Preventive versus treatment effect of AG3340, a potent matrix metalloproteinase inhibitor in a rat model of choroidal neovascularization

Effects of slit lamp-delivered retinal laser photobiomodulation in a rat model of choroidal neovascularization

Neovascular age-related macular degeneration, also known as exudative or wet age-related macular degeneration, is the leading cause of blindness in the developed world. Photobiomodulation has the potential to target the up-stream hypoxic and pro-inflammatory drivers of choroidal neovascularization. This study investigated whether photobiomodulation attenuates characteristic pathological features of choroidal neovascularization in a rodent model. Experimental choroidal neovascularization was induced in Brown Norway rats with laser photocoagulation. A custom-designed, slit-lamp-mounted, 670 nm laser was used to administer retinal photobiomodulation every 3 days, beginning 6 days prior to choroidal neovascularization induction and continuing until the animals were killed 14 days later. The effect of photobiomodulation on the size of choroidal neovascular membranes was determined using isolectin-B4 immunohistochemistry and spectral domain-optical coherence tomography. Vascular leakage was determined with fluorescein angiography. The effect of treatment on levels of vascular endothelial growth factor expression was quantified with enzyme-linked immunosorbent assay. Treatment with photobiomodulation was associated with choroidal neovascular membranes that were smaller, had less fluorescein leakage, and a diminished presence of inflammatory cells as compared to sham eyes. These effects were not associated with a statistically significant difference in the level of vascular endothelial growth factor when compared to sham eyes. The data shown herein indicate that photobiomodulation attenuates pathological features of choroidal neovascularization in a rodent model by mechanisms that may be independent of vascular endothelial growth factor.

Matrix Metalloproteinases in Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is a complex, multifactorial and progressive retinal disease affecting millions of people worldwide. In developed countries, it is the leading cause of vision loss and legal blindness among the elderly. Although the pathogenesis of AMD is still barely understood, recent studies have reported that disorders in the regulation of the extracellular matrix (ECM) play an important role in its etiopathogenesis. The dynamic metabolism of the ECM is closely regulated by matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs). The present review focuses on the crucial processes that occur at the level of the Bruch’s membrane, with special emphasis on MMPs, TIMPs, and the polymorphisms associated with increased susceptibility to AMD development. A systematic literature search was performed, covering the years 1990–2020, using the following keywords: AMD, extracellular matrix, Bruch’s membrane, MMPs, TIMPs, and MMPs polymorphisms in AMD. In both early and advanced AMD, the pathological dynamic changes of ECM structural components are caused by the dysfunction of specific regulators and by the influence of other regulatory systems connected with both genetic and environmental factors. Better insight into the pathological role of MMP/TIMP complexes may lead to the development of new strategies for AMD treatment and prevention.

Age-related Macular Degeneration: Current Knowledge of Zinc Metalloproteinases Involvement

BACKGROUND

Advanced age-related macular degeneration (AMD) is the leading cause of blindness in the elderly with limited therapeutic options. The disease is characterized by photoreceptor loss in the macula and reduced Retinal Pigment Epithelium (RPE) function, associated with matrix degradation, cell proliferation, neovascularization and inflammation. Matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases (ADAMs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) play a critical role in the physiology of extracellular matrix (ECM) turnover and, in turn, in ECM pathologies, such as AMD. A balance between the activities of MMPs and Tissue Inhibitors of Metalloproteinase (TIMPs) is crucial for the integrity of the ECM components; indeed, a dysregulation in the ratio of these factors produces profound changes in the ECM, including thickening and deposit formation, which eventually might lead to AMD development.

OBJECTIVE

This article reviews the relevance and impact of zinc metalloproteinases on the development of AMD and their roles as biomarkers and/or therapeutic targets. We illustrate some studies on several inhibitors of MMPs currently used to dissect physiological properties of MMPs. Moreover, all molecules or technologies used to control MMP and ADAM activity in AMD are analyzed.

CONCLUSION

This study underlines the changes in the activity of MMPs expressed by RPE cells, highlights the functions of already used MMP inhibitors and consequently suggests their application as therapeutic agents for the treatment of AMD.

