Alveolar fibrosis and changes in equine lung morphometry in response to intrapulmonary blood.
Abstract: Necropsy studies of horses suffering exercise-induced pulmonary haemorrhage (EIPH) have identified mild inflammatory lesions with evidence of alveolar fibrosis and bronchiolitis. These lesions were thought to be the result of viral infections that predisposed the affected regions of the lung to EIPH. We have shown previously that during erythrophagocytosis in the alveolar space, there is a prolonged period of macrophage influx and activation. This present study used morphometric analysis to quantify the effects of macrophage activity during erythrophagocytosis, on the alveolar cell population and physical structure of the alveolar walls. Segments of the bronchial tree were inoculated with either autologous whole blood or serum, at 15, 8, 3 days, 24 h and 30 min prior to euthanasia. Blood inoculation produced many significant changes in the alveolar morphometry including, increased numbers of alveolar macrophages, increased septal thickness, and a markedly increased percentage of collagen in the alveolar walls. Signs of chronic inflammation including increased macrophage activity and erythrophagocytosis coincided with increased alveolar macrophage numbers (10,688 +/- 1708 cells/mm3 to 30,957 +/- 6831 cells/mm3), septal thickness (4.1 +/- 0.4 microm to 6.1 +/- 0.5 microm) and alveolar septal collagen content (6.6 +/- 0.5% to 27.5 +/- 3.3%). The results suggest that intrapulmonary blood induces a macrophage dominated inflammatory response, septal thickening and the development of alveolar fibrosis. These changes are the probable cause of the observed alveolar fibrosis and bronchiolitis that was once suspected to be the originating cause of EIPH.
Publication Date: 2002-10-31 PubMed ID: 12405733DOI: 10.1111/j.2042-3306.2002.tb05465.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research explores the effect of blood present in the lungs’ alveolar spaces in horses, leading to inflammation, thickening of the alveolar walls, and fibrosis. The study solidifies the connection between intrapulmonary blood and the development of exercise-induced pulmonary haemorrhage (EIPH).
Research Context and Objectives
- The research was carried out to understand the impact of erythrophagocytosis (a process where red blood cells are consumed by macrophages) on the lungs of horses, mainly focusing on horse exercise-induced pulmonary haemorrhage (EIPH).
- Necropsy studies on EIPH horses indicated alveolar fibrosis and bronchiolitis, earlier attributed to viral infections. The researchers, however, posit that intrapulmonary blood may play a critical role in causing these conditions.
Methodology
- Researchers studied the effects of macrophage activity (defense cells in the body which engulf harmful bacteria) during erythrophagocytosis on alveolar cells and their wall structure. Morphometric analysis, which allows for quantifying effects, was utilized to this end.
- The bronchial tree segments were injected with autologous whole blood or serum before euthanasia to mimic intrapulmonary bleeding.
- The various time intervals at which the injections were made included 15, 8, 3 days, 24 hours, and 30 minutes ahead of euthanasia.
Key Findings
- The study found significant changes in alveolar morphometry due to blood injections which primarily included an increased count of alveolar macrophages, heightened septal thickness, and a significant rise in the alveolar wall collagen percentage.
- It was seen that signs of chronic inflammation, an increase in macrophage activity, and erythrophagocytosis were directly associated with elevated alveolar macrophage numbers, septal thickness, and collagen content in the alveolar septa.
Conclusions
- The study indicates that intrapulmonary blood could initiate an inflammatory response mainly led by macrophages, resulting in septal thickening and eventual development of alveolar fibrosis.
- These changes are likely to cause the alveolar fibrosis and bronchiolitis observed in some horses rather than their being precursors to EIPH.
Cite This Article
APA
McKane SA, Slocombe RF.
(2002).
Alveolar fibrosis and changes in equine lung morphometry in response to intrapulmonary blood.
Equine Vet J Suppl(34), 451-458.
https://doi.org/10.1111/j.2042-3306.2002.tb05465.x Publication
Researcher Affiliations
- University of Melbourne, Werribee, Victoria, Australia.
MeSH Terms
- Animals
- Bronchiolitis / etiology
- Bronchiolitis / pathology
- Bronchiolitis / veterinary
- Collagen / metabolism
- Erythrocytes / immunology
- Hemorrhage / etiology
- Hemorrhage / pathology
- Hemorrhage / veterinary
- Horse Diseases / etiology
- Horse Diseases / pathology
- Horses
- Macrophages, Alveolar / immunology
- Macrophages, Alveolar / physiology
- Phagocytosis
- Pulmonary Alveoli / pathology
- Pulmonary Fibrosis / etiology
- Pulmonary Fibrosis / pathology
- Pulmonary Fibrosis / veterinary
Citations
This article has been cited 3 times.- Bayly W, Lopez C, Sides R, Bergsma G, Bergsma J, Gold J, Sellon D. Effect of different protocols on the mitigation of exercise-induced pulmonary hemorrhage in horses when administered 24 hours before strenuous exercise.. J Vet Intern Med 2019 Sep;33(5):2319-2326.
- Hinchcliff KW, Couetil LL, Knight PK, Morley PS, Robinson NE, Sweeney CR, van Erck E. Exercise induced pulmonary hemorrhage in horses: American College of Veterinary Internal Medicine consensus statement.. J Vet Intern Med 2015 May-Jun;29(3):743-58.
- Perez-Moreno CI, Couëtil LL, Pratt SM, Ochoa-Acuña HG, Raskin RE, Russell MA. Effect of furosemide and furosemide-carbazochrome combination on exercise-induced pulmonary hemorrhage in Standardbred racehorses.. Can Vet J 2009 Aug;50(8):821-7.
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