Visualizing recruitment of immune cells to regenerating tissue in Drosophila

Immune cells are a crucial and conserved element involved in regeneration, helping clear cellular debris while secreting signaling molecules for cell proliferation and differentiation. However, relatively little is known about what role hemocytes, the immune cells of Drosophila melanogaster, play during regeneration, despite it being one of the most powerful model organisms to study this fascinating process. To understand this relationship, I used a genetic ablation system that enables the expression of two distinct, cell death-inducing factors within targeted compartments of the wing imaginal disc, a larval tissue renowned for its regenerative ability. One factor results in the regulated form of cell death known as apoptosis, while the other causes necrosis, an unregulated form of death characterized by cell lysis. Simultaneously, I visualized the accumulation of hemocytes using a hemocyte-specific fluorescent marker. I found that hemocytes are recruited to both forms of cell death but in differing numbers and at different times. In apoptotic wounds, large numbers of hemocytes can be seen at 18 and 40 hours post injury. Furthermore, recruitment of these cells is largely dependent on extracellular reactive oxygen species (ROS), a known conserved primary wound signal. In contrast, necrotic wounds appear to recruit hemocytes independently of ROS and only display large numbers of hemocytes at 40 hours. These results demonstrate that hemocytes are attracted to numerous types of wounds and likely play an important role in regeneration. I am currently undertaking experiments to modulate hemocyte activity to reveal what that role is.