Exploring the Impact of Saccharin on Neovascular Age-Related Macular Degeneration: A Comprehensive Study in Patients and Mice

Purpose

We aimed to determine the impact of artificial sweeteners (AS), especially saccharin, on the progression and treatment efficacy of patients with neovascular age-related macular degeneration (nAMD) under anti-vascular endothelial growth factor (anti-VEGF-A) treatment.

Methods

In a cross-sectional study involving 46 patients with nAMD undergoing intravitreal anti-VEGF therapy, 6 AS metabolites were detected in peripheral blood using liquid chromatography - tandem mass spectrometry (LC-MS/MS). Disease features were statistically tested against these metabolite levels. Additionally, a murine choroidal neovascularization (CNV) model, induced by laser, was used to evaluate the effects of orally administered saccharin, assessing both imaging outcomes and gene expression patterns. Polymerase chain reaction (PCR) methods were used to evaluate functional expression of sweet taste receptors in a retinal pigment epithelium (RPE) cell line.

Results

Saccharin levels in blood were significantly higher in patients with well-controlled CNV activity (P = 0.004) and those without subretinal hyper-reflective material (P = 0.015). In the murine model, saccharin-treated mice exhibited fewer leaking laser scars, lesser occurrence of bleeding, smaller fibrotic areas (P < 0.05), and a 40% decrease in mononuclear phagocyte accumulation (P = 0.06). Gene analysis indicated downregulation of inflammatory and VEGFR-1 response genes in the treated animals. Human RPE cells expressed taste receptor type 1 member 3 (TAS1R3) mRNA and reacted to saccharin stimulation with changes in mRNA expression.

Conclusions

Saccharin appears to play a protective role in patients with nAMD undergoing intravitreal anti-VEGF treatment, aiding in better pathological lesion control and scar reduction. The murine study supports this observation, proposing saccharin's potential in mitigating pathological VEGFR-1-induced immune responses potentially via the RPE sensing saccharin in the blood stream.

Islet Co-Expression of CD133 and ABCB5 in Human Retinoblastoma Specimens

BACKGROUND

The role of CD133 und ABCB5 is discussed in treatment resistance in several types of cancer. The objective of this study was to evaluate whether CD133⁺/ABCB5⁺ colocalization differs in untreated, in beam radiation treated, and in chemotherapy treated retinoblastoma specimens. Additionally, CD133, ABCB5, sphingosine kinase 1, and sphingosine kinase 2 gene expression was analyzed in WERI-RB1 (WERI RB1) and etoposide-resistant WERI RB1 subclones (WERI ETOR).

METHODS

Active human untreated retinoblastoma specimens (n = 12), active human retinoblastoma specimens pretreated with beam radiation before enucleation (n = 8), and active human retinoblastoma specimens pretreated with chemotherapy before enucleation (n = 7) were investigated for localization and expression of CD133 and ABCB5 by immunohistochemistry. Only specimens with IIRC D, but not E, were included in this study. Furthermore, WERI RB1 and WERI ETOR cell lines were analyzed for CD133, ABCB5, sphingosine kinase 1, and sphingosine kinase 2 by the real-time polymerase chain reaction (RT-PCR).

RESULTS

Immunohistochemical analysis revealed the same amount of CD133⁺/ABCB5⁺ colocalization islets in untreated and treated human retinoblastoma specimens. Quantitative RT-PCR analysis showed a statistically significant upregulation of CD133 in WERI ETOR (p = 0.002). No ABCB5 expression was detected in WERI RB1 and WERI ETOR. On the other hand, SPHK1 (p = 0.0027) and SPHK2 (p = 0.017) showed significant downregulation in WERI ETOR compared to WERI RB1.

CONCLUSIONS

CD133⁺/ABCB5⁺ co-localization islets were noted in untreated and treated human retinoblastoma specimens. Therefore, we assume that CD133⁺/ABCB5⁺ islets might play a role in retinoblastoma genesis, but not in retinoblastoma treatment resistance.

Effects of TNFα receptor TNF-Rp55- or TNF-Rp75- deficiency on corneal neovascularization and lymphangiogenesis in the mouse

Tumor necrosis factor (TNF)α is an inflammatory cytokine likely to be involved in the process of corneal inflammation and neovascularization. In the present study we evaluate the role of the two receptors, TNF-receptor (TNF-R)p55 and TNF-Rp75, in the mouse model of suture-induced corneal neovascularization and lymphangiogenesis. Corneal neovascularization and lymphangiogenesis were induced by three 11-0 intrastromal corneal sutures in wild-type (WT) C57BL/6J mice and TNF-Rp55-deficient (TNF-Rp55d) and TNF-Rp75-deficient (TNF-Rp75d) mice. The mRNA expression of VEGF-A, VEGF-C, Lyve-1 and TNFα and its receptors was quantified by qPCR. The area covered with blood- or lymphatic vessels, respectively, was analyzed by immunohistochemistry of corneal flatmounts. Expression and localization of TNFα and its receptors was assessed by immunohistochemistry of sagittal sections and Western Blot. Both receptors are expressed in the murine cornea and are not differentially regulated by the genetic alteration. Both TNF-Rp55d and TNF-Rp75d mice showed a decrease in vascularized area compared to wild-type mice 14 days after suture treatment. After 21 days there were no differences detectable between the groups. The number of VEGF-A-expressing macrophages did not differ when comparing WT to TNF-Rp55d and TNF-Rp75d. The mRNA expression of lymphangiogenic markers VEGF-C or LYVE-1 does not increase after suture in all 3 groups and lymphangiogenesis showed a delayed effect only for TNF-Rp75d. TNFα mRNA and protein expression increased after suture treatment but showed no difference between the three groups. In the suture-induced mouse model, TNFα and its ligands TNF-Rp55 and TNF-Rp75 do not play a significant role in the pathogenesis of neovascularisation and lymphangiogenesis.

FLASH proton irradiation setup with a modulator wheel for a single mouse eye

PURPOSE

Recent studies indicate that FLASH irradiation, which involves ultra-high dose rates in a short time window (usually >40 Gy/s in <500 ms), might be equally efficient against tumors but less harmful to healthy tissues, compared to conventional irradiation with the same total dose. Aiming to verify the latter claim for ocular proton radiotherapy, in vivo experiments with mice are being carried out by Charité - Universitätsmedizin Berlin. This work presents the implemented setup for delivering FLASH proton radiation to a single eye of mice at the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB).

MATERIALS AND METHODS

The HZB cyclotron is tuned to provide a high-intensity 68 MeV focused proton beam. Outside the vacuum beamline, the protons hit a single scatterer, which also serves as range shifter, and a rotating modulator wheel, which produces a flat depth-dose distribution. Two transmission ionization chambers in between, read out by fast electronics, are used as dose monitors for triggering an in-vacuum beam shutter, which blocks the beam once the desired dose has been delivered. A collimating aperture shapes the radiation field at the isocenter, which is measured by a radioluminescent screen and a CCD camera. At the same position, a parallel-plate ionization chamber of type Advanced Markus^® is used for absolute dosimetry and characterization of the spread-out Bragg peak inside a water phantom. A thin-foil mirror of adjustable tilt in the beam path assists the correct alignment of the target through side illumination. Radiochromic films of type EBT3 are used to supplement the dosimetry and assist the alignment.

RESULTS

A dose rate of 75 Gy/s has been measured, delivering within 200 ms 15 Gy (RBE) with a reproducibility better than ±1%. A depth-dose curve with a range of 5.2 mm in water, 0.9 mm distal fall-off (90%-10%), and ±2.5% ripple has been demonstrated, with a PTV of 6.3 mm diameter, 1.7 mm lateral penumbra (90%-10%), 8% uniformity, and 3% symmetry.

