Abstract The lung, as the primary respiratory organ, possesses a distinctive capillary-alveolar structure that supports efficient gas exchange and is the most highly vascularized organ in the body, with endothelial cells (ECs) comprising nearly half of all lung cells. Recent advances in single-cell and spatial omics have identified two major capillary EC subpopulations—specialized aerocytes and general capillaries. Aerocytes, which encircle the alveolar epithelium, are crucial for gas exchange; however, their regulatory role as a niche population for alveolar epithelial regeneration remains poorly understood. We hypothesized that aerocytes are critical regulators of alveolar epithelial regeneration after lung injury and sought to define the underlying signaling mechanisms. Single-cell RNA sequencing (scRNA-seq), proteomics, and RNA-Scope were used to identify key angiocrine factors produced by aerocytes. Loss-of-function and gain-of-function approaches in mouse models were employed to determine the role of aerocyte-derived R-spondin3 in alveolar epithelial regeneration following lung injury, with a particular focus on regenerative alveolar remodeling (AT2 → transitional stem cell TSC → AT1). We identified R-spondin3, an angiocrine factor known to activate Wnt signaling and act as a stem cell factor, as being specifically produced by aerocytes. Loss of angiocrine R-spondin3 impaired alveolar epithelial repair after lung injury and disrupted regenerative alveolar remodeling. These findings demonstrate that aerocyte-derived R-spondin3 is essential for directing epithelial repair and regenerative alveolar remodeling after lung injury, playing a key role in AT2 cell renewal, their transition to TSCs, and subsequent differentiation into AT1 cells. This research was supported by NIH/NHLBI R01HL176717 and R01HL169447 (to B.Z.). This abstract is funded by: NHLBI
Zhou et al. (Fri,) studied this question.