Understanding the Role of Hemocytes in Wing Disc Regeneration in Drosophila melanogaster

Tissue regeneration is a complex process that activates both developmental and metabolic signaling pathways (Kashio & Miura, 2020). The wing imaginal disc in Drosophila melanogaster has been invaluable in discerning what pathways are activated during tissue regeneration, which is typically done by genetically or physically wounding the wing disc and using fluorescent markers to track different signals. However, despite its importance in other regeneration contexts (Tafesh-Edwards & Eleftherianos, 2020), immune signaling has not been well studied in this tissue. Furthermore, what we do know about tissue regeneration and immune signaling is specific to apoptotic cellular death, less is known about other types of cellular death, such as necrotic cellular death and the consequent signaling systems that result from necrosis. Drosophila have an open immune system and only possess innate immunity (Pastor-Pareja et al., 2008), making them an ideal model to study hemocyte involvement in tissue regeneration. Hemocytes are equivalent to blood cells in vertebrates, and are involved in immunological response (Kurucz et al., 2003). In this work, we observed hemocyte accumulation during injury-induced regeneration. Cellular damage was induced using a genetic ablation system known as DUAL Control, with hemipterous CA and GluR1 used to induce apoptotic and necrotic cell death respectfully. We have discovered that while hemocytes are recruited to the wing disc upon both apoptotic and necrotic injury, necrotic tissue has more hemocytes adhered than apoptotic tissue. The difference in adherence could be due to basement membrane integrity being damaged more severely in necrotic discs than apoptotic discs. Our results show that hemocytes are attracted to wing discs that have undergone necrotic damage, indicating that the immune system plays some sort of role in necrotic cellular death. Though the immune response to different types of tissue damage in Drosophila is much simpler than in vertebrate models, there are many similarities between the two, and could lead to research involving human immune signaling as it pertains to regeneration.