Deeba Husain

Verteporfin Photodynamic Therapy Retreatment of Normal Retina and Choroid in the Cynomolgus Monkey

OBJECTIVE This study evaluated the effect of repeated photodynamic therapy (PDT) applications on normal primate retina and choroid using an intravenous infusion of liposomal benzoporphyrin derivative (verteporfin). DESIGN This was an experimental study in a primate model. ANIMALS/CONTROLS: Six cynomolgus monkeys were used as experimental subjects and one monkey was used as a control subject. INTERVENTION Three consecutive PDT treatments at 2-week intervals were applied over the center of the fovea or the optic nerve of each eye. Verteporfin was delivered by intravenous infusion at a dose of 6 mg/m2, 12 mg/m2, or 18 mg/m2. Laser irradiation was then applied using a diode laser (689 nm) with light doses and spot sizes kept constant. MAIN OUTCOME MEASURES Findings were documented by fundus photography, fluorescein angiography, and light and electron microscopy. RESULTS A cumulative dose response was seen angiographically and histologically with more severe damage to the retina and choroid noted at higher dye doses. Photodynamic therapy applied to the macula using the 6-mg/m2 verteporfin dose showed recovery of choriocapillaris, with mild retinal pigment epithelium and outer photoreceptor damage at 6 weeks. At this dose, the optic nerve showed few focal sites of axon atrophy and capillary loss. Treatments over the macula using the 12-mg/m2 and 18-mg/m2 doses led to chronic absence of choriocapillaris and photoreceptors at 6 weeks. One of two optic nerves became atrophic after PDT applications using dye doses of 12 mg/m2, and both optic nerves became atrophic in the 18-mg/m2 dye dose group. CONCLUSION Limited damage to the retina, choroid, and optic nerve was present in primates treated with multiple PDT sessions using 6 mg/m2 verteporfin with light doses and the timing of irradiation kept constant. However, PDT using higher dye doses of 12 mg/m2 and 18 mg/m2 led to significant chronic damage to the normal retina, choroid, and optic nerve.

Mechanism of age related macular degeneration

AMD is a poorly understood disease at this time. Since it is the leading cause of blindness in the elderly in the developed world, there is a pressing need for better treatment. Therefore, there is extensive ongoing research in both pathogenesis and therapy of AMD. Epidemiological studies have shown significant risk associated with increasing age and cigarette smoking, future studies may identify environmental risk factors though at present studies have been inconclusive. Genetic studies may identify subgroups of disease and thus help provide a selective approach to treatment. The vascular model of AMD may provide better understanding of the blood flow and post capillary resistance and help in early and newer intervention in the disease. Vascular endothelial growth factor has been extensively studied in choroidal neovascularization. It has been demonstrated in human and animal models of CNV and VEGF antagonists are currently in clinical trial. Extensive work is ongoing to prevent and treat CNV with antiangiogenic agents.

Photodynamic Therapy and Digital Angiography of Experimental Iris Neovascularization Using Liposomal Benzoporphyrin Derivative

PURPOSE To study the efficacy of liposomal benzoporphyrin derivative (BPD) (Verteportin) for the angiographic visualization and photodynamic therapy (PDT) of experimental iris neovascularization. METHODS Experimental iris neovascularization was induced in eight cynomolgus monkey eyes by occluding all the branch retinal veins with a dye-yellow (577-nm) laser. Iris angiography was done with sodium fluorescein, indocyanine green (ICG), and liposomal BPD to compare the visualization of normal and neovascular vessels by these three dyes. PDT was performed using an intravenous infusion of liposomal BPD (0.375-0.75 mg/kg), followed by irradiation with 689-nm light from a diode laser/slit-lamp delivery system using 600 mW/cm2 irradiance and 150 J/cm2 fluence. The effect of treatment was followed by iris photography and angiography, and the findings were confirmed by histopathology using light and electron microscopy. RESULTS Iris fluorescein angiography (FA) showed superficial tortuous and leaky new vessels. Liposomal BPD and ICG angiography of the same eye demonstrated deeper dilated and tortuous iris vessels, with minimal dye leakage. PDT of the iris with irradiation, performed within 20 minutes of the start of dye infusion (0.75 mg/kg), resulted in angiographic and histologic occlusion of iris vessels examined at 24 hours. Three to nine days after PDT, histopathologic examination showed regression of the iris neovascular membrane, with some open vessels. CONCLUSIONS Liposomal BPD and ICG provided angiographic visualization of deeper normal and neovascular iris vessels. PDT using liposomal BPD leads to effective early closure to experimental iris neovascularization.

