Low Oxygen Tension Research Articles

INTERLEUKIN-1B (IL-1B)-INHIBITED MENISCUS DEPOSITION IS COUNTERED BY CULTURE UNDER PHYSIOXIA TO A GREATER EXTENT COMPARED WITH CELECOXIB-TREATED MENISCUS CELLS

Meniscus tears have been treated using partial meniscectomy to relieve pain in patients, although this leads to the onset of early osteoarthritis (OA). Cell-based therapies can help preserve the meniscus, although the presence of inflammatory cytokines compromises clinical outcomes. Anti-inflammatory drugs (e.g. celecoxib), can help to reduce pain in patients and in vitro studies suggest a beneficial effect on cytokine inhibited matrix content. Previously, we have demonstrated that the inhibitory effects of IL-1β can be countered by culture under low oxygen tension or physioxia. The present study sought to understand whether physioxia, celecoxib or combined application can counter the inhibitory effects IL-1β inhibited meniscus cells.Human avascular and vascular meniscus cells (n =3) were isolated and expanded under 20% (hyperoxia) or 2% (physioxia) oxygen. Cells were seeded into collagen scaffolds (Geistlich, Wolhusen) and cultured for 28 days either in the presence of 0.1ng/mL IL-1β, 5µg/mL celecoxib or both under their expansion oxygen conditions. Histological (DMMB, collagen I and collagen II immunostaining), GAG content and gene expression analysis was evaluated for the scaffolds.Under hyperoxia, meniscus cells showed a significant reduction in GAG content in the presence of IL-1β (*p < 0.05). Celecoxib alone did not significantly increase GAG content in IL-1β treated cultures. In contrast, physioxic culture showed a donor dependent increase in GAG content in control, IL-1β and celecoxib treated cultures with corresponding histological staining correlating with these results. Additionally, gene expression showed an upregulation in COL1A1, COL2A1 and ACAN and a downregulation in MMP13 and ADAMTS5 under physioxia for all experimental groups.Physioxia alone had a stronger effect in countering the inhibitory effects of IL-1β treated meniscus cells than celecoxib under hyperoxia. Preconditioning meniscus cells under physioxia prior to implantation has the potential to improve clinical outcomes for cell-based therapies of the meniscus.

Evaluation of hypoxia tolerance in F3 hybrids of blunt snout bream (Megalobrama amblycephala♀) × topmouth culter (Culter alburnus♂)

To compare gill hypoxia adaptation mechanisms, the hypoxia-related physiological indices were measured in F3 self-crossing population of blunt snout bream (Megalobrama amblycephala)♀ × topmouth culter (Culter alburnus)♂ hybrids. The critical oxygen pressure (Pcrit) of F3 population was 28.33 ± 1.58 Torr, which is higher than topmouth culter (21.69 ± 0.85 Torr) and lower than blunt snout bream (33.00 ± 0.97 Torr). Moreover, the lower oxygen tension threshold for loss of equilibrium (LOEcrit) of F3 hybrids was 1.09 mg·L−1 higher than topmouth culter (0.91 mg·L−1) and lower than blunt snout bream (1.30 mg·L−1). These results indicated that the hypoxia tolerance of F3 hybrid fish was significantly higher than that of blunt snout bream. In the hypoxic environment, gill remodeling reactions increased the mass-specific lamellar area. In this study, gill remodeling was observed in blunt snout bream, topmouth culter and F3 hybrids. However, a particularly intriguing finding was that the gill recovery ability of F3 population was better than that of blunt snout bream after reoxygenation treatment. This might be related to the capability of physiological and biochemical regulation and lactic acid excretion of F3 hybrids. Together, these results showed that the F3 population inherited the gill remodeling mechanism of their parents, which had better hypoxia tolerance than blunt snout bream, and they could change the morphology and physiological and biochemical levels of gill tissue to cope with hypoxia.

Long-term proliferation of immature hypoxia-dependent JMML cells supported by a 3D invitro system.

