A lymphatic defect causes ocular hypertension and glaucoma in mice

Area of Science:

• Ophthalmology
• Vascular Biology
• Genetics

Background:

• Glaucoma is a leading cause of blindness affecting over 60 million people globally.
• Elevated intraocular pressure (IOP), driven by impaired aqueous humor drainage, is a primary risk factor for glaucoma.
• The angiopoietin/TIE2 (ANGPT/TIE2) signaling pathway is crucial for vascular development and function.

Purpose of the Study:

• To investigate the role of the ANGPT/TIE2 signaling pathway in the development of glaucoma.
• To elucidate the molecular mechanisms underlying impaired ocular drainage in glaucoma.
• To explore the cooperative function of angiopoietin ligands in lymphatic endothelium.

Main Methods:

• Genetic disruption of Angpt1 and Angpt2 in mice (A1A2Flox(WB) mice) to induce deletion.
• Histological analysis of ocular tissues to examine drainage pathways, including Schlemm's canal and lymphatic capillaries.
• Assessment of intraocular pressure (IOP) and retinal ganglion cell degeneration.
• Investigation of transcription factor expression (PROX1, VEGFR3, FOXC) in ocular endothelium.

Main Results:

• Genetic deletion of ANGPT1 and ANGPT2 led to the absence of ocular drainage pathways, resulting in high IOP, buphthalmos, and glaucoma features.
• ANGPT1 or ANGPT2 expression alone was sufficient for normal ocular drainage.
• Loss of FOXC2 in lymphatics caused TIE2 downregulation, suggesting a link to glaucoma in patients with FOXC mutations.
• Cooperation between ANGPT1 and ANGPT2 is essential for regulating TIE2 in the eye's lymphatic network.

Conclusions:

• The ANGPT/TIE2 signaling pathway is critical for maintaining ocular drainage and preventing glaucoma.
• Cooperation between angiopoietin ligands is vital for lymphatic endothelial function in the eye.
• Dysregulation of this pathway, potentially involving FOXC transcription factors, provides a molecular basis for glaucoma pathogenesis.