Cross Talk Between Endothelial and Smooth Muscle Cells in Pulmonary Hypertension

Abstract

Background-The mechanism of pulmonary artery smooth muscle cell (PA-SMC) hyperplasia in idiopathic pulmonary artery hypertension (iPH) may involve both an inherent characteristic of PA-SMCs and abnormal control by external stimuli. We investigated the role of pulmonary microvascular endothelial cells (P-ECs) in controlling PA-SMC growth. Methods and Results-Serum-free medium of quiescent P-ECs elicited marked PA-SMC proliferation, and this effect was greater with P-ECs from patients with iPH than from control subjects and greater with PA-SMCs from these patients than from control subjects. Fluoxetine, which inhibits serotonin-induced mitogenesis by blocking the serotonin transporter, and p-chlorophenylalanine, which inhibits serotonin synthesis by blocking tryptophan hydroxylase (TPH), caused a similar 60% reduction in the growth-promoting effect of P-EC media, whereas endothelin receptor blockers had no effect. Assays of TPH activity in P-EC medium based on p-chlorophenylalanine-sensitive 5-hydroxytryptophan accumulation or serotonin determination indicated serotonin synthesis by P-ECs and an increase in this TPH-dependent process in iPH. Expression of the tph1 gene encoding the peripheral form of the TPH enzyme was increased in lungs and P-ECs from patients with iPH. Lung TPH1 immunostaining was confined to the pulmonary vessel intima. Conclusions-P-ECs produce paracrine factors governing PA-SMC growth. Serotonin, the main P-EC-derived growth factor, is overproduced in iPH and contributes to PA-SMC hyperplasia.

Cellular microparticles in the pathogenesis of pulmonary hypertension

“…Indeed, accumulating evidence supports the concept that increased endothelial apoptosis at the early stage and decreased endothelial apoptosis at later stages of the disease could contribute to PAH [18]. Consistent with this hypothesis, we have recently reported that primary pulmonary endothelial cells generated from PAH lung specimens exhibit various intrinsic abnormalities and present a modified pro-proliferative, apoptotic-resistant phenotype [4,17,19]. Although we have shown that increased activity of the FGF2 autocrine loop is among the mechanisms needed to acquire this altered endothelial phenotype in PAH [17], the exact nature of pulmonary endothelial cell modification during PAH and the balance between apoptotic and anti-apoptotic phenotypes remain only partially understood.…”

“…Precise and dynamic crosstalk between cells is critical for cellular behaviour, including for cell proliferation, apoptosis, differentiation, migration and survival, and thus crucial for proper tissue organisation and homeostasis; abnormal cellular crosstalk can lead to the development of cancer and PH [4,5]. These wellregulated processes to transfer information between cells occur through direct cell-cell contact, various soluble bioactive factors and through cellular microparticles [6,7].…”

Bone morphogenetic protein signalling in heritable versus idiopathic pulmonary hypertension

“…Human pulmonary microvascular endothelial cells (PECs) were obtained by dispase I (Roche Diagnostics, Penzbeg, Germany) digestion followed by immunomagnetic purification with anti-platelet endothelial cell adhesion molecule-1 (CD31) monoclonal antibody-labelled Dynabeads (Dynal Biotech, Compiegne, France) of a fragment of lung tissue isolated from heritable and idiopathic PAH patients and controls, as previously described [9,14]. To characterise the endothelial phenotype, PECs were labelled with acetylated low-density lipoprotein coupled to a fluorescent carbocyanine dye (1,19-dioctadecyl-3,3,39,39-tetramethylindocarbocyanine perchlorate (Dil-Ac-LDL); Tebu, Le Perray en Yvelines, France) and stained with antibodies against the endothelial cell-specific lectin Ulex europaeus agglutinin-1 (UEA-1; Sigma-Aldrich, Irvine, UK) [15].…”

“…Cells with positive staining for Dil-Ac-LDL and UEA-1 and negative staining for desmin and vimentin were taken as endothelial cells and constituted .95% of our PEC cultures. PECs were used between passages three and six [9,14].…”

“…It has previously been reported that PASMCs from idiopathic PAH patients present with an in vitro proliferative phenotype [9,10]. In the present study, we investigated the effects of BMP4 on Smad and p38MAPK signalling associated with mitosis and apoptosis in cultured PASMCs isolated from idiopathic PAH patients without detected mutations and from heritable PAH patients with mutations.…”