Blood-retinal barrier as a converging pivot in understanding the initiation and development of retinal diseases / 中华医学杂志(英文版)

Clinical ophthalmologists consider each retinal disease as a completely unique entity. However, various retinal diseases, such as uveitis, age-related macular degeneration, diabetic retinopathy, and primary open-angle glaucoma, share a number of common pathogenetic pathways. Whether a retinal disease initiates from direct injury to the blood-retinal barrier (BRB) or a defect/injury to retinal neurons or glia that impairs the BRB secondarily, the BRB is a pivotal point in determining the prognosis as self-limiting and recovering, or developing and progressing to a clinical phenotype. The present review summarizes our current knowledge on the physiology and cellular and molecular pathology of the BRB, which underlies its pivotal role in the initiation and development of common retinal diseases.

Prostaglandin antagonist relieves blood-retinal barrier breakdown induced by anterior segment intraocular surgery in a rat model / O antagonista das prostaglandinas alivia a ruptura da barreira sanguínea retiniana induzida pela cirurgia intraocular do segmento anterior em um modelo em ratos

ABSTRACT Purpose: To evaluate the efficacy of prostaglandin antagonists on blood-retinal barrier breakdown induced by anterior segment intraocular simulated surgery. Methods: Rats were randomly assigned to a negative control group, model group, nonsteroidal anti-inflammatory drugs prophylactic treatment group, nonsteroidal anti-inflammatory drugs treatment group, corticosteroid prophylactic treatment group, and corticosteroid treatment group. Four hours and 48h after modeling, the concentrations of PGE1, PGE2, and PGF2 α in the aqueous humor and vitreous body of the rat model were visualized using ELISA. The integrity of the blood-retinal barrier was quantitatively measured using Evan's blue as a tracer. Results: Four hours after modeling, the concentrations of PGE1, PGE2, and PGF2α in the aqueous humor and vitreous body in the negative control group and the nonsteroidal anti-inflammatory drugs prophylactic treatment group were significantly lower than those in the model group. The concentrations of PGE1, PGE2, and PGF2α in the aqueous humor and vitreous body in the corticosteroid prophylactic treatment group were higher than those in the negative control group and the nonsteroidal anti-inflammatory drugs prophylactic treatment group. Forty-eight hours after modeling, the concentrations of PGE1, PGE2, and PGF2α in the aqueous humor and vitreous body in the nonsteroidal anti-inflammatory drugs prophylactic treatment group, nonsteroidal anti-inflammatory drugs treatment group, corticosteroid prophylactic treatment group, and corticosteroid treatment group were lower than those in the model group, but higher than those in the negative group. Retinal Evan's blue leakage in the nonsteroidal anti-inflammatory drugs prophylactic treatment group was higher than that in the negative control group, and lower than those in the nonsteroidal anti-inflammatory drugs treatment group, corticosteroid prophylactic treatment group, corticosteroid treatment group, and model group. Retinal Evan's blue leakage in the nonsteroidal anti-inflammatory drugs treatment group, corticosteroid prophylactic treatment group, and corticosteroid treatment group were lower than those in the model group. Conclusions: This study confirms that prostaglandin antagonists can relieve blood-retinal barrier breakdown in a rat model and that nonsteroidal anti-inflammatory drugs prophylactic treatment can achieve better efficacy.

