Patients with congenital lymphedema suffer from tissue swelling in part due to mutations in genes regulating lymphatic valve development. Lymphatic valve leaflets grow and are maintained throughout life in response to oscillatory shear stress (OSS), which regulates gene transcription in lymphatic endothelial cells (LECs). Here, we identified the first transcription factor, Foxo1, that repressed lymphatic valve formation by inhibiting the expression of valve-forming genes. We showed that both embryonic and postnatal ablation of Foxo1 in LECs induced additional valve formation in postnatal and adult mice in multiple tissues. Our quantitative analyses revealed that after deletion, the total number of valves in the mesentery was significantly (P < 0.01) increased in the Foxo1LEC-KO mice compared with Foxo1fl/fl controls. In addition, our quantitative real-time PCR (RT-PCR) data from cultured LECs showed that many valve-forming genes were significantly (P < 0.01) upregulated upon knockdown of FOXO1. To confirm our findings in vivo, rescue experiments showed that Foxc2+/– mice, a model of lymphedema-distichiasis, had 50% fewer lymphatic valves and that the remaining valves exhibited backleak. Both valve number and function were completely restored to control levels upon Foxo1 deletion. These findings established FOXO1 as a clinically relevant target to stimulate de novo lymphatic valve formation and rescue defective valves in congenital lymphedema.
Joshua P. Scallan, Luz A. Knauer, Huayan Hou, Jorge A. Castorena-Gonzalez, Michael J. Davis, Ying Yang
This file is in Adobe Acrobat (PDF) format. If you have not installed and configured the Adobe Acrobat Reader on your system.
PDFs are designed to be printed out and read, but if you prefer to read them online, you may find it easier if you increase the view size to 125%.
Many versions of the free Acrobat Reader do not allow Save. You must instead save the PDF from the JCI Online page you downloaded it from. PC users: Right-click on the Download link and choose the option that says something like "Save Link As...". Mac users should hold the mouse button down on the link to get these same options.