Application of AdamSPGD algorithm to sensor-less adaptive optics in coherent free-space optical communication system.

Sensor-less adaptive optics based on stochastic parallel gradient descent (SPGD) is effective for the compensation of atmospheric disturbances in coherent free-space optical communication systems. However, SPGD converges slowly and easily falls into local extremes. Combining adaptive moment estimation and SPGD, we propose the AdamSPGD algorithm for efficient wavefront correction. Theoretical analysis and numerical simulations demonstrate that AdamSPGD can significantly increase the convergence speed, robustness, and dynamic ability, thereby more efficiently suppress the negative effects of atmospheric turbulence on mixing efficiency, bit error rate, and outage probability. Experimental results show that AdamSPGD reduces ∼50% of iterations. The improved performances make the proposed algorithm suitable for SLAO to improve the quality of optical communications.

Mouse models of X-linked juvenile retinoschisis have an early onset phenotype, the severity of which varies with genotype.

X-linked juvenile retinoschisis (XLRS) is an early-onset inherited condition that affects primarily males and is characterized by cystic lesions of the inner retina, decreased visual acuity and contrast sensitivity and a selective reduction of the electroretinogram (ERG) b-wave. Although XLRS is genetically heterogeneous, all mouse models developed to date involve engineered or spontaneous null mutations. In the present study, we have studied three new Rs1 mutant mouse models: (1) a knockout with inserted lacZ reporter gene; (2) a C59S point mutant substitution and (3) an R141C point mutant substitution. Mice were studied from postnatal day (P15) to 28 weeks by spectral domain optical coherence tomography and ERG. Retinas of P21-22 mice were examined using biochemistry, single cell electrophysiology of retinal ganglion cells (RGCs) and by immunohistochemistry. Each model developed intraretinal schisis and reductions in the ERG that were greater for the b-wave than the a-wave. The phenotype of the C59S mutant appeared less severe than the other mutants by ERG at adult ages. RGC electrophysiology demonstrated elevated activity in the absence of a visual stimulus and reduced signal-to-noise ratios in response to light stimuli. Immunohistochemical analysis documented early abnormalities in all cells of the outer retina. Together, these results provide significant insight into the early events of XLRS pathophysiology, from phenotype differences between disease-causing variants to common mechanistic events that may play critical roles in disease presentation and progression.

The potassium channel Kcne3 is a VEGFA-inducible gene selectively expressed by vascular endothelial tip cells.

Angiogenesis is largely driven by motile endothelial tip-cells capable of invading avascular tissue domains and enabling new vessel formation. Highly responsive to Vascular Endothelial Growth-Factor-A (VEGFA), endothelial tip-cells also suppress angiogenic sprouting in adjacent stalk cells, and thus have been a primary therapeutic focus in addressing neovascular pathologies. Surprisingly, however, there remains a paucity of specific endothelial tip-cell markers. Here, we employ transcriptional profiling and a lacZ reporter allele to identify Kcne3 as an early and selective endothelial tip-cell marker in multiple angiogenic contexts. In development, Kcne3 expression initiates during early phases of angiogenesis (E9) and remains specific to endothelial tip-cells, often adjacent to regions expressing VEGFA. Consistently, Kcne3 activation is highly responsive to exogenous VEGFA but maintains tip-cell specificity throughout normal retinal angiogenesis. We also demonstrate endothelial tip-cell selectivity of Kcne3 in several injury and tumor models. Together, our data show that Kcne3 is a unique marker of sprouting angiogenic tip-cells and offers new opportunities for investigating and targeting this cell type.

Performance analysis of a coherent free space optical communication system based on experiment.

Based on our previous study and designed experimental AO system with a 97-element continuous surface deformable mirror, we conduct the performance analysis of a coherent free space optical communication (FSOC) system for mixing efficiency (ME), bit error rate (BER) and outage probability under different Greenwood frequency and atmospheric coherent length. The results show that the influence of the atmospheric temporal characteristics on the performance is slightly stronger than that of the spatial characteristics when the receiving aperture and the number of sub-apertures are given. This analysis result provides a reference for the design of the coherent FSOC system.

