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A2401 - Alveolar Macrophage Proliferation Is Increased in Chronic Cigarette Smokers
Author Block: N. Shetty1, M. O. Aksoy2, M. Barbe3, M. R. Wolfson4, S. G. Kelsen5; 1Thoracic Medicine and Surgery, Temple University Hospital, Philadelphia, PA, United States, 2Medicine, Temple University School of Medicine, Philadelphia, PA, United States, 3Anatomy and Cell Biology, Temple University Hospital, Philadelphia, PA, United States, 4Physiology, Lewis Katz School of Medicine at Temple University, Philadelphia, PA, United States, 5Temple Univ Sch of Med, Philadelphia, PA, United States.
Rationale: Chronic cigarette smoking increases lung alveolar macrophage (AM) number, and affects macrophage gene expression and functional response. However, little is known about the source of the increased macrophage numbers. In particular, it is not known whether the increase in alveolar macrophage cell number is due to proliferation or to increased migration of monocyte - derived macrophages from the lung interstitium. Using a well-accepted marker of cell proliferation, expression of ki67 assessed by immunofluorescence microscopy, we assessed the effects of chronic cigarette smoking on alveolar macrophage proliferation in human lung tissue. Specifically, the number of proliferating (ki67+) macrophages was assessed in inflated, formalin-fixed lungs obtained from smoking [S] and never-smoking subjects [NS]. Methods: Serial 5 µm thick, paraffin-embedded lung tissue sections were stained for the proliferation marker ki67 using the red fluorescent label (Alexa fluor 647) conjugated to a monoclonal ki67 antibody (Abcam). Alveolar macrophages were identified by morphology in the bright field channel and counted for total number. The ki67 signal was captured in the red channel by a Nikon E800 camera and microscope system to minimize autofluorescence. Ki67 positive macrophages in the alveolar space were counted in 10 random fields and the percentage of positive cells was used to determine the proliferation rate. Results: Alveolar macrophage number was greater in S (83 ± 8 SEM) than in NS (29 ± 3 SEM). Proliferation rate was greater in S (54 ± 3% SEM) than NS (5 ± 5% SEM). Discussion: This study showed that chronic cigarette smoking increases alveolar macrophage proliferation which may account for the increase in macrophage number. Proliferation of long-lived resident AM's could contribute to the pathogenesis of lung disease in chronic smokers.