In vivo scanning laser fundus and high-resolution OCT imaging of retinal ganglion cell injury in a non-human primate model with an activatable fluorescent-labeled TAT peptide probe.

The optical imaging agent TcapQ488 has enabled imaging of retinal ganglion cell (RGC) injury in vivo in rodents and has potential as an effective diagnostic probe for early detection and intervention monitoring in glaucoma patients. In the present study, we investigated TcapQ488 in non-human primates (NHPs) to identify labeling efficacy and early signals of injured RGC, to determine species-dependent changes in RGC probe uptake and clearance, and to determine dose-limiting toxicities. Doses of 3, 6, and 12 nmol of TcapQ488 were delivered intravitreally to normal healthy NHP eyes and eyes that had undergone hemiretinal endodiathermy axotomy (HEA) in the inferior retina.

Development of Microcystoid Macular Degeneration in the Retina of Nonhuman Primates: Time-Course and Associated Pathologies.

Purpose: Microcystoid macular degeneration (MMD) is a condition where cystoid vacuoles develop within the inner nuclear layer of the retina in humans in a variety of disorders. Here we report the occurrence of MMD in non-human primates (NHPs) with various retinal ganglion cell (RGC) pathologies and evaluate the hypothesis that MMD does not precede RGC loss but follows it.

Methods: Morphological studies were performed of the retinas of NHPs, specifically both rhesus () and cynomolgus macaques (), in which MMD was identified after induction of experimental glaucoma (EG), hemiretinal endodiathermy axotomy (HEA), and spontaneous idiopathic bilateral optic atrophy.

Frequent first-trimester pregnancy loss in rhesus macaques infected with African-lineage Zika virus.

In the 2016 Zika virus (ZIKV) pandemic, a previously unrecognized risk of birth defects surfaced in babies whose mothers were infected with Asian-lineage ZIKV during pregnancy. Less is known about the impacts of gestational African-lineage ZIKV infections. Given high human immunodeficiency virus (HIV) burdens in regions where African-lineage ZIKV circulates, we evaluated whether pregnant rhesus macaques infected with simian immunodeficiency virus (SIV) have a higher risk of African-lineage ZIKV-associated birth defects.

Multifocal electroretinography increases following experimental glaucoma in nonhuman primates with retinal ganglion cell axotomy.

Purpose: To determine whether short-latency changes in multifocal electroretinography (mfERG) observed in experimental glaucoma (EG) are secondary solely to retinal ganglion cell (RGC) loss or whether there is a separate contribution from elevated intraocular pressure (IOP).

Methods: Prior to operative procedures, a series of baseline mfERGs were recorded from six rhesus macaques using a 241-element unstretched stimulus. Animals then underwent hemiretinal endodiathermy axotomy (HEA) by placing burns along the inferior 180° of the optic nerve margin in the right eye (OD).

Quantitative definition of neurobehavior, vision, hearing and brain volumes in macaques congenitally exposed to Zika virus.

Congenital Zika virus (ZIKV) exposure results in a spectrum of disease ranging from severe birth defects to delayed onset neurodevelopmental deficits. ZIKV-related neuropathogenesis, predictors of birth defects, and neurodevelopmental deficits are not well defined in people. Here we assess the methodological and statistical feasibility of a congenital ZIKV exposure macaque model for identifying infant neurobehavior and brain abnormalities that may underlie neurodevelopmental deficits.

Rapid Development of Glaucoma Via ITV Nonselective ANGPT 1/2 Antibody: A Potential Role for ANGPT/TIE2 Signaling in Primate Aqueous Humor Outflow.

Purpose: Investigate a significant, dose-related increase in IOP, leading to glaucomatous damage to the neuroretina and optic nerve following intravitreal (ITV) administration of a bispecific F(ab')2 [anti-VEGF/Angiopoietins [ANGPT]F(ab')2] molecule in adult monkeys.

Methods: ITV ocular tolerability and investigation of anti-VEGF/ANGPT F(ab')2 (blocking both ANGPT1 and ANGPT2) was done in monkeys; mechanistic studies were done in neonatal mice.

Results: Following the second ITV dose of anti-VEGF/ANGPT F(ab')2, all 1.

