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Single-cell transcriptomics of the human retinal pigment epithelium and choroid in health and macular degeneration.

Mon, 2019-11-18 09:41
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Single-cell transcriptomics of the human retinal pigment epithelium and choroid in health and macular degeneration.

Proc Natl Acad Sci U S A. 2019 Nov 11;:

Authors: Voigt AP, Mulfaul K, Mullin NK, Flamme-Wiese MJ, Giacalone JC, Stone EM, Tucker BA, Scheetz TE, Mullins RF

Abstract
The human retinal pigment epithelium (RPE) and choroid are complex tissues that provide crucial support to the retina. Disease affecting either of these supportive tissues can lead to irreversible blindness in the setting of age-related macular degeneration. In this study, single-cell RNA sequencing was performed on macular and peripheral regions of RPE-choroid from 7 human donor eyes in 2 independent experiments. In the first experiment, total RPE/choroid preparations were evaluated and expression profiles specific to RPE and major choroidal cell populations were identified. As choroidal endothelial cells represent a minority of the total RPE/choroidal cell population but are strongly implicated in age-related macular degeneration (AMD) pathogenesis, a second single-cell RNA-sequencing experiment was performed using endothelial cells enriched by magnetic separation. In this second study, we identified gene expression signatures along the choroidal vascular tree, classifying the transcriptome of human choriocapillaris, arterial, and venous endothelial cells. We found that the choriocapillaris highly and specifically expresses the regulator of cell cycle gene (RGCC), a gene that responds to complement activation and induces apoptosis in endothelial cells. In addition, RGCC was the most up-regulated choriocapillaris gene in a donor diagnosed with AMD. These results provide a characterization of the human RPE and choriocapillaris transcriptome, offering potential insight into the mechanisms of choriocapillaris response to complement injury and choroidal vascular disease in age-related macular degeneration.

PMID: 31712411 [PubMed - as supplied by publisher]

Association of Genetic Variants With Primary Open-Angle Glaucoma Among Individuals With African Ancestry.

Mon, 2019-11-11 07:02
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Association of Genetic Variants With Primary Open-Angle Glaucoma Among Individuals With African Ancestry.

JAMA. 2019 11 05;322(17):1682-1691

Authors: Genetics of Glaucoma in People of African Descent (GGLAD) Consortium, Hauser MA, Allingham RR, Aung T, Van Der Heide CJ, Taylor KD, Rotter JI, Wang SJ, Bonnemaijer PWM, Williams SE, Abdullahi SM, Abu-Amero KK, Anderson MG, Akafo S, Alhassan MB, Asimadu I, Ayyagari R, Bakayoko S, Nyamsi PB, Bowden DW, Bromley WC, Budenz DL, Carmichael TR, Challa P, Chen YI, Chuka-Okosa CM, Cooke Bailey JN, Costa VP, Cruz DA, DuBiner H, Ervin JF, Feldman RM, Flamme-Wiese M, Gaasterland DE, Garnai SJ, Girkin CA, Guirou N, Guo X, Haines JL, Hammond CJ, Herndon L, Hoffmann TJ, Hulette CM, Hydara A, Igo RP, Jorgenson E, Kabwe J, Kilangalanga NJ, Kizor-Akaraiwe N, Kuchtey RW, Lamari H, Li Z, Liebmann JM, Liu Y, Loos RJF, Melo MB, Moroi SE, Msosa JM, Mullins RF, Nadkarni G, Napo A, Ng MCY, Nunes HF, Obeng-Nyarkoh E, Okeke A, Okeke S, Olaniyi O, Olawoye O, Oliveira MB, Pasquale LR, Perez-Grossmann RA, Pericak-Vance MA, Qin X, Ramsay M, Resnikoff S, Richards JE, Schimiti RB, Sim KS, Sponsel WE, Svidnicki PV, Thiadens AAHJ, Uche NJ, van Duijn CM, de Vasconcellos JPC, Wiggs JL, Zangwill LM, Risch N, Milea D, Ashaye A, Klaver CCW, Weinreb RN, Ashley Koch AE, Fingert JH, Khor CC

