Insertional oncogenesis in 4 patients after retrovirus-mediated gene therapy of SCID-X1

Gene therapy in preeclampsia: the dawn of a new era

Preeclampsia is a severe complication of pregnancy, affecting an estimated 4 million women annually. It is one of the leading causes of maternal and fetal mortality worldwide, and it has life-long consequences. The maternal multisystemic symptoms are driven by poor placentation, which causes syncytiotrophoblastic stress and the release of factors into the maternal bloodstream. Amongst them, the soluble fms-like tyrosine kinase-1 (sFLT-1) triggers extensive endothelial dysfunction by acting as a decoy receptor for the vascular endothelial growth factor (VEGF) and the placental growth factor (PGF). Current interventions aim to mitigate hypertension and seizures, but the only definite treatment remains induced delivery. Thus, there is a pressing need for novel therapies to remedy this situation. Notably, CBP-4888, a siRNA drug delivered subcutaneously to knock down sFLT1 expression in the placenta, has recently obtained Fast Track approval from the Food and Drug Administration (FDA) and is undergoing a phase 1 clinical trial. Such advance highlights a growing interest and significant potential in gene therapy to manage preeclampsia. This review summarizes the advances and prospects of gene therapy in treating placental dysfunction and illustrates crucial challenges and considerations for these emerging treatments.

Personalized mRNA vaccines in glioblastoma therapy: from rational design to clinical trials

Glioblastomas (GBMs) are the most common and aggressive malignant brain tumors, presenting significant challenges for treatment due to their invasive nature and localization in critical brain regions. Standard treatment includes surgical resection followed by radiation and adjuvant chemotherapy with temozolomide (TMZ). Recent advances in immunotherapy, including the use of mRNA vaccines, offer promising alternatives. This review focuses on the emerging use of mRNA vaccines for GBM treatment. We summarize recent advancements, evaluate current obstacles, and discuss notable successes in this field. Our analysis highlights that while mRNA vaccines have shown potential, their use in GBM treatment is still experimental. Ongoing research and clinical trials are essential to fully understand their therapeutic potential. Future developments in mRNA vaccine technology and insights into GBM-specific immune responses may lead to more targeted and effective treatments. Despite the promise, further research is crucial to validate and optimize the effectiveness of mRNA vaccines in combating GBM.

CAR-T and CAR-NK as cellular cancer immunotherapy for solid tumors

In the past decade, chimeric antigen receptor (CAR)-T cell therapy has emerged as a promising immunotherapeutic approach for combating cancers, demonstrating remarkable efficacy in relapsed/refractory hematological malignancies in both pediatric and adult patients. CAR-natural killer (CAR-NK) cell complements CAR-T cell therapy by offering several distinct advantages. CAR-NK cells do not require HLA compatibility and exhibit low safety concerns. Moreover, CAR-NK cells are conducive to "off-the-shelf" therapeutics, providing significant logistic advantages over CAR-T cells. Both CAR-T and CAR-NK cells have shown consistent and promising results in hematological malignancies. However, their efficacy against solid tumors remains limited due to various obstacles including limited tumor trafficking and infiltration, as well as an immuno-suppressive tumor microenvironment. In this review, we discuss the recent advances and current challenges of CAR-T and CAR-NK cell immunotherapies, with a specific focus on the obstacles to their application in solid tumors. We also analyze in depth the advantages and drawbacks of CAR-NK cells compared to CAR-T cells and highlight CAR-NK CAR optimization. Finally, we explore future perspectives of these adoptive immunotherapies, highlighting the increasing contribution of cutting-edge biotechnological tools in shaping the next generation of cellular immunotherapy.

Genome Editing Therapy for the Blood: Ex Vivo Success and In Vivo Prospects

Hematopoietic stem cells (HSCs) provide the body with a continuous supply of healthy, functional blood cells. In patients with hematopoietic malignancies, immunodeficiencies, lysosomal storage disorders, and hemoglobinopathies, therapeutic genome editing offers hope for corrective intervention, with even modest editing efficiencies likely to provide clinical benefit. Engineered white blood cells, such as T cells, can be applied therapeutically to address monogenic disorders of the immune system, HIV infection, or cancer. The versatility of CRISPR-based tools allows countless new medical interventions for diseases of the blood, and rapid ex vivo success has been demonstrated in hemoglobinopathies via transplantation of the patient's HSCs following genome editing in a laboratory setting. Here we review recent advances in therapeutic genome editing of HSCs and T cells, focusing on the progress in ex vivo contexts, the promise of improved access via in vivo delivery, as well as the ongoing preclinical efforts that may enable the transition from ex vivo to in vivo administration. We discuss the challenges, limitations, and future prospects of this rapidly developing field, which may one day establish CRISPR as the standard of care for some diseases affecting the blood.

Genotoxicity evaluation of gene therapies: A report from the International Workshop on Genotoxicity Testing (IWGT) 2022

At the 8th International Workshop on Genotoxicity Testing meeting in Ottawa, in August 2022, a plenary session was dedicated to the genotoxicity risk evaluation of gene therapies, including insertional oncogenesis and off-target genome editing. This brief communication summarizes the topics of discussion and the main insights from the speakers. Common themes included recommendations to conduct tailored risk assessments based on a weight-of-evidence approach, to promote data sharing, transparency, and cooperation between stakeholders, and to develop state-of-the-art validated tests relevant to clinical scenarios.

Gene Therapy Strategies for RAG1 Deficiency: Challenges and Breakthroughs

Mutations in the recombination activating genes (RAG) cause various forms of immune deficiency. Hematopoietic stem cell transplant (HSCT) is the only cure for patients with severe manifestations of RAG deficiency; however, outcomes are suboptimal with mismatched donors. Gene therapy aims to correct autologous hematopoietic stem and progenitor cells (HSPC) and is emerging as an alternative to allogeneic HSCT. Gene therapy based on viral gene addition exploits viral vectors to add a correct copy of a mutated gene into the genome of HSPCs. Only recently, after a prolonged phase of development, viral gene addition has been approved for clinical testing in RAG1-SCID patients. In the meantime, a new technology, CRISPR/Cas9, has made its debut to compete with viral gene addition. Gene editing based on CRISPR/Cas9 allows to perform targeted genomic integrations of a correct copy of a mutated gene, circumventing the risk of virus-mediated insertional mutagenesis. In this review, we present the biology of the RAG genes, the challenges faced during the development of viral gene addition for RAG1-SCID, and the current status of gene therapy for RAG1 deficiency. In particular, we highlight the latest advances and challenges in CRISPR/Cas9 gene editing and their potential for the future of gene therapy.

The longitudinal kinetics of AAV5 vector integration profiles and evaluation of clonal expansion in mice

Adeno-associated virus (AAV)-based vectors are used clinically for gene transfer and persist as extrachromosomal episomes. A small fraction of vector genomes integrate into the host genome, but the theoretical risk of tumorigenesis depends on vector regulatory features. A mouse model was used to investigate integration profiles of an AAV serotype 5 (AAV5) vector produced using Sf and HEK293 cells that mimic key features of valoctocogene roxaparvovec (AAV5-hFVIII-SQ), a gene therapy for severe hemophilia A. The majority (95%) of vector genome reads were derived from episomes, and mean (± standard deviation) integration frequency was 2.70 ± 1.26 and 1.79 ± 0.86 integrations per 1,000 cells for Sf- and HEK293-produced vector. Longitudinal integration analysis suggested integrations occur primarily within 1 week, at low frequency, and their abundance was stable over time. Integration profiles were polyclonal and randomly distributed. No major differences in integration profiles were observed for either vector production platform, and no integrations were associated with clonal expansion. Integrations were enriched near transcription start sites of genes highly expressed in the liver (p = 1 × 10-4) and less enriched for genes of lower expression. We found no evidence of tumorigenesis or fibrosis caused by the vector integrations.

