Disruption of lineage specification in adult pulmonary mesenchymal progenitor cells promotes microvascular dysfunction
Christa F. Gaskill, … , Dwight J. Klemm, Susan M. Majka
Christa F. Gaskill, … , Dwight J. Klemm, Susan M. Majka
Published May 2, 2017
Citation Information: J Clin Invest. 2017;127(6):2262-2276. https://doi.org/10.1172/JCI88629.
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Disruption of lineage specification in adult pulmonary mesenchymal progenitor cells promotes microvascular dysfunction

Abstract

Pulmonary vascular disease is characterized by remodeling and loss of microvessels and is typically attributed to pathological responses in vascular endothelium or abnormal smooth muscle cell phenotypes. We have challenged this understanding by defining an adult pulmonary mesenchymal progenitor cell (MPC) that regulates both microvascular function and angiogenesis. The current understanding of adult MPCs and their roles in homeostasis versus disease has been limited by a lack of genetic markers with which to lineage label multipotent mesenchyme and trace the differentiation of these MPCs into vascular lineages. Here, we have shown that lineage-labeled lung MPCs expressing the ATP-binding cassette protein ABCG2 (ABCG2+) are pericyte progenitors that participate in microvascular homeostasis as well as adaptive angiogenesis. Activation of Wnt/β-catenin signaling, either autonomously or downstream of decreased BMP receptor signaling, enhanced ABCG2+ MPC proliferation but suppressed MPC differentiation into a functional pericyte lineage. Thus, enhanced Wnt/β-catenin signaling in ABCG2+ MPCs drives a phenotype of persistent microvascular dysfunction, abnormal angiogenesis, and subsequent exacerbation of bleomycin-induced fibrosis. ABCG2+ MPCs may, therefore, account in part for the aberrant microvessel function and remodeling that are associated with chronic lung diseases.

Authors

Christa F. Gaskill, Erica J. Carrier, Jonathan A. Kropski, Nathaniel C. Bloodworth, Swapna Menon, Robert F. Foronjy, M. Mark Taketo, Charles C. Hong, Eric D. Austin, James D. West, Anna L. Means, James E. Loyd, W. David Merryman, Anna R. Hemnes, Stijn De Langhe, Timothy S. Blackwell, Dwight J. Klemm, Susan M. Majka

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Figure 1

Abnormal pericyte lineage specification and microvascular dysfunction accompanied by loss of distal lung tissue structure in vivo via deregulation of BMPR2 and Wnt/β-catenin signaling in lung MPCs.

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Abnormal pericyte lineage specification and microvascular dysfunction ac...
(A) Schematic time line of mouse modeling. WT, Bmpr2fl/+, and βOE mice were induced with i.p. tamoxifen (0.5 mg total). (B) Two weeks after induction, eGFP labeling and enumeration of ABCG2+ lung MPCs were confirmed by flow cytometry (n = 3–6). Numbers in parentheses represent SEM. (C) Three weeks after induction, pulmonary vascular leak was quantitated. Representative images of mice obtained with the Pearl analyzer. Bar graph shows the ratio calculated for each animal, comparing the intensity of dye in the lung (red squares) with the baseline fluorescence in the nose (red circles) (n = 7–15). (D–F) Additional mice were sacrificed and the lungs agarose inflated using constant pressure to obtain lung tissue for immunofluorescence analyses. Immunostaining for detection of eGFP (green) MPCs and derivatives as well as α-SMA (red) was performed (n = 4). (G) Eighteen to twenty weeks after tamoxifen induction, RVSP was measured (n = 10–13). Immunostaining was performed on lung tissue sections to detect (H) F8+ microvessels and (I) α-SMA+ muscularized vessels. (J) The ratio of α-SMA/total microvessels was also calculated, and the positive numbers were counted per FOV. Six to eight sections of twenty FOV per section were evaluated (n = 4). (K) MLI was calculated to evaluate the loss of distal lung tissue structure (n = 6). (L–N) Immunofluorescent staining (IFC) to detect α-SMA demonstrated a decrease in α-SMA overall in Bmpr2fl/+ and βOE lungs. (L–T) Immunostaining was performed to detect ABCG2+ MPCs and derived eGFP- and α-SMA–expressing cells. Scale bars: 50 μm (L–T) and 100 μm (D–F). Data are presented as the mean ± SEM. *P < 0.05 and **P < 0.01, by 1-way ANOVA followed by Tukey’s honest significant difference (HSD) post-hoc test.