Vitreous Protein Concentration Research Articles

Evaluation of Neopterin Levels in an Endotoxin-Induced Experimental Uveitis Model

Background: In this study, NP levels of intraocular fluids and serum were analyzed in the endotoxin-induced uveitis model. Methods: Intravitreal injection of 0.05 ml E. Coli lipopolysaccharide (IVT LPS) has been performed into the right eyes of 14 rabbits. Animals were divided into two groups. Group 1 (n = 7) sacrificed 24 hours after the intravitreal injection, and group 2 (n = 7) 72 hours after the intravitreal injection. Aqueous fluid, vitreous and serum samples were drawn at the time of sacrifice; histopathological changes were also examined. Results: Significantly elevated aqueous and vitreous NP levels were observed in IVT LPS injected eyes. In IVT LPS injected eyes, aqueous NP levels showed a significant decrease in 72 hours (p < 0.05), whereas vitreous NP concentrations significantly increased in 72 hours (p < 0.05). Both aqueous and vitreous protein concentrations were significantly higher in IVT LPS injected eyes. Histopathologic evaluation revealed that, in the first 24 hours, inflammation was significant in choroid and ciliary body. Retinal histopathological changes were observed mainly at 72 hours. Conclusions: This study demonstrates that neopterin levels correlate with early intraocular inflammatory response in an endotoxin-induced uveitis model.

Pharmacokinetics and efficacy of topically applied nonsteroidal anti-inflammatory drugs in retinochoroidal tissues in rabbits.

PurposeTo evaluate the pharmacokinetics and efficacy of topically applied nonsteroidal anti-inflammatory drugs (NSAIDs) in the retinochoroidal tissues of rabbits.MethodsThe cyclooxygenase (COX) inhibitory activity of diclofenac, bromfenac, and amfenac, an active metabolite of nepafenac, were determined using human-derived COX-1 and COX-2. Each of the three NSAIDs was applied topically to rabbits, and after 0.5 to 8 hrs, the concentration of each drug in the aqueous humor and the retinochoroidal tissues was measured by liquid chromatography-tandem mass spectrometry. The pharmacokinetics of the drugs in the tissues after repeated doses as is done on patients was calculated by a simulation software. The inhibitory effect of each NSAID on the breakdown of the blood-retinal barrier was assessed by the vitreous protein concentration on concanavalin A-induced retinochoroidal inflammation in rabbits.ResultsThe half-maximal inhibitory concentration (IC50) of diclofenac, bromfenac, and amfenac was 55.5, 5.56, and 15.3 nM for human COX-1, and 30.7, 7.45, and 20.4 nM for human COX-2, respectively. The three NSAIDs were detected in the aqueous humor and the retinochoroidal tissue at all-time points. Simulated pharmacokinetics showed that the levels of the three NSAIDs were continuously higher than the IC50 of COX-2, as an index of efficacy, in the aqueous humor, whereas only the bromfenac concentration was continuously higher than the IC50 at its trough level in the retinochoroidal tissues. The intravitreous concentration of proteins was significantly reduced in rabbits that received topical bromfenac (P = 0.026) but not the other two NSAIDs.ConclusionsTopical bromfenac can penetrate into the retinochoroidal tissues in high enough concentrations to inhibit COX-2 and exerts its inhibitory effect on the blood-retinal barrier breakdown in an experimental retinochoroidal inflammation in rabbits. Topical bromfenac may have a better therapeutic benefit than diclofenac and nepafenac for retinochoroidal inflammatory diseases.

Plasma and vitreous fluid levels of Dickkopf-1 in patients with diabetic retinopathy

Dickkopf-1 (DKK-1) is a secreted inhibitor of the Wnt/β-catenin signaling pathway, which plays a pathogenic role in diabetic retinopathy (DR). We aimed to investigate whether DKK-1 levels in the plasma and the vitreous are associated with DR in type 2 diabetes mellitus (DM) patients. Case-control study: plasma samples were collected from 125 type 2 DM including 81 DR (29 non-proliferative DR (NPDR) and 52 proliferative DR (PDR)), 44 non-DR patients (NDR), and 100 non-diabetic controls. Undiluted vitreous fluid samples were obtained from 30 PDR and 25 non-diabetic patients. DKK-1 concentrations in samples were determined using enzyme-linked immunosorbent assay. Variables were compared with the Kruskal-Wallis H test, Mann-Whitney U-test, and χ(2)-test, when appropriate. Plasma DKK-1 levels were significantly lower in DR patients (median: 465.77 pg/ml, range: 137.11-1190.31) than in non-diabetic controls (656.83 pg/ml, 171.63-1795.08; P<0.001) and NDR patients (693.04 pg/ml, 305.43-1218.35; P<0.001). Furthermore, DKK-1 levels were lower in PDR patients (425.21 pg/ml, 137.10-1077.32) compared with NPDR patients (594.86 pg/ml, 256.36-1393.27; P=0.003). Vitreous absolute DKK-1 levels in PDR patients (259.04 pg/ml, 104.44-596.96) were higher than in non-diabetic controls (138.26 pg/ml, 18.69-239.52; P<0.001). After normalizing by total vitreous protein concentrations, however, there was no significant difference between the groups. DKK-1 levels in vitreous were lower than those in plasma in both groups (P<0.001 for controls; P=0.002 for PDR patients). Decreased plasma DKK-1 levels, which may contribute to the Wnt pathway activation, are associated with the presence and progression of DR, and have potential to become a biomarker for DR.

