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Updated: Sep 1, 2025
Stereological and Flow Cytometry Characterization of Leukocyte Subpopulations in Models of Transient or Permanent Cerebral Ischemia
Published on: December 28, 2014
Platelet Endothelial Cell Adhesion Molecule (PECAM/CD31) Blockade Modulates Neutrophil Recruitment Patterns and
Neil A Nadkarni1, Erika Arias2, Raymond Fang3
1Department of Neurology, Northwestern University, Chicago, Illinois.
Abstract:
The infiltration of polymorphonuclear leukocytes (PMNs) in ischemia-reperfusion injury (I/RI) has been implicated as a critical component of inflammatory damage following ischemic stroke. However, successful blockade of PMN transendothelial migration (TEM) in preclinical studies has not translated to meaningful clinical outcomes. To investigate this further, leukocyte infiltration patterns were quantified, and these patterns were modulated by blocking platelet endothelial cell adhesion molecule-1 (PECAM), a key regulator of TEM. LysM-eGFP mice and microscopy were used to visualize all myeloid leukocyte recruitment following ischemia/reperfusion. Visual examination showed heterogeneous leukocyte distribution across the infarct at both 24 and 72 hours after I/RI. A semiautomated process was designed to precisely map PMN position across brain sections. Treatment with PECAM function-blocking antibodies did not significantly affect total leukocyte recruitment but did alter their distribution, with more observed at the cortex at both early and later time points (24 hours: 89% PECAM blocked vs. 72% control; 72 hours: 69% PECAM blocked vs. 51% control). This correlated with a decrease in infarct volume. These findings suggest that TEM, in the setting of I/RI in the cerebrovasculature, occurs primarily at the cortical surface. The reduction of stroke size with PECAM blockade suggests that infiltrating PMNs may exacerbate I/RI and indicate the potential therapeutic benefit of regulating the timing and pattern of leukocyte infiltration after stroke.
Insights
Blocking platelet endothelial cell adhesion molecule-1 (PECAM) in stroke models altered polymorphonuclear leukocyte (PMN) distribution, reducing infarct size. This suggests targeting PMN infiltration patterns may offer therapeutic benefits for ischemic stroke.
Area of Science:
- Neuroscience
- Immunology
- Cardiovascular Research
Background:
- Polymorphonuclear leukocytes (PMNs) contribute to inflammatory damage in ischemic stroke.
- Previous attempts to block PMN transendothelial migration (TEM) have yielded limited clinical success.
- Understanding PMN infiltration patterns is crucial for developing effective stroke therapies.
Purpose of the Study:
- To quantify leukocyte infiltration patterns in ischemia-reperfusion injury (I/RI).
- To investigate the effect of blocking platelet endothelial cell adhesion molecule-1 (PECAM) on PMN distribution and infarct volume.
- To explore the therapeutic potential of modulating PMN infiltration in stroke.
Main Methods:
- Utilized LysM-eGFP mice and microscopy to visualize myeloid leukocyte recruitment after I/RI.
- Employed a semiautomated process to map PMN positions in brain sections.
- Administered PECAM function-blocking antibodies to modulate leukocyte infiltration.
Main Results:
- Leukocyte distribution was heterogeneous across the infarct at 24 and 72 hours post-I/RI.
- PECAM blockade altered PMN distribution, increasing cortical infiltration (24h: 89% vs. 72%; 72h: 69% vs. 51%).
- PECAM blockade correlated with a significant decrease in infarct volume.
Conclusions:
- Cerebrovascular TEM in I/RI predominantly occurs at the cortical surface.
- Modulating PMN infiltration patterns, specifically cortical distribution, may reduce stroke-induced damage.
- Targeting PECAM offers a potential therapeutic strategy for ischemic stroke by mitigating PMN-exacerbated injury.
