| Summary: | Pulmonary arterial hypertension (PAH) is a lethal disease characterized by excessive
proliferation of pulmonary vascular cells, such as endothelial cells (ECs). Hereditary (H)
PAH is mainly caused by ―loss-of-function‖ mutations in the gene coding for the bone
morphogenetic protein type II receptor (BMPR2). However, the mechanisms by which
these mutations cause PAH remain unclear. The hypothesis of this thesis was that
BMPR2 mutations produce an imbalance in EC protein expression and/or activity that is
integrally related to the development of abnormalities in lung vascular function and
structure in HPAH. Patient-specific blood-outgrowth endothelial cells (BOECs) expanded
ex vivo from peripheral blood mononuclear cells from patients with HPAH and healthy
subjects were used to examine the consequences of BMPR2 mutations on the BOEC
protein expression profile as well as on their functionality. Functional analyses of the
BOECs revealed that HPAH-derived BOECs are more susceptible to apoptosis and
more proliferative compared with healthy controls. Protein isolates of BOECs from
patients with HPAH and from healthy subjects were subjected to 2-D gel electrophoresis
and stained for total proteins and phosphoproteins, and to a quantitative computerassisted
analysis. Differentially regulated proteins were identified by mass spectrometry
(LC-MS/MS). Of the 416 total proteins detected under basal conditions, 11 were
significantly downregulated in HPAH-derived BOECs and 11, including the translationally
controlled tumor protein (TCTP), were upregulated. TCTP has previously been shown to
be involved in systemic arteriolar remodeling, inflammation and growth. Therefore, the
potential role of TCTP in PAH was studied in vivo in the SU5416 rat model of severe
angioproliferative PAH. Immunofluorescence staining revealed high expression of TCTP
in arteriolar ECs of PAH lungs tightly localized to proliferating cells within occlusive
intimal lesions; whereas, only minimal TCTP expression was seen in vascular ECs of normal lungs. Similarly, abundant TCTP immunostaining was also seen in human PAH
lung sections, again associated with complex vascular lesions. In BOECs, TCTP was
found to participate in cell growth and survival. These data suggest that TCTP could play
an important role in PAH by mediating pro-survival and growth signaling in vascular cells,
contributing to occlusive pulmonary vascular remodeling triggered by EC apoptosis.
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