Aflibercept exhibits VEGF binding stoichiometry distinct from bevacizumab and does not support formation of immune-like complexes.

Anti-vascular endothelial growth factor (VEGF) therapies have improved clinical outcomes for patients with cancers and retinal vascular diseases. Three anti-VEGF agents, pegaptanib, ranibizumab, and aflibercept, are approved for ophthalmic indications, while bevacizumab is approved to treat colorectal, lung, and renal cancers, but is also used off-label to treat ocular vascular diseases. The efficacy of bevacizumab relative to ranibizumab in treating neovascular age-related macular degeneration has been assessed in several trials. However, questions persist regarding its safety, as bevacizumab can form large complexes with dimeric VEGF165, resulting in multimerization of the Fc domain and platelet activation. Here, we compare binding stoichiometry, Fcγ receptor affinity, platelet activation, and binding to epithelial and endothelial cells in vitro for bevacizumab and aflibercept, in the absence or presence of VEGF. In contrast to bevacizumab, aflibercept forms a homogenous 1:1 complex with each VEGF dimer. Unlike multimeric bevacizumab:VEGF complexes, the monomeric aflibercept:VEGF complex does not exhibit increased affinity for low-affinity Fcγ receptors, does not activate platelets, nor does it bind to the surface of epithelial or endothelial cells to a greater degree than unbound aflibercept or control Fc. The latter finding reflects the fact that aflibercept binds VEGF in a unique manner, distinct from antibodies not only blocking the amino acids necessary for VEGFR1/R2 binding but also occluding the heparin-binding site on VEGF165.

The Dll4/Notch pathway controls postangiogenic blood vessel remodeling and regression by modulating vasoconstriction and blood flow.

Blood vessel remodeling is crucial to the formation of the definitive vasculature, but little is known about the mechanisms controlling this process. We show that Delta-like ligand 4 (Dll4)/Notch pathway regulates vessel regression in normal pathologic conditions. Genetic and pharmacologic inhibition of Dll4/Notch prevented retinal capillary regression in the oxygen-induced retinopathy (OIR) model and during normal development. Deletion of the Notch-regulated ankyrin repeat protein, a negative regulator of the Notch pathway, produced an opposite phenotype. Inhibition of Dll4/Notch reduced vessel occlusion, maintaining blood flow that is essential for survival of microvessels. Dll4/Notch inhibition up-regulated the expression of vasodilators adrenomedullin and suppressed the expression of vasoconstrictor angiotensinogen. Angiotensin II induced rapid nonperfusion and regression of developing retinal capillaries, whereas Ace1 and AT1 inhibitors and adrenomedullin attenuated vasoobliteration in OIR, indicating that both pathways are involved in modulating vessel remodeling. In contrast, inhibition of vascular endothelial growth factor-A (VEGF-A) did not result in a pervasive loss of retinal capillaries, demonstrating that reduced expression of VEGF-A is not the proximate cause of capillary regression in OIR. Modulation of VEGF-A and Dll4/Notch signaling produced distinct changes in blood vessel morphology and gene expression, indicating that these pathways can have largely independent functions in vascular remodeling.

Inhibition of complement pathway activation with Pozelimab, a fully human antibody to complement component C5.

Complement is a key component of the innate immune system. Inappropriate complement activation underlies the pathophysiology of a variety of diseases. Complement component 5 (C5) is a validated therapeutic target for complement-mediated diseases, but the development of new therapeutics has been limited by a paucity of preclinical models to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) properties of candidate therapies. The present report describes a novel humanized C5 mouse and its utility in evaluating a panel of fully human anti-C5 antibodies. Surprisingly, humanized C5 mice revealed marked differences in clearance rates amongst a panel of anti-C5 antibodies. One antibody, pozelimab (REGN3918), bound C5 and C5 variants with high affinity and potently blocked complement-mediated hemolysis in vitro. In studies conducted in both humanized C5 mice and cynomolgus monkeys, pozelimab demonstrated prolonged PK and durable suppression of hemolytic activity ex vivo. In humanized C5 mice, a switch in dosing from in-house eculizumab to pozelimab was associated with normalization of serum C5 concentrations, sustained suppression of hemolytic activity ex vivo, and no overt toxicity. Our findings demonstrate the value of humanized C5 mice in identifying new therapeutic candidates and treatment options for complement-mediated diseases.