RESUMO Objetivos: Avaliar a eficácia do antagonista de prostaglandinas no rompimento da barreira hemato-retiniana induzida por cirurgia simulada intraocular do segmento anterior. Métodos: Os ratos foram divididos aleatoriamente em grupo controle negativo, grupo modelo, grupo de tratamento profilático com drogas anti-inflamatórias não esteroides, grupo de tratamento com anti-inflamatórias não esteroides, grupo de tratamento profilático com corticosteroides e grupo de tratamento com corticosteroides. Quatro e 48h após a modelagem, as concentrações de PGE1, PGE2 e PGF2 α no humor aquoso e no corpo vítreo em modelo em ratos foram detectadas através de Elisa. A integridade da barreira hemato-retiniana foi quantitativamente mensurada utilizando o azul de Evans como marcador. Resultados: Quatro horas após a modelagem, as concentrações de PGE1, PGE2 e PGF2α no humor aquoso e no corpo vítreo no grupo controle negativo e no grupo de tratamento profilático com anti-inflamatórias não esteroides foram significativamente menores do que as do grupo modelo. As concentrações de PGE1, PGE2 e PGF2α no humor aquoso e no corpo vítreo no grupo de tratamento profilático com corticosteroides foram maiores do que as observadas no grupo controle negativo e no grupo de tratamento profilático com anti-inflamatórias não esteroides. 48h após a modelagem, as concentrações de PGE1, PGE2 e PGF2α no humor aquoso e no corpo vítreo no grupo de tratamento profilático com anti-inflamatórias não esteroides, no grupo de tratamento com anti-inflamatórias não esteroides, no grupo de tratamento profilático com corticosteroides e no grupo de tratamento com corticosteroides foram menores do que as observadas no grupo modelo e maiores que as observadas no grupo negativo. O extravasamento retinal de azul de Evans no grupo de tratamento profilático com anti-inflamatórias não esteroides foi maior que no grupo controle negativo e menor que nos grupos de tratamento com anti-inflamatórias não esteroides, de tratamento profilático com corticosteroides, de tratamento com corticosteroides e no grupo modelo. O extravasamento retinal de azul de Evans observado nos grupos de tratamento com anti-inflamatórias não esteroides, de tratamento profilático com corticosteroides e de tratamento com corticosteroides foi inferior ao observado no grupo modelo. Conclusões: Este estudo valida que o antagonista das prostaglandinas pode aliviar a ruptura da barreira hemato-retiniana em um modelo em ratos e que o tratamento profilático com anti-inflamatórias não esteroides pode alcançar melhor eficácia.

Effects of Bisphosphonates on Glucose Transport in a Conditionally Immortalized Rat Retinal Capillary Endothelial Cell Line (TR-iBRB Cells)

The objective of the present study was to elucidate the effect of bisphosphonates, anti-osteoporosis agents, on glucose uptake in retinal capillary endothelial cells under normal and high glucose conditions. The change of glucose uptake by pre-treatment of bisphosphonates at the inner blood-retinal barrier (iBRB) was determined by measuring cellular uptake of [3H]3-O-methyl glucose (3-OMG) using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB cells) under normal and high glucose conditions. [3H]3-OMG uptake was inhibited by simultaneous treatment of unlabeled D-glucose and 3-OMG as well as glucose transport inhibitor, cytochalasin B. On the other hand, simultaneous treatment of alendronate or pamidronate had no significant inhibitory effect on [3H]3-OMG uptake by TR-iBRB cells. Under high glucose condition of TR-iBRB cells, [3H]3-OMG uptake was increased at 48 h. However, [3H]3-OMG uptake was decreased significantly by pre-treatment of alendronate or pamidronate compared with the values for normal and high glucose conditions. Moreover, geranylgeraniol (GGOH), a mevalonate pathway intermediate, increased the uptake of [3H]3-OMG reduced by bisphosphonates pre-treatment. But, pre-treatment of histamine did not show significant inhibition of [3H]3-OMG uptake. The glucose uptake may be down regulated by inhibiting the mevalonate pathway with pre-treatment of bisphosphonates in TR-iBRB cells at high glucose condition.

SIRT1 negatively regulates amyloid-beta-induced inflammation via the NF-B pathway

Chronic inflammation induced by amyloid-beta (Aβ) plays a key role in the development of age-related macular degeneration (AMD), and matrix metalloproteinase-9 (MMP-9), interleukin (IL)-6, and IL-8 may be associated with chronic inflammation in AMD. Sirtuin 1 (SIRT1) regulates inflammation via inhibition of nuclear factor-kappa B (NF-κB) signaling, and resveratrol has been reported to prevent Aβ-induced retinal degeneration; therefore, we investigated whether this action was mediated via activation of SIRT1 signaling. Human adult retinal pigment epithelial (RPE) cells were exposed to Aβ, and overactivation and knockdown of SIRT1 were performed to investigate whether SIRT1 is required for abrogating Aβ-induced inflammation. We found that Aβ-induced RPE barrier disruption and expression of IL-6, IL-8, and MMP-9 were abrogated by the SIRT1 activator SRT1720, whereas alterations induced by Aβ in SIRT1-silenced RPE cells were not attenuated by SRT1720. In addition, SRT1720 inhibited Aβ-mediated NF-κB activation and decrease of the NF-κB inhibitor, IκBα. Our findings suggest a protective role for SIRT1 signaling in Aβ-dependent retinal degeneration and inflammation in AMD.