CONCLUSIONS

The implemented setup is able to accommodate ocular irradiation of narcotized mice with protons, targeting selectively the left or the right eye, under conventional and FLASH conditions. Switching between these two modes can be done within half an hour, including the calibration of the dose monitors and the verification of the dose delivery. Further upgrades are planned after the completion of the on-going experiment.

Lack of netrin-4 alters vascular remodeling in the retina

PURPOSE

Netrin-4 (NTN4) is a protein that plays an important role in the regulation of angiogenesis in the pathological retina. Some evidences show that it can also have a role in inflammation and vascular stability. We will explore these questions in vivo in the mature mouse retina.

METHODS

We created a NTN4 knockout that expresses EGFP in mononuclear phagocytes (CSFR1-positive cells) to track inflammation in vivo in the retina by scanning laser ophthalmoscopy (SLO). Fundus angiography permitted to study blood vessels. Retinal function was assessed with electroretinography (ERG).

RESULTS

Lack of NTN4 leads to an increased amount of amoeboid mononuclear phagocytes in the adult retina, and blood vessels displayed increased tortuosity when compared with the wildtype. Inner retina function also seemed affected in NTN4 null. Lack of NTN4 resulted in a higher persistence of hyaloid artery and spontaneous leakage in the adult retina. No differences were found regarding vessel bifurcation, vessel width, or vein/artery ratio.

CONCLUSIONS

These in vivo data show for the first time that lack of NTN4 induces changes in the retinal vascular phenotype in a non-pathological scenario. This evidence widens the role of NTN4 as a guidance cue in vascular remodeling.

Systemic Rho-kinase inhibition using fasudil in mice with oxygen-induced retinopathy

PURPOSE

To investigate the influence of the selective Rho-kinase (ROCK) inhibitor, fasudil, on the mRNA level of proinflammatory factors and the retinal vascular development in mice with oxygen-induced retinopathy (OIR).

METHODS

C57BL/6J mice underwent standard protocol for OIR induction from postnatal days 7 to 12. Subsequently, they received a daily intraperitoneal injection of fasudil or sodium chloride from P12 to P16. Analyses were performed using vascular staining on retinal flat mounts, RNA expression by qPCR, and immunohistochemistry on paraffin sections.

RESULTS

On retinal flat mounts, the proportion of avascular area and tuft formation did not differ between the fasudil and NaCl group. Immunohistochemical staining revealed a less intense staining with inflammatory markers after fasudil. Nevertheless, there were no differences on RNA level between the two groups.

CONCLUSIONS

In conclusion, our findings support that daily systemic application of fasudil does not decrease retinal neovascularization in rodents with oxygen-induced retinopathy. The results of our study together with the controversial results on the effects of different ROCK inhibitors from the literature makes it apparent that effects of ROCK inhibition are more complex, and further studies are necessary to analyze its potential therapeutic effects.

Local partial depletion of CD11b+ cells and their influence on choroidal neovascularization using the CD11b-HSVTK mouse model

PURPOSE

To assess the influence of retinal macrophages and microglia on the formation of choroidal neovascularization (CNV). Therefore, we used a transgenic mouse (CD11b-HSVTK) in which the application of ganciclovir (GCV) results in a depletion of CD11b⁺ cells.

METHODS

We first investigated if a local depletion of CD11b⁺ macrophages and microglia in the retina is feasible. In a second step, the influence of CD11b⁺ cell depletion on CNV formation was analysed. One eye of each CD11b-HSVTK mouse was injected with GCV, and the fellow eye received sodium chloride solution (NaCl). Cell counting was performed at day 3 and 7 (one injection) or at day 14 and 21 (two injections). Choroidal neovascularization (CNV) was induced by argon laser and analysed at day 14.

RESULTS

The most effective CD11b⁺ cell depletion was achieved 7 days after a single injection and 14 days after two injections of GCV. After two injections of GCV, we found a significant reduction of CD11b⁺ cells in central (52 ± 23.9 cells/mm² ) and peripheral retina (53 ± 20.6 cells/mm² ); compared to eyes received NaCl (216 ± 49.0 and 210 ± 50.5 cells/mm² , p < 0.001, respectively). Regarding CNV areas, no statistical significance was found between the groups.

CONCLUSION

The CD11b-HSVTK mouse is a feasible model for a local depletion of CD11b⁺ cells in the retina. Nevertheless, only a partial depletion of CD11b⁺ cells could be achieved compared to baseline data without any intravitreal injections. Our results did not reveal a significant reduction in CNV areas. In the light of previous knowledge, the potential influence of systemic immune cells on CNV formation might be more relevant than expected.

Dataset on the activation of Müller cells through macrophages upon hypoxia in the retina

The dataset presented in this article complements the article entitled “Myeloid cells contribute indirectly to VEGF expression upon hypoxia via activation of Müller cells” (C. Nürnberg, N. Kociok, C. Brockmann, T. Lischke, S. Crespo-Garcia, N. Reichhart, S. Wolf, R. Baumgrass, S.A. Eming, S. Beer-Hammer, and A.M. Joussen). This complementary dataset provides further insight into the experimental validation of the VEGF^fl/fl LysMCre (here named VEGF^mcko) knockout model used in the main article through genomic and quantitative Real-Time PCR in various murine tissues as well as additional flow cytometry data and immunohistochemical stainings. By providing these data, we aim to enable researcher to reproduce and critically analyze our data.

Spatial distribution of CD115+ and CD11b+ cells and their temporal activation during oxygen-induced retinopathy in mice

PURPOSE

The model of oxygen-induced retinopathy (OIR) is widely used to analyze pathomechanisms in retinal neovascularization. Previous studies have shown that macrophages (MP) play a key role in vessel formation in OIR, the influence of microglia (MG) having been discussed. The aim of our study was to analyze the spatial and temporal distribution and activation of MP/MG expressing CD115 and CD11b during the process of neovascularization in OIR.

METHODS

We used MacGreen mice expressing the green fluorescence protein (GFP) under the promoter for CD115. CD115⁺ cells were investigated in vivo by scanning laser ophthalmoscopy at postnatal days (P) 17 and 21 in MacGreen mice with OIR (75% oxygen from P7 to P12), and were compared to MacGreen room-air controls. In addition MP/MG were examined ex vivo using immunohistochemistry for CD11b⁺ detection on retinal flatmounts at P14, P17, and P21 of wild type mice with OIR.

RESULTS

In-vivo imaging revealed the highest density of activated MP/MG in tuft areas at P17 of MacGreen mice with OIR. Tufts and regions with a high density of CD115⁺ cells were detected close to veins, rather to arteries. In peripheral, fully vascularized areas, the distribution of CD115⁺ cells in MacGreen mice with OIR was similar to MacGreen room-air controls. Correspondingly, immunohistochemical analyses of retinal flatmounts from wild type mice with OIR induction revealed that the number of CD11b⁺ cells significantly varies between vascular, avascular, and tuft areas as well as between the retinal layers. Activated CD11b⁺ cells were almost exclusively found in avascular areas and tufts of wild type mice with OIR induction; here, the proportion of activated cells related to the total number of CD11b⁺ cells remained stable over the course of time.

CONCLUSIONS

Using two different approaches to monitor MP/MG cells, our findings demonstrated that MP/MG concentrate within pathologically vascularized areas during OIR. We were able to clarify that reactive changes of CD11b⁺ cell distribution to OIR primarily occur in the deep retinal layers. Furthermore, we found the highest proportion of activated CD11b⁺ cells in regions with pathologic neovascularization processes. Our findings support previous reports about activated MP/MG guiding revascularization in avascular areas and playing a key role in the formation and regression of neovascular tufts.

