Prox1-GFP/Flt1-DsRed transgenic mice: an animal model for simultaneous live imaging of angiogenesis and lymphangiogenesis

Abstract

The roles of angiogenesis in development, health, and disease have been studied extensively; however, the studies related to lymphatic system are limited due to the difficulty in observing colorless lymphatic vessels. But recently, with the improved technique, the relative importance of the lymphatic system is just being revealed. We bred transgenic mice in which lymphatic endothelial cells express GFP (Prox1-GFP) with mice in which vascular endothelial cells express DsRed (Flt1-DsRed) to generate Prox1-GFP/Flt1-DsRed (PGFD) mice. The inherent fluorescence of blood and lymphatic vessels allows for direct visualization of blood and lymphatic vessels in various organs via confocal and two-photon microscopy and the formation, branching, and regression of both vessel types in the same live mouse cornea throughout an experimental time course. PGFD mice were bred with CDh5CreERT2 and VEGFR2lox knockout mice to examine specific knockouts. These studies showed a novel role for vascular endothelial cell VEGFR2 in regulating VEGFC-induced corneal lymphangiogenesis. Conditional deletion of vascular endothelial VEGFR2 abolished VEGFA- and VEGFC-induced corneal lymphangiogenesis. These results demonstrate the potential use of the PGFD mouse as a powerful animal model for studying angiogenesis and lymphangiogenesis.

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Potential lymphangiogenesis therapies: Learning from current antiangiogenesis therapies—A review

“…They found that lymphangiogenesis occurred even when angiogenesis did not, in concordance with previous studies reporting the occurrence of corneal lymphangiogenesis independently of hemangiogenesis . Conditional deletion of VEGFR2 in endothelial cells markedly reduced lymphangiogenesis in the mouse cornea in response to VEGF‐A and VEGF‐C pellets, compared to that in mice without this conditional deletion, suggesting a role for blood endothelial cell VEGFR2 in lymphatic vessel formation and growth . There seem to be various combinations of ligand‐binding affinities and kinase activities that produce a spectrum of downstream effects, both angiogenic and lymphangiogenic.…”

“…[118][119][120][121][122][123] Conditional deletion of VEGFR2 in endothelial cells markedly reduced lymphangiogenesis in the mouse cornea in response to VEGF-A and VEGF-C pellets, compared to that in mice without this conditional deletion, suggesting a role for blood endothelial cell VEGFR2 in lymphatic vessel formation and growth. 78 There seem to be various combinations of ligand-binding affinities and kinase activities that produce a spectrum of downstream effects, both angiogenic and lymphangiogenic. Thus, before a therapeutic target can be determined, it is crucial to further characterize the specific mechanisms of the VEGF signaling system.…”

Fluorescent reporter transgenic mice for in vivo live imaging of angiogenesis and lymphangiogenesis

“…Finally, Zhong et al developed Prox1-GFP/Flt1-DsRed (PGFD) mice for refined tracking of both blood and lymphatic vascular changes over time, particularly the monitoring of corneal hemangiogenesis and lymphangiogenesis within individual mice throughout a 14-day period after corneal injury [51]. Using confocal microscopy and two-photon imaging, they rapidly visualized fluorescent three-dimensional blood and lymphatic vessel patterns up to 150 and 400 µm deep, respectively, in large, unprocessed specimens from many tissues.…”

“…( b) The percent areas occupied by alkali burn-induced corneal HA and LA were calculated over the experimental time course. Reprinted with permission from [51]. …”