In utero stem cell transplantation and gene therapy: rationale, history, and recent advances toward clinical application

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.

In Utero Cell Treatment of Hemophilia A Mice via Human Amniotic Fluid Mesenchymal Stromal Cell Engraftment

Hemophilia is a genetic disorder linked to the sex chromosomes, resulting in impaired blood clotting due to insufficient intrinsic coagulation factors. There are approximately one million individuals worldwide with hemophilia, with hemophilia A being the most prevalent form. The current treatment for hemophilia A involves the administration of clotting factor VIII (FVIII) through regular and costly injections, which only provide temporary relief and pose inconveniences to patients. In utero transplantation (IUT) is an innovative method for addressing genetic disorders, taking advantage of the underdeveloped immune system of the fetus. This allows mesenchymal stromal cells to play a role in fetal development and potentially correct genetic abnormalities. The objective of this study was to assess the potential recovery of coagulation disorders in FVIII knockout hemophilia A mice through the administration of human amniotic fluid mesenchymal stromal cells (hAFMSCs) via IUT at the D14.5 fetal stage. The findings revealed that the transplanted human cells exhibited fusion with the recipient liver, with a ratio of approximately one human cell per 10,000 mouse cells and produced human FVIII protein in the livers of IUT-treated mice. Hemophilia A pups born to IUT recipients demonstrated substantial improvement in their coagulation issues from birth throughout the growth period of up to 12 weeks of age. Moreover, FVIII activity reached its peak at 6 weeks of age, while the levels of FVIII inhibitors remained relatively low during the 12-week testing period in mice with hemophilia. In conclusion, the results indicated that prenatal intrahepatic therapy using hAFMSCs has the potential to improve clotting issues in FVIII knockout mice, suggesting it as a potential clinical treatment for individuals with hemophilia A.

Transplanting FVIII/ET3-secreting cells in fetal sheep increases FVIII levels long-term without inducing immunity or toxicity

Hemophilia A is the most common X-linked bleeding disorder affecting more than half-a-million individuals worldwide. Persons with severe hemophilia A have coagulation FVIII levels <1% and experience spontaneous debilitating and life-threatening bleeds. Advances in hemophilia A therapeutics have significantly improved health outcomes, but development of FVIII inhibitory antibodies and breakthrough bleeds during therapy significantly increase patient morbidity and mortality. Here we use sheep fetuses at the human equivalent of 16-18 gestational weeks, and we show that prenatal transplantation of human placental cells (107-108/kg) bioengineered to produce an optimized FVIII protein, results in considerable elevation in plasma FVIII levels that persists for >3 years post-treatment. Cells engraft in major organs, and none of the recipients mount immune responses to either the cells or the FVIII they produce. Thus, these studies attest to the feasibility, immunologic advantage, and safety of treating hemophilia A prior to birth.

Acceptability of prenatal diagnosis and prenatal treatment of haemophilia using cell and gene therapies within US haemophilia community

BACKGROUND

The overall burden of disease in persons with haemophilia continues to be high despite the latest advancements in therapeutics. Clinical trials testing prenatal treatments for several genetic disorders are underway or are recruiting subjects, attesting to the much-needed change in paradigm of how patients with monogenic disorders can be treated. Here we investigate the overall attitude towards prenatal diagnosis, preferences on types of prenatal therapies for haemophilia, the level of 'acceptable' risk tolerated, and which social and moral pressures or disease personal experiences may predict willingness of individuals to consider foetal therapy in a future pregnancy.

RESULTS

A multidisciplinary team designed the survey, and the study was carried out using REDCap, and publicized through the National Haemophilia Foundation. Subjects ≥18 years of age were eligible to participate in the study. We assessed participants' attitudes towards prenatal therapy and their level of 'acceptable' risk towards the procedure and therapy. The survey was completed by 67 adults, the majority females. Respondents were willing to undergo prenatal diagnosis, and their main concerns related to the well-being of the pregnant woman and the foetus regarding lasting therapeutic efficacy, side effects of the therapy, and procedural risks, but they were likely to accept a wide range of prenatal therapeutic options, particularly if the foetal therapy proved to be long-lasting and safe.

CONCLUSIONS

These data demonstrate the willingness of persons with haemophilia, and the haemophilia community, to explore new treatment options beyond the currently offered approaches.