Inhibition of Placenta Growth Factor Reduces Subretinal Mononuclear Phagocyte Accumulation in Choroidal Neovascularization

Purpose

The cellular immune response driven by mononuclear phagocytes (MPs) is crucial for choroidal neovascularization (CNV) progression. Case reports show that a switch from pure anti-vascular endothelial growth factor-A (VEGF-A) intravitreal treatment to aflibercept, a drug with combined anti-VEGF-A and anti-placenta growth factor (PlGF) activity, can be beneficial for patients who do not respond to anti-VEGF-A alone. Since MPs harbor VEGFR1, we hypothesize that the interplay of P1GF/vascular endothelial growth factor receptor 1 (VEGFR1) in immune cells plays a pivotal role for CNV.

Methods

CNV was induced with laser, and immune cells and neovascularization were analyzed in vivo and ex vivo. Immunohistochemistry was employed for protein detection. Differential expression of angiogenic factors and macrophage polarization markers were assessed by quantitative PCR (qPCR). One day after laser, intravitreal injection of aflibercept or anti-PlGF was performed.

Results

In the early inflammatory phase after laser, Plgf but not Vegfa was significantly upregulated. VEGF-A upregulation is limited to the scar, whereas PlGF shows a wider distribution. M1 (proinflammatory) macrophage markers were upregulated in the early phase of CNV. However, M2 (proangiogenic) markers showed more inconsistent dynamics. We demonstrated that both aflibercept and anti-PlGF treatments decrease the overall amount of activated subretinal MPs, and especially of those expressing PlGF. These data correlated with a reduction in leakage associated to CNV. Aflibercept showed a stronger reduction in both parameters.

Conclusions

The results hint at an interplay between PlGF/VEGFR1 and MPs that is important in the early phase of CNV. A combined inhibition of VEGF-A and PlGF is superior to a specific anti-PlGF treatment in terms of subretinal MP recruitment.

Myeloid cells contribute indirectly to VEGF expression upon hypoxia via activation of Müller cells

Anti-VEGF-directed therapies have been a milestone for treating retinal vascular diseases. Depletion of monocyte lineage cells suppresses pathological neovascularization in the oxygen-induced retinopathy mouse model. However, the question whether myeloid-derived VEGF-A expression is responsible for the pathogenesis in oxygen-induced retinopathy remained unknown. We analyzed LysMCre-driven myeloid cell-specific VEGF-A knockout mice as well as mice with complete depletion of circulating macrophages through clodronate-liposome treatment in the oxygen-induced retinopathy model by immunohistochemistry, qPCR, and flow cytometry. Furthermore, we analyzed VEGF-A mRNA expression in MIO-M1 cells alone and in co-culture with BV-2 cells in vitro. The myeloid cell-specific VEGF-A knockout did not change relative retinal VEGF-A mRNA levels, the relative avascular area or macrophage/granulocyte numbers in oxygen-induced retinopathy and under normoxic conditions. We observed an insignificantly attenuated pathology in systemically clodronate-liposome treated knockouts but evident VEGF-A expression in activated Müller cells on immunohistochemically stained sections. MIO-M1 cells had significantly higher expression levels of VEGF-A in co-culture with BV-2 cells compared to cultivating MIO-M1 cells alone. Our data show that myeloid-derived cells contribute to pathological neovascularization in oxygen-induced retinopathy through activation of VEGF-A expression in Müller cells.

Netrin-4 Mediates Corneal Hemangiogenesis but Not Lymphangiogenesis in the Mouse-Model of Suture-Induced Neovascularization

Purpose

Netrin-4, a secreted protein, is found in the basement membrane of blood vessels and acts as a key regulator of angiogenesis. Here we investigated the role of Netrin-4 in the mouse-model of suture-induced corneal hem- and lymphangiogenesis.

Methods

Corneal hem- and lymphangiogenesis were induced in Netrin-4-deficient (Ntn4-/-) and wild-type (WT) mice by placing three 11-0 nylon sutures intrastromally. Fourteen days after suturing, the vascularized area was analyzed via corneal flat mount immunohistochemistry. Messenger RNA levels for VEGF-A, VEGF-C, Lyve-1, Netrin-4, Unc5H2, "deleted in colon cancer" receptor, and Neogenin in treated and nontreated mouse corneas, cultured human corneal keratocytes (HCK) and epithelial cells (HCEC+HCET) were analyzed by quantitative PCR.

Results

In wild-type mice, Netrin-4 mRNA expression in the cornea decreased in growing corneal neovascularization after suturing. Correspondingly, Ntn4-/- mice showed an increased vascularized area compared to that in WT mice. Expression of VEGF-A mRNA was higher in Ntn4-/- versus WT mice. There was no Netrin-4 expression in lymphatic vessels and the area of lymphatic vascularization did not differ between Ntn4-/- and WT mice, nor did expression of VEGF-C and Lyve-1 mRNA. Human corneal epithelial cells showed mainly Netrin-4 mRNA expression, which increased after stimulation, while HCK demonstrated Unc5H2 mRNA expression. Expression of VEGF-A, Netrin-4, Unc5H2, and Neogenin mRNA in HCEC and HCK did not differ significantly between the serum-free condition and VEGF-A or Netrin-4 stimulation.

Conclusions

Absence of Netrin-4 increased corneal hemangiogenesis but not lymphangiogenesis in the mouse-model of suture-induced neovascularization. Netrin-4 acted as an antiangiogenic factor in the cornea, with which the healthy cornea is enriched via its expression by corneal epithelial cells.

Vascular-Associated Muc4/Vwf Co-Localization in Human Conjunctival Malignant Melanoma Specimens-Tumor Metastasis by Migration?

PURPOSE

To investigate whether vascular differentiation marker von Willebrand factor (vWf) and proliferation marker KI67 expression correlate with MUC4 localization around stromal tumor vascularization in human conjunctival malignant melanoma (CMM).

MATERIALS AND METHODS

For the purposes of this study, we analyzed samples from human CMMs (n = 4), conjunctival compound nevi (n = 7), and samples from healthy conjunctiva (n = 7) for MUC1, 4, and 16 by immunohistochemistry. To test CMM vessel association of MUC4, we investigated the co-localization of MUC4 with vWf or KI67 in human CMM specimens (n = 10) by immunohistochemistry. Also, we investigated the MUC4 localization around vessels of healthy conjunctiva (n = 10).

RESULTS

The immunohistochemical analysis demonstrated membrane-associated mucin expression in epithelia of CMM, nevi and healthy conjunctiva, whereas only MUC4 was localized perivascular in CMM tissue in this preliminary analysis. Co-staining analysis with vWf and KI67 demonstrated MUC4 localization around stromal vessels in human CMM specimens. In contrast, no MUC4 localization has been seen around healthy conjunctiva stroma vessels.

CONCLUSIONS

MUC4 was detected around vWf/KI67-positive CMM stromal vascular tissue, but not around healthy conjunctival stroma vessels. Therefore, we assume that MUC4 might play a role in tumor cell migration toward vessels inducing metastasis.

The TetO rat as a new translational model for type 2 diabetic retinopathy by inducible insulin receptor knockdown

AIMS/HYPOTHESIS

Although the renin-angiotensin system plays an important role in the progression of diabetic retinopathy, its influence therein has not been systematically evaluated. Here we test the suitability of a new translational model of diabetic retinopathy, the TetO rat, for addressing the role of angiotensin-II receptor 1 (AT1) blockade in experimental diabetic retinopathy.