Intravitreous hepatocyte growth factor in patients with proliferative diabetic retinopathy: A case-control study

The aim of the present study was to evaluate the vitreous levels of hepatocyte growth factor (HGF) in patients with proliferative diabetic retinopathy (PDR) and to investigate its relationship with vascular endothelial growth factor (VEGF) and retinopathy activity. In addition, the relationship between intravitreous HGF levels and the presence of epiretinal membranes (ERM), as well as the expression of c-Met in ERM were also investigated. In this case-control study, serum and vitreous samples as well as ERM specimens were obtained during vitrectomy from 28 diabetic patients with PDR and 30 non-diabetic control subjects. HGF and VEGF were determined by ELISA and c-Met expression by immunohistochemistry. Vitreal levels of both VEGF and HGF were higher in patients with PDR in comparison with the control group ( p < 0.0001). However, after correcting for total vitreous protein concentration, HGF (ng/mg of proteins) was lower in diabetic patients than in non-diabetic control subjects ( p = 0.02). No correlation was detected between the vitreal levels of HGF and VEGF. In addition, intravitreous VEGF but not HGF was found to be related to PDR activity. Both diabetic patients and non-diabetic patients in whom ERM had been excised presented higher HGF intravitreous levels. Finally, a significant expression of c-Met in ERM membranes were observed in both diabetic patients with PDR and in non-diabetic subjects. In conclusion, both HGF and VEGF increased, but were not related, in the vitreous fluid of diabetic patients with PDR. Our findings suggest that HGF is related to pathological conditions in which fibroproliferative processes or wound healing are involved rather than with angiogenesis itself.

The effect of partial vitrectomy on blood-ocular barrier function in the rabbit

Purpose. To compare ocular vascular permeability in the rabbit after vitrectomy as assessed by contrast-enhanced magnetic imaging (CE-MRI) and measurements of aqueous and vitreous humor protein concentration. Methods. Partial vitrectomies were performed, irrigating with BSS ® or BSS PLUS ®. Post-operative vascular leakage was determined by CE-MRI following intravenous administration of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA). Aqueous and vitreous protein concentrations were quantified by standard biochemical assay. ERG evaluations were performed on postoperative days 1, 3, and 7. Results. Using BSS as irrigant, breakdown of the inner blood-retinal barrier (BRB) occurred in 4/7 eyes on post-operative day 1. The rate of Gd-DTPA leakage was significantly greater on postoperative day 1 than that in unoperated, control eyes, but declined ˜50% by day 3. At both time points, outer BRB breakdown was restricted to the sclerotomy wounds. No BRB leakage was detectable in control eyes. Blood-aqueous barrier (BAB) leakage was bilateral on day 1. Significantly greater Gd-DTPA leakage occurred in the operated eye than in the nonsurgical contralateral eye. On day 3, ˜40% bilateral reduction in leakage indicated resolution of BAB leakage. Notably, Gd-DTPA leakage of the BAB and BRB was significantly reduced in the BSS PLUS treated group. In contrast to MRI assessments, protein concentrations of the aqueous and vitreous in the surgical eye showed no detectable differences between BSS and BSS PLUS. Concurrent with the transient loss of ocular barrier function, ERG responses also declined. However, by day 7 greater than 90% recovery was noted in BSS PLUS treated animals but not in the BSS treatment group. Conclusions. CE-MRI is capable of detecting subtle changes in vascular permeability following ocular surgery. Advantages of using BSS PLUS compared to BSS as the irrigating solution can be detected using this technique. BSS PLUS’s protection of barrier function is consistent with a rapid recovery in retinal function not observed in BSS treated eyes.

Risk factors for proliferative vitreoretinopathy after primary vitrectomy: a prospective study

AIMTo assess clinical variables and vitreous protein as risk factors for the development of postoperative proliferative vitreoretinopathy (PVR).METHODSA prospective study was conducted on 140 patients with a rhegmatogenous retinal detachment...