Performance analysis of 349-element adaptive optics unit for a coherent free space optical communication system.

As a continuation of our previous work [Optics Express.25, 15229(2017)] in which we have verified the performance of a coherent free space optical communication (FSOC) system with a 97-element adaptive optics (AO) system, in this paper, we evaluated the performance improvement of the coherent FSOC system using a large-scale high-speed AO system with a 349-element continuous surface deformable mirror. The mixing efficiency (ME) and bit-error-rate (BER) under different Greenwood frequency (GF) were calculated as the performance metric of coherent FSOC system. The performance of FSOC system using such a large-scale AO system was quantitatively verified for the first time. The obtained results showed that the performance was obviously improved when a larger-scale high-speed AO system is employed in coherent FSOC system. This analysis result provides a performance verification for large-scale high-speed AO systems used in FSOC system which is beneficial for coherent FSOC system parameters design.

Device design methodology and formulation of a protein therapeutic for sustained release intraocular delivery.

Despite years of effort, sustained delivery of protein therapeutics remains an unmet need due to three primary challenges - dose, duration, and stability. The work presented here provides a design methodology for polycaprolactone reservoir-based thin film devices suitable for long-acting protein delivery to the back of the eye. First, the challenge of formulating highly concentrated protein in a device reservoir was addressed by improving stability with solubility-reducing excipients. Next, predictive correlations between design parameters and device performance were developed to provide a methodology to achieve a target product profile. Prototype devices were designed using this methodology to achieve desired device size, release rate, therapeutic payload, and protein stability, assessed by in vitro studies. Finally, prototype tolerability was established in a non-human primate model. The design methodology presented here is widely applicable to reservoir-based sustained delivery devices for proteins and provides a general device design framework.

Aflibercept Action in a Rabbit Model of Chronic Retinal Neovascularization: Reversible Inhibition of Pathologic Leakage With Dose-Dependent Duration.

Purpose: We establish and characterize the chronic retinal neovascularization (RNV) induced by intravitreal (IVT) injection of DL-α-aminoadipic acid (AAA) in a rabbit model and investigate the extent and duration of inhibitory actions induced by IVT aflibercept on the RNV. Methods: Rabbits received a single IVT injection of AAA, with weekly follow-up fundus photography, fluorescein angiography (FA), and optical coherence tomography (OCT). After 10 weeks, they received a single IVT aflibercept or control injection. RNV leakage was quantified from FA by image analysis with Photoshop. Some eyes were collected for histologic analysis. Results: IVT AAA produced neuronal degeneration over a large fraction of the retina. RNV formed in the damaged area and by 10 weeks exhibited stable morphology and leakage, which persisted for at least 65 weeks. Control IVT injections did not affect RNV leakage, but IVT aflibercept completely blocked RNV leakage. The inhibition was reversible (i.e., the leakage returned as the drug cleared), and the duration of antileak effects with 500 µg aflibercept was approximately 8 weeks. Partial regression of the pathologic vasculature also occurred with aflibercept, with reestablishment as the drug cleared. Conclusions: This model mimics a chronic human disease in its stability and persistence, and the antileak action of aflibercept is fully reversible with a dose-dependent duration. Therefore, this large eye model is uniquely suitable for investigations into the efficacy and duration of action of novel formulations and pharmacotherapies for retinal vascular diseases, and for studying the underlying pathobiology of retinal angiogenesis.

VEGF-A stimulates lymphangiogenesis and hemangiogenesis in inflammatory neovascularization via macrophage recruitment.