Spontaneously resolving macular cyst in an infant

The purpose of this study is to describe transient macular cysts in an infant and correlate their occurrence with normal development events. A newborn Caucasian girl presented with a protruding corneal mass in her left eye at birth. She underwent a complete ophthalmic examination. A keratinized staphylomatous malformation involving the entire cornea and precluding further visualization of the anterior and posterior segment was observed in the left eye. Spectral domain optical coherence tomography [SD-OCT] of the right eye performed when the child was approximately 6-week-old had revealed an unexpected finding of macular cysts involving the inner nuclear and outer retinal layers. Corneal transplant in the left eye was performed a month later. Ocular examination under anesthesia just prior to surgery revealed normal intraocular pressure, anterior segment and retina in the right eye. SD-OCT was normal in both eyes and showed complete resolution of the cysts in the right eye. The patient had not been on any medications at that time. Although clinical retinal examination might be unremarkable, SD-OCT may reveal cystic spaces in the macula. In the absence of conditions known to be associated with macular edema, transient macular cysts may arise due to a developmental incompetence of the blood-retinal barrier or may represent transient spaces created during normal migration of retinal cells. Further study is warranted to delineate the entity of transient macular cysts in infancy

Chlorogenic Acid Decreases Retinal Vascular Hyperpermeability in Diabetic Rat Model

To evaluate the effect of chlorogenic acid (CGA), a polyphenol abundant in coffee, on retinal vascular leakage in the rat model of diabetic retinopathy, Sprague-Dawley rats were divided into four groups: controls, streptozotocin-induced diabetic rats, and diabetic rats treated with 10 and 20 mg/kg chlorogenic acid intraperitoneally daily for 14 days, respectively. Blood-retinal barrier (BRB) breakdown was evaluated using FITC-dextran. Vascular endothelial growth factor (VEGF) distribution and expression level was evaluated with immunohistochemistry and Western blot analysis. Expression of tight junction proteins, occludin and claudin-5, and zonula occludens protein, ZO-1 was also evaluated with immunohistochemistry and Western blot analysis. BRB breakdown and increased vascular leakage was found in diabetic rats, with increased VEGF expression and down-regulation of occludin, claudin-5, and ZO-1. CGA treatment effectively preserved the expression of occludin, and decreased VEGF levels, leading to less BRB breakdown and less vascular leakage. CGA may have a preventive role in BRB breakdown in diabetic retinopathy by preserving tight junction protein levels and low VEGF levels.

Effects of electromagnetic pulse exposure on the permeability of inner blood-retinal barrier model in vitro / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To establish the inner blood-retinal barrier (BRB) model in vitro by co-culturing RF/6A cells and C6 cells and to investigate the effects of EMP (200 kV/m, 200 pulses) exposure on the permeability of the inner BRB model in vitro.</p><p><b>METHODS</b>RF/6A cells and C6 cells were co-cultured on transwell, and the characteristic of the inner BRB model was assessed by detecting transendothelial electrical resistance (TEER) and the permeability of horseradish peroxidase (HRP). The co-cultured model was exposed or sham exposed to the EMP (200 kV/m 200 pulses) for 0.5, 3, 6, 12, 24 h in vitro, then TEER and the permeability of HRP were measured for studying the effects of EMP on the permeability of inner BRB model in vitro.</p><p><b>RESULTS</b>TEER value (145 Ωcm(2)) of the co-culturing inner BRB model significantly increased, as compared to that of RF/6A cells alone model (P < 0.05) on the 6th day after inoculation. There was significant difference of permeability of HRP between the co-culturing inner BRB model and RF/6A cells alone model (P < 0.05). The ability of inhibiting large molecular materials in the co-culturing inner BRB model enhanced. The TEER value decreased and the permeability of HRP increased as compared to the sham group at 0.5, 3, 6 h after the exposure.</p><p><b>CONCLUSION</b>The inner BRB model by co-culturing RF/6A cells and C6 cells in vitro is efficient and suitable to study the alterations of the restricted permeability function of the inner BRB. EMP (200 kV/m for 200 pulses) could induce the enhanced permeability of the inner BRB model in vitro.</p>

