Extracellular Matrix Remodeling Associated With Bleomycin-Induced Lung Injury Supports Pericyte-To-Myofibroblast Transition

Abstract

Of the many origins of pulmonary myofibroblasts, microvascular pericytes are a known source. Prior literature has established the ability of pericytes to transition into myofibroblasts, but provide limited insight into molecular cues that drive this process during lung injury repair and fibrosis. Fibronectin and RGD-binding integrins have long been considered pro-fibrotic factors in myofibroblast biology, and here we test the hypothesis that these known myofibroblast cues coordinate pericyte-to-myofibroblast transitions. Specifically, we hypothesized that v{beta}3 integrin engagement on fibronectin induces pericyte transition into myofibroblastic phenotypes in the murine bleomycin lung injury model. Myosin Heavy Chain 11 (Myh11)-CreERT2 lineage tracing in transgenic mice allows identification of cells of pericyte origin and provides a robust tool for isolating pericytes from tissues for further evaluation. We used this murine model to track and characterize pericyte behaviors during tissue repair. The majority of Myh11 lineage-positive cells are positive for the pericyte surface markers, PDGFR{beta} (55%) and CD146 (69%), and display typical pericyte morphology with spatial apposition to microvascular networks. After intratracheal bleomycin treatment of mice, Myh11 lineage-positive cells showed significantly increased contractile and secretory markers, as well as v integrin expression. According to RNASeq measurements, many disease and tissue-remodeling genesets were upregulated in Myh11 lineage-positive cells in response to bleomycin-induced lung injury. In vitro, blocking v{beta}3 binding through cyclo-RGDfK prevented expression of the myofibroblastic marker SMA relative to controls. In response to RGD-containing provisional matrix proteins present in lung injury, pericytes may alter their integrin profile. This altered matrix-integrin axis contributes to pericyte-to-myofibroblastic transition and represents a possible therapeutic target for limiting the myofibroblastic burden in lung fibrosis. HighlightsO_LIPericyte lineage model enables study of transdifferentiating pericytes C_LIO_LIHigh dimensional flow cytometry used to characterize pulmonary stromal cells C_LIO_LIPulmonary pericytes express matrix-remodeling genes and proteins in lung injury C_LIO_LIMyofibroblasts derived from pericytes have active v{beta}3 integrin C_LIO_LIIn vitro assay reveals necessity of RGD for pericyte transdifferentiation C_LI