Abstract
Importance: Primary open-angle glaucoma presents with increased prevalence and a higher degree of clinical severity in populations of African ancestry compared with European or Asian ancestry. Despite this, individuals of African ancestry remain understudied in genomic research for blinding disorders.
Objectives: To perform a genome-wide association study (GWAS) of African ancestry populations and evaluate potential mechanisms of pathogenesis for loci associated with primary open-angle glaucoma.
Design, Settings, and Participants: A 2-stage GWAS with a discovery data set of 2320 individuals with primary open-angle glaucoma and 2121 control individuals without primary open-angle glaucoma. The validation stage included an additional 6937 affected individuals and 14 917 unaffected individuals using multicenter clinic- and population-based participant recruitment approaches. Study participants were recruited from Ghana, Nigeria, South Africa, the United States, Tanzania, Britain, Cameroon, Saudi Arabia, Brazil, the Democratic Republic of the Congo, Morocco, Peru, and Mali from 2003 to 2018. Individuals with primary open-angle glaucoma had open iridocorneal angles and displayed glaucomatous optic neuropathy with visual field defects. Elevated intraocular pressure was not included in the case definition. Control individuals had no elevated intraocular pressure and no signs of glaucoma.
Exposures: Genetic variants associated with primary open-angle glaucoma.
Main Outcomes and Measures: Presence of primary open-angle glaucoma. Genome-wide significance was defined as P < 5 × 10-8 in the discovery stage and in the meta-analysis of combined discovery and validation data.
Results: A total of 2320 individuals with primary open-angle glaucoma (mean [interquartile range] age, 64.6 [56-74] years; 1055 [45.5%] women) and 2121 individuals without primary open-angle glaucoma (mean [interquartile range] age, 63.4 [55-71] years; 1025 [48.3%] women) were included in the discovery GWAS. The GWAS discovery meta-analysis demonstrated association of variants at amyloid-β A4 precursor protein-binding family B member 2 (APBB2; chromosome 4, rs59892895T>C) with primary open-angle glaucoma (odds ratio [OR], 1.32 [95% CI, 1.20-1.46]; P = 2 × 10-8). The association was validated in an analysis of an additional 6937 affected individuals and 14 917 unaffected individuals (OR, 1.15 [95% CI, 1.09-1.21]; P < .001). Each copy of the rs59892895*C risk allele was associated with increased risk of primary open-angle glaucoma when all data were included in a meta-analysis (OR, 1.19 [95% CI, 1.14-1.25]; P = 4 × 10-13). The rs59892895*C risk allele was present at appreciable frequency only in African ancestry populations. In contrast, the rs59892895*C risk allele had a frequency of less than 0.1% in individuals of European or Asian ancestry.
Conclusions and Relevance: In this genome-wide association study, variants at the APBB2 locus demonstrated differential association with primary open-angle glaucoma by ancestry. If validated in additional populations this finding may have implications for risk assessment and therapeutic strategies.

PMID: 31688885 [PubMed - in process]

Imidazole Compounds for Protecting Choroidal Endothelial Cells from Complement Injury.

Mon, 2019-11-04 05:34
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Imidazole Compounds for Protecting Choroidal Endothelial Cells from Complement Injury.

Sci Rep. 2018 09 06;8(1):13387

Authors: Zeng S, Wen KK, Workalemahu G, Sohn EH, Wu M, Chirco KR, Flamme-Wiese MJ, Liu X, Stone EM, Tucker BA, Mullins RF

Abstract
Age-related macular degeneration (AMD) is a common, blinding disease associated with increased complement system activity. Eyes with AMD show elevated accumulation of the membrane attack complex (MAC) in the choriocapillaris and degeneration of macular choriocapillaris endothelial cells (ECs). Thus, one could reasonably conclude that the endothelial cell death that occurs in AMD is due to injury by the MAC. We therefore sought to identify strategies for protecting ECs against MAC lysis. RF/6A endothelial cells were pre-incubated with a library of FDA-approved small molecules, followed by incubation with complement intact human serum quantification of cell death. Two closely related molecules identified in the screen, econazole nitrate and miconazole nitrate, were followed in validation and mechanistic studies. Both compounds reduced lysis of choroidal ECs treated with complement-intact serum, across a range of doses from 1 to 100 µM. Cell rescue was confirmed in mouse primary choroidal ECs. Both exosome release and cell surface roughness (assessed using a Holomonitor system) were reduced by drug pretreatment in RF/6A cells, whereas endosome formation increased with both drugs, consistent with imidazole-mediated alterations of cell surface dynamics. The results in the current study provide further proof of principle that small molecules can protect choroidal ECs from MAC-induced cell death and suggest that FDA approved compounds may be beneficial in reducing vascular loss and progression of AMD.

PMID: 30190604 [PubMed - indexed for MEDLINE]

Effect of Molecular Weight and Functionality on Acrylated Poly(caprolactone) for Stereolithography and Biomedical Applications.

Sun, 2019-09-08 21:00
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Effect of Molecular Weight and Functionality on Acrylated Poly(caprolactone) for Stereolithography and Biomedical Applications.