Intravenously Administered Anti-recoverin Antibody Alone Does Not Pass through the Blood-Retinal Barrier

PURPOSE: Cancer-associated retinopathy is a paraneoplastic retinal degeneration which may primarily result from auto-immune mediated apoptosis. It has been hypothesized that high titer of auto-antibodies are able to cross the blood-retinal barrier (BRB) and to enter retinal cells to activate apoptotic pathway which has been already well-established. However, it still remains to be elucidated whether auto-antibodies could cross BRB in the retina. Herein, we demonstrated that intravenously administrated anti-recoverin antibodies could not pass through BRB and not lead to retinal cell death. METHODS: Anti-recoverin antibody was intravenously injected to C57BL/6 mice, which were sacrificed 1 and 7 days to obtain eye. Vascular endothelial growth factor was intravitreally injected to induce BRB breakdown, which was confirmed by fluorescein angiography and western blotting for zonula occludens (ZO)-1, ZO-2 and occludin. To investigate the location of anti-recoverin antibody in the retina, immunofluorescein was performed. The retinal toxicity of intravenous anti-recoverin antibody was evaluated by histological examination and transferase-mediated dUTP nick-end labeling. Immunofluorescein staining for glial fibrillary acidic protein was done to address glial activation as well. RESULTS: Intravenously administrated anti-recoverin antibodies were exclusively distributed on retinal vessels which were co-localized with CD31, and led to neither increase of glial fibrillary acidic protein expression, as an indicator of retinal stress, nor apoptotic retinal cell death. Moreover, even in the condition of vascular endothelial growth factor-induced BRB breakdown, anti-recoverin antibodies could not migrate across BRB and still remained on retinal vessels without retinal cytotoxicity. CONCLUSIONS: Our results suggest that high titer of intravascular anti-recoverin antibodies could not penetrate into the retina by themselves, and BRB breakdown mediated by dysregulation of tight junction might not be sufficient to allow anti-recoverin antibodies to pass through BRB.

Ocular drug delivery; impact of invitro cell culture models

Normal vision depends on the optimal function of ocular barriers and intact membranes that selectively regulate the environment of ocular tissues. Novel pharmaco-therapeutic modalities have aimed to overcome such biological barriers which impede efficient ocular drug delivery. To determine the impact of ocular barriers on research related to ophthalmic drug delivery and targeting, herein we provide a review of the literature on isolated primary or immortalized cell culture models which can be used for evaluation of ocular barriers. In vitro cell cultures are valuable tools which serve investigations on ocular barriers such as corneal and conjunctival epithelium, retinal pigment epithelium and retinal capillary endothelium, and can provide platforms for further investigations. Ocular barrier-based cell culture systems can be simply set up and used for drug delivery and targeting purposes as well as for pathological and toxicological research

Efeitos da latanoprosta sobre a espessura foveal em olhos submetidos à cirurgia de catarata / Influence of topical latanoprost on foveal thickness in eyes that underwent uneventful cataract surgery

OBJETIVO: Avaliar prospectivamente com o uso da tomografia de coerência óptica se o uso tópico de latanoprosta induz alterações retinianas em pacientes submetidos à cirurgia de catarata. MÉTODOS: Estudo clínico randomizado, com observador mascarado e um mês de duração. Pacientes pseudofácicos foram tratados com latanoprosta (n=10) ou lubrificante ocular uma vez ao dia (grupo controle - placebo) (n=10). Metade dos pacientes de cada grupo possuía capsulotomia posterior (Nd:YAG laser). Avaliamos o status da barreira hemato-retiniana pela medida da espessura retiniana na fóvea com a tomografia de coerência óptica. Exames de tomografia de coerência óptica e medida da acuidade visual foram realizados antes do início do estudo e com 15 e 30 dias de tratamento. RESULTADOS: Não foi observada alteração significante na média da espessura foveal do grupo controle (p>0,0610). Houve aumento significante na média da espessura foveal nos pacientes tratados com latanoprosta (p<0,0004). Não foi observada alteração na acuidade visual em nenhum paciente. A média da espessura retiniana na fóvea foi significativamente maior no grupo da latanoprosta (p<0,0007). A espessura foveal nos olhos tratados com latanoprosta com cápsula posterior rota foi significativamente maior que a dos pacientes com cápsula íntegra (p<0,0461). Comparando apenas os pacientes com cápsula posterior íntegra, houve diferença significante da espessura foveal entre os pacientes tratados com latanoprosta (236,4 ± 29,4 mm) e placebo (197,8 ± 19,3 mm) apenas na avaliação realizada com 30 dias de tratamento. CONCLUSÕES: Latanoprosta pode levar à quebra da barreira hemato-retiniana em pacientes pseudofácicos. Isso é mais provável de ocorrer em pacientes com cápsula posterior rota.