c-Cbl inhibits angiogenesis and tumor growth by suppressing activation of PLCγ1

Angiogenesis is regulated by highly coordinated function of various proteins with pro- and anti-angiogenic functions. Among the many cytoplasmic signaling proteins that are activated by VEGFR-2, activation of PLCγ1 is considered to have a pivotal role in angiogenic signaling. In previous study we have identified c-Cbl as a negative regulator of PLCγ1 in endothelial cells, the biochemical and biological significance of c-Cbl, however, in angiogenesis in vivo and molecular mechanisms involved were remained elusive. In this study, we report that genetic inactivation of c-Cbl in mice results in enhanced tumor angiogenesis and retinal neovascularization. Endothelial cells derived from c-Cbl null mice displayed elevated cell proliferation and tube formation in response to VEGF stimulation. Loss of c-Cbl also resulted in robust activation of PLCγ1 and increased intracellular calcium release. c-Cbl-dependent ubiquitination selectively inhibited tyrosine phosphorylation of PLCγ1 and mostly refrained from ubiquitin-mediated degradation. Hence, we propose c-Cbl as an angiogenic suppressor protein where upon activation it uniquely modulates PLCγ1 activation by ubiquitination and subsequently inhibits VEGF-driven angiogenesis.

Photodynamic Therapy of Exudative Age-Related Macular Degeneration

Photodynamic therapy (PDT) is a potentially selective treatment modality, which involves systemic administration of a photosensitizer dye. Dye accumulates in proliferating tissues such as tumors and neovascularization, followed by exposure of the photosensitized tissue to light at a wavelength at the absorption maximum of the dye. Excitation of the dye leads to photochemical damage of the targeted tissue. Various photosensitizers have been used in experimental choroidal neovascularization to investigate PDT. We have used benzoporphyrin derivative monoacid (BPD) and shown that it occludes experimental choroidal neovascularization (CNV) with no significant damage to the overlying neurosensory retina or underlying choroid. Clinical trials of PDT using BPD for exudative age-related macular degeneration (AMD) have started. Preliminary results suggest that CNV can be occluded in the early posttreatment phase, with some nonselective effects at high light doses. Further studies are underway to investigate whether...

Inhibition of the alternative complement pathway preserves photoreceptors after retinal injury