METHODS

Diabetes was induced by tetracycline-inducible small hairpin RNA (shRNA) knockdown of the insulin receptor in rats, generating TetO rats. Systemic treatment consisted of an AT1 blocker (ARB) at the onset of diabetes, following which, 4-5 weeks later the retina was analysed in vivo and ex vivo. Retinal function was assessed by Ganzfeld electroretinography (ERG).

RESULTS

Retinal vessels in TetO rats showed differences in vessel calibre, together with gliosis. The total number and the proportion of activated mononuclear phagocytes was increased. TetO rats presented with loss of retinal ganglion cells (RGC) and ERG indicated photoreceptor malfunction. Both the inner and outer blood-retina barriers were affected. The ARB treated group showed reduced gliosis and an overall amelioration of retinal function, alongside RGC recovery, whilst no statistically significant differences in vascular and inflammatory features were detected.

CONCLUSIONS/INTERPRETATION

The TetO rat represents a promising translational model for the early neurovascular changes associated with type 2 diabetic retinopathy. ARB treatment had an effect on the neuronal component of the retina but not on the vasculature.

In vivo analysis of the time and spatial activation pattern of microglia in the retina following laser-induced choroidal neovascularization

Microglia play a major role in retinal neovascularization and degeneration and are thus potential targets for therapeutic intervention. In vivo assessment of microglia behavior in disease models can provide important information to understand patho-mechanisms and develop therapeutic strategies. Although scanning laser ophthalmoscope (SLO) permits the monitoring of microglia in transgenic mice with microglia-specific GFP expression, there are fundamental limitations in reliable identification and quantification of activated cells. Therefore, we aimed to improve the SLO-based analysis of microglia using enhanced image processing with subsequent testing in laser-induced neovascularization (CNV). CNV was induced by argon laser in MacGreen mice. Microglia was visualized in vivo by SLO in the fundus auto-fluorescence (FAF) mode and verified ex vivo using retinal preparations. Three image processing algorithms based on different analysis of sequences of images were tested. The amount of recorded frames was limiting the effectiveness of the different algorithms. Best results from short recordings were obtained with a pixel averaging algorithm, further used to quantify spatial and temporal distribution of activated microglia in CNV. Morphologically, different microglia populations were detected in the inner and outer retinal layers. In CNV, the peak of microglia activation occurred in the inner layer at day 4 after laser, lacking an acute reaction. Besides, the spatial distribution of the activation changed by the time over the inner retina. No significant time and spatial changes were observed in the outer layer. An increase in laser power did not increase number of activated microglia. The SLO, in conjunction with enhanced image processing, is suitable for in vivo quantification of microglia activation. This surprisingly revealed that laser damage at the outer retina led to more reactive microglia in the inner retina, shedding light upon a new perspective to approach the immune response in the retina in vivo.

Intravitreal inhibition of complement C5a reduces choroidal neovascularization in mice

PURPOSE

To investigate the influence of complement component C5a inhibition on laser-induced choroidal neovascularization (CNV) in mice using a C5a specific L-aptamer.

METHODS

In C57BL/6 J mice CNV was induced by argon-laser, C5a-inhibitor (NOX-D20) was intravitreally injected in three concentrations: 0.3, 3.0, and 30 mg/ml. The unPEGylated derivate (NOX-D20001) was applied at 3.0 mg/ml; the vehicle (5 % glucose) was injected in controls. Vascular leakage was evaluated using fluorescence angiography, CNV area was examined immunohistochemically. Activated immune cells surrounding the CNV lesion and potential cytotoxicity were analyzed.

RESULTS

Compared to controls, CNV areas were significantly reduced after NOX-D20 injection at a concentration of 0.3 and 3.0 mg/ml (p = 0.042; p = 0.016). NOX-D20001 significantly decreased CNV leakage but not the area (p = 0.007; p = 0.276). At a concentration of 30 mg/ml, NOX-D20 did not reveal significant effects on vascular leakage or CNV area (p = 0.624; p = 0.121). The amount of CD11b positive cells was significantly reduced after treatment with 0.3 and 3.0 mg/ml NOX-D20 (p = 0.027; p = 0.002). No adverse glial cell proliferation or increased apoptosis were observed at effective dosages.

CONCLUSIONS

Our findings demonstrate that the targeted inhibition of complement component C5a reduces vascular leakage and neovascular area in laser-induced CNV in mice. NOX-D20 was proven to be an effective and safe agent that might be considered as a therapeutic candidate for CNV treatment. The deficiency of activated immune cells highlights promising new aspects in the pathology of choroidal neovascularization, and warrants further investigations.

β-Secretase (BACE1) inhibition causes retinal pathology by vascular dysregulation and accumulation of age pigment

β-Secretase (BACE1) is a major drug target for combating Alzheimer's disease (AD). Here we show that BACE1(-/-) mice develop significant retinal pathology including retinal thinning, apoptosis, reduced retinal vascular density and an increase in the age pigment, lipofuscin. BACE1 expression is highest in the neural retina while BACE2 was greatest in the retinal pigment epithelium (RPE)/choroid. Pigment epithelial-derived factor, a known regulator of γ-secretase, inhibits vascular endothelial growth factor (VEGF)-induced in vitro and in vivo angiogenesis and this is abolished by BACE1 inhibition. Moreover, intravitreal administration of BACE1 inhibitor or BACE1 small interfering RNA (siRNA) increases choroidal neovascularization in mice. BACE1 induces ectodomain shedding of vascular endothelial growth factor receptor 1 (VEGFR1) which is a prerequisite for γ-secretase release of a 100 kDa intracellular domain. The increase in lipofuscin following BACE1 inhibition and RNAI knockdown is associated with lysosomal perturbations. Taken together, our data show that BACE1 plays a critical role in retinal homeostasis and that the use of BACE inhibitors for AD should be viewed with extreme caution as they could lead to retinal pathology and exacerbate conditions such as age-related macular degeneration.

Aldose reductase deficiency reduced vascular changes in neonatal mouse retina in oxygen-induced retinopathy

PURPOSE

Retinal neovascularization is the major pathologic process in many ocular diseases and is associated with oxidative stress. Deficiency of aldose reductase (AR), the first enzyme in the polyol pathway for glucose metabolism, has been shown to reduce oxidative stress and blood vessel leakage. The present study aimed to investigate the effect of AR deficiency on retinal neovascularization in a murine oxygen-induced retinopathy (OIR) model.

METHODS

Seven-day-old wild-type (WT) and AR-deficient (AR(-/-)) mice were exposed to 75% oxygen for 5 days and then returned to room air. Vascular obliteration, neovascularization, and blood vessel leakage were analyzed and compared. Immunohistochemistry for AR, nitrotyrosine (NT), poly(ADP-ribose) (PAR), glial fibrillary acidic protein (GFAP), and Iba-1, as well as Western blots for vascular endothelial growth factor (VEGF), phospho-Erk (p-Erk), phospho-Akt (p-Akt), and phospho-IκB (p-IκB) were performed.

RESULTS

Compared with WT OIR retinae, AR(-/-) OIR retinae displayed significantly smaller central retinal vaso-obliterated area, less neovascularization, and reduced blood vessel leakage. Significantly reduced oxidative stress and glial responses were also observed in AR(-/-) OIR retinae. Moreover, reduced microglial response in the avascular area but increased microglial responses in the neovascular area were found with AR deficiency. Furthermore, expression levels of VEGF, p-Erk, p-Akt, and p-IκB were significantly reduced in AR(-/-) OIR retinae.

