Pregnant Gland Research Articles

6693 Hypopituitarism in Pregnancy

Abstract Disclosure: N.A. Mcheik: None. H. Howarth: None. Background: Hypopituitarism in pregnancy requires careful management to ensure both maternal and fetal well-being. Disruptions of the pituitary gland in pregnancy can be due to adenomas, pituitary infarction, autoimmune disease, trauma, etc. Complications of hypopituitarism in pregnancy stem from inadequate production of thyroid stimulating hormone, growth hormone, gonadotropins and cortisol. Hormone replacement therapy will be necessary in such cases. For instance, patients in late pregnancy may require an increased dose of hydrocortisone due to the rise of corticosteroid-binding globulin. Patients may need increased doses of glucocorticoid therapy during labor given the major surgical stress. Antenatal care should include close follow up with endocrinologists and obstetricians and regular assessment of maternal hormone levels and fetal growth. Case: We present a case of a 37-year-old female G3P0020 at 24 weeks who presented with complaint of constant headache for 6 days. Associated with photophobia, intermittent blurry vision, nausea, and vomiting. She was admitted and given 1 g Magnesium bolus as well as Robaxin and Tylenol for headache without relief. Given persistence of symptoms and non-focal neurologic exam, MRI brain was completed that showed an enlarged pituitary gland with blood products. MRI pituitary showed an approximately 1.3 x 1.2 x 1.8 cm hemorrhagic lesion on the right side of pituitary gland with fluid level, most in keeping with hemorrhagic pituitary apoplexy. Thyroid function studies were consistent with central hypothyroidism with a low TSH 0.05, low Ft4 0.5, and normal Ft3 2.4. Luteinizing hormone was 0.1 mIU/mL (<1.5 normal in pregnancy), follicle stimulating hormone was <0.5 mIU/mL (<0.1 normal in pregnancy), estradiol >5000 pg/mL (1278-7192 normal in pregnancy), and prolactin 254 ng/mL (80-400 normal in pregnancy). IGF-1 was normal at 148 ng/ml. Morning cortisol was low at 1.8 ug/dL and ACTH was 9 pg/mL (low normal). Cortrosyn stimulation test at 60 minutes was normal at 17.7 ug/dL, however, given clinical improvement on steroids, the clinical picture is consistent with central hypoadrenalism. For treatment, she was started on IV hydrocortisone 50 mg every 8 hours and oral levothyroxine 100 mcg daily. The patient was discharged home on oral hydrocortisone 20 mg daily in the morning and 10 mg daily in the afternoon with close follow up. Conclusion: Ultimately, the management of hypopituitarism in pregnancy requires a personalized approach to hormone replacement and obstetric care and this is done through multidisciplinary care involving endocrinologists and obstetricians to optimize outcomes for both the mother and the baby. Presentation: 6/1/2024

6693 Hypopituitarism in Pregnancy

Abstract Disclosure: N.A. Mcheik: None. H. Howarth: None. Background: Hypopituitarism in pregnancy requires careful management to ensure both maternal and fetal well-being. Disruptions of the pituitary gland in pregnancy can be due to adenomas, pituitary infarction, autoimmune disease, trauma, etc. Complications of hypopituitarism in pregnancy stem from inadequate production of thyroid stimulating hormone, growth hormone, gonadotropins and cortisol. Hormone replacement therapy will be necessary in such cases. For instance, patients in late pregnancy may require an increased dose of hydrocortisone due to the rise of corticosteroid-binding globulin. Patients may need increased doses of glucocorticoid therapy during labor given the major surgical stress. Antenatal care should include close follow up with endocrinologists and obstetricians and regular assessment of maternal hormone levels and fetal growth. Case: We present a case of a 37-year-old female G3P0020 at 24 weeks who presented with complaint of constant headache for 6 days. Associated with photophobia, intermittent blurry vision, nausea, and vomiting. She was admitted and given 1 g Magnesium bolus as well as Robaxin and Tylenol for headache without relief. Given persistence of symptoms and non-focal neurologic exam, MRI brain was completed that showed an enlarged pituitary gland with blood products. MRI pituitary showed an approximately 1.3 x 1.2 x 1.8 cm hemorrhagic lesion on the right side of pituitary gland with fluid level, most in keeping with hemorrhagic pituitary apoplexy. Thyroid function studies were consistent with central hypothyroidism with a low TSH 0.05, low Ft4 0.5, and normal Ft3 2.4. Luteinizing hormone was 0.1 mIU/mL (<1.5 normal in pregnancy), follicle stimulating hormone was <0.5 mIU/mL (<0.1 normal in pregnancy), estradiol >5000 pg/mL (1278-7192 normal in pregnancy), and prolactin 254 ng/mL (80-400 normal in pregnancy). IGF-1 was normal at 148 ng/ml. Morning cortisol was low at 1.8 ug/dL and ACTH was 9 pg/mL (low normal). Cortrosyn stimulation test at 60 minutes was normal at 17.7 ug/dL, however, given clinical improvement on steroids, the clinical picture is consistent with central hypoadrenalism. For treatment, she was started on IV hydrocortisone 50 mg every 8 hours and oral levothyroxine 100 mcg daily. The patient was discharged home on oral hydrocortisone 20 mg daily in the morning and 10 mg daily in the afternoon with close follow up. Conclusion: Ultimately, the management of hypopituitarism in pregnancy requires a personalized approach to hormone replacement and obstetric care and this is done through multidisciplinary care involving endocrinologists and obstetricians to optimize outcomes for both the mother and the baby. Presentation: 6/1/2024

