Good Manufacturing Practice-compliant human induced pluripotent stem cells: from bench to putative clinical products.

BACKGROUND AIMS: Few human induced pluripotent stem cell (hiPSC) lines are Good Manufacturing Practice (GMP)-compliant, limiting the clinical use of hiPSC-derived products. Here, we addressed this by establishing and validating an in-house platform to produce GMP-compliant hiPSCs that would be appropriate for producing both allogeneic and autologous hiPSC-derived products. METHODS: Our standard research protocol for hiPSCs production was adapted and translated into a GMP-compliant platform. In addition to the generation of GMP-compliant hiPSC, the platform entails the methodology for donor recruitment, consent and screening, donor material procurement, hiPSCs manufacture, in-process control, specific QC test validation, QC testing, product release, hiPSCs storage and stability testing. For platform validation, one test run and three production runs were performed. Highest-quality lines were selected to establish master cell banks (MCBs). RESULTS: Two MCBs were successfully released under GMP conditions. They demonstrated safety (sterility, negative mycoplasma, endotoxins <5.0 EU/mL and negative adventitious agents), cell identity (>75% of cells expressing markers of undifferentiated state, identical STR profile, normal karyotype in >20 metaphases), purity (negative residual vectors and no plasmid integration in the genome) and potency (expression of at least two of the three markers for each of the three germ layers). In addition, directed differentiation to somitoids (skeletal muscle precursors) and six potential clinical products from all three germ layers was achieved: pancreatic islets (endoderm), kidney organoids and cardiomyocytes (mesoderm), and keratinocytes, GABAergic interneurons and inner-ear organoids (ectoderm). CONCLUSIONS: We successfully developed and validated a platform for generating GMP-compliant hiPSC lines. The two MCBs released were shown to differentiate into clinical products relevant for our own and other regenerative medicine interests.

CRB1 is required for recycling by RAB11A+ vesicles in human retinal organoids.

CRB1 gene mutations can cause early- or late-onset retinitis pigmentosa, Leber congenital amaurosis, or maculopathy. Recapitulating human CRB1 phenotypes in animal models has proven challenging, necessitating the development of alternatives. We generated human induced pluripotent stem cell (iPSC)-derived retinal organoids of patients with retinitis pigmentosa caused by biallelic CRB1 mutations and evaluated them against autologous gene-corrected hiPSCs and hiPSCs from healthy individuals. Patient organoids show decreased levels of CRB1 and NOTCH1 expression at the retinal outer limiting membrane. Proximity ligation assays show that human CRB1 and NOTCH1 can interact via their extracellular domains. CRB1 patient organoids feature increased levels of WDFY1+ vesicles, fewer RAB11A+ recycling endosomes, decreased VPS35 retromer complex components, and more degradative endolysosomal compartments relative to isogenic control organoids. Taken together, our data demonstrate that patient-derived retinal organoids enable modeling of retinal degeneration and highlight the importance of CRB1 in early endosome maturation receptor recycling in the retina.

AAV-mediated gene augmentation therapy of CRB1 patient-derived retinal organoids restores the histological and transcriptional retinal phenotype.

Retinitis pigmentosa and Leber congenital amaurosis are inherited retinal dystrophies that can be caused by mutations in the Crumbs homolog 1 (CRB1) gene. CRB1 is required for organizing apical-basal polarity and adhesion between photoreceptors and Müller glial cells. CRB1 patient-derived induced pluripotent stem cells were differentiated into CRB1 retinal organoids that showed diminished expression of variant CRB1 protein observed by immunohistochemical analysis. Single-cell RNA sequencing revealed impact on, among others, the endosomal pathway and cell adhesion and migration in CRB1 patient-derived retinal organoids compared with isogenic controls. Adeno-associated viral (AAV) vector-mediated hCRB2 or hCRB1 gene augmentation in Müller glial and photoreceptor cells partially restored the histological phenotype and transcriptomic profile of CRB1 patient-derived retinal organoids. Altogether, we show proof-of-concept that AAV.hCRB1 or AAV.hCRB2 treatment improved the phenotype of CRB1 patient-derived retinal organoids, providing essential information for future gene therapy approaches for patients with mutations in the CRB1 gene.

