Monthly intraocular injections are widely used to deliver protein-based drugs that cannot cross the blood-retina barrier for the treatment of leading blinding diseases such as age-related macular degeneration (AMD). This invasive treatment carries significant risks, including bleeding, pain, infection, and retinal detachment. Further, current therapies are associated with a rate of retinal fibrosis and geographic atrophy significantly higher than that which occurs in the described natural history of AMD. A novel therapeutic strategy which improves outcomes in a less invasive manner, reduces risk, and provides long-term inhibition of angiogenesis and fibrosis is a felt medical need. Here we show that a single intravenous injection of targeted, biodegradable nanoparticles delivering a recombinant Flt23k intraceptor plasmid homes to neovascular lesions in the retina and regresses CNV in primate and murine AMD models. Moreover, this treatment suppressed subretinal fibrosis, which is currently not addressed by clinical therapies. Murine vision, as tested by OptoMotry, significantly improved with nearly 40% restoration of visual loss induced by CNV. We found no evidence of ocular or systemic toxicity from nanoparticle treatment. These findings offer a nanoparticle-based platform for targeted, vitreous-sparing, extended-release, nonviral gene therapy.
Corneal transparency is a prerequisite for optimal vision and in turn relies on an absence of blood and lymphatic vessels, which is remarkable given the corneas proximity to vascularized tissues. Membrane-bound vascular endothelial growth factor receptor 3 (VEGFR-3), with its cognate ligand vascular endothelial growth factor C (VEGF-C), is a major mediator of lymphangiogenesis. Here, we demonstrate that the cornea expresses a novel truncated isoform of this molecule, soluble VEGFR-3 (sVEGFR-3), which is critical for corneal alymphaticity, by sequestering VEGF-C. sVEGFR-3 binds and sequesters VEGF-C, thereby blocking signaling through VEGFR-3 and suppressing lymphangiogenesis induced by VEGF-C. sVEGFR-3 knockdown leads to lymphangiogenesis and hemangiogenesis in the mouse cornea, while overexpression of sVEGFR-3 inhibits lymphangiogenesis and hemangiogenesis in a murine suture injury model. Pax6(+/-) mice spontaneously develop corneal and lymphatic vessels and are deficient in sVEGFR-3. sVEGFR-3 suppresses hemangiogenesis by blocking VEGF-C-induced phosphorylation of VEGFR-2. Overexpression of sVEGFR-3 leads to a 5-fold increase in corneal transplant survival in mouse models. sVEGFR-3 holds promise as a molecule to control and regress lymphatic-vessel-based dysfunction. Therefore, sVEGFR-3 has the potential to protect the injured cornea from opacification secondary to infection, inflammation, or transplant rejection.
Delivery of anti-inflammatory steroids concurrently to both anterior and posterior segments of the eye is a challenge. The anterior ocular structures limit topical delivery. Injection can be disproportionately and repeatedly invasive and selective for only one ocular hemisphere. We developed a novel implant that can compensate for the limited conveyance of topical medicine and reduce the repetitive invasiveness of injection from the capsular bag allowing dexamethasone (DXM) delivery to both the anterior and posterior chambers. To establish proof of concept, microparticles were prepared with PLGA [poly(d,l-lactide-co-glycolide), 50:50, MW. 7000-17000], hydroxypropyl methyl cellulose (HPMC), and DXM by oil-in-water emulsion/solvent evaporation technique. Zeatsizer Nano and SEM (scanning electron microscopy) results showed microspheres in the range of 8±1µm. The target load of DXM in the microparticles was ~20.0% with a % recovery of 99.9% (w/w). Dose related pharmacokinetics with near zero order kinetics was observed for up to 6 weeks in rabbits with intracapsular bag implants. DXM flow was bidirectional from the endocapsular space and significant concentrations were found in the anterior and posterior chambers after up to 6 weeks. Whereas, with topical drops the exposure was minimal in all the ocular tissues with greater systemic exposure. Intraocular pressure was normal in all of the study groups; slit lamp biomicroscopy examinations revealed that no cells or fibrin formation in the anterior and posterior chamber with implants but flare, cells and fibrin was present in the topical drops group. Histological examination revealed normal tissues and no signs of inflammation in all the groups. The implant did not migrate to the center of the eye or obstruct the visual axis. We believe these findings demonstrate the feasibility of drug delivery from the capsular bag to the anterior and posterior segments effectively compared to topical alternatives.
Optimal phototransduction requires separation of the avascular photoreceptor layer from the adjacent vascularized inner retina and choroid. Breakdown of peri-photoreceptor vascular demarcation leads to retinal angiomatous proliferation or choroidal neovascularization, two variants of vascular invasion of the photoreceptor layer in age-related macular degeneration (AMD), the leading cause of irreversible blindness in industrialized nations. Here we show that sFLT-1, an endogenous inhibitor of vascular endothelial growth factor A (VEGF-A), is synthesized by photoreceptors and retinal pigment epithelium (RPE), and is decreased in human AMD. Suppression of sFLT-1 by antibodies, adeno-associated virus-mediated RNA interference, or Cre/lox-mediated gene ablation either in the photoreceptor layer or RPE frees VEGF-A and abolishes photoreceptor avascularity. These findings help explain the vascular zoning of the retina, which is critical for vision, and advance two transgenic murine models of AMD with spontaneous vascular invasion early in life. DOI:http://dx.doi.org/10.7554/eLife.00324.001.
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