Physiological Changes of Thyroid Gland in Pregnancy

Women with hypothyroidism who did not take adequate medicine had a three times increased chance of developing preeclampsia. In the group that received inadequate treatment, preterm births and restrictions on the foetus's growth both increased dramatically. In the cohort I looked at, there was not a single incident of placental unexpectedness. It was discovered that the group who received poor treatment had a significantly higher incidence of oligohydramnios. When hypothyroidism is properly managed during pregnancy, pregnancy-related complications such as premature birth, toxaemia, intrauterine growth restriction (IUGR), oligohydramnios, glucose intolerance, preterm labour, low birth weight babies, abruptio placenta, and stillbirth are less likely to occur. Given that this study showed that women with pre-gestational diabetes mellitus frequently have thyroid impairment, it is important to check these women's thyroid function when they are pregnant. Thyroid dysfunction was present in both pregnant women with GDM and healthy pregnant women, but in 27% of them, TPO Ab titers were positive, indicating the need for additional testing for postpartum thyroiditis and dysfunction.

Recent Approach of Endocrine Function of Thyroid Gland and its Impact on Pregnancy

Introductions: Pregnancy is a period in which there are physical and hormonal changes for the development of the fetus and essentials nutrients supply and the preparation of the maternal organism for birth and lactation. There is a paucity of data on the endocrine function of the thyroid gland in pregnancy in Saudi Arabia. The purpose of this study was to assess the impact of the endocrine function of thyroid gland in pregnancy and current techniques for its management. Methods: In this systematic review and meta-analysis, PRISMA (preferred reporting items for systematic review and meta-analysis) was used. Cochrane handbook guidelines were used for all aspects of this study. It includes published and unpublished studies with different study designs. Such studies were found from databases which include Google Scholar, Embase Medline, PsycINFO, Google, and Cochrane library up to the last week of January 2022 without any language restriction and identified all RCTs related to the endocrine function of the thyroid gland and its impact on pregnancy. Results: All RCTs connected to the endocrine function of the thyroid gland and its impact on pregnancy were found using a total of 304 articles from the electronic database Google Scholar, PubMed, Embase, PsycINFO, and the Cochrane Library, which were searched without any language restrictions. ''Endocrine'', ''Endocrine function'', ''Thyroid'', ''TSH’’, ‘‘T3’’, ‘‘T4’’, ‘‘hormones’’ and ‘‘pregnancy’’ and ‘‘randomized controlled trial’’ were some of the search terms we utilized. In addition, we searched references in a few journals to find more potentially relevant studies. Due to redundancy, 92 articles were excluded from the total of 304. A total of 107 articles were reviewed, with 77 rejected following a preliminary review. There were 30 full-text papers reviewed for eligibility, and 10 of them met the inclusion requirements, with all of the selected articles being of high quality. The parameters of the trials differed greatly in terms of treatment length and population investigated. All of the studies were nonrandomized and compared groups based on retrospective chart reviews. Out of 10 studies, three were from Iran, two from Saudi Arabia, one from the United States, one from Denmark, one from Ireland, one from Netherland, and one from Australia.