PURPOSE: To study prospectively using optical coherence tomography whether topical latanoprost induces retinal disorders in patients that underwent cataract surgery. METHODS: Randomized, masked-observer, one-month clinical trial. Pseudophakic patients were treated with latanoprost (n=10) or lubricant drop q.d. (control group) (n=10). Half of the patients of each group presented ruptured posterior capsule (Nd:YAG laser). We evaluated the blood-retinal barrier status assessed by optical coherence tomography measurement of retinal thickness in the fovea. Before the beginning of the study and after 15 and 30 days of treatment, optical coherence tomography images were taken, and the visual acuity examination was performed. RESULTS: There was no statistically significant increase in mean foveal thickness when patients instilled placebo (P>0.0610). A statistically significant increase in retinal thickness in the fovea was observed when patients instilled latanoprost (P<0.0004). No changes were observed in visual acuity in both groups. Mean retinal thickness in the fovea was significantly higher in the latanoprost group (P<0.0007). The mean foveal thickness in latanoprost treated eyes with ruptured posterior capsule was statistically greater when compared with that of intact posterior capsule (P<0.0461). When comparing only the patients with that of intact posterior capsule, there was a statistically significant difference in foveal thickness between patients treated with latanoprost (236.4 ± 29.4 mm) and placebo (197.8 ± 19.3 mm) only at 30 days of treatment. CONCLUSIONS: Latanoprost may lead to disruption of the blood-retinal barrier in pseudophakic patients, and is more probable to occur in patients with ruptured posterior capsule.

The Steroid Effect on the Blood-Ocular Barrier Change Induced by Triolein Emulsion as seen on Contrast-Enhanced MR Images

OBJECTIVE: The purpose of this study is to evaluate the effect of dexamethasone on the damaged blood-ocular barrier caused by triolein emulsion, using contrast-enhanced MR imaging. MATERIALS AND METHODS: An emulsion of 0.1-mL triolein in 20 mL of saline was infused into the carotid arteries of 32 cats, 12 cats were placed in the treatment group and 18 cats were placed in the Control group. Thirty minutes after the infusion of triolein emulsion, a set of orbital pre- and post-contrast T1-weighted MR images (T1WIs) were obtained. Infusion of 10 mg/kg dexamethasone into the ipsilateral carotid artery of each of the cats in the treatment group cats and 20 mL saline in each of the cats in the control group was given. A second set of pre- and post-contrast orbital T1WIs were obtained three hours following triolein emulsion infusion. Qualitative analysis was performed for the the anterior chamber (AC), the posterior chamber (PC), and in the vitreous humor of the ipsilateral and contralateral eyes. The signal intensity ratios of the ipsilateral eye over the contralateral eye were quantitatively evaluated in the three ocular chambers on the first and second set of T1WIs, and were then statistically compared. RESULTS: Qualitatively, the AC, the PC or the vitreous did not show immediate contrast enhancement on the first and the second set of post-contrast T1WIs. However, the AC and the PC showed delayed contrast enhancement for both groups of cats on the second pre-contrast T1WIs. No enhancement or minimally delayed enhancement was seen for the vitreous humor. Quantitatively, the signal intensity ratios in the PC of the treatment group of cats were statistically lower than the ratios of the control group of cats for the second set of T1WIs (p = 0.037). The AC and vitreous showed no statistically significant difference between the feline treatment group and control group (p > 0.05). CONCLUSION: Contrast-enhanced MR images revealed increased vascular permeability in the PC of the eye after infusion of triolein emulsion. Dexamethasone seems to decrease the breakdown of the blood-aqueous barrier in the PC.