CONCLUSIONS

Our observations indicated that AR deficiency reduced retinal vascular changes in the mouse model of OIR, indicating that AR can be a potential therapeutic target in ischemia-induced retinopathy.

Recruitment of blood-derived inflammatory cells mediated via tumor necrosis factor-α receptor 1b exacerbates choroidal neovascularization

Purpose. Tumor necrosis factor (TNF)-α contributes to inflammation-associated angiogenesis, and TNF-α receptor 1b is selectively expressed on immuno-competent and endothelial cells. This study investigated the role of TNF-α receptor 1b in the recruitment of circulating inflammatory cells and the development of choroidal neovascularization (CNV). Methods. Lethally irradiated Tnfrsf1b(-/-) mice and their wild-type (WT) controls were transplanted with whole adult bone marrow (BM) cells, competent for both TNF-α receptors 1a and 1b (gfp(+) labeled), as well as with BM cells deficient for TNF-α receptor 1b. One month after transplantation CNV was induced by laser damage of Bruch's membrane. Pathologic angiogenesis was estimated qualitatively and quantitatively by histology on choroidal flatmounts and paraffin cross sections. Macrophage invasion was investigated by immunochemistry. Results. One month after transplantation the reconstitution rate measured by FACS analysis was >80% in gfp(+)-chimeric mice. Two weeks after laser injury reduced gfp(+)-cell invasion to the laser scars and decreased pathologic angiogenesis were observed in Tnfrsf1b(-/-) versus WT recipients. Approximately 70% of the invaded gfp(+) cells were labeled with macrophage marker F4/80. Transplantation of TNF-α receptor 1b-deficient BM cells in WT recipients reduced the CNV lesion compared with WT and Tnfrsf1b(-/-) recipients that received TNF-α receptor-competent BM cells. Transplantation of receptor 1b-deficient cells to Tnfrsf1b(-/-) recipients further reduced the degree of CNV formation. Conclusions. Signals through TNF-α receptor 1b expressed on BM -derived inflammatory cells mediate an increased inflammatory cell invasion and enhanced angiogenic response after laser-induced rupture of Bruch's membrane.

Expression of connexin genes in the human retina

BACKGROUND

Gap junction channels allow direct metabolically and electrical coupling between adjacent cells in various mammalian tissues. Each channel is composed of 12 protein subunits, termed connexins (Cx). In the mouse retina, Cx43 could be localized mostly between astroglial cells whereas expression of Cx36, Cx45 and Cx57 genes has been detected in different neuronal subtypes. In the human retina, however, the expression pattern of connexin genes is largely unknown.

METHODS

Northern blot hybridizations, RT-PCR as well as immunofluorescence analyses helped to explore at least partially the expression pattern of the following human connexin genes GJD2 (hCx36), GJC1 (hCx45), GJA9 (hCx59) and GJA10 (hCx62) in the human retina.

RESULTS

Here we report that Northern blot hybridization signals of the orthologuous hCx36 and hCx45 were found in human retinal RNA. Immunofluorescence signals for both connexins could be located in both inner and outer plexiform layer (IPL, OPL). Expression of a third connexin gene denoted as GJA10 (Cx62) was also detected after Northern blot hybridization in the human retina. Interestingly, its gene structure is similar to that of Gja10 (mCx57) being expressed in mouse horizontal cells. RT-PCR analysis suggested that an additional exon of about 25 kb further downstream, coding for 12 amino acid residues, is spliced to the nearly complete reading frame on exon2 of GJA10 (Cx62). Cx59 mRNA, however, with high sequence identity to zebrafish Cx55.5 was only weakly detectable by RT-PCR in cDNA of human retina.

CONCLUSION

In contrast to the neuron-expressed connexin genes Gjd2 coding for mCx36, Gjc1 coding for mCx45 and Gja10 coding for mCx57 in the mouse, a subset of 4 connexin genes, including the unique GJA9 (Cx59) and GJA10 (Cx62), could be detected at least as transcript isoforms in the human retina. First immunofluorescence analyses revealed a staining pattern of hCx36 and hCx45 expression both in the IPL and OPL, partially reminiscent to that in the mouse, although additional post-mortem material is needed to further explore their sublamina-specific distribution. Appropriate antibodies against Cx59 and Cx62 protein will clarify expression of these proteins in future studies.

Conditions of retinal glial and inflammatory cell activation after irradiation in a GFP-chimeric mouse model

PURPOSE

Microglia cells have been associated with immunologic defense and repair. The course of retinal disease after lethal irradiation for bone marrow depletion and substitution was evaluated with respect to macrophage and microglial involvement.

METHODS

Lethal irradiation in C57BL/6 mice was conducted with a low-voltage radiation unit. The animals were randomized to shielded or unshielded radiation and subsequently received transplants of GFP+ bone marrow cells (beta-actin promoter). The GFP transformation rate was analyzed by flow cytometry. GFP+ cells in the retina were examined for co-localization with macrophage and dendritic cell markers at various time points between 1 and 7 months after irradiation. Clodronate liposomes were used to investigate the fate of migrated and residential microglia cells. Pathologic angiogenesis was investigated in laser-induced choroidal neovascularization (CNV) after unshielded and shielded irradiation.

RESULTS

Flow cytometry revealed average transformation rates of 78.2% in unshielded and 64.1% in shielded group. Four weeks after transplantation, perfused flat mounts were virtually free of extravasal GFP+ cells in both groups, whereas 4 months after irradiation, cluster cell infiltrations, preferentially in the peripheral retina, became apparent exclusively in the unshielded group. Cell morphology ranged from oval, to a few extensions, to dendritiform with long-branched extensions. Clodronate treatment resulted in a reduction of GFP+ cells in the retinal tissue when applied 3 months after unshielded irradiation. Although GFP+ cells accumulated in the choroidal scar after laser treatment, in both the shielded and unshielded groups, GFP+ cells in the overlying retina were restricted to the unshielded group.

CONCLUSIONS

Approximately 3 months after lethal full-body irradiation including the eye, bone marrow-derived leukocytes exhibit a wound-healing reaction, and unlike physiological turnover, infiltrate the retina and form microglial cells.

Differential role of tumor necrosis factor (TNF)-alpha receptors in the development of choroidal neovascularization

PURPOSE

Tumor necrosis factor alpha (TNF)-alpha contributes to inflammation-associated angiogenesis. This study investigates the role of TNF-alpha receptors 1a and 1b in the development of choroidal neovascularization (CNV).

METHODS

CNV was induced in Tnfrsf1a(-/-) and Tnfrsf1b(-/-) mice with C57Bl6/J background and their wild-type (WT) (C57Bl/6J) controls by laser damage to the Bruch's membrane. TNF-alpha expression in RPE/choroid was determined by Western blot analysis. Pathologic angiogenesis was estimated qualitatively and quantitatively by fluorescein angiography and histology on choroidal flat mounts and paraffin cross-sections. Inflammatory cell invasion was investigated by clodronic acid depletion of circulating macrophages and immunochemistry, and the apoptotic activity was investigated by TUNEL assay and by caspase-3 and caspase-8 expression. Receptor 1b-specific Bmx/Etk kinase was detected by immunochemistry.

RESULTS

TNF-alpha levels were elevated after laser treatment. Severe CNV lesions and increased macrophage invasion were observed in Tnfrsf1a(-/-) compared with WT and Tnfrsf1b(-/-) mice. Increased immunoreactivity for Bmx/Etk kinase corresponded to the severity of CNV formation. Reduced pathologic angiogenesis and macrophage invasion in Tnfrsf1b(-/-) mice (vs. WT and Tnfrsf1a(-/-)) was accompanied by enhanced endothelial cell apoptosis and by caspase-3 and caspase-8 activation.

