Treatment of age-related macular degeneration

Nanotechnology for Omics-Based Ocular Drug Delivery

Millions of people suffer from ocular diseases that impair vision and can lead to blindness. Advances in genomics and proteomics have revealed a number of different molecular markers specific for different ocular diseases, thereby optimizing the processes of drug development and discovery. Nanotechnology can increase the throughput of data obtained in omics-based studies and allows for more sensitive diagnostic techniques as more efficient drug delivery systems. Biocompatible and biodegradable nanomaterials developed through omics-based research are able to target reported molecular markers for different ocular diseases and offer novel alternatives to conventional drug therapy. In this chapter, the authors review the pathophysiology, current genomic and proteomic information, and current nanomaterial-based therapies of four ocular diseases: glaucoma, uveal melanoma, age-related macular degeneration, and diabetic retinopathy. Omics-based research can be used to elucidate specific genes and proteins and develop novel nanomedicine formulations to prevent, halt, or cure ocular diseases at the transcriptional or translational level.

Nanotechnology for Omics-Based Ocular Drug Delivery

Millions of people suffer from ocular diseases that impair vision and can lead to blindness. Advances in genomics and proteomics have revealed a number of different molecular markers specific for different ocular diseases, thereby optimizing the processes of drug development and discovery. Nanotechnology can increase the throughput of data obtained in omics-based studies and allows for more sensitive diagnostic techniques as more efficient drug delivery systems. Biocompatible and biodegradable nanomaterials developed through omics-based research are able to target reported molecular markers for different ocular diseases and offer novel alternatives to conventional drug therapy. In this chapter, the authors review the pathophysiology, current genomic and proteomic information, and current nanomaterial-based therapies of four ocular diseases: glaucoma, uveal melanoma, age-related macular degeneration, and diabetic retinopathy. Omics-based research can be used to elucidate specific genes and proteins and develop novel nanomedicine formulations to prevent, halt, or cure ocular diseases at the transcriptional or translational level.

Photoreceptor degeneration and retinal inflammation induced by very low-density lipoprotein receptor deficiency

Our previous studies have shown that very low-density lipoprotein receptor (VLDLR) is a negative regulator of the Wnt pathway. The present study showed that VLDLR gene knockout (Vldlr(-/-)) mice displayed impaired cone ERG responses at early ages. Immunostaining of mid-wavelength cones showed significantly decreased cone densities in the retina and shortened cone outer segments in Vldlr(-/-) mice. At older ages, Vldlr(-/-) mice displayed declined rod ERG responses, decreased layers of photoreceptor nuclei, reduced rhodopsin levels and decreased levels of 11-cis retinal, the chromophore of visual pigments. As shown by fluorescein angiography and permeability assay, Vldlr(-/-) mice had severe retinal vascular leakage. ZO-1, a tight junction protein, was down-regulated in Vldlr(-/-) mouse retinae, further supporting the impaired blood-retinal barrier. Double staining of pericytes and endothelial cells in retinal sections revealed that neovasculature in Vldlr(-/-) mice lacks pericyte coverage, suggesting impaired maturation of retinal vasculature in Vldlr(-/-) mice. Staining of adherent leukocytes in the retinal vasculature revealed significant leukostasis in Vldlr(-/-) mice. Moreover, Vldlr(-/-) mice displayed up-regulated expression of multiple pro-inflammatory factors and activated NF-kappaB and HIF-1 alpha, key regulators of inflammation. These findings suggest that deficiency of VLDLR leads to retinal degeneration and inflammation.

Micro-scale thermal tissue gripper

During eye surgery translocating a graft of retinal tissue without damaging the vulnerable top layer is highly problematic using the currently available instruments. This study presents indirect Heat Induced Attachment and Detachment (HIAD) as a new concept for single side attachment of tissue to, and detachment from a heated metal wire. A small-scale prototype was built, having a 50 mum molybdenum wire that could be heated via an electric current. Tests (n = 60) were performed on submerged chicken meat to study the attachment and detachment properties of the prototype at different electric signal lengths. A 9V signal was applied to the prototype, with amplifier input signal lengths varying from 0.6-1.5 ms. Voltages and currents were sampled at 250 kHz to obtain energies. Both attachment and detachment occurred with 98% and 90% certainty, respectively, supplying 41 and 110 mJ of energy to the prototype in 0.7 and 1.5 ms. The attachment strength was estimated at 0.2 mN. Visible damage appeared to be approximately 0.005 mm(2). The concept of indirect heating of the instrument-tissue interface proved to be effective as the prototype could induce attachment and detachment of tissue. Indirect HIAD may be applicable in many different surgical applications.