H2AX Promoter Demethylation at Specific Sites Plays a Role in STAT5-Induced Tumorigenesis.

Deregulated STAT5 activity in the mammary gland of transgenic mice results in parity-dependent latent tumorigenesis. The trigger for cell transformation was previously associated with hyperactivation of the H2AX proximal promoter in a small basal cell population during pregnancy. The current study focuses on the latent activation of tumor development. H2AX was highly expressed in carcinoma and adenocarcinoma as compared to the multiparous mammary gland, whereas pSTAT5 expression decreased in a tumor type-dependent manner. In contrast to the pregnant gland, no positive correlation between H2AX and pSTAT5 expression could be defined in carcinoma and adenocarcinoma. Using targeted methylation analysis, the methylation profile of the H2AX promoter was characterized in the intact gland and tumors. Average H2AX promoter methylation in the tumors was relatively high (~90%), but did not exceed that of the multiparous gland; 5mC methylation was higher in the differentiated tumors and negatively correlated with its oxidative product 5hmC and H2AX expression. Individual analysis of 25 H2AX promoter-methylation sites revealed two consecutive CpGs at positions -77 and - 54 that were actively demethylated in the multiparous gland, but not in their age-matched virgin counterpart. The different methylation profiles at these sites distinguished tumor types and may assume a prognostic role. In-silico and ChIP analyses revealed overlapping methylation-independent SP1-binding and methylation-dependent p53-binding to these sites. We propose that interference with SP1-assisted p53-binding to these sites abrogates H2AX's ability to arrest the cell cycle upon DNA damage, and contributes to triggering latent development of STAT5-induced tumors in estrapausal multiparous mice.

Hyperthyroid in Pregnancy: A Case Report

Hyperthyroidism in pregnancy is generally caused by Grave's disease which can cause thyroid crises, premature, abortion and fetal death. Graves disease often becomes more severe in the first trimester of pregnancy and will experience an exacerbation in the postpartum period. A 35-year-old woman with a third pregnancy 23-24 weeks with fetal death in the womb. The patient has been suffering from Grave's disease for 10 years but has not taken the drug for the past 1 year. No history of trauma and bleeding. FT4 levels 75.62 pmol / L and TSHs levels 0.005 µIU / mL. Wayne's index score is 23 and the Burch Wartofsky scale is 45 or impending thyroid storm. Management of hyperthyroidism is given before termination of pregnancy. Pulmonary breath shortness at two hours after delivery and given a diuretic and vasodilator. Supervision is carried out until the patient's condition improves. The function of the thyroid gland in pregnancy is increased which is influenced by increased levels of thyroxin binding globulin (TBG), thyroid-stimulating factors (TSF) from the placenta and decreased iodine supply in the thyroid gland. These complaints are more severe in the first trimester of pregnancy and will experience an exacerbation in the postpartum period. In inadequate treatment, hyperthyroidism complicated to maternal heart failure and fetal death. Hyperthyroidism can cause complications in the mother and fetus and increase morbidity and mortality. Proper initial treatment will improve outcomes.

Commercial Artificial Sweeteners Might Affect Pregnant and Nursing Mice Mammary Gland. A Histological Study

The use of artificial sweeteners as non-nutritive food additive is becoming very common nowadays. The aim of this research was to study the effect of commercial artificial sweeteners consumption on the adult mouse mammary gland in pregnancy (18-day pregnancy) and 3 weeks nursing. A commercial artificial sweetener solution was given to pregnant mice of treated groups 50 mg/kg body weight, from day one of pregnancy till the end of 3 weeks nursing. Controls were given distilled water. The histological studies of the mammary gland of treated animals showed some changes. In treated 18-day pregnant mothers; the amount of adipose cells seemed to increase and the amount of lipid droplets within the alveoli seemed to increase compared to the controls. Also alveoli in the treated mammary gland sections appeared to be larger and less in number compared to the controls. In 3 weeks treated nursing mothers the amount of milk and lipid droplets in the alveoli decreased compared to the controls. The mammary gland circumference of treated 18-day pregnant mothers was significantly smaller compared to the controls, while it was significantly larger in 3 weeks treated nursing mothers compared to the controls. These results show that artificial sweeteners disturbed the arrangement of the histological structure in the mammary gland of pregnant and nursing mice. Awareness should be raised to restrict the use of artificial sweeteners to people with diabetes or who are in medical need.

