10.3389/fimmu.2019.01640.s002 Mario Tirone Mario Tirone Anna Giovenzana Anna Giovenzana Arianna Vallone Arianna Vallone Paola Zordan Paola Zordan Martina Sormani Martina Sormani Pier Andrea Nicolosi Pier Andrea Nicolosi Raffaela Meneveri Raffaela Meneveri Carmen Rosaria Gigliotti Carmen Rosaria Gigliotti Antonello E. Spinelli Antonello E. Spinelli Renata Bocciardi Renata Bocciardi Roberto Ravazzolo Roberto Ravazzolo Ingrid Cifola Ingrid Cifola Silvia Brunelli Silvia Brunelli Image_2_Severe Heterotopic Ossification in the Skeletal Muscle and Endothelial Cells Recruitment to Chondrogenesis Are Enhanced by Monocyte/Macrophage Depletion.tif Frontiers 2019 macrophage endothelial cell (EC) heterotopic ossification (HO) EndoMT endothelial progenitors cells RNASeq and NGS data analysis micro-computerized tomography (μCT) analysis 2019-07-22 14:19:12 Figure https://frontiersin.figshare.com/articles/figure/Image_2_Severe_Heterotopic_Ossification_in_the_Skeletal_Muscle_and_Endothelial_Cells_Recruitment_to_Chondrogenesis_Are_Enhanced_by_Monocyte_Macrophage_Depletion_tif/8977133 <p>Altered macrophage infiltration upon tissue damage results in inadequate healing due to inappropriate remodeling and stem cell recruitment and differentiation. We investigated in vivo whether cells of endothelial origin phenotypically change upon heterotopic ossification induction and whether infiltration of innate immunity cells influences their commitment and alters the ectopic bone formation. Liposome-encapsulated clodronate was used to assess macrophage impact on endothelial cells in the skeletal muscle upon acute damage in the ECs specific lineage-tracing Cdh5CreER<sup>T2</sup>:R26REYFP/dtTomato transgenic mice. Macrophage depletion in the injured skeletal muscle partially shifts the fate of ECs toward endochondral differentiation. Upon ectopic stimulation of BMP signaling, monocyte depletion leads to an enhanced contribution of ECs chondrogenesis and to ectopic bone formation, with increased bone volume and density, that is reversed by ACVR1/SMAD pathway inhibitor dipyridamole. This suggests that macrophages contribute to preserve endothelial fate and to limit the bone lesion in a BMP/injury-induced mouse model of heterotopic ossification. Therefore, alterations of the macrophage-endothelial axis may represent a novel target for molecular intervention in heterotopic ossification.</p>