Juvenile myelomonocytic leukemia (JMML) is a rare clonal stem cell disorder that occurs in early childhood and is characterized by the hyperactivation of the RAS pathway in 95% of the patients. JMML is characterized by a hyperproliferation of granulocytes and monocytes, and little is known about the heterogeneous nature of leukemia-initiating cells, as well as of the cellular hierarchy of the JMML bone marrow. In this study, we report the generation and characterization of a novel patient-derived three-dimensional (3D) invitro JMML model, called patient-derived JMML Atypical Organoid (pd-JAO), sustaining the long-term proliferation of JMML cells with stem cell features and patient-specific hallmarks. JMML cells brewed in a 3D model under different microenvironmental conditions acquired proliferative and survival advantages when placed under low oxygen tension. Transcriptomic and microscopic analyses revealed the activation of specific metabolic energy pathways and the inactivation of processes leading to cell death. Furthermore, we demonstrated the pd-JAO-derived cells' migratory, propagation, and self-renewal capacities. Our study contributes to the development of a robust JMML 3D invitro model for studying and defining the impact of microenvironmental stimuli on JMML disease and the molecular mechanisms that regulate JMML initiating and propagating cells. Pd-JAO may become a promising model for compound tests focusing on new therapeutic interventions aimed at eradicating JMML progenitors and controlling JMML disease.

In vitro spermatogenesis in isolated seminiferous tubules of immature mice.

Mouse spermatogenesis, from spermatogonial stem cell proliferation to sperm formation, can be reproduced in vitro by culturing testis tissue masses of neonatal mice. However, it remains to be determined whether this method is also applicable when testis tissues are further divided into tiny fragments, such as segments of the seminiferous tubule (ST), a minimal anatomical unit for spermatogenesis. In this study, we investigated this issue using the testis of an Acrosin-GFP/Histone H3.3-mCherry (Acr/H3) double-transgenic mouse and monitored the expression of GFP and mCherry as indicators of spermatogenic progression. Initially, we noticed that the cut and isolated stretches of ST shrunk rapidly and conglomerated. We therefore maintained the isolation of STs in two ways: segmental isolation without truncation or embedding in soft agarose. In both cases, GFP expression was observed by fluorescence microscopy. By whole-mount immunochemical staining, meiotic spermatocytes and round and elongating spermatids were identified as Sycp3-, crescent-form GFP-, and mCherry-positive cells, respectively. Although the efficiency was significantly lower than that with tissue mass culture, we clearly showed that spermatogenesis can be induced up to the elongating spermatid stage even when the STs were cut into short segments and cultured in isolation. In addition, we demonstrated that lowered oxygen tension was favorable for spermatogenesis both for meiotic progression and for producing elongating spermatids in isolated STs. Culturing isolated STs rather than tissue masses is advantageous for explicitly assessing the various environmental parameters that influence the progression of spermatogenesis.

Functional exploration of SNP mutations in HIF2αb gene correlated with hypoxia tolerance in blunt snout bream (Megalobrama amblycephala).

Blunt snout bream (Megalobrama amblycephala) is sensitive to hypoxia environment. Hypoxia-inducible factor (HIF) is the most critical factor in the HIF pathway, which strictly regulates the hypoxia stress process of fish. In this study, we found six hifα genes in blunt snout bream that demonstrated different expressions under hypoxia conditions. In HEK293T cells, all six hifαs were detected to activate the HRE region by luciferase reporter assay. More importantly, we identified two linkage-disequilibrium SNP sites at exon 203 and 752 of the hif2αb gene in blunt snout bream. Haplotype II (A203A752) and its homozygous diplotype II (A203A203A752A752) appeared frequently in a selected strain of blunt snout bream with hypoxia tolerance. Diplotype II has a lower oxygen tension threshold for loss of equilibrium (LOEcrit) over a similar range of temperatures. Moreover, its erythrocyte number increased significantly (p < 0.05) than those in diplotype I and diplotype III strains at 48h of hypoxia. The enzymes related with hypoxia tolerant traits, i.e., reduced glutathione, superoxide dismutase, and catalase, were also significantly (p < 0.05) induced in diplotype II than in diplotype I or III. In addition, the expression of epo in the liver of diplotype II was significantly (p < 0.01) higher than that in the diplotype I or III strains at 48h of hypoxia. Taken together, our results found that the hypoxia-tolerant-related diplotype II of hif2αb has the potential to be used as a molecular marker in future genetic breeding of hypoxia-tolerant strain.

Oxygen-generating microparticles downregulate HIF-1α expression, increase cardiac contractility, and mitigate ischemic injury.