CONCLUSIONS

Receptor 1b promotes the recruitment of inflammatory cells to the site of injury and exacerbated pathologic angiogenesis probably by way of the Bmx/Etk-kinase-dependent pathway in the absence of receptor 1a. On the other hand, receptor 1a-dependent apoptosis in the absence of receptor 1b leads to reduced inflammatory response and CNV lesions after laser treatment. This demonstrates the potential for specific targeting of TNF-alpha receptors for future therapies of inflammation-associated choroidal neovascularization.

TNF-alpha mediated apoptosis plays an important role in the development of early diabetic retinopathy and long-term histopathological alterations

PURPOSE

The pathophysiology of diabetic retinopathy involves leukocyte adhesion to retinal vasculature, early blood-retinal barrier breakdown, capillary nonperfusion, and endothelial cell death. We investigated the involvement of tumor necrosis factor alpha (TNF-alpha) in diabetes-related histopathological changes in two relevant rodent models.

METHODS

In short-term studies, Long-Evans rats with streptozotocin-induced diabetes were treated with or without the TNF-alpha inhibitor, etanercept. For long-term studies, tumor necrosis factor receptor I (TNF-RI)-deficient mice and TNF-RII-deficient mice, as well as C57/Bl6 wild-type mice, were fed 30% galactose for up to 20 months. The retinal histopathological alterations of hypergalactosemia were analyzed in trypsin digest preparations. Endothelial cell injury and apoptosis in rat retinas were evaluated by propidium iodide, TUNEL, CytoDeath staining, and DNA fragmentation ELISA. Caspase 3 and 8 activity was evaluated by immunoblotting and quantitative enzymatic activity assay.

RESULTS

Etanercept suppressed caspase activation, retinal cell injury, and apoptosis in short-term diabetic rats. Pericyte and endothelial cell loss were also reduced in long-term hypergalactosemic mice. Long-term studies demonstrated that pericyte loss and endothelial cell loss were reduced in comparison to wild-type diabetic controls.

CONCLUSIONS

Our study identifies an important role for TNF-alpha in the pathogenesis of signature diabetic retinopathy pathologies and demonstrates that etanercept can inhibit retinal cell death and long-term complication of diabetes. Taken together, our results suggest that etanercept could prove beneficial in preventing both early and late vascular diabetic complications.

Modulation of Hypoxia-Induced Neovascularization by JSM6427, an Integrin α5β 1 Inhibiting Molecule

PURPOSE

Integrin alpha5beta1, a fibronectin receptor, is involved in endothelial cell migration and proliferation. Here we investigate the effect of JSM6427, an integrin alpha5beta1 inhibiting molecule, on the development of retinal vascular system using the mouse model of oxygen-induced retinopathy (OIR).

METHODS

Endothelial cell migration and sprouting was analyzed in vitro using a 2D migration assay and a 3D sprouting/angiogenesis assay in fibrin gel. C57BL/C6 mice were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and returned to room air thereafter. Intravitreal injection of 40 microg JSM6427 was performed in each one eye on P14. On P17, vascular area, avascularized area, and neovascular blood vessel tufts were quantified after perfusion with fluorescein-coupled concanavalin A. The number of retinal neovascular cell nuclei was determined in hematoxylin-stained cross sections of the eyes. Integrin alpha 5 expression was determined by immunohistochemistry.

RESULTS

In vitro, JSM6427 inhibits the migration of HUVEC and the tube formation induced by both bFGF and VEGF. In vivo, integrin alpha 5 expression was detectable in neovascular retinal blood vessels. Oxygen treatment (positive control) in comparison with no oxygen treatment (negative control) reduced significantly the vascularized area and increased the avascularized area. A single intravitreal injection of 40 microg JSM6427 resulted in a significant reduction of the vascularized area and the number of preretinal nuclei in comparison with the intravitreal injection of the vehicle while the avascularized area increased significantly.

CONCLUSIONS

These results imply an essential role of integrin alpha5beta1 in the refining of the retinal vasculature in OIR and suggest JSM6427 may have a possible therapeutic function for neovascular disease.

ICAM-1 depletion does not alter retinal vascular development in a model of oxygen-mediated neovascularization

ICAM-1 has been identified as a mediator of inflammatory and VEGF-dependent corneal neovascularization. Furthermore, ICAM-1 has been demonstrated to be involved in leukocyte-mediated endothelial injury in diabetic retinopathy. Here we investigated the role of ICAM-1 in retinal vaso-obliteration and vascularization. ICAM-1 deficient mice as well as their respective wild-type controls were exposed to 75% oxygen from postnatal day 7 to day 12. Retinal vascularization was investigated after lectin labeling of endothelial cells on day 14, 17, and 20 in flat mount preparations. Retinal mRNA expression of VEGF, Angiopoietin 1 and 2 as well as PDGFbeta was examined at day 14 and 20 by Real Time RT-PCR. ICAM-1(-/-) mice and their respective wild-type controls demonstrated similar retinal development and vascularization under normoxic conditions. Similarly, after oxygen challenge, the vascular area, the avascularized area as well as the area of neovascular tufts did not differ between ICAM-1(-/-) and the respective wild-type mice although the mRNA expression of VEGF, ang-1, ang-2, and PDGFbeta differed clearly. This study demonstrates that lack of ICAM-1 leads to an altered expression of angiogenic factors that in combination may neutralize each other and do not alter retinal development and angiogenesis in oxygen-induced retinopathy.

Hepatocyte expression of angiotensin II type 1 receptor is downregulated in advanced human liver fibrosis

BACKGROUND

The renin-angiotensin system plays an important role in fibrosis. Angiotensin II regulates key steps in tissue remodelling processes through angiotensin II type 1 receptor (AT1R). In bile duct-occluded rats, AT1R expression is significantly decreased in advanced liver fibrosis. Therefore, we studied the AT1R expression in human liver tissue during different stages of fibrosis caused by chronic hepatitis C.

METHODS

Liver biopsy specimens from 85 patients were analysed. Real-time reverse transcription polymerase chain reaction was used to quantify AT1R mRNA. Immunohistochemical labelling of AT1R and double staining for AT1R, CD31, CD68, CD3 and fibulin-2 were performed.

RESULTS

AT1R mRNA was significantly reduced in human liver tissue with end-stage cirrhosis compared with early fibrosis. In liver cirrhosis, immunohistochemistry revealed a decreased expression of AT1R on hepatocytes, together with an increased staining intensity on myofibroblasts, vascular endothelium and bile duct epithelium.

CONCLUSION

In conclusion, AT1R expression is downregulated in human liver cirrhosis specimens because of the reduced expression levels on hepatocytes. Therefore, antifibrogenic therapy with AT1R blockers may be most promising if initiated during early stages of fibrosis.

A cleaning solution for silicone intraocular lenses: "sticky silicone oil"

AIM

The aim of the study was to compare the efficacy of perfluorobutylpentane (F4H5) and perfluorohexyloctane (F6H8) in dissolving silicone oil from the surface of silicone intraocular lenses (IOL).

METHODS

Droplets of stained silicone oil were applied to an object slide either lying flat or tilted by 30 degrees . Mixing with H(2)O, F4H5 or F6H8 was documented by a digital camera. Droplets of silicone oil were applied to silicone lenses and washed off by repeated rinsing with F4H5 or F6H8. The silicone lenses of 11 patients with silicone oil remnants on the posterior IOL surface were rinsed intraoperatively with F4H5 during removal surgery.