Thyroid papillary cancer-related pregnancy: a case report

Abstract Differentiated thyroid cancer is the second-most frequent tumor among those tumors diagnosed during pregnancy after breast cancer; it also is the most common endocrine malignancy. Pregnancy-associated cancer was defined as a malignancy detected during pregnancy or within 2 years of delivery, but most of the patients with pregnancy-associated cancer were recognized in the postpartum period. The best time for surgery is unclear. Its management is a challenge for both doctors and patients. Enlargement of the thyroid gland in pregnancy is usually a physiological change related to pregnancy, but even if it is rare, it can be due to thyroid malignancy. We report a case of 31-year-old female diagnosed with thyroid papillary cancer during pregnancy with no symptoms except for a lump on her neck. For this reason, the examination of the thyroid gland and the examination of neck lymph nodes should be routinely performed on all pregnant women.

RANKL/RANK: from bone loss to the prevention of breast cancer.

RANK and RANKL, a receptor ligand pair belonging to the tumour necrosis factor family, are the critical regulators of osteoclast development and bone metabolism. Besides their essential function in bone, RANK and RANKL have also been identified as the key factors for the formation of a lactating mammary gland in pregnancy. Mechanistically, RANK and RANKL link the sex hormone progesterone with stem cell expansion and proliferation of mammary epithelial cells. Based on their normal physiology, RANKL/RANK control the onset of hormone-induced breast cancer through the expansion of mammary progenitor cells. Recently, we and others were able to show that RANK and RANKL are also critical regulators of BRCA1-mutation-driven breast cancer. Currently, the preventive strategy for BRCA1-mutation carriers includes preventive mastectomy, associated with wide-ranging risks and psychosocial effects. The search for an alternative non-invasive prevention strategy is therefore of paramount importance. As our work strongly implicates RANK and RANKL as key molecules involved in the initiation of BRCA1-associated breast cancer, we propose that anti-RANKL therapy could be a feasible preventive strategy for women carrying BRCA1 mutations, and by extension to other women with high risk of breast cancer.

Biological roles of uterine glands in pregnancy.

All mammalian uteri contain glands in the endometrium that synthesize or transport and secrete substances essential for survival and development of the conceptus (embryo/fetus and associated extraembryonic membranes). This review summarizes information related to the biological roles of uterine glands and their secretions in blastocyst/conceptus survival and implantation, uterine receptivity, and stromal cell decidualization in humans and animal models. The infertility and recurrent pregnancy loss observed in the ovine uterine gland knockout (UGKO) model unequivocally supports a primary role for uterine glands and, by inference, their secretions present in uterine luminal fluid in survival and development of the conceptus. Further, studies with mutant and progesterone-induced UGKO mice found that uterine glands and their secretions are required for establishment of uterine receptivity and blastocyst implantation as well as stromal cell decidualization. Similarly in humans, uterine glands and their secretory products are likely critical regulators of blastocyst implantation, uterine receptivity, and conceptus growth and development during the first trimester. Circumstantial evidence suggests that deficient glandular activity may be a causative factor in pregnancy failure and complications in humans. Thus, an increased understanding of uterine gland biology is important for diagnosis, prevention, and treatment of fertility and pregnancy problems in mammals.