The role of the conditioning regimen for autologous and ex vivo genetically modified hematopoietic stem cell-based therapies: recommendations from the ISCT stem cell engineering committee

BACKGROUND

The advent of autologous gene modified cell therapies to treat monogenic disorders has been a major step forward for the field of hematopoietic stem cell transplantation (HCT) and cellular therapies. The need for disease-specific conditioning to enable these products to provide a potential cure has required extrapolation from experience in myeloablative and non-myeloablative HCT for these disorders.

METHODS

In this manuscript, we review the current datasets and clinical experience using different conditioning regimens for autologous gene therapies in hemoglobinopathies, metabolic and lysosomal disorders, inborn errors of immunity (IEI) and bone marrow failure (BMF) syndromes.

RESULTS

The disease specific and unique conditioning requirements of each disorder are considered in order to achieve maximal benefit while minimizing associated toxicities.

CONCLUSIONS

Standardized recommendations based on these data are made for each set of disorders to harmonize treatment. Future directions and the possibility of non-genotoxic conditioning regimens for autologous gene therapies are also discussed. Ethical Statement: The authors followed all relevant ethical considerations in writing this manuscript.

Adeno-Associated Virus Vectors-a Target of Cellular and Humoral Immunity-are Expanding Their Reach Toward Hematopoietic Stem Cell Modification and Immunotherapies

All current market-approved gene therapy medical products for in vivo gene therapy of monogenic diseases rely on adeno-associated virus (AAV) vectors. Advances in gene editing technologies and vector engineering have expanded the spectrum of target cells and, thus, diseases that can be addressed. Consequently, AAV vectors are now being explored to modify cells of the hematopoietic system, including hematopoietic stem and progenitor cells (HSPCs), to develop novel strategies to treat monogenic diseases, but also to generate cell- and vaccine-based immunotherapies. However, the cell types that represent important new targets for the AAV vector system are centrally involved in immune responses against the vector and its transgene product as discussed briefly in the first part of this review. In the second part, studies exploring AAV vectors for genetic engineering of HSPCs, T and B lymphocytes, and beyond are presented.

The menace of severe adverse events and deaths associated with viral gene therapy and its potential solution

Over the past decade, in vivo gene replacement therapy has significantly advanced, resulting in market approval of numerous therapeutics predominantly relying on adeno-associated viral vectors (AAV). While viral vectors have undeniably addressed several critical healthcare challenges, their clinical application has unveiled a range of limitations and safety concerns. This review highlights the emerging challenges in the field of gene therapy. At first, we discuss both the role of biological barriers in viral gene therapy with a focus on AAVs, and review current landscape of in vivo human gene therapy. We delineate advantages and disadvantages of AAVs as gene delivery vehicles, mostly from the safety perspective (hepatotoxicity, cardiotoxicity, neurotoxicity, inflammatory responses etc.), and outline the mechanisms of adverse events in response to AAV. Contribution of every aspect of AAV vectors (genomic structure, capsid proteins) and host responses to injected AAV is considered and substantiated by basic, translational and clinical studies. The updated evaluation of recent AAV clinical trials and current medical experience clearly shows the risks of AAVs that sometimes overshadow the hopes for curing a hereditary disease. At last, a set of established and new molecular and nanotechnology tools and approaches are provided as potential solutions for mitigating or eliminating side effects. The increasing number of severe adverse reactions and, sadly deaths, demands decisive actions to resolve the issue of immune responses and extremely high doses of viral vectors used for gene therapy. In response to these challenges, various strategies are under development, including approaches aimed at augmenting characteristics of viral vectors and others focused on creating secure and efficacious non-viral vectors. This comprehensive review offers an overarching perspective on the present state of gene therapy utilizing both viral and non-viral vectors.

Enhancing cellular immunotherapies in cancer by engineering selective therapeutic resistance

Adoptive cell therapies engineered to express chimeric antigen receptors (CARs) or transgenic T cell receptors (TCRs) to recognize and eliminate cancer cells have emerged as a promising approach for achieving long-term remissions in patients with cancer. To be effective, the engineered cells must persist at therapeutically relevant levels while avoiding off-tumour toxicities, which has been challenging to realize outside of B cell and plasma cell malignancies. This Review discusses concepts to enhance the efficacy, safety and accessibility of cellular immunotherapies by endowing cells with selective resistance to small-molecule drugs or antibody-based therapies to facilitate combination therapies with substances that would otherwise interfere with the functionality of the effector cells. We further explore the utility of engineering healthy haematopoietic stem cells to confer resistance to antigen-directed immunotherapies and small-molecule targeted therapies to expand the therapeutic index of said targeted anticancer agents as well as to facilitate in vivo selection of gene-edited haematopoietic stem cells for non-malignant applications. Lastly, we discuss approaches to evade immune rejection, which may be required in the setting of allogeneic cell therapies. Increasing confidence in the tools and outcomes of genetically modified cell therapy now paves the way for rational combinations that will open new therapeutic horizons.

Engineered IRES-mediated promoter-free insulin-producing cells reverse hyperglycemia

Background

Endogenous insulin supplementation is essential for individuals with type 1 diabetes (T1D). However, current treatments, including pancreas transplantation, insulin injections, and oral medications, have significant limitations. The development of engineered cells that can secrete endogenous insulin offers a promising new therapeutic strategy for type 1 diabetes (T1D). This approach could potentially circumvent autoimmune responses associated with the transplantation of differentiated β-cells or systemic delivery of viral vectors.

Methods

We utilized CRISPR/Cas9 gene editing coupled with homology-directed repair (HDR) to precisely integrate a promoter-free EMCVIRES-insulin cassette into the 3' untranslated region (UTR) of the GAPDH gene in human HEK-293T cells. Subsequently quantified insulin expression levels in these engineered cells, the viability and functionality of the engineered cells when seeded on different cell vectors (GelMA and Cytopore I) were also assessed. Finally, we investigated the therapeutic potential of EMCVIRES-based insulin secretion circuits in reversing Hyperglycaemia in T1D mice.

Result

Our results demonstrate that HDR-mediated gene editing successfully integrated the IRES-insulin loop into the genome of HEK-293T cells, a non-endocrine cell line, enabling the expression of human-derived insulin. Furthermore, Cytopore I microcarriers facilitated cell attachment and proliferation during in vitro culture and enhanced cell survival post-transplantation. Transplantation of these cell-laden microcarriers into mice led to the development of a stable, fat-encapsulated structure. This structure exhibited the expression of the platelet-endothelial cell adhesion molecule CD31, and no significant immune rejection was observed throughout the experiment. Diabetic mice that received the cell carriers reversed hyperglycemia, and blood glucose fluctuations under simulated feeding stimuli were very similar to those of healthy mice.

Conclusion

In summary, our study demonstrates that Cytopore I microcarriers are biocompatible and promote long-term cell survival in vivo. The promoter-free EMCVIRES-insulin loop enables non-endocrine cells to secrete mature insulin, leading to a rapid reduction in glucose levels. We have presented a novel promoter-free genetic engineering strategy for insulin secretion and proposed an efficient cell transplantation method. Our findings suggest the potential to expand the range of cell sources available for the treatment of diabetes, offering new avenues for therapeutic interventions.

