Remodeling of oxygen-transporting tracheoles drives intestinal regeneration and tumorigenesis

Abstract

The Drosophila tracheal system, as the functional equivalent of mammalian blood vessels, responds to hypoxia and transports oxygen throughout the body. Although the signaling pathways involved in tracheal development and the hypoxic response are well-studied, how adult tracheae interact with their target tissues is largely unknown. Here we show that the tracheae that serve the adult intestine are dynamic and respond to enteric infection, oxidative agents, and the development of gut tumors with increased terminal branching. Increased tracheation is necessary for efficient damage-induced intestinal stem cell (ISC)-mediated midgut regeneration and sufficient to drive ISC proliferation in the absence of damage. Gut damage or tumors induce Hif-1α/Sima, which, in turn, stimulates tracheole branching via the FGF(Brachless/Bnl)/FGFR(Breathless/Btl) signaling cascade. Bnl/Btl signaling is required both in the intestinal epithelium and the tracheal system for efficient damage-induced tracheal remodeling and ISC proliferation. We show that chemical or Pseudomonas-generated ROS directly affect the trachea and are necessary for branching and intestinal regeneration. Similarly, tracheole branching and the resulting increase in oxygen supply are essential for tumor growth in the midgut. Thus, we have identified a novel mechanism of visceral tracheal-intestinal tissue communication, whereby oxidative damage and tumors induce neo-tracheogenesis in adult Drosophila. This process is reminiscent of cancer-induced neo-angiogenesis in mammals.

How Gut Microbes Nurture Intestinal Stem Cells: A Drosophila Perspective

“…Specialized differentiated cells, such us antimicrobial-secreting Paneth cells, mucus-secreting goblet cells and mechanosensing tuft cells, are absent from the fly midgut lineage [27,28]. The Drosophila midgut epithelial tube is ensheathed by longitudinal and circular visceral muscle fibers involved in peristalsis, is oxygenated by visceral tracheae, and is innervated by neuronal termini at the anterior and posterior ends [21,[29][30][31][32].…”