MD Research News – Issue 422 – 16 May 2019

Drug treatment

Graefes Arch Clin Exp Ophthalmol. 2019 May 3.

Long-term effect of intravitreal ranibizumab therapy on retinal nerve fiber layer in eyes with exudative age-related macular degeneration.

Valverde-Megías A, Ruiz-Calvo A, Murciano-Cespedosa A, Hernández-Ruiz S, Martínez-de-la-Casa JM, García-Feijoo J.

Purpose: To investigate long-term effect (96 months) of intravitreal ranibizumab administered for exudative age-related macular degeneration (AMD) on retinal nerve fiber layer (RNFL) thickness when used following a pro re nata regimen.

Methods: In this prospective study, 20 eyes of 20 patients diagnosed with exudative AMD were included. Contralateral non-exudative AMD eyes of nine of these patients were included as controls. Data on intraocular pressure (IOP) and number of injections were recorded. Spectralis optic coherence tomography (OCT) of the circumpapillary RNFL was performed under dilation when diagnosis was made and before the three loading injections. "Follow-up" software was selected to accurately compare baseline with subsequent images through the 8 years of the study.

Results: Baseline IOP was 14.1 mmHg both in study (standard deviation, SD: 0.8) and control eyes (SD: 0.9) and remained unchanged during the study. Mean number of injections was 21 (SD: 2.8) at the end of the study. Mean average thickness of RNFL in the study eye group at the end of the study was 96.5 μm (SD: 2.1). Mean loss for the study period was 5.3 μm (SD: 0.7; p < 0.0001). Corresponding RNFL values for controls were 92.9 (SD: 3.2) and 5.8 μm (SD: 1.2; p < 0.001). Superior temporal sector had the greatest loss in both groups, followed by inferior and nasal sectors. No statistically significant differences were found when comparing losses in injected eyes versus control eyes.

Conclusion: RNFL thickness decreased both equally in injected eyes and control eyes. Thus, no long-term effects of intravitreal ranibizumab were observed on the retinal nerve fiber layer thickness.

PMID: 31053943 DOI: 10.1007/s00417-019-04325-y

 

Int Ophthalmol. 2019 May 8. doi: 10.1007/s10792-019-01116-6. [Epub ahead of print]

Long-term changes in retinal layers in patients undergoing intravitreal ranibizumab for neovascular age-related macular degeneration: Retinal layers after anti-VEGF therapy.

Inan ÜÜ1,, Baysal Z, Inan S.

Purpose: To analyze long-term changes in individual retinal layers (RLs) after intravitreal injections of ranibizumab (IVRs) in patients with neovascular age-related macular degeneration (n-AMD).

Methods: The patients were treated with 0.5-mg IVRs based on an as-needed protocol after the first three monthly doses over a 12-month follow-up period. Patients underwent optical coherence tomography and best-corrected visual acuity (BCVA) evaluation at each visit. The ETDRS grid with central subfield (R1) (r 0.5 mm) and the inner ring (R2) (r 0.5-1.5 mm) was used for calculation of the mean thickness of each RL. Changes in the thickness of segmented RLs within the R1 and R2 of ETDRS circles at months-3, -6, and -12 were compared to baseline.

Results: The mean age was 72 ± 7.4 years. The mean number of injections was 9.08 (range 6-11). Mean BCVA improved from 49.7 ± 22.1 to 60.1 ± 19.8 letters. Central macular thickness decreased from 390.25 ± 149.6 to 312.74 ± 118.4 μm. Thicknesses of GCL (from 23.93 ± 13.73 to 19.50 ± 9.50 μm in R1; p 0.001, and from 44.5 ± 12.6 to 39.6 ± 10.6 μm in R2; p 0.005), IPL (from 28.90 ± 14.36 to 22.35 ± 6.23 μm in R1; p 0.001, and from 39.34 ± 8.53 to 35.58 ± 7.93 μm in R2; p 0.004), and total inner RL (ILM to ELM) (from 222.93 ± 93.09 to 180 ± 53 μm in R1; p 0.001, and from 255.06 ± 42.74 to 240.25 ± 40.37 μm in R2; p 0.003) in the central and parafoveal rings decreased statistically at month-12. Decrease in INL was limited to month-6 (from 34.80 ± 15.33 to 27.60 ± 12.59 μm in R1; p 0.001), while decreases in total outer RLs (ELM to RPE) (from 128.32 ± 26.92 to 115.54 ± 43.98 μm in R1; p 0.001, and 103.81 ± 16.73 to 96.38 ± 16.22 μm in R2; p 0.014) and RPE (from 39.12 ± 22.33 to 29.70 ± 22.05 μm in R1; p 0.001, and from 31.27 ± 13.11 to 24.40 ± 9.99 μm in R2; p 0.001) were limited to month-3.