Myocardial hypoxia is the low oxygen tension in the heart tissue implicated in many diseases, including ischemia, cardiac dysfunction, or after heart procurement for transplantation. Oxygen-generating microparticles have recently emerged as a potential strategy for supplying oxygen to sustain cell survival, growth, and tissue functionality in hypoxia. Here, we prepared oxygen-generating microparticles with poly D,L-lactic-co-glycolic acid, and calcium peroxide (CPO), which yielded a continuous morphology capable of sustained oxygen release for up to 24h. We demonstrated that CPO microparticles increased primary rat cardiomyocyte metabolic activity while not affecting cell viability during hypoxia. Moreover, hypoxia-inducible factor (HIF)-1α, which is upregulated during hypoxia, can be downregulated by delivering oxygen using CPO microparticles. Single-cell traction force microscopy data demonstrated that the reduced energy generated by hypoxic cells could be restored using CPO microparticles. We engineered cardiac tissues that showed higher contractility in the presence of CPO microparticles compared to hypoxic cells. Finally, we observed reduced myocardial injuries in ex vivo rabbit hearts treated with CPO microparticles. In contrast, an acute early myocardial injury was observed for the hearts treated with control saline solution in hypoxia. In conclusion, CPO microparticles improved cell and tissue contractility and gene expression while reducing hypoxia-induced myocardial injuries in the heart. STATEMENT OF SIGNIFICANCE: Oxygen-releasing microparticles can reduce myocardial ischemia, allograft rejection, or irregular heartbeats after heart transplantation. Here we present biodegradable oxygen-releasing microparticles that are capable of sustained oxygen release for more than 24 hrs. We then studied the impact of sustained oxygen release from microparticles on gene expresseion and cardiac cell and tissue function. Previous studies have not measured cardiac tissue or cell mechanics during hypoxia, which is important for understanding proper cardiac function and beating. Using traction force microscopy and an engineered tissue-on-a-chip, we demonstrated that our oxygen-releasing microparticles improve cell and tissue contractility during hypoxia while downregulating the HIF-1α expression level. Finally, using the microparticles, we showed reduced myocardial injuries in rabbit heart tissue, confirming the potential of the particles to be used for organ transplantation or tissue engineering.

MiR-210 Expression Is Strongly Hypoxia-Induced in Anaplastic Thyroid Cancer Cell Lines and Is Associated with Extracellular Vesicles and Argonaute-2.

Hypoxia, or low oxygen tension, is frequently found in highly proliferative solid tumors such as anaplastic thyroid carcinoma (ATC) and is believed to promote resistance to chemotherapy and radiation. Identifying hypoxic cells for targeted therapy may thus be an effective approach to treating aggressive cancers. Here, we explore the potential of the well-known hypoxia-responsive microRNA (miRNA) miR-210-3p as a cellular and extracellular biological marker of hypoxia. We compare miRNA expression across several ATC and papillary thyroid cancer (PTC) cell lines. In the ATC cell line SW1736, miR-210-3p expression levels indicate hypoxia during exposure to low oxygen conditions (2% O2). Furthermore, when released by SW1736 cells into the extracellular space, miR-210-3p is associated with RNA carriers such as extracellular vesicles (EVs) and Argonaute-2 (AGO2), making it a potential extracellular marker for hypoxia.

Tissue-Oxygen-Adaptation of Bone Marrow-Derived Mesenchymal Stromal Cells Enhances Their Immunomodulatory and Pro-Angiogenic Capacity, Resulting in Accelerated Healing of Chemical Burns.

Transplantation of mesenchymal stromal cells (MSCs) provides a powerful tool for the management of multiple tissue injuries. However, poor survival of exogenous cells at the site of injury is a major complication that impairs MSC therapeutic efficacy. It has been found that tissue-oxygen adaptation or hypoxic pre-conditioning of MSCs could improve the healing process. Here, we investigated the effect of low oxygen tension on the regenerative potential of bone-marrow MSCs. It turned out that incubation of MSCs under a 5% oxygen atmosphere resulted in increased proliferative activity and enhanced expression of multiple cytokines and growth factors. Conditioned growth medium from low-oxygen-adapted MSCs modulated the pro-inflammatory activity of LPS-activated macrophages and stimulated tube formation by endotheliocytes to a much higher extent than conditioned medium from MSCs cultured in a 21% oxygen atmosphere. Moreover, we examined the regenerative potential of tissue-oxygen-adapted and normoxic MSCs in an alkali-burn injury model on mice. It has been revealed that tissue-oxygen adaptation of MSCs accelerated wound re-epithelialization and improved the tissue histology of the healed wounds in comparison with normoxic MSC-treated and non-treated wounds. Overall, this study suggests that MSC adaptation to 'physiological hypoxia' could be a promising approach for facilitating skin injuries, including chemical burns.