Matrix Metalloproteinases and Glaucoma Treatment

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade extracellular matrix (ECM) components such as collagen and have important roles in multiple biological processes, including development and tissue remodeling, both in health and disease. The activity of MMPs is influenced by the expression of MMPs and tissue inhibitors of metalloproteinase (TIMPs). In the eye, MMP-mediated ECM turnover in the juxtacanalicular region of the trabecular meshwork (TM) reduces outflow resistance in the conventional outflow pathway and helps maintain intraocular pressure (IOP) homeostasis. An imbalance in the MMP/TIMP ratio may be involved in the elevated IOP often associated with glaucoma. The prostaglandin analog/prostamide (PGA) class of topical ocular hypotensive medications used in glaucoma treatment reduces IOP by increasing outflow through both conventional and unconventional (uveoscleral) outflow pathways. Evidence from in vivo and in vitro studies using animal models and anterior segment explant and cell cultures indicates that the mechanism of IOP lowering by PGAs involves increased MMP expression in the TM and ciliary body, leading to tissue remodeling that enhances conventional and unconventional outflow. PGA effects on MMP expression are dependent on the identity and concentration of the PGA. An intracameral sustained-release PGA implant (Bimatoprost SR) in development for glaucoma treatment can reduce IOP for many months after expected intraocular drug bioavailability. We hypothesize that the higher concentrations of bimatoprost achieved in ocular outflow tissues with the implant produce greater MMP upregulation and more extensive, sustained MMP-mediated target tissue remodeling, providing an extended duration of effect.

New model of proliferative vitreoretinopathy in rabbit for drug delivery and pharmacodynamic studies

Blinding retinal diseases become more epidemic as the population ages. These diseases, such as diabetic retinopathy and macular edema, are of chronic nature and require protracted drug presence at the disease site. A sustained intravitreal porous silicon delivery system with dexamethasone (pSiO₂-COO-DEX) was evaluated in a new rabbit model of proliferative vitreoretinopathy (PVR) in a real treatment design. In contrast to the pretreatment design model, pSiO₂-COO-DEX was intravitreally injected into the eyes with active inflammation. Subretinal injection of vascular endothelial growth factor (VEGF) and Matrigel induced a late-onset vitreoretinal inflammation that gradually developed into PVR. This method mimics the human disease better than PVR induced by either intravitreal cell injection or trauma. The pSiO₂-COO-DEX intervened eyes had minimal PVR, while balanced saline solution or free dexamethasone intervened eyes had significantly more PVR formation. In addition, adding VEGF to the Matrigel for subretinal injection induced greater inflammation and retinal neovascularization in comparison to only Matrigel injected under the medullary ray. Clinical and pathological examinations, including fundus fluorescein angiography and optical coherence tomography, confirmed these changes. In the current study, neither subretinal injection of Matrigel or subretinal injection of VEGF and Matrigel induced choroidal neovascularization. However, the current PVR model demonstrates a chronic course with moderate severity, which may be useful for drug screening studies.

A novel lipid prodrug strategy for sustained delivery of hexadecyloxypropyl 9-[2-(phosphonomethoxy)ethyl]guanine (HDP-PMEG) on unwanted ocular proliferation

