Emerging evidence of the physiological role of hypoxia in mammary development and lactation

Lithium Chloride Promotes Endogenous Synthesis of CLA in Bovine Mammary Epithelial Cells

Although conjugated linoleic acid (CLA) can promote human health, its content in milk is insufficient to have a significant impact. The majority of the CLA in milk is produced endogenously by the mammary gland. However, research on improving its content through nutrient-induced endogenous synthesis is relatively scarce. Previous research found that the key enzyme, stearoyl-CoA desaturase (SCD) for the synthesis of CLA, can be expressed more actively in bovine mammary epithelial cells (MAC-T) when lithium chloride (LiCl) is present. This study investigated whether LiCl can encourage CLA synthesis in MAC-T cells. The results showed that LiCl effectively increased SCD and proteasome α5 subunit (PSMA5) protein expression in MAC-T cells as well as the content of CLA and its endogenous synthesis index. LiCl enhanced the expression of proliferator-activated receptor-γ (PPARγ), sterol regulatory element-binding protein 1 (SREBP1), and its downstream enzymes acetyl CoA carboxylase (ACC), fatty acid synthase (FASN), lipoprotein lipase (LPL), and Perilipin 2 (PLIN2). The addition of LiCl significantly enhanced p-GSK-3β, β-catenin, p-β-catenin protein expression, hypoxia-inducible factor-1α (HIF-1α), and downregulation factor genes for mRNA expression (P < 0.05). These findings highlight that LiCl can increase the expression of SCD and PSMA5 by activating the transcription of HIF-1α, Wnt/β-catenin, and the SREBP1 signaling pathways to promote the conversion of trans-vaccenic acid (TVA) to the endogenous synthesis of CLA. This data suggests that the exogenous addition of nutrients can increase CLA content in milk through pertinent signaling pathways.

Single-Cell Transcription Mapping of Murine and Human Mammary Organoids Responses to Female Hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

Single-cell transcription mapping of murine and human mammary organoids responses to female hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

CeRNA Network Reveals the Circular RNA Characterization in Goat Ear Fibroblasts Reprogramming into Mammary Epithelial Cells

Circular RNAs (circRNAs) are a type of non-coding RNA that play a crucial role in the development and lactation of mammary glands in mammals. A total of 107 differentially expressed circRNAs (DE circRNAs) were found, of which 52 were up-regulated and 55 were down-regulated. We also found that DE circRNA host genes were mainly involved in GO terms related to the development process of mammary epithelial cells and KEGG pathways were mostly related to mammary epithelial cells, lactation, and gland development. Protein network analysis found that DE circRNAs can competitively bind to miRNAs as key circRNAs by constructing a circRNA-miRNA-mRNA network. CircRNAs competitively bind to miRNAs (miR-10b-3p, miR-671-5p, chi-miR-200c, chi-miR-378-3p, and chi-miR-30e-5p) involved in goat mammary gland development, mammary epithelial cells, and lactation, affecting the expression of core genes (CDH2, MAPK1, ITGB1, CAMSAP2, and MAPKAPK5). Here, we generated CiMECs and systematically explored the differences in the transcription profile for the first time using whole-transcriptome sequencing. We also analyzed the interaction among mRNA, miRNA, and cirRNA and predicted that circRNA plays an important role in the maintenance of mammary epithelial cells.

Heat stress affects dairy cow health status through blood oxygen availability

BACKGROUND

Rises in global warming and extreme weather occurrence make the risk of heat stress (HS) induced by high ambient temperatures more likely in high-yielding dairy cows, resulting in low milk quality and yield. In animals, oxygen is involved in many physiological and metabolic processes, but the effects of HS on oxygen metabolism remain unclear. Thus, the current study aimed to investigate how oxygen metabolism plays a role in health status of dairy cows by measuring the milk yield, milk composition, and blood biochemical variables of cows under different levels of HS: none (No-HS), mild (Mild-HS), and moderate HS (Mod-HS).

RESULTS

The HS significantly increased rectal temperature (Ptreat < 0.01) and respiration rate (Ptreat < 0.01). Under Mod-HS, greater Na+ (P < 0.05) and lower total CO2, and pH (P < 0.05) were observed relative to those under No-HS and Mild-HS. Oxygen concentrations in both coccygeal artery and mammary vein (Ptreat < 0.01) were lower under Mod-HS than under No-HS. Coccygeal vein concentrations of heat shock protein 90 (HSP90) (P < 0.05) increased during Mod-HS compared with those in cows under No-HS. Malondialdehyde increased during Mod-HS, and glutathione peroxidase (P < 0.01) increased during Mild-HS. Coccygeal vein concentrations of vascular endothelial growth factor (P < 0.01), heme oxygenase-1 (P < 0.01), and hypoxia-inducible factor 1α (P < 0.01) were greater in cows under Mod-HS than those under No-HS. Red blood cell count (P < 0.01) and hemoglobin concentration (P < 0.01) were lower in the coccygeal vein of dairy cows under Mild- and Mod-HS than those of cows under No-HS.