The Underexplored Landscape of Hypoxia-Inducible Factor 2 Alpha and Potential Roles in Tumor Macrophages: A Review.

Low tissue oxygenation, termed hypoxia, is a characteristic of solid tumors with negative consequences. Tumor-associated macrophages (TAMs) accumulate in hypoxic tumor regions and correlate with worse outcomes in cancer patients across several tumor types. Thus, the molecular mechanism in which macrophages respond to low oxygen tension has been increasingly investigated in the last decade. Hypoxia stabilizes a group of hypoxia-inducible transcription factors (HIFs) reported to drive transcriptional programs involved in cell survival, metabolism, and angiogenesis. Though both tumor macrophage HIF-1α and HIF-2α correlate with unfavorable tumor microenvironments, most research focuses on HIF-1α as the master regulator of hypoxia signaling, because HIF-1α expression was originally identified in several cancer types and correlates with worse outcome in cancer patients. The relative contribution of each HIFα subunit to cell phenotypes is poorly understood especially in TAMs. Once thought to have overlapping roles, recent investigation of macrophage HIF-2α has demonstrated a diverse function from HIF-1α. Little work has been published on the differential role of hypoxia-dependent macrophage HIF-2α when compared to HIF-1α in the context of tumor biology. This review highlights cellular HIF-2α functions and emphasizes the gap in research investigating oxygen-dependent functions of tumor macrophage HIF-2α.

Initial care of sickle cell crises at the Prince of Wales Hospital from 2017–2022. A quality improvement study

Background: Sickle cell disease is a haemoglobinopathy caused by a single nucleotide substitution in the beta globin gene which leads to polymerisation and sickling at low oxygen tensions.1 The hallmark of the disease is intermittent, painful vaso-occlusive crises which often require presentation to the emergency department for management. Delay in effective management of sickle cell crises in the ED is common.2

COMMENSAL GUT BACTERIA REGULATE HIF ACTIVITY TO PROMOTE INTESTINAL HOMEOSTASIS

Abstract Inflammatory bowel disease (IBD) is a disorder marked by chronic, relapsing inflammation of the gastrointestinal tract. Although the precise etiology of IBD is unclear, pathogenic immune response to the gut microbiota is considered a contributing factor. The importance of the gut microbiota in the development of intestinal inflammation has been previously shown through associative studies that correlate dysbiosis of the gut microbiota with active IBD, particularly through the loss of fiber-fermenting obligate anaerobes, an increased presence of pathobionts, and an overall decrease in microbial species diversity. Although the gut microbiota clearly plays an essential role in the development and progression of IBD, the mechanisms by which these micro-organisms regulate gut homeostasis remain to be fully elucidated. Previously, we found that Salmonella Typhimurium (STm), a model invasive pathogen, activated hypoxia inducible factor-1α (HIF-1α) in intestinal epithelial cells (IECs) to regulate anti-bacterial autophagy. HIF-1α is a member of a transcription factor family that senses and responds to environmental stressors, in particular low oxygen tensions. Such stressors stabilize HIF-1α in the cytoplasm and prevent its usual oxygen-dependent degradation. Of note, HIF-1α has been previously shown to be essential for intestinal homeostasis in animal models of IBD, and stabilization of HIF has been demonstrated to be protective during various models of colitis in mice. As an extension of these studies, we asked whether bacterial stabilization of HIF was unique to STm in the intestinal epithelium. We found that stabilization of HIF in IECs was not restricted to STm but was, surprisingly, recapitulated by a wide variety of bacteria, including bacteria rendered non-invasive by genetic manipulation and nonpathogenic/commensal enteric bacterial isolates. Further, we observed that stabilization of HIF was dependent on live bacteria and not due to a secreted factor, suggesting an innate HIF response by the intestinal epithelium to enteric bacteria. Finally, we found modulation of HIF signaling by enteric bacteria including regulation of numerous genes previously implicated in gut homeostasis. These results, taken together, suggest that commensal bacteria regulate intestinal homeostasis through activation of the transcription factor HIF.

