IntroductionThe discovery of induced pluripotent stem cells (iPSCs) revolutionized the field of translational medicine by enabling the reprogramming of adult somatic cells into a pluripotent state. From personalized disease models to innovative cell therapies, iPSCs are poised to play a central role in the future of clinical medicine. iPSCs hold enormous promises due to their ability to self-renew indefinitely and differentiate into all somatic cell types, thus offering patient-specific cellular models and therapeutic options without the ethical constraints of embryonic stem cells (ESCs). iPSCs, which exhibit pluripotency similar to embryonic stem cells, are generated by introducing specific factors into terminally differentiated cells, inducing a shift in their epigenetic and transcriptional landscape, which leads to the reactivation of the pluripotency program of the cells. Nevertheless, the mechanisms underlying successful reprogramming remain poorly understood.MethodsIn this study we performed a statistical evaluation of reprogramming efficiencies of 150 iPSC lines generated in our lab, comparing factors such as the starting somatic cell type, passage number, donor´s health status, donor age and sex, reprogramming methodology, and growth conditions.Results/DiscussionWe found that the most relevant factor influencing reprogramming efficiency is the developmental status of the starting cells. While other parameters may exert minor effects, inherent donor-specific biological characteristics appear to play the strongest role in determining reprogramming outcomes.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease characterized by adrenergically induced ventricular arrhythmias that cause sudden cardiac death. Using non-integrative episomal plasmids we reprogrammed skin fibroblasts of three heterozygous and two homozygous carriers of a mutation in the gene that encodes the ryanodine receptor type 2 (RYR2), RYR2_c.G1069A/p.G357S, previously associated to CPVT in a large family of the Gran Canaria Island. The resulting hiPSC cell lines have normal karyotype, differentiate into cells of the 3 germ layers, and express pluripotency markers and genes.

Patient-derived induced pluripotent stem cells (hiPSC) are a valuable approach to model cardiovascular diseases. We nucleofected non-integrating episomal vectors in skin fibroblasts of four family members. Two of them carried the single nucleotide variant (SNV) SCN5A_c.287 T > C, leading to NaV1.5_p.L96P, and two were non-carrier family members. The resulting hiPSC cell lines differentiate into cells of the 3 germ layers, display normal karyotypes and express markers of the undifferentiated hPSC state. Thus, they are a reliable source to study the effect of the identified mutation in a physiologically relevant environment.

Early embryos are exposed to environmental perturbations that may influence their development, including bacteria. Despite lacking a proper immune system, the surface epithelium of early embryos (trophectoderm in mammals) can phagocytose defective pluripotent cells. Here, we explore the dynamic interactions between early embryos and bacteria. Quantitative live imaging of infection models developed in zebrafish embryos reveals the efficient phagocytic capability of surface epithelia in detecting, ingesting, and destroying infiltrated E. coli and S. aureus. In vivo single-cell interferences uncover actin-based epithelial zippering protrusions mediating bacterial phagocytosis, safeguarding developmental robustness upon infection. Transcriptomic and inter-scale dynamic analyses of phagocyte-bacteria interactions identify specific features of this epithelial phagocytic program. Notably, live imaging of mouse and human blastocysts supports a conserved role of the trophectoderm in bacterial phagocytosis. This defensive role of the surface epithelium against bacterial infection provides immunocompetence to early embryos, with relevant implications for understanding failures in human embryogenesis.

mRNA reprogramming is a technology for generating iPSCs with high efficiency and safety. However, it is not suitable for reprogramming non-adherent cells, the primary cell type in blood. An alternative is to obtain adherent cells from blood for this technology. To validate this approach, we generated a human iPSC line from blood outgrowth endothelial cells (BOECs) using mRNA-based reprogramming. The resulting line, CTRL EiPS J9 mR6F-8, meets iPSC criteria, including an undifferentiated state, pluripotency, genome integrity. This line is available upon request.