Macular pigment: new clinical methods of detection and the role of carotenoids in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in people over the age of 65. The Age-Related Eye Disease Study (AREDS) suggests antioxidants may delay the advance of age-related macular degeneration. The macular pigments zeaxanthin and lutein may serve as antioxidants as well as blue filter to protect the retina. In this review, the general characteristics of macular pigment are described. The nutritional value of zeaxanthin/lutein and methods to assess macular pigment are discussed. Several emerging instruments to assess macular pigment, including heterochromatic flickering photometer, motion detection photometer, fundus reflectance spectroscope, Raman spectrometer, and autofluorescence spectrometry, are introduced and reviewed. Optometrists should be aware that they may play a role to assess and monitor the risk of AMD. There is an opportunity to incorporate measurement of macular pigment in optometric practice.

Selection of dosing regimen with WST11 by Monte Carlo simulations, using PK data collected after single IV administration in healthy subjects and population PK modeling

WST11, a novel generation of photo sensitizers to be used for vascular-targeted phototherapy (VTP), is effective at short interval between injection and illumination and it is expected to enable selective destruction of neovasculature with minimal side effects or skin photo toxicity. This study was conducted to evaluate the clinical and laboratory safety, tolerability and pharmacokinetic profile of WST11 given as a single intravenous administration (1.25, 2.5, 5, 7.5, 10, or 15 mg/kg) during an escalating dose study in healthy male subjects. This article describes WST11 population pharmacokinetic modeling and simulations performed to optimize the IV infusion-dosing regimen in combination with illumination, the target PK profile being plateau concentrations during approximately 30 min. The study included 42 healthy male subjects, administered 1.25, 2.5, 5, 7.5, 10, or 15 mg/kg as a 10-min IV infusion. A population pharmacokinetic model was developed using nonlinear mixed effects modeling (NONMEM). Monte Carlo simulations of the population PK dataset (NONMEM) were performed to select series of dosing regimen which would result in a plateau of concentration lasting at least 30 min and allow laser illumination. A two-compartment model with nonlinear elimination best described the data. No demographic factor was shown to affect the WST11 pharmacokinetics. The clearance was shown to decreases with the dose administered, ranging from 6 L/h (dose of 79 mg) to 2 L/h (dose of 1110 mg). The duration of the infusion was estimated at 12 min. The volume of distribution of the central compartment was 3 L and the volume of the peripheral compartment was 1.15 L. The apparent inter-compartmental clearance was 0.137 L/h. The between subjects variability on clearance and on volume was low. Residual variability was moderate with a CV of 21%. Due to the dose effect on clearance and the rapid elimination, simulations showed that different dosing inputs are necessary: for 5 and 10 mg/kg BW, a sufficiently good dosing scenario is to administer 80% of the dose over 5 min, 15% over 10 min and the remaining 5% over 10 min. For lower doses, the sequence 70% in 5 min/20% in 10 min/10% in 10 min is preferable. The pharmacokinetic profile of WST11 by IV administration would allow a treatment by laser illumination in good clinical conditions using controlled infusions. The study results do not indicate that the dose should be adjusted for body size. The only factor that determines the drug input profile is the dose level, since the elimination half-life decreases when the dose administered increases. The use of the population PK model for simulations has shown that, at dose level of 5 mg/kg or more, a loading dose of 80% dose given over 5 min followed by 15% of dose during 10 min and remained dose to give over 10 min would result in a favorable PK profile.

