GLI1+ Cells Contribute to Vascular Remodeling in Pulmonary Hypertension

BACKGROUND: The precise origin of newly formed ACTA2+ (alpha smooth muscle actin-positive) cells appearing in nonmuscularized vessels in the context of pulmonary hypertension is still debatable although it is believed that they predominantly derive from preexisting vascular smooth muscle cells (VSMCs). METHODS: Gli1(Cre-ERT2); tdTomato(flox) mice were used to lineage trace GLI1+ (glioma-associated oncogene homolog 1-positive) cells in the context of pulmonary hypertension using 2 independent models of vascular remodeling and reverse remodeling: hypoxia and cigarette smoke exposure. Hemodynamic measurements, right ventricular hypertrophy assessment, flow cytometry, and histological analysis of thick lung sections followed by state-of-the-art 3-dimensional reconstruction and quantification using Imaris software were used to investigate the contribution of GLI1+ cells to neomuscularization of the pulmonary vasculature. RESULTS: The data show that GLI1+ cells are abundant around distal, nonmuscularized vessels during steady state, and this lineage contributes to around 50% of newly formed ACTA2+ cells around these normally nonmuscularized vessels. During reverse remodeling, cells derived from the GLI1+ lineage are largely cleared in parallel to the reversal of muscularization. Partial ablation of GLI1+ cells greatly prevented vascular remodeling in response to hypoxia and attenuated the increase in right ventricular systolic pressure and right heart hypertrophy. Single-cell RNA sequencing on sorted lineage-labeled GLI1+ cells revealed an Acta2(high) fraction of cells with pathways in cancer and MAPK signaling as potential players in reprogramming these cells during vascular remodeling. Analysis of human lung-derived material suggests that GLI1 signaling is overactivated in both group 1 and group 3 pulmonary hypertension and can promote proliferation and myogenic differentiation. CONCLUSIONS: Our data highlight GLI1+ cells as an alternative cellular source of VSMCs in pulmonary hypertension and suggest that these cells and the associated signaling pathways represent an important therapeutic target for further studies.

• Chu, X.
• Kheirollahi, V.
• Lingampally, A.
• Chelladurai, P.
• Valasarajan, C.
• Vazquez-Armendariz, A. I.
• Hadzic, S.
• Khadim, A.
• Pak, O.
• Rivetti, S.
• Wilhelm, J.
• Bartkuhn, M.
• Crnkovic, S.
• Moiseenko, A.
• Heiner, M.
• Kraut, S.
• Sotoodeh, L.
• Koepke, J.
• Valente, G.
• Ruppert, C.
• Braun, T.
• Samakovlis, C.
• Alexopoulos, I.
• Looso, M.
• Chao, C. M.
• Herold, S.
• Seeger, W.
• Kwapiszewska, G.
• Huang, X.
• Zhang, J. S.
• Pullamsetti, S. S.
• Weissmann, N.
• Li, X.
• El Agha, E.
• Bellusci, S.