Proliferative vitreoretinopathy (PVR) is a blinding eye disease and there is no effective pharmacological measure to prevent PVR development. The difficulty comes from lack of potent antiproliferative agent and lack of sustained delivery to cover high-risk time window for PVR to develop. Lipid prodrug of PMEG, hexadecyloxypropyl 9-[(2-phosphonomethoxy)ethyl]guanine (HDP-PMEG), was prepared and was evaluated as a pharmacological adjuvant to surgical management of PVR. A dose-escalation study determined that the highest nontoxic dose for intravitreal use in pigmented rabbits was 3 µg per eye. The genotoxicity of HDP-PMEG was harnessed as a perioperative preventative measure against PVR in a rabbit eye model while the sustained intravitreal pharmacological effect was evaluated on a laser-induced fibrovascular model in rat eye. After intravitreal 3 µg, HDP-PMEG particles in the rabbit vitreous was visible for at least 6 weeks. A single 50-min intravitreal infusion of HDP-PMEG demonstrated significant inhibition of PVR formation when compared with the eyes infused with only BSS (BSS vs. HDP-PMEG: estimate = 1.14, OR = 3.1, p = .027). A single intravitreal 104 ng (equivalent to 3 µg for rabbit eye) of HDP-PMEG significantly inhibit laser-induced fibrovascular proliferation in rat eye by 55% (least square mean pixel, BSS = 4763569.5 vs. HDP-PMEG = 2148129.7, p < .0001, generalized estimating equation [GEE]). Retinal fluorescein angiography showed the odds for BSS intervened eyes to have higher-rated FA leaking grades were 38.5 times compared with HDP-PMEG treated eyes (p < .0001, GEE). Our study results indicate that single intravitreal HDP-PMEG may be a promising ocular drug delivery as a perioperative intervention to prevent PVR reoccurrence following primary surgical management.

Heparanase-1 activities in the development of laser induced choroidal neovascularization

AIM

To investigate the role of heparanase-1 in laser-induced choroidal neovascularization (CNV).

METHODS

Experimental CNV was induced by krypton laser photocoagulation in 15 male Brown Norway rats. Fundus fluorescein angiography and histopathological examination were performed in observing the CNV development. The expression and distribution of heparanase-1 protein in the laser lesions were determined by immunohistochemistry and western blotting analysis.

RESULTS

The success rate of laser induced CNV was approximately 75% on 3-4 weeks after laser photocoagulation. The protein levels of heparanase-1 increased significantly in the retina-choroidal complex of CNV models when compared to normal rat eyes (P<0.01). Immunostaining confirmed strong heparanase-1 expressions in all laser lesions, and it displayed to be highest at the newly formed blood vessels within the fibrovascular complex in the subretinal space.

CONCLUSION

Heparanase-1 is closely involved in the development of laser induced CNV.

Increase in matrix metalloproteinase-2 level in the chicken retina after laser photocoagulation

BACKGROUND AND OBJECTIVE

We investigated the levels of matrix metalloproteinase-2 (MMP-2), which has been implicated in various vitreoretinal diseases, in the retina after laser photocoagulation (LPC).

MATERIALS AND METHODS

The time course of MMP-2 expression in 2-day-old chicken retinas before and 6 hours, 12 hours, 1 day, 2 days, 4 days, 8 days, 16 days, and 32 days after LPC was determined by real-time PCR and gelatin zymography. The basal level of MMP-2 in the retina and vitreous was also measured by gelatin zymography. MMP-2 localization in the retina was examined by immunohistochemistry. The localization of MMP-2 mRNA was determined by fluorescent in situ hybridization. The internal limiting membrane (ILM) was observed by scanning electron microscopy.

RESULTS

MMP-2 mRNA expression in the retina peaked at day 4, but gelatin zymography showed that MMP-2 peaked 6 hours after LPC and the significant increase in the level of active MMP-2 lasted for more than 4 days. The concentration of MMP-2 in the vitreous was significantly higher than that in the retina. A distinct MMP-2 signal around the ILM was identified 6 hours after LPC, but MMP-2 mRNA was not detected there. Electron microscopy showed a damaged retinal surface after LPC.

CONCLUSION AND OUTLOOK

The significant increase in retinal MMP-2 which lasted for more than 4 days after LPC may be induced by influx from the vitreous into the retina. This MMP-2 dynamics may contribute to pathological processes in the retina after LPC.

