The Laboratory of J. Ambati

Vascular Heterogeneity in the Eye:

The main goal of the laboratory is to elucidate molecular mechanisms that fundamentally regulate vascular growth in normal and diseased states in the eye. In 2006, we answered the foremost outstanding question in vascular biology: "What is responsible for avascularity of the cornea?" This work (Ambati et al. Nature 2006) demonstrated that, contrary to prevailing dogma that a multitude of anti-angiogenic molecules was required for corneal avascularity, a single protein - soluble VEGF receptor-1 - was uniquely responsible. This work was hailed by Science as a “Signaling Breakthrough of the Year”, and is far-reaching because the cornea is the default platform for testing therapies for cancer, atherosclerosis, and other diseases driven by angiogenesis.

Paradigms in Ocular Angiogenesis:

Several corneal and retinal diseases are hallmarked by neovascularization that often leads to irreversible blindness. We seek to identify the specific mediators for such pathologic responses in order to develop targeted therapeutics to reverse and prevent these devastating disorders. Our laboratory was the first to demonstrate the presence of in situ complement activation in the retina and choroid of patients with age-related macular degeneration (AMD). We showed (Nozaki et al. PNAS 2006) that this complement activation triggers the angiogenic switch that transforms the disease state from an atrophic to a neovascular phenotype. This vital observation has now resulted in the initiation of pre-clinical/Phase I clinical trials of complement inhibitors in AMD by more than a dozen pharmaceutical/biotech companies. Crucial to this translational advance was our lab’s report of the first animal model of AMD (Ambati et al. Nat Med 2003). This data in conjunction with several other studies has supported a major paradigm shift towards inflammatory and immunologic mediators playing a significant role in the development of AMD and its progression to choroidal neovascularization.

The Interface of Immunity and Vascular Response in the Eye:

How does the omnipresent immune system induce pathologic vascular responses in the eye? Given the fundamental lack of knowledge on the molecular basis of immune regulated angiogenesis, our lab is committed to unraveling these complex biologic interactions. We recently identified (Kleinman et al. Nature 2008) the immune receptor TLR3 as a surprising signaling receptor for small interfering RNAs (siRNAs) in a sequence-independent manner. We showed that siRNAs "generically" suppress angiogenesis in multiple mouse models by activating cell surface TLR3 rather than by triggering RNA interference. Concomitantly, we discovered (Yang et al. NEJM 2008) a hypomorphic polymorphism in TLR3 which confers protection against the atrophic form of AMD. These findings, which were covered in Commentaries by Nature Medicine and Nature Biotechnology, advance the nascent understanding of the multifunctional aspects of the immune system within the eye. We will continue our investigations into immunovascular biology with the goal of mapping this critical interface while creating more effective and tolerable medicines to treat neovascular diseases.