Von Hippel-Lindau protein is required for optimal alveolar macrophage terminal differentiation, self-renewal and function.

The rapid transit from hypoxia to normoxia in the lung that follows the first breath in newborn mice coincides with alveolar macrophage (AM) differentiation. However, whether sensing of oxygen affects AM maturation and function has not been previously explored. We have generated mice whose AMs show a deficient ability to sense oxygen after birth by deleting Vhl, a negative regulator of HIF transcription factors, in the CD11c compartment (CD11c∆Vhl mice). VHL-deficient AMs show an immature-like phenotype and an impaired self-renewal capacity in vivo that persists upon culture ex vivo. VHL-deficient phenotype is intrinsic in AMs derived from monocyte precursors in mixed bone marrow chimeras. Moreover, unlike control Vhlfl/fl, AMs from CD11c∆Vhl mice do not revert pulmonary alveolar proteinosis when transplanted into Csf2rb-/- mice, demonstrating that VHL contributes to AM-mediated surfactant clearance. Thus, our results suggest that optimal AM terminal differentiation, self-renewal, and homeostatic function requires their oxygen sensing capacity. BAL AMs were pooled from 5-7 age and sex-matched mice per genotype and further purified by positive selection with anti-CD11c-microbeads (Miltenyi Biotec), following manufacturer’s instructions. Cell lysis was performed with buffer RLT (Qiagen), containing 10µ/ml β-mercaptoethanol and RNA was isolated with RNeasy Plus Mini Kit (Qiagen). RNA concentration and integrity were determined with an Agilent 2100 Bioanalyzer (Caliper Life Science). Samples with RNA integrity values > 8 were further processed. A total of 3 pools per genotype were used for RNA Seq.