There is a critical need worldwide for tissue for transplantation in patients with organ failure and with degenerative diseases with no treatments available.Cell therapy can represent an alternative to organ transplantation and for the treatment of degenerative diseases (such as heart failure, macular degeneration, type 1 diabetes, or Parkinson's disease, among others).The generation of human induced pluripotent stem cells offers a unique opportunity to obtain an unlimited supply of specialized cells.The use of patient's cells for the generation of human induced pluripotent stem cells and their derivatives for treatment ensures immunological compatibility and minimizes the risk of rejection.However, the time and cost necessary to produce customized human induced pluripotent stem cell lines and their derivatives in GMP conditions are excessively high.An alternative to the use of patient-specific human induced pluripotent stem cells would be an human induced pluripotent stem cell collection from allogeneic healthy donors that could be expanded and differentiated to treat different patients.This collection should comprise lines with enough diverse and compatible homozygous human leukocyte antigen to reduce the risk of immune rejection in a high percentage of the population.Homozygous human leukocyte antigen-matched iPSC lines suitable for a wide variety of homozygous human leukocyte antigen genotypes would be valuable for significant numbers of patients and will allow delivery of off-the-shelf cells for the manufacturing of cell therapy products for multiple diseases by reducing time and costs.HAPLO-iPS aims to create a collaborative network to provide a framework for human induced pluripotent stem cell generation of human induced pluripotent stem cells homozygous for frequent homozygous human leukocyte antigen haplotypes, compatible with a INDUCED PLURIPOTENT STEM CELLS (iPSCS) UNDERSTANDING THE CHALLENGESCurrently, some registries of available hPSCs do exist.The most prominent is hPSCreg, significant percentage of the population to be used for cell therapy clinical trials, and to collect a data collection system for such lines and all the associated data.

Human embryonic stem cells (hESCs) derived from blastocyst stage embryos present a primed state of pluripotency, whereas mouse ESCs (mESCs) display naïve pluripotency. Their unique characteristics make naïve hESCs more suitable for particular applications in biomedical research. This work aimed to derive hESCs from single blastomeres and determine their pluripotency state, which is currently unclear. We derived hESC lines from single blastomeres of 8-cell embryos and from whole blastocysts, and analysed several naïve pluripotency indicators, their transcriptomic profile and their trilineage differentiation potential. No significant differences were observed between blastomere-derived hESCs (bm-hESCs) and blastocyst-derived hESCs (bc-hESCs) for most naïve pluripotency indicators, including TFE3 localization, mitochondrial activity, and global DNA methylation and hydroxymethylation, nor for their trilineage differentiation potential. Nevertheless, bm-hESCs showed an increased single-cell clonogenicity and a higher expression of naïve pluripotency markers at early passages than bc-hESCs. Furthermore, RNA-seq revealed that bc-hESCs overexpressed a set of genes related to the post-implantational epiblast. Altogether, these results suggest that bm-hESCs, although displaying primed pluripotency, would be slightly closer to the naïve end of the pluripotency continuum than bc-hESCs.

Background Induced pluripotent stem cell (iPSC)-derived cell therapies are an interesting new area in the field of regenerative medicine. One of the approaches to decrease the costs of iPSC-derived therapies is the use of allogenic homozygous human leukocyte antigen (HLA)-matched donors to generate iPSC lines and to build a clinical-grade iPSC bank covering a high percentage of the Spanish population. Methods The Spanish Stem Cell Transplantation Registry was screened for cord blood units (CBUs) homozygous for the most common HLA-A, HLA-B and HLA-DRB1 haplotypes. Seven donors were selected with haplotypes covering 21.37% of the haplotypes of the Spanish population. CD34-positive hematopoietic progenitors were isolated from the mononuclear cell fraction of frozen cord blood units from each donor by density gradient centrifugation and further by immune magnetic labeling and separation using purification columns. Purified CD34 + cells were reprogrammed to iPSCs by transduction with the CTS CytoTune-iPS 2.1 Sendai Reprogramming Kit. Results The iPSCs generated from the 7 donors were expanded, characterized, banked and registered. Master cell banks (MCBs) and working cell banks (WCBs) from the iPSCs of each donor were produced under GMP conditions in qualified clean rooms. Conclusions Here, we present the first clinical-grade, iPSC haplobank in Spain made from CD34 + cells from seven cord blood units homozygous for the most common HLA-A, HLA-B and HLA-DRB1 haplotypes within the Spanish population. We describe their generation by transduction with Sendai viral vectors and their GMP-compliant expansion and banking. These haplolines will constitute starting materials for advanced therapy medicinal product development (ATMP).

Tissue-specific cells differentiated from patient-derived human induced pluripotent stem cells (hiPSC) are a relevant cellular model to study several diseases. We obtained a hiPSC line from skin fibroblasts of a patient affected by familial atrial fibrillation by nucleofection of non-integrating episomal vectors. The resulting hiPSC line displays a normal karyotype, expresses pluripotency surface markers and pluripotency genes, and differentiates into cells of the 3 germ layers. Therefore, it represents a reliable model to study the disease in a physiologically relevant cellular environment.

Transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) is a life-threatening disease caused by the abnormal production of misfolded TTR protein by liver cells, which is then released systemically. Its amyloid deposition in the heart is linked to cardiac toxicity and progression toward heart failure. A human induced pluripotent stem cell (iPSC) line was generated from peripheral blood mononuclear cells (PBMCs) from a patient suffering familial transthyretin amyloid cardiomyopathy carrying a c.128G>A (p.Ser43Asn) mutation in the TTR gene. This iPSC line offers a useful resource to study the disease pathophysiology and a cell-based model for therapeutic discovery.

NF2-related schwannomatosis is an autosomal dominant syndrome that predisposes to the development of benign tumors of the nervous system. Schwannomas, particularly bilateral vestibular schwannomas (VS), are the most characteristic features of the disease. These tumors are caused by the bi-allelic inactivation of the NF2 gene in a cell of the Schwann cell lineage. Our current understanding of the molecular pathogenesis of the NF2 gene, as well as the development of new effective therapies is hampered by the absence of human non-perishable cell-based bearing distinct NF2 pathogenic variants. With this aim, we generated and characterized three isogenic paired induced pluripotent stem cell (iPSC) lines with single or bi-allelic inactivation of NF2 by combining the direct reprogramming of VS cells with the use of CRISPR/Cas9 editing. Our results show a critical function of NF2 for the maintenance of a stable pluripotent state. However, we were able to nudge them towards the Neural Crest-Schwann Cell (NC-SC) axis by applying a 3D Schwann cell differentiation protocol. NF2 (+/−) and NF2 (−/−) spheroids homogeneously expressed classical markers of the NC-SC lineage. In addition, NF2 (−/−) SC-like spheroids showed dysregulation of multiple signaling pathways already described for merlin-deficient SC, and altered in human schwannomas. Therefore, NF2 (+/−) and NF2 (−/−) SC-like spheroids can represent a bona fide human in vitro cellular model to study the role of NF2 pathogenesis.### Competing Interest StatementThe authors have declared no competing interest.

The effects of genetic mutations on protein function can be studied in a physiologically relevant environment using tissue-specific cells differentiated from patient-derived induced pluripotent stem cells (iPSC). However, it is crucial to use iPSC derived from healthy individuals as control. We generated an iPS cell line from skin fibroblasts of a healthy Caucasian male by nucleofection of non-integrating episomal vectors. This cell line has normal karyotype, expresses pluripotency surface markers and pluripotency genes, and successfully differentiates into cells of the 3 germ layers. Therefore, it can be used as control for any disease of interest that is modelled using iPSC.

Patient-derived induced pluripotent stem cells (iPSC) are a valuable approach to model cardiovascular diseases. We nucleofected non-integrating episomal vectors in skin fibroblasts of three family members carrying a single nucleotide variant (SNV) in SCN5A, which encodes the cardiac-type sodium channel, and of a related healthy control. The SNV SCN5A_c.4573G > A had been previously identified in a Brugada Syndrome patient. The resulting iPS cell lines differentiate into cells of the 3 germ layers, display normal karyotypes and express pluripotency surface markers and genes. Thus, they are a reliable source to study the effect of the identified mutation in a physiologically relevant environment.

ABSTRACTNF2-related schwannomatosis is an autosomal dominant syndrome that predisposes to the development of benign tumors of the nervous system. Schwannomas, particularly bilateral vestibular schwannomas (VS), are the most characteristic features of the disease. These tumors are caused by the bi-allelic inactivation of theNF2gene in a cell of the Schwann cell lineage. Our current understanding of the molecular pathogenesis of theNF2gene, as well as the development of new effective therapies is hampered by the absence of human non-perishable cell-based bearing distinctNF2pathogenic variants. With this aim, we generated and characterized three isogenic paired induced pluripotent stem cell (iPSC) lines with single or bi-allelic inactivation ofNF2by combining the direct reprogramming of VS cells with the use of CRISPR/Cas9 editing. Our results show a critical function ofNF2for the maintenance of a stable pluripotent state. However, we were able to nudge them towards the Neural Crest-Schwann Cell (NC-SC) axis by applying a 3D Schwann cell differentiation protocol.NF2(+/−) andNF2(−/−) spheroids homogeneously expressed classical markers of the NC-SC lineage. In addition,NF2(−/−) SC-like spheroids showed dysregulation of multiple signaling pathways already described for merlin-deficient SC, and altered in human schwannomas. Therefore,NF2(+/−) andNF2(−/−) SC-like spheroids can represent a bona fide humanin vitrocellular model to study the role ofNF2pathogenesis.