The crucial role of osteocyte-derived RANKL in bone homeostasis

Receptor activator of NF-κB ligand (RANKL; also known as TNFSF11), a TNF family molecule, and its receptor RANK (TNFRSF11A) are key regulators of osteoclast differentiation and function. Aberrant expression of RANKL explains why autoimmune diseases, cancers, leukemia and periodontal disease result in systemic and local bone loss. In particular, RANKL is the pathogenic factor that cause bone and cartilage destruction in arthritis. Inhibition of RANKL function by the natural decoy receptor osteoprotegerin (OPG; also known as TNFRSF11B) or anti-RANKL antibody prevents bone loss in postmenopausal osteoporosis, cancer metastases and arthritis. RANKL also regulates T cell/dendritic cell communications, dendritic cell survival and lymph node organogenesis. Intriguingly, RANKL and RANK play an essential role in the maturation of mammary glands in pregnancy and lactation. Bone homeostasis depends on the coordination of osteoclastic bone resorption and osteoblastic bone formation. We reported that RANKL induces osteoclast differentiation through activating a transcriptional programme mediated by the master transcription factor nuclear factor of activated T cells (NFAT) c1. Although it is well accepted that the RANKL-NFATc1 pathway is crucially important for osteoclast differentiation, little is known about the major cellular source of RANKL in the skeletal tissue. RANKL has been postulated to be mainly expressed by osteoblasts and bone marrow stromal cells. However, here we show that osteocytes embedded within the bone matrix are the critical source of RANKL in bone remodeling. Osteocytes, the most abundant cell type in bone, are thought to orchestrate bone homeostasis by regulating both osteoclastic bone resorption and osteoblastic bone formation, but in vivo evidence and the molecular basis for the regulation has not been sufficiently demonstrated. Using a newly established method for the isolation of high-purity dentin matrix protein 1-positive osteocytes from bone, we have found that osteocytes express a much higher amount of RANKL and have a much greater capacity to support osteoclast formation than osteoblasts and bone marrow stromal cells. The crucial role of RANKL expressed by osteocytes was validated by the severe osteopetrotic phenotype observed in mice lacking RANKL specifically in osteocytes. Thus, we provide in vivo evidence for the key role of osteocyte-derived RANKL in bone homeostasis, establishing a molecular basis for osteocyte regulation of bone resorption.

Development and Function of Murine B Cells Lacking RANK

RANKL-RANK signaling regulates numerous physiologic processes such as bone remodeling, lymph node organogenesis, central thermoregulation, and formation of a lactating mammary gland in pregnancy. Recently, a receptor activator of NF-κB ligand (RANKL)-blocking Ab has been approved for human use in potentially millions of osteoporosis and cancer patients. However, germline deficiencies in RANKL or receptor activator of NF-κB (RANK) also lead to strong B cell defects in mice and human patients, suggesting that RANKL-RANK inhibition could interfere with B cell physiology and thereby trigger immunologic side-effects. To address this key question--that is, whether RANKL-RANK signaling affects B cell physiology directly or the observed defects are secondary because of the severe osteopetrosis--we generated B cell-specific RANK knockout mice. We show that B cells deficient for RANK undergo normal development and do not show any obvious defects in Ab secretion, class switch recombination, or somatic hypermutation. Our data indicate that ablation of the RANKL-RANK pathway has no direct adverse effect on B cell physiology.

Excess ATP7A reduces the copper content of the mammary gland in pregnancy and lactation but does not alter levels of plasma ceruloplasmin

Two Cu pumps, ATP7A and B, are critical for Cu transport and homeostasis in mammalian metabolism. Mammary gland (MG) and placenta are somewhat unique in expressing both ATPases, and the question arises as to their separate functions. We hypothesized that in the lactating MG, ATP7B promotes entry of Cu into the milk, while ATP7A promotes efflux of excess Cu back into the blood. In lactating human breast we showed with confocal microscopy that ATP7A was localized in the basolateral membrane. It moved towards the basolateral membrane from the TGN in response to lactational hormones in the PMC42 cell breast model. In transgenic mice with human ATP7A expression 10–20 fold higher than endogenous mouse Atp7a, total Cu in the mammary gland, brain and kidney was reduced. Hepatic Cu and plasma ceruloplasmin were unchanged; however, plasma ferroxidase activity was significantly higher in the transgenic animals. In lactation and throughout gestation, MG had half as much Cu as the wild type, as did the milk. Uptake of 64Cu tracer by MG 1h after i.p. injection increased about 3‐fold from early to late gestation in the wild type but was significantly lower in the ATP7A overexpressing mice. These findings are consistent with the concept that ATP7A promotes “backflow” of Cu from mammary epithelial cells to the maternal blood, not just in lactation but also during gestational mammary gland development. Supported by USPHS Grant HD 46949.