Targeting multiple hallmarks of mammalian aging with combinations of interventions

Aging is currently viewed as a result of multiple biological processes that manifest themselves independently, reinforce each other and in their totality lead to the aged phenotype. Genetic and pharmaceutical approaches targeting specific underlying causes of aging have been used to extend the lifespan and healthspan of model organisms ranging from yeast to mammals. However, most interventions display only a modest benefit. This outcome is to be expected if we consider that even if one aging process is successfully treated, other aging pathways may remain intact. Hence solving the problem of aging may require targeting not one but many of its underlying causes at once. Here we review the challenges and successes of combination therapies aimed at increasing the lifespan of mammals and propose novel directions for their development. We conclude that both additive and synergistic effects on mammalian lifespan can be achieved by combining interventions that target the same or different hallmarks of aging. However, the number of studies in which multiple hallmarks were targeted simultaneously is surprisingly limited. We argue that this approach is as promising as it is understudied.

Preclinical evidence in the assembly of mammalian SWI/SNF complexes: Epigenetic insights and clinical perspectives in human lung disease therapy

The SWI/SNF complex, also known as the BRG1/BRM-associated factor (BAF) complex, represents a critical regulator of chromatin remodeling mechanisms in mammals. It is alternatively referred to as mSWI/SNF and has been suggested to be imbalanced in human disease compared with human health. Three types of BAF assemblies associated with it have been described, including (1) canonical BAF (cBAF), (2) polybromo-associated BAF (PBAF), and (3) non-canonical BAF (ncBAF) complexes. Each of these BAF assemblies plays a role, either functional or dysfunctional, in governing gene expression patterns, cellular processes, epigenetic mechanisms, and biological processes. Recent evidence increasingly links the dysregulation of mSWI/SNF complexes to various human non-malignant lung chronic disorders and lung malignant diseases. This review aims to provide a comprehensive general state-of-the-art and a profound examination of the current understanding of mSWI/SNF assembly processes, as well as the structural and functional organization of mSWI/SNF complexes and their subunits. In addition, it explores their intricate functional connections with potentially dysregulated transcription factors, placing particular emphasis on molecular and cellular pathogenic processes in lung diseases. These processes are reflected in human epigenome aberrations that impact clinical and therapeutic levels, suggesting novel perspectives on the diagnosis and molecular therapies for human respiratory diseases.

Vaccine delivery systems and administration routes: Advanced biotechnological techniques to improve the immunization efficacy

Since the first use of vaccine tell the last COVID-19 pandemic caused by spread of SARS-CoV-2 worldwide, the use of advanced biotechnological techniques has accelerated the development of different types and methods for immunization. The last pandemic showed that the nucleic acid-based vaccine, especially mRNA, has an advantage in terms of development time; however, it showed a very critical drawback namely, the higher costs when compared to other strategies, and its inability to protect against new variants. This showed the need of more improvement to reach a better delivery and efficacy. In this review we will describe different vaccine delivery systems including, the most used viral vector, and also variable strategies for delivering of nucleic acid-based vaccines especially lipid-based nanoparticles formulation, polymersomes, electroporation and also the new powerful tools for the delivery of mRNA, which is based on the use of cell-penetrating peptides (CPPs). Additionally, we will also discuss the main challenges associated with each system. Finlay, the efficacy and safety of the vaccines depends not only on the formulations and delivery systems, but also the dosage and route of administration are also important players, therefore we will see the different routes for the vaccine administration including traditionally routes (intramuscular, Transdermal, subcutaneous), oral inhalation or via nasal mucosa, and will describe the advantages and disadvantage of each administration route.

Current and emerging drug treatment strategies to tackle sickle cell anemia

INTRODUCTION

Since its discovery in the early 1900s, sickle cell disease (SCD) has contributed significantly to the scientific understanding of hemoglobin and hemoglobinopathies. Despite this, now almost a century later, optimal medical management and even curative options remain limited. Encouragingly, in the last decade, there has been a push toward advancing the care for individuals with SCD and a diversifying interest in options to manage this disorder.

AREAS COVERED

Here, we review the current state of disease modifying therapies for SCD including fetal hemoglobin inducers, monoclonal antibodies, anti-inflammatory modulators, and enzyme activators. We also discuss current curative strategies with specific interest in transformative gene therapies.

EXPERT OPINION

SCD is a chronic, progressive disease that despite a century of clinical description, only now is seeing a growth and advance in therapeutic options to improve the lifespan and quality of life for individuals with SCD. We anticipate newly designed and even repurposed therapies that may work as a single agent or combination agents to tackle the progression of SCD. The vast majority of individuals living with SCD are unlikely to receive gene therapy, therefore improved disease management is critical even for those that may ultimately chose to pursue a potentially curative strategy.

Scalable intracellular delivery via microfluidic vortex shedding enhances the function of chimeric antigen receptor T-cells

Adoptive chimeric antigen receptor T-cell (CAR-T) therapy is transformative and approved for hematologic malignancies. It is also being developed for the treatment of solid tumors, autoimmune disorders, heart disease, and aging. Despite unprecedented clinical outcomes, CAR-T and other engineered cell therapies face a variety of manufacturing and safety challenges. Traditional methods, such as lentivirus transduction and electroporation, result in random integration or cause significant cellular damage, which can limit the safety and efficacy of engineered cell therapies. We present hydroporation as a gentle and effective alternative for intracellular delivery. Hydroporation resulted in 1.7- to 2-fold higher CAR-T yields compared to electroporation with superior cell viability and recovery. Hydroporated cells exhibited rapid proliferation, robust target cell lysis, and increased pro-inflammatory and regulatory cytokine secretion in addition to improved CAR-T yield by day 5 post-transfection. We demonstrate that scaled-up hydroporation can process 5 x 108 cells in less than 10 s, showcasing the platform as a viable solution for high-yield CAR-T manufacturing with the potential for improved therapeutic outcomes.

Role of Neurotransmitters in Steady State Hematopoiesis, Aging, and Leukemia

Haematopoiesis within the bone marrow (BM) represents a complex and dynamic process intricately regulated by neural signaling pathways. This delicate orchestration is susceptible to disruption by factors such as aging, diabetes, and obesity, which can impair the BM niche and consequently affect haematopoiesis. Genetic mutations in Tet2, Dnmt3a, Asxl1, and Jak2 are known to give rise to clonal haematopoiesis of intermediate potential (CHIP), a condition linked to age-related haematological malignancies. Despite these insights, the exact roles of circadian rhythms, sphingosine-1-phosphate (S1P), stromal cell-derived factor-1 (SDF-1), sterile inflammation, and the complement cascade on various BM niche cells remain inadequately understood. Further research is needed to elucidate how BM niche cells contribute to these malignancies through neural regulation and their potential in the development of gene-corrected stem cells. This literature review describes the updated functional aspects of BM niche cells in haematopoiesis within the context of haematological malignancies, with a particular focus on neural signaling and the potential of radiomitigators in acute radiation syndrome. Additionally, it underscores the pressing need for technological advancements in stem cell-based therapies to alleviate the impacts of immunological stressors. Recent studies have illuminated the microheterogeneity and temporal stochasticity of niche cells within the BM during haematopoiesis, emphasizing the updated roles of neural signaling and immunosurveillance. The development of gene-corrected stem cells capable of producing blood, immune cells, and tissue-resident progeny is essential for combating age-related haematological malignancies and overcoming immunological challenges. This review aims to provide a comprehensive overview of these evolving insights and their implications for future therapeutic strategies.

