Targeted alveolar regeneration with Frizzled-specific agonists

Wnt ligands oligomerize Frizzled (Fzd) and Lrp5/6 receptors to control the specification and activity of stem cells in many species. How Wnt is selectively activated in different stem cell populations, often within the same organ, is not understood. In lung alveoli, wherein Wnt-dependent epithelial and stromal progenitors are intermingled, we show that distinct Wnt receptors are expressed by epithelial (Fzd5/6), endothelial (Fzd4), and stromal (Fzd1) cells. Moreover, Fzd5 was uniquely required for alveolar epithelial stem cell activity. However, by developing an expanded repertoire of Fzd-Lrp agonists (FLAgs), we could activate canonical Wnt signaling in alveolar epithelial stem cells via either Fzd5 or, unexpectedly, non-canonical Fzd6. Fzd5 and Fzd6 FLAgs stimulated supra-physiological alveolar epithelial stem cell activity in mice following lung injury, but only Fzd6 FLAg promoted an alveolar fate in airway-derived progenitors. Therefore, we identify a potential strategy for promoting regeneration without exacerbating fibrosis during lung injury. Overall design: Cells grown with Wnt agonist CHIR99201 (LGK_CHIR99201) for 19 days and then Wnt is withdrawn for 24 hours (24hourwithdrawal) and 48 hours (48hourwithdrawal). We also withdrew CHIR99201 and replaced it with Wnt (LGK974_WNT), Fzd5 agonist (LGK974_FZD5_Agonist) and Fzd6 agonist (LGK974_FZD6_Agonist).