Wnt4 is not sufficient to induce lobuloalveolar mammary development

BackgroundBrisken et al (2000) showed that Wnt4 null mammary glands were deficient in early lobuloalveolar mammary outgrowth during pregnancy, and implicated Wnt4 as an effector for the progesterone-induced mammary growth program. Though ectopic Wnt1 signaling is known to be mitogenic and oncogenic, no endogenously expressed Wnt ligands have ever been directly implicated in mammary growth and morphogenesis. Therefore, we generated conditional transgenic mice to test whether Wnt4 can stimulate mammary epithelial cell growth.ResultsWe found that despite pregnancy-associated expression levels of Wnt4, mammary glands did not display the side-branching typical of early pregnancy. Control experiments designed to test the Wnt4 construct in zebrafish reproduced other studies that demonstrated Wnt4-specific phenotypes distinct from Wnt1-induced phenotypes. Indeed, using qPCR-based array analyses, we found that a specific transcriptional target of Wnt4, namely Wnt16, was induced in Wnt4-expressing transgenic glands, to levels equivalent to that of early pregnant glands.ConclusionTaken together, we propose that Wnt4 is necessary, but not sufficient, to induce side-branch development.

Activation of Stat5 and induction of a pregnancy‐like mammary gland differentiation by eicosapentaenoic and docosapentaenoic omega‐3 fatty acids

The protective effect of early pregnancy against breast cancer can be attributed to the transition from undifferentiated cells in the nulliparous to the differentiated mature cells during pregnancy. Considerable evidence suggests strongly that the n-3 polyunsaturated fatty acid (PUFA) content of adipose breast tissue is inversely associated with an increased risk of breast cancer. Here, we report that there was a decrease in the n-6/n-3 PUFA ratio and a significant increase in concentration of n-3 PUFA docosapentaenoic acid and eicosapentaenoic acid in the pregnant gland. The functional role of n-3 PUFAs on differentiation was supported by the studies in the fat-1 transgenic mouse, which converts endogenous n-6 to n-3 PUFAs. Alternation of the n-6/n-3 ratio in favor of n-3 PUFA, and particularly docosapentaenoic acid, in the mammary gland of fat-1 mouse resulted in development of lobulo-alveolar-like structure and milk protein beta-casein expression, mimicking the differentiated state of the pregnant gland. Docosapentaenoic acid and eicosapentaenoic acid activated the Jak2/Stat5 signaling pathway and induced a functional differentiation with production of beta-casein. Expression of brain type fatty acid binding protein brain type fatty acid binding protein in virgin transgenic mice also resulted in a reduced ratio of n-6/n-3 PUFA, a robust increase in docosapentaenoic acid accumulation, and mammary differentiation. These data indicate a role of mammary derived growth inhibitor related gene for preferential accumulation of n-3 docosapentaenoic acid and eicosapentaenoic acid in the differentiated gland during pregnancy. Thus, alternation of n-6/n-3 fatty acid compositional ratio in favor of n-3 PUFA, and particularly docosapentaenoic acid and eicosapentaenoic acid, is one of the underlying mechanisms of pregnancy-induced mammary differentiation.

Production of parathyroid hormone-related protein by the rat mammary gland in pregnancy and lactation.

Production of parathyroid hormone-related protein by the rat mammary gland in pregnancy and lactation. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E1077-E1085, 1992.--Production of parathyroid hormone-related protein (PTHrP) by the mammary gland of Sprague-Dawley rats has been examined using immunohistochemistry and in situ hybridization to detect PTHrP and PTHrP mRNA, respectively. PTHrP and PTHrP mRNA could be demonstrated in nests of epithelial cells of the developing mammary gland at day 14 of pregnancy and in the epithelial secretory cells lining the alveoli during the latter stages of pregnancy and during lactation. A specific radioimmunoassay was also used to measure the concentration of PTHrP secreted in the milk throughout lactation. The concentration of PTHrP in milk was relatively low initially but increased during the latter stages of lactation, whereas calcium concentrations remained virtually constant throughout lactation. No correlation was found between the concentrations of calcium and PTHrP in rat milk. These results show that PTHrP is present in rat milk and also in mammary tissue before parturition, and therefore it may assist in the development of the mammary gland during pregnancy.