Conclusions: Significant changes were observed in the thickness of the inner RLs after 1-year treatment with IVRs for n-AMD. A significant decrease in RPE thickness confined to the first months disappeared at month-12.

PMID: 31069616 DOI: 10.1007/s10792-019-01116-6

 

Imaging

Ophthalmol Retina. 2019 Mar 21. pii: S2468-6530(18)30645-6.

Detection of nonexudative choroidal neovascularization and progression to exudative choroidal neovascularization using OCT angiography.

Bailey ST, Thaware O, Wang J, Hagag AM, Zhang X, Flaxel CJ, Lauer AK, Hwang TS, Lin P, Huang D, Jia Y.

Purpose: To detect nonexudative choroidal neovascularization (CNV) in age-related macular degeneration (AMD) with OCT angiography (OCTA) and determine the risk of exudative CNV developing compared with eyes without nonexudative CNV.

Design: Prospective, longitudinal, observational study.

Participants: Consecutive patients with drusen and pigmentary changes in the study eye and exudative neovascular AMD in the fellow eye.

Methods: In this prospective observational study, participants underwent spectral-domain OCTA (AngioVue; Optovue, Inc, Fremont, CA), clinical examination, and structural OCT at baseline and 6-month intervals for 2 years. OCT angiography images were exported for custom processing to remove projection artifact and calculate CNV vessel area.

Main Outcome Measures: Rate of developing exudation in eyes with and without nonexudative CNV as detected by OCTA on regular follow-up.

Results: Sixty-three study participants were followed up every 6 months and 48 completed the 2-year study. Mean age was 78 years and 60.3% were female. On the baseline visit, 5 eyes (7.9%) were found to have nonexudative CNV by OCTA, and 3 of them demonstrated exudation. Of 58 eyes with a normal OCTA on baseline visit, 5 eyes developed nonexudative CNV during a follow-up visit. All 5 of these nonexudative CNV went on to develop exudation in subsequent visits. Overall, 8 of the 10 eyes with nonexudative CNV developed exudation with a mean time of 8 months and mean CNV area growth rate of 20% per month (P = 0.014, exponential model). Initiation of antiangiogenic treatment halted their growth. In comparison, exudation occurred in only 6 of the 53 eyes (11%) that lacked a precursor nonexudative CNV. Cox proportional hazard analysis showed that having nonexudative CNV detected was associated with an 18.1-fold increase in the rate of exudation subsequently developing (P < 0.0001).

Conclusions: Nonexudative CNV frequently is detected by OCTA in the fellow eyes of those with exudative CNV. These lesions carry a high risk of exudation developing within the first year after detection and could benefit from close monitoring. The high risk of progression may justify prophylactic treatment; further studies are needed.

PMID: 31068262 DOI: 10.1016/j.oret.2019.03.008

 

Invest Ophthalmol Vis Sci. 2019 May 1;60(6):1937-1942.

Impact of drusen volume on quantitative fundus autofluorescence in early and intermediate age-related macular degeneration.

Reiter GS, Told R, Schlanitz FG, Bogunovic H, Baumann L, Sacu S, Schmidt-Erfurth U, Pollreisz A.

Purpose: Drusen volume (DV) and quantitative autofluorescence (qAF) are potential indicators of progression in age-related macular degeneration (AMD). This prospective and observational study examined the association between DV and qAF of the retinal pigment epithelium.

