Martina Theresa Kralinger

Plasma levels of vascular endothelial growth factor before and after intravitreal injection of bevacizumab, ranibizumab and pegaptanib in patients with age-related macular degeneration, and in patients with diabetic macular oedema.

Aims To determine the level of vascular endothelial growth factor (VEGF) in the plasma of patients with diabetic macular edema (DME) and of patients with exudative age-related macular degeneration (ARMD) before and after intravitreal injection of bevacizumab, ranibizumab or pegaptanib. Methods 30 patients with DME and 30 patients with ARMD were included in this randomized controlled study. Patients were randomized to treatment with ranibizumab (0.5 mg), bevacizumab (1.25 mg) or pegaptanib (0.3 mg). 10 patients with DME received bevacizumab, 10 ranibizumab and 10 pegaptanib. The same randomized treatment allocation applied to the 30 patients with ARMD. The concentrations of VEGF were measured by ELISA just before the injection, after 7 days and 1 month. Results Plasma VEGF in patients with exudative ARMD before the injection of bevacizumab was 89.7 pg/ml. It was significantly reduced to 25.1 pg/ml after 7 days (p=0.01), and to 22.8 pg/ml after 1 month (p=0.008). In patients with DME the same systemic reduction by bevacizumab was observed with a significant decrease of baseline VEGF level from 72.2 pg/ml to 13.7 pg/ml after 7 days (p=0.008) and 17.1 pg/ml at 4 weeks with (p=0.012). No significant reductions of plasma VEGF levels were observed in patients receiving ranibizumab or pegaptanib during follow-up. Conclusions Bevacizumab significantly reduces the level of VEGF in the blood plasma for up to one month in patients with DME as well as in those with ARMD. No significant systemic effects of intravitreal ranibizumab or pegaptanib on plasma VEGF could be observed.

Systemic levels of vascular endothelial growth factor before and after intravitreal injection of aflibercept or ranibizumab in patients with age‐related macular degeneration: a randomised, prospective trial

To evaluate the changes of vascular endothelial growth factor (VEGF) plasma levels after intravitreal injections of aflibercept or ranibizumab in patients with exudative age‐related macular degeneration (AMD).

Long-Term Outcome after Vitrectomy for Diabetic Macular Edema

Background: To determine the benefit of vitrectomy on eyes with diabetic macular edema. Methods: A retrospective institutional case series was used including 66 patients (69 eyes) who had undergone pars plana vitrectomy for diabetic macular edema between 1992 and 2000. Prior to surgery, the patients had been treated with laser coagulation as recommended by the Early Treatment Diabetic Retinopathy Study. In the case of persistent macular edema, vitrectomy with removal of the posterior hyaloid in all cases and the inner limiting mem brane in 51 (74%) of all cases was performed. Results: The mean preoperative best-corrected visual acuity improved from 20/320 to 20/80 at the time of best postoperative best-corrected visual acuity (p < 0.0001). The mean increase in Snellen lines was 2.7 ± 7.9. In 90% of eyes, the macular edema improved. A persistence of the edema was observed in 10%. All eyes had at least 12 months of follow-up with a mean of 55 months and a maximum of 120 months. Conclusions: Our findings confirm that vitrectomy might represent a therapeutic alternative in the case of persisting diabetic macular edema after laser photocoagulation.

Correlation of vascular endothelial growth factor plasma levels and glycemic control in patients with diabetic retinopathy

Purpose:  To determine whether glycemic control of patients with diabetic retinopathy (DR) due to type 2 diabetes was related to VEGF plasma levels.