CONCLUSIONS

Exposure to HS negatively impacts the health status and lactation performance of dairy cows by limiting oxygen metabolism and transportation. However, the specific mechanism by which HS affects mammary function in cows remains unclear and requires further exploration.

SIM2s directed Parkin-mediated mitophagy promotes mammary epithelial cell differentiation

The functionally differentiated mammary gland adapts to extreme levels of stress from increased demand for energy by activating specific protective mechanisms to support neonatal health. Here, we identify the breast tumor suppressor gene, single-minded 2 s (SIM2s) as a novel regulator of mitophagy, a key component of this stress response. Using tissue-specific mouse models, we found that loss of Sim2 reduced lactation performance, whereas gain (overexpression) of Sim2s enhanced and extended lactation performance and survival of mammary epithelial cells (MECs). Using an in vitro model of MEC differentiation, we observed SIM2s is required for Parkin-mediated mitophagy, which we have previously shown as necessary for functional differentiation. Mechanistically, SIM2s localizes to mitochondria to directly mediate Parkin mitochondrial loading. Together, our data suggest that SIM2s regulates the rapid recycling of mitochondria via mitophagy, enhancing the function and survival of differentiated MECs.

Lithium Chloride Promotes Milk Protein and Fat Synthesis in Bovine Mammary Epithelial Cells via HIF-1α and β-Catenin Signaling Pathways

Lithium is one of the trace elements with many physiological properties, such as being anti-cancer, anti-viral, and anti-inflammatory. However, little is known about its effect on milk synthesis during lactation. Therefore, we selected different concentrations (5 mM, 10 mM, and 20 mM) of lithium chloride (LiCl) and assessed the effect of LiCl on bovine mammary epithelial (MAC-T) cells that underwent 4 days of differentiation induction. Moreover, we analyzed the effect of LiCl on the expression of genes related to milk fat and milk protein synthesis. Herein, LiCl (5-20 mM) significantly increased the expression of β-casein, promoted mRNA expression and phosphorylated protein expression of the signal transduction molecule and activator of transcription 5β (STAT5-β), and inhibited mRNA and protein expression of suppressor of cytokine signaling 2 (SOCS2). In contrast, 5 and 10 mM LiCl significantly inhibited expression of SOCS3. LiCl at concentration of 5-20 mM enhanced phosphorylation level of mTOR protein; at 10 mM and 20 mM, LiCl significantly promoted expression and phosphorylation of downstream ribosomal protein S6 kinase beta-1 (S6K1) protein. Considering milk fat synthesis, mRNA expression of acetyl CoA carboxylase (ACC) and lipoprotein lipase (LPL) genes was considerably increased in the presence of LiCl (5-20 mM). Additionally, increased protein expression levels of stearoyl-CoA desaturase (SCD), peroxisome proliferator-activated receptor-γ (PPARγ), and sterol regulatory element-binding protein 1 (SREBP1) were observed at all LiCl concentrations tested. Subsequently, LiCl (5-20 mM) significantly promoted protein expression and phosphorylation of β-catenin, while 10 mM and 20 mM of LiCl significantly promoted protein expression of hypoxia-inducible factor-1α (HIF-1α). Collectively, it has been shown that 10 mM LiCl can effectively activate HIF-1α, β-catenin, and β-catenin downstream signaling pathways. Conversely, at 10 mM, LiCl inhibited SOCS2 and SOCS3 protein expression through JAK2/STAT5, mTOR, and SREBP1 signaling pathways, improving synthesis of milk protein and fat. Therefore, LiCl can be used as a potential nutrient to regulate milk synthesis in dairy cows.

Structural Characterization of the Interaction of Hypoxia Inducible Factor-1 with Its Hypoxia Responsive Element at the -964G > A Variation Site of the HLA-G Promoter Region

