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Using CRISPR-Cas9 to Generate Gene-Corrected Autologous iPSCs for the Treatment of Inherited Retinal Degeneration.

Tue, 2018-05-15 14:28
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Using CRISPR-Cas9 to Generate Gene-Corrected Autologous iPSCs for the Treatment of Inherited Retinal Degeneration.

Mol Ther. 2017 Sep 06;25(9):1999-2013

Authors: Burnight ER, Gupta M, Wiley LA, Anfinson KR, Tran A, Triboulet R, Hoffmann JM, Klaahsen DL, Andorf JL, Jiao C, Sohn EH, Adur MK, Ross JW, Mullins RF, Daley GQ, Schlaeger TM, Stone EM, Tucker BA

Abstract
Patient-derived induced pluripotent stem cells (iPSCs) hold great promise for autologous cell replacement. However, for many inherited diseases, treatment will likely require genetic repair pre-transplantation. Genome editing technologies are useful for this application. The purpose of this study was to develop CRISPR-Cas9-mediated genome editing strategies to target and correct the three most common types of disease-causing variants in patient-derived iPSCs: (1) exonic, (2) deep intronic, and (3) dominant gain of function. We developed a homology-directed repair strategy targeting a homozygous Alu insertion in exon 9 of male germ cell-associated kinase (MAK) and demonstrated restoration of the retinal transcript and protein in patient cells. We generated a CRISPR-Cas9-mediated non-homologous end joining (NHEJ) approach to excise a major contributor to Leber congenital amaurosis, the IVS26 cryptic-splice mutation in CEP290, and demonstrated correction of the transcript and protein in patient iPSCs. Lastly, we designed allele-specific CRISPR guides that selectively target the mutant Pro23His rhodopsin (RHO) allele, which, following delivery to both patient iPSCs in vitro and pig retina in vivo, created a frameshift and premature stop that would prevent transcription of the disease-causing variant. The strategies developed in this study will prove useful for correcting a wide range of genetic variants in genes that cause inherited retinal degeneration.

PMID: 28619647 [PubMed - indexed for MEDLINE]

Feeder-free differentiation of cells exhibiting characteristics of corneal endothelium from human induced pluripotent stem cells.

Tue, 2018-05-01 10:45
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Feeder-free differentiation of cells exhibiting characteristics of corneal endothelium from human induced pluripotent stem cells.

Biol Open. 2018 Apr 23;:

Authors: Wagoner MD, Bohrer LR, Aldrich BT, Greiner MA, Mullins RF, Worthington KS, Tucker BA, Wiley LA

Abstract
The purpose of this study was to devise a strategy for the derivation of corneal endothelial cells (CEnCs) from adult fibroblast-derived induced pluripotent stem cells (iPSCs). IPSCs were generated from an adult human with normal ocular history via expression of OCT4, SOX2, KLF4 and c-MYC Neural crest cells (NCCs) were differentiated from iPSCs via addition of CHIR99021 and SB4315542. NCCs were driven toward a CEnC fate via addition of B27, PDGF-BB and DKK-2 to CEnC media. Differentiation of NCCs and CEnCs was evaluated via rt-PCR, morphological and immunocytochemical analysis. At 17 days post-NCC induction, there were notable changes in cell morphology and upregulation of the neural crest lineage transcripts PAX3, SOX9, TFAP2A, SOX10 and p75NTR and the proteins p75/NGFR and SOX10. Exposure of NCCs to B27, PDGF-BB and DKK-2 induced a shift in morphology from a spindle-shaped neural phenotype to a tightly-packed hexagonal appearance and increased expression of the transcripts ATP1A1, COL8A1, COL8A2, AQP1 and CDH2 and the proteins, ZO-1, N-Cad, AQP-1 and Na+/K+ATPase. Replacement of NCC media with CEnC media on day 3, 5 or 8 reduced the differentiation time needed to yield CEnCs. IPSC-derived CEnCs could be used for evaluation of cornea endothelial disease pathophysiology and for testing of novel therapeutics.

PMID: 29685994 [PubMed - as supplied by publisher]

Generation of Xeno-Free, cGMP-Compliant Patient-Specific iPSCs from Skin Biopsy.