In vitro and in vivo matrix metalloproteinase expression after photodynamic therapy with a liposomal formulation of aminolevulinic acid and its methyl ester

Photodynamic therapy (PDT) is a well-known method for the treatment of malignant tumors, and its principles have been well established over the past 30 years. This therapy involves the application of a chemical called a photosensitizer and its subsequent excitation with light at the appropriate wavelength and energy. Topical photodynamic therapy with aminolevulinic acid (5-ALA) is an alternative therapy for many malignant processes, including nonmelanoma skin cancers such as basal-cell carcinoma (BCC). Our novel approach for this study was to use a liposomal formulation of 5-ALA and its methyl ester (commercially available as metvix) both in vitro and in vivo, and to check whether the liposome-entrapped precursors of photosensitizers can induce the expression of metalloproteinases (MMPs) in animal tumor cells and in other tissues from tumor-bearing rats and in selected cell lines in vitro. We also checked whether the application of tissue inhibitors of matrix metalloproteinases (TIMPs) has any effect on MMPs in the above-mentioned experimental models, and if they can cause complete inhibition of MMP expression. Immunohistochemical studies revealed that after the PDT, the intensity of expression of MMPs in healthy animals was very low and seen in single cells only. After the PDT in tumor-bearing rats, MMP-3 was expressed in the tumor cells with the highest intensity of staining in the tissues directly adjacent to the tumors, while MMP-2 and -9 were not found. In the control groups, there was no observed expression of MMPs. In vitro studies showed that MMP-3 was expressed in MCF-7 cells after PDT, but MMP-9 was not observed and MMP-2 was only seen in single cases. Our studies confirmed that the application of an MMP-3 inhibitor may block an induction of MMP-3 expression which had previously been initiated by PDT. The preliminary data obtained from cancer patients revealed that new precursors are effective in terms of PDT, and that using MMP inhibitors should be considered as a potential enhancing factor in clinical PDT.

AHI1 is required for photoreceptor outer segment development and is a modifier for retinal degeneration in nephronophthisis

Photoreceptor degeneration is a common feature of ciliopathies, owing to the importance of the highly specialized ciliary structure of these cells. Absence of AHI1, which encodes a cilium-localized protein, has been shown to cause a form of Joubert syndrome highly penetrant for retinal degeneration1,2. We show that Ahi1 knockout mice fail to form outer segments (OS), and show abnormal distribution of opsin throughout photoreceptors. Apoptotic cell death occurs rapidly between 2-4 weeks of age and is significantly delayed by reduced dosage of opsin. This phenotype also displays dosage-sensitive genetic interactions with Nphp1, another ciliopathy gene. Although not a primary cause of retinal blindness in humans, an allele of AHI1 modifies the relative risk of retinal degeneration greater than 7 fold within a nephronophthisis cohort. Our data support context-specific roles for AHI1 as a contributor to retinopathy and may explain a proportion of the variability of retinal phenotypes observed in nephronophthisis.

Toxicity and intraocular properties of a novel long-acting anti-proliferative and anti-angiogenic compound IMS2186

PURPOSE

To investigate the intraocular properties and toxicity of IMS2186, a small molecule developed as an anti-choroidal neovascularization (anti-CNV) drug.

MATERIALS AND METHODS

Cellular toxicity and mechanism of action was tested on cell lines in vitro. Intraocular studies used rabbits for drug dissolution as well as toxicity and rats for the treatment study as well as the toxicity confirmation study. Rabbits' eyes were injected with 2.5 mg of IMS2186 and observed for 36 weeks. Laser-induced CNV in rats was treated with IMS2186, Kenalog, or phosphate-buffered saline (pBS). Fluorescein angiography (FA) and immunohistochemical processing of the globes was performed.

RESULTS

The anti-proliferative IC(50) of IMS2186 for human fibroblast cells was 1.0-3.0 microM and 0.3-3.0 microM for human cancer cells; the IC(50) of IMS2186 to inhibit endothelial tube formation was 0.1-0.3 microM. The IC(50) of IMS2186 for inhibiting the production of pro-inflammatory cytokines was 0.3-1 microM. The IC(50) of IMS2186 for inhibiting macrophage migration was 1 micrM. These biological properties were not species specific. IMS2186 can be formulated as a suspension for long-lasting release and when delivered intraocularly, no intraocular toxicity was observed by slit lamp exam, fundus exam, intraocular pressure measurements, or by electroretinography. FA showed a reduction in the leakage in eyes treated with IMS2186 and triamcinolone acetonide; DAPI staining also showed significantly less cellularity in IMS2186-treated lesions as compared to PBS (p = 0.0025).