Inhibitory effect of certain neuropeptides on the proliferation of human retinal pigment epithelial cells

Aims: To define the effect of the neuropeptides substance P, calcitonin gene related peptide, vasoactive intestinal polypeptide, neuropeptide Y, and secretoneurin on the proliferation of human retinal pigment epithelial (RPE) cells. Methods: ARPE-19 cells were used. The cells were cultured in Dulbecco’s modified Eagle’s medium. 1000 and 2000 cells were incubated with the peptides for 3 and 5 days, and the effect of the peptides was evaluated by an ATP lite assay dose dependently. Furthermore, specific antagonists at 10−6 M were used to find out whether the effect would be reversed. Results: In brief, each of the peptides tested had an inhibiting effect. This inhibiting effect was weak but highly significant, averaging 10% to 15%, and was most pronouncedly seen at concentrations between 10−10 M and 10−14 M. Each antagonist reversed the inhibiting effect fully. Conclusions: These results clearly indicate that RPE cells are under neural control and the low effective concentration of the peptides may be the one physiologically acting on these cells. The results are of important relevance both physiologically and pathophysiologically: physiologically, the inhibitory effect may mean that these peptides cause the cells to remain in a differentiated condition. Pathophysiologically, the findings are relevant in proliferative vitreoretinopathy where RPE cells proliferate in excess. The authors hypothesise that the inhibiting effect diminishes when these cells are swept out and actively migrate from their physiological location and thus, dedifferentiate and begin to proliferate. This hypothesis improves the knowledge of the initial processes in the pathogenesis of the disease as there seems to be a discrepancy between facilitatory and inhibitory influences favouring the former in proliferative vitreoretinopathy. Furthermore, these neuropeptides constitute the first endogenous inhibitors of RPE cell proliferation.

Experimental Model for Proliferative Vitreoretinopathy by Intravitreal Dispase: Limited by Zonulolysis and Cataract

Background: The intravitreal injection of dispase has been shown to be a valuable method for induction of experimental PVR. The goal of the present study was to gain additional information about potential side effects associated with this method. Methods: Twenty-one pigmented rabbits received a single injection of dispase under topical anesthesia to one eye only, contralateral eyes served as untreated control. The animals were injected with doses from 0.045 to 0.065 units of dispase: 8 animals received 0.045 units, 9 animals 0.055 units and 4 animals 0.065 units. Results: Proliferative vitreoretinopathy occurred in 81% of the treated eyes. In 90% cataract formation was observed. Lens luxation was present in 47.3% of the cataract eyes. Conclusion: Intravitreal injection of dispase resulted in the reproducible induction of PVR in addition to cataract formation and lens luxation. Whether these effects may all be associated with a toxic reaction or whether the proliferative changes are solely triggered by endogenous reactions similar to the pathomechanism of human PVR and whether the cataract formation and the lens luxation may be avoided by changing the method of injection require further investigation.

VIP, PACAP-38, BDNF and ADNP in NMDA-induced excitotoxicity in the rat retina

Purpose: To evaluate the effect of intravitreal injection of N‐methyl‐D‐aspartate (NMDA) on brain‐derived neurotrophic factor (BDNF), pituitary adenylate cyclase‐activating peptide‐38 (PACAP‐38), vasoactive intestinal peptide (VIP) and the VIP‐associated glial protein activity‐dependent neuroprotective protein (ADNP) in the rat retina. These elements have well‐documented neuroprotective properties and may thus be integrated in endogenous neuroprotective mechanisms in the retina which break down in NMDA excitotoxicity.

Systemic counterregulatory response of placental growth factor levels to intravitreal aflibercept therapy.