Human Antigen Leukocyte-G (HLA-G) gene encodes an immune checkpoint molecule that has restricted tissue expression in physiological conditions; however, the gene may be induced in hypoxic conditions by the interaction with the hypoxia inducible factor-1 (HIF1). Hypoxia regulatory elements (HRE) located at the HLA-G promoter region and at exon 2 are the major HIF1 target sites. Since the G allele of the −964G > A transversion induces higher HLA-G expression when compared to the A allele in hypoxic conditions, here we analyzed HIF1-HRE complex interaction at the pair-atom level considering both −964G > A polymorphism alleles. Mouse HIF2 dimer crystal (Protein Data Bank ID: 4ZPK) was used as template to perform homology modelling of human HIF1 quaternary structure using MODELLER v9.14. Two 3D DNA structures were built from 5′GCRTG’3 HRE sequence containing the −964G/A alleles using x3DNA. Protein-DNA docking was performed using the HADDOCK v2.4 server, and non-covalent bonds were computed by DNAproDB server. Molecular dynamic simulation was carried out per 200 ns, using Gromacs v.2019. HIF1 binding in the HRE containing −964G allele results in more hydrogen bonds and van der Waals contact formation than HRE with −964A allele. Protein-DNA complex trajectory analysis revealed that HIF1-HRE-964G complex is more stable. In conclusion, HIF1 binds in a more stable and specific manner at the HRE with G allele.

Beta-Sitosterol Promotes Milk Protein and Fat Syntheses-Related Genes in Bovine Mammary Epithelial Cells

Simple Summary

The levels of milk fats and proteins are important indexes used to evaluate milk quality. Generally, feed additives are used to improve milk quality. This study aimed to investigate the effect of β-sitosterol on milk fat and protein gene expression in bovine mammary epithelial cells. β-sitosterol increased the β-casein levels in bovine mammary epithelial cells and promoted the expression of milk fat and protein synthesis-related genes, suggesting the use of β-sitosterol as a potential feed additive to improve milk quality in dairy cows.

Abstract

β-sitosterol, a phytosterol with multiple biological activities, has been used in the pharmaceutical industry. However, there are only a few reports on the use of β-sitosterol in improving milk synthesis in dairy cows. This study aimed to investigate the effects of β-sitosterol on milk fat and protein syntheses in bovine mammary epithelial cells (MAC-T) and its regulatory mechanism. MAC-T cells were treated with different concentrations (0.01, 0.1, 1, 5, 10, 20, 30, or 40 μM) of β-sitosterol, and the expression levels of milk protein and fat synthesis-related genes and proteins were analyzed. β-sitosterol at 0.1, 1, and 10 μM concentrations promoted the mRNA and protein expression of β-casein. β-sitosterol (0.1, 1, 10 μM) increased the mRNA and protein expression levels of signal transducer activator of transcription 5 (STAT5), mammalian target of rapamycin (mTOR), and ribosomal protein S6 kinase beta-1 (S6K1) of the JAK2/STAT5 and mTOR signaling pathways. It also stimulated the milk fat synthesis-related factors, including sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor-gamma (PPARγ), acetyl-CoA carboxylase (ACC), lipoprotein lipase (LPL), and stearyl CoA desaturase (SCD). β-sitosterol (0.1, 1, 10 μM) also significantly increased the expression of growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and hypoxia-inducible factor-1α (HIF-1α)-related genes. Notably, the compound inhibited the expression of the negative regulator, the suppressor of cytokine signaling 2 (SOCS2) at the two lower concentrations (0.1, 1 μM), but significantly promoted the expression at the highest concentration (30 μM). These results highlight the role of β-sitosterol at concentrations ranging from 0.1 to 10 μM in improving milk protein and fat syntheses, regulating milk quality. Therefore, β-sitosterol can be used as a potential feed additive to improve milk quality in dairy cows.

Normalization of the tumor microvasculature based on targeting and modulation of the tumor microenvironment

Angiogenesis is an essential process for tumor development. Owing to the imbalance between pro- and anti-angiogenic factors, the tumor vasculature possesses the characteristics of tortuous, hyperpermeable vessels and compressive force, resulting in a reduction in the effect of traditional chemotherapy and radiotherapy. Anti-angiogenesis has emerged as a promising strategy for cancer treatment. Tumor angiogenesis, however, has been proved to be a complex process in which the tumor microenvironment (TME) plays a vital role in the initiation and development of the tumor microvasculature. The host stromal cells in the TME, such as cancer associated fibroblasts (CAFs), tumor associated macrophages (TAMs) and Treg cells, contribute to angiogenesis. Furthermore, the abnormal metabolic environment, such as hypoxia and acidosis, leads to the up-regulated expression of angiogenic factors. Indeed, normalization of the tumor microvasculature via targeting and modulating the TME has become a promising strategy for anti-angiogenesis and anti-tumor therapy. In this review, we summarize the abnormalities of the tumor microvasculature, tumor angiogenesis induced by an abnormal metabolic environment and host stromal cells, as well as drug delivery therapies to restore the balance between pro- and anti-angiogenic factors by targeting and normalizing the tumor vasculature in the TME.

Sodium salicylate reduced mRNA abundance of hypoxia-associated genes in MAC-T cells

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Sodium salicylate decreased abundance of transcripts involved in mammary development.

