Poster presentation presented by Valérie Smolders at the ERS 2017 on September 11th 2017, Milan, Italy. This poster summarize the results from endothelial cells derived from patients with CTEPH. Both functional and metabolic studies are described. Rationale: Material obtained at pulmonary endarterectomy (PEA) offers the unique opportunity to unravel pathophysiological mechanisms underlying CTEPH. Vascular changes occurring in CTEPH might be linked to metabolic dysregulation of CTEPH endothelial cells (EC). The aim of this study was the development of an in vitro model of EC pathology using primary cultures of patient derived EC to assay cell metabolism in CTEPH. Method: Like previously showed, isolated cells from specimens collected at PEA (N=12) were confirmed as being EC. Cell migration was evaluated using scratch assay. Metabolic changes in CTEPH-EC are being studied using RT-PCR, Western-Blot and colorimetric assays. Results: CTEPH-EC showed a reduced capacity to recover from a scratch when compared with human pulmonary arterial endothelial cells (HPAE) (1-way anova, p<0.0001). HIF-1a was highly expressed in CTEPH-EC when compared with HPAE cells (3.21±1.38 vs 1.54±0.87; p<0.001). Lactate dehydrogenase (LDH) activity, measured in the supernatant of cultured cells, was higher for CETPH-EC when compared with controls (77.57±12.11 vs 53.82±3.70; p<0.001). The amount of lactate in the supernatant of CETPH-EC was higher when compared to HPAE cells, whereas glucose was lower in comparison with controls (Lactate: 6.80±2.19 vs 4.49±2.29; p<0.05, Glucose: 48.31±21.89 vs 60±20.80; p>0.05). Conclusion: CTEPH-EC show functional impairment. Higher expression of HIF-1a is a noteworthy link with metabolic alterations. Preliminary data suggesting an increase in LDH activity can be explained, at least partially, by higher expression of HIF-1a. Variations in lactate and glucose support the presence of a metabolic pathophenotype in CTEPH-EC. Funded by: SEPAR, SOCAP, FIS: PI15/00582, HORIZON 2020 – Marie Skłodowska-Curie grant – ITN-European Joint Doctorate