RESULTS

Only F4H5 was able to mix with silicone oil and to remove it form the surface of a glass object slides. Rinsing with 25 mul F4H5 reduced the amount of silicone oil 1000 mPas or 5000 mPas attached on a silicone lens to 15% and 28%, respectively. A hanging droplet of silicone oil 5000 beneath a silicone lens was completely removed from below by F4H5. In all patients sufficient IOL cleaning was possible using F4H5. There was no significant postoperative inflammation in the vitreous or anterior chamber.

CONCLUSION

Polydimethylsiloxanes dissolve effectively in F4H5 due to its lipophilic chemical structure. A much smaller volume of F4H5 than F6H8 is able to remove silicone oil from silicone lenses completely. Intraocular use of F4H5 is safe, and initial clinical data underlines its effectiveness as a cleaning agent after contact of silicone lenses with silicone oil.

[Effect of anti-TNF-alpha on laser-induced choroidal neovascularization]

OBJECTIVE

To investigate the role of TNF-alpha in the development of laser-induced choroidal neovascularization (CNV) in the mouse.

METHODS

Laser photocoagulation was used to induce CNV in wild-type C57BL/6J mice by making four separate choroidal bums in each eye. Animals were treated 3 days before or after laser injury with recombinant TNF receptor P75 (etanercept, 5 microg/h, group 1, n = 12), chimeric monoclonal antibody (infliximab, 5 microg/h, group 2, n = 12) for 7 days by intraperitoneally implanted osmotic pumps. PBS was used as control (group 3, n = 12). The left eyes were removed for histopathologic examination and the right eyes were removed for flatmounts immunohistochemistry immediately after fluorescein angiography. In mice treated with medications 3 days before laser injury, left eyes were collected at 1 or 2 weeks after laser injury. In mice treated with medications 3 days after laser injury, left eyes were collected at 10 days after laser injury. CNV responses were compared by flatmount analysis of CNV-related fluorescence area and by determination of fluorescein angiographic leakage. The level of protein expression of TNF-alpha was semiquantitatively evaluated by Western blot analysis of the choroidal and RPE layer from mice with or without laser treatment.

RESULTS

Western blotting demonstrated that TNF-alpha was highly expressed in choroidal and RPE cells of wild type mice 1 week after laser treatment as compared to the control mice without laser treatment. Etanercept and infliximab administrated 3 days before laser-damage significantly reduced CNV size and pathological fluorescein leakage in comparison to the control group one and two weeks after laser injury. Only etanercept administered 3 days after laser injury still significantly reduced the development of CNV lesions. Histopathological examination confirmed that CNV lesions in treated mice had smaller diameter and thinner center as compared to the control animals.

CONCLUSIONS

Anti-TNF-alpha treatment reduces the size and leakage of laser-induced CNV. These results suggest the involvement of TNF-alpha in the development of laser-induced CNV and its potential use as a therapeutic agent in the age related macular degeneration.

Pneumatic retinopexy by evaporation of fluorocarbon liquids: in vitro and in vivo results

PURPOSE

To develop an expanding gas tamponade allowing a controlled and complete filling of the vitreous cavity in the non-vitrectomized eye.

METHODS

Twenty-two different liquid fluorocarbon mixtures with a high vapour pressure were tested in an in vitro eye model and in rabbit eyes. The intraocular pressure (IOP), the anterior segment of the eye, the vitreous and the retina were inspected at each examination during a period of 2 weeks. The timepoint of maximal gas expansion and the period required for complete absorption of the gas bubble were recorded.

RESULTS

In vitro, admixtures of perfluorocarbons (PFCLs) and of semifluorinated alkanes (SFAs) with ether/alkanes generated limited temporary gas expansion but increased IOP. Admixtures of n-pentane in paraffin oil or silicone oil resulted in incomplete gas filling remaining for several days, with moderate IOP. In vivo, different clinical features and gas expansion were observed after the injection of PFCLs saturated with CO(2) or SF(6). Normal IOP was noted, but only with a transient and incomplete gas expansion and tamponade. For example, with n-pentane/n-hexane/perfluoromethylcyclopentane/perfluoromethyl-cyclohexane (1:1:1:1) a very rapid gas expansion was observed, followed by a raised IOP, a shallow anterior chamber, and finally rupture of the globe. The correlation between the in vitro and in vivo data was low.

CONCLUSIONS

Gas endotamponade based on evaporation of liquid fluorocarbons is possible, but a complete and reliable tamponade could not be achieved. The best results were demonstrated by admixtures with an overall density <1.00 g/cm(3), an inert carrier with high vapour pressure, and a highly volatile substance. Further detailed investigation into the factors influencing evaporation is required.

Expression of angiotensin II receptor type 1 is reduced in advanced rat liver fibrosis

In this study, we assessed the hypothesis that the expression of angiotensin II receptor type 1 (AGTR1) in liver tissue changes with increasing fibrosis, which would influence the antifibrotic efficacy of AGTR1 blockers. Rats were treated with candesartancilexetil (CAN) initiated 8 or 15 days after bile duct occlusion (BDO). Four weeks after BDO, AGTR1 mRNA and protein were decreased compared to those in sham-operated animals depending on the amount of fibrosis. Starting CAN early, but not late, reduced mRNA of profibrotic TGF-beta, MMP2, and Smad2. However, CAN had no significant effect on collagen I, fibrosis, or intrahepatic resistance. In conclusion, progression of liver fibrosis reduces AGTR1 expression. Therefore, in our model, antifibrotic effects of CAN are insufficient to improve fibrosis or intrahepatic resistance. However, if AGTR1 blockade is started early, a decrease in essential profibrotic molecules is achieved. Hence, early initiation of therapy with AGTR1 blockers may be crucial for the prevention of cirrhosis.

The role of integrin alpha5beta1 in the regulation of corneal neovascularization

Integrins are transmembrane receptor proteins critical for growth and stabilization of vessels, but the mechanisms by which integrin activities are involved in neoangiogenesis of the eye remain unclear. Specific inhibitors to fibronectin receptor integrin alpha(5)beta(1) impeded pathological neovascularization in vivo. Our objective was to determine whether alpha(5)beta(1) plays a role in ocular angiogenesis, and whether a novel alpha(5)beta(1)-inhibiting small molecule is able to reduce angiogenesis in a model of inflammatory corneal neovascularization. Corneal neovascularization was induced in C57Bl/6 mice by NaOH-application and debridement of the limbal epithelium. Mice were randomized into six groups receiving either no treatment, or intraperitoneal osmotic pumps delivering three different doses of integrin antagonist or control substance on day 10 after scraping. In order to quantify the neovascular response, flatmounts were stained with FITC-CD31. Integrin alpha(5) expression was determined by immunohistochemistry and quantified by semiquantitative western blot analysis. Influence of integrin antagonist treatment on the mRNA expression of VEGF, bFGF and integrin alpha(5) was quantified by real-time RT-PCR. Vascularized corneas demonstrated a strong up-regulation of integrin alpha(5) within affected areas. Animals treated systemically with alpha(5)beta(1)-inhibiting small molecule showed a significant inhibition and regression of corneal neovascularization. PCR analysis evinced a significant up-regulation of VEGF and integrin alpha(5) mRNA levels in injured animals compared to controls, and a significant reduction of integrin alpha(5) mRNA in substance-treated animals compared to control substance, but no significant differences of bFGF levels in all groups. Western blot analysis of integrin alpha(5)beta(1) protein expression showed a trend towards up-regulation in injured animals, both control substance-treated and those treated with the alpha(5)beta(1)-inhibiting small molecule. Systemic delivery of an alpha(5)beta(1)-inhibiting small molecule inhibits and regresses corneal neovascularization induced by mechanical-alkali burn corneal injury. These results suggest an essential role for the integrin alpha(5)beta(1) in pathological neovascular processes of the cornea. Integrin alpha(5)beta(1) inhibitors could become a new approach for treatment of neovascularization in the eye.

