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Ultrastructural Evidence of Degranulation of Eosinophils During Transmigration of Arterioles in Murine Lung Following Bleomycin

Friday, November 08, 2013 — Poster Session IV

2:00 p.m. – 4:00 p.m.

FAES Academic Center (Upper-Level Terrace)




  • PM Wang
  • WJ Martin II


Our previous study reported that eosinophils could transmigrate through muscular arterioles in murine lungs following bleomycin. Because eosinophil granular proteins can induce tissue damage, we hypothesized that eosinophil degranulation will occur during eosinophil transmigration. Female adult mice were intratracheally instilled with bleomycin (3.33 U/kg) and lungs were isolated at day 9-11 following bleomycin. Eosinophils were identified by their characteristic granules using transmission electron microscopy. We found eosinophil degranulation evidenced by free extracellular granules during transmigration of arterioles, which was accompanied by ultrastructural evidence of reduction in electron density and loss of the crystalloid cores within granules. The mean grey levels of granules for a single eosinophil, quantified using Image J, revealed a linear increase along the distance from arteriolar luminal surface to periarteriolar interstitium (ANOVA, P<0.05), suggesting the electron density of eosinophil granules decreased during degranulation. Also, average circularity values of granules within a single eosinophil increased along the transmigrated distance (ANOVA, P<0.05), i.e. the granule shape gradually changes from an elongated to a more circular shape. Our results provide direct evidence that eosinophils undergo degranulation during transmigration of arterioles during bleomycin-induced acute lung injury, suggesting that degranulation may play an important role during eosinophil arteriolar transmigration in bleomycin-injured lung.

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