytosis, secretion of antimicrobial factors and/or antigen presentation in both the mammary gland and the gastrointestinal tract of the infant, and also in other infant tissues, where they are transported via the systemic circulation. Recently, it has been demonstrated that breast milk leukocytes respond dynamically to maternal as well as infant infections, and are fewer in nonexclusively compared with exclusively breastfeeding dyads, further emphasizing their importance for both the mother and infant. This review summarizes the current knowledge of human milk leukocytes and factors influencing them, and presents recent novel findings supporting their potential as a diagnostic marker for infections of the lactating breast and of the breastfed infant.