Tue, 2018-05-01 10:45
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Generation of Xeno-Free, cGMP-Compliant Patient-Specific iPSCs from Skin Biopsy.

Curr Protoc Stem Cell Biol. 2017 Aug 14;42:4A.12.1-4A.12.14

Authors: Wiley LA, Anfinson KR, Cranston CM, Kaalberg EE, Collins MM, Mullins RF, Stone EM, Tucker BA

Abstract
This unit describes protocols for the generation of clinical-grade patient-specific induced pluripotent stem cell (iPSC)-derived retinal cells from patients with inherited retinal degenerative blindness. Specifically, we describe how, using xeno-free reagents in an ISO class 5 environment, one can isolate and culture dermal fibroblasts, generate iPSCs, and derive autologous retinal cells via 3-D differentiation. The universal methods described herein for the isolation of dermal fibroblasts and generation of iPSCs can be employed regardless of disease, tissue, or cell type of interest. © 2017 by John Wiley & Sons, Inc.

PMID: 28806854 [PubMed - indexed for MEDLINE]

cGMP production of patient-specific iPSCs and photoreceptor precursor cells to treat retinal degenerative blindness.

Tue, 2018-05-01 10:45
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cGMP production of patient-specific iPSCs and photoreceptor precursor cells to treat retinal degenerative blindness.

Sci Rep. 2016 07 29;6:30742

Authors: Wiley LA, Burnight ER, DeLuca AP, Anfinson KR, Cranston CM, Kaalberg EE, Penticoff JA, Affatigato LM, Mullins RF, Stone EM, Tucker BA

Abstract
Immunologically-matched, induced pluripotent stem cell (iPSC)-derived photoreceptor precursor cells have the potential to restore vision to patients with retinal degenerative diseases like retinitis pigmentosa. The purpose of this study was to develop clinically-compatible methods for manufacturing photoreceptor precursor cells from adult skin in a non-profit cGMP environment. Biopsies were obtained from 35 adult patients with inherited retinal degeneration and fibroblast lines were established under ISO class 5 cGMP conditions. Patient-specific iPSCs were then generated, clonally expanded and validated. Post-mitotic photoreceptor precursor cells were generated using a stepwise cGMP-compliant 3D differentiation protocol. The recapitulation of the enhanced S-cone phenotype in retinal organoids generated from a patient with NR2E3 mutations demonstrated the fidelity of these protocols. Transplantation into immune compromised animals revealed no evidence of abnormal proliferation or tumor formation. These studies will enable clinical trials to test the safety and efficiency of patient-specific photoreceptor cell replacement in humans.

PMID: 27471043 [PubMed - indexed for MEDLINE]

CRISPR-Cas9 genome engineering: Treating inherited retinal degeneration.

Tue, 2018-04-03 03:00
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CRISPR-Cas9 genome engineering: Treating inherited retinal degeneration.

Prog Retin Eye Res. 2018 Mar 22;:

Authors: Burnight ER, Giacalone JC, Cooke JA, Thompson JR, Bohrer LR, Chirco KR, Drack AV, Fingert JH, Worthington KS, Wiley LA, Mullins RF, Stone EM, Tucker BA

Abstract
Gene correction is a valuable strategy for treating inherited retinal degenerative diseases, a major cause of irreversible blindness worldwide. Single gene defects cause the majority of these retinal dystrophies. Gene augmentation holds great promise if delivered early in the course of the disease, however, many patients carry mutations in genes too large to be packaged into adeno-associated viral vectors and some, when overexpressed via heterologous promoters, induce retinal toxicity. In addition to the aforementioned challenges, some patients have sustained significant photoreceptor cell loss at the time of diagnosis, rendering gene replacement therapy insufficient to treat the disease. These patients will require cell replacement to restore useful vision. Fortunately, the advent of induced pluripotent stem cell and CRISPR-Cas9 gene editing technologies affords researchers and clinicians a powerful means by which to develop strategies to treat patients with inherited retinal dystrophies. In this review we will discuss the current developments in CRISPR-Cas9 gene editing in vivo in animal models and in vitro in patient-derived cells to study and treat inherited retinal degenerative diseases.