Biomacromolecules. 2018 09 10;19(9):3682-3692

Authors: Green BJ, Worthington KS, Thompson JR, Bunn SJ, Rethwisch M, Kaalberg EE, Jiao C, Wiley LA, Mullins RF, Stone EM, Sohn EH, Tucker BA, Guymon CA

Abstract
Degradable polymers are integral components in many biomedical polymer applications. The ability of these materials to decompose in situ has become a critical component for tissue engineering, allowing scaffolds to guide cell and tissue growth while facilitating gradual regeneration of native tissue. The objective of this work is to understand the role of prepolymer molecular weight and functionality of photocurable poly(caprolactone) (PCL) in determining reaction kinetics, mechanical properties, polymer degradation, biocompatibility, and suitability for stereolithography. PCL, a degradable polymer used in a number of biomedical applications, was functionalized with acrylate groups to enable photopolymerization and three-dimensional printing via stereolithography. PCL prepolymers with different molecular weights and functionalities were studied to understand the role of molecular structure in reaction kinetics, mechanical properties, and degradation rates. The mechanical properties of photocured PCL were dependent on cross-link density and directly related to the molecular weight and functionality of the prepolymers. High-molecular weight, low-functionality PCLDA prepolymers exhibited a lower modulus and a higher strain at break, while low-molecular weight, high-functionality PCLTA prepolymers exhibited a lower strain at break and a higher modulus. Additionally, degradation profiles of cross-linked PCL followed a similar trend, with low cross-link density leading to degradation times up to 2.5 times shorter than those of more highly cross-linked polymers. Furthermore, photopolymerized PCL showed biocompatibility both in vitro and in vivo, causing no observed detrimental effects on seeded murine-induced pluripotent stem cells or when implanted into pig retinas. Finally, the ability to create three-dimensional PCL structures is shown by fabrication of simple structures using digital light projection stereolithography. Low-molecular weight, high-functionality PCLTA prepolymers printed objects with feature sizes near the hardware resolution limit of 50 μm. This work lays the foundation for future work in fabricating microscale PCL structures for a wide range of tissue regeneration applications.

PMID: 30044915 [PubMed - indexed for MEDLINE]

Helper-Dependent Adenovirus Transduces the Human and Rat Retina but Elicits an Inflammatory Reaction When Delivered Subretinally in Rats.

Sun, 2019-09-01 19:26
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Helper-Dependent Adenovirus Transduces the Human and Rat Retina but Elicits an Inflammatory Reaction When Delivered Subretinally in Rats.

Hum Gene Ther. 2019 Aug 28;:

Authors: Han IC, Burnight E, Ulferts MJ, Worthington KS, Russell SR, Sohn EH, Mullins RF, Stone E, Tucker BA, Wiley LA

Abstract
The identification of over 100 genes causing inherited retinal degeneration and the promising results of recent gene augmentation trials have led to an increase in the number of studies investigating the preclinical efficacy of viral-mediated gene transfer. Despite success using adeno-associated viruses (AAV), many disease-causing genes, like ABCA4 or USH2A, are too large to be packaged into these vectors. One option for large gene delivery is the family of integration deficient helper-dependent adenoviruses (HDAds), which efficiently transduce post-mitotic neurons. However, HDAds have been shown in other organ systems to elicit an immune response, and the immunogenicity of HDAds in the retina has not been characterized. In this study, HDAd5 was found to successfully transduce rod and cone photoreceptors in ex vivo human retinal organ cultures. The ocular inflammatory response to subretinal injection of the HDAd serotype 5 (HDAd5) was evaluated using a rat model. Subretinal injection of HDAd5 carrying cytomegalovirus promoter-driven enhanced Green Fluorescent Protein (HDAd5-CMVp-eGFP) elicited a robust inflammatory response by 3-days post-injection. This reaction included vitreous infiltration of Iba1-positive monocytes and increased expression of the pro-inflammatory protein, ICAM-1. By 7-days post-injection, most Iba1-positive infiltrates migrated into the neural retina, including the outer nuclear layer, and ICAM-1 expression was significantly increased compared to buffer-injected contralateral control eyes. At 14-days post-injection, Iba1-positive cells persisted in the retinas of HDAd5-injected eyes, and there was thinning of the outer nuclear layer indicative of photoreceptor cell loss. Subretinal injection of an empty HDAd5 virus was used to confirm that the inflammatory response was in response to the HDAd5 vector and not due to eGFP-induced overexpression cytotoxicity. Despite their larger carrying capacity, further work is needed to elucidate the inflammatory pathways involved and to identify an immunomodulation paradigm sufficient for safe and effective transfer of large genes to the retina using the HDAd5 system.

PMID: 31456426 [PubMed - as supplied by publisher]