Lymphangiogenesis, an important initial step in tumor metastasis and transplant sensitization, is mediated by the action of VEGF-C and -D on VEGFR3. In contrast, VEGF-A binds VEGFR1 and VEGFR2 and is an essential hemangiogenic factor. We re-evaluated the potential role of VEGF-A in lymphangiogenesis using a novel model in which both lymphangiogenesis and hemangiogenesis are induced in the normally avascular cornea. Administration of VEGF Trap, a receptor-based fusion protein that binds and neutralizes VEGF-A but not VEGF-C or -D, completely inhibited both hemangiogenesis and the outgrowth of LYVE-1(+) lymphatic vessels following injury. Furthermore, both lymphangiogenesis and hemangiogenesis were significantly reduced in mice transgenic for VEGF-A(164/164) or VEGF-A(188/188) (each of which expresses only one of the three principle VEGF-A isoforms). Because VEGF-A is chemotactic for macrophages and we demonstrate here that macrophages in inflamed corneas release lymphangiogenic VEGF-C/VEGF-D, we evaluated the possibility that macrophage recruitment plays a role in VEGF-A-mediated lymphangiogenesis. Either systemic depletion of all bone marrow-derived cells (by irradiation) or local depletion of macrophages in the cornea (using clodronate liposomes) prior to injury significantly inhibited both hemangiogenesis and lymphangiogenesis. We conclude that VEGF-A recruitment of monocytes/macrophages plays a crucial role in inducing inflammatory neovascularization by supplying/amplifying signals essential for pathological hemangiogenesis and lymphangiogenesis.

Intravitreal administration of erythropoietin and preservation of retinal ganglion cells in an experimental rat model of glaucoma.

PURPOSE: The aim of this pilot study was to evaluate the potential neuroprotective effect of an intravitreal injection of erythropoietin (EPO) on retinal ganglion cell (RGC) preservation in an episcleral vessel cautery-induced rat model of glaucoma. METHODS: The animals were randomly assigned into an unoperated control group (n = 11) and three experimental groups: episcleral vessel cautery only (EVC: n = 4), episcleral vessel cautery with intravitreal normal saline injection (EVC-NS; n = 5), and episcleral vessel cautery with intravitreal EPO treatment (EVC-EPO; n = 9). The intravitreal injections were limited to 5 mul containing either normal saline alone or 200 ng of EPO in normal saline administered immediately after the cautery procedure. RGCs were labeled retrogradely by FluoroGold neuron tracer 5 to 7 days prior to the collection of eyes at day 21 and counted in whole flat-mounted retinas with fluorescence microscopy. RESULTS: Compared to the RGC counts in retinal specimens from unoperated control rats (12,619 +/- 310), the corresponding RGC counts were significantly decreased in both the EVC (9116 +/- 273; p < 0.005) and EVC-NS (9489 +/- 293; p < 0.005) groups but not significantly decreased in the EVC-EPO (11,212 +/- 414; p = 0.051) treated retinas. CONCLUSIONS: A single intravitreal 200 ng dose of EPO appears to have a protective effect on RGC viability in an in vivo rat model of glaucoma. Further experimental studies are needed to confirm these preliminary results and to optimize the appropriate dose and frequency of EPO delivery in animal models of glaucoma.

Localization of VEGF receptor-2 (KDR/Flk-1) and effects of blocking it in oxygen-induced retinopathy.