Involvement of VEGF in both Cell Apoptosis and Survival in the Retina of Type 2 Diabetic OLETF Rats / 대한해부학회지

Vascular endothelial growth factor (VEGF) is closely involved in early retinal pathology of diabetes, including blood-retinal barrier breakdown, pericyte loss, neuro-retinal apoptosis, and cell proliferation. This study examines the involvement of VEGF in cell apoptosis and survival in the retina of animals with type 2 diabetes. We used retinas from 28-week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of spontaneous type 2 diabetes, and Long-Evans Tokushima Otsuka (LETO) rats as controls. In parallel with evidence for pericyte loss, we found cell proliferation, apoptosis, and endothelial nitric oxide synthase (eNOS) (an indicator of endothelial cell proliferation/survival) and VEGF overexpression in the OLETF-retina, compared to control LETO. Furthermore, apoptotic signals were partly co-localized to only VEGF-positive cells in the OLETF-retina, but no apoptotic signals were found in VEGF- and eNOS-double-positive cells. These results suggest that upregulated VEGF is involved in apoptosis and eNOS-dependent cell survival in the retinas of type 2 diabetic rats.

MRI evidence of exogenous vascular endothelial growth factor-enhanced transport across inner ear barriers in guinea pigs / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>Increased vascular endothelial growth factor (VEGF) and VEGF receptor expression is the important biological response under shear stress, ischemia and hypoxia conditions. Mechanical vibration induced cochlea shear stress and trauma obviously upregulate VEGF and VEGF receptor 2 (VEGFR2) expression in the cochlea. To evaluate the possibility of VEGF varying the transport in blood-labyrinth barrier and blood-perilymphatic barrier.</p><p><b>METHODS</b>Eleven guinea pigs, male and female, weighing from 300 g to 900 g were kept under general anaesthesia with xylazine (16 mg/kg) and ketamine (60 mg/kg) for both drug delivery and MRI measurement. VEGF (6 ears) and phosphate-buffered saline (PBS, 5 ears) were delivered to the inner ear via the round window membrane (soaked in gelfoam). The T1 contrast agent gadodiamide (Gd-DTPA-BMA) chelated bound paramagnetic gadolinium was used as the inner ear barrier transportation tracer. A Bruker Biospec Avance 47/40 experimental MRI system with a magnetic field strength of 4. 7 Tesla and a 40 cm bore was used for the 2-dimensional cochlea MRI evaluation. The Paravision software was used for image intensity measurement and the Adobe Photoshop 6.0 software was used for image presentation.</p><p><b>RESULTS</b>VEGF induced significant Gd uptake in the scala tympani and scala vestibuli, but had little effect on the uptake of Gd in the scala media.</p><p><b>CONCLUSIONS</b>VEGF significantly increased the transportation of blood-perilymphatic barrier and adapted the inner ear for compensation and repair.</p>

Outer Blood-retinal Barrier Alteration Induced by Intraocular Ad vanced Glycation Endproduct

Advanced glycation end-product(AGE)is known as a factor causing diabetic retinopathy, but little is known about its effect on the function of outer blood-retinal barrier. To test whether AGE can increase the permeability of outer blood-retinal barrier, we injected glycated albumin into white rabbit eyes and observed the change of the fundus and of the outer blood-retinal barrier permeability. The rabbit retina in medullary ray was thickened in AGE-injected eyes. Intravenously injected microperoxidase, tracer molecule, was found in outer sensory retinal layer and outside of the retinal pigment epithelium in AGE-injected eyes. These results suggest that intraocularly injected AGE can increase the outer blood-retinal barrier permeability.

Measurement of Blood Retina Barrier in Branch Retinal Vein Occlusion (BRVO)

Vitreous fluorophotometry was used to measure blood retinal barrier permeability to fluorescein in 15 patients with branch retinal vein occlusion(BRVO). Mean posterior vitreous fluorescein concentration(3mm) was 20.0 +/- 11.3(ng/ml) in affected eyes, and 2.99 +/- 1.22(ng/ml) in unaffected eyes. There was a statistically significant difference between the affected eye and unaffected eye(p<0.05). Also there was a correlation between the hemorrhage area and the posterior vitreous fluorescein concentration(r2=0.819). This study revealed that the permeability of blood retinal barrier was increased in BRVO as compared to the contralateral eye, and the higher permeability values were associated with the extent of area involved.