A microfluidic-based PDAC organoid system reveals the impact of hypoxia in response to treatment

Pancreatic Ductal Adenocarcinoma (PDAC) is estimated to become the second leading cause of cancer-related deaths by 2030 with mortality rates of up to 93%. Standard of care chemotherapeutic treatment only prolongs the survival of patients for a short timeframe. Therefore, it is important to understand events driving treatment failure in PDAC as well as identify potential more effective treatment opportunities. PDAC is characterized by a high-density stroma, high interstitial pressure and very low oxygen tension. The aim of this study was to establish a PDAC platform that supported the understanding of treatment response of PDAC organoids in mono-, and co-culture with pancreatic stellate cells (PSCs) under hypoxic and normoxic conditions. Cultures were exposed to Gemcitabine in combination with molecules targeting relevant molecular programs that could explain treatment specific responses under different oxygen pressure conditions. Two groups of treatment responses were identified, showing either a better effect in monoculture or co-culture. Moreover, treatment response also differed between normoxia and hypoxia. Modulation of response to Gemcitabine was also observed in presence of a Hypoxia-inducible factor (HIF) prolyl hydroxylase (PHD) inhibitor and HIF inhibitors. Altogether this highlights the importance of adjusting experimental conditions to include relevant oxygen levels in drug response studies in PDAC.

Low oxygen tension affects proliferation and senescence of caprine bone marrow mesenchymal stem cells in in vitro culture condition

The culture system of bone marrow mesenchymal stem cells (bmMSCs) in the normoxic environment does not imitate the hypoxic milieu of typical biological conditions, thus hypoxic culture conditions may improve survival, and growth attributes of bmMSCs during in vitro culture. Therefore, the present study was conducted at ICAR-CIRG, Makhdoom during year 2020 with the objective to investigate the changes in biological characteristics of cultured caprine bmMSCs (cbmMSCs) including the cellular senescence, survival, rate of proliferation, immuno-phenotypic characteristics, and gene expression pattern in a normal and hypoxic microenvironment condition. For this, cbmMSCs isolated from bone marrow collected from iliac crest were enriched and grown under either hypoxic (5% O2) or normoxic (20% O2) conditions. Thereafter, the outcome of hypoxic (5% O2) culturing of cbmMSCs on growth characteristics, proliferation, senescence, and expression profile of important stemness-associated (OCT-4) and oxidative stress [glutathione peroxidase (GPx1) and copper-zinc superoxide dismutase (CuZnSOD)] marker genes was evaluated. cbmMSCs cultivated in hypoxic conditions showed higher proliferation and decreased population doubling time and senescence-associated β-GAL expression; however, the immune-phenotypic characteristics of the cells remain unchanged. Furthermore, the culture of cbmMSCs in hypoxia increased the expression of OCT-4, GPx1, and CuZnSOD, compared with the cells grown under normoxia. In conclusion, the culture condition with low O2 level improved the growth characteristics and proliferation of cbmMSCs. These outcomes would provide information to formulate strategies for the collection and efficient in vitro expansion of bmMSCs from goats and other farm animals before their downstream applications.

Role of apoptotic inhibitors, viability, and differentiation in low oxygen tension of mesenchymal stem cells cultured in a rat model of ovarian failure.