SHORT COMMUNICATION: The vitreous protein concentration is increased prior to neovascularization in experimental ROP

PURPOSE. To test the hypothesis that the vitreous protein content is altered prior to the development of neovascularization in an experimental model of retinopathy of prematurity (ROP). METHODS. Newborn rats underwent either a variable oxygen exposure or room air exposure following birth. On day 13 or 14, two days prior to neovascularization, the steady state vitreous and plasma total protein levels in room-air controls or variable-oxygen-exposed newborn rats were determined; similar measurements were also made for control adult rats. RESULTS. There was a significant difference (P < 0.05, 2-tailed t-test) in the vitreous protein concentration between the age-matched control and experimental newborn rats. The protein level in the ROP rat plasma was not significantly (P > 0.05) different from that in the age-matched control animals. The vitreous-to-plasma-protein ratios of both the control and ROP new- born animals were significantly greater (P < 0.05) than that in the adults. CONCLUSIONS. The results of this study demonstrate, for the first time, increased vitreous protein levels prior to the development of neovascularization in the newborn rat model of ROP. In addition, developmental changes in vitreous protein levels were identified. The role of developmental and pathologic alterations in the blood-ocular barriers in this study is discussed.

Transscleral Contact Retinal Photocoagulation With an 810nm Semiconductor Diode Laser

ABSTRACT Since the 810-nm wavelength has marked transmissibility through the sclera and absorption by melanin, ft would be ideal for transscleral photocoagulation. We performed experiments to determine if consistent transscleral chorioretinal lesions could be produced in Dutch belted pigmented rabbits using the 810-nm laser, and if this modality caused less blood-retinal barrier disruption than retinal cryopexy of clinically equivalent treatment areas. The laser applications produced whitish to grayish-white retinal lesions when the surgeon, under direct visualization, used low powers and long durations (5 to 10 seconds), and controlled the treatment duration. Histopathologic evaluation of a lesion demonstrated an intact sclera overlying the chorioretinal lesion. Vitreous protein concentration, which was measured to assess bloodretinal barrier disruption, was significantly less in eyes treated with transscleral photocoagulation than in eyes treated with cryopexy of clinically equivalent treatment areas. We conclude that transscleral 810nm laser treatment may be a viable clinical alternative to retinal cryopexy.

Role of the lens and vitreous humor in the refractive properties of the eyes of three strains of goldfish

Certain strains of goldfish are characterized by large bulging eyes which have been shown to be extremely myopic. Such myopia has been hypothesized to have its origin in enlargement of the posterior chamber of the eye. The focal length of the lens was found to be similar for paraxial and marginal lens zones in common, Chinese Black Moor and Celestial goldfish, thus providing indirect support of that hypothesis. Freeze-sectioning study of intraocular dimensions shows that the axial length of the vitreous chamber of the common goldfish eye is about 37% of total axial length. In contrast, it becomes more than 70% of axial length in Chinese Black Moors and Celestials. An examination of vitreous protein concentration indicates that ocular enlargement in Chinese Black Moors and in Celestials is related to an increase in vitreous quantity, and is accompanied by vitreous dilution. The fact that similar findings are reported in the case of experimental myopia in chicks, suggests the existence of a fundamental mechanism of refractive development for the vertebrate eye.

Experimental retinal detachment. IX. Aqueous, vitreous, and subretinal protein concentrations.

Unilateral rhegmatogenous retinal detachments were created in seven cynomolgus monkeys. Six months later, aqueous, vitreous, and subretinal fluid protein concentrations were measured. In fellow eyes with vitrectomy alone, mean aqueous and vitreous protein concentrations were 0.28 and 0.23 mg/mL, respectively. In eyes with retinal detachments, mean aqueous, vitreous, and subretinal protein levels were 1.46, 2.66, and 4.74 mg/mL, respectively. Eyes with a large retinal hole (greater than or equal to 1 disc diameter) had a subretinal fluid-vitreous protein concentration ratio of 1.1, indicating free diffusional exchange between the vitreous and subretinal space. In eyes with a small retinal hole (less than or equal to 1/4 disc diameter), the corresponding ratio was 4.0. These findings are consistent with the hypothesis that fluid moves from the vitreous cavity through the retinal hole into the subretinal space, preventing back diffusion of protein from the subretinal space into the vitreous, and allowing accumulation of protein in the subretinal space.

Intraocular fluid dynamics. Measurements following vitrectomy and intraocular sulfur hexafluoride administration.

Partial vitrectomies were performed in rabbits, replacing 40% of initial vitreous volume with 100% sulfur hexafluoride, and concentrations of sodium, potassium, calcium, magnesium, ascorbate, and protein were determined in aqueous and vitreous at 10, 14, 21, 28, 56, and 110 days. There were significant increases of potassium, calcium, magnesium, and protein above control values at varying times throughout the study. Vitreous potassium concentration was decreased at 14 and 21 days. All other measurements were similar to control values. Results of studies indicate that, following vitrectomy in rabbits, the blood-retinal barrier can re-form in 14 days and blood-aqueous barrier in ten days. However, a greater than normal exchange diffusion of these measured substances occurs between aqueous and vitreous through 21 days. Four eyes with cataracts, vitreous membranes, and/or detached retinas demonstrated elevated aqueous and vitreous protein concentrations through 110 days, although other measurements returned to normal levels.