Methods: Eighty-eight eyes of 52 patients with early and intermediate AMD were included. The mean follow-up was 9.2 ± 5.6 months, resulting in 312 examinations. DV was extracted from 6 × 6-mm spectral-domain optical coherence tomography scans. qAF was measured using a rotated Delori pattern. The associations between qAF and DV, age, sex, and lens status were investigated using linear mixed models.

Results: Patients' mean age was 75.6 ± 5.0 years (range, 61.0-83.4 years). Sixty-eight eyes (77.3%) were from females. No significant association between DV and qAF was found, neither within the total outer Early Treatment Diabetic Retinopathy Study (ETDRS) grid nor for ETDRS segments six to nine (all P > 0.05). Sex and lens status were not associated with qAF (P = 0.429 and P = 0.213, respectively). A significant association between age and qAF (P = 0.025) was found, indicating a decrease of qAF with age.

Conclusions: Quantification of DV and fundus autofluorescence did not reveal any correlation in early and intermediate AMD. qAF decreased with age, whereas DV increased in about half of the patients. This finding is a quantitative corroboration that fundus autofluorescence and the buildup of drusen are not correlated processes in AMD.

PMID: 31050721 DOI: 10.1167/iovs.19-26566

 

Pathogenesis

Curr Eye Res. 2019 May 4.

The placental growth factor pathway and its potential role in macular degenerative disease.

Cunningham F, Van Bergen T, Canning P, Lengyel I, Feyen JHM, Stitt AW.

Abstract: There is growing evidence that placental growth factor (PlGF) is an important player in multiple pathologies, including tumorigenesis, inflammatory disorders and degenerative retinopathies. PlGF is a member of the vascular endothelial growth factor (VEGF) family and in the retina, binding of this growth factor to specific receptors is associated with pathological angiogenesis, vascular leakage, neurodegeneration and inflammation. Although they share some receptor signalling pathways, many of the actions of PlGF are distinct from VEGF and this has revealed the enticing prospect that it could be a useful therapeutic target for treating early and late stages of diabetic retinopathy (DR) and neovascular age-related macular degeneration (AMD). Recent research suggests that modulation of PlGF could also be important in the geographic atrophy (GA) form of late AMD by protecting the outer retina and the retinal pigment epithelium (RPE). This review discusses PlGF and its signalling pathways and highlights the potential of blocking the bioactivity of this growth factor to treat irreversible visual loss due to the two main forms of AMD.

PMID: 31055948 DOI: 10.1080/02713683.2019.1614197

 

Am J Pathol. 2019 Apr 30. pii: S0002-9440(18)30884-8.

Choriocapillaris degeneration in geographic atrophy.

Sohn EH, Flamme-Wiese MJ, Whitmore SS, Workalemahu G, Marneros AG, Boese EA, Kwon YH, Wang K, Abramoff MD, Tucker BA, Stone EM, Mullins RF.

Abstract: Early age-related macular degeneration (AMD) is characterized by degeneration of the choriocapillaris, the vascular supply of retinal photoreceptor cells. We assessed vascular loss during disease progression in the choriocapillaris and larger vessels in the deeper choroid. Human donor maculas from controls (n=99), early AMD (n=35), or clinically diagnosed with geographic atrophy (GA; n=9, collected from outside the zone of retinal pigment epithelium degeneration) were evaluated using Ulex europaeus agglutinin-I labeling to discriminate between vessels with intact endothelial cells and ghost vessels. Morphometric analyses of choriocapillaris density (cross sectional area of capillary lumens divided by length) and of vascular lumen-to-stroma ratio in the outer choroid were performed. Choriocapillaris loss was observed in early AMD (Bonferroni corrected P (pcorr)=0.024) with greater loss in GA (pcorr <10-9) even in areas of intact retinal pigment epithelium. In contrast, changes in lumen-to-stroma ratio in the outer choroid were not found to differ between controls and AMD or GA eyes (P >0.05), suggesting that changes in the choriocapillaris are more prevalent in AMD than those in the outer choroid. In addition, vascular endothelial growth factor-A levels were negatively correlated with choriocapillaris vascular density. These findings support the concept that choroidal vascular degeneration contributes to dry AMD, and that these changes are predominant in the microvasculature. Addressing the capillary loss in AMD remains an important translational target.