The effect of subtenon injection of methylprednisolone acetate on the breakdown of blood retinal barrier after cryotherapy

Using computerized vitreous fluorophotometry (VFP, Fluorotron(TM)), we examined the effect of cryotherapy on the blood retinal barrier (BRB) and the effect of subtenon injection of methylprednisolone acetate (Depomedrol(R)). In experiment 1, the right eyes of the 13 pigmented rabbits were treated with heavy cryotherapy after baseline VFP readings. The freezes were applied at 6 places in each quadrant around the equator are in two rows, a total of 24 places circumferentially. The left eyes were reserved as controls. In 6 rabbits (cryo with steroid group), Depomedrol(R) 10 mg of Depomedrol was injected into subtenon space after cryotherapy. The other 7 rabbits were treated with cryotherapy only (cryo only group). The VFP readings were taken 1, 3, 5, and 7 days, 2, 3, 5, and 7 weeks after cryotherapy. Cryotherapy increased the breakdown of BRB significantly. The peak VFP readings were obtained 5 days after cryotherapy in the cryo only group and 7 days after cryotherapy in the cryo with steroid group. In the cryo only group, the severity of the breakdown of BRB was higher than in the cryo with steroid group, and the increased VFP readings could not be normalized until 7 weeks after cryotherapy. In experiment 2, both eyes of the 8 pigmented rabbits were treated with medium cryotherapy after baseline VFP readings. The freezes were applied at 3 places in the superior temporal quadrant and at 3 places in the superior nasal quadrant, a total of 6 places. Depomedrol(R) 10 mg was injected into subtenon space after cryotherapy in the right eyes only. The VFP readings were taken 1, 3, 5, 7, 10, and 14 days after cryotherapy. In this experiment, cryotherapy did not increase the breakdown of BRB. But in the right eye, the severity of the breakdown of BRB was significantly lower than in the left eye 7 and 10 days after cryotherapy. These results suggest that Depomedrol(R) can decrease the severity of the breakdown of BRB after cryotherapy, and may be useful in the prevention of proliferative vitreoretinopathy (PVR).

The Effect of PRP on the Absorption of Vitreous Hemorrhage in Rabbit Eyes

The panretinal photocoagulation(PRP) is known to increase the absorption of fluid through the retinal pigment epithelium by destroying blood retinal barrier. Therefore we thought that PRP could increase vitreoretinal choroidal outflow in vitreous hemorrhage. In order to investigate the effect of PRP on the absorption of vitreous hemorrhage, we performed animal experiment with 12 rabbits divided into 4 groups, and the results were as follows; 1) In phakic eyes, the vitreous hemorrhage was absorbed faster in group with PRP than in group without PRP(p0.05).

Experimental Study on the Destruction and Recovery of the Blood Retinal Barrier after Photocoagulation and Cryotherapy in the Rabbits

The primary purpose of the study is to investigate the destruction and recovery of the blood retinal barrier after photocoagulation and cryotherapy in the rabbits. The 110 pigmented rabbits were used in this experiment. After photocagulation and cryotherapy we injected intravenousely a dose of 25 mg/kg of fluorescein sodium, and then sampled blood and vitreous and measured the concentration of fluorescein sodium by means of High Performance Liquid Chromatography. The calculated penetration ratio which indicates the destruction of the blood retinal barrier is obtained by dividing fluorescein sodium concentration of vitreous by integral of fluorescein sodium concentration of the plasma from 3 min to 60 min. Subsequently, fundus photography and enucleation for flat preparation were performed in each experimental rabbit. The fluorescein concentration of vitreous of the normal rabbit is 3.60 +/- 4.75 X 10(-9)gm/ml and its penetration ratio is 0.20 +/- 0.23 X 10(-6) min. After measuring the correlation between the frequency of photocoagulation and penetration ratio and between the frequency of cryotherapy and penetration ratio, we found out that the correlation coefficient was 0.885 and 0.909 respectively. And this experiment showed that penetration ratio was higher in cryotherapy group than in photocoagulation group. In addition, we divided these experimental animals into 4 groups, mild and severe cryotherapy groups and lighter and heaver photocoagulation groups, and assessed the penetration ratio of these four groups at 1,3,7,14,28, and 42 days after treatment. As a result, penetration ratio was highest at 3 days after treatment and was almost back to normal by 42 days in all experimental groups except in severe cryotherapy group. Compared with photocagulation groups, cryotherapy groups showed more extensive destruction and delayed recovery of the blood retinal barrier. In fundus photography, in the photocoagulation groups white patch was developed after treatment, at 7 days white patches disappeared and were replaced by pigmented and scarred tissue; by 42 days the margin of these lesions was indistinct and the lesions were changed into relatively small scarred patches. On the other hand, in the cryotherapy groups the thick round white patch wasdeveloped after treament, at 7 days large round white patches disappeared and were replaced by pigmented and scarred tissue; by 42 days the lesions were replaced by large scarred patches with pigmentation and depigmentation. In flat preparation, in the photocoagulation groups central necrotic zone and intermediate zone with hyperpigmentation and peripheral zone with hypopigmentation was presented at 1 day. In the cryotherapy groups the diminished density, in the center and white ring at the margin was revealed at 1 day. From 7 days in photocogulation groups and from 14 days in the cryotherapy groups, retinal pigment epithelium began to show proliferation and by 42 days, retinal pigment epithelial layer of both groups except severe cryotherapy group was replaced by relatively normal retinal pigment epithelium.

