The impact of hyperoxia on the neonatal and adult developing dendritic cell

Oxygen-Generating Scaffolds: One Step Closer to the Clinical Translation of Tissue Engineered Products

The lack of oxygen supply in engineered constructs has been an ongoing challenge for tissue engineering and regenerative medicine. Upon implantation of an engineered tissue, spontaneous blood vessel formation does not happen rapidly, therefore, there is typically a limited availability of oxygen in engineered biomaterials. Providing oxygen in large tissue-engineered constructs is a major challenge that hinders the development of clinically relevant engineered tissues. Similarly, maintaining adequate oxygen levels in cell-laden tissue engineered products during transportation and storage is another hurdle. There is an unmet demand for functional scaffolds that could actively produce and deliver oxygen, attainable by incorporating oxygen-generating materials. Recent approaches include encapsulation of oxygen-generating agents such as solid peroxides, liquid peroxides, and fluorinated substances in the scaffolds. Recent approaches to mitigate the adverse effects, as well as achieving a sustained and controlled release of oxygen, are discussed. Importance of oxygen-generating materials in various tissue engineering approaches such as ex vivo tissue engineering, in situ tissue engineering, and bioprinting are highlighted in detail. In addition, the existing challenges, possible solutions, and future strategies that aim to design clinically relevant multifunctional oxygen-generating biomaterials are provided in this review paper.

Comparison of Preterm and Term Wharton's Jelly-Derived Mesenchymal Stem Cell Properties in Different Oxygen Tensions

Mesenchymal stem cells (MSCs) have shown promise as therapeutic agents in treating morbidities associated with premature birth. MSCs derived from the human umbilical cord are easy to isolate and have low immunogenicity and a robust ability to secrete paracrine factors. To date, there are no studies evaluating preterm versus term umbilical cord tissue-derived MSCs. Therefore, our aim was twofold: (1) to compare stem cell properties in preterm versus term MSCs and (2) to examine the impact of oxygen tension on stem cell behavior. Umbilical cord tissue was obtained from 5 preterm and 5 term neonates. The cells were isolated and characterized as MSCs in accordance with the International Society for Cellular Therapy. We exposed MSCs to different oxygen tensions to examine the impact of environmental factors on cell performance. We studied the following stem cell properties: (i) motility, (ii) proliferation, (iii) senescence, (iv) cell viability, (v) colony-forming unit efficiency, and (vi) inflammatory cytokine expression. Under normoxia (21% O2), cells from preterm and term infants had similar properties. Under hypoxic conditions (1% O2), term MSCs had better cell proliferation; however, cells exposed to hyperoxia (90% O2) had the slowest motility and lowest cell viability (p < 0.05). There was no difference in the expression of senescence or cytokine expression between the groups. The term cells demonstrated more colony-forming efficiency than the preterm cells. In sum, our preliminary findings suggest that MSCs derived from term and preterm umbilical cords have similar characteristics, offering the potential of future autologous/allogeneic MSC transplants in neonates.

Effects of oxygen concentration and pressure on Drosophila melanogaster: oxidative stress, mitochondrial activity, and survivorship

Organisms are known to be equipped with an adaptive plasticity as the phenotype of traits in response to the imposed environmental challenges as they grow and develop. In this study, the effects of extreme changes in oxygen availability and atmospheric pressure on physiological phenotypes of Drosophila melanogaster were investigated to explore adaptation mechanisms. The changes in citrate synthase activity (CSA), lifespan, and behavioral function in different atmospheric conditions were evaluated. In the CAS test, hyperoxia significantly increased CSA; both hypoxia and hyperbaric conditions caused a significant decrease in CSA. In the survivorship test, all changed atmospheric conditions caused a significant reduction in lifespan. The lifespan reduced more after hypoxia exposure than after hyperbaria exposure. In behavioral function test, when mechanical agitation was conducted, bang-sensitive flies showed a stereotypical sequence of initial muscle spasm, paralysis, and recovery. The percentage of individuals that displayed paralysis or seizure was measured on the following day and after 2 weeks from each exposure. The majority of flies showed seizure behavior 15 days after exposure, especially after 3 h of exposure. The percentage of individuals that did not undergo paralysis or seizure and was able to move in the vial, was also tested. The number of flies that moved and raised the higher level of the vial decreased after exposure. Animal's speed decreased significantly 15 days after exposure to extreme environmental conditions. In summary, the alteration of oxygen availability and atmospheric pressure may lead to significant changes in mitochondria mass, lifespan, and behavioral function in D. melanogaster.

