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Cuervo, A., Dans, P. D., Carrascosa, J. L., Orozco, M., Gomila, G., Fumagalli, L., (2014). Direct measurement of the dielectric polarization properties of DNA Proceedings of the National Academy of Sciences of the United States of America 111, (35), E3624-E3630

The electric polarizability of DNA, represented by the dielectric constant, is a key intrinsic property that modulates DNA interaction with effector proteins. Surprisingly, it has so far remained unknown owing to the lack of experimental tools able to access it. Here, we experimentally resolved it by detecting the ultraweak polarization forces of DNA inside single T7 bacteriophages particles using electrostatic force microscopy. In contrast to the common assumption of low-polarizable behavior like proteins (εr ~ 2–4), we found that the DNA dielectric constant is ~ 8, considerably higher than the value of ~ 3 found for capsid proteins. State-of-the-art molecular dynamic simulations confirm the experimental findings, which result in sensibly decreased DNA interaction free energy than normally predicted by Poisson–Boltzmann methods. Our findings reveal a property at the basis of DNA structure and functions that is needed for realistic theoretical descriptions, and illustrate the synergetic power of scanning probe microscopy and theoretical computation techniques.

Keywords: Atomic force microscopy, Atomistic simulations, DNA packaging, DNA-ligand binding, Poisson-Boltzmann equation, capsid protein, DNA, double stranded DNA, amino acid composition, article, atomic force microscopy, bacteriophage, bacteriophage T7, dielectric constant, dipole, DNA binding, DNA packaging, DNA structure, electron microscopy, ligand binding, nonhuman, polarization, priority journal, protein analysis, protein DNA interaction, scanning probe microscopy, static electricity, virion, virus capsid, virus particle, atomic force microscopy, atomistic simulations, DNA packaging, DNA-ligand binding, Poisson-Boltzmann equation, Bacteriophage T7, Capsid, Cations, Dielectric Spectroscopy, DNA, DNA, Viral, DNA-Binding Proteins, Electrochemical Techniques, Ligands, Microscopy, Atomic Force, Models, Chemical, Nuclear Proteins


Dalmases, M., Torres, M., Márquez-Kisinousky, L., Almendros, I., Planas, A. M., Embid, C., Martínez-Garcia, M. A., Navajas, D., Farré, R., Montserrat, J. M., (2014). Brain tissue hypoxia and oxidative stress induced by obstructive apneas is different in young and aged rats Sleep , 37, (7), 1249-1256

Study Objectives: To test the hypotheses that brain oxygen partial pressure (PtO2) in response to obstructive apneas changes with age and that it might lead to different levels of cerebral tissue oxidative stress. Design: Prospective controlled animal study. Setting: University laboratory. Participants: Sixty-four male Wistar rats: 32 young (3 mo old) and 32 aged (18 mo). Interventions: Protocol 1: Twenty-four animals were subjected to obstructive apneas (50 apneas/h, lasting 15 sec each) or to sham procedure for 50 min. Protocol 2: Forty rats were subjected to obstructive apneas or sham procedure for 4 h. Measurements and Results: Protocol 1: Real-time PtO2 measurements were performed using a fast-response oxygen microelectrode. During successive apneas cerebral cortex PtO2 presented a different pattern in the two age groups; there was a fast increase in young rats, whereas it remained without significant changes between the beginning and the end of the protocol in the aged group. Protocol 2: Brain oxidative stress assessed by lipid peroxidation increased after apneas in young rats (1.34 ± 0.17 nmol/mg of protein) compared to old ones (0.63 ± 0.03 nmol/mg), where a higher expression of antioxidant enzymes was observed. Conclusions: The results suggest that brain oxidative stress in aged rats is lower than in young rats in response to recurrent apneas, mimicking obstructive sleep apnea. This could be due to the different PtO2 response observed between age groups and the increased antioxidant expression in aged rats.

