Physiologic and molecular consequences of endothelial Bmpr2 mutation

Area of Science:

• Cardiovascular Biology
• Molecular Medicine
• Genetics

Background:

• Pulmonary arterial hypertension (PAH) pathogenesis is linked to pulmonary vascular microendothelial cell (PMVEC) dysfunction.
• Hereditary PAH is predominantly associated with BMPR2 mutations, but their functional consequences in PMVECs remain unclear.

Purpose of the Study:

• To investigate the in vivo and in vitro effects of BMPR2 mutations in PMVECs.
• To elucidate the molecular mechanisms by which BMPR2 mutations contribute to PAH.

Main Methods:

• Conditional endothelial-specific expression of Bmpr2 mutations (Bmpr2delx4+, Bmpr2R899X) in adult mice.
• Phenotypic assessment including right ventricular systolic pressure (RVSP), vascular remodeling, and cellular changes (thrombosis, inflammation, apoptosis).
• BMPR2 knockdown in PMVECs using siRNA and gene expression profiling via Affymetrix arrays.

Main Results:

• Transgenic mice exhibited elevated RVSP, vascular muscularization, thrombosis, inflammation, and increased proliferation and apoptosis.
• Gene expression analysis revealed pathway alterations consistent with observed phenotypes, with distinct profiles for Bmpr2delx4+ and Bmpr2R899X mutations.
• BMPR2 mutations in PMVECs did not affect differentiation markers, unlike in smooth muscle cells.

Conclusions:

• BMPR2 mutations in PMVECs can drive PAH through multiple downstream mechanisms.
• These mechanisms include proliferation, apoptosis, inflammation, and thrombosis, potentially acting independently.
• Understanding these pathways offers insights into hereditary PAH and potential therapeutic targets.