CONCLUSION

IMS2186 may be a safe intraocular therapeutic agent for intraocular proliferation and angiogenesis.

The role of vascular endothelial growth factor and other endogenous interplayers in age-related macular degeneration

Age-related macular degeneration (AMD) is a multifaceted disease characterized by early subclinical changes at the choroidea-retinal pigment epithelium interface. Both the causal and formal pathogenesis of the disease is still puzzling. Similarly, the reason for progression into two distinct late forms which are "geographic atrophy" and "choroidal neovascularization" remains enigmatic. Late changes are usually responsible for the dramatic loss in central function that has a devastating effect on quality of life. In industrialized countries the disease is a major cause for visual disability among persons over 60 years of age. Due to demographic right-shift and increased life expectancy, AMD is not only a medical problem but will have a pronounced socio-economic effect. Neovascular AMD with the development of choroidal neovascularization in the macular area accounts for 80% of the severe loss of visual acuity due to AMD. In the last decades, treatment modes were merely based on the destruction or surgical removal of the neovascular complex. In the present, however, the philosophical approach to treat the disease is changing to a pathology modifying manner. Intelligent targeting of the involved relevant factors and pathways should stop disease progression, reduce complications and improve vision. The first step into this new era has been accomplished with the introduction of antiangiogenic agents. The new agents act either directly on vascular endothelial growth factor (VEGF) or indirectly on its functional cascade. VEGF makes a fundamental contribution to neovascular processes but it also acts in physiological pathways. The main purpose of this review is to summarize its physiological role especially within the eye, the role in the development of AMD and to understand and foresee both the benefits and potential side-effects of the anti-VEGF-based therapy.

Correlation of the extent and duration of rhegmatogenous retinal detachment with the expression of matrix metalloproteinases in the vitreous

BACKGROUND

Investigation of the activity of matrix metalloproteinase (MMP)-2 and -9 and protein levels of MMP-1, -3, -8, and the tissue inhibitor of MMPs (TIMP)-1 in the vitreous of patients with rhegmatogenous retinal detachment (RRD) and establishment of potential correlations of MMPs with clinical parameters.

METHODS

Thirty-two vitreous samples from patients with RRD and 9 vitreous samples from human organ donors (controls) were assayed for MMP-1,-3, -8, and TIMP-1 levels using enzyme-linked immunosorbent assay and MMP-2 and -9 activity employing gelatin zymography.

RESULTS

MMP-1, MMP-3, proMMP-2, proMMP-9, MMP-9, and TIMP-1 were higher in vitreous from patients with RRD as compared to organ donors. Overall, MMPs and TIMPs were differentially expressed in vitreous from RRD with respect to the duration and extent of RRD. Regression analysis for all data indicated that a model consisting of MMP-2 and TIMP-1 could estimate the extent of RRD.

CONCLUSION

Levels of MMPs and TIMP-1 studied are elevated in vitreous during RRD. MMP-2 and TIMP-1 may have a more prominent and persistent role than other MMPs in the wound healing process of the retina during RRD. A regression model consisting of MMP-2 and TIMP-1 may prove to be of potential use in providing information for the evaluation of the extent of RRD.

Strategies for blocking angiogenesis in diabetic retinopathy: from basic science to clinical practice

Proliferative diabetic retinopathy (PDR) demands both more effective and less expensive biologically based treatments. Our understanding of the pathophysiology of the disease is increasing as new biochemical pathways are identified. Most reports emphasize proangiogenic stimuli, with the natural inhibitory elements receiving little attention. There are two therapeutic strategies for blocking retinal angiogenesis in PDR: systemic drug administration (protein kinase C inhibitors and somatostatin analogs) or local therapies (anti-vascular endothelial growth factor strategies, anti-inflammatory agents, gene therapy and stem cell therapy). This review mainly focuses on the role of local therapies, especially intravitreous delivery, in the management of PDR. The potential for adverse effect are also discussed. The availability of these new strategies or the combination of them will not only be beneficial in treating PDR but may also result in a shift towards treating earlier stages of diabetic retinopathy, thus easing the burden of this devastating disease.