Experimental and clinical progress of in utero hematopoietic cell transplantation therapy for congenital disorders

In utero hematopoietic cell transplantation (IUHCT) is considered a potentially efficient therapeutic approach with relatively few side effects, compared to adult hematopoietic cell transplantation, for various hematological genetic disorders. The principle of IUHCT has been extensively studied in rodent models and in some large animals with close evolutionary similarities to human beings. However, IUHCT has only been used to rebuild human T cell immunity in certain patients with inherent immunodeficiencies. This review will first summarize the animal models utilized for IUHCT investigations and describe the associated outcomes. Recent advances and potential barriers for successful IUHCT are discussed, followed by possible strategies to overcome these barriers experimentally. Lastly, we will outline the progress made towards utilizing IUHCT to treat inherent disorders for patients, list out associated limitations and propose feasible means to promote the efficacy of IUHCT clinically.

Prenatal Somatic Cell Gene Therapies: Charting a Path Toward Clinical Applications (Proceedings of the CERSI-FDA Meeting)

We are living in a golden age of medicine in which the availability of prenatal diagnosis, fetal therapy, and gene therapy/editing make it theoretically possible to repair almost any defect in the genetic code. Furthermore, the ability to diagnose genetic disorders before birth and the presence of established surgical techniques enable these therapies to be delivered safely to the fetus. Prenatal therapies are generally used in the second or early third trimester for severe, life-threatening disorders for which there is a clear rationale for intervening before birth. While there has been promising work for prenatal gene therapy in preclinical models, the path to a clinical prenatal gene therapy approach is complex. We recently held a conference with the University of California, San Francisco-Stanford Center of Excellence in Regulatory Science and Innovation, researchers, patient advocates, regulatory (members of the Food and Drug Administration), and other stakeholders to review the scientific background and rationale for prenatal somatic cell gene therapy for severe monogenic diseases and initiate a dialogue toward a safe regulatory path for phase 1 clinical trials. This review represents a summary of the considerations and discussions from these conversations.

Catching Them Early: Framework Parameters and Progress for Prenatal and Childhood Application of Advanced Therapies

Advanced therapy medicinal products (ATMPs) are medicines for human use based on genes, cells or tissue engineering. After clear successes in adults, the nascent technology now sees increasing pediatric application. For many still untreatable disorders with pre- or perinatal onset, timely intervention is simply indispensable; thus, prenatal and pediatric applications of ATMPs hold great promise for curative treatments. Moreover, for most inherited disorders, early ATMP application may substantially improve efficiency, economy and accessibility compared with application in adults. Vindicating this notion, initial data for cell-based ATMPs show better cell yields, success rates and corrections of disease parameters for younger patients, in addition to reduced overall cell and vector requirements, illustrating that early application may resolve key obstacles to the widespread application of ATMPs for inherited disorders. Here, we provide a selective review of the latest ATMP developments for prenatal, perinatal and pediatric use, with special emphasis on its comparison with ATMPs for adults. Taken together, we provide a perspective on the enormous potential and key framework parameters of clinical prenatal and pediatric ATMP application.

Long-term safety evaluation of placental mesenchymal stromal cells for in utero repair of myelomeningocele in a novel ovine model

PURPOSE

Augmentation of in utero myelomeningocele repair with human placental mesenchymal stromal cells seeded onto extracellular matrix (PMSC-ECM) improves motor outcomes in an ovine myelomeningocele model. This study evaluated the safety of PMSC-ECM application directly onto the fetal spinal cord in preparation for a clinical trial.

METHODS

Laminectomy of L5-L6 with PMSC-ECM placement directly onto the spinal cord was performed in five fetal lambs at gestational age (GA) 100-106 days. Lambs and ewes were monitored for three months following delivery. Lambs underwent magnetic resonance imaging (MRI) of the brain and spine at birth and at three months. All organs from lambs and uteri from ewes underwent histologic evaluation. Lamb spinal cords and brains and ewe placentas were evaluated for persistence of PMSCs by polymerase chain reaction for presence of human DNA.

RESULTS

MRIs demonstrated no evidence of abnormal tissue growth or spinal cord tethering. Histological analysis demonstrated no evidence of abnormal tissue growth or treatment related adverse effects. No human DNA was identified in evaluated tissues.

CONCLUSION

There was no evidence of abnormal tissue growth or PMSC persistence at three months following in utero application of PMSC-ECM to the spinal cord. This supports proceeding with clinical trials of PMSC-ECM for in utero myelomeningocele repair.

LEVEL OF EVIDENCE

N/A TYPE OF STUDY: Basic science.