PURPOSE Placental growth factor (PlGF) has been implicated as a contributor to resistance against anti-VEGF therapy. The purpose of the present study was to analyze the systemic levels of PlGF, VEGF-A, and VEGF-B in patients with neovascular age-related macular degeneration (AMD) after treatment with aflibercept, ranibizumab, or bevacizumab. METHODS Totals of 19 patients were treated with intravitreal aflibercept, 19 with ranibizumab, and 18 with bevacizumab. The cytokine levels were measured by ELISA just before the injection, and 7 days and 1 month thereafter. Age- and sex-matched participants (n = 22) served as controls. RESULTS The median PlGF plasma concentration at baseline was <12.0 pg/mL in the control group as well as in all three anti-VEGF treatment cohorts. After intravitreal aflibercept injection, a significant upregulation of systemic PlGF could be observed in all treated patients (38.0 [31.0-44.0] pg/mL after 1 week [P < 0.001] and 16.0 [0.0-19.0] pg/mL [P = 0.005] after 4 weeks). No significant effects on plasma PlGF concentrations could be detected in those treated with ranibizumab and bevacizumab. The systemic VEGF-A levels were significantly reduced 1 and 4 weeks after intravitreal aflibercept (P < 0.001, P < 0.001) and bevacizumab (P < 0.001, P < 0.01) injections. No significant effects on plasma cytokine concentrations could be observed in the ranibizumab cohort. No significant effects on systemic VEGF-B could be observed in any of the treatment groups. CONCLUSIONS In this study, we report a significant systemic upregulation of the proangiogenic cytokine PlGF after intravitreal administration of aflibercept. This might represent a counter-regulatory response to antiangiogenic therapy.

Systemic Upregulation of PDGF-B in Patients With Neovascular AMD

PURPOSE To determine the plasma levels of platelet-derived growth factor-B (PDGF-B), VEGF, and TNF-α in patients with neovascular AMD and in patients with diabetic macular edema (DME). METHODS Thirty patients with neovascular AMD, 30 patients with DME, and 12 healthy controls were included in this prospective study. The concentrations of PDGF-B, VEGF, and TNF-α were measured by ELISA. RESULTS The PDGF-B concentration in the plasma of controls was (median [25th-75th percentile]) 263.5 (162.0-513.3) pg/mL and in patients with DME 219.0 (122.8-604.8) pg/mL. In patients with neovascular AMD, PDGF-B levels were significantly higher with a median plasma concentration of 783.5 (289.3-1183.5) pg/mL (P = 0.003). The VEGF concentrations in patients with DME 33.0 (21.8-73.0) pg/mL and in patients with neovascular AMD 55.0 (37.0-116.3) pg/mL showed no significant differences (P = 0.159). A positive correlation of PDGF-B and VEGF plasma levels was found in patients with neovascular AMD and in patients with DME (r = 0.683, P < 0.001, and r = 0.612, P < 0.001, respectively). No significant differences of systemic TNF-α levels could be found between the three study groups. CONCLUSIONS Patients with neovascular AMD have significantly higher plasma PDGF-B levels compared with patients with DME and healthy controls. Our study data indicate that PDGF-B may be involved in the pathogenesis of neovascular AMD. (https://eudract.ema.europa.eu number, EudraCT 2010-024654-11)

Neurokinin A and neurokinin B in the human retina

Very recently, the authors found levels of neurokinin (NK) A-like immunoreactivities in the human retina which were more than five times higher than those of substance P (SP). The present study aimed to find out how many of these immunoreactivities can be attributed to NKA and NKB and then the exact distribution pattern of both NKA and NKB was evaluated in the human retina and compared with that of SP. For this purpose, NKA-like immunoreactivities were characterized in the human retina by reversed phase HPLC followed by radioimmunoassay using the K12 antibody which recognizes both NKA and NKB. Furthermore, the retinae from both a 22- and 70-year-old donor were processed for double-immunofluorescence NKA/SP and NKB/SP. The results showed that NKA contributes to approximately two thirds and NKB to approximately one third of the immunoreactivities measured with the K12 antibody. NKA was found to be localized in sparse amacrine cells in the proximal inner nuclear layer, in displaced amacrine cells in the ganglion cell layer with processes ramifying in stratum 3 of the inner plexiform layer and also in sparse ganglion cells. By contrast, staining for NKB was only observed in ganglion cells and in the nerve fiber layer. Double-immunofluorescence revealed cellular colocalization of NKA with SP and also of NKB with SP. Thus, the levels of NKA and NKB are more than three and two times higher than those of SP, respectively. Whereas the distribution pattern of NKA is typical for neuropeptides, the localization of NKB exclusively in ganglion cells is atypical and unique.