PURPOSE: Vascular endothelial cell growth factor (VEGF) has been implicated in vascular development and in proliferative retinopathies. The goal of this study was to examine the immunohistochemical localization and relative levels of VEGF receptor-2 (KDR) in canine retina during postnatal vasculogenesis and during angiogenesis in oxygen-induced retinopathy (OIR) and to investigate the effects of neutralizing KDR on these processes. METHODS: Eyes from normal dogs ranging from 1 to 22 days of age and age-matched oxygen-treated animals were snap frozen for immunohistochemical analysis with antibodies against human KDR. To examine the effects of blocking KDR, 6-day-old air-reared control and oxygen-treated animals were surgically implanted with slow release polymer pellets containing control IgG or anti-KDR. Material eluted from pellets was assessed using a binding assay (measures binding to soluble KDR) to determine the kinetics of anti-KDR release and endothelial cell proliferation to measure bioactivity. Animals were killed at 22 days of age and tissues examined with adenosine diphosphatase (ADPase) histochemical staining of blood vessels. RESULTS: KDR immunoreactivity was only weakly associated with developing retinal vessels and was not observed in angioblasts throughout normal postnatal development. Immunoreactivity was very strong in reforming retinal vessels and intravitreal neovascularization in oxygen-treated animals. Anti-KDR had no effect on vessel morphology or growth in air-reared control animals. In oxygen-treated animals, anti-KDR significantly inhibited revascularization of the retina (P = 0.005) and formation of intravitreal neovascularization compared with control IgG pellet eyes (P < 0.04). CONCLUSIONS: KDR/Flk-1 was only weakly associated with normal developing primary retinal vessels but was strongly expressed by proliferating endothelial cells in reforming retinal vessels and intravitreal neovascularization after hyperoxic insult. Anti-KDR antibody delivered by slow-release pellets had no effect on normal vasculogenesis, but it inhibited the formation of intravitreal neovascularization and retinal vessel development in OIR. The study suggests that blocking KDR may be beneficial for treating pathologic angiogenesis in adult tissue.

Inhibition of hemangiogenesis and lymphangiogenesis after normal-risk corneal transplantation by neutralizing VEGF promotes graft survival.

PURPOSE: To evaluate the occurrence and time course of hem- and lymphangiogenesis after normal-risk corneal transplantation in the mouse model and to test whether pharmacologic strategies inhibiting both processes improve long-term graft survival. METHODS: Normal-risk allogeneic (C57BL/6 to BALB/c) and syngeneic (BALB/c to BALB/c) corneal transplantations were performed and occurrence and time course of hem- and lymphangiogenesis after keratoplasty was observed, by using double immunofluorescence of corneal flatmounts (with CD31 as a panendothelial and LYVE-1 as a lymphatic vascular endothelium-specific marker). A molecular trap designed to eliminate VEGF-A (VEGF Trap(R1R2); 12.5 mg/kg) was tested for its ability to inhibit both processes after keratoplasty and to promote long-term graft survival (intraperitoneal injections on the day of surgery and 3, 7, and 14 days later). RESULTS: No blood or lymph vessels were detectable immediately after normal-risk transplantation in either donor or host cornea, but hem- and lymphangiogenesis were clearly visible at day 3 after transplantation. Both vessel types reached donor tissue at 1 week after allografting and similarly after syngeneic grafting. Early postoperative trapping of VEGF-A significantly reduced both hem- and lymphangiogenesis and significantly improved long-term graft survival (78% vs. 40%; P < 0.05). CONCLUSIONS: There is concurrent, VEGF-A-dependent hem- and lymphangiogenesis after normal-risk keratoplasty within the preoperatively avascular recipient bed. Inhibition of hem- and lymphangiogenesis (afferent and efferent arm of an immune response) after normal-risk corneal transplantation improves long-term graft survival, establishing early postoperative hem- and lymphangiogenesis as novel risk factors for graft rejection even in low-risk eyes.

Ganglion cell responses to retinal light stimulation in the absence of photoreceptor outer segments from retinal degenerate rodents.

PURPOSE: To determine whether a severely degenerated retina without photoreceptor outer segments and a non-recordable electroretinogram (ERG) can still show retinal ganglion cell (RGC) responses to retinal light stimulation. METHODS: The authors measured ERGs and retinal surface RGC responses from six week old rd mice and three month old homozygous S334ter line3 rats. Animal eyes were also studied by light microscopy, transmission electron microscopy, and immunohistochemistry (rats). RESULTS: The corneal ERGs were non-recordable and no photoreceptor outer segments were found in either retinal degeneration model. A few cell bodies (without outer segments) that were immunoreactive for cone opsin and rhodopsin were found in the outer nuclear layer of the rats. Light-driven ON-RGC responses, however, were recordable from six week old rd mice. In addition, light-driven ON and OFF-RGC responses were recordable from three month old homozygous S334ter line 3 rats. CONCLUSIONS: This study suggests that despite the apparent absence of photoreceptor outer segments and a non-recordable ERG, ganglion cell responses to retinal light stimulation may remain preserved in some severe retinal degenerate transgenic rodents.