Amniotic fluid stabilized lipid nanoparticles for in utero intra-amniotic mRNA delivery

Congenital disorders resulting in pathological protein deficiencies are most often treated postnatally with protein or enzyme replacement therapies. However, treatment of these disorders in utero before irreversible disease onset could significantly minimize disease burden, morbidity, and mortality. One possible strategy for the prenatal treatment of congenital disorders is in utero delivery of messenger RNA (mRNA). mRNA is a nucleic acid therapeutic that has previously been investigated as a platform for protein replacement therapies and gene editing technologies. While viral vectors have been explored to induce intracellular expression of mRNA, they are limited in their clinical application due to risks associated with immunogenicity and genomic integration. As an alternative to viral vectors, safe and efficient in utero mRNA delivery can be achieved using ionizable lipid nanoparticles (LNPs). While LNPs have demonstrated potent in vivo mRNA delivery to the liver following intravenous administration, intra-amniotic delivery has the potential to deliver mRNA to cells and tissues beyond those in the liver, such as in the skin, lung, and digestive tract. However, LNP stability in fetal amniotic fluid and how this stability affects mRNA delivery has not been previously investigated. Here, we engineered a library of LNPs using orthogonal design of experiments (DOE) to evaluate how LNP structure affects their stability in amniotic fluid ex utero and whether a lead candidate identified from these stability measurements enables intra-amniotic mRNA delivery in utero. We used a combination of techniques including dynamic light scattering (DLS), transmission electron microscopy (TEM), and chromatography followed by protein content quantification to screen LNP stability in amniotic fluids. These results identified multiple lead LNP formulations that are highly stable in amniotic fluids ranging from small animals to humans, including mouse, sheep, pig, and human amniotic fluid samples. We then demonstrate that stable LNPs from the ex utero screen in mouse amniotic fluid enabled potent mRNA delivery in primary fetal lung fibroblasts and in utero following intra-amniotic injection in a murine model. This exploration of ex utero stability in amniotic fluids demonstrates a means by which to identify novel LNP formulations for prenatal treatment of congenital disorders via in utero mRNA delivery.

Society for Maternal-Fetal Medicine Special Statement: Beyond the scalpel: in utero fetal gene therapy and curative medicine

With the recent advances in gene editing with systems such as CRISPR-Cas9, precise genome editing in utero is on the horizon. Sickle cell disease is an excellent candidate for in utero fetal gene therapy, because the disease is monogenic, causes irreversible harm, and has life-limiting morbidity. Gene therapy has recently been proven to be effective in an adolescent patient. Several hurdles still impede the progress for fetal gene therapy in humans, including an incomplete understanding of the fetal immune system, unclear maternal immune responses to in utero gene therapy, risks of off-target effects from gene editing, gestational age constraints, and ethical questions surrounding fetal genetic intervention. However, none of these barriers appears insurmountable, and the journey to in utero gene therapy for sickle cell disease and other conditions should be well underway.

In Utero Gene Therapy for Primary Immunodeficiencies

Primary immunodeficiencies (PIDs) have become a prime target for gene therapy given the morbidity, mortality, and the single gene etiology. Given that outcomes are better the earlier gene therapy is implemented, it is possible that fetal gene therapy may be an important future direction for the treatment of PIDs. In this chapter, the current treatments available for several PIDs will be reviewed, as well as the history and current status of gene therapy for PIDs. The possibility of in utero gene therapy as a possibility will then be discussed.

Prenatal Gene Therapy

Prenatal gene therapy could provide a cure for many monogenic diseases. Prenatal gene therapy has multiple potential advantages over postnatal therapy, including treating before the onset of disease, the ability to induce tolerance and cross the blood-brain barrier. In this chapter, we will describe in utero gene therapy and its rationale, clinical trials of postnatal gene therapy, preclinical studies of in utero gene therapy, and potential risks to the mother and fetus.

In Utero Fetal Therapy: Stem Cells, Cell Transplantation, Gene Therapy, and CRISPR-Cas9

In utero fetal therapy offers the opportunity to prevent and treat diseases with a cellular or genetic basis. Components of successful fetal treatment include isolation of a replacement cell population, in utero stem cell transplantation, cell engraftment with fetal immune tolerance, and ongoing cell function. Fetal gene therapy with CRISPR-Cas9 represents an exciting potential therapy for genetic diseases not amenable to gene supplementation via adenoviral vector transduction. These fetal therapies have unique ethical and safety considerations. Clinical trials for in utero cell therapy are underway, as additional discoveries in stem cell biology and gene therapy move closer to clinical translation.

Emerging drugs for hemophilia A: insights into phase II and III clinical trials

INTRODUCTION

Hemophilia is a lifelong, genetic-bleeding disorder, which inadequately treated results in permanent joint damage. It is characterized by spontaneous and