Changes of Blood-Retinal Barrier Induced by Destruction of the Retinal Pigment Epithelium

The author studied the functional derangement of blood-retinal barrier induced by destruction of the pigment epithelial cells of the retina. Sodium iodate, which was well known to exert a selectively destructive action to the retinal pigment epithelial cells, was injected to the rabbits intravenously(60mg/kg of body weight). Eyes were enucleated 2 days and 4 days after sodium iodate injection and examined by electron microscope. Some of the tissue were fixed in colloid lanthanum, to investigate the changes of the permeability of plasma membrane in accordance with cellular damages induced by sodium iodate. The permeability of the blood-retinal barrier was also studied after intravenous(200mg/kg) or intraocular(4 microgram/20ml of saline) injection of horseradish peroxidase(HRP). The results obtained were summarized as the following: Sodium iodate induced patchy areas of loss of pigment epithelial cells after 2 days, which were more widespread and severe after 4 days with regenerative activities. Loss of outer segment and mitochondrial swelling of the inner segment of visual cells were also noted after 4 days. Colloidal lanthanum penetrated into the mitochondria of pigment epithelial cells at 2 days after sodium iodate injection, which was extended to the mitochondria of inner segment of visual cells after 4 days. Intraocularly injected HRP appeared from the internal limiting membrane to Bruch's membrane after 2 days. Intravenously injected HRP appeared from the Bruch's membrane to ganglion cell layer after 2 days, which were extended to the vitreal cavity. The results suggested that the damage of the pigment epithelial cells induced by sodium iodate destroy blood-retinal barrier. HRP exudation is more extensive in direction of retina to choroid than choroid to retina.

A Study on the Changes in Blood-Retinal Barrier After Vitreal Injection of Silicone Oil in Rabbits

The blood-retinal barrier, that outward movement from the eye into the blood appears to predominate and the penetration into the eye of only a few important metabolic products is allowed, is particularly tight non-leaky junction on blood ocular barrier. In order to investigate the extent of destruction in blood retinal barrier after injection of silicone oil in the vitreous of the rabbit, author serially studied the change of fluorescein concentration in vitreous using the HPLC, ERG changes, and histopathologic changes of the retina. The results were belows, 1. The changes of fluorescein concentration in the vitreous showed increasing tendency, with time. The concentration of fluorescein were 0.008 micro/ml in 1st week, 0.069 micro/ml in 2nd week, 0.058 micro/ml in 3rd week, 0.325 micro/ml in 4th week, respectively. 2. The amplitude of photopic b wave in normal rabbit was lower than that of scotopic b wave, but there wasn't significant difference in latency between photopic and scotopic b wave. The amplitudes of b wave in silicone oil injected eyes showed lower voltage than that of normal eyes. 3. The amplitudes of b wave in silicone oil injected eyes were 210 micro V at 1st week, 150 micro V at 2nd week, 72 micro V at 3rd week, 63 micro V at 4th week in average. They showed prominent decrease in voltage from 1st week to 3rd week, but decreased slightly from 3rd week to 4th week. 4. Histopathologically, the retinal changes of the silicone oil injected eyes in 3rd week showed increased cellularity in ganglion cell layer and presented many vacuoles. In 4th week, ganglion cells were decreased but vacuoles were more increased in number.