Prevention of experimental choroidal neovascularization and resolution of active lesions by VEGF trap in nonhuman primates.

OBJECTIVE: To evaluate the efficacy of systemic and intravitreous administration of VEGF Trap (aflibercept) in a nonhuman primate model of choroidal neovascularization (CNV). METHODS: VEGF Trap treatment on laser-induced CNV was evaluated in 48 adult cynomolgus monkeys. In the prevention arms of the study, VEGF Trap was administered by intravenous injection (3 or 10 mg/kg weekly) or intravitreous injection (50, 250, or 500 µg/eye every 2 weeks) beginning before laser injury. In the treatment arm, a single intravitreous injection (500 µg) was given 2 weeks following laser injury. Laser-induced lesions were scored from grade 1 (no hyperfluorescence) to grade 4 (clinically relevant leakage). Representative lesions were evaluated histologically. RESULTS: Grade 4 leakage developed at 32.4% and 45.4% of the laser sites in animals receiving intravitreous or intravenous administration of placebo at 2 weeks following laser injury, respectively. In contrast, the development of grade 4 lesions was completely or nearly completely prevented in all groups receiving intravenous or intravitreous injections of VEGF Trap. A single intravitreous injection of VEGF Trap (500 µg) administered following the development of CNV reduced the frequency of grade 4 lesions from 44.4% to 0% within 14 days of treatment. Intravitreous VEGF Trap was well tolerated with either no or only mild ocular inflammation. Histological evaluation showed decreased scores for morphologic features of tissue proliferation in the VEGF Trap prevention groups. CONCLUSIONS: VEGF Trap prevented the development of clinically relevant CNV leakage when administered at the lowest doses tested. Moreover, a single intravitreous injection induced inhibition of active CNV leakage. CLINICAL RELEVANCE: The animal model used in this study has an established track record as a predictor of pharmacologic efficacy of antineovascular drugs in humans having the neovascular, or wet, form of age-related macular degeneration.

A subretinal matrigel rat choroidal neovascularization (CNV) model and inhibition of CNV and associated inflammation and fibrosis by VEGF trap.

PURPOSE: The exudative, or the wet form of age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). A subretinal Matrigel (BD Biosciences, Bedford MA) model of CNV is described here, along with the effects of vascular endothelial growth factor (VEGF) neutralization on the development of CNV and associated inflammation and fibrosis. METHODS: CNV was induced in adult Sprague-Dawley rats by subretinal injection of Matrigel. CNV growth and associated leukocyte infiltration and collagen deposition were examined. VEGF Trap (Regeneron Pharmaceuticals, Tarrytown, NY), a recombinant protein that comprises portions of the extracellular domains of VEGF receptors 1 and 2 and that binds all isoforms of VEGF-A as well as placental growth factor with high affinity, was administered subcutaneously. RESULTS: Initiation of CNV was detected 4 days after Matrigel injection and then increased progressively in size. Systemic administration of VEGF Trap beginning on day 2 and 6 completely prevented development of CNV. When CNV was allowed to develop for 10 days before treatment was initiated, VEGF Trap not only prevented its further progression, but also induced substantial regression of existing lesions. In addition, VEGF Trap treatment reduced the total lesion volume and largely prevented the progressive leukocyte infiltration and fibrosis associated with CNV. CONCLUSIONS: The subretinal Matrigel CNV model provides a convenient tool for the study of the diverse components of complex CNV lesions. The data not only confirm the critical roles of VEGF in the development and maintenance of CNV, but further demonstrate that VEGF and other VEGF receptor 1 ligands promote CNV-associated inflammation and fibrosis.