Determination of a No Observable Effect Level for Endotoxin Following a Single Intravitreal Administration to Cynomolgus Monkeys.

To characterize the inflammatory response and determine the no-observable-effect level (NOEL) in cynomolgus monkey eyes after intravitreal (ITV) injection of endotoxin. The inflammatory response to endotoxin was assessed in a single-dose study in monkeys at doses of 0.01 to 0.

Glaucoma Drugs in the Pipeline.

Glaucoma is a chronic disease that can be challenging to treat for both patients and physicians. Most patients will require more than 1 medication over time to maintain their intraocular pressure (IOP) at a physiologically benign level. Patients may become refractory to existing compounds and many struggle with adherence to multiple topical drop regimens.

Biomechanical, ultrastructural, and electrophysiological characterization of the non-human primate experimental glaucoma model.

Laser-induced experimental glaucoma (ExGl) in non-human primates (NHPs) is a common animal model for ocular drug development. While many features of human hypertensive glaucoma are replicated in this model, structural and functional changes in the unlasered portions of trabecular meshwork (TM) of laser-treated primate eyes are understudied. We studied NHPs with ExGl of several years duration.

In vivo evaluation of the cornea and conjunctiva of the normal laboratory beagle using time- and Fourier-domain optical coherence tomography and ultrasound pachymetry.

Objective: To obtain normative data for the canine cornea and conjunctiva using high-resolution time- and Fourier-domain optical coherence tomography (TD-OCT and FD-OCT) and ultrasound pachymetry (USP).

Animals: One hundred sixty-eight eyes of 133 healthy young intact laboratory beagles.

Procedures: The cornea and conjunctiva of 16 eyes of 8 healthy young intact female beagles were imaged using FD-OCT.

Exciting directions in glaucoma.

Glaucoma is a complex, life-long disease that requires an individualized, multifaceted approach to treatment. Most patients will be started on topical ocular hypotensive eyedrop therapy, and over time multiple classes of drugs will be needed to control their intraocular pressure. The search for drugs with novel mechanisms of action, to treat those who do not achieve adequate intraocular pressure control with, or become refractory to, current therapeutics, is ongoing, as is the search for more efficient, targeted drug delivery methods.

The trabecular meshwork in normal eyes and in exfoliation glaucoma.

Trabecular meshwork (TM) and ciliary muscle contraction and relaxation function together to provide control of outflow. The active role the TM plays in the regulation of intraocular pressure (IOP) is mediated by cytoskeletal and contractility mechanisms as well as signal/transduction factors that mediate its response to stressors. This complex system is altered with age and the glaucomas, and it can be difficult to differentiate between the various etiological effects/agents.

Latrunculin B Reduces Intraocular Pressure in Human Ocular Hypertension and Primary Open-Angle Glaucoma.

Purpose: To evaluate the safety, tolerability, and intraocular pressure (IOP)-lowering effect of Latrunculin-B (Lat-B), a marine macrolide that disrupts the actin cytoskeleton, in patients with ocular hypertension (OHT) or early primary open-angle glaucoma (POAG).

Methods: In this Phase I, multicenter, double-masked, randomized, placebo-controlled, ascending-dose study, subjects with bilateral OHT or early POAG (>22 mm Hg) received one of four concentrations of INS115644 (Lat-B ophthalmic solutions, 0.005%, 0.

Prospects for lentiviral vector mediated prostaglandin F synthase gene delivery in monkey eyes in vivo.

Currently, the most effective outflow drugs approved for clinical use are prostaglandin F2α analogues, but these require daily topical self-dosing and have various intraocular, ocular surface and extraocular side effects. Lentiviral vector-mediated delivery of the prostaglandin F synthase (PGFS) gene, resulting in long-term reduction of intraocular pressure (IOP), may eliminate off-target tissue effects and the need for daily topical PGF2α self-administration. Lentiviral vector-mediated delivery of the PGFS gene to the anterior segment has been achieved in cats and non-human primates.

Application of canaloplasty in glaucoma gene therapy: where are we?

Purpose: Schlemm's canal (SC) inner wall is adjacent to the juxtacanalicular trabecular meshwork (TM) over their entire circumference. We seek to transfer reporter and therapeutic genes to these outflow-modulating tissues via canaloplasty surgery in live monkeys.

