Objective: Hereditary haemorrhagic telangiectasia (HHT) is originated by mutations in endoglin (HHT1) and ALK1 (HHT2) genes. The purpose of this work was to isolate and characterize circulating endothelial cells from HHT patients. Methods: Pure primary cultures of blood outgrowth endothelial cells (BOECs) were obtained from 50 ml of peripheral blood by selection on collagen plates with endothelial medium. Results: The amount of endoglin in HHT1-BOECs is half the controls, but HHT2-BOECs are also endoglin-deficient. Since the TGF-β/ALK1 pathway activates the endoglin promoter activity, these results suggest the involvement of ALK1 in endoglin gene expression. Endothelial TGF-β pathways, mediated by ALK1 and ALK5, are impaired in HHT cells. HHT-BOECs show disorganized and depolymerized actin fibers, as compared to the organized stress fibers of healthy-BOECs. Functionally, HHT-BOECs have impaired tube formation, in contrast with the cord-like structures derived from normal donors. Conclusions: Decreased endoglin expression, impaired TGF-β signalling, disorganized cytoskeleton, and failure to form cord-like structures are common characteristics of endothelial cells from HHT patients. These features may lead to fragility of small vessels and bleeding characteristic of the HHT vascular dysplasia and to a disrupted and abnormal angiogenesis, which may explain the clinical symptoms associated with this disease.
Bibliographical noteFunding Information:
Authors are indebted to Drs. Michelle Letarte and Ursula Cymerman for suggestions and advice on sequencing methods, Dr. Benilde Jimenez for human fibroblasts, Carmen Langa for technical assistance, Dr. Carmelo Morales for data on HHT families, Ma Victoria Gomez España and María Jesús Borquez for blood extractions, and to all the volunteers and HHT patients for their collaboration. Drs. R. Hebbel and J. Nguyen are funded by the National Institutes of Health USA (HL71269). This work was supported by grants from Ministerio de Educación y Ciencia (SAF2004-01390), Fondo de Investigación Sanitaria (PI020200) and HHT Foundation International to CB. Africa Fernandez-L is a predoctoral fellow of I3P Program from Ministerio de Educación y Ciencia.
- Endothelial function
- Endothelial receptors
- Signal transduction