PMID: 31051169 DOI: 10.1016/j.ajpath.2019.04.005

 

Mar Drugs. 2019 Apr 30;17(5). pii: E258.

Effects of fucoidans from five different brown algae on oxidative stress and VEGF interference in ocular cells.

Dörschmann P, Bittkau KS, Neupane S, Roider J, Alban S, Klettner A.

Background: Fucoidans are interesting for potential usage in ophthalmology, and especially age-related macular degeneration. However, fucoidans from different species may vary in their effects. Here, we compare fucoidans from five algal species in terms of oxidative stress protection and vascular endothelial growth factor (VEGF) interference in ocular cells.

Methods: Brown algae (Fucus vesiculosus, Fucus distichus subsp. evanescens, Fucus serratus, Laminaria digitata, Saccharina latissima) were harvested and fucoidans isolated by hot-water extraction. Fucoidans were tested in several concentrations (1, 10, 50, and 100 µg/mL). Effects were measured on a uveal melanoma cell line (OMM-1) (oxidative stress), retinal pigment epithelium (RPE) cell line ARPE19 (oxidative stress and VEGF), and primary RPE cells (VEGF). Oxidative stress was induced by H2O2 or tert-Butyl hydroperoxide (TBHP). Cell viability was investigated with methyl thiazolyl tetrazolium (MTT or MTS) assay, and VEGF secretion with ELISA. Affinity to VEGF was determined by a competitive binding assay.

Results: All fucoidans protected OMM-1 from oxidative stress. However, in ARPE19, only fucoidan from Saccharina latissima was protective. The affinity to VEGF of all fucoidans was stronger than that of heparin, and all reduced VEGF secretion in ARPE19. In primary RPE, only the fucoidan from Saccharina latissima was effective.

Conclusion: Among the fucoidans from five different species, Saccharina latissima displayed the most promising results concerning oxidative stress protection and reduction of VEGF secretion.

PMID: 31052228 DOI: 10.3390/md17050258

 

Bioanalysis. 2019 May 9.

Development and evaluation of an ultrasensitive free VEGF-A immunoassay for analysis of human aqueous humor.

Göpfert JC, Reiser A, Yañez VC, Pohle A, Wessels U, Heine A, Joos TO, Petit-Frère C, Nogoceke E, Stubenrauch KG.

Aim: Novel bifunctional VEGF-A neutralizing therapies are being developed for the treatment of retinal vascular diseases such as age-related macular degeneration and diabetic retinopathy. In developing new therapeutic drugs, only small aqueous humor sample volumes are available for analyzing several parameters. Highly sensitive detection methods must be applied in analyzing VEGF-A levels in ocular fluids in order to demonstrate VEGF-A suppression following drug administration.

Experimental: A highly sensitive immunoassay for VEGF-A was developed on the single molecule array (Simoa) platform, and validated before being used for the analysis of clinical aqueous humor samples from patients treated with anti-VEGF-A therapeutics.

Results: This highly sensitive immunoassay allows the detection of baseline VEGF-A levels and suppression effects after drug administration, even in sample volumes as low as 12 μl.

Conclusion: The Simoa VEGF-A assay is a valuable tool for the reliable monitoring of VEGF-A suppression after intravitreal administration of anti-VEGF-A drugs.

PMID: 31070047 DOI: 10.4155/bio-2019-0044

 

J Biol Chem. 2019 May 9. pii: jbc.RA119.008697. doi: 10.1074/jbc.RA119.008697. [Epub ahead of print]

The selective estrogen receptor modulator raloxifene mitigates the effect of all-trans-retinal toxicity in photoreceptor degeneration.

Getter T, Suh S, Hoang T, Handa JT, Dong Z, Ma X, Chen Y, Blackshaw S, Palczewski K.