PMID: 29578069 [PubMed - as supplied by publisher]

Evaluation of sFLT1 protein levels in human eyes with the FLT1 rs9943922 polymorphism.

Tue, 2018-04-03 03:00
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Evaluation of sFLT1 protein levels in human eyes with the FLT1 rs9943922 polymorphism.

Ophthalmic Genet. 2018 Jan-Feb;39(1):68-72

Authors: Chirco KR, Lewis CJ, Scheetz TE, Johnston RM, Tucker BA, Stone EM, Fingert JH, Mullins RF

Abstract
PURPOSE: Age-related macular degeneration (AMD) is a devastating disease characterized by central vision impairment in individuals with advanced age. Neovascular AMD is a form of end-stage disease in which choroidal vessel outgrowth occurs beneath the retina. While many hypotheses have been raised as to what triggers the formation of pathological choroidal neovascular membranes, the exact mechanism for their initiation remains unresolved. Polymorphisms in the FLT1 gene have previously been associated with neovascular AMD risk, including the rs9943922 single nucleotide polymorphism (SNP). Here, we aimed to determine the association between the high-risk FLT1 genotype and FLT1 protein levels in human retina or retinal pigment epithelium (RPE)/choroid tissue.
METHODS: Retina and RPE/choroid tissue from 10 human donor eyes was selected from a collection of eyes genotyped for the rs9943922 SNP. Differences in soluble and membrane bound FLT1 protein levels were assessed for retina versus RPE/choroid donor tissue using ELISA and Western blotting analyses. Genotype-associated changes in FLT1 protein levels were also evaluated.
RESULTS: We found soluble FLT1 levels in the RPE/choroid tissue to be approximately three times higher than that of the retina (p < 0.001), while both samples have similar levels of the membrane bound form. When tissue with the rs9943922 SNP was compared with controls, no significant genotypic differences in FLT1 protein levels were observed.
CONCLUSIONS: Based on these data, we conclude that the rs9943922 SNP in the FLT1 gene does not result in a large difference in FLT1 protein levels, regardless of whether it is the soluble or the membrane bound form.

PMID: 28949775 [PubMed - indexed for MEDLINE]

CRISPR-Cas9-Based Genome Editing of Human Induced Pluripotent Stem Cells.

Mon, 2018-03-12 21:21
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CRISPR-Cas9-Based Genome Editing of Human Induced Pluripotent Stem Cells.

Curr Protoc Stem Cell Biol. 2018 Feb 28;44:5B.7.1-5B.7.22

Authors: Giacalone JC, Sharma TP, Burnight ER, Fingert JF, Mullins RF, Stone EM, Tucker BA

Abstract
Human induced pluripotent stem cells (hiPSCs) are the ideal cell source for autologous cell replacement. However, for patients with Mendelian diseases, genetic correction of the original disease-causing mutation is likely required prior to cellular differentiation and transplantation. The emergence of the CRISPR-Cas9 system has revolutionized the field of genome editing. By introducing inexpensive reagents that are relatively straightforward to design and validate, it is now possible to correct genetic variants or insert desired sequences at any location within the genome. CRISPR-based genome editing of patient-specific iPSCs shows great promise for future autologous cell replacement therapies. One caveat, however, is that hiPSCs are notoriously difficult to transfect, and optimized experimental design considerations are often necessary. This unit describes design strategies and methods for efficient CRISPR-based genome editing of patient- specific iPSCs. Additionally, it details a flexible approach that utilizes positive selection to generate clones with a desired genomic modification, Cre-lox recombination to remove the integrated selection cassette, and negative selection to eliminate residual hiPSCs with intact selection cassettes. © 2018 by John Wiley & Sons, Inc.

PMID: 29512106 [PubMed - in process]

Patient-specific induced pluripotent stem cells to evaluate the pathophysiology of TRNT1-associated Retinitis pigmentosa.

Mon, 2018-03-12 21:21
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Patient-specific induced pluripotent stem cells to evaluate the pathophysiology of TRNT1-associated Retinitis pigmentosa.

