Role of angiopoietin-2 in corneal lymphangiogenesis.
OBJECTIVE
Lymphatic research has progressed rapidly in recent years. Lymphatic dysfunction has been found in myriad disorders from cancer metastasis to transplant rejection; however, effective treatment for lymphatic disorders is still limited. This study investigates the role of angiopoietin-2 (Ang-2) in corneal inflammatory lymphangiogenesis (LG) in vivo and in lymphatic endothelial cell (LEC) functions in vitro.


METHODS
Standard suture placement model was used to study Ang-2 expression in inflamed cornea, and corneal LG and hemangiogenesis (HG) responses in Ang-2 knockout mice. Moreover, human LEC culture system was used to examine the effect of Ang-2 gene knockdown on LEC functions using small interfering RNAs (siRNAs). The effect of siRNA treatment on corneal LG was also assessed in vivo.


RESULTS
Angiopoietin-2 was expressed on lymphatic vessels and macrophages in inflamed cornea. While corneal LG response was abolished in Ang-2 knockout mice, the HG response was also significantly suppressed with disorganized patterning. Moreover, anti-Ang-2 treatment inhibited LEC proliferation and capillary tube formation in vitro and corneal LG in vivo.


CONCLUSIONS
Angiopoietin-2 is critically involved in lymphatic processes in vivo and in vitro. Further investigation of the Ang-2 pathway may provide novel insights and therapeutic strategies for lymphatic-related disorders, which occur both inside and outside the eye.
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States.
Don
D
Yuen
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States.
Sammy
S
Grimaldo
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States.
Roberto
R
Sessa
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States.
Tatiana
T
Ecoiffier
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States Graduate Group in Vision Science, University of California, Berkeley, Berkeley, California, United States.
Tan
T
Truong
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States.
Eric
E
Huang
Department of Surgery, School of Medicine, University of Arizona, Tucson, Arizona, United States.
Michael
M
Bernas
Department of Surgery, School of Medicine, University of Arizona, Tucson, Arizona, United States.
Sarah
S
Daley
Department of Surgery, School of Medicine, University of Arizona, Tucson, Arizona, United States.
Marlys
M
Witte
Center for Eye Disease and Development, Program in Vision Science and School of Optometry, University of California, Berkeley, Berkeley, California, United States Graduate Group in Vision Science, University of California, Berkeley, Berkeley, California, United States.
Lu
L
Chen
D042702:Angiopoietin-2 / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D003315:Cornea / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology; D016510:Corneal Neovascularization / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D042583:Lymphangiogenesis / Q000235:genetics*; D042601:Lymphatic Vessels / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D012313:RNA / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D042702:Angiopoietin-2; D012313:RNA
Ang-2; corneal lymphangiogenesis; knockout mice; lymphatic endothelial cells; small interfering RNA