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[Influence of age on mouse pulmonary alveolar macrophage clonal growth]
Y Higashimoto1, M Ohata, K Uetani
1Department of Internal Medicine, Wakayama Medical College Kihoku Hospital.
Abstract:
Although monocyte influx has been suggested as the primary source of pulmonary alveolar macrophages (AM), increasing evidence from recent studies has indicated that AM may be sustained through a self-renewal mechanism. We evaluated the age-related changes of the clonal growth (colony formation) of AM in mice (C57BL/6N mice and senescence accelerated mice). The colony forming unit (CFU) of AM of 24 month old C57BL/6N mice was lower than that of AM of 4-month-old mice (p < 0.05). In SAMP6 (senescence accelerated mice), CFU of AM was decreased with aging (p < 0.05). In SAMR1 (controls for SAMP6), CFU of AM was decreased with aging (p < 0.001). In SAMR1, CFU of bone marrow (BM) adherent cells of 12-month-old mice was similar to that of 4-month-old mice. In SAMP6, CFU of BM adherent cells of 12-month-old mice was larger than that of 4-month-old mice (P < 0.005). It was concluded that the CFU of AM declined with aging, but the CFU of the BM adherent cells did not. The decline of the AM CFU may be partly responsible for the defect of the immune response of the alveolar space in the elderly.
Insights
Pulmonary alveolar macrophages (AM) show reduced colony formation with aging in mice. This decline in AM self-renewal may contribute to age-related immune deficits in the lungs.
Area of Science:
- Immunology
- Cell Biology
- Gerontology
Context:
- Pulmonary alveolar macrophages (AM) are crucial for lung immunity.
- Traditionally, AM were thought to be replenished by monocyte influx.
- Recent evidence suggests AM possess self-renewal capabilities.
Purpose:
- To investigate age-related changes in the clonal growth of pulmonary alveolar macrophages (AM).
- To compare AM self-renewal capacity in aging C57BL/6N mice and senescence-accelerated mice (SAMP6) and their controls (SAMR1).
Summary:
- Colony-forming unit (CFU) assays revealed a significant decline in AM CFU with aging in both C57BL/6N and SAMP6 mice.
- In contrast, bone marrow (BM) adherent cell CFU remained stable or increased with age in SAMR1 and SAMP6 mice, respectively.
- These findings indicate that AM self-renewal capacity diminishes with age, unlike bone marrow progenitor cells.
Impact:
- The age-related decline in AM self-renewal may underlie impaired immune responses in the elderly lung.
- This research highlights the importance of AM intrinsic properties in maintaining lung immunity throughout life.
- Understanding AM aging mechanisms could inform strategies to bolster lung defense in older individuals.