Abstract: The retinoid cycle is a metabolic process in the vertebrate retina that continuously regenerates 11-cis-retinal (11-cisRAL) from the all-trans-retinal (atRAL) isomer. AtRAL accumulation can cause photoreceptor degeneration and irreversible visual dysfunction associated with incurable blinding retinal diseases such as stargardt disease, retinitis pigmentosa (RP), and atrophic age-related macular degeneration (AMD). The underlying cellular mechanisms leading to retinal degeneration remain uncertain, although previous studies have shown that atRAL promotes calcium influx associated with cell apoptosis. To identify compounds that mitigate the effects of atRAL toxicity, here we developed an unbiased and robust image-based assay that can detect changes in intracellular calcium levels in U2OS cells. Using our assay in a high-throughput screen of 2400 compounds, we noted  that selective estrogen receptor modulators (SERMs) potentpotently stabilize intracellular calcium and thereby counteract atRAL-induced toxicity. In a light-induced retinal degeneration mouse model (Abca4-/-Rdh8-/-), raloxifene (a benzothiophene-type scaffold SERM) prevented the onset of photoreceptor apoptosis and thus protected the retina from degeneration. The minor structural differences between raloxifene and one of its derivatives (Y 134) had a major impact on calcium homeostasis after atRAL exposure in vitro, and we verified this differential impact in vivo. In summary, the SERM raloxifene has structural and functional neuroprotective effects in the retina. We propose that the highly sensitive image-based assay developed here could be applied for the discovery of additional drug candidates preventing photoreceptor degeneration.

PMID: 31073029 DOI: 10.1074/jbc.RA119.008697

 

Genetics

Exp Eye Res. 2019 May 7. pii: S0014-4835(19)30272-6.

Molecular characterization of foveal versus peripheral human retina by single-cell RNA sequencing.

Voigt AP, Whitmore SS, Flamme-Wiese MJ, Riker M, Wiley LA, Tucker BA, Stone EM, Mullins RF, Scheetz TE.

Abstract: The human retina is a complex tissue responsible for detecting photons of light and converting information from these photons into the neurochemical signals interpreted as vision. Such visual signaling not only requires sophisticated interactions between multiple classes of neurons, but also spatially-dependent molecular specialization of individual cell types. In this study, we performed single-cell RNA sequencing on neural retina isolated from both the fovea and peripheral retina in three human donors. We recovered a total of 8,217 cells, with 3,578 cells originating from the fovea and 4,639 cells originating from the periphery. Expression profiles for all major retinal cell types were compiled, and differential expression analysis was performed between cells of foveal versus peripheral origin. Globally, mRNA for the serum iron binding protein transferrin (TF), which has been associated with age-related macular degeneration pathogenesis, was enriched in peripheral samples. Cone photoreceptor cells were of particular interest and formed two predominant clusters based on gene expression. One cone cluster had 96% of cells originating from foveal samples, while the second cone cluster consisted exclusively of peripherally isolated cells. A total of 148 genes were differentially expressed between cones from the fovea versus periphery. Interestingly, peripheral cones were enriched for the gene encoding Beta-Carotene Oxygenase 2 (BCO2). A relative deficiency of this enzyme may account for the accumulation of carotenoids responsible for yellow pigment deposition within the macula. Overall, this data set provides rich expression profiles of the major human retinal cell types and highlights transcriptomic features that distinguish foveal and peripheral cells.

PMID: 31075224 DOI: 10.1016/j.exer.2019.05.001

 

Tissue engineering

Drug Discov Today. 2019 Apr 30. pii: S1359-6446(18)30396-9.

Retinal cell regeneration using tissue engineered polymeric scaffolds.

Abedin Zadeh M, Khoder M, Al-Kinani AA, Younes HM, Alany RG.

Abstract: Degenerative retinal diseases, such as age-related macular degeneration (AMD), can lead to permanent sight loss. Although intravitreal anti-vascular endothelial growth factor (VEGF) and steroid injections are effective for the management of early stages of wet and/or neovascular AMD (nAMD), no proven treatments currently exist for dry AMD or for the advanced geographic atrophy of the retina that follows. Tissue engineering (TE) has recently emerged as a promising alternative to repair retinal damaged and restore its functions. Here, we review recent advances in TE, with a particular emphasis on retinal regeneration. We provide an overview of retinal diseases, followed by a comprehensive review of TE techniques, cells, and polymers used in the fabrication of scaffolds for retinal cell regenerations, in particular the retinal pigment epithelium (RPE).

PMID: 31051266 DOI: 10.1016/j.drudis.2019.04.009