Background: Stem cell therapy shows applications potential for malnutrition-induced ovarian failure in rat models. However, it is ineffective because of the lack of viability and differentiation of transplanted stem cells, resulting in low adaptation and survival rates. We aimed to determine whether stem cells cultured under low oxygen (O 2) tension improves the adaptability and viability of stem cells, as well as ovarian failure. Methods: After four days of culturing mesenchymal stem cells (MSCs) in 21% oxygen (normoxia) as the T2 group and 1% oxygen (low O 2 or hypoxia) as the T1 group, 200 million bone marrow-derived MSCs per rat were transplanted into female rats with ovarian failure (15 rats per treatment group). A total of 15 fertile and 15 infertile rats were categorized as the C+ and C- groups, respectively. Results: The slight increase in cells expressing HSP70 (C+, T2, T1, and C- groups were 0.5 a±0.53, 1.7 a±0.82, 6.2 b±1.5, and 9.6 c±1.3, respectively), decrease in cells expressing caspase-3 as an apoptotic inhibitor (C+, T2, T1, and C- groups were 0.2 a±0.42, 0.6 a±0.52, 4.8 b±1.03, and 7.3 c±1.42, respectively), and increase in cells expressing VEGF-1 (C+, T2, T1, and C- groups were 10.8 c±1.55, 8.7 b±0.48, 0.4 a±0.52, and 0.2 a±0.42, respectively) and GDF-9 (C+, T2, T1, and C- groups were 5.8 c±1.47, 4.6 b±0.97, 0.5 a±0.53, and 0.3 a±0.48, respectively) were used as markers for viability and differentiation in ovarian tissue, indicating that MSCs cultured under low O 2 tension were more effective than those cultured under normoxic conditions as a treatment for female rats with ovarian failure. Furthermore, infertile female rats treated with MSCs cultivated under low O 2 tension had an enhanced ovarian tissue shape, as indicated by the increasing Graafian follicle count (C+, T2, T1, and C- groups were 8.9 c±0.74, 4.5 b±0.71, 0.5 a±0.53, and 0.4 a±0.52, respectively). Conclusions: MSCs cultured under low O 2 tension are an effective treatment for malnourished rats with ovarian failure.

MTORC2 Is Activated under Hypoxia and Could Support Chronic Myeloid Leukemia Stem Cells.

Hypoxia is a critical condition that governs survival, self-renewal, quiescence, metabolic shift and refractoriness to leukemic stem cell (LSC) therapy. The present study aims to investigate the hypoxia-driven regulation of the mammalian Target of the Rapamycin-2 (mTORC2) complex to unravel it as a novel potential target in chronic myeloid leukemia (CML) therapeutic strategies. After inducing hypoxia in a CML cell line model, we investigated the activities of mTORC1 and mTORC2. Surprisingly, we detected a significant activation of mTORC2 at the expense of mTORC1, accompanied by the nuclear localization of the main substrate phospho-Akt (Ser473). Moreover, the Gene Ontology analysis of CML patients' CD34+ cells showed enrichment in the mTORC2 signature, further strengthening our data. The deregulation of mTOR complexes highlights how hypoxia could be crucial in CML development. In conclusion, we propose a mechanism by which CML cells residing under a low-oxygen tension, i.e., in the leukemia quiescent LSCs, singularly regulate the mTORC2 and its downstream effectors.

Nitric oxide promotes cell-matrix adhesion of endothelial progenitor cells under hypoxia condition via ITGA5 CpG promoter demethylation

Hypoxia or low oxygen tension causes changes in the structure and functional phenotype of the endothelial progenitor cells (EPCs). EPCs are found to be involved in angiogenesis and vascular repair. However, EPC's role in cell-matrix adhesion under hypoxia conditions is not clearly established. Nitric oxide (NO) exerts a wide range of biological functions, especially in regulating the mobilization and vascular repair of EPCs. In contrast, the link between NO and its role in cell-matrix deadhesion under hypoxia is not studied yet. Here, we investigated the protective role of NO in hypoxia-induced cell-matrix deadhesion of EPCs through an epigenetic mechanism. The EPCs were exposed to 2% hypoxia in the presence or absence of 10 μM Spermine NONOate (NO donor). The result demonstrates that hypoxia exposure intensified mitochondrial oxidative damage and energy defects. Using miScript miRNA qPCR array-based screening, the study found miR-148 as a novel target of hypoxia-induced DNMT1 activation. Mechanistically, the study discovered that hypoxia suppressed miR-148 levels and stimulated EPCs cell-matrix deadhesion via increasing DNMT1 mediated Integrin alpha-5 (ITGA5) CpG promoter hypermethylation. Treatment with a mitochondria-targeted antioxidant, MitoTEMPO, or epigenetic DNMT inhibitor, 5′-azacitidine, or miR-148 overexpression in hypoxic EPCs culture, prevented the cell-matrix deadhesion compared to hypoxic EPCs. Further, treatment of spNO or transient expression of eNOS-GFP attenuated hypoxia-induced cell-matrix deadhesion via inhibition of ITGA5 CpG island promoter methylation. In conclusion, the study provides evidence that NO is essential for cell-matrix adhesion of EPCs by epigenetically mitigating ITGA5 CpG promoter hypermethylation under hypoxia conditions. This finding uncovers the previously undefined mechanism of NO-mediated diminution of hypoxia-induced cell-matrix deadhesion and dysfunction induced by low oxygen tension.