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Knockdown of HIF-1α did not prevent hypoxia-induced glucose transporter 1 expression.

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Few interactions between hypoxia and sodium salicylate were observed.

Hypoxia is an oxygen deficiency commonly found in growing tissues and is speculated to occur in the rapidly developing mammary gland in peripartum dairy cattle. Low oxygen concentrations can activate hypoxia-inducible factor-1 (HIF-1), which increases transcription of genes involved in angiogenesis (VEGFA) and glucose transport (GLUT1), among other processes. The mRNA stability of these genes is positively regulated by heterogeneous nuclear ribonucleoprotein D (HNRNPD; also known as AUF1). In our previous research, postpartum administration of sodium salicylate (SS) increased whole-lactation milk yield in multiparous cows but tended to reduce milk yield in primiparous cows. Because rapid mammary tissue development likely occurs in cows approaching first lactation, we hypothesized that SS inhibited the activation of HIF-1α and decreased transcription of downstream targets. MAC-T cells were treated with SS (100 μM) or control medium before incubation under either hypoxic (1% O₂) or normoxic conditions for 12 h. Additionally, cells were transfected with either HIF1A small interfering RNA (siRNA) or a scrambled siRNA negative control 48 h before hypoxia treatments. HIF1A, GLUT1, VEGFA, and HNRNPD were quantified relative to the internal control gene NENF. Transcript abundance was assessed using a linear mixed model with the fixed effects of SS, hypoxia, siRNA, and all 2- and 3-way interaction terms and the random effect of plate nested within hypoxia. Treatment with SS interacted with hypoxia for GLUT1, as SS reduced GLUT1 when MAC-T cells were cultured in normoxic conditions; however, no effect of SS was found in hypoxia-treated cells. Regardless of oxygen status, SS reduced HNRNPD and tended to decrease VEGFA mRNA relative to untreated cells. Hypoxia increased GLUT1, yet no effect was observed on VEGFA or HNRNPD. Small interfering RNA knocked down HIF1A, but no effect was found on GLUT1, VEGFA, or HNRNPD. In conclusion, SS reduced transcript abundance of genes involved with mammary gland development but generally did not interact with oxygen status.

Effects of Dietary L-Carnitine Supplementation on Platelets and Erythrogram of Dairy Cows with Special Emphasis on Parturition

During late gestation and early lactation, many proliferative processes and metabolic adaptions are involved in homeorhesis. An adjusted supply of oxygen is a precondition for an optimized cellular energy metabolism whereby erythrocytes play a central role. Endogenous L-carnitine modulates the mitochondrial fatty acid utilization for generating adenosine triphosphate (ATP). As it might be insufficient around calving due to increased need, L-carnitine supplementation is frequently recommended. Thus, the present study addressed the interplay between the red hemogram, platelets, oxidative stress indices, and L-carnitine supplementation of dairy cows around calving. German Holstein cows were assigned to a control (n = 30) and an L-carnitine group (n = 29, 25 g of rumen-protected L-carnitine per cow and per day), and blood samples were taken from day 42 ante partum (ap) until day 110 postpartum (pp), with a higher sampling frequency during the first three days pp. The time courses of the erythrogram parameters reflected the physiological adaptations to the oxygen need without being influenced by L-carnitine supplementation. Erythrocytic antioxidative enzymatic defence paralleled the relative development of polycythemia ap, while non-enzymatic total plasma antioxidative capacity continuously increased pp. In contrast to erythrocytes, the platelet counts of the L-carnitine supplemented cows varied at significantly higher levels. This can be interpreted as a result of a membrane-stabilizing effect of L-carnitine.

Comprehensive MicroRNA Expression Profile of the Mammary Gland in Lactating Dairy Cows With Extremely Different Milk Protein and Fat Percentages

A total of 31 differentially expressed genes in the mammary glands were identified in our previous study using RNA sequencing (RNA-Seq), for lactating cows with extremely high and low milk protein and fat percentages. To determine the regulation of milk composition traits, we herein investigated the expression profiles of microRNA (miRNA) using small RNA sequencing based on the same samples as in the previous RNA-Seq experiment. A total of 497 known miRNAs (miRBase, release 22.1) and 49 novel miRNAs among the reads were identified. Among these miRNAs, 71 were found differentially expressed between the high and low groups (p < 0.05, q < 0.05). Furthermore, 21 of the differentially expressed genes reported in our previous RNA-Seq study were predicted as target genes for some of the 71 miRNAs. Gene ontology and KEGG pathway analyses showed that these targets were enriched for functions such as metabolism of protein and fat, and development of mammary gland, which indicating the critical role of these miRNAs in regulating the formation of milk protein and fat. With dual luciferase report assay, we further validated the regulatory role of 7 differentially expressed miRNAs through interaction with the specific sequences in 3'UTR of the targets. In conclusion, the current study investigated the complexity of the mammary gland transcriptome in dairy cattle using small RNA-seq. Comprehensive analysis of differential miRNAs expression and the data from previous study RNA-seq provided the opportunity to identify the key candidate genes for milk composition traits.

