Meeting Abstract
Adult mammals generally heal wounds by forming scar tissue. Howvever, African spiny mice (Acomys spp.) can undergo tissue regeneration to heal hair follicles, sebaceous glands, dermis and cartilage in lieu of fibrosis. It is not known why these mammals can regenerate while others cannot, but studies in non-mammalian vertebrate systems suggest regeneration is associated with reduced pro-inflammatory and cellular immune responses. In this study, we used a comparative approach to evaluate the quantity and efficacy of cellular and humoral innate immune responses in regenerating (Acomys cahirinus) and non-regenerating mice (Mus musculus). We evaluated the number and functionality of neutrophils, key inflammatory cells of innate immunity, and found that while A. cahirinus exhibited lower neutrophil numbers than M. musculus in the blood, both species contained equal neutrophil numbers in the bone marrow. We also observed that A. cahirinus neutrophils contained significantly less myeloperoxidase, required for producing reactive oxygen species, and exhibited increased phagocytosis compared to M. musculus neutrophils. Finally, we assessed the in vitro Escherichia coli killing abilities of neutrophils, serum, and whole blood from both species. We found that while neutrophils and whole blood from both species exhibited similar bacterial killing, the serum of A. cahirinus was significantly more effective at destroying E. coli than that of M. musculus. Collectively, these results indicate marked differences in neutrophil number and function between animals with differing regenerative capacities. They also suggest regenerating mice may depend more on serum defenses than cellular ones to control bacterial infection and that regenerating rodent serum may inhibit the bacterial killing ability of cells.