Preclinical safety assessment of modified gamma globin lentiviral vector-mediated autologous hematopoietic stem cell gene therapy for hemoglobinopathies

Previously, we reported the development of a human Aγ-globin gene lentivirus (LV), GbG, which expresses high levels of HbF to correct the sickle cell anemia (SCA) phenotype in the Berkeley SCA mouse model, and then modified the γ-globin gene by substituting glycine at codon 16 with aspartic acid in the Aγ-globin gene to generate GbGM LV. In the present study, we evaluated the long-term safety of human Aγ-globin gene carrying GbGM LV in wild-type mice after primary and secondary transplants of GbGM-modified hematopoietic stem cells (HSC) over 18 months. The safety of the GbGM bone marrow transplant was assessed by monitoring the effects on body weight, hematology, histopathology, malignancy formation, and survival. Mice transplanted with Mock-transduced and spleen focus forming virus (SFFV) γ-retroviral vector (RV)-transduced HSC served as negative and positive controls, respectively. The mean donor-cell engraftment was comparable across Mock, GbGM LV, and SFFV RV groups. There were no significant differences in body weight, clinical signs, immunophenotype, or histopathology in the GbGM-treated mice compared to controls. Four SFFV RV-treated mice, but none of the GbGM-treated mice, developed donor-derived, vector-positive lymphomas as demonstrated by flow cytometry analysis and in situ hybridization. These results highlight the safety of the administration of GbGM LV-modified HSC with long-term follow-up after primary and secondary transplants in mice. This data supported the initiation of phase 1/2 first-in-human SCA clinical trial in the United States.

Gene therapy for the leukodystrophies: From preclinical animal studies to clinical trials

Leukodystrophies are progressive single gene disorders affecting the white matter of the brain. Several gene therapy trials are in progress to address the urgent unmet need for this patient population. We performed a comprehensive literature review of all gene therapy clinical trials listed in www.clinicaltrials.gov through August 2024, and the relevant preclinical studies that enabled clinical translation. Of the approximately 50 leukodystrophies described to date, only eight have existing gene therapy clinical trials: metachromatic leukodystrophy, X-linked adrenoleukodystrophy, globoid cell leukodystrophy, Canavan disease, giant axonal neuropathy, GM2 gangliosidoses, Alexander disease and Pelizaeus-Merzbacher disease. What led to the emergence of gene therapy trials for these specific disorders? What preclinical data or disease context was enabling? For each of these eight disorders, we first describe its pathophysiology and clinical presentation. We discuss the impact of gene therapy delivery route, targeted cell type, delivery modality, dosage, and timing on therapeutic efficacy. We note that use of allogeneic hematopoietic stem cell transplantation in some leukodystrophies allowed for an accelerated path to clinic even in the absence of available animal models. In other leukodystrophies, small and large animal model studies enabled clinical translation of experimental gene therapies. Human clinical trials for the leukodystrophies include ex vivo lentiviral gene delivery, in vivo AAV-mediated gene delivery, and intrathecal antisense oligonucleotide approaches. We outline adverse events associated with each modality focusing specifically on genotoxicity and immunotoxicity. We review monitoring and management of events related to insertional mutagenesis and immune responses. The data presented in this review show that gene therapy, while promising, requires systematic monitoring to account for the precarious disease biology and the adverse events associated with new technology.

Gene therapy in pediatrics - Clinical studies and approved drugs (as of 2023)

Gene therapy in pediatrics represents a cutting-edge therapeutic strategy for treating a range of genetic disorders that manifest in childhood. Gene therapy involves the modification or correction of a mutated gene or the introduction of a functional gene into a patient's cells. In general, it is implemented through two main modalities namely ex vivo gene therapy and in vivo gene therapy. Currently, a noteworthy array of gene therapy products has received valid market authorization, with several others in various stages of the approval process. Additionally, a multitude of clinical trials are actively underway, underscoring the dynamic progress within this field. Pediatric genetic disorders in the fields of hematology, oncology, vision and hearing loss, immunodeficiencies, neurological, and metabolic disorders are areas for gene therapy interventions. This review provides a comprehensive overview of the evolution and current progress of gene therapy-based treatments in the clinic for pediatric patients. It navigates the historical milestones of gene therapies, currently approved gene therapy products by the U.S. Food and Drug Administration (FDA) and/or European Medicines Agency (EMA) for children, and the promising future for genetic disorders. By providing a thorough compilation of approved gene therapy drugs and published results of completed or ongoing clinical trials, this review serves as a guide for pediatric clinicians to get a quick overview of the situation of clinical studies and approved gene therapy products as of 2023.

Precise Gene Knock-In Tools with Minimized Risk of DSBs: A Trend for Gene Manipulation

Gene knock-in refers to the insertion of exogenous functional genes into a target genome to achieve continuous expression. Currently, most knock-in tools are based on site-directed nucleases, which can induce double-strand breaks (DSBs) at the target, following which the designed donors carrying functional genes can be inserted via the endogenous gene repair pathway. The size of donor genes is limited by the characteristics of gene repair, and the DSBs induce risks like genotoxicity. New generation tools, such as prime editing, transposase, and integrase, can insert larger gene fragments while minimizing or eliminating the risk of DSBs, opening new avenues in the development of animal models and gene therapy. However, the elimination of off-target events and the production of delivery carriers with precise requirements remain challenging, restricting the application of the current knock-in treatments to mainly in vitro settings. Here, a comprehensive review of the knock-in tools that do not/minimally rely on DSBs and use other mechanisms is provided. Moreover, the challenges and recent advances of in vivo knock-in treatments in terms of the therapeutic process is discussed. Collectively, the new generation of DSBs-minimizing and large-fragment knock-in tools has revolutionized the field of gene editing, from basic research to clinical treatment.

The paths toward non-viral CAR-T cell manufacturing: A comprehensive review of state-of-the-art methods

Although CAR-T cell therapy has emerged as a game-changer in cancer immunotherapy several bottlenecks limit its widespread use as a front-line therapy. Current protocols for the production of CAR-T cells rely mainly on the use of lentiviral/retroviral vectors. Nevertheless, according to the safety concerns around the use of viral vectors, there are several regulatory hurdles to their clinical use. Large-scale production of viral vectors under "Current Good Manufacturing Practice" (cGMP) involves rigorous quality control assessments and regulatory requirements that impose exorbitant costs on suppliers and as a result, lead to a significant increase in the cost of treatment. Pursuing an efficient non-viral method for genetic modification of immune cells is a hot topic in cell-based gene therapy. This study aims to investigate the current state-of-the-art in non-viral methods of CAR-T cell manufacturing. In the first part of this study, after reviewing the advantages and disadvantages of the clinical use of viral vectors, different non-viral vectors and the path of their clinical translation are discussed. These vectors include transposons (sleeping beauty, piggyBac, Tol2, and Tc Buster), programmable nucleases (ZFNs, TALENs, and CRISPR/Cas9), mRNA, plasmids, minicircles, and nanoplasmids. Afterward, various methods for efficient delivery of non-viral vectors into the cells are reviewed.

Enhancing pediatric access to cell and gene therapies

Increasing numbers of cell and gene therapies (CGTs) are emerging to treat and cure pediatric diseases. However, small market sizes limit the potential return on investment within the traditional biopharmaceutical drug development model, leading to a market failure. In this Perspective, we discuss major factors contributing to this failure, including high manufacturing costs, regulatory challenges, and licensing practices that do not incorporate pediatric development milestones, as well as potential solutions. We propose the creation of a new entity, the Pediatric Advanced Medicines Biotech, to lead late-stage development and commercialize pediatric CGTs outside the traditional biopharmaceutical model in the United States-where organized efforts to solve this problem have been lacking. The Pediatric Advanced Medicines Biotech would partner with the academic ecosystem, manufacture products in academic good manufacturing practice facilities and work closely with regulatory bodies, to ferry CGTs across the drug development 'valley of death' and, ultimately, increase access to lifesaving treatments for children in need.

Enhancement of erythropoietic output by Cas9-mediated insertion of a natural variant in haematopoietic stem and progenitor cells

Some gene polymorphisms can lead to monogenic diseases, whereas other polymorphisms may confer beneficial traits. A well-characterized example is congenital erythrocytosis-the non-pathogenic hyper-production of red blood cells-that is caused by a truncated erythropoietin receptor. Here we show that Cas9-mediated genome editing in CD34+ human haematopoietic stem and progenitor cells (HSPCs) can recreate the truncated form of the erythropoietin receptor, leading to substantial increases in erythropoietic output. We also show that combining the expression of the cDNA of a truncated erythropoietin receptor with a previously reported genome-editing strategy to fully replace the HBA1 gene with an HBB transgene in HSPCs (to restore normal haemoglobin production in cells with a β-thalassaemia phenotype) gives the edited HSPCs and the healthy red blood cell phenotype a proliferative advantage. Combining knowledge of human genetics with precise genome editing to insert natural human variants into therapeutic cells may facilitate safer and more effective genome-editing therapies for patients with genetic diseases.

Advancements in Hematopoietic Stem Cell Gene Therapy: A Journey of Progress for Viral Transduction

Hematopoietic stem cell (HSC) transduction has undergone remarkable advancements in recent years, revolutionizing the landscape of gene therapy specifically for inherited hematologic disorders. The evolution of viral vector-based transduction technologies, including retroviral and lentiviral vectors, has significantly enhanced the efficiency and specificity of gene delivery to HSCs. Additionally, the emergence of small molecules acting as transduction enhancers has addressed critical barriers in HSC transduction, unlocking new possibilities for therapeutic intervention. Furthermore, the advent of gene editing technologies, notably CRISPR-Cas9, has empowered precise genome modification in HSCs, paving the way for targeted gene correction. These striking progresses have led to the clinical approval of medicinal products based on engineered HSCs with impressive therapeutic benefits for patients. This review provides a comprehensive overview of the collective progress in HSC transduction via viral vectors for gene therapy with a specific focus on transduction enhancers, highlighting the latest key developments, challenges, and future directions towards personalized and curative treatments.

Mechanisms Underlying the Development of Murine T-Cell Lymphoblastic Lymphoma/Leukemia Induced by Total-Body Irradiation

Exposure to ionizing radiation is associated with an increased risk of hematologic malignancies in myeloid and lymphoid lineages in humans and experimental mice. Given that substantial evidence links radiation exposure with the risk of hematologic malignancies, it is imperative to deeply understand the mechanisms underlying cellular and molecular changes during the latency period between radiation exposure and the emergence of fully transformed malignant cells. One experimental model widely used in the field of radiation and cancer biology to study hematologic malignancies induced by radiation exposure is mouse models of radiation-induced thymic lymphoma. Murine radiation-induced thymic lymphoma is primarily driven by aberrant activation of Notch signaling, which occurs frequently in human precursor T-cell lymphoblastic lymphoma (T-LBL) and T-cell lymphoblastic leukemia (T-ALL). Here, we summarize the literature elucidating cell-autonomous and non-cell-autonomous mechanisms underlying cancer initiation, progression, and malignant transformation in the thymus following total-body irradiation (TBI) in mice.

Risk of Second Tumors and T-Cell Lymphoma after CAR T-Cell Therapy

BACKGROUND

The risk of second tumors after chimeric antigen receptor (CAR) T-cell therapy, especially the risk of T-cell neoplasms related to viral vector integration, is an emerging concern.

METHODS

We reviewed our clinical experience with adoptive cellular CAR T-cell therapy at our institution since 2016 and ascertained the occurrence of second tumors. In one case of secondary T-cell lymphoma, a broad array of molecular, genetic, and cellular techniques were used to interrogate the tumor, the CAR T cells, and the normal hematopoietic cells in the patient.

RESULTS

A total of 724 patients who had received T-cell therapies at our center were included in the study. A lethal T-cell lymphoma was identified in a patient who had received axicabtagene ciloleucel therapy for diffuse large B-cell lymphoma, and both lymphomas were deeply profiled. Each lymphoma had molecularly distinct immunophenotypes and genomic profiles, but both were positive for Epstein-Barr virus and were associated with DNMT3A and TET2 mutant clonal hematopoiesis. No evidence of oncogenic retroviral integration was found with the use of multiple techniques.

CONCLUSIONS

Our results highlight the rarity of second tumors and provide a framework for defining clonal relationships and viral vector monitoring. (Funded by the National Cancer Institute and others.).

Prenatal AAV9-GFP administration in fetal lambs results in transduction of female germ cells and maternal exposure to virus

Prenatal somatic cell gene therapy (PSCGT) could potentially treat severe, early-onset genetic disorders such as spinal muscular atrophy (SMA) or muscular dystrophy. Given the approval of adeno-associated virus serotype 9 (AAV9) vectors in infants with SMA by the U.S. Food and Drug Administration, we tested the safety and biodistribution of AAV9-GFP (clinical-grade and dose) in fetal lambs to understand safety and efficacy after umbilical vein or intracranial injection on embryonic day 75 (E75) . Umbilical vein injection led to widespread biodistribution of vector genomes in all examined lamb tissues and in maternal uteruses at harvest (E96 or E140; term = E150). There was robust GFP expression in brain, spinal cord, dorsal root ganglia (DRGs), without DRG toxicity and excellent transduction of diaphragm and quadriceps muscles. However, we found evidence of systemic toxicity (fetal growth restriction) and maternal exposure to the viral vector (transient elevation of total bilirubin and a trend toward elevation in anti-AAV9 antibodies). There were no antibodies against GFP in ewes or lambs. Analysis of fetal gonads demonstrated GFP expression in female (but not male) germ cells, with low levels of integration-specific reads, without integration in select proto-oncogenes. These results suggest potential therapeutic benefit of AAV9 PSCGT for neuromuscular disorders, but warrant caution for exposure of female germ cells.

Vector integration and fate in the hemophilia dog liver multiple years after AAV-FVIII gene transfer

ABSTRACT

Gene therapy using adeno-associated virus (AAV) vectors is a promising approach for the treatment of monogenic disorders. Long-term multiyear transgene expression has been demonstrated in animal models and clinical studies. Nevertheless, uncertainties remain concerning the nature of AAV vector persistence and whether there is a potential for genotoxicity. Here, we describe the mechanisms of AAV vector persistence in the liver of a severe hemophilia A dog model (male = 4, hemizygous; and female = 4, homozygous), more than a decade after portal vein delivery. The predominant vector form was nonintegrated episomal structures with levels correlating with long-term transgene expression. Random integration was seen in all samples (median frequency, 9.3e-4 sites per cell), with small numbers of nonrandom common integration sites associated with open chromatin. No full-length integrated vectors were found, supporting predominant episomal vector-mediated long-term transgene expression. Despite integration, this was not associated with oncogene upregulation or histopathological evidence of tumorigenesis. These findings support the long-term safety of this therapeutic modality.

International Society for Cell & Gene Therapy Stem Cell Engineering Committee report on the current state of hematopoietic stem and progenitor cell-based genomic therapies and the challenges faced

Genetic manipulation of hematopoietic stem cells (HSCs) is being developed as a therapeutic strategy for several inherited disorders. This field is rapidly evolving with several novel tools and techniques being employed to achieve desired genetic changes. While commercial products are now available for sickle cell disease, transfusion-dependent β-thalassemia, metachromatic leukodystrophy and adrenoleukodystrophy, several challenges remain in patient selection, HSC mobilization and collection, genetic manipulation of stem cells, conditioning, hematologic recovery and post-transplant complications, financial issues, equity of access and institutional and global preparedness. In this report, we explore the current state of development of these therapies and provide a comprehensive assessment of the challenges these therapies face as well as potential solutions.

Evolution of the clinical-stage hyperactive TcBuster transposase as a platform for robust non-viral production of adoptive cellular therapies

Cellular therapies for the treatment of human diseases, such as chimeric antigen receptor (CAR) T and natural killer (NK) cells have shown remarkable clinical efficacy in treating hematological malignancies; however, current methods mainly utilize viral vectors that are limited by their cargo size capacities, high cost, and long timelines for production of clinical reagent. Delivery of genetic cargo via DNA transposon engineering is a more timely and cost-effective approach, yet has been held back by less efficient integration rates. Here, we report the development of a novel hyperactive TcBuster (TcB-M) transposase engineered through structure-guided and in vitro evolution approaches that achieves high-efficiency integration of large, multicistronic CAR-expression cassettes in primary human cells. Our proof-of-principle TcB-M engineering of CAR-NK and CAR-T cells shows low integrated vector copy number, a safe insertion site profile, robust in vitro function, and improves survival in a Burkitt lymphoma xenograft model in vivo. Overall, TcB-M is a versatile, safe, efficient and open-source option for the rapid manufacture and preclinical testing of primary human immune cell therapies through delivery of multicistronic large cargo via transposition.

Nucleic acid-based drugs for patients with solid tumours

The treatment of patients with advanced-stage solid tumours typically involves a multimodality approach (including surgery, chemotherapy, radiotherapy, targeted therapy and/or immunotherapy), which is often ultimately ineffective. Nucleic acid-based drugs, either as monotherapies or in combination with standard-of-care therapies, are rapidly emerging as novel treatments capable of generating responses in otherwise refractory tumours. These therapies include those using viral vectors (also referred to as gene therapies), several of which have now been approved by regulatory agencies, and nanoparticles containing mRNAs and a range of other nucleotides. In this Review, we describe the development and clinical activity of viral and non-viral nucleic acid-based treatments, including their mechanisms of action, tolerability and available efficacy data from patients with solid tumours. We also describe the effects of the tumour microenvironment on drug delivery for both systemically administered and locally administered agents. Finally, we discuss important trends resulting from ongoing clinical trials and preclinical testing, and manufacturing and/or stability considerations that are expected to underpin the next generation of nucleic acid agents for patients with solid tumours.

Twin Prime Editing Mediated Exon Skipping/Reinsertion for Restored Collagen VII Expression in Recessive Dystrophic Epidermolysis Bullosa

Gene editing nucleases, base editors, and prime editors are potential locus-specific genetic treatment strategies for recessive dystrophic epidermolysis bullosa; however, many recessive dystrophic epidermolysis bullosa COL7A1 pathogenic nucleotide variations (PNVs) are unique, making the development of personalized editing reagents challenging. A total of 270 of the ∼320 COL7A1 epidermolysis bullosa PNVs reside in exons that can be skipped, and antisense oligonucleotides and gene editing nucleases have been used to create in-frame deletions. Antisense oligonucleotides are transient, and nucleases generate deleterious double-stranded DNA breaks and uncontrolled mixtures of allele products. We developed a twin prime editing strategy using the PEmax and recently evolved PE6 prime editors and dual prime editing guide RNAs flanking COL7A1 exon 5. Prime editing-mediated deletion of exon 5 with a homozygous premature stop codon was achieved in recessive dystrophic epidermolysis bullosa fibroblasts, keratinocytes, and induced pluripotent stem cells with minimal double-stranded DNA breaks, and collagen type VII protein was restored. Twin prime editing can replace the target exon with recombinase attachment sequences, and we exploited this to reinsert a normal copy of exon 5 using the Bxb1 recombinase. These findings demonstrate that twin prime editing can facilitate locus-specific, predictable, in-frame deletions and sequence replacement with few double-stranded DNA breaks as a strategy that may enable a single therapeutic agent to treat multiple recessive dystrophic epidermolysis bullosa patient cohorts.

Targeted gene delivery systems for T-cell engineering

T lymphocytes are indispensable for the host systems of defense against pathogens, tumors, and environmental threats. The therapeutic potential of harnessing the cytotoxic properties of T lymphocytes for antigen-specific cell elimination is both evident and efficacious. Genetically engineered T-cells, such as those employed in CAR-T and TCR-T cell therapies, have demonstrated significant clinical benefits in treating cancer and autoimmune disorders. However, the current landscape of T-cell genetic engineering is dominated by strategies that necessitate in vitro T-cell isolation and modification, which introduce complexity and prolong the development timeline of T-cell based immunotherapies. This review explores the complexities of gene delivery systems designed for T cells, covering both viral and nonviral vectors. Viral vectors are known for their high transduction efficiency, yet they face significant limitations, such as potential immunogenicity and the complexities involved in large-scale production. Nonviral vectors, conversely, offer a safer profile and the potential for scalable manufacturing, yet they often struggle with lower transduction efficiency. The pursuit of gene delivery systems that can achieve targeted gene transfer to T cell without the need for isolation represents a significant advancement in the field. This review assesses the design principles and current research progress of such systems, highlighting the potential for in vivo gene modification therapies that could revolutionize T-cell based treatments. By providing a comprehensive analysis of these systems, we aim to contribute valuable insights into the future development of T-cell immunotherapy.

Gene therapy: principles, challenges and use in clinical practice

INTRODUCTION

Gene therapy is an emerging topic in medicine. The first products have already been licensed in the European Union for the treatment of immune deficiency, spinal muscular atrophy, hemophilia, retinal dystrophy, a rare neurotransmitter disorder and some hematological cancers, while many more are being assessed in preclinical and clinical trials.

OBJECTIVE

The purpose of this review is to provide an overview of the core principles of gene therapy along with information on challenges and risks. Benefits, adverse effects and potential risks are illustrated based on the examples of hemophilia and spinal muscular atrophy.

RESULTS

At present, in-vitro and in-vivo gene addition or gene augmentation is the most commonly established type of gene therapy. More recently, more sophisticated and precise approaches such as in situ gene editing have moved into focus. However, all types of gene therapy require long-term observation of treated patients to ensure safety, efficacy, predictability and durability. Important safety concerns include immune reactions to the vector, the foreign DNA or the new protein resulting from gene therapy, and a remaining low cancer risk based on insertional mutagenesis. Ethical and regulatory issues need to be addressed, and new reimbursement models are called for to ease the financial burden that this new treatment poses for the health care system.

CONCLUSION

Gene therapy holds great promise for considerable improvement or even cure of genetic diseases with serious clinical consequences. However, a number of questions and issues need to be clarified to ensure broad accessibility of safe and efficacious products.

Non-clinical safety assessment of novel drug modalities: Genome safety perspectives on viral-, nuclease- and nucleotide-based gene therapies

Gene therapies have emerged as promising treatments for various conditions including inherited diseases as well as cancer. Ensuring their safe clinical application requires the development of appropriate safety testing strategies. Several guidelines have been provided by health authorities to address these concerns. These guidelines state that non-clinical testing should be carried out on a case-by-case basis depending on the modality. This review focuses on the genome safety assessment of frequently used gene therapy modalities, namely Adeno Associated Viruses (AAVs), Lentiviruses, designer nucleases and mRNAs. Important safety considerations for these modalities, amongst others, are vector integrations into the patient genome (insertional mutagenesis) and off-target editing. Taking into account the constraints of in vivo studies, health authorities endorse the development of novel approach methodologies (NAMs), which are innovative in vitro strategies for genotoxicity testing. This review provides an overview of NAMs applied to viral and CRISPR/Cas9 safety, including next generation sequencing-based methods for integration site analysis and off-target editing. Additionally, NAMs to evaluate the oncogenicity risk arising from unwanted genomic modifications are discussed. Thus, a range of promising techniques are available to support the safe development of gene therapies. Thorough validation, comparisons and correlations with clinical outcomes are essential to identify the most reliable safety testing strategies. By providing a comprehensive overview of these NAMs, this review aims to contribute to a better understanding of the genome safety perspectives of gene therapies.

Clinical perspective on topical vaccination strategies

Vaccination is one of the most successful measures in modern medicine to combat diseases, especially infectious diseases, and saves millions of lives every year. Vaccine design and development remains critical and involves many aspects, including the choice of platform, antigen, adjuvant, and route of administration. Topical vaccination, defined herein as the introduction of a vaccine to any of the three layers of the human skin, has attracted interest in recent years as an alternative vaccination approach to the conventional intramuscular administration because of its potential to be needle-free and induce a superior immune response against pathogens. In this review, we describe recent progress in developing topical vaccines, highlight progress in the development of delivery technologies for topical vaccines, discuss potential factors that might impact the topical vaccine efficacy, and provide an overview of the current clinical landscape of topical vaccines.

Deciphering conundrums of adeno-associated virus liver-directed gene therapy: focus on hemophilia

Adeno-associated virus gene therapy has been the subject of intensive investigation for monogenic disease gene addition therapy for more than 25 years, yet few therapies have been approved by regulatory agencies. Most have not progressed beyond phase 1/2 due to toxicity, lack of efficacy, or both. The liver is a natural target for adeno-associated virus since most serotypes have a high degree of tropism for hepatocytes due to cell surface receptors for the virus and the unique liver sinusoidal geometry facilitating high volumes of blood contact with hepatocyte cell surfaces. Recessive monogenic diseases such as hemophilia represent promising targets since the defective proteins are often synthesized in the liver and secreted into the circulation, making them easy to measure, and many do not require precise regulation. Yet, despite initiation of many disease-specific clinical trials, therapeutic windows are often nonexistent, resulting in excess toxicity and insufficient efficacy. Iterative progress built on these attempts is best illustrated by hemophilia, with the first regulatory approvals for factor IX and factor VIII gene therapies eventually achieved 25 years after the first gene therapy studies in humans. Although successful gene transfer may result in the production of sufficient transgenic protein to modify the disease, many emerging questions on durability, predictability, reliability, and variability of response have not been answered. The underlying biology accounting for these heterogeneous responses and the interplay between host and virus is the subject of intense investigation and the subject of this review.

A case of T-cell acute lymphoblastic leukemia in retroviral gene therapy for ADA-SCID

Hematopoietic stem cell gene therapy (GT) using a γ-retroviral vector (γ-RV) is an effective treatment for Severe Combined Immunodeficiency due to Adenosine Deaminase deficiency. Here, we describe a case of GT-related T-cell acute lymphoblastic leukemia (T-ALL) that developed 4.7 years after treatment. The patient underwent chemotherapy and haploidentical transplantation and is currently in remission. Blast cells contain a single vector insertion activating the LIM-only protein 2 (LMO2) proto-oncogene, confirmed by physical interaction, and low Adenosine Deaminase (ADA) activity resulting from methylation of viral promoter. The insertion is detected years before T-ALL in multiple lineages, suggesting that further hits occurred in a thymic progenitor. Blast cells contain known and novel somatic mutations as well as germline mutations which may have contributed to transformation. Before T-ALL onset, the insertion profile is similar to those of other ADA-deficient patients. The limited incidence of vector-related adverse events in ADA-deficiency compared to other γ-RV GT trials could be explained by differences in transgenes, background disease and patient's specific factors.

In vitro encapsulation and expansion of T and CAR-T cells using 3D synthetic thermo-responsive matrices

Suspension cell culture and rigid commercial substrates are the most common methods to clinically manufacture therapeutic CAR-T cells ex vivo. However, suspension culture and nano/micro-scale commercial substrates poorly mimic the microenvironment where T cells naturally develop, leading to profound impacts on cell proliferation and phenotype. To overcome this major challenge, macro-scale substrates can be used to emulate that environment with higher precision. This work employed a biocompatible thermo-responsive material with tailored mechanical properties as a potential synthetic macro-scale scaffold to support T cell encapsulation and culture. Cell viability, expansion, and phenotype changes were assessed to study the effect of two thermo-responsive hydrogel materials with stiffnesses of 0.5 and 17 kPa. Encapsulated Pan-T and CAR-T cells were able to grow and physically behave similar to the suspension control. Furthermore, matrix stiffness influenced T cell behavior. In the softer polymer, T cells had higher activation, differentiation, and maturation after encapsulation obtaining significant cell numbers. Even when terpolymer encapsulation affected the CAR-T cell viability and expansion, CAR T cells expressed favorable phenotypical profiles, which was supported with cytokines and lactate production. These results confirmed the biocompatibility of the thermo-responsive hydrogels and their feasibility as a promising 3D macro-scale scaffold for in vitro T cell expansion that could potentially be used for cell manufacturing process.

Mesenchymal stem cells in craniofacial reconstruction: a comprehensive review

Craniofacial reconstruction faces many challenges, including high complexity, strong specificity, severe injury, irregular and complex wounds, and high risk of bleeding. Traditionally, the "gold standard" for treating craniofacial bone defects has been tissue transplantation, which involves the transplantation of bone, cartilage, skin, and other tissues from other parts of the body. However, the shape of craniofacial bone and cartilage structures varies greatly and is distinctly different from ordinary long bones. Craniofacial bones originate from the neural crest, while long bones originate from the mesoderm. These factors contribute to the poor effectiveness of tissue transplantation in repairing craniofacial defects. Autologous mesenchymal stem cell transplantation exhibits excellent pluripotency, low immunogenicity, and minimally invasive properties, and is considered a potential alternative to tissue transplantation for treating craniofacial defects. Researchers have found that both craniofacial-specific mesenchymal stem cells and mesenchymal stem cells from other parts of the body have significant effects on the restoration and reconstruction of craniofacial bones, cartilage, wounds, and adipose tissue. In addition, the continuous development and application of tissue engineering technology provide new ideas for craniofacial repair. With the continuous exploration of mesenchymal stem cells by researchers and the continuous development of tissue engineering technology, the use of autologous mesenchymal stem cell transplantation for craniofacial reconstruction has gradually been accepted and promoted. This article will review the applications of various types of mesenchymal stem cells and related tissue engineering in craniofacial repair and reconstruction.

