J Vet Sci.  2017 Mar;18(1):17-23. 10.4142/jvs.2017.18.1.17.

Expression of von Willebrand factor, pulmonary intravascular macrophages, and Toll-like receptors in lungs of septic foals

• Harrison J
• Quanstrom
• Robinson A
• Wobeser B
• Anderson S
• Singh B

• KMID: 2412583
• DOI: http://doi.org/10.4142/jvs.2017.18.1.17

Abstract

Sepsis causes significant mortality in neonatal foals; however, there is little data describing the cellular and molecular pathways of lung inflammation in septic foals. This study was conducted to characterize lung inflammation in septic foals. Lung tissue sections from control (n = 6) and septic (n = 17) foals were compared using histology and immunohistology. Blinded pathologic scoring of hematoxylin and eosin stained samples revealed increased features of lung inflammation such as thickened alveolar septa and sequestered inflammatory cells in septic foals. Septic foal lungs showed increased expression of von Willebrand factor in blood vessels, demonstrating vascular inflammation. Use of MAC387 antibody to detect calprotectin as a reflection of mononuclear cell infiltration revealed a significant increase in their numbers in alveolar septa of lungs from septic foals compared to those from control foals. The mononuclear cells appeared to be mature macrophages and were located in the septal capillaries, suggesting they were pulmonary intravascular macrophages (PIMs). Finally, lungs from septic foals showed increased expression of Toll-like receptor 4 and 9 in mononuclear cells relative to the control. Taken together, this study is the first to show the expression of inflammatory molecules and an increase in PIMs in lungs from foals that died from sepsis.

Keyword

Toll-like receptor 4 and 9; horses; immunohistochemistry; pulmonary intravascular macrophage; von Willebrand factor

MeSH Terms

Animals
*Gene Expression
Horse Diseases/*genetics/immunology/microbiology
Horses
Inflammation/genetics/immunology/microbiology/*veterinary
Lung/metabolism
Macrophages, Alveolar/*metabolism
Sepsis/genetics/immunology/microbiology/*veterinary
Toll-Like Receptors/*genetics/metabolism
von Willebrand Factor/*genetics/metabolism
Toll-Like Receptors
von Willebrand Factor

Figure

• 

  Fig. 1 Histology of hematoxylin and eosin stained lung sections from control (A and C) and septic (B and D) foals. Lung section from the control foal (A) shows normal lung morphology of bronchiole (†), blood vessels (BV), and alveolar space (*) compared to increased septal thickness and cellularity (arrows) in the lung section from the septic foal (B). Lung section from the control foal (C) shows normal alveolar septal width (double headed arrow) compared to the thickened septa of the septic foal lung section (D). Scale bars = 200 µm (A and B), 20 µm (C), 10 µm (D).

• 

  Fig. 2 Histologic lung sections from control (A and C) and septic (B and D) foals. Von Willebrand factor (vWF) staining (arrows) was present in the endothelium of large blood vessel (BV), but was minimal in alveolar septa (S) in sections from the control foal lung (A and C). The sections from septic foals show increased staining for vWF in alveolar septa and the endothelium in large BVs (B and D). The septic foals (B) also showed an increase in positive vWF staining on mononuclear cells (arrowheads) compared to normal foal lungs. *Alveolar space. †Bronchiole. Scale bars = 100 µm (A and B), 50 µm (C and D).

• 

  Fig. 3 Histologic lung sections from control (A and C) and septic (B and D) foals with MAC387 staining. Mononuclear cell (arrowheads) infiltration increased in septic (B and D) vs. control (A and C) foals. The inset image in figure d shows macrophage-like cells within the vasculature of the alveolar septa (S), suggesting the presence of a pulmonary intravascular macrophages. BV, blood vessel; En, endothelial cell; L, lumen; M, macrophage. *Alveolar space. †Bronchiole. Scale bars = 200 µm (A and B), 50 µm (C and D).

• 

  Fig. 4 Histologic lung sections from control (A and C) and septic (B and D) foals. Septic foals (B and D) showed an increase in TLR4 staining (arrowheads) on mononuclear cells, but a slight decrease along bronchiole (†) epithelium, blood vessel (BV) endothelium, and alveolar septa (S). *Alveolar space. Scale bars = 100 µm (A and B), 50 µm (C and D).

• 

  Fig. 5 Histologic lung sections from control (A and C) and septic (B and D) foals. Septic foals showed an increase in TLR9 staining (arrowheads) on mononuclear cells, but a slight decrease along bronchiole (†) epithelium, blood vessel (BV) endothelium, and alveolar septa (S). *Alveolar space. Scale bars = 100 µm (A and B), 50 µm (C and D).

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