The alternative complement pathway is activated in response to retinal injury, and inhibiting this pathway prevents complement-mediated photoreceptor cell death. Preventing photoreceptor death after retinal injury Retinal detachment and subsequent degeneration of the retina can lead to progressive visual decline due to death of photoreceptor cells, the major light-sensing cells within the eye. Early inflammatory mediators are up-regulated in the eye of patients with retinal detachment including components of the alternative complement pathway. Using a mouse model of retinal detachment, Sweigard et al. found that by blocking the alternative complement pathway through both genetic and pharmacological means, photoreceptors were protected from cell death. Degeneration of photoreceptors is a primary cause of vision loss worldwide, making the underlying mechanisms surrounding photoreceptor cell death critical to developing new treatment strategies. Retinal detachment, characterized by the separation of photoreceptors from the underlying retinal pigment epithelium, is a sight-threatening event that can happen in a number of retinal diseases. The detached photoreceptors undergo apoptosis and programmed necrosis. Given that photoreceptors are nondividing cells, their loss leads to irreversible visual impairment even after successful retinal reattachment surgery. To better understand the underlying disease mechanisms, we analyzed innate immune system regulators in the vitreous of human patients with retinal detachment and correlated the results with findings in a mouse model of retinal detachment. We identified the alternative complement pathway as promoting early photoreceptor cell death during retinal detachment. Photoreceptors down-regulate membrane-bound inhibitors of complement, allowing for selective targeting by the alternative complement pathway. When photoreceptors in the detached retina were removed from the primary source of oxygen and nutrients (choroidal vascular bed), the retina became hypoxic, leading to an up-regulation of complement factor B, a key mediator of the alternative pathway. Inhibition of the alternative complement pathway in knockout mice or through pharmacological means ameliorated photoreceptor cell death during retinal detachment. Our current study begins to outline the mechanism by which the alternative complement pathway facilitates photoreceptor cell death in the damaged retina.

Vitreous evaluation: a diagnostic challenge.

PURPOSE To categorize vitrectomy cytologic diagnoses and ancillary tests to address appropriate processing of low-volume vitreous samples. DESIGN Retrospective case series. PARTICIPANTS Five thousand seven hundred thirty-six vitreous samples. METHODS Cytologic diagnoses of therapeutic and diagnostic vitrectomy samples and their processing protocols from 3 teaching institutions were reviewed. MAIN OUTCOME MEASURES Diagnostic results were categorized as negative for malignancy, suspicious for malignancy, and positive for malignancy. All ancillary studies performed were documented, including special stains, immunohistochemistry analysis, cytokine levels, and polymerase chain reaction (PCR) analysis. RESULTS Of the 5736 vitreous samples analyzed, 4683 (81.64%) were from Tufts Medical Center (TMC), 955 (16.65%) were from Boston Medical Center (BMC), and 98 (1.70%) were from Massachusetts Eye Research and Surgery Institution (MERSI). Cases from TMC and BMC were therapeutic and diagnostic vitrectomies, and MERSI cases were diagnostic vitrectomies. Most vitrectomies showed negative results for malignancy: 99.47% of TMC cases, 99.89% of BMC cases, and 79.6% of MERSI cases. These included vitreous hemorrhage and inflammatory or infectious findings. Ancillary studies performed in this category included Periodic Acid-Schiff staining for fungi, PCR analysis for toxoplasmosis, cytomegalovirus, Epstein-Barr virus (EBV), herpes simplex virus I and II, and vitreous cultures for infections (coagulase-negative Staphylococcus, Candida, Fusarium, and Propionibacterium species). Interleukin (IL) 10-to-IL-6 ratios were performed on 38.7% of cases from MERSI. Fourteen cases from TMC were suspicious for malignancy based on cytologic evaluation. Eleven cases from TMC, 1 case from BMC, and 20 cases from MERSI showed positive results for malignancy and included B-cell lymphoma, retinoblastoma, melanoma, and metastatic adenocarcinoma. The ancillary testing included PCR for heavy chain immunoglobulin gene rearrangements, immunohistochemistry for EBV, in situ hybridization for κ and λ light chains, and cytogenetics. CONCLUSIONS This is the largest data pool of reported cytologic diagnoses of diagnostic and therapeutic vitrectomy samples. Cytologic evaluation of therapeutic vitrectomy samples provides a valuable baseline of nonpathologic findings that assist in differentiation between malignancy, infections, and inflammatory conditions. Allocation of small-volume vitreous samples to select ancillary testing from the plethora of available diagnostic tests requires preoperative communication between surgeons and pathologists to ensure appropriate and timely treatment methods.