Generation of human induced pluripotent stem cell line EURACi006-A and its isogenic gene-corrected line EURACi006-A-1 from an arrhythmogenic cardiomyopathy patient carrying the c.1643delG PKP2 mutation.

Arrhythmogenic Cardiomyopathy (ACM) is a rare genetic cardiac disease predominantly associated with mutations in genes of the desmosomes and characterized by arrhythmia and fibro-fatty replacement of the myocardium. We generated human induced pluripotent stem cells (hiPSCs) from one patient affected by ACM carrying the heterozygous c.1643delG (p.G548VfsX15) PKP2 mutation and then corrected the mutation using CRISPR/Cas9 technology. Both original and corrected hiPSC lines showed typical morphology of pluripotent cells, expressed pluripotency markers, displayed a normal karyotype, and differentiated towards the three germ layers. This isogenic hiPSC pair can be used to study the role of the c.1643delG PKP2 mutation in vitro.

Reprogramming Urine-Derived Cells using Commercially Available Self-Replicative RNA and a Single Electroporation.

We describe a protocol for efficient generation of human-induced pluripotent stem cells (hiPSCs) from urine-derived cells (UDCs) obtained from adult donors using self-replicative RNA containing the reprogramming factors OCT3/4, SOX2, KLF4, GLIS1, and c-MYC (ReproRNA-OKSGM). After electroporation, transfection efficiency is quantified by measuring OCT3/4-expressing UDCs using flow cytometry and should be ≥0.1%. hiPSC colonies emerge within 3 weeks after transfection and express multiple pluripotency markers. Moreover, the UDC-derived hiPSCs are able to differentiate into cells of all three germ layers and display normal karyotypes. ReproRNA-OKSGM is available commercially and only requires a single transfection step so that the protocol is readily accessible, as well as straightforward. In addition to a detailed step-by-step description for generating clonal hiPSCs from UDCs using ReproRNA-OKSGM, we provide guidance for basic pluripotency characterization of the hiPSC lines. © 2020 The Authors. Basic Protocol: Reprogramming of urine-derived cells using ReproRNA-OKSGM Support Protocol 1: Determination of the pluripotency status of hiPSCs by flow cytometry Support Protocol 2: Characterization of functional pluripotency of hiPSCs.

Generation of human induced pluripotent stem cell line LUMCi027-A and its isogenic gene-corrected line from a patient affected by arrhythmogenic cardiomyopathy and carrying the c.2013delC PKP2 mutation.

Arrhythmogenic Cardiomyopathy (ACM) is a rare inherited heart muscle disease characterised by progressive fibro-fatty replacement of the ventricular myocardium leading to life-threatening arrhythmias. We generated human induced pluripotent stem cells (hiPSCs) from a patient affected by ACM and carrying the heterozygous c.2013delC (p.K672Rfs) PKP2 mutation and then corrected the mutation using CRISPR/Cas9 technology. Both hiPSC lines expressed pluripotency markers, maintained a normal karyotype, and differentiated into derivatives of the three germ layers. This isogenic hiPSC pair represents a genetically controlled system to study the role of the c.2013delC PKP2 mutation in vitro.

Generation of two human induced pluripotent stem cell lines, LUMCi020-A and LUMCi021-A, from two patients with Catecholaminergic Polymorphic Ventricular Tachycardia carrying heterozygous mutations in the RYR2 gene.

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a malignant channelopathy associated with exercise- and stress-induced cardiac sudden death. The autosomal dominant form of CPVT is due to mutations in the ryanodine receptor 2 (RYR2) gene. We generated induced pluripotent stem cells (hiPSCs) from skin fibroblasts of two patients carrying the c.12441 G>T and c.14885 A>G RYR2 missense mutations, respectively, using non-integrating Sendai virus. These lines show the typical morphology of pluripotent cells, express pluripotency markers, display a normal karyotype and differentiate towards the three germ layers in vitro. These lines represent a human cellular model to study the molecular basis of CPVT.