Supplemental effects of dietary lysophospholipids in lactation diets on sow performance, milk composition, gut health, and gut-associated microbiome of offspring

Dietary lysophospholipids (LPL) would influence milk composition of sows, thus positively affect intestinal health of offspring. The objective of this study was to determine effects of dietary LPL fed to lactating sows on performance, milk characteristics, gut health, and gut-associated microbiome of offspring. Sixty pregnant sows were allotted to 2 treatments in a randomized complete block design with parity and BW as blocks on day 110 of gestation. Treatments were CON (no added LPL) and LPL (0.05% LPL; Lipidol-Ultra, Pathway Intermediates, Shrewsbury, UK). Sows were fed 2 kg/d from day 110 of gestation until farrowing and ad libitum after farrowing. Diets were formulated to meet NRC requirement for lactating sows. Colostrum and milk samples from 12 sows per treatment were collected to measure nutrients and immunoglobulins on days 1 and 18 of lactation, respectively. Twelve piglets per treatment (1 piglet per litter) were euthanized on day 18 to collect tissues to measure tumor necrosis factor-α, interleukin-8 (IL-8), malondialdehyde, protein carbonyl, IgA, histomorphology, crypt cell proliferation rate, and microbiota in the jejunum and colon. Data were analyzed using the MIXED procedure of SAS, and the mortality was analyzed using the GLIMMIX procedure of SAS. There was no difference in sow BW, parity, and litter size between treatments on day 0 of lactation. Sows fed LPL had increased (P < 0.05) litter BW gain (53.9 vs. 59.4 kg) and decreased piglet mortality (13.9% vs. 10.6%) on day 18 of lactation. Sows fed LPL had increased (P < 0.05) omega-6:omega-3 (22.1 vs. 23.7) and unsaturated:saturated (1.4 vs. 1.6) fatty acids ratios with increased oleic acid (29.1% vs. 31.4%) and tended to have increased (P = 0.092) IgG (1.14 vs. 1.94 g/L) and linoleic acid (17.7% vs. 18.7%) in the milk on day 18 of lactation. Piglets from sows fed LPL had increased (P < 0.05) IL-8 (184 vs. 245 pg/mg) and crypt cell proliferation rate (39.4% vs. 40.9%) and tended to have increased (P = 0.095) Firmicutes:Bacteroidetes ratio (1.0 vs. 3.5) in the jejunum. In conclusion, sows fed with LPL had milk with increased IgG, oleic acids, and linoleic acids without changes in BW and backfat during lactation. These changes could contribute to improved survivability and intestinal health of piglets by increasing IL-8 concentration, enhancing balance among gut-associated microbiome, and increasing enterocyte proliferation in the jejunum.

Oxygen carrier in core-shell fibers synthesized by coaxial electrospinning enhances Schwann cell survival and nerve regeneration

Rationale: Local hypoxia is a challenge for fabrication of cellular grafts and treatment of peripheral nerve injury. In our previous studies, we demonstrated that perfluorotributylamine (PFTBA) could provide short term oxygen supply to Schwann cells (SCs) and counteract the detrimental effects of hypoxia on SCs during the early stages of nerve injury. However, the quick release of oxygen in PFTBA compromised its ability to counteract hypoxia over an extended time, limiting its performance in peripheral nerve injury.

Methods: In this study, PFTBA-based oxygen carrier systems were prepared through coaxial electrospinning to prolong the time course of oxygen release. Core-shell structures were fabricated, optimized, and the oxygen kinetics of PFTBA-enriched core-shell fibers evaluated. The effect of core-shells on the survival and function of SCs was examined in both 2D and 3D systems as well as in vivo. The system was used to bridge large sciatic nerve defects in rats.

Results: PFTBA core-shell fibers provided high levels of oxygen to SCs in vitro, enhancing their survival, and increasing NGF, BDNF, and VEGF expression in 2D and 3D culture systems under hypoxic condition. In vivo analysis showed that the majority of GFP-expressing SCs in the PFTBA conduit remained viable 14 days post-implantation. We found that axons in PFTBA oxygen carrier scaffold improved axonal regeneration, remyelination, and recovery.

Conclusion: A synthetic oxygen carrier in core-shell fibers was fabricated by the coaxial electrospinning technique and was capable of enhancing SC survival and nerve regeneration by prolonged oxygen supply. These findings provide a new strategy for fabricating cellular scaffolds to achieve regeneration in peripheral nerve injury treatment and other aerobic tissue injuries.