A microfabricated scaffold for retinal progenitor cell grafting

Diseases that cause photoreceptor cell degeneration afflict millions of people, yet no restorative treatment exists for these blinding disorders. Replacement of photoreceptors using retinal progenitor cells (RPCs) represents a promising therapy for the treatment of retinal degeneration. Previous studies have demonstrated the ability of polymer scaffolds to increase significantly both the survival and differentiation of RPCs. We report the microfabrication of a poly(glycerol-sebacate) scaffold with superior mechanical properties for the delivery of RPCs to the subretinal space. Using a replica molding technique, a porous poly(glycerol-sebacate) scaffold with a thickness of 45 microm was fabricated. Evaluation of the mechanical properties of this scaffold showed that the Young's modulus is about 5-fold lower and the maximum elongation at failure is about 10-fold higher than the previously reported RPC scaffolds. RPCs strongly adhered to the poly(glycerol-sebacate) scaffold, and endogenous fluorescence nearly doubled over a 2-day period before leveling off after 3 days. Immunohistochemistry revealed that cells grown on the scaffold for 7 days expressed a mixture of immature and mature markers, suggesting a tendency towards differentiation. We conclude that microfabricated poly(glycerol-sebacate) exhibits a number of novel properties for use as a scaffold for RPC delivery.

AQ4, an antitumor anthracenedione, inhibits endothelial cell proliferation and vascular endothelial growth factor secretion: implications for the therapy of ocular neovascular disorders

Current clinical options for the treatment of neovascular disorders of the posterior segment of the eye have several drawbacks. Photocoagulation lasers can impair peripheral and night vision. Photodynamic therapies as well as intravitreal macromolecule injections (Macugen and Lucentis) require frequent, invasive administrations. Above all, only modest improvement in vision is achieved with any of the existing treatments. In order to overcome these limitations in the long run, this study investigated the antiangiogenic potential of AQ4, a low molecular weight anthracenedione. The results indicate that AQ4 enters the cell nucleus and inhibits proliferation of choroid-retina endothelial (RF/6A) cells and human retinal pigment epithelial (ARPE-19) cells under hypoxic (1% O(2)) as well as normoxic (21% O(2)) conditions. The IC(50) for these effects ranges from 5.5 to 6.9 muM. AQ4 does not affect the viability of non-dividing RF/6A or ARPE-19 cells up to 0.1 mM. Further, AQ4 (20 muM) reduces vascular endothelial growth factor (VEGF) protein secretion by about 50% in ARPE-19 cells under normoxia as well as hypoxia, possibly by reducing VEGF transcription. AQ4 arrests the growth of endothelial cells in S phase, consistent with interference of AQ4 with DNA replication. These results for the first time suggest that AQ4 can potentially alleviate the neovascularization of choroid/retina by a dual mechanism of inhibiting the proliferation of endothelial cells and by reducing mitogenic VEGF stimulus from retinal pigment epithelial cells.

A review of drug options in age-related macular degeneration therapy and potential new agents

Age-related macular degeneration (AMD) is the leading cause of legal blindness in people > 50 years of age in the developed world. AMD is both a debilitating and costly disease for the individual and the community. Greater understanding of the mechanisms and pathways involved in causing the visual loss in AMD has resulted in the advent of several newer and more effective treatment options, making it an exciting time in the management of AMD. This paper will examine the principles behind the existing drug therapies available, as well as those being developed in the management or prophylaxis of AMD and its vision-threatening complications.

Impact of age related macular degeneration on quality of life

AIMS

To describe the impact of age related macular degeneration (AMD) on quality of life and explore the association with vision, health, and demographic variables.

METHODS

Adult participants diagnosed with AMD and with impaired vision (visual acuity <6/12) were assessed with the Impact of Vision Impairment (IVI) questionnaire. Participants rated the extent that vision restricted participation in activities affecting quality of life and completed the Short Form General Health Survey (SF-12) and a sociodemographic questionnaire.

RESULTS

The mean age of the 106 participants (66% female) was 83.6 years (range 64-98). One quarter had mild vision impairment, (VA<6/12-6/18) and 75% had moderate or severely impaired vision. Participants reported from at least "a little" concern on 23 of the 32 IVI items including reading, emotional health, mobility, and participation in relevant activities. Those with mild and moderate vision impairment were similarly affected but significantly different from those with severe vision loss (p<0.05). Distance vision was associated with IVI scores but not age, sex, or duration of vision loss.

CONCLUSION

AMD affects many quality of life related activities and not just those related to reading. Referral to low vision care services should be considered for people with mild vision loss and worse.