A novel in vitro macrophage senescence model to study macrophaging

Resumen

Macrophages play a key role in the immune response destroying pathogens directly or releasing mediators which can activate other cells. However, macrophages from aged mice present defects in their functional activities due to the aging process that alter the immune response. Cellular senescence is characterized by a permanent cell cycle arrest and is produced after continuous duplication/reproduction of a cell. The accumulation of senescent cells seems to be involved in and is responsible for the induction of aging. In this regard, due to the difficulty of working with old mice as a source of aged macrophages, in the present study we have considered whether the functions of long-lasting cultures of macrophages from young mice resembles to the functions found in senescent cells responsible for the aging patterns previously described. For this purpose, we have compared a normal macrophage culture (0 days macrophages) and long-period macrophage culture (14 days macrophages) of bone-marrow derived macrophages from 6-weeks old Balb/c mice. Macrophages from 14 days cultures were positive for senescence markers such as telomere shortening and high β-galactosidase activity. Macrophage senescence was correlated with a reduced proliferation in response to specific growth factors (M-CSF and GM-CSF) due to an increase of cells in G1 phase of the cell cycle. In addition, long-lasting macrophage cultures showed a great number of altered macrophage functions such as antigen presentation and microbicidal reduced capacities and defects in alternative activation, indicating that both pro-inflammatory and anti-inflammatory phenotypes were impaired in these cells which correlate with that observed in macrophages from aged mice, as it was previously demonstrated in our laboratory. All these data suggest that cellular senescence induced in long-lasting macrophage cultures is a good tool to evaluate the altered macrophage functions and characteristics during the aging process.