Oxygen and the Spark of Human Brain Evolution: Complex Interactions of Metabolism and Cortical Expansion across Development and Evolution

Scientific theories on the functioning and dysfunction of the human brain require an understanding of its development—before and after birth and through maturation to adulthood—and its evolution. Here we bring together several accounts of human brain evolution by focusing on the central role of oxygen and brain metabolism. We argue that evolutionary expansion of human transmodal association cortices exceeded the capacity of oxygen delivery by the vascular system, which led these brain tissues to rely on nonoxidative glycolysis for additional energy supply. We draw a link between the resulting lower oxygen tension and its effect on cytoarchitecture, which we posit as a key driver of genetic developmental programs for the human brain—favoring lower intracortical myelination and the presence of biosynthetic materials for synapse turnover. Across biological and temporal scales, this protracted capacity for neural plasticity sets the conditions for cognitive flexibility and ongoing learning, supporting complex group dynamics and intergenerational learning that in turn enabled improved nutrition to fuel the metabolic costs of further cortical expansion. Our proposed model delineates explicit mechanistic links among metabolism, molecular and cellular brain heterogeneity, and behavior, which may lead toward a clearer understanding of brain development and its disorders.

MiR-210-3p Promotes Obesity-Induced Adipose Tissue Inflammation and Insulin Resistance by Targeting SOCS1-Mediated NF-κB Pathway.

Under the condition of chronic obesity, an increased level of free fatty acids along with low oxygen tension in the adipose tissue creates a pathophysiological adipose tissue microenvironment (ATenv), leading to the impairment of adipocyte function and insulin resistance. Here, we found the synergistic effect of hypoxia and lipid (H + L) surge in fostering adipose tissue macrophage (ATM) inflammation and polarization. ATenv significantly increased miR-210-3p expression in ATMs which promotes NF-κB activation-dependent proinflammatory cytokine expression along with the downregulation of anti-inflammatory cytokine expression. Interestingly, delivery of miR-210-3p mimic significantly increased macrophage inflammation in the absence of H + L co-stimulation, while miR-210-3p inhibitor notably compromised H + L-induced macrophage inflammation through increased production of suppressor of cytokine signaling 1 (SOCS1), a negative regulator of the NF-κB inflammatory signaling pathway. Mechanistically, miR-210 directly binds to the 3'-UTR of SOCS1 mRNA and silences its expression, thus preventing proteasomal degradation of NF-κB p65. Direct delivery of anti-miR-210-3p LNA in the ATenv markedly rescued mice from obesity-induced adipose tissue inflammation and insulin resistance. Thus, miR-210-3p inhibition in ATMs could serve as a novel therapeutic strategy for managing obesity-induced type 2 diabetes.

Hypoxia disturbs the Migration and Adhesion characteristics of Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) have been successfully used in treating many diseases which being verified by many preclinical and clinical trials. Despite the exciting therapeutic potential of MSCs, multiple challenges encountered which hinder researchers from achieving successful clinical translations. Many studies have showed that moderate hypoxia (1-7% O2) considered as an important regulator of MSCs homing, migration, and differentiation. Additionally, low oxygen tension levels have been implicated in the maintenance of MSCs quiescence and plasticity in general. On the other hand, severe hypoxia (<1% O2) negatively affects the in vitro therapeutic potential of MSCs and causing their poor survival. Using Elisa assay we assessed some major adhesion markers that are known to be secreted by MSCs and play a role in cell-cell and cell-matrix adhesion under normoxia (21% O2) and severe hypoxia (0.5% O2). These markers including: SDF1-α, CXCR4, FAK, VEGF and ICAM-1. The results showed a significant drop in the adhesion markers in MSCs under severe hypoxia in comparing to normoxia, which causes a disruption in the cell-cell adhesion abilities of MSCs and ultimately can affect the incorporation of MSCs at the host site. These Findings can open new avenue to improve the attachment of MSCs at the transplantation site by targeting the adhesion and chemokines markers.