Background: The aim of this study was to test the feasibility and safety of subretinal transplantation of human induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) cells into the healthy margins and within areas of degenerative retina in a swine model of geographic atrophy (GA). Methods: Well-delimited selective outer retinal damage was induced by subretinal injection of NaIO3 into one eye in minipigs (n = 10). Thirty days later, a suspension of hiPSC-derived RPE cells expressing green fluorescent protein was injected into the subretinal space, into the healthy margins, and within areas of degenerative retina. In vivo follow-up was performed by multimodal imaging. Post-mortem retinas were analyzed by immunohistochemistry and histology. Results: In vitro differentiated hiPSC-RPE cells showed a typical epithelial morphology, expressed RPE-related genes, and had phagocytic ability. Engrafted hiPSC-RPE cells were detected in 60% of the eyes, forming mature epithelium in healthy retina extending towards the border of the atrophy. Histological analysis revealed RPE interaction with host photoreceptors in the healthy retina. Engrafted cells in the atrophic zone were found in a patchy distribution but failed to form an epithelial-like layer. Conclusions: These results might support the use of hiPSC-RPE cells to treat atrophic GA by providing a housekeeping function to aid the overwhelmed remnant RPE, which might improve its survival and therefore slow down the progression of GA.

The value of human pluripotent stem cells (hPSC) in regenerative medicine has yet to reach its full potential. The road from basic research tool to clinically validated PSC-derived cell therapy products is a long and winding one, leading researchers, clinicians, industry and regulators alike into undiscovered territory. All stakeholders must work together to ensure the development of safe and effective cell therapies. Similarly, utilization of hPSC in meaningful and controlled disease modeling and drug screening applications requires information on the quality and suitability of the applied cell lines. Central to these common goals is the complete documentation of hPSC data, including the ethical provenance of the source material, the hPSC line derivation, culture conditions and genetic constitution of the lines. Data surrounding hPSC is scattered amongst diverse sources, including publications, supplemental data, researcher lab books, accredited lab reports, certificates of analyses and public data repositories. Not all of these data sources are publicly accessible nor associated with metadata nor stored in a standard manner, such that data can be easily found and retrieved. The Human Pluripotent Stem Cell Registry (hPSCreg; https://hpscreg.eu/) was started in 2007 to impart provenance and transparency towards hPSC research by registering and collecting standard properties of hPSC lines. In this chapter, we present a short primer on the history of stem cell-based products, summarize the ethical and regulatory issues introduced in the course of working with hPSC-derived products and their associated data, and finally present the Human Pluripotent Stem Cell Registry as a valuable resource for all stakeholders in therapies and disease modeling based on hPSC-derived cells.

Over the past 10 years’ significant research developments have taken place on human pluripotent stem cells and human embryonic stem cells to exploit the future potential in gene therapy and other focused treatments. There remains concerns around ethics of research and the fate of the human embryo used in such studies. European Board and College of Obstetrics and Gynaecology urge upon all scientists and the research bodies to adhere to the highest ethical principles of confidentiality and their actions should meet the criteria as set out by the international society for stem cell research.

The Spanish National Stem Cell Bank (Banco Nacional de Líneas Celulares, BNLC) was established in 2006 thanks to a change in the legislative framework in Spain. The Law 14/2006 updated the previous Assisted Reproduction Techniques Law (Law 45/2003) allowing the use of the surplus frozen embryos following IVF for research. The BNLC has a network structure with 3 nodes: the Regenerative Medicine Program (IDIBELL), the Principe Felipe Research Center (CIPF) in Valencia and the Andalusian Public Health System Biobank (SSPA Biobank) in Granada. The aim of the BNLC is to guarantee throughout the national territory the availability of human stem cell lines for biomedical research. At present time, there are 40 human embryonic stem cell lines (hESC) and 171 human induced pluripotent stem cell lines (hiPSC) registered in the BNLC. These lines are fully characterized and available in the context of research projects approved by the Technical Committee of the BNLC.