All TIEd up: mechanisms of Schlemm's canal maintenance.

Glaucoma is a leading cause of blindness, with an estimated world-wide prevalence of 3.5% in members of the population older than 40 years of age. Elevated intraocular pressure as the result of abnormal resistance to aqueous humor drainage is a major contributing, and the only preventable, factor in glaucoma development. Schlemm's canal (SC), a lymphatic-like vessel encircling the anterior portion of the eye, plays a key role in promoting aqueous humor outflow and maintenance of normal intraocular pressure. The risk of developing glaucoma increases with age; therefore, understanding mechanisms of SC maintenance and how aging affects SC function are of special importance, both for prevention and novel treatment approaches to glaucoma. Using a compelling array of genetic models, Kim et al. report in this issue of the JCI that continuous angiopoietin/TIE2 signaling is required for maintaining SC identity and integrity during adulthood and show that its age-related changes can be rescued by a TIE2 agonistic antibody.