Circadian clock and cell cycle gene expression in mouse mammary epithelial cells and in the developing mouse mammary gland

Mouse mammary epithelial cells (HC-11) and mammary tissues were analyzed for developmental changes in circadian clock, cellular proliferation, and differentiation marker genes. Expression of the clock genes Per1 and Bmal1 were elevated in differentiated HC-11 cells, whereas Per2 mRNA levels were higher in undifferentiated cells. This differentiation-dependent profile of clock gene expression was consistent with that observed in mouse mammary glands, as Per1 and Bmal1 mRNA levels were elevated in late pregnant and lactating mammary tissues, whereas Per2 expression was higher in proliferating virgin and early pregnant glands. In both HC-11 cells and mammary glands, elevated Per2 expression was positively correlated with c-Myc and Cyclin D1 mRNA levels, whereas Per1 and Bmal1 expression changed in conjunction with beta-casein mRNA levels. Interestingly, developmental stage had differential effects on rhythms of clock gene expression in the mammary gland. These data suggest that circadian clock genes may play a role in mouse mammary gland development and differentiation.

Elf5 is essential for early embryogenesis and mammary gland development during pregnancy and lactation

Elf5 is an epithelial-specific ETS factor. Embryos with a null mutation in the Elf5 gene died before embryonic day 7.5, indicating that Elf5 is essential during mouse embryogenesis. Elf5 is also required for proliferation and differentiation of mouse mammary alveolar epithelial cells during pregnancy and lactation. The loss of one functional allele led to complete developmental arrest of the mammary gland in pregnant Elf5 heterozygous mice. A quantitative mRNA expression study and Western blot analysis revealed that decreased expression of Elf5 correlated with the downregulation of milk proteins in Elf5(+/-) mammary glands. Mammary gland transplants into Rag(-/-) mice demonstrated that Elf5(+/-) mammary alveolar buds failed to develop in an Elf5(+/+) mammary fat pad during pregnancy, demonstrating an epithelial cell autonomous defect. Elf5 expression was reduced in Prolactin receptor (Prlr) heterozygous mammary glands, which phenocopy Elf5(+/-) glands, suggesting that Elf5 and Prlr are in the same pathway. Our data demonstrate that Elf5 is essential for developmental processes in the embryo and in the mammary gland during pregnancy.

Tissue involution and the acute phase response.

After their roles in reproduction are completed, the mass of the uterus and the mammary gland decrease rapidly by the process of involution that involves an ordered series of events including apoptosis, neutrophil entry, the release of degradative enzymes, and phagocytosis of cellular debris. The acute phase proteins are produced by the liver and other tissues in response to inflammation or a toxic challenge. Uterocalin (SIP24/24p3) is one of these proteins. During involution, the mammary gland and uterus express high levels of uterocalin that reach an average of 0.2-0.5% of the total extractable protein at its peak. Uterocalin and its orthologues have been demonstrated in vitro to (1). bind certain fatty acids and (2). specifically induce apoptosis in neutrophils and other leukocytes. The period of uterocalin expression during involution is consistent with the hypothesis that one of its physiological roles is to induce apoptosis of invading neutrophils and delay the entry of neutrophils into the tissue until the second phase of involution. Interestingly, it has been shown that uterocalin expression remains higher in primiparous gland than in virgin glands after the pregnant glands have completely involuted. This observation and the known protective effect of early pregnancy on later development of breast cancer suggest that the ability of uterocalin to induce apoptosis in neutrophils might also decrease oxidative and carcinogenic activity in the gland and result in a lower mutation rate and thus a lower probability of cancer in the primiparous gland.

Prolactin gene expression in the mouse nipple.

In this study, we attempted to examine the presence of prolactin (PRL) messenger ribonucleic acid (mRNA) and protein in the mouse nipple and mammary gland in pregnancy and lactation. PRL-like substances were found by immunohistochemistry using an antibody against the mouse PRL (mPRL) in the sebaceous gland cells of the nipple during late pregnancy and lactation, and the cistern of alveoli in mammary glands during lactation. Western blot analysis of proteins extracted from the nipple and the mammary gland showed immunoreactive bands corresponding to molecular weights of approximate 16 kDa and 32 kDa, respectively. The expression of mRNA for mPRL in the nipple and mammary gland during late pregnancy and lactation was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR), Southern blotting, and nucleotide sequence analyses. These results suggest that mPRL mRNA and its translation product are synthesized in the mouse nipple.