O. Lyons1, P. Saha1, C. Seet1, A. Kuchta2, A. Arnold2, S. Grover4, V. Rashbrook1, A. Sabine5, G. Vizcay-Barrena3, A. Patel1, F. Ludwinski1, S. Padayachee2, T. Kume6, B. Kwak7, G. Brice8, S. Mansour8, P. Ostergaard9, P. Mortimer9, S. Jeffery9, N. Brown10, T. Makinen11, T. Petrova5, B. Modarai1, A. Smith1 1King’s College London,Academic Department Of Surgery, Cardiovascular Division, BHF Centre Of Research Excellence,London, LONDON, United Kingdom 2Guy’s & St Thomas’ NHS Foundation Trust,Ultrasonic Angiology,London, LONDON, United Kingdom 3King’s College London,Centre For Ultrastructural Imaging,London, LONDON, United Kingdom 4Division Of Hemostasis And Thrombosis,Beth Israel Deaconess Medical Centre,Boston, MA, USA 5Ludwig Institute For Cancer Research And Division Of Experimental Pathology,Department Of Fundamental Oncology, Centre Hospitalier Universitaire Vaudois And University Of Lausanne, Epalinges, Switzerland,Lausanne, LAUSANNE, Switzerland 6Feinberg Cardiovascular Research Institute,Northwestern University School Of Medicine,Evanston, IL, USA 7Department Of Pathology And Immunology,University Of Geneva,Geneva, GENEVA, Switzerland 8South West Thames Regional Genetics Service,St George’s Hospital,London, LONDON, United Kingdom 9Cardiovascular And Cell Sciences Institute,St George’s Hospital,London, LONDON, United Kingdom 10Institute Of Medical And Biomedical Education,St George’s Hospital,London, LONDON, United Kingdom 11Rudbeck Laboratory,Department Of Immunology, Genetics And Pathology, Uppsala University,Uppsala, UPPSALA, Sweden
Introduction:
Venous valves (VVs) prevent blood reflux that can give rise to chronic venous hypertension and ulceration. Patients with mutations in the genes encoding the transcription factor Foxc2 and gap junction protein, connexin47 (Cx47), have venous reflux. We sought to examine VV phenotypes in these patients and to use a murine model to elucidate the function of these proteins in VV development.
Methods:
Human VV number and length were quantified by ultrasound. Murine VV phenotype (marked by expression of Prox1) was examined using confocal microscopy, in wild-type and mice with complete or conditional deletion of genes expressing transcription factors and connexins.
Results:
Patients with Foxc2/Cx47 mutations had reduced valve number (P<0.0005) and shorter valves (P<0.0005). VV initiation in mice was marked by elongation/reorientation of Prox1hi endothelia by postnatal day 0. Expression of Foxc2 and Nfatc1, and the gap junction proteins, Cx47, Cx43 and Cx37, were temporo-spatially regulated during this process. Combined Foxc2 deletion with calcineurin-NFAT inhibition disrupted endothelial organisation, suggesting co-operative Foxc2-NFATc1 patterning. Deletion/knockout of each of the connexins also disrupted endothelial organisation. Specific deletion of endothelial Foxc2 had no effect on VV maintenance.
Conclusion:
Patients with mutations in Foxc2 and Cx47 have globally reduced VV numbers and shorter VV leaflets. Foxc2 and Nfatc1 likely cooperate to organise the initial ring of VV-forming cells. Connexins are critical for early organisation of valve-forming cells at P0 and failure of this process may underlie abnormal VVs identified in patients with mutated Cx47. Foxc2, in endothelia, is not required for valve maintenance.