Pericytes are organ-specific regulators of tissue morphogenesis

Blood vessels provide a versatile and adaptable transport system, but recent work has established that endothelial cells, which form the innermost lining of the vascular network, are also a source of molecular signals controlling the behavior of other cell types in the surrounding tissue. Pericytes are another essential component of the vessel wall, but comparably little is known about their signaling interactions with other cell populations during organ growth and patterning. Here, we have used tissue-specific and inducible mouse genetics, high-resolution imaging, single-cell RNA sequencing and cell culture experiments to address the function of three pericyte-derived growth factors in the postnatal development of two model organs, namely lung and brain. We found that Pdgfrb-CreERT2-controlled inactivation of the gene for hepatocyte growth factor (HGF) causes no overt alterations in the postnatal brain but impairs alveologenesis in the lung due to defective interaction with AT2 epithelial cells. Likewise, expression of brain-derived neurotrophic factor (BDNF) by pericytes is not required in the postnatal brain but controls lung development through interactions with the receptor tyrosine kinase TrkB in the pulmonary endothelium. Conversely, pericyte expression of the TGFβ family growth factor Nodal is not required for lung morphogenesis but regulates blood vessel growth and barrier function in the postnatal brain, which we attribute to signaling interactions with endothelial cells, astrocytes and microglia. Taken together, our findings establish that pericytes are a critical source of angiocrine signals that control morphogenetic processes in an organ-specific fashion.