Effect of short-term ischemia on microcirculation and wound healing of adipocutaneous flaps in the rat

PURPOSE

Composite flaps used in reconstructive surgery may intra- and postoperatively suffer from hypoperfusion and/or ischemia-reperfusion influencing wound healing. We aimed to follow-up the effect of ischemia on adipocutaneous flaps' wound healing and microcirculation.

METHODS

In anesthetized rats groin flaps were formed bilaterally. In Control group the flaps were repositioned and sutured back. In Ischemia-Reperfusion (I/R) group before repositioning and suturing the flap pedicles were clamped for 60 minutes. Laser Doppler (LD) fluxmetry and temperature probes were applied on the cranial, central and caudal flap regions before/after preparation and ischemia, re-suturing, and on the 1st-3rd-5th-7th-14th postoperative days, before the final examinations and biopsies for histology.

RESULTS

Flaps' skin temperature quickly recovered after repositioning. LD values were lower in the I/R group, reaching a significant level by the 3rd postoperative day, and remained lowered till the 14th day. The magnitude of alterations differed in the flap regions. Histologically normal wound healing process was seen, except for some I/R flaps, where hypertrophized mammary glands were found.

CONCLUSIONS

Short-term ischemia could influence flap microcirculation and wound healing, and may result in hypertrophized mammary glands. Laser Doppler could be used to evaluate intra- and postoperative microcirculatory changes and may have significance in predicting complications.

Effects of Hyperbaric Oxygen on T helper 17/regulatory T Polarization in Antigen and Collagen-induced Arthritis: Hypoxia-inducible Factor-1α as a Target

Objectives

We sought to investigate and prove the effect of hyperbaric oxygen therapy (HBOT) on T helper 17 (Th17)/regulatory T (Treg) cell polarization through changes in the expression of hypoxia-inducible factor-1 alpha (HIF-1α) in rheumatoid arthritis (RA) animal model.

Methods

We used antigen and collagen-induced arthritis (ACIA) as a RA animal model. Sixteen male BALB/c models of ACIA mice were divided into two groups, the non-HBOT group as the control group and the HBOT group as the treatment group. Expression of HIF-1α, Th17 anti-cluster differentiation 196 (CD196), and Treg anti-interleukine 2 receptor β-chain cells (IL-2Rβ) in tissue from the left knee joint tissue were determined histologically. Oxidative stress and systemic inflammation were assessed by levels of superoxide dismutase (SOD), interleukin 17a (IL-17a), C-reactive protein (CRP), and rheumatoid factor (RF) using the enzyme-linked immune-sorbent assay. The degree of arthritis was assessed by clinical scoring of paw swelling and the diameter of paw swelling.

Results

We found a significant decrease (p < 0.050) in the expression of HIF-1α, Th17 (CD196), IL-17a, RF levels, and the clinical scores and the diameter of paw swelling when comparing both groups. There was no significant decrease in the level of CRP in the treatment group compared to the control group. The expression of Treg (IL-2Rβ) increased significantly (p < 0.050) and the level of SOD increased but not significantly (p > 0.050) in the treatment group compared to the control group.

Conclusions

HBOT has effects on the polarization of Th17 to Treg through a decrease in expression of HIF-1α in mice with ACIA. HBOT is recommended for use as a support therapy for RA in combination with drug therapy.

Oxygen Regulation in Development: Lessons from Embryogenesis towards Tissue Engineering

Oxygen is a vital source of energy necessary to sustain and complete embryonic development. Not only is oxygen the driving force for many cellular functions and metabolism, but it is also involved in regulating stem cell fate, morphogenesis, and organogenesis. Low oxygen levels are the naturally preferred microenvironment for most processes during early development and mainly drive proliferation. Later on, more oxygen and also nutrients are needed for organogenesis and morphogenesis. Therefore, it is critical to maintain oxygen levels within a narrow range as required during development. Modulating oxygen tensions is performed via oxygen homeostasis mainly through the function of hypoxia-inducible factors. Through the function of these factors, oxygen levels are sensed and regulated in different tissues, starting from their embryonic state to adult development. To be able to mimic this process in a tissue engineering setting, it is important to understand the role and levels of oxygen in each developmental stage, from embryonic stem cell differentiation to organogenesis and morphogenesis. Taking lessons from native tissue microenvironments, researchers have explored approaches to control oxygen tensions such as hemoglobin-based, perfluorocarbon-based, and oxygen-generating biomaterials, within synthetic tissue engineering scaffolds and organoids, with the aim of overcoming insufficient or nonuniform oxygen levels and nutrient supply.

