title: Ageing and chronic intermittent hypoxia mimicking sleep apnea do not modify local brain tissue stiffness in healthy mice.
abstract: Recent evidence suggests that obstructive sleep apnea (OSA) may increase the risk of Alzheimer´s disease (AD), with the latter promoting alterations in brain tissue stiffness, a feature of ageing. Here, we assessed the effects of age and intermittent hypoxia (IH) on brain tissue stiffness in a mouse model of OSA. Two-month-old and 18-month-old mice (N=10 each) were subjected to IH (20% O240s - 6% O220s) for 8 weeks (6h/day). Corresponding control groups for each age were kept under normoxic conditions in room air (RA). After sacrifice, the brain was excised and 200-micron coronal slices were cut with a vibratome. Local stiffness of the cortex and hippocampus were assessed in brain slices placed in an Atomic Force Microscope. For both brain regions, the Young's modulus (E) in each animal was computed as the average values from 9 force-indentation curves. Cortex E mean (±SE) values were 442±122Pa (RA) and 455±120 (IH) for young mice and 433±44 (RA) and 405±101 (IH) for old mice. Hippocampal E values were 376±62 (RA) and 474±94 (IH) for young mice and 486±93 (RA) and 521±210 (IH) for old mice. For both cortex and hippocampus, 2-way ANOVA indicated no statistically significant effects of age or challenge (IH vs. RA) on E values. Thus, neither chronic IH mimicking OSA nor ageing up to late middle age appear to modify local brain tissue stiffness in otherwise healthy mice.
authors.affiliation: Unitat Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain; Institut de Bioenginyeria de Catalunya, Barcelona, Spain.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Jorba
authors.affiliation: Unitat Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
authors.forename: Maria José
authors.initials: MJ
authors.lastname: Menal
authors.affiliation: Sleep Lab, Hospital Clinic Barcelona, Barcelona, Spain; CIBER de Enfermedades Respiratorias, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Torres
authors.affiliation: Section of Pediatric Sleep Medicine, Department of Pediatrics, Pritzker School of Medicine, Biological Sciences Division, The University of Chicago, Chicago, IL, USA.
authors.forename: David
authors.initials: D
authors.lastname: Gozal
authors.affiliation: Unitat Trastorns Cognitius, Clinical Neuroscience Research, IRBLleida-Hospital Universitari Santa Maria, Lleida, Spain.
authors.forename: Gerard
authors.initials: G
authors.lastname: Piñol-Ripoll
authors.affiliation: Dept. Mort i Proliferació Cel.lular, Institut d'Investigacions Biomèdiques de Barcelona (IIBB-CSIC), CIBERNED, Spain; Institut Investigacions Biomediques August Pi Sunyer, Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Colell
authors.affiliation: Sleep Lab, Hospital Clinic Barcelona, Barcelona, Spain; CIBER de Enfermedades Respiratorias, Madrid, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Montserrat
authors.affiliation: Unitat Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain; Institut de Bioenginyeria de Catalunya, Barcelona, Spain; CIBER de Enfermedades Respiratorias, Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Navajas
authors.affiliation: Unitat Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain; CIBER de Enfermedades Respiratorias, Madrid, Spain; Institut Investigacions Biomediques August Pi Sunyer, Barcelona, Spain.
authors.forename: Ramon
authors.initials: R
authors.lastname: Farré
authors.affiliation: Unitat Biofísica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain; CIBER de Enfermedades Respiratorias, Madrid, Spain; Institut Investigacions Biomediques August Pi Sunyer, Barcelona, Spain. Electronic address: isaac.almendros@ub.edu.
authors.forename: Isaac
authors.initials: I
authors.lastname: Almendros
mesh_terms: D000375:Aging; D000818:Animals; D001921:Brain / Q000473:pathology*; D004195:Disease Models, Animal; D055119:Elastic Modulus; D000860:Hypoxia / Q000503:physiopathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*
keywords: Atomic Force Microscopy; Brain mechanics; Cortex stiffness; Hippocampus stiffness; Obstructive sleep apnea; Young's modulus