Značajke neuroinflamacije tijekom kronične intermitentne hipoksije na mišjem modelu opstruktivne apneje spavanja

doctoral thesis

• Title (english): Characteristics of neuroinflammation during chronic intermittent hypoxia, a mouse model of obstructive sleep apnea
• Author: Dora Polšek
• Mentor: Srećko Gajović (mentor)
• Mentor: Ivana Rosenzweig (komentor)
• Committee member: nije dostupno (član povjerenstva)
• Granter: University of Zagreb; School of Medicine; Zagreb
• Defense date and country: 2017-09-11, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Clinical Medical Sciences
• Universal decimal classification (UDC): 61 - Medical sciences

Abstract

Opstruktivna apneja spavanja (OSA) kronična je, često neprepoznata, multisistemska bolest karakterizirana intermitentnom hipoksijom (IH) i fragmentacijom sna koja nastupa zbog periodičke opstrukcije gornjeg dišnog puta tijekom spavanja. OSA je povezana s brojnim komorbiditetima, od kojih su najvažnije kardiovaskularne bolesti, moždani udar i Alzheimerova bolest (AD). Za potvrdu pretpostavke kako su upalni procesu u mozgu bolesnika s OSA-om u pozadini povezanosti ove bolesti s AD, potrebno je razumijevanje upalnih procesa u OSA-i. Provedeno je istraživanje na mišjem modelu OSA-e kako bi se utvrdile značajke neuroinflamacije u životinja izloženih IH.
Za optimizaciju modela IH razvijen je sustav kojim se hipoksija brzo i precizno regulirala. Transgenični TLR2-luc-GFP miševi izloženi su IH (N=20) i tijekom 21 dan praćeni in vivo snimanjem bioluminiscenicije, dok je kontrolna skupina (N=6) praćena na isti način bez izlaganja IH. Skupine miševa sa i bez Tlr2 gena izložene IH (N(TLR2 IH)= 15, N(TLR2-/- IH)= 15) te njihove kontrole (N(TLR2 CTRL)= 11, N(TLR2-/- CTRL)= 8) podvrgnute su testu visenja na repu, otvorenog polja i Y-labirinta. Mozgovi su izolirani i snimljeni ex vivo magnetskom rezonancom te su imunohistokemijskim bojanjem kvantificirane stanice mikroglije (Iba1+), astrocita (GFAP+) i cFos-pozitivni neuroni.
Snimanjem bioluminiscencije pokazano je akutno povišenje ekspresije TLR2 koje ostaje kronično povišeno tijekom 3 tjedna izlaganja IH. U TLR2 IH skupini pokazana je hipertrofija hipokampusa, motornog i cingulatnog korteksa te hipotrofija talamusa i piriformnog korteksa. Strukturne promjene TLR2-/- IH skupine bile su manje izražene u velikom mozgu no pokazana je hipotrofija struktura mezencefalona, ponsa i produljene moždine te hipertrofija malog mozga. IH ne utječe na prostorno pamćenje i opću pokretnost životinja ali pojačava pokretnost životinja na testu visenja na repu. Nije pokazan utjecaj IH na promjene u broju stanica mikroglije, astrocita i c-Fos-pozitivnih neurona.
IH uzrokuje akutno i kronično povišenje ekspresije TLR2 u mozgu te uzrokuje strukturne promjene mozga izraženije u životinjama sa pristunim genom TLR2. IH uzrokuje ograničene funkcionalne i histološke promjene mozga koje se nisu razlikovale među skupinama sa i bez gena TLR2.

Abstract (english)

Obstructive sleep apnea (OSA) is a chronic, underdiagnosed, multi-system disease characterized by intermittent hypoxia (IH) and sleep fragmentation that occurs due to periodic upper airway obstruction during sleep. OSA often presents with multiple comorbidities, the most important of which are cardiovascular diseases, stroke and Alzheimer's dementia (AD). Detailed research is needed to confirm the hypothesis that neuroinflammation is the common ethiopathogenic background for both OSA and AD. The study focused on establishing the properties of neuroinflammation in animals exposed to IH, the mouse model of OSA.
To optimize the IH model a fast and precise system was developed. Transgenic TLR2-luc-GFP mice underwent 21 days of IH (N=20) and their TLR2 expression was followed using in vivo bioluminescenc imaging (BLI), while the controls (N=6) were imaged in the same way without IH exposure. Groups of mice with and without Tlr2 gene exposed to IH (N(TLR2 IH)= 15, N(TLR2-/- IH)= 15) and their controls (N(TLR2 CTRL)= 11, N(TLR2-/- CTRL)= 8) were tested using the tail suspension test (TST), open field and Y maze. The brains were subsequently isolated and imaged ex vivo using MRI. Immunohistochemical staining for microglia (Iba1), astrocytes (GFAP) and c-Fos positive neurons was quantified.
BLI showed an acute upregulation of TLR2 after IH exposure that remained elevated throughout the 21-day protocol. Bilateral hypertrophy of the hippocampal, and left motor and cingulate cortex as well as hypotrophy of the thalamus and piriform cortex were found in the TLR2 IH group. Structural changes were less pronounced in the TLR2-/- IH group in the cerebrum, while significant hypotrophic changes were found in the midbrain, pons and medulla as well as hypertrophy of the cerebellum. Behavioral and histological testing found limited effects that warrant further investigation.
IH exposure caused an acute and chronic upregulation of TLR2 expression in the brain and induced structural changes that were more pronounced in animals with the functional TLR2 gene. IH caused limited functional and histological changes in the brain.

• Keywords: medicina
• Keywords (english): medicine
• Language: croatian
• URN:NBN: urn:nbn:hr:105:474270
• Study programme: Title: Neuroscience; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje biomedicine i zdravstva (doktor/doktorica znanosti, područje biomedicine i zdravstva)
• Type of resource: Text
• Extent: 147 str.
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-05-05 08:44:43