In Vivo Retinal Tolerance of Various Heavy Silicone Oils

PURPOSE

Heavy silicone oils are currently under investigation as a permanent tamponade in eyes with inferior PVR. This study was an investigation of Densiron 68 (Fluoron GmbH, Neu-Ulm, Germany) and several new heavy silicone oil admixtures on the basis of the perfluoroalkanes F4H5 (perfluorobutylpentane), F4H6 (perfluorobutylhexane), and F4H8 (perfluorobutyloctane) with respect to their long-term tolerance in a rabbit model.

METHODS

Because of the better solubility of the F4Hn-species (n = 5-8) in comparison to F6H8, we used F4H5, F4H6, and F4H8 to generate highly viscous, heavy silicone oils (HSO). After vitrectomy and fluid-air exchange, the left eye of each of five rabbits per group was filled with HSO 68-1500 (Densiron 68), HSO 45-5000, HSO 45-3000, HSO 46-5000, HSO 46-3000, HSO 48-5000, or HSO 48-3000, or pure F4H5, F4H6, or F4H8. Detailed clinical investigation, ERG testing, and histologic evaluation were performed throughout a 3-month follow-up.

RESULTS

Densiron 68 and HSOs based on F4H5, as well as the three control oils (silicone oil of 1000, 3000, and 5000 mPa . s) were well tolerated over 3 months. Histologically, the retina was unaffected. In contrast, intraocular inflammation, cataract formation, and retinal detachment and degeneration were noticed in all groups with HSOs based on F4H6 or F4H8.

CONCLUSIONS

Biocompatibility of the new HSOs is dependent on the lipophilic behavior (R(F)/R(H) ratio) and furthermore on the molecular dimension of the used semifluorinated alkanes (SFAs). HSOs on the basis of F4H5 may have advantages over silicone oils, on the basis of F6H8, for use as a tamponade agent for the inferior retina in difficult retinal situations.

Tyrosinase biosynthesis and trafficking in adult human retinal pigment epithelial cells

BACKGROUND

Tyrosinase (EC 1.14.18.1) is the key enzyme of melanin pigment formation and it is unclear whether it is synthesized in human postnatal retinal pigment epithelium (RPE). In this study, we investigated if phagocytosis of rod outer segments (ROS) can increase tyrosinase expression in vitro.

METHODS

Primary cultures of human RPE cells were fed with isolated ROS from cattle and with latex particles. After phagocytosis, RPE cells were tested for tyrosinase presence and activity with several independent methods: (1) immunocytochemistry with anti-tyrosinase antibodies and (2) ultrastructural as well as light microscopic DOPA histochemistry; (3) mRNA was isolated from human RPE before incubation with ROS and 5, 20 and 40 h after feeding with ROS. The amount of tyrosinase mRNA was determined quantitatively by real-time reverse transcription polymerase chain reaction (RT-PCR), and the tyrosinase activity was investigated by measuring tyrosine hydroxylase activity using [(3)H]tyrosine.

RESULTS

Tyrosinase was found in fed RPE cells using these methods, but was absent without feeding. Furthermore, we showed co-localization of rhodopsin and tyrosinase in the fed RPE cells. Contrary to tyrosinase activity, the mRNA for tyrosinase was clearly present in the cultured RPE cells which had not been exposed to ROS, decreased significantly from 5 h after exposure to ROS and returned to its original non-fed level 40 h after ROS feeding.

CONCLUSION

Our study does not present new evidence that de novo melanogenesis takes place in the adult differentiated RPE. However, in contrast to the classic hypothesis, which states that tyrosinase is only detected in embryos, we provide evidence with several independent methods that the expression of tyrosinase and its enzymatic activity are induced in cultured human adult RPE by phagocytosis of ROS.

Pathological but not physiological retinal neovascularization is altered in TNF-Rp55-receptor-deficient mice

PURPOSE

Tumor necrosis factor (TNF)-alpha is one of the major cytokines in inflammation and apoptosis. It has been demonstrated that inhibition of TNFalpha can reduce leukocyte adhesion, vascular leakage, and apoptotic endothelial cell death in diabetes. This study was conducted to investigate the effect of TNF-Rp55 and TNF-Rp75 on retinal development in oxygen-induced retinopathy.

METHODS

TNF-Rp55- and TNF-Rp75-deficient mice, as well as their respective wild-type controls, were exposed to 75% oxygen from postnatal day P7 to P12. Retinal vascularization was investigated in flatmount preparations after concanavalin A labeling of endothelial cells on days P6, P14, P17, and P20. Retinal mRNA expression of VEGF, angiopoietin-1 and -2, and PDGF was examined at days P14 and P20.

RESULTS

TNF-Rp55- and TNF-Rp75-deficient mice demonstrated similar retinal development and vascularization under normoxic conditions. In comparison to wild-type mice, the vascularized area remained stable during the observation time, although the gene expression of VEGF, angiopoietin (ang)-1 and -2, and PDGFb changed. Compared with that in the wild type mice, the relative expression of VEGF, ang-1, ang-2, and PDGFb changed 5.14-, 1.7-, 0.39-, and 0.36-fold in Rp55(-/-) mice and 4.1-, 9.5 x 10(-5)-, 0.12-, and 2975-fold in Rp75(-/-) mice, respectively. Treatment with oxygen resulted in a significantly reduced vascularization in Rp55(-/-) but not Rp75(-/-) mice on postnatal day (P)20.

CONCLUSIONS

Inhibition of TNFalpha via TNF-Rp55 can alter retinal development and angiogenesis in a model of oxygen-induced retinopathy. The data underscore the potential effectiveness of TNF-inhibitory treatments as modulators in oxygen-induced retinopathy.

Effect of gravity in long-term vitreous tamponade: in vivo investigation using perfluorocarbon liquids and semi-fluorinated alkanes

PURPOSE

In order to investigate whether gravity is the reason for retinal degeneration in long-term vitreous tamponade, perfluorohexyloctane (F6H8), perfluorodecalin (PFD), and a mixture of F6H8/PFD were compared.

MATERIALS AND METHODS

Each group of 5 rabbits received a 3-month tamponade with either PFD (pure) (1.93 g/cm(3)), F6H8 (pure) (1.33 g/cm(3)), or a 1:1 mixture of F6H8/PFD (1.62 g/cm(3)). Electroretinograms (ERG) were performed pre- and postoperatively. Lower and upper retinal areas were compared using immunohistochemical methods. Transmission electron microscopy was performed to investigate alterations in the photoreceptors.

RESULTS

All three substances were tolerated well in rabbit eyes for up to 3 months. Dispersion was seen earliest with PFD and latest with pure F6H8. None of the substances demonstrated inflammatory reactions or vascular alterations. ERGs were not considerably altered with any of the substances. Histology of the retina showed alterations in the cell counts within the inner and outer nuclear layer that were not attributable to the gravity of the tamponading agent.

CONCLUSION

In contrast to previously published work, this study did not detect any tamponade-related structural damage of the retina after a 3-months tamponade in the rabbit model. Based upon this study, we conclude that gravity might not be causally linked to retinal damage.