Stem Cell Res. 2017 May;21:58-70

Authors: Sharma TP, Wiley LA, Whitmore SS, Anfinson KR, Cranston CM, Oppedal DJ, Daggett HT, Mullins RF, Tucker BA, Stone EM

Abstract
Retinitis pigmentosa (RP) is a heterogeneous group of monogenic disorders characterized by progressive death of the light-sensing photoreceptor cells of the outer neural retina. We recently identified novel hypomorphic mutations in the tRNA Nucleotidyl Transferase, CCA-Adding 1 (TRNT1) gene that cause early-onset RP. To model this disease in vitro, we generated patient-specific iPSCs and iPSC-derived retinal organoids from dermal fibroblasts of patients with molecularly confirmed TRNT1-associated RP. Pluripotency was confirmed using rt-PCR, immunocytochemistry, and a TaqMan Scorecard Assay. Mutations in TRNT1 caused reduced levels of full-length TRNT1 protein and expression of a truncated smaller protein in both patient-specific iPSCs and iPSC-derived retinal organoids. Patient-specific iPSCs and iPSC-derived retinal organoids exhibited a deficit in autophagy, as evidenced by aberrant accumulation of LC3-II and elevated levels of oxidative stress. Autologous stem cell-based disease modeling will provide a platform for testing multiple avenues of treatment in patients suffering from TRNT1-associated RP.

PMID: 28390992 [PubMed - indexed for MEDLINE]

Two-photon polymerization for production of human iPSC-derived retinal cell grafts.

Mon, 2018-03-05 17:09
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Two-photon polymerization for production of human iPSC-derived retinal cell grafts.

Acta Biomater. 2017 Jun;55:385-395

Authors: Worthington KS, Wiley LA, Kaalberg EE, Collins MM, Mullins RF, Stone EM, Tucker BA

Abstract
Recent advances in induced pluripotent stem cell (iPSC) technology have paved the way for the production of patient-specific neurons that are ideal for autologous cell replacement for treatment of neurodegenerative diseases. In the case of retinal degeneration and associated photoreceptor cell therapy, polymer scaffolds are critical for cellular survival and integration; however, prior attempts to materialize this concept have been unsuccessful in part due to the materials' inability to guide cell alignment. In this work, we used two-photon polymerization to create 180μm wide non-degradable prototype photoreceptor scaffolds with varying pore sizes, slicing distances, hatching distances and hatching types. Hatching distance and hatching type were significant factors for the error of vertical pore diameter, while slicing distance and hatching type most affected the integrity and geometry of horizontal pores. We optimized printing parameters in terms of structural integrity and printing time in order to create 1mm wide scaffolds for cell loading studies. We fabricated these larger structures directly on a porous membrane with 3µm diameter pores and seeded them with human iPSC-derived retinal progenitor cells. After two days in culture, cells nested in and extended neuronal processes parallel to the vertical pores of the scaffolds, with maximum cell loading occurring in 25μm diameter pores. These results highlight the feasibility of using this technique as part of an autologous stem cell strategy for restoring vision to patients affected with retinal degenerative diseases.
STATEMENT OF SIGNIFICANCE: Cell replacement therapy is an important goal for investigators aiming to restore neural function to those suffering from neurodegenerative disease. Cell delivery scaffolds are frequently necessary for the success of such treatments, but traditional biomaterials often fail to facilitate the neuronal orientation and close packing needed to recapitulate the in vivo environment. Here, we use two-photon polymerization to create prototype cell scaffolds with densely packed vertical pores for photoreceptor cell loading and small, interconnected horizontal pores for nutrient diffusion. This study offers a thorough characterization of how two-photon polymerization parameters affect final structural outcomes and printing time. Our findings demonstrate the feasibility of using two-photon polymerization to create scaffolds that can align neuronal cells in 3D and are large enough to be used for transplantation. In future work, these scaffolds could comprise biodegradable materials with tunable microstructure, elastic modulus and degradation time; a significant step towards a promising treatment option for those suffering from late-stage neurodegeneration, including retinal degenerative blindness.

PMID: 28351682 [PubMed - indexed for MEDLINE]