Matrix metalloproteinases in human choroidal neovascular membranes excised following verteporfin photodynamic therapy

AIM

To evaluate expression of proangiogenic matrix metalloproteinases (MMP) 2 and 9 at distinct intervals after verteporfin photodynamic therapy (PDT) in human choroidal neovascular membranes (CNV) secondary to age-related macular degeneration (AMD).

METHODS

Retrospective review of an interventional case series of 49 patients who underwent removal of CNV. Twenty-six patients were treated with PDT 3 to 383 days prior to surgery. Twenty-three CNV without previous treatment were used as controls. CNV were stained for CD34, cytokeratin 18, endostatin, MMP-2 and MMP-9 by immunohistochemistry.

RESULTS

CNV without previous therapy disclosed MMP-2, MMP-9 in RPE-Bruch's membrane, vessels and stroma in different intensities. Three days after PDT, MMP-9 expression was significantly weaker in stroma (p = 0.0019). Endostatin was significantly reduced in vessels (p<0.001). At longer post-PDT intervals, a significant increase of MMP-9 in stroma (p = 0.037) and of endostatin in RPE-Bruch's membrane (p = 0.02), vessels (p = 0.005) and stroma (p<0.001) were disclosed. No significant changes in MMP-2 expression were detected.

CONCLUSIONS

PDT induced an early, temporary decrease in MMP-9 and endostatin expression. At longer intervals, MMP-9 increase is possibly associated with the angiogenic process responsible for recurrence after PDT. MMP-9, however, acts as a double-edged sword by concomitant induction of endostatin, an endogenous inhibitor of angiogenesis.

Expression of matrix metalloproteinases in the subretinal fluid correlates with the extent of rhegmatogenous retinal detachment

BACKGROUND

We investigated the activity of matrix metalloproteinase (MMP)-2 and -9 and the protein levels of MMP-1, -3, -8 and the tissue inhibitor of MMPs (TIMP)-1 in the subretinal fluid (SRF) of patients with rhegmatogenous retinal detachment (RRD) and establishment of potential correlations with clinical parameters.

METHODS

Thirty-seven SRF from RRD patients and nine vitreous samples from the human eye of organ donors (controls) were collected and assayed for MMP-1,-3,-8 and TIMP-1 levels using ELISA and for MMP-2 and -9 activity employing gelatin zymography.

RESULTS

MMP-1, MMP-3, MMP-8, proMMP-2, proMMP-9, MMP-9 and TIMP-1 levels were higher in SRF compared with vitreous fluid. Overall, MMPs and TIMPs were differentially expressed in SRF with respect to duration and extent of RRD, as well as to stage of proliferative vitreoretinopathy. Regression analysis for all data indicated that a model consisting of MMP-3, MMP-8 and proMMP-9 could estimate the extent of RRD.

CONCLUSIONS

MMPs and TIMP-1 levels are elevated in SRF during RRD. A regression model consisting of MMP-3, MMP-8 and proMMP-9 may be proved to be of potential use in providing information for evaluation of the extent of RRD.

Toxicity of subretinal ribozyme to the proliferating cell nuclear antigen and 5-fluorouracil in rat eyes

PURPOSE

To investigate the subretinal toxicity profile of the ribozyme to the proliferating cell nuclear antigen (PCNA-Rz) and 5-fluorouracil (5-FU), as well as the highest nontoxic subretinal dose of the mixture of the two agents in rat eyes.

METHODS

Brown-Norway rats received subretinal injections of 1 microg, 10 microg, and 100 microg/microl PCNA-Rz and 0.06 microg/microl, 0.3 microg/microl, and 1.5 microg/microl 5-FU in the right eyes, and the left eyes were injected with H-BSS as control. Each dose was tested on 5 eyes in a 5 microl volume. In a second study, a combination of 5-FU (1.5 microg/microL) with varying 10-30-50 microg/microl doses of PCNA-Rz was tested in a regimen of four sequential subretinal injections. Toxicity was monitored by biomicroscopy, indirect ophthalmoscopy, electroretinography (ERG), and histology.