Keywords: Aging, Animal model, Obstructive apnea, Oxidative stress, Tissue oxygenation, antioxidant, glutathione disulfide, aged, animal experiment, animal model, animal tissue, apnea, arterial oxygen saturation, article, brain cortex, brain oxygen tension, brain tissue, controlled study, groups by age, hypoxia, lipid peroxidation, male, nonhuman, oxidative stress, pressure, priority journal, rat


Melo, E., Cárdenes, N., Garreta, E., Luque, T., Rojas, M., Navajas, D., Farré, R., (2014). Inhomogeneity of local stiffness in the extracellular matrix scaffold of fibrotic mouse lungs Journal of the Mechanical Behavior of Biomedical Materials , 37, 186-195

Lung disease models are useful to study how cell engraftment, proliferation and differentiation are modulated in lung bioengineering. The aim of this work was to characterize the local stiffness of decellularized lungs in aged and fibrotic mice. Mice (2- and 24-month old; 14 of each) with lung fibrosis (N=20) and healthy controls (N=8) were euthanized after 11 days of intratracheal bleomycin (fibrosis) or saline (controls) infusion. The lungs were excised, decellularized by a conventional detergent-based (sodium-dodecyl sulfate) procedure and slices of the acellular lungs were prepared to measure the local stiffness by means of atomic force microscopy. The local stiffness of the different sites in acellular fibrotic lungs was very inhomogeneous within the lung and increased according to the degree of the structural fibrotic lesion. Local stiffness of the acellular lungs did not show statistically significant differences caused by age. The group of mice most affected by fibrosis exhibited local stiffness that were ~2-fold higher than in the control mice: from 27.2±1.64 to 64.8±7.1. kPa in the alveolar septa, from 56.6±4.6 to 99.9±11.7. kPa in the visceral pleura, from 41.1±8.0 to 105.2±13.6. kPa in the tunica adventitia, and from 79.3±7.2 to 146.6±28.8. kPa in the tunica intima. Since acellular lungs from mice with bleomycin-induced fibrosis present considerable micromechanical inhomogeneity, this model can be a useful tool to better investigate how different degrees of extracellular matrix lesion modulate cell fate in the process of organ bioengineering from decellularized lungs.

Keywords: Ageing, Atomic force microscopy, Decellularization, Lung fibrosis, Tissue engineering, Atomic force microscopy, Biological organs, Peptides, Sodium dodecyl sulfate, Sodium sulfate, Tissue engineering, Ageing, Decellularization, Extracellular matrices, Healthy controls, Inhomogeneities, Lung fibrosis, Micro-mechanical, Statistically significant difference, Mammals, bleomycin, adventitia, animal experiment, animal model, article, atomic force microscopy, bleomycin-induced pulmonary fibrosis, cell fate, controlled study, extracellular matrix, female, intima, lung alveolus, lung fibrosis, lung mechanics, mechanical probe, microenvironment, mouse, nonhuman, pleura, priority journal, rigidity, tissue engineering


Nonaka, P. N., Uriarte, J. J., Campillo, N., Melo, E., Navajas, D., Farré, R., Oliveira, L. V. F., (2014). Mechanical properties of mouse lungs along organ decellularization by sodium dodecyl sulfate Respiratory Physiology & Neurobiology , 200, 1-5

Lung decellularization is based on the use of physical, chemical, or enzymatic methods to break down the integrity of the cells followed by a treatment to extract the cellular material from the lung scaffold. The aim of this study was to characterize the mechanical changes throughout the different steps of lung decellularization process. Four lungs from mice (C57BL/6) were decellularized by using a conventional protocol based on sodium dodecyl sulfate. Lungs resistance (RL) and elastance (EL) were measured along decellularization steps and were computed by linear regression fitting of tracheal pressure, flow, and volume during mechanical ventilation. Transients differences found were more distinct in an intermediate step after the lungs were rinsed with deionized water and treated with 1% SDS, whereupon the percentage of variation reached approximately 80% for resistance values and 30% for elastance values. In conclusion, although a variation in extracellular matrix stiffness was observed during the decellularization process, this variation can be considered negligible overall because the resistance and elastance returned to basal values at the final decellularization step.

Keywords: Lung bioengineering, Lung decellularization, Organ scaffold, dodecyl sulfate sodium, animal tissue, article, artificial ventilation, compliance (physical), controlled study, enzyme chemistry, extracellular matrix, female, flow, lung, lung decellularization, lung pressure, lung resistance, mouse, nonhuman, positive end expiratory pressure, priority journal, rigidity, tissue engineering, trachea pressure