Abstract The lack of in vivo models that can accurately replicate the complex physiological functions of the human lung hinders therapeutic development for intractable lung diseases. Current animal models are limited by inter-species differences in genetics and anatomy, while in vitro organoids cannot recapitulate the complex three-dimensional cellular interactions and the dynamic crosstalk with vascular and immune systems. To address this, we developed a novel humanized lung chimeric mouse model. We engineered immunocompromised mice to express the diphtheria toxin receptor, enabling selective ablation of alveolar type 2 (AT2) cells and lung macrophages. By administering diphtheria toxin exclusively to the left lung using a microendoscope, we successfully created an efficient niche for the engraftment and proliferation of transplanted cells. We then transplanted alveolar-differentiated human lung progenitors derived from human induced pluripotent stem cells (hiPSCs). Using non-invasive bioluminescence imaging, we confirmed their durable engraftment for at least 24 weeks. Over this period, the cells proliferated, maintained self-renewal capacity, and became structurally integrated with the host lung tissue. Single-cell RNA sequencing confirmed their differentiation into AT1 and AT2 cells with gene expression profiles comparable to those of primary human cells. The engrafted cells functionally recapitulated the roles of mature human alveolar epithelium, including secreting surfactant proteins and maintaining phosphate homeostasis via the NaPi2b transporter. Notably, the host microenvironment induced the expression of major histocompatibility complex II (MHC-II) in the transplanted cells—a feature not previously observed in hiPSC-derived AT2 cells in vitro—suggesting our model promotes physiological maturation. To validate the platform’s utility as a disease model, we performed similar transplantations using hiPSCs with mutations in SLC34A2, the causative gene for pulmonary alveolar microlithiasis (PAM). We successfully recapitulated the in vivo formation of calcium phosphate microliths, a hallmark of the disease. This was a critical distinction, as microliths did not form spontaneously in our in vitro system, likely due to the inability to model a slow, progressive disease in a culture requiring regular media changes. In conclusion, the chimeric lung model established in this study is an unparalleled and potent platform that replicates the intricate structure, function, and metabolism of human alveolar epithelium in vivo over an extended period. This system enables a broad range of applications, from basic lung biology research to the evaluation of new therapies, accelerating future advances in respiratory medicine by serving as a critical bridge between experimental models and first-in-human clinical trials. This abstract is funded by: None
Yamagata et al. (Fri,) studied this question.