Review: Hypoxic and oxidative stress resistance in Drosophila melanogaster

Oxygen (O(2)) is essential for aerobic life; however, the level of O(2), whether too low (hypoxia) or too high (hyperoxia), can induce oxidative injury and increase morbidity and mortality. Disruption of O(2) homeostasis represents a major aspect of many disease etiologies and pathobiology. In the past, our laboratory has been using Drosophila melanogaster to investigate the cellular and molecular aspects of the response to hypoxia and oxidative stress. There are several advantages for using Drosophila as a model system, the most important one being an evolutionary conservation of genetic and signaling pathways from Drosophila to mammals. As a proof of this concept, we have shown that we can substantially improve the tolerance of human cells in culture by transfecting these cells with particular Drosophila genes. In this review, we summarize the recent findings from our laboratory using Drosophila as a model system to investigate the genetic basis of hypoxia/hyperoxia tolerance. We have done microarray studies and identified several oxidative stress resistance genes that play an important role in individual paradigms such as constant or intermittent hypoxia, short term (days) or long term (generations) hypoxia/hyperoxia. Our studies provide evidence that a pattern of oxidative stress is specific in inducing a gene expression profile which, in turn, plays an important role in modulating the phenotype. To improve our understanding of oxidative and hypoxic stress as well as its associated diseases, multi-disciplinary approaches are necessary and critical in the study of complicated issues in systems biology.

Understanding the effects of oxygen administration in haemorrhagic shock

AIMS AND OBJECTIVES

the aim of this article is to provide a review of the literature regarding oxygen administration and the use of oxygen in patients experiencing haemorrhagic shock (HS).

RESULTS

oxygen is administered to patients to assist them in maintaining oxygenation. The administration of oxygen is complex and varies significantly among patients. In order to optimize patient care, clinicians need to be aware of the potential effects, both beneficial and harmful, that oxygen can have on the body.

INCLUSION AND EXCLUSION CRITERIA

literature inclusion criteria for this article was any article (1995 to present) pertaining to oxygen administration and HS. Also included were articles related to tissue injury caused by an overabundance of free radicals with the administration of oxygen. Articles related to oxygen and wound healing, pollution, aerospace, food and industrial uses were excluded.

CONCLUSIONS

this review of the literature provides an overview of the use of oxygen in clinical practice and HS. The harmful effects of oxygen are highlighted to alert the clinician to this potential when there is an overabundance of oxygen.

RELEVANCE TO CLINICAL PRACTICE

oxygen is one of the most common drugs used in the medical community; however, the effects of oxygen on the body are not well understood. The use of oxygen if not prescribed correctly can cause cellular damage and death. Clinicians need to be more aware of the effects of oxygen and the damage it may cause if not administered properly.

Antimicrobial peptides increase tolerance to oxidant stress in Drosophila melanogaster

It is well appreciated that reactive oxygen species (ROS) are deleterious to mammals, including humans, especially when generated in abnormally large quantities from cellular metabolism. Whereas the mechanisms leading to the production of ROS are rather well delineated, the mechanisms underlying tissue susceptibility or tolerance to oxidant stress remain elusive. Through an experimental selection over many generations, we have previously generated Drosophila melanogaster flies that tolerate tremendous oxidant stress and have shown that the family of antimicrobial peptides (AMPs) is over-represented in these tolerant flies. Furthermore, we have also demonstrated that overexpression of even one AMP at a time (e.g. Diptericin) allows wild-type flies to survive much better in hyperoxia. In this study, we used a number of experimental approaches to investigate the potential mechanisms underlying hyperoxia tolerance in flies with AMP overexpression. We demonstrate that flies with Diptericin overexpression resist oxidative stress by increasing antioxidant enzyme activities and preventing an increase in ROS levels after hyperoxia. Depleting the GSH pool using buthionine sulfoximine limits fly survival, thus confirming that enhanced survival observed in these flies is related to improved redox homeostasis. We conclude that 1) AMPs play an important role in tolerance to oxidant stress, 2) overexpression of Diptericin changes the cellular redox balance between oxidant and antioxidant, and 3) this change in redox balance plays an important role in survival in hyperoxia.

Experimental selection for Drosophila survival in extremely high O2 environments

Although oxidative stress is deleterious to mammals, the mechanisms underlying oxidant susceptibility or tolerance remain to be elucidated. In this study, through a long-term laboratory selection over many generations, we generated a Drosophila melanogaster strain that can live and reproduce in very high O₂ environments (90% O₂), a lethal condition to naïve flies. We demonstrated that tolerance to hyperoxia was heritable in these flies and that these hyperoxia-selected flies exhibited phenotypic differences from naïve flies, such as a larger body size and increased weight by 20%. Gene expression profiling revealed that 227 genes were significantly altered in expression and two third of these genes were down-regulated. Using a mutant screen strategy, we studied the role of some altered genes (up- or down-regulated in the microarrays) by testing the survival of available corresponding P-element or UAS construct lines under hyperoxic conditions. We report that down-regulation of several candidate genes including Tropomyosin 1, Glycerol 3 phosphate dehydrogenase, CG33129, and UGP as well as up-regulation of Diptericin and Attacin conferred tolerance to severe hyperoxia. In conclusion, we identified several genes that were not only altered in hyperoxia-selected flies but we also prove that these play an important role in hyperoxia survival. Thus our study provides a molecular basis for understanding the mechanisms of hyperoxia tolerance.