Methods: A standard canaloplasty surgical approach was performed in cynomolgus monkeys using flexible canaloplasty catheters, modified for monkey eyes with a 175-μm outer diameter and an LED-lighted tip.

Benzalkonium chloride and glaucoma.

Glaucoma patients routinely take multiple medications, with multiple daily doses, for years or even decades. Benzalkonium chloride (BAK) is the most common preservative in glaucoma medications. BAK has been detected in the trabecular meshwork (TM), corneal endothelium, lens, and retina after topical drop installation and may accumulate in those tissues.

Structural and functional effects of hemiretinal endodiathermy axotomy in cynomolgus macaques.

Purpose: Outer retinal injury has been well described in glaucoma. To better understand the source of this injury, we wanted to develop a reliable model of partial retinal ganglion cell (RGC) axotomy.

Methods: Endodiathermy spots were placed along the inferior 180° adjacent to the optic nerve margin in the right eyes of four cynomolgus monkeys.

Optical coherence tomography for the evaluation of retinal and optic nerve morphology in animal subjects: practical considerations.

Optical coherence tomography (OCT) is a noninvasive, noncontact imaging technique capable of producing high-resolution images of the retina and optic nerve. These images provide information that is useful for following the progression and/or resolution of posterior segment disease. Rapid advances in OCT technology allow the acquisition of increasingly detailed images, approaching the original goal of providing in vivo histopathology.

Structure/function studies and the effects of memantine in monkeys with experimental glaucoma.

Purpose. The scanning laser polarimetry with variable corneal compensation (GDx VCC) methodology was established and verified in monkeys with experimental glaucoma (ExpG). Terminal GDx parameters were correlated with axon counts and electrophysiologic measures.

Functional and anatomic consequences of subretinal dosing in the cynomolgus macaque.

Objective: To characterize functional and anatomic sequelae of a bleb induced by subretinal injection.

Methods: Subretinal injections (100 μL) of balanced salt solution were placed in the superotemporal macula of 1 eye in 3 cynomolgus macaques. Fellow eyes received intravitreal injections (100 μL) of balanced salt solution.

Effect of nitric oxide compounds on monkey ciliary muscle in vitro.

The effects of various nitric oxide compounds and their inhibitors on monkey ciliary muscle contraction in vitro were investigated in both the longitudinal and circular vectors. The responses to nitric oxide compounds in carbachol precontracted ciliary muscle consisted of an initial relaxation often followed by recovery to near carbachol precontracted levels while the compound was still present. Sodium nitroprusside produced the greatest relaxation responses (nearly 100% relaxation in both vectors at 10(-3) M).

Astrocyte and microglial activation in the lateral geniculate nucleus and visual cortex of glaucomatous and optic nerve transected primates.

Purpose: To examine early cellular changes, including astrocyte reactivity and microglial activation, in the central nervous system (CNS) after unilateral optic nerve transection (ONT) or ocular hypertension (OHT) in monkeys.

Methods: Unilateral ONT or OHT was achieved in monkeys for periods ranging from two weeks to two months in duration. After intracardial perfusion, sections of the lateral geniculate nucleus (LGN) and visual cortex (V1) were examined by immunohistochemistry for glial fibrillary acidic protein (GFAP) and CD11b, a subunit of the complement 3 receptor and marker of macrophage and microglia cells (MAC-1).

Self-complementary AAV virus (scAAV) safe and long-term gene transfer in the trabecular meshwork of living rats and monkeys.

Purpose: AAV vectors produce stable transgene expression and elicit low immune response in many tissues. AAVs have been the vectors of choice for gene therapy for the eye, in particular the retina. scAAVs are modified AAVs that bypass the required second-strand DNA synthesis to achieve transcription of the transgene.

Gene therapy targeting glaucoma: where are we?

In a chronic disease such as glaucoma, a therapy that provides a long lasting local effect with minimal systemic side effects, while circumventing the issue of patient compliance, is very attractive. The field of gene therapy is growing rapidly and ocular applications are expanding. Our understanding of the molecular pathogenesis of glaucoma is leading to greater specificity in ocular tissue targeting.