Macrophage-derived PDGF-B induces muscularization in murine and human pulmonary hypertension
Aglaia Ntokou, … , W. Mark Saltzman, Daniel M. Greif
Aglaia Ntokou, … , W. Mark Saltzman, Daniel M. Greif
Published February 16, 2021
Citation Information: JCI Insight. 2021;6(6):e139067. https://doi.org/10.1172/jci.insight.139067.
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Research Article Pulmonology Vascular biology

Macrophage-derived PDGF-B induces muscularization in murine and human pulmonary hypertension

Abstract

Excess macrophages and smooth muscle cells (SMCs) characterize many cardiovascular diseases, but crosstalk between these cell types is poorly defined. Pulmonary hypertension (PH) is a lethal disease in which lung arteriole SMCs proliferate and migrate, coating the normally unmuscularized distal arteriole. We hypothesized that increased macrophage platelet-derived growth factor–B (PDGF-B) induces pathological SMC burden in PH. Our results indicate that clodronate attenuates hypoxia-induced macrophage accumulation, distal muscularization, PH, and right ventricle hypertrophy (RVH). With hypoxia exposure, macrophage Pdgfb mRNA was upregulated in mice, and LysM‑Cre mice carrying floxed alleles for hypoxia-inducible factor 1a, hypoxia-inducible factor 2a, or Pdgfb had reduced macrophage Pdgfb and were protected against distal muscularization and PH. Conversely, LysM‑Cre von-Hippel Lindaufl/fl mice had increased macrophage Hifa and Pdgfb and developed distal muscularization, PH, and RVH in normoxia. Similarly, Pdgfb was upregulated in macrophages from human idiopathic or systemic sclerosis–induced pulmonary arterial hypertension patients, and macrophage-conditioned medium from these patients increased SMC proliferation and migration via PDGF-B. Finally, in mice, orotracheal administration of nanoparticles loaded with Pdgfb siRNA specifically reduced lung macrophage Pdgfb and prevented hypoxia-induced distal muscularization, PH, and RVH. Thus, macrophage-derived PDGF-B is critical for pathological SMC expansion in PH, and nanoparticle-mediated inhibition of lung macrophage PDGF-B has profound implications as an interventional strategy for PH.

Authors

Aglaia Ntokou, Jui M. Dave, Amy C. Kauffman, Maor Sauler, Changwan Ryu, John Hwa, Erica L. Herzog, Inderjit Singh, W. Mark Saltzman, Daniel M. Greif

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Figure 4

Hif1a deletion in myeloid cells attenuates hypoxia-induced Pdgfb expression, distal muscularization, and PH.

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Hif1a deletion in myeloid cells attenuates hypoxia-induced Pdgfb expres...
(A and B) BALF cells were isolated from normoxic or hypoxic (10% FiO2 up to 21 days) WT mice. HIF1-α and β-actin protein were assessed by Western blot (A) with densitometry of HIF1-α relative to β-actin (B). n = 3 mice per time point. (C–I) Hif1afl/fl mice also carrying no Cre or LysM-Cre were exposed to hypoxia for 3 or 21 days. At hypoxia day 3, Pdgfb transcript levels of BALF cells were determined by qRT-PCR (C). Lung vibratome sections were stained for SMA, macrophage marker CD64, and nuclei (DAPI) with arterioles indicated by “a” and boxed regions shown as close-ups below (D). The numbers of macrophages (asterisks) and alveolar myofibroblasts (arrowhead) were quantified per 100 alveoli (D–F). n = 3–5 mice; qRT-PCR was done in triplicate. More than 700 alveoli were quantified per mouse. At hypoxia day 21, vibratome sections with distal arterioles in the L.L1.A1.L1 area were stained for SMA and CD31 (G), and RVSP and the Fulton index were measured as shown (H and I). n = 3 mice. One-way ANOVA with Tukey’s multiple-comparison test was used in B, H, and I (* vs. normoxia, P < 0.05), and Student’s t test was used in C, E, and F. Scale bars: 25 μm.