Andean Aymara Enriched Genetic Variants Are Beneficial to High Altitude Adaptation of Andean Quechuas Living at 5000 m

Populations living at high altitude developed distinct evolutionary genetic adaptations allowing them to exist in extreme hypobaric hypoxia condition. Tibetans and Andean highlanders (Aymaras and Quechuas) have inhabited regions over ~4000 m for 44,000 and 14,000 years, respectively (PMID: 28448578, 25342802). Unlike other high-altitude populations, such as Tibetans, Andeans' Aymaras and Quechuas have higher hemoglobin levels. Tibetan genomic analyses revealed evolutionary selected genetic signatures EPAS1, EGLN1 and PKLR genes (PMID:25129147; Song, ASH 2018). However non-DenisovanEPAS1 variants (rs13005507 and rs142764723) are present in Aymaras and Quechuas, and ~56% of Aymaras have Tibetan PKLR variants (Song, ASH 2018). Our whole genome study found that most Aymara evolutionary-enriched genes (BRNIP3, NOS2, SH2B1, and TBX5) are associated with cardiopulmonary development but not with hemoglobin levels (PMID: 29100088); different genomic selection was reported in Andean Quechuas (PMID:23954164). We then found previously unreported Aymara enriched NFKB1 single nucleotide polymorphisms (SNP) by integrative analysis of the Aymaras' genome and transcriptome, this SNP is also enriched in Quechuas but to the lesser degree. Decreased NFKB1 results in increased NF-kB levels leading to NF-kB driven increased inflammation as well as increased HIFs activity (PMID: 26513405) and is associated with high hemoglobin and inflammatory protein and transcript levels in Aymaras (Song, ASH 2018). We studied the presence of Aymara enriched SNPs in Quechua, one of Andean population living in Chorolque (5000 m) and their association with phenotypes at high altitude. We genotyped 5 Aymara enriched SNPs and PKLR (Table) in Quechuas (45 men, 14 women) living in Chorolque (5000 m) mining district, Potosi-Bolivia. All men were smokers while none of women were smokers. We also measured laboratory phenotypes leukocytes, platelets, lymphocytes, monocytes, neutrophils, as well as hemoglobin dissociation p50, SpO2, lactose, hemoglobin and hematocrit to study if genetic variants play a role in changes in these phenotypes. All Aymara enriched allele frequencies in Quechuas were lower than in Aymaras (Table). The allele frequencies of BRINP3, SH2B1, TBX5 in Quechuas were significantly different from those in Aymara, suggesting that Quechuas share some but not all genetic background with Aymaras. Since all men were smokers, we tested smoking effect on these phenotypes. Except hemoglobin and hematocrit levels, other phenotypes were comparable to women without smoking history. BRINP3 SNP positively correlated with SpO2 levels (r=0.2252, p=0.0893), suggesting that this SNP may have a role in delivery oxygen to tissue. PKLR SNP is associated with decreased levels of pyruvate kinase transcript levels, leading to increase 2,3 DPG and shifting hemoglobin dissociation curve to the right (increase of p50) (Song, ASH 2018). However, in these subjects, we did not find association in p50 but positive correlation with SpO2 (r=0.3423, p=0.0082). It suggests that presence of BRINP3 and PKLR SNPs is beneficial to live at low oxygen tension by delivering more oxygen to tissues. Total leukocytes, lymphocytes, and neutrophils were negatively correlated with NFKB1 SNP (r=-0.2349, r=-0.281, and r=-0.1725, respectively) which differed from our previous study of Aymaras at La Paz, suggesting that Quechuas may have different mechanisms in responding to inflammation from Aymaras. None of SNPs were associated with hematocrit and hemoglobin levels in men; however, we could not exclude effect of smoking. In females, NOS2 SNP were positively correlated with both hemoglobin and hematocrit (r=0.5513, p=0.0246). NO (nitric oxide) synthesized by NOS2 inhibits erythropoiesis (PMID: 18282521), suggesting that NOS2 SNP may decrease NO production resulting in inducing erythropoiesis in Quechuas. We conclude that while Quechuas and Aymaras share some genetic variants, but they differ in degree of selection for these SNPs. BRINP3 and PKLR SNPs are helpful to transfer more oxygen to tissues at high altitude. NFKB1 SNPs` inverse correlation with immune cells may provide protective functions in response to increased inflammation at high altitude (PMID: 26855492). Decreased NO production by NOS2 SNP may augment erythropoiesis in Quechuas, resulting in their higher hemoglobin and hematocrit at high altitude compared to Europeans. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal