The role of human leukocyte antigen matching in the development of multiethnic "haplobank" of induced pluripotent stem cell lines

Past, present, and future of cell replacement therapy for parkinson's disease: a novel emphasis on host immune responses

Parkinson's disease (PD) stands as the second most common neurodegenerative disorder after Alzheimer's disease, and its prevalence continues to rise with the aging global population. Central to the pathophysiology of PD is the specific degeneration of midbrain dopamine neurons (mDANs) in the substantia nigra. Consequently, cell replacement therapy (CRT) has emerged as a promising treatment approach, initially supported by various open-label clinical studies employing fetal ventral mesencephalic (fVM) cells. Despite the initial favorable results, fVM cell therapy has intrinsic and logistical limitations that hinder its transition to a standard treatment for PD. Recent efforts in the field of cell therapy have shifted its focus towards the utilization of human pluripotent stem cells, including human embryonic stem cells and induced pluripotent stem cells, to surmount existing challenges. However, regardless of the transplantable cell sources (e.g., xenogeneic, allogeneic, or autologous), the poor and variable survival of implanted dopamine cells remains a major obstacle. Emerging evidence highlights the pivotal role of host immune responses following transplantation in influencing the survival of implanted mDANs, underscoring an important area for further research. In this comprehensive review, building upon insights derived from previous fVM transplantation studies, we delve into the functional ramifications of host immune responses on the survival and efficacy of grafted dopamine cells. Furthermore, we explore potential strategic approaches to modulate the host immune response, ultimately aiming for optimal outcomes in future clinical applications of CRT for PD.

Regenerative treatment of ophthalmic diseases with stem cells: Principles, progress, and challenges

Background

Degenerate eye disorders, such as glaucoma, cataracts and age-related macular degeneration (AMD), are prevalent causes of blindness and visual impairment worldwide. Other eye disorders, including limbal stem cell deficiency (LSCD), dry eye diseases (DED), and retinitis pigmentosa (RP), result in symptoms such as ocular discomfort and impaired visual function, significantly impacting quality of life. Traditional therapies are limited, primarily focus on delaying disease progression, while emerging stem cell therapy directly targets ocular tissues, aiming to restore ocular function by reconstructing ocular tissue.

Main text

The utilization of stem cells for the treatment of diverse degenerative ocular diseases is becoming increasingly significant, owing to the regenerative and malleable properties of stem cells and their functional cells. Currently, stem cell therapy for ophthalmopathy involves various cell types, such as embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), and retinal progenitor cells (RPCs). In the current article, we will review the current progress regarding the utilization of stem cells for the regeneration of ocular tissue covering key eye tissues from the cornea to the retina. These therapies aim to address the loss of functional cells, restore damaged ocular tissue and or in a paracrine-mediated manner. We also provide an overview of the ocular disorders that stem cell therapy is targeting, as well as the difficulties and opportunities in this field.

Conclusions

Stem cells can not only promote tissue regeneration but also release exosomes to mitigate inflammation and provide neuroprotection, making stem cell therapy emerge as a promising approach for treating a wide range of eye disorders through multiple mechanisms.

Innovations in bio-engineering and cell-based approaches to address immunological challenges in islet transplantation

Human allogeneic pancreatic islet transplantation is a life-changing treatment for patients with severe Type 1 Diabetes (T1D) who suffer from hypoglycemia unawareness and high risk of severe hypoglycemia. However, intensive immunosuppression is required to prevent immune rejection of the graft, that may in turn lead to undesirable side effects such as toxicity to the islet cells, kidney toxicity, occurrence of opportunistic infections, and malignancies. The shortage of cadaveric human islet donors further limits islet transplantation as a treatment option for widespread adoption. Alternatively, porcine islets have been considered as another source of insulin-secreting cells for transplantation in T1D patients, though xeno-transplants raise concerns over the risk of endogenous retrovirus transmission and immunological incompatibility. As a result, technological advancements have been made to protect transplanted islets from immune rejection and inflammation, ideally in the absence of chronic immunosuppression, to improve the outcomes and accessibility of allogeneic islet cell replacement therapies. These include the use of microencapsulation or macroencapsulation devices designed to provide an immunoprotective environment using a cell-impermeable layer, preventing immune cell attack of the transplanted cells. Other up and coming advancements are based on the use of stem cells as the starting source material for generating islet cells 'on-demand'. These starting stem cell sources include human induced pluripotent stem cells (hiPSCs) that have been genetically engineered to avoid the host immune response, curated HLA-selected donor hiPSCs that can be matched with recipients within a given population, and multipotent stem cells with natural immune privilege properties. These strategies are developed to provide an immune-evasive cell resource for allogeneic cell therapy. This review will summarize the immunological challenges facing islet transplantation and highlight recent bio-engineering and cell-based approaches aimed at avoiding immune rejection, to improve the accessibility of islet cell therapy and enhance treatment outcomes. Better understanding of the different approaches and their limitations can guide future research endeavors towards developing more comprehensive and targeted strategies for creating a more tolerogenic microenvironment, and improve the effectiveness and sustainability of islet transplantation to benefit more patients.

Clinical translation of pluripotent stem cell-based therapies: successes and challenges

The translational stem cell research field has progressed immensely in the past decade. Development and refinement of differentiation protocols now allows the generation of a range of cell types, such as pancreatic β-cells and dopaminergic neurons, from human pluripotent stem cells (hPSCs) in an efficient and good manufacturing practice-compliant fashion. This has led to the initiation of several clinical trials using hPSC-derived cells to replace lost or dysfunctional cells, demonstrating evidence of both safety and efficacy. Here, we highlight successes from some of the hPSC-based trials reporting early signs of efficacy and discuss common challenges in clinical translation of cell therapies.

HLA-based banking of induced pluripotent stem cells in Saudi Arabia

BACKGROUND

Human iPSCs' derivation and use in clinical studies are transforming medicine. Yet, there is a high cost and long waiting time associated with autologous iPS-based cellular therapy, and the genetic engineering of hypo-immunogenic iPS cell lines is hampered with numerous hurdles. Therefore, it is increasingly interesting to create cell stocks based on HLA haplotype distribution in a given population. This study aimed to assess the potential of HLA-based iPS banking for the Saudi population.

METHODS

In this study, we interrogated the HLA database of the Saudi Stem Cell Donor Registry (SSCDR), containing high-resolution HLA genotype data from 64,315 registered Saudi donors at the time of analysis. This database was considered to be a representative sample of the Saudi population. The most frequent HLA haplotypes in the Saudi population were determined, and an in-house developed iterative algorithm was used to identify their HLA matching percentages in the SSCDR database and cumulative coverage. Subsequently, to develop a clinically relevant protocol for iPSCs generation, and to illustrate the applicability of the concept of HLA-based banking for cell therapy purposes, the first HLA-based iPS cell line in Saudi Arabia was generated. Clinically relevant methods were employed to generate the two iPS clones from a homozygous donor for the most prevalent HLA haplotype in the Saudi population. The generated lines were then assessed for pluripotency markers, and their ability to differentiate into all three germ layers, beating cardiomyocytes, and neural progenitors was examined. Additionally, the genetic stability of the HLA-iPS cell lines was verified by comparing the mutational burden in the clones and the original blood sample, using whole-genome sequencing. The standards set by the American College of Medical Genetics and Genomics (ACMG) were used to determine the clinical significance of identified variants.

RESULTS

The analysis revealed that the establishment of only 13 iPSC lines would match 30% of the Saudi population, 39 lines would attain 50% coverage, and 596 lines would be necessary for over 90% coverage. The proof-of-concept HLA-iPSCs, which cover 6.1% of the Saudi population, successfully demonstrated pluripotency and the ability to differentiate into various cell types including beating cardiomyocytes and neuronal progenitors. The comprehensive genetic analysis corroborated that all identified variants in the derived iPSCs were inherently present in the original donor sample and were classified as benign according to the standards set by the ACMG.

CONCLUSIONS

Our study sets a road map for introducing iPS-based cell therapy in the Kingdom of Saudi Arabia. It underscores the pragmatic approach of HLA-based iPSC banking which circumvents the limitations of autologous iPS-based cellular therapies. The successful generation and validation of iPSC lines based on the most prevalent HLA haplotype in the Saudi population signify a promising step toward broadening the accessibility and applicability of stem cell therapies and regenerative medicine in Saudi Arabia.

Challenges of CRISPR/Cas-Based Cell Therapy for Type 1 Diabetes: How Not to Engineer a "Trojan Horse"

Type 1 diabetes mellitus (T1D) is an autoimmune disease caused by the destruction of insulin-producing β-cells in the pancreas by cytotoxic T-cells. To date, there are no drugs that can prevent the development of T1D. Insulin replacement therapy is the standard care for patients with T1D. This treatment is life-saving, but is expensive, can lead to acute and long-term complications, and results in reduced overall life expectancy. This has stimulated the research and development of alternative treatments for T1D. In this review, we consider potential therapies for T1D using cellular regenerative medicine approaches with a focus on CRISPR/Cas-engineered cellular products. However, CRISPR/Cas as a genome editing tool has several drawbacks that should be considered for safe and efficient cell engineering. In addition, cellular engineering approaches themselves pose a hidden threat. The purpose of this review is to critically discuss novel strategies for the treatment of T1D using genome editing technology. A well-designed approach to β-cell derivation using CRISPR/Cas-based genome editing technology will significantly reduce the risk of incorrectly engineered cell products that could behave as a "Trojan horse".

'Off the shelf' immunotherapies: Generation and application of pluripotent stem cell-derived immune cells

In recent years, great strides have been made toward the development of immune cell-based therapies in the treatment of refractory malignancies. Primary T cells and NK cells armed with chimeric antigen receptors have achieved tremendous clinical success especially in patients with leukaemia and lymphoma. However, the autologous origin of these effector cells means that a single batch of laboriously engineered cells treats only a certain patient, leading to high cost, ununiform product quality, and risk of delay in treatment, and therefore results in restricted accessibility of these therapies to the overwhelming majority of the patients. Addressing these tricky obstacles calls for the development of universal immune cell products that can be provided 'off the shelf' in a large amount. Pluripotent stem cells (PSCs), owing to their unique capacity of self-renewal and the potential of multi-lineage differentiation, offer an unlimited cell source to generate uniform and scalable engineered immune cells. This review discusses the major advances in the development of PSC-derived immune cell differentiation approaches and their therapeutic potential in treating both hematologic malignancies and solid tumours. We also consider the potency of PSC-derived immune cells as an alternative therapeutic strategy for other diseases, such as autoimmune diseases, fibrosis, infections, et al.

Current Status and Future Perspectives on Stem Cell-Based Therapies for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting 1%-2% of the population over the age of 65. As the population ages, it is anticipated that the burden on society will significantly escalate. Although symptom reduction by currently available pharmacological and/or surgical treatments improves the quality of life of many PD patients, there are no treatments that can slow down, halt, or reverse disease progression. Because the loss of a specific cell type, midbrain dopamine neurons in the substantia nigra, is the main cause of motor dysfunction in PD, it is considered a promising target for cell replacement therapy. Indeed, numerous preclinical and clinical studies using fetal cell transplantation have provided proof of concept that cell replacement therapy may be a viable therapeutic approach for PD. However, the use of human fetal cells remains fraught with controversy due to fundamental ethical, practical, and clinical limitations. Groundbreaking work on human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, coupled with extensive basic research in the stem cell field offers promising potential for hPSC-based cell replacement to become a realistic treatment regimen for PD once several major issues can be successfully addressed. In this review, we will discuss the prospects and challenges of hPSC-based cell therapy for PD.

Blood donor biobank and HLA imputation as a resource for HLA homozygous cells for therapeutic and research use

Background

Allogeneic therapeutic cells may be rejected if they express HLA alleles not found in the recipient. As finding cell donors with a full HLA match to a recipient requires vast donor pools, the use of HLA homozygous cells has been suggested as an alternative. HLA homozygous cells should be well tolerated by those who carry at least one copy of donor HLA alleles. HLA-A-B homozygotes could be valuable for HLA-matched thrombocyte products. We evaluated the feasibility of blood donor biobank and HLA imputation for the identification of potential cell donors homozygous for HLA alleles.

Methods

We imputed HLA-A, -B, -C, -DRB1, -DQA1, -DQB1 and -DPB1 alleles from genotypes of 20,737 Finnish blood donors in the Blood Service Biobank. We confirmed homozygosity by sequencing HLA alleles in 30 samples and by examining 36,161 MHC-located polymorphic DNA markers.

Results

Three hundred and seventeen individuals (1.5%), representing 41 different haplotypes, were found to be homozygous for HLA-A, -B, -C, -DRB1, -DQA1 and -DQB1 alleles. Ten most frequent haplotypes homozygous for HLA-A to -DQB1 were HLA-compatible with 49.5%, and three most frequent homozygotes to 30.4% of the Finnish population. Ten most frequent HLA-A-B homozygotes were compatible with 75.3%, and three most frequent haplotypes to 42.6% of the Finnish population. HLA homozygotes had a low level of heterozygosity in MHC-located DNA markers, in particular in HLA haplotypes enriched in Finland.

Conclusions

The present study shows that HLA imputation in a blood donor biobank of reasonable size can be used to identify HLA homozygous blood donors suitable for cell therapy, HLA-typed thrombocytes and research. The homozygotes were HLA-compatible with a large fraction of the Finnish population. Regular blood donors reported to have positive attitude to research donation appear a good option for these purposes. Differences in population frequencies of HLA haplotypes emphasize the need for population-specific collections of HLA homozygous samples.

Engineering immunomodulatory hydrogels and cell-laden systems towards bone regeneration

The well-known synergetic interplay between the skeletal and immune systems has changed the design of advanced bone tissue engineering strategies. The immune system is essential during the bone lifetime, with macrophages playing multiple roles in bone healing and biomaterial integration. If in the past, the most valuable aspect of implants was to avoid immune responses of the host, nowadays, it is well-established how important are the crosstalks between immune cells and bone-engineered niches for an efficient regenerative process to occur. For that, it is essential to recapitulate the multiphenotypic cellular environment of bone tissue when designing new approaches. Indeed, the lack of osteoimmunomodulatory knowledge may be the explanation for the poor translation of biomaterials into clinical practice. Thus, smarter hydrogels incorporating immunomodulatory bioactive factors, stem cells, and immune cells are being proposed to develop a new generation of bone tissue engineering strategies. This review highlights the power of immune cells to upgrade the development of innovative engineered strategies, mainly focusing on orthopaedic and dental applications.

Long-term survival in non-human primates of stem cell-derived, MHC-unmatched corneal epithelial cell sheets

When corneal epithelial stem cells residing in the corneal limbus become dysfunctional, called a limbal stem cell deficiency (LSCD), corneal transparency is decreased, causing severe vision loss. Transplantation of corneal epithelial cell sheets (CEPS) derived from stem cells, including induced pluripotent stem cells, is a promising treatment for LSCD. However, the potential effect of human leukocyte antigen (HLA) concordance on CEPS transplantation has not been addressed. Here, we show that there is no difference in the immune response to CEPS between HLA-matched and -unmatched peripheral blood mononuclear cells in mixed lymphocyte reactions. CEPS transplantation in cynomolgus monkeys revealed that the immune response to major histocompatibility-unmatched CEPS was not strong and could be controlled by local steroid administration. Furthermore, programmed death ligand 1 was identified as an immunosuppressive molecule in CEPS under inflammatory conditions in vitro. Our results indicate that corneal epithelium has low immunogenicity and allogeneic CEPS transplantation requires mild immunosuppression.

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There is no difference in the immune response to CEPS owing to HLA conformity in MLR

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The immune response to MHC-unmatched CEPS is not strong after transplantation

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Local steroid administration could control the immune response to MHC-unmatched CEPS

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PD-L1 was identified as an immunosuppressive molecule in CEPS

Pancreatic β-Cell Development and Regeneration

The pancreatic β-cells are essential for regulating glucose homeostasis through the coordinated release of the insulin hormone. Dysfunction of the highly specialized β-cells results in diabetes mellitus, a growing global health epidemic. In this review, we describe the development and function of β-cells the emerging concept of heterogeneity within insulin-producing cells, and the potential of other cell types to assume β-cell functionality via transdifferentiation. We also discuss emerging routes to design cells with minimal β-cell properties and human stem cell differentiation efforts that carry the promise to restore normoglycemia in patients suffering from diabetes.

What did we learn from neural grafts in Huntington disease?

Huntington's disease is a rare, severe, and inherited neurodegenerative disorder that affects young adults. To date, there is no treatment to stop its progression. The primary atrophy of the striatum in HD, is limited in space and centrally focalised in the brain and thus constitutes a good candidate for graft. Therefore, transplantation of foetal cells from the ganglionic eminence, the germinal zone of the striatum, has the potential to restore disrupted fronto-cortical circuits and corresponding clinical functions. The international Multicentric intracerebral Grafting in Huntington's disease trial was not as successful as two pilot trials (Créteil and London) which showed promising results in the 2000s, displaying stabilisation/recovery of symptoms in some patients. A point-by-point comparison of the differences between MIG-HD and the pilot trial from Créteil in which similar data are available provides lessons on the grafting procedure and allows for strategic thinking before embarking on future trials. MIG-HD demonstrated the existence of intracerebral alloimmunisation leading to acute or chronic graft rejection into the brain and showed the limitations of surgical standardisation and immunosuppression. It has also improved the safety of the procedure and provided guidance for the follow-up of future patients. Indeed, even if disease modifiers treatments are currently the focus of intense research, they may not stop or slow the progression of the disease sufficiently, or even be administered in all patients, to prevent brain atrophy in all cases. Although disease-modifying therapies are currently the subject of intense research, they may not stop or slow disease progression sufficiently, or may not be given to all patients to prevent brain atrophy. A combination with intracerebral transplantation to repair the damaged structures may thus prove beneficial. Altogether, pursuing research in intracerebral transplantation remains necessary.

Assessment of Safety and Immunogenicity of MHC homozygous iPSC-derived CD34+ Hematopoietic Progenitors in a NHP Model

Infusion of iHPs is safe and well tolerated in NHPs.

iHPs are hypoimmunogenic and can be administered with a low risk of alloimmunization.

Administration of ex vivo expanded somatic myeloid progenitors has been explored as a way to facilitate a more rapid myeloid recovery and improve overall survival after myeloablation. Recent advances in induced pluripotent stem cell (iPSC) technologies have created alternative platforms for supplying off-the-shelf immunologically compatible myeloid progenitors, including cellular products derived from major histocompatibility complex (MHC) homozygous superdonors, potentially increasing the availability of MHC-matching cells and maximizing the utility of stem cell banking. However, the teratogenic and tumorigenic potential of iPSC-derived progenitor cells and whether they will induce alloreactive antibodies upon transfer remain unclear. We evaluated the safety and efficacy of using CD34⁺CD45⁺ hematopoietic progenitors derived from MHC homozygous iPSCs (iHPs) to treat cytopenia after myeloablative hematopoietic stem cell (HSC) transplantation in a Mauritian cynomolgus macaque (MCM) nonhuman primate (NHP) model. We demonstrated that infusion of iHPs was well tolerated and safe, observing no teratomas or tumors in the MCMs up to 1 year after HSC transplantation and iHP infusion. Importantly, the iHPs also did not induce significant levels of alloantibodies in MHC-matched or -mismatched immunocompetent MCMs, even after increasing MHC expression on iHPs with interferon-γ. These results support the feasibility of iHP use in the setting of myeloablation and suggest that iHP products pose a low risk of inducing alloreactive antibodies.

Toward in Vitro Production of Platelet from Induced Pluripotent Stem Cells

Platelets (PLTs) are small anucleate blood cells that release from polyploidy megakaryocytes(MKs). PLT transfusion is standard therapy to prevent hemorrhage. PLT transfusion is donor-dependent way which have limitations including the inadequate donor blood supply, poor quality, and issues related to infection and immunity. Overcoming these obstacles is possible with in vitro production of human PLTs. Currently several cells have been considered as source to in vitro production of PLTs such as hematopoietic stem cells (HSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). However, HSCs are a limited source for PLT production and large-scale expansion of HSC-derived PLT remains difficult. Alternative sources can be ESCs which have unlimited expansion capacity. But ESCs have ethical issues related to destroying human embryos. iPSCs are considered as an ideal unlimited source for PLT production. They are able to differentiate into any cells and have the capacity of self-renewal. Moreover, iPSCs can be acquired from any donor and easily manipulated. Due to new advances in development of MK cell lines, bioreactors, feeder cell-free production and the ability of large scale generation, iPSC-based PLTs are moving toward clinical applicability and considering the minimal risk of alloimmunization and tumorigenesis of these products, there is great hopefulness they will become the standard source for blood transfusions in the future. This review will focus on how to progress of in vitro generation of PLT from stem cell especially iPSCs and some of the successful strategies that can be easily used in clinic will be described.

Advances in Manufacturing Cardiomyocytes from Human Pluripotent Stem Cells

The emergence of human pluripotent stem cell (hPSC) technology over the past two decades has provided a source of normal and diseased human cells for a wide variety of in vitro and in vivo applications. Notably, hPSC-derived cardiomyocytes (hPSC-CMs) are widely used to model human heart development and disease and are in clinical trials for treating heart disease. The success of hPSC-CMs in these applications requires robust, scalable approaches to manufacture large numbers of safe and potent cells. Although significant advances have been made over the past decade in improving the purity and yield of hPSC-CMs and scaling the differentiation process from 2D to 3D, efforts to induce maturation phenotypes during manufacturing have been slow. Process monitoring and closed-loop manufacturing strategies are just being developed. We discuss recent advances in hPSC-CM manufacturing, including differentiation process development and scaling and downstream processes as well as separation and stabilization. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 13 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Prospects for Development of Induced Pluripotent Stem Cell-Derived CAR-Targeted Immunotherapies

Technologies required to generate induced pluripotent stem cells (iPSC) were first described 15 years ago, providing a strong impetus to the field of regenerative medicine. In parallel, immunotherapy has finally emerged as a clinically meaningful modality of cancer therapy. In particular, impressive efficacy has been achieved in patients with selected haematological malignancies using ex vivo expanded autologous T cells engineered to express chimeric antigen receptors (CARs). While solid tumours account for over 90% of human cancer, they currently are largely refractory to this therapeutic approach. Nonetheless, given the considerable innovation taking place worldwide in the CAR field, it is likely that effective solutions for common solid tumours will emerge in the near future. Such a development will create significant new challenges in the scalable delivery of these complex, costly and individualised therapies. CAR-engineered immune cell products that originate from iPSCs offer the potential to generate unlimited numbers of homogeneous, standardised cell products in which multiple defined gene modification events have been introduced to ensure safety, potency and reproducibility. Here, we review some of the emerging strategies in use to engineer CAR-expressing iPSC-derived drug products.

Systemic Supplementation of Collagen VI by Neonatal Transplantation of iPSC-Derived MSCs Improves Histological Phenotype and Function of Col6-Deficient Model Mice

Collagen VI is distributed in the interstitium and is secreted mainly by mesenchymal stromal cells (MSCs) in skeletal muscle. Mutations in COL6A1-3 genes cause a spectrum of COL6-related myopathies. In this study, we performed a systemic transplantation study of human-induced pluripotent stem cell (iPSC)-derived MSCs (iMSCs) into neonatal immunodeficient COL6-related myopathy model (Col6a1^KO/NSG) mice to validate the therapeutic potential. Engraftment of the donor cells and the resulting rescued collagen VI were observed at the quadriceps and diaphragm after intraperitoneal iMSC transplantation. Transplanted mice showed improvement in pathophysiological characteristics compared with untreated Col6a1^KO/NSG mice. In detail, higher muscle regeneration in the transplanted mice resulted in increased muscle weight and enlarged myofibers. Eight-week-old mice showed increased muscle force and performed better in the grip and rotarod tests. Overall, these findings support the concept that systemic iMSC transplantation can be a therapeutic option for COL6-related myopathies.

Somatic Reprogramming-Above and Beyond Pluripotency

Pluripotent stem cells, having long been considered the fountain of youth, have caught the attention of many researchers from diverse backgrounds due to their capacity for unlimited self-renewal and potential to differentiate into all cell types. Over the past 15 years, the advanced development of induced pluripotent stem cells (iPSCs) has displayed an unparalleled potential for regenerative medicine, cell-based therapies, modeling human diseases in culture, and drug discovery. The transcription factor quartet (Oct4, Sox2, Klf4, and c-Myc) reprograms highly differentiated somatic cells back to a pluripotent state recapitulated embryonic stem cells (ESCs) in different aspects, including gene expression profile, epigenetic signature, and functional pluripotency. With the prior fruitful studies in SCNT and cell fusion experiments, iPSC finds its place and implicates that the differentiated somatic epigenome retains plasticity for re-gaining the pluripotency and further stretchability to reach a totipotency-like state. These achievements have revolutionized the concept and created a new avenue in biomedical sciences for clinical applications. With the advent of 15 years’ progress-making after iPSC discovery, this review is focused on how the current concept is established by revisiting those essential landmark studies and summarizing its current biomedical applications status to facilitate the new era entry of regenerative therapy.

Implantation of Human-Induced Pluripotent Stem Cell-Derived Cartilage in Bone Defects of Mice

Although bone has an innate capacity for repair, clinical situations such as comminuted fracture, open fracture, or the surgical resection of bone tumors produce critical-sized bone defects that exceed the capacity and require external intervention. Initiating endochondral ossification (EO) by the implantation of a cartilaginous template into the bone defect is a relatively new approach to cure critical-sized bone defects. The combination of chondrogenically primed mesenchymal stromal/stem cells and artificial scaffolds has been the most extensively studied approach for inducing endochondral bone formation in bone defects. In this study, we prepared cartilage (human-induced pluripotent stem [hiPS]-Cart) from hiPS cells (hiPSCs) in a scaffoldless manner and implanted hiPS-Cart into 3.5 mm large defects created in the femurs of immunodeficient mice to examine the repair capacity. For the control, nothing was implanted into the defects. The implantation of hiPS-Cart significantly induced more new bone in the defect compared with the control. Culture periods for the chondrogenic differentiation of hiPSCs significantly affected the speed of bone induction, with less time resulting in faster bone formation. Histological analysis revealed that hiPS-Cart induced new bone formation in a manner resembling EO of the secondary ossification center, with the cartilage canal, which extended from the periphery to the center of hiPS-Cart, initially forming in unmineralized cartilage, followed by chondrocyte hypertrophy at the center. In the newly formed bone, the majority of osteocytes, osteoblasts, and adipocytes expressed human nuclear antigen (HNA), suggesting that these types of cells mainly derived from the perichondrium of hiPS-Cart. Osteoclasts and blood vessel cells did not express HNA and thus were mouse. Finally, integration between the newly formed bone and mouse femur was attained substantially. Although hiPS-Cart induced new bone that filled bone defects, the newly formed bone, which is a hybrid of human and mouse, had not remodeled to mature bone within the observation period of this study (28 weeks).

Autologous Induced Pluripotent Stem Cell-Based Cell Therapies: Promise, Progress, and Challenges

The promise of human induced pluripotent stem cells (iPSCs) lies in their ability to serve as a starting material for autologous, or patient-specific, stem cell-based therapies. Since the first publications describing the generation of iPSCs from human tissue in 2007, a Phase I/IIa clinical trial testing an autologous iPSC-derived cell therapy has been initiated in the U.S., and several other autologous iPSC-based therapies have advanced through various stages of development. Three single-patient in-human transplants of autologous iPSC-derived cells have taken place worldwide. None of the patients suffered serious adverse events, despite not undergoing immunosuppression. These promising outcomes support the proposed advantage of an autologous approach: a cell therapy product that can engraft without the risk of immune rejection, eliminating the need for immunosuppression and the associated side effects. Despite this advantage, there are currently more allogeneic than autologous iPSC-based cell therapy products in development due to the cost and complexity of scaling out manufacturing for each patient. In this review, we highlight recent progress toward clinical translation of autologous iPSC-based cell therapies. We also highlight technological advancements that would reduce the cost and complexity of autologous iPSC-based cell therapy production, enabling autologous iPSC-based therapies to become a more commonplace treatment modality for patients. © 2021 The Authors.

Evaluation of the Spanish population coverage of a prospective HLA haplobank of induced pluripotent stem cells

Background

iPSC (induced pluripotent stem cells) banks of iPSC lines with homozygous HLA (human leukocyte antigen) haplotypes (haplobanks) are proposed as an affordable and off-the-shelf approach to allogeneic transplantation of iPSC derived cell therapies. Cord blood banks offer an extensive source of HLA-typed cells suitable for reprogramming to iPSC. Several initiatives worldwide have been undertaken to create national and international iPSC haplobanks that match a significant part of a population.

Methods

To create an iPSC haplobank that serves the Spanish population (IPS-PANIA), we have searched the Spanish Bone Marrow Donor Registry (REDMO) to identify the most frequently estimated haplotypes. From the top ten donors identified, we estimated the population coverage using the criteria of zero mismatches in HLA-A, HLA-B, and HLA-DRB1 with different stringencies: high resolution, low resolution, and beneficial mismatch.

Results

We have calculated that ten cord blood units from homozygous donors stored at the Spanish cord blood banks can provide HLA-A, HLA-B, and HLA-DRB1 matching for 28.23% of the population.

Conclusion

We confirm the feasibility of using banked cord blood units to create an iPSC haplobank that will cover a significant percentage of the Spanish and international population for future advanced therapy replacement strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02301-0.

Reprogramming: Emerging Strategies to Rejuvenate Aging Cells and Tissues

Aging is associated with a progressive and functional decline of all tissues and a striking increase in many "age-related diseases". Although aging has long been considered an inevitable process, strategies to delay and potentially even reverse the aging process have recently been developed. Here, we review emerging rejuvenation strategies that are based on reprogramming toward pluripotency. Some of these approaches may eventually lead to medical applications to improve healthspan and longevity.

Cell therapy in Huntington's disease: Taking stock of past studies to move the field forward

Huntington's disease (HD) is a rare inherited neurodegenerative disease that manifests mostly in adulthood with progressive cognitive, behavioral, and motor dysfunction. Neuronal loss occurs predominantly in the striatum but also extends to other brain regions, notably the cortex. Most patients die around 20 years after motor onset, although there is variability in the rate of progression and some phenotypic heterogeneity. The most advanced experimental therapies currently are huntingtin-lowering strategies, some of which are in stage 3 clinical trials. However, even if these approaches are successful, it is unlikely that they will be applicable to all patients or will completely halt continued loss of neural cells in all cases. On the other hand, cellular therapies have the potential to restore atrophied tissues and may therefore provide an important complementary therapeutic avenue. Pilot studies of fetal cell grafts in the 2000s reported the most dramatic clinical improvements yet achieved for this disease, but subsequent studies have so far failed to identify methodology to reliably reproduce these results. Moving forward, a major challenge will be to generate suitable donor cells from (nonfetal) cell sources, but in parallel there are a host of procedural and trial design issues that will be important for improving reliability of transplants and so urgently need attention. Here, we consider findings that have emerged from clinical transplant studies in HD to date, in particular new findings emerging from the recent multicenter intracerebral transplant HD study, and consider how these data may be used to inform future cell therapy trials.

CRISPR/Cas9 Ribonucleoprotein Complex-Mediated Efficient B2M Knockout in Human Induced Pluripotent Stem Cells (iPSCs)

Advances in induced pluripotent stem cell (iPSC) technology provide a renewable source of cells for tissue regeneration and therefore hold great promise for cell replacement therapy. However, immune rejection of allograft due to human leukocyte antigen (HLA) mismatching remains a major challenge. Considerable efforts have been devoted to overcoming the immunogenicity of allograft transplantation. One of the approaches is an elimination of HLA molecules on the surface of allogeneic cells using genome editing technology to generate universal stem cells. Here, we present a simple and effective genome editing approach to knockout the β-2-immunoglobulin (B2M) gene, which encodes B2M protein that forms a heterodimer with HLA class I proteins, in induced pluripotent stem cells (iPSCs) leading to HLA class I (HLA-I) depletion. We also describe detailed procedures for validation of the B2M-knockout iPSCs using flow cytometry, and genotypic analysis for potential off-target regions. Our protocol is also applicable for knocking out other genes in iPSCs and other cell types.

Enhancing Matured Stem-Cardiac Cell Generation and Transplantation: A Novel Strategy for Heart Failure Therapy

Heart failure (HF) remains one of the major causes of morbidity and mortality worldwide. Recent studies have shown that stem cells (SCs) including bone marrow mesenchymal stem (BMSC), embryonic bodies (EB), embryonic stem (ESC), human induced pluripotent stem (hiPSC)-derived cardiac cells generation, and transplantation treated myocardial infarction (MI) in vivo and in human. However, the immature phenotypes compromise their clinical application requiring immediate intervention to improve stem-derived cardiac cell (S-CCs) maturation. Recently, an unbiased multi-omic analysis involving genomics, transcriptomics, epigenomics, proteomics, and metabolomics identified specific strategies for the generation of matured S-CCs that may enhance patients' recovery processes upon transplantation. However, these strategies still remain undisclosed. Here, we summarize the recently discovered strategies for the matured S-CC generation. In addition, cardiac patch formation and transplantation that accelerated HF recuperation in clinical trials are discussed. A better understanding of this work may lead to efficient generation of matured S-CCs for regenerative medicine. Graphical abstract.

Human Pluripotent Stem Cells-Based Therapies for Neurodegenerative Diseases: Current Status and Challenges

Neurodegenerative diseases are characterized by irreversible cell damage, loss of neuronal cells and limited regeneration potential of the adult nervous system. Pluripotent stem cells are capable of differentiating into the multitude of cell types that compose the central and peripheral nervous systems and so have become the major focus of cell replacement therapies for the treatment of neurological disorders. Human embryonic stem cell (hESC) and human induced pluripotent stem cell (hiPSC)-derived cells have both been extensively studied as cell therapies in a wide range of neurodegenerative disease models in rodents and non-human primates, including Parkinson’s disease, stroke, epilepsy, spinal cord injury, Alzheimer’s disease, multiple sclerosis and pain. In this review, we discuss the latest progress made with stem cell therapies targeting these pathologies. We also evaluate the challenges in clinical application of human pluripotent stem cell (hPSC)-based therapies including risk of oncogenesis and tumor formation, immune rejection and difficulty in regeneration of the heterogeneous cell types composing the central nervous system.

Haplobanking induced pluripotent stem cells for clinical use

The development of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka and colleagues in 2006 has led to a potential new paradigm in cellular therapeutics, including the possibility of producing patient-specific, disease-specific and immune matched allogeneic cell therapies. One can envisage two routes to immunologically compatible iPSC therapies: using genetic modification to generate a 'universal donor' with reduced expression of Human Leukocyte Antigens (HLA) and other immunological targets or developing a haplobank containing iPSC lines specifically selected to provide HLA matched products to large portions of the population. HLA matched lines can be stored in a designated physical or virtual global bank termed a 'haplobank'. The process of 'iPSC haplobanking' refers to the banking of iPSC cell lines, selected to be homozygous for different HLA haplotypes, from which therapeutic products can be derived and matched immunologically to patient populations. By matching iPSC and derived products to a patient's HLA class I and II molecules, one would hope to significantly reduce the risk of immune rejection and the use of immunosuppressive medication. Immunosuppressive drugs are used in several conditions (including autoimmune disease and in transplantation procedures) to reduce rejection of infused cells, or transplanted tissue and organs, due to major and minor histocompatibility differences between donor and recipient. Such regimens can lead to immune compromise and pathological consequences such as opportunistic infections or malignancies due to decreased cancer immune surveillance. In this article, we will discuss what is practically involved if one is developing and executing an iPSC haplobanking strategy.

The Global Alliance for iPSC Therapies (GAiT)

The Global Alliance for iPSC Therapies (GAiT) is a new initiative to support the implementation and clinical application of therapies derived from pluripotent stem cells to the benefit of patients globally. GAiT's mission is to serve as a central, international resource for those organisations developing therapies from clinical-grade induced pluripotent stem cells, and to support the expansion of this nascent field. With the support of its international partners, GAiT already has an early position on manufacturing, regulatory and quality standards. This article details GAiT's development, its mission and structure, as well as how, and by whom, it is funded. The article ends with brief overview of current and upcoming activities.

[Novel platelet pharming using human induced pluripotent stem cells]

La production in vitro de plaquettes offre une opportunité de résoudre les problèmes liés aux limitations d’approvisionnement et à la sécurité des dons de produits dérivés du sang. Les cellules souches pluripotentes induites – ou iPSC – sont une source idéale pour la production de cellules à des fins de thérapies régénératives. Nous avons précédemment établi avec succès une lignée mégacaryocytaire immortalisée à partir d’iPSC. Celle-ci possède une capacité de prolifération fiable. Par ailleurs, il est possible de les cryoconserver. Elle est donc une source adaptée de cellules primaires pour la production de plaquettes suivant les Bonnes Pratiques de Fabrication (BPF). Dans le même temps, la capacité améliorée des bioréacteurs à reproduire certaines conditions physiologiques, telle que la turbulence, de pair avec la découverte de molécules favorisant la thrombopoïèse, a contribué à l’accomplissement de la production de plaquettes en quantité et qualité suffisantes pour répondre aux besoins cliniques. La production de plaquettes à partir de cellules iPS s’étend aussi aux patients en état de réfraction allo-immune, par la production de plaquettes autologues ou dont on a génétiquement manipulé l’expression des Antigènes des Leucocytes Humains (HLA) et des Antigènes Plaquettaires Humain (HPA). Considérant ces avancées fondamentales, les plaquettes iPSC avec expression des HLA modifiées se présentent comme un potentiel produit de transfusion universel. Dans cette revue, nous souhaitons apporter une vue d’ensemble de la production in vitro de plaquettes à partir de cellules iPS, et de son possible potentiel transformatif, d’importance capitale dans le domaine de la transfusion des produits sanguins.

New trends in cellular therapy

Regenerative therapies, including both gene and cellular therapies, aim to induce regeneration of cells, tissues and organs and restore their functions. In this short Spotlight, we summarize the latest advances in cellular therapies using pluripotent stem cells (PSCs), highlighting the current status of clinical trials using induced (i)PSC-derived cells. We also discuss the different cellular products that might be used in clinical studies, and consider safety issues and other challenges in iPSC-based cell therapy.

Electrospun Scaffolds and Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Cardiac Tissue Engineering Applications

Tissue engineering (TE) combines cells, scaffolds, and growth factors to assemble functional tissues for repair or replacement of tissues and organs. Cardiac TE is focused on developing cardiac cells, tissues, and structures-most notably the heart. This review presents the requirements, challenges, and research surrounding electrospun scaffolds and induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) towards applications to TE hearts. Electrospinning is an attractive fabrication method for cardiac TE scaffolds because it produces fibers that demonstrate the optimal potential for mimicking the complex structure of the cardiac extracellular matrix (ECM). iPSCs theoretically offer the capacity to generate limitless numbers of CMs for use in TE hearts, however these iPSC-CMs are electrophysiologically, morphologically, mechanically, and metabolically immature compared to adult CMs. This presents a functional limitation to their use in cardiac TE, and research aiming to address this limitation is presented in this review.

Emerging routes to the generation of functional β-cells for diabetes mellitus cell therapy

Diabetes mellitus, which affects more than 463 million people globally, is caused by the autoimmune ablation or functional loss of insulin-producing β-cells, and prevalence is projected to continue rising over the next decades. Generating β-cells to mitigate the aberrant glucose homeostasis manifested in the disease has remained elusive. Substantial advances have been made in producing mature β-cells from human pluripotent stem cells that respond appropriately to dynamic changes in glucose concentrations in vitro and rapidly function in vivo following transplantation in mice. Other potential avenues to produce functional β-cells include: transdifferentiation of closely related cell types (for example, other pancreatic islet cells such as α-cells, or other cells derived from endoderm); the engineering of non-β-cells that are capable of modulating blood sugar; and the construction of synthetic 'cells' or particles mimicking functional aspects of β-cells. This Review focuses on the current status of generating β-cells via these diverse routes, highlighting the unique advantages and challenges of each approach. Given the remarkable progress in this field, scalable bioengineering processes are also discussed for the realization of the therapeutic potential of derived β-cells.

Human pluripotent stem cells: A toolbox to understand and treat retinal degeneration

Age-related Macular Degeneration (AMD) and Retinitis Pigmentosa (RP) are retinal degenerative disorders that dramatically damage the retina. As there is no therapeutic option for the majority of patients, vision is progressively and irremediably lost. Owing to their unlimited renewal and potency to give rise to any cell type of the human adult body, human pluripotent stem cells (hPSCs) have been extensively studied in recent years to develop more physiologically relevant in vitro cellular models. Such models open new perspectives to investigate the pathological molecular mechanisms of AMD and RP but also in drug screening. Moreover, proof-of-concept of hPSC-derived retinal cell therapy in animal models have led to first clinical trials. This review outlines the recent advances in the use of hPSCs in pathological modeling of retinal degeneration and their use in regenerative medicine. We also address the associated limitations and challenges that need to be overcome when using hPSCs.

Clinical-Grade Human Pluripotent Stem Cells for Cell Therapy: Characterization Strategy

Human pluripotent stem cells have the potential to change the way in which human diseases are cured. Clinical-grade human embryonic stem cells and human induced pluripotent stem cells have to be created according to current good manufacturing practices and regulations. Quality and safety must be of the highest importance when humans' lives are at stake. With the rising number of clinical trials, there is a need for a consensus on hPSCs characterization. Here, we summarize mandatory and 'for information only' characterization methods with release criteria for the establishment of clinical-grade hPSC lines.

Ethical Aspects of Translating Research with Human Pluripotent Stem Cell Products into Clinical Practice: A Stakeholder Approach

Experimental therapies with embryonic stem cells (hESCs) and, more recently, human induced pluripotent stem cells (hiPSCs) are steadily gaining ground in clinical practice. The implementation of such novel high-risk/high-potential treatments calls for proper safeguards for the interests of the public and, most importantly, of research participants directly affected by the design and outcomes of trials. We argue that the active involvement of stakeholders in decision-making is ethically required. Public and patient involvement is a necessary prerequisite for dealing responsibly with high-risk/high-potential clinical research such as stem-cell research. Moreover, there is an urgent need for public debate, regionally and globally, about the present and future value of such types of research. A stakeholder approach that pays attention to all of the people and institutions involved, including patients and their organizations, will guide the translational process and maintain the public's trust in such a rapidly evolving scientific field.

iPSC-Derived Platelets Depleted of HLA Class I Are Inert to Anti-HLA Class I and Natural Killer Cell Immunity

The ex vivo production of platelets depleted of human leukocyte antigen class I (HLA-I) could serve as a universal measure to overcome platelet transfusion refractoriness caused by HLA-I incompatibility. Here, we developed human induced pluripotent cell-derived HLA-I-deficient platelets (HLA-KO iPLATs) in a clinically applicable imMKCL system by genetic manipulation and assessed their immunogenic properties including natural killer (NK) cells, which reject HLA-I downregulated cells. HLA-KO iPLATs were deficient for all HLA-I but did not elicit a cytotoxic response by NK cells in vitro and showed circulation equal to wild-type iPLATs upon transfusion in our newly established Hu-NK-MSTRG mice reconstituted with human NK cells. Additionally, HLA-KO iPLATs successfully circulated in an alloimmune platelet transfusion refractoriness model of Hu-NK-MISTRG mice. Mechanistically, the lack of NK cell-activating ligands on platelets may be responsible for evading the NK cell response. This study revealed the unique non-immunogenic property of platelets and provides a proof of concept for the clinical application of HLA-KO iPLATs.

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Clinically applicable iPSC-derived HLA class I knockout platelets (HLA-KO iPLATs)

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HLA-KO iPLATs do not elicit NK cell activation in vitro

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HLA-KO iPLATs circulate comparably with wild type in human NK cell-reconstituted mice

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HLA-KO iPLATs circulate competently in alloimmune PTR model mice

Genomic integrity of human induced pluripotent stem cells: Reprogramming, differentiation and applications

Ten years after the initial generation of induced pluripotent stem cells (hiPSCs) from human tissues, their potential is no longer questioned, with over 15000 publications listed on PubMed, covering various fields of research; including disease modeling, cell therapy strategies, pharmacology/toxicology screening and 3D organoid systems. However, despite evidences that the presence of mutations in hiPSCs should be a concern, publications addressing genomic integrity of these cells represent less than 1% of the literature. After a first overview of the mutation types currently reported in hiPSCs, including karyotype abnormalities, copy number variations, single point mutation as well as uniparental disomy, this review will discuss the impact of reprogramming parameters such as starting cell type and reprogramming method on the maintenance of the cellular genomic integrity. Then, a specific focus will be placed on culture conditions and subsequent differentiation protocols and how their may also trigger genomic aberrations within the cell population of interest. Finally, in a last section, the impact of genomic alterations on the possible usages of hiPSCs and their derivatives will also be exemplified and discussed. We will also discuss which techniques or combination of techniques should be used to screen for genomic abnormalities with a particular focus on the necessary quality controls and the potential alternatives.

Impact of Homozygous Conserved Extended HLA Haplotype on Single Cord Blood Transplantation: Lessons for Induced Pluripotent Stem Cell Banking and Transplantation in Allogeneic Settings

Induced pluripotent stem cells (iPSCs) have been applied to clinical regenerative cell therapy. Recently, an iPSC banking system to collect HLA haplotype (HP) homozygous (homo) cells for iPSC transplantation in allogeneic settings was proposed, and tissue transplantation generated from iPSC through banking has just began. We analyzed 5017 single cord blood transplantation (CBT) pairs with HLA-A, -B, -C, -DRB1 allele typing data and found 39 donor HLA homo donor to patient HLA heterozygous (hetero) pairs. Of note, all 39 HLA homo to hetero pairs engrafted neutrophils, except 1 early death pair, and all 30 assessable pairs engrafted platelets. Acute graft-versus-host disease (GVHD) grades II to IV and grades III to IV occurred in 17 and 3 of 38 assessable pairs, respectively. Competing risk regression analysis revealed a favorable risk of neutrophil engraftment and higher risk of acute GVHD compared with HLA-matched CBTs. Thirty-seven of 39 homo to hetero pairs had conserved extended HLA HPs (HP-1, n = 18; HP-2, n = 8; HP-3, n = 7; HP-4, n = 4; HP-5, n = 1) that were ethnicity-specific, and at least 1 of 2 patient HLA-A, -B, -C, and -DRB1 alleles in each locus were invariably shared with the same donor HP in 35 pairs. These findings confirmed our preliminary results with 6 HLA homo CBTs, and a trend of high incidence of acute GVHD was newly observed. Importantly, they imply the possibility that HLA-homo iPSC transplantation provides favorable engraftment and accordingly imply the merit of banking iPSC with homozygous major conserved extended HLA HPs.

Induced pluripotent stem cells, a giant leap for mankind therapeutic applications

Induced pluripotent stem cells (iPSC) technology has propelled the field of stem cells biology, providing new cells to explore the molecular mechanisms of pluripotency, cancer biology and aging. A major advantage of human iPSC, compared to the pluripotent embryonic stem cells, is that they can be generated from virtually any embryonic or adult somatic cell type without destruction of human blastocysts. In addition, iPSC can be generated from somatic cells harvested from normal individuals or patients, and used as a cellular tool to unravel mechanisms of human development and to model diseases in a manner not possible before. Besides these fundamental aspects of human biology and physiology that are revealed using iPSC or iPSC-derived cells, these cells hold an immense potential for cell-based therapies, and for the discovery of new or personalized pharmacological treatments for many disorders. Here, we review some of the current challenges and concerns about iPSC technology. We introduce the potential held by iPSC for research and development of novel health-related applications. We briefly present the efforts made by the scientific and clinical communities to create the necessary guidelines and regulations to achieve the highest quality standards in the procedures for iPSC generation, characterization and long-term preservation. Finally, we present some of the audacious and pioneer clinical trials in progress with iPSC-derived cells.

Induced Pluripotent Stem Cells and Their Use in Human Models of Disease and Development

The discovery of somatic cell nuclear transfer proved that somatic cells can carry the same genetic code as the zygote, and that activating parts of this code are sufficient to reprogram the cell to an early developmental state. The discovery of induced pluripotent stem cells (iPSCs) nearly half a century later provided a molecular mechanism for the reprogramming. The initial creation of iPSCs was accomplished by the ectopic expression of four specific genes (OCT4, KLF4, SOX2, and c-Myc; OSKM). iPSCs have since been acquired from a wide range of cell types and a wide range of species, suggesting a universal molecular mechanism. Furthermore, cells have been reprogrammed to iPSCs using a myriad of methods, although OSKM remains the gold standard. The sources for iPSCs are abundant compared with those for other pluripotent stem cells; thus the use of iPSCs to model the development of tissues, organs, and other systems of the body is increasing. iPSCs also, through the reprogramming of patient samples, are being used to model diseases. Moreover, in the 10 years since the first report, human iPSCs are already the basis for new cell therapies and drug discovery that have reached clinical application. In this review, we examine the generation of iPSCs and their application to disease and development.

Determination of HLA-A, -B, -C, -DRB1 and -DQB1 allele and haplotype frequencies in heart failure patients

Aims

Cell therapy can be used to repair functionally impaired organs and tissues in humans. Although autologous cells have an immunological advantage, it is difficult to obtain high cell numbers for therapy. Well‐characterized banks of cells with human leukocyte antigens (HLA) that are representative of a given population are thus needed. The present study investigates the HLA allele and haplotype frequencies in a cohort of heart failure (HF) patients.

Methods and results

We carried out the HLA typing and the allele and haplotype frequency analysis in 247 ambulatory HF patients. We determined HLA class I (A, B, and C) and class II (DRB1 and DQB1) using next‐generation sequencing technology. The allele frequencies were obtained using Python for Population Genomics (PyPop) software, and HLA haplotypes were estimated using HaploStats. A total of 30 HLA‐A, 56 HLA‐B, 23 HLA‐C, 36 HLA‐DRB1, and 15 HLA‐DQB1 distinct alleles were identified within the studied cohort. The genotype frequencies of all five HLA loci were in Hardy–Weinberg equilibrium. We detected differences in HLA allele frequencies among patients when the etiological cause of HF was considered. There were a total of 494 five‐loci haplotypes, five of which were present six or more times. Moreover, the most common estimated HLA haplotype was HLA‐A*01:01, HLA‐B*08:01, HLA‐C*07:01, HLA‐DRB1*03:01, and HLA‐DQB1*02:01 (6.07% haplotype frequency per patient). Remarkably, the 11 most frequent haplotypes would cover 31.17% of the patients of the cohort in need of allogeneic cell therapy.

Conclusions

Our findings could be useful for improving allogeneic cell administration outcomes without concomitant immunosuppression.

Immunological Considerations for Retinal Stem Cell Therapy

There is an increasing effort toward generating replacement cells for neuronal application due to the nonregenerative nature of these tissues. While much progress has been made toward developing methodologies to generate these cells, there have been limited improvements in functional restoration. Some of these are linked to the degenerative and often nonreceptive microenvironment that the new cells need to integrate into. In this chapter, we will focus on the status and role of the immune microenvironment of the retina during homeostasis and disease states. We will review changes in both innate and adaptive immunity as well as the role of immune rejection in stem cell replacement therapies. The chapter will end with a discussion of immune-modulatory strategies that have helped to ameliorate these effects and could potentially improve functional outcome for cell replacement therapies for the eye.