Study objectives: The diagnosis of alveolar hemorrhage
is assisted by the presence of hemosiderin-laden macrophages (HLMs) in
the BAL fluid or lung tissue. Despite the importance of this diagnostic
method in clinical settings, limited information is available on the
formation and clearance of HLMs as a function of time. The objectives
of this study are to determine the time course of HLMs within the BAL
and lung tissue, and to evaluate the effect of a single blood
aspiration on the recruitment of inflammatory cells within the
Design: Under light anesthesia,
Balb/c mice received a single intranasal instillation of
species-specific blood (50 μL). Control animals received heparinized
sterile saline solution in a similar manner. At several time points
after blood aspiration, BAL was recovered for cell differentials and
determination of HLMs. The time course for HLMs was also established in
the lung tissue.
Results: Hemosiderin staining within
alveolar macrophages was first detected in the BAL and lung tissue at
day 3, peaked at day 7, and persisted through 2 months. The analysis of
the BAL revealed an increased number of total cells, with an acute
inflammatory reaction that resolved within 2 weeks.
Conclusions: Our findings demonstrate the validity of this
model for the study of HLM production after blood aspiration.
Additional work using animal models of lung hemorrhage is needed to
further characterize the cellular events leading to clearance of
erythrocytes within the lung.