Fibroblast growth factor-2 induced by enriched environment enhances angiogenesis and motor function in chronic hypoxic-ischemic brain injury

PLoS One. 2013 Sep 30;8(9):e74405. doi: 10.1371/journal.pone.0074405. eCollection 2013.

Abstract

This study aimed to investigate the effects of enriched environment (EE) on promoting angiogenesis and neurobehavioral function in an animal model of chronic hypoxic-ischemic (HI) brain injury. HI brain damage was induced in seven day-old CD-1® mice by unilateral carotid artery ligation and exposure to hypoxia (8% O2 for 90 min). At six weeks of age, the mice were randomly assigned to either EE or standard cages (SC) for two months. Rotarod, forelimb-use asymmetry, and grip strength tests were performed to evaluate neurobehavioral function. In order to identify angiogenic growth factors regulated by EE, an array-based multiplex ELISA assay was used to measure the expression in frontal cortex, striatum, and cerebellum. Among the growth factors, the expression of fibroblast growth factor-2 (FGF-2) was confirmed using western blotting. Platelet endothelial cell adhesion molecule-1 (PECAM-1) and α-smooth muscle actin (α-SMA) were also evaluated using immunohistochemistry. As a result, mice exposed to EE showed significant improvements in rotarod and ladder walking performances compared to SC controls. The level of FGF-2 was significantly higher in the frontal cortex of EE mice at 8 weeks after treatment in multiplex ELISA and western blot. On the other hand, FGF-2 in the striatum significantly increased at 2 weeks after exposure to EE earlier than in the frontal cortex. Expression of activin A was similarly upregulated as FGF-2 expression pattern. Particularly, all animals treated with FGF-2 neutralizing antibody abolished the beneficial effect of EE on motor performance relative to mice not given anti-FGF-2. Immunohistochemistry showed that densities of α-SMA(+) and PECAM-1(+) cells in frontal cortex, striatum, and hippocampus were significantly increased following EE, suggesting the histological findings exhibit a similar pattern to the upregulation of FGF-2 in the brain. In conclusion, EE enhances endogenous angiogenesis and neurobehavioral functions mediated by upregulation of FGF-2 in chronic hypoxic-ischemic brain injury.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Analysis of Variance
  • Animals
  • Blotting, Western
  • DNA Primers / genetics
  • Enzyme-Linked Immunosorbent Assay
  • Fibroblast Growth Factor 2 / metabolism*
  • Housing, Animal*
  • Hypoxia-Ischemia, Brain / metabolism*
  • Immunohistochemistry
  • Mice
  • Muscle Strength / physiology
  • Neovascularization, Physiologic / physiology*
  • Platelet Endothelial Cell Adhesion Molecule-1 / metabolism
  • Real-Time Polymerase Chain Reaction
  • Rotarod Performance Test

Substances

  • Actins
  • DNA Primers
  • Platelet Endothelial Cell Adhesion Molecule-1
  • alpha-smooth muscle actin, mouse
  • Fibroblast Growth Factor 2

Grants and funding

This study was supported by grants from the National Research Foundation (NRF-2010-0020408; 2010-0024334) funded by the Ministry of Education, Science and Technology, Republic of Korea, the 2011 Chyung Ki Lee Research Fund, the Yonsei University College of Medicine (6-2013-0045), and the Students' Association of the Graduate School of Yonsei University funded by the Graduate School of Yonsei University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.