Role of c-Cbl–Dependent Regulation of Phospholipase Cγ1 Activation in Experimental Choroidal Neovascularization

PURPOSE Activation of phospholipase Cγ1 (PLCγ1) by vascular endothelial growth factor receptor (VEGFR)-2 is necessary for proliferation and tube formation of endothelial cells in vitro. Previous work has demonstrated that Casitas B-lineage lymphoma (c-Cbl) promotes ubiquitination of PLCγ1 and suppression of its tyrosine phosphorylation. This study was designed to evaluate the importance of PLCγ1 and c-Cbl in experimental choroidal neovascularization (CNV). METHODS The role of PLCγ1 was studied in three models of angiogenesis: the endothelial cell culture system, the chorioallantoic membrane (CAM) assay, and the laser-induced CNV model. Endothelial cells were analyzed for the role of PLCγ1 in promoting tube formation. CAMs were incubated with pharmacologic agents that either inhibit or stimulate PLCγ1. CNV was induced in wild-type and c-Cbl-knockout mice, and the progression of CNV was evaluated by fluorescein angiography. RESULTS Activation of PLCγ1 was necessary for tube formation of endothelial cells. PLCγ1 stimulation increased the growth of blood vessels and conversely, PLCγ1 inhibition decreased the growth of blood vessels in the CAM model. CNV lesions in the c-Cbl-knockout mice were significantly greater in number, more confluent, and increased in size with time, compared with those in the control wild-type mice. CONCLUSIONS The data show that PLCγ1 plays an important role in angiogenesis. Loss of c-Cbl results in enhanced CNV in the eye. The study also shows that c-Cbl plays an important role in ocular angiogenesis, suggesting that modulation of c-Cbl activity or inhibition of PLCγ1 would be a compelling target for antiangiogenesis therapy.

Ocriplasmin for Treatment of Stage 2 Macular Holes: Early Clinical Results

BACKGROUND AND OBJECTIVE To review clinical and structural outcomes of ocriplasmin for treatment of stage 2 macular holes. PATIENTS AND METHODS A retrospective review of the first patients with stage 2 macular holes to be treated with ocriplasmin at Massachusetts Eye and Ear Infirmary. All patients were imaged with spectral-domain optical coherence tomography (SD-OCT). RESULTS Eight patients with stage 2 macular holes received a single injection of 125 μg of ocriplasmin. One patient (12.5%) demonstrated macular hole closure. The posterior hyaloid separated from the macula in six eyes (75%). All seven holes that remained open showed enlargement in hole diameters (narrowest, apical, and basal) at 1 week and 1 month. All seven were successfully closed with surgery. Ellipsoid zone disruptions were observed by OCT in four eyes (50%) and persisted throughout follow-up (more than 6 months on average). CONCLUSION In early clinical results, the authors found a lower macular hole closure rate with ocriplasmin than previously reported. Enlargement was observed in all holes that failed to close with ocriplasmin. The authors found ellipsoid zone disruptions that persisted through 6 months of follow-up after ocriplasmin injection. Further work is needed to investigate the cause for these ellipsoid zone changes.

Endogenous Endophthalmitis in the American and Korean Population: An 8-year Retrospective Study

ABSTRACT Purpose: To study the clinical features of endogenous endophthalmitis (EE) in sample patient populations from the USA and South Korea over an 8-year period. Methods: We reviewed data from 128 eyes of 60 American and 48 Korean patients diagnosed with EE and compared their clinical characteristics. Results: Fungemia and liver abscess were the most common extraocular infection sources among American (26.7%) and Korean patients (33.3%), respectively. Klebsiella pneumoniae and Candida species were the most common pathogens of EE in the Korean and the American patients, respectively. Endophthalmitis caused by fungi had a better visual prognosis than that caused by bacteria (p = 0.001). Vitrectomy was beneficial for eyes with EE due to virulent bacteria presenting with worse than counting finger vision. Conclusions: The predisposing conditions and responsible organisms for EE vary in different regions of the world. The visual prognosis was strongly influenced by the underlying pathogen.