Recapitulating primary immunodeficiencies with expanded potential stem cells: Proof of concept with STAT1 gain of function

BACKGROUND

Inborn errors of immunity (IEI) often lack specific disease models and personalized management. Signal transducer and activator of transcription (STAT)-1 gain of function (GoF) is such example of an IEI with diverse clinical phenotype with unclear pathomechanisms and unpredictable response to therapy. Limitations in obtaining fresh samples for functional testing and research further highlights the need for patient-specific ex vivo platforms.

OBJECTIVE

Using STAT1-GoF as an example IEI, we investigated the potential of patient-derived expanded potential stem cells (EPSC) as an ex vivo platform for disease modeling and personalized treatment.

METHODS

We generated EPSC derived from individual STAT1-GoF patients. STAT1 mutations were confirmed with Sanger sequencing. Functional testing including STAT1 phosphorylation/dephosphorylation and gene expression with or without Janus activating kinase inhibitors were performed. Functional tests were repeated on EPSC lines with GoF mutations repaired by CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9) editing.

RESULTS

EPSC were successfully reprogrammed from STAT1-GoF patients and expressed the same pluripotent makers as controls, with distinct morphologic differences. Patient-derived EPSC recapitulated the functional abnormalities of index STAT1-GoF patients with STAT1 hyperphosphorylation and increased expression of STAT1 and its downstream genes (IRF1, APOL6, and OAS1) after IFN-γ stimulation. Addition of ruxolitinib and baricitinib inhibited STAT1 hyperactivation in STAT1-GoF EPSC in a dose-dependent manner, which was not observed with tofacitinib. Corrected STAT1 phosphorylation and downstream gene expression were observed among repaired STAT1-GoF EPSC cell lines.

CONCLUSION

This proof-of-concept study demonstrates the potential of our patient-derived EPSC platform to model STAT1-GoF. We propose this platform when researching, recapitulating, and repairing other IEI in the future.

Optimised protocols to generate high titre lentiviral vectors using a novel transfection agent enabling extended HEK293T culture following transient transfection and suspension culture

HIV-1 based lentiviral viruses are considered powerful and versatile gene therapy vectors to deliver therapeutic genes to patients with hereditary or acquired diseases. These vectors can efficiently transduce a variety of cell types when dividing or non-dividing to provide permanent delivery and long-term gene expression. Demand for scalable manufacturing protocols able to generate enough high titre vector for widespread use of this technology is increasing and considerable efforts to improve vector production cost-effectively, is ongoing. Current methods for LV production mainly use transient transfection of producer cell lines. Cells can be grown at scale, either in 2D relying on culturing producer cells in multi-tray flask cell culture factories or in roller bottles or can be adapted to grow in 3D suspensions in large batch fermenters. This suits rapid production and testing of new vector constructs pre-clinically for their efficacy, particle titre and safety. In this study, we sought to improve lentiviral titre over time by testing two alternative commercially available transfection reagents Fugene® 6 and Genejuice® with the commonly used polycation, polyethyleneimine. Our aim was to identify less cytotoxic transfection reagents that could be used to generate LV particles at high titre past the often used 72 h period when vector is usually collected before producer cell death is caused due to post transfection cytotoxicity. We show that LV could be produced in extended culture using Genejuice® and even by transfected cells in glass flasks in suspension. Because this delivery agent is less toxic to 293 T producer cells, following optimisation of transfection we found that LV can be harvested for more than 10 days at high titre. Using our protocol, titres of 109 TU/ml and 108 TU/ml were routinely reached via traditional monolayer conditions or suspension cultures, respectively. We propose, this simple change in vector production enables large volumes of high titre vector to be produced, cost effectively for non-clinical in vivo and in vitro applications or for more stringent downstream clinical grade vector purification.

The Regenerative Microenvironment of the Tissue Engineering for Urethral Strictures

Urethral stricture caused by various reasons has threatened the quality of life of patients for decades. Traditional reconstruction methods, especially for long-segment injuries, have shown poor outcomes in treating urethral strictures. Tissue engineering for urethral regeneration is an emerging concept in which special designed scaffolds and seed cells are used to promote local urethral regeneration. The scaffolds, seed cells, various factors and the host interact with each other and form the regenerative microenvironment. Among the various interactions involved, vascularization and fibrosis are the most important biological processes during urethral regeneration. Mesenchymal stem cells and induced pluripotent stem cells play special roles in stricture repair and facilitate long-segment urethral regeneration, but they may also induce carcinogenesis and genomic instability during reconstruction. Nevertheless, current technologies, such as genetic engineering, molecular imaging, and exosome extraction, provide us with opportunities to manage seed cell-related regenerative risks. In this review, we described the interactions among seed cells, scaffolds, factors and the host within the regenerative microenvironment, which may help in determining the exact molecular mechanisms involved in urethral stricture regeneration and promoting clinical trials and the application of urethral tissue engineering in patients suffering from urethral stricture.

Targeted nonviral delivery of genome editors in vivo

Cell-type-specific in vivo delivery of genome editing molecules is the next breakthrough that will drive biological discovery and transform the field of cell and gene therapy. Here, we discuss recent advances in the delivery of CRISPR-Cas genome editors either as preassembled ribonucleoproteins or encoded in mRNA. Both strategies avoid pitfalls of viral vector-mediated delivery and offer advantages including transient editor lifetime and potentially streamlined manufacturing capability that are already proving valuable for clinical use. We review current applications and future opportunities of these emerging delivery approaches that could make genome editing more efficacious and accessible in the future.

Gene regulation in inborn errors of immunity: Implications for gene therapy design and efficacy

Inborn errors of immunity (IEI) present a unique paradigm in the realm of gene therapy, emphasizing the need for precision in therapeutic design. As gene therapy transitions from broad-spectrum gene addition to careful modification of specific genes, the enduring safety and effectiveness of these therapies in clinical settings have become crucial. This review discusses the significance of IEIs as foundational models for pioneering and refining precision medicine. We explore the capabilities of gene addition and gene correction platforms in modifying the DNA sequence of primary cells tailored for IEIs. The review uses four specific IEIs to highlight key issues in gene therapy strategies: X-linked agammaglobulinemia (XLA), X-linked chronic granulomatous disease (X-CGD), X-linked hyper IgM syndrome (XHIGM), and immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX). We detail the regulatory intricacies and therapeutic innovations for each disorder, incorporating insights from relevant clinical trials. For most IEIs, regulated expression is a vital aspect of the underlying biology, and we discuss the importance of endogenous regulation in developing gene therapy strategies.

Functional genomics in inborn errors of immunity

Inborn errors of immunity (IEI) comprise a diverse spectrum of 485 disorders as recognized by the International Union of Immunological Societies Committee on Inborn Error of Immunity in 2022. While IEI are monogenic by definition, they illuminate various pathways involved in the pathogenesis of polygenic immune dysregulation as in autoimmune or autoinflammatory syndromes, or in more common infectious diseases that may not have a significant genetic basis. Rapid improvement in genomic technologies has been the main driver of the accelerated rate of discovery of IEI and has led to the development of innovative treatment strategies. In this review, we will explore various facets of IEI, delving into the distinctions between PIDD and PIRD. We will examine how Mendelian inheritance patterns contribute to these disorders and discuss advancements in functional genomics that aid in characterizing new IEI. Additionally, we will explore how emerging genomic tools help to characterize new IEI as well as how they are paving the way for innovative treatment approaches for managing and potentially curing these complex immune conditions.