Delayed histochemical alterations within the neurovascular unit due to transient focal cerebral ischemia and experimental treatment with neurotrophic factors

PLoS One. 2017 Apr 26;12(4):e0174996. doi: 10.1371/journal.pone.0174996. eCollection 2017.

Abstract

Current stroke therapy is focused on recanalizing strategies, but neuroprotective co-treatments are still lacking. Modern concepts of the ischemia-affected neurovascular unit (NVU) and surrounding penumbra emphasize the complexity during the transition from initial damaging to regenerative processes. While early treatment with neurotrophic factors was shown to result in lesion size reduction and blood-brain barrier (BBB) stabilization, cellular consequences from these treatments are poorly understood. This study explored delayed cellular responses not only to ischemic stroke, but also to an early treatment with neurotrophic factors. Rats underwent 60 minutes of focal cerebral ischemia. Fluorescence labeling was applied to sections from brains perfused 7 days after ischemia. Analyses focused on NVU constituents including the vasculature, astrocytes and microglia in the ischemic striatum, the border zone and the contralateral hemisphere. In addition to histochemical signs of BBB breakdown, a strong up-regulation of collagen IV and microglia activation occurred within the ischemic core with simultaneous degradation of astrocytes and their endfeet. Activated astroglia were mainly depicted at the border zone in terms of a glial scar formation. Early treatment with pigment epithelium-derived factor (PEDF) resulted in an attenuation of the usually up-regulated collagen IV-immunoreactivity. However, glial activation was not influenced by treatment with PEDF or the epidermal growth factor (EGF). In conclusion, these data on ischemia-induced cellular reactions within the NVU might help to develop treatments addressing the transition from injury towards regeneration. Thereby, the integrity of the vasculature in close relation to neighboring structures like astrocytes appears as a promising target.

MeSH terms

  • Animals
  • Aquaporin 4 / metabolism
  • Astrocytes / metabolism
  • Astrocytes / pathology
  • Blood-Brain Barrier / drug effects
  • Blood-Brain Barrier / metabolism
  • Brain / diagnostic imaging
  • Brain / drug effects*
  • Brain / metabolism
  • Brain / pathology
  • Collagen Type IV / metabolism
  • Disease Models, Animal
  • Epidermal Growth Factor / pharmacology
  • Epidermal Growth Factor / therapeutic use
  • Eye Proteins / pharmacology
  • Eye Proteins / therapeutic use
  • Glial Fibrillary Acidic Protein / metabolism
  • Ischemic Attack, Transient / diagnostic imaging
  • Ischemic Attack, Transient / drug therapy
  • Ischemic Attack, Transient / pathology*
  • Magnetic Resonance Imaging
  • Male
  • Microglia / metabolism
  • Microglia / pathology
  • Microscopy, Fluorescence
  • Nerve Growth Factors / pharmacology*
  • Nerve Growth Factors / therapeutic use
  • Rats
  • Rats, Sprague-Dawley
  • Serpins / pharmacology
  • Serpins / therapeutic use
  • Up-Regulation / drug effects
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • Aquaporin 4
  • Collagen Type IV
  • Eye Proteins
  • GFAP protein, rat
  • Glial Fibrillary Acidic Protein
  • Nerve Growth Factors
  • Serpins
  • Vascular Endothelial Growth Factor A
  • pigment epithelium-derived factor
  • Epidermal Growth Factor

Grant support

The study was mainly performed without external funding. During the revision process, some parts were supported by the Europäischer Sozialfonds (ESF, grant 100270131 to Dominik Michalski). Dr. Carsten Hobohm (University of Leipzig) is acknowledged for financial support during the early phase of the study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.