Bone Marrow-Derived Proangiogenic Cells Mediate Pulmonary Arteriole Stiffening via Serotonin 2B Receptor Dependent Mechanism.

Bloodworth NC, Clark CR, West JD, Snider JC, Gaskill C, Shay S, Scott C, Bastarache J, Gladson S, Moore C, D'Amico R, Brittain EL, Tanjore H, Blackwell TS, Majka SM, Merryman WD
Circ Res. 2018 123 (12): e51-e64

PMID: 30566041 · PMCID: PMC6309812 · DOI:10.1161/CIRCRESAHA.118.313397

RATIONALE - Pulmonary arterial hypertension is a deadly disease of the pulmonary vasculature for which no disease-modifying therapies exist. Small-vessel stiffening and remodeling are fundamental pathological features of pulmonary arterial hypertension that occur early and drive further endovascular cell dysfunction. Bone marrow (BM)-derived proangiogenic cells (PACs), a specialized heterogeneous subpopulation of myeloid lineage cells, are thought to play an important role in pathogenesis.

OBJECTIVE - To determine whether BM-derived PACs directly contributed to experimental pulmonary hypertension (PH) by promoting small-vessel stiffening through 5-HT (serotonin 2B receptor)-mediated signaling.

METHODS AND RESULTS - We performed BM transplants using transgenic donor animals expressing diphtheria toxin secondary to activation of an endothelial-specific tamoxifen-inducible Cre and induced experimental PH using hypoxia with SU5416 to enhance endovascular injury and ablated BM-derived PACs, after which we measured right ventricular systolic pressures in a closed-chest procedure. BM-derived PAC lineage tracing was accomplished by transplanting BM from transgenic donor animals with fluorescently labeled hematopoietic cells and treating mice with a 5-HT antagonist. BM-derived PAC ablation both prevented and reversed experimental PH with SU5416-enhanced endovascular injury, reducing the number of muscularized pulmonary arterioles and normalizing arteriole stiffness as measured by atomic force microscopy. Similarly, treatment with a pharmacological antagonist of 5-HT also prevented experimental PH, reducing the number and stiffness of muscularized pulmonary arterioles. PACs accelerated pulmonary microvascular endothelial cell injury response in vitro, and the presence of BM-derived PACs significantly correlated with stiffer pulmonary arterioles in pulmonary arterial hypertension patients and mice with experimental PH. RNA sequencing of BM-derived PACs showed that 5-HT antagonism significantly altered biologic pathways regulating cell proliferation, locomotion and migration, and cytokine production and response to cytokine stimulus.

CONCLUSIONS - Together, our findings illustrate that BM-derived PACs directly contribute to experimental PH with SU5416-enhanced endovascular injury by mediating small-vessel stiffening and remodeling in a 5-HT signaling-dependent manner.

MeSH Terms (14)

Angiogenesis Inhibitors Animals Arterioles Cell Lineage Cells, Cultured Hypertension, Pulmonary Indoles Lung Mice Mice, Inbred C57BL Myeloid Progenitor Cells Pyrroles Receptor, Serotonin, 5-HT2B Vascular Stiffness

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