Prolactin selectively transported to cerebrospinal fluid from blood under hypoxic/ischemic conditions

Aim

The aim of this study was to determine and to verify the correlation between the amount of prolactin (PRL) levels in the blood and in the cerebrospinal fluid (CSF) by various causes of death as an indicator for acute hypoxia in autopsy cases. It is to confirm the cause of the change in prolactin level in CSF by in vitro system.

Materials and methods

In autopsy materials, the PRL levels in blood from the right heart ventricle and in the CSF were measured by chemiluminescent enzyme immunoassay, and changes in the percentage of PRL-positive cells in the pituitary gland were examined using an immunohistochemical method. Furthermore, an inverted culture method was used as an in vitro model of the blood-CSF barrier using epithelial cells of the human choroid plexus (HIBCPP cell line) and SDR-P-1D5 or MSH-P3 (PRL-secreting cell line derived from miniature swine hypophysis) under normoxic or hypoxic (5% oxygen) conditions, and as an index of cell activity, we used Vascular Endothelial Growth Factor (VEGF).

Results and discussion

Serum PRL levels were not significantly different between hypoxia/ischemia cases and other causes of death. However, PRL levels in CSF were three times higher in cases of hypoxia/ischemia than in those of the other causes of death. In the cultured cell under the hypoxia condition, PRL and VEGF showed a high concentration at 10 min. We established a brain-CSF barrier model to clarify the mechanism of PRL transport to CSF from blood, the PRL concentrations from blood to CSF increased under hypoxic conditions from 5 min. These results suggested that PRL moves in CSF through choroidal epithelium from blood within a short time. PRL is hypothesized to protect the hypoxic/ischemic brain, and this may be because of the increased transportation of the choroid plexus epithelial cells.

Distinct breast cancer stem/progenitor cell populations require either HIF1α or loss of PHD3 to expand under hypoxic conditions

The heterogeneous nature of breast cancer is a result of intrinsic tumor complexity and also of the tumor microenvironment, which is known to be hypoxic. We found that hypoxia expands different breast stem/progenitor cell populations (cells with increased aldehyde dehydrogenase activity (Aldefluor⁺), high mammosphere formation capacity and CD44⁺CD24^−/low cells) both in primary normal epithelial and tumor cells. The presence of the estrogen receptor (ER) limits hypoxia-dependent CD44⁺CD24^−/low cell expansion. We further show that the hypoxia-driven cancer stem-like cell enrichment results from a dedifferentiation process. The enhanced mammosphere formation and Aldefluor⁺ cell content observed in breast cancer cells relies on hypoxia-inducible factor 1α (HIF1α). In contrast, the CD44⁺CD24^−/low population expansion is HIF1α independent and requires prolyl hydroxylase 3 (PHD3) downregulation, which mimics hypoxic conditions, leading to reduced CD24 expression through activation of NFkB signaling. These studies show that hypoxic conditions expand CSC populations through distinct molecular mechanisms. Thus, potential therapies that combine current treatments for breast cancer with drugs that target CSC should take into account the heterogeneity of the CSC subpopulations.

Hypoxia promotes the proliferation of MC3T3-E1 cells via the hypoxia-inducible factor-1α signaling pathway

Investigations into the role of hypoxia have concentrated on hypoxic damage to cells and the associated adaptative mechanisms, however, the effects of hypoxia on cell proliferation and differentiation have received less attention. The present study aimed to investigate the role of hypoxia on the proliferation of MC3T3‑E1 cells and examine the molecular mechanism involved. Cells treated with low levels of hypoxia had an increased percentage of S phase cells and a decreased percentage of G1 phase cells, promoted the level of cell proliferation‑associated proteins, proliferating cell nuclear antigen and cyclin D. In addition, hypoxia increased cell proliferation by upregulating the expression of hypoxia‑inducible factor (HIF)‑1α. The phosphoinositide 3‑kinase/Akt and mitogen‑activated protein kinase/extracellular signal‑regulated kinase pathways augmented the expression of HIF‑1α in the MC3T3‑E1 cells. The present study demonstrated that hypoxia induces positive effects on osteoblast proliferation, suggesting a novel strategy in the treatment of osteoporosis.

