title: A murine model of inflammation-induced cerebral microbleeds.
abstract: Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to study cerebral microbleeds.
  
  
  
  Adult C57BL/6 mice were injected with LPS (3 or 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. At 2 or 7 days after the first injection, brains were harvested. Hematoxylin and eosin (H&E) and Prussian blue (PB) were used to stain fresh (acute) hemorrhages and hemosiderin (sub-acute) hemorrhages, respectively. Brain tissue ICAM-1, IgG, Iba1, and GFAP immunohistochemistry were used to examine endothelium activation, blood-brain barrier (BBB) disruption, and neuroinflammation. MRI and fluorescence microscopy were used to further confirm CMH development in this model.
  
  
  
  LPS-treated mice developed H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. No surface and negligible H&E-positive CMH were observed in saline-treated mice (n = 12). LPS (3 mg/kg; n = 10) produced significantly higher number, size, and area of H&E-positive CMH at 2 days. LPS (1 mg/kg; n = 9) produced robust development of PB-positive CMH at 7 days, with significantly higher number and area compared with saline (n = 9)-treated mice. CMH showed the highest distribution in the cerebellum followed by the sub-cortex and cortex. LPS-induced CMH were predominantly adjacent to cerebral capillaries, and CMH load was associated with indices of brain endothelium activation, BBB disruption, and neuroinflammation. Fluorescence microscopy confirmed the extravasation of red blood cells into the brain parenchyma, and MRI demonstrated the presence of cerebral microbleeds.
  
  
  
  LPS produced rapid and robust development of H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. The ease of development of both H&E- and PB-positive CMH makes the LPS-induced mouse model suitable to study inflammation-induced CMH.
authors: Department of Biopharmaceutical Sciences, School of Pharmacy, Keck Graduate Institute, Claremont, CA, USA.|Department of Neurology, University of California, Irvine, CA, USA.
authors: Rachita K
authors: RK
authors: Sumbria
authors: Department of Neurology, University of California, Irvine, CA, USA.
authors: Mher Mahoney
authors: MM
authors: Grigoryan
authors: Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA.
authors: Vitaly
authors: V
authors: Vasilevko
authors: Beckman Laser Institute, University of California, Irvine, CA, USA.
authors: Tatiana B
authors: TB
authors: Krasieva
authors: Department of Radiology, University of California, San Diego, CA, USA.
authors: Miriam
authors: M
authors: Scadeng
authors: Department of Neurology, University of California, Irvine, CA, USA.
authors: Alexandra K
authors: AK
authors: Dvornikova
authors: Department of Neurology, University of California, Irvine, CA, USA.
authors: Annlia
authors: A
authors: Paganini-Hill
authors: Department of Pathology and Laboratory Medicine, University of California, Irvine, CA, USA.
authors: Ronald
authors: R
authors: Kim
authors: Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA.
authors: David H
authors: DH
authors: Cribbs
authors: Department of Neurology, University of California, Irvine, CA, USA. mfisher@uci.edu.|Department of Pathology and Laboratory Medicine, University of California, Irvine, CA, USA. mfisher@uci.edu.|Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA. mfisher@uci.edu.|UC Irvine Medical Center, 101 The City Drive South, Shanbrom Hall, Room 121, Orange, CA, 92868, USA. mfisher@uci.edu.
authors: Mark J
authors: MJ
authors: Fisher
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000378:metabolism; D002543:Cerebral Hemorrhage / Q000139:chemically induced / Q000000981:diagnostic imaging* / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D007249:Inflammation / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D055806:Microvessels / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides
keywords: Animal models; Cerebral microbleeds; Cerebral microhemorrhage; Hemosiderin; Inflammation