CD90 + CD146 + identifies a pulmonary mesenchymal cell subtype with both immune modulatory and perivascular-like function in postnatal human lung.

Our understanding of mesenchymal cell subsets and their function in human lung affected by aging and in certain disease settings remains poorly described. We use a combination of flow cytometry, prospective cell-sorting strategies, confocal imaging, and modeling of microvessel formation using advanced microfluidic chip technology to characterize mesenchymal cell subtypes in human postnatal and adult lung. Tissue was obtained from patients undergoing elective surgery for congenital pulmonary airway malformations (CPAM) and other airway abnormalities including chronic obstructive pulmonary disease (COPD). In microscopically normal postnatal human lung, there was a fivefold higher mesenchymal compared with epithelial (EpCAM(+)) fraction, which diminished with age. The mesenchymal fraction composed of CD90(+) and CD90(+)CD73(+) cells was enriched in CXCL12 and platelet-derived growth factor receptor-alpha (PDGFR alpha) and located in close proximity to EpCAM(+) cells in the alveolar region. Surprisingly, alveolar organoids generated from EpCAM(+) cells supported by CD90(+) subset were immature and displayed dysplastic features. In congenital lung lesions, cystic air spaces and dysplastic alveolar regions were marked with an underlying thick interstitium composed of CD90(+) and CD90(+)PDGFR(alpha)(+) cells. In postnatal lung, a subset of CD90(+) cells coexpresses the pericyte marker CD146 and supports self-assembly of perfusable microvessels. CD90(+)CD146(+) cells from COPD patients fail to support microvessel formation due to fibrinolysis. Targeting the plasmin-plasminogen system during microvessel self-assembly prevented fibrin gel degradation, but microvessels were narrower and excessive contraction blocked perfusion. These data provide important new information regarding the immunophenotypic identity of key mesenchymal lineages and their change in a diverse setting of congenital lung lesions and COPD.