The effect of long term under- and over-feeding on the expression of genes related to glucose metabolism in mammary tissue of sheep

Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, the effect of long term under- and over-feeding on the expression of genes [glucose transporter 1: GLUT1, glucose transporter 3: GLUT3, Sodium glucose contransporter 1: SGLT1, two isoforms of β- (1,4) galactosyltransferase: β- (1,4) GAT1, β- (1,4) GAT3 and α-lactalbumin: LALBA] related to glucose metabolism in sheep mammary tissue (MT) was examined. Twenty-four lactating dairy sheep were divided into three homogenous sub-groups and fed the same ration in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant reduction on mRNA of GLUT1 and LALBA gene in the MT of underfed sheep, compared with the respective controls and overfed and a significant reduction on mRNA level of SGLT1 and β- (1,4) GAT1 in the MT of underfed sheep, compared with the overfed ones. A significant increase in the GLUT3 mRNA accumulation in the MT of both under- and over- fed sheep was found. Additionally, a trend of reduction on β- (1,4) GAT3 mRNA level in the MT of the underfed sheep, compared with the overfed, was observed. A close positive relationship was obtained between the mRNA transcripts accumulation of GLUT1, SGLT1, β- (1,4) GAT1 and LALBA gene with the milk lactose content and milk lactose yield respectively. In conclusion, feeding level and consequently nutrient availability, may affect glucose uptake and utilisation in sheep MT by altering the GLUT1, GLUT3, SGLT1, β- (1,4) GAT1 and LALBA gene expression involved in their metabolic pathways.

Developmental programming: the role of growth hormone

Developmental programming of the fetus has consequences for physiologic responses in the offspring as an adult and, more recently, is implicated in the expression of altered phenotypes of future generations. Some phenotypes, such as fertility, bone strength, and adiposity are highly relevant to food animal production and in utero factors that impinge on those traits are vital to understand. A key systemic regulatory hormone is growth hormone (GH), which has a developmental role in virtually all tissues and organs. This review catalogs the impact of GH on tissue programming and how perturbations early in development influence GH function.

Differential regulation of GLUT1 and GLUT8 expression by hypoxia in mammary epithelial cells

Glucose is a major substrate for milk synthesis and is taken up from the blood by mammary epithelial cells (MECs) through facilitative glucose transporters (GLUTs). The expression levels of GLUT1 and GLUT8 are upregulated dramatically in the mammary gland from late pregnancy through early lactation stages. This study aimed to test the hypothesis that this increase in GLUT1 and GLUT8 expression involves hypoxia signaling through hypoxia inducible factor-1α (HIF-1α) in MECs. Mouse mammary glands showed significantly more hypoxia in midpregnancy through early lactation stages compared with in the virgin stage, as stained by the hypoxia marker pimonidazole HCl. Treatment with hypoxia (2% O2) significantly stimulated glucose uptake and GLUT1 mRNA and protein expression, but decreased GLUT8 mRNA expression in bovine MECs. In MECs, hypoxia also increased the levels of HIF-1α protein in the nuclei, and siRNA against HIF-1α completely abolished the hypoxia-induced upregulation of GLUT1, while having no effect on GLUT8 expression. A 5'-RCGTG-3' core HIF-1α binding sequence was identified 3.7 kb upstream of the bovine GLUT1 gene, and HIF-1α binding to this site was increased during hypoxia. In conclusion, the mammary glands in pregnant and lactating animals are hypoxic, and MECs respond to this hypoxia by increasing GLUT1 expression and glucose uptake through a HIF-1α-dependent mechanism. GLUT8 expression, however, is negatively regulated by hypoxia through a HIF-1α-independent pathway. The regulation of glucose transporters through hypoxia-mediated gene transcription in the mammary gland may provide an important physiological mechanism for MECs to meet the metabolic demands of mammary development and lactation.

Biology of glucose transport in the mammary gland

Glucose is the major precursor of lactose, which is synthesized in Golgi vesicles of mammary secretory alveolar epithelial cells during lactation. Glucose is taken up by mammary epithelial cells through a passive, facilitative process, which is driven by the downward glucose concentration gradient across the plasma membrane. This process is mediated by facilitative glucose transporters (GLUTs), of which there are 14 known isoforms. Mammary glands mainly express GLUT1 and GLUT8, and GLUT1 is the predominant isoform with a Km of ~10 mM and transport activity for mannose and galactose in addition to glucose. Mammary glucose transport activity increases dramatically from the virgin state to the lactation state, with a concomitant increase in GLUT expression. The increased GLUT expression during lactogenesis is not stimulated by the accepted lactogenic hormones. New evidence indicates that a possible low oxygen tension resulting from increased metabolic rate and oxygen consumption may play a major role in stimulating glucose uptake and GLUT1 expression in mammary epithelial cells during lactogenesis. In addition to its primary presence on the plasma membrane, GLUT1 is also expressed on the Golgi membrane of mammary epithelial cells and is likely involved in facilitating the uptake of glucose and galactose to the site of lactose synthesis. Because lactose synthesis dictates milk volume, regulation of GLUT expression and trafficking represents potentially fruitful areas for further research in dairy production. In addition, this research will have pathological implications for the treatment of breast cancer because glucose uptake and GLUT expression are up-regulated in breast cancer cells to accommodate the increased glucose need.