RESULTS

The highest nontoxic dose for subretinal PCNA-Rz was 10 microg/microl, whereas 100 microg/microl showed disturbance of pigmentation with corresponding histological changes of retinal photoreceptor loss and retinal pigment epithelium proliferation or irregularities. Subretinal injection of all three doses of 5-FU did not show any toxicity. Serial injections of a mixture of 1.5 microg/microl 5-FU with 10 microg/microl of PCNA-Rz was found to be safe in rat eyes.

CONCLUSIONS

Subretinal injections of the combination of PCNA-Rz (10 microg/microl) and 5-FU (1.5 microg/microl) demonstrated to be safe in rat eyes during the course of this study, even with a multiple administration of four injections.

Suppression of Laser-Induced Choroidal Neovascularization by Subconjunctival Injection of 9.ALPHA.-Fluoromedroxyprogesterone Acetate (FMPA), an Anti-angiogenic Agent, in Rats

9alpha-Fluoromedroxyprogesterone acetate (FMPA) is a synthetic analog of medroxyprogesterone acetate (MPA). FMPA exhibited more potent anti-tumor and anti-angiogenic activities in some assay systems than the parent agent, MPA. Exudative age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). Anecortave acetate, an angiostatic steroid, is clinically efficacious in patients with exudative AMD. Betamethasone is an anti-angiogenic steroid. Therefore, we examined the effects of FMPA, anecortave acetate and betamethasone on laser-induced CNV in rats. Anecortave acetate and betamethasone were included as positive controls. Crypton laser was applied to the fundus in Brown Norway rats. Laser photocoagulations were performed in each eye between the major retinal vessels of the superior retina. Subconjunctival injection of FMPA, anecortave acetate or betamethasone was performed once just after the photocoagulation (on day 0). The incidence of CNV formation was evaluated by fluorescein angiography (FAG) on day 14. On the next day, examination of the retinal function was performed by electro retinogram (ERG). Subconjunctival injection of FMPA at doses of 300, 1000 and 3000 microg/eye dose-dependently inhibited the incidence of CNV formation. Significant differences were observed at doses of 1000 and 3000 microg/eye of FMPA as compared with the control group. Anecortave acetate and betamethasone significantly inhibited the incidence of CNV formation. FMPA at the doses used in this study did not affect the retinal function in rats, as determined by ERG. FMPA appeared to be effective in a rat model of CNV, so it was demonstrated that FMPA might be useful in the treatment of AMD.

EFFICIENT GENE TRANSFER TO RETINAL PIGMENT EPITHELIUM CELLS WITH LONG-TERM EXPRESSION

PURPOSE

To evaluate the safety and efficiency of feline immunodeficiency virus (FIV) vectors for gene delivery into the mammalian retina.

METHODS

A first-generation FIV vector was constructed and administered into rabbit eyes at two different concentrations by intravitreal or subretinal routes. A second-generation FIV vector was also constructed and administered subretinally into both rabbit and rat eyes at the same concentration. After vector administration, eyes were monitored using slit-lamp biomicroscopy, indirect ophthalmoscopy, fundus photography, and electroretinogram. After the rabbits were killed, eye tissues were processed for light microscopy and immunohistochemical analysis.

RESULTS

Administration of both first- and second-generation FIV vectors produced transient vitritis and/or papillitis in rabbits, without other pathologic abnormalities. Retinal pigment epithelium (RPE) cells were the predominant cell type transduced in rabbit eyes, but ganglion cells and Muller cells were also transduced. Transduction was confined to the retinal bleb area. The second-generation FIV vector transduced RPE cells much more efficiently than the first-generation vector (95% vs. 4.5%, respectively; P = 0.0015) in rabbit eyes. In contrast, no toxicity was evident over a 24- to 25-month follow-up period after injection of the second-generation FIV vector into rat eyes. Tropism in the rat eye was similar, including RPE and ganglion cells, and the RPE transduction rate was also high (50%). Transgene expression was persistent in both species over the duration of the experiment.

CONCLUSION

Second-generation FIV vectors can efficiently transfer genes into RPE cells with resulting long-term expression, properties potentially valuable to gene therapy approaches to some retinal diseases.