The human respiratory epithelium is derived from a progenitor cell in the distal buds of the developing lung. These “bud tip progenitors” are regulated by reciprocal signaling with surrounding mesenchyme; however, mesenchymal heterogeneity and function in the developing human lung are poorly understood. We interrogated single-cell RNA sequencing data from multiple human lung specimens and identified a mesenchymal cell population present during development that is highly enriched for expression of the WNT agonist RSPO2, and we found that the adjacent bud tip progenitors are enriched for the RSPO2 receptor LGR5. Functional experiments using organoid models, explant cultures, and FACS-isolated RSPO2⁺ mesenchyme show that RSPO2 is a critical niche cue that potentiates WNT signaling in bud tip progenitors to support their maintenance and multipotency.

人类呼吸道上皮源自发育中的肺远端芽中的祖细胞。这些“芽尖祖细胞”受到与周围间质的相互信号调节；然而，人们对发育中的人肺的间充质异质性和功能知之甚少。我们询问了来自多个人肺样本的单细胞 RNA 测序数据，并鉴定了发育过程中存在的间充质细胞群，该细胞群高度富集 WNT 激动剂 RSPO2 的表达，并且我们发现相邻的芽尖祖细胞富含 RSPO2 受体 LGR5 。使用类器官模型、外植体培养物和 FACS 分离的 RSPO2 ⁺间充质的功能实验表明，RSPO2 是一个关键的生态位线索，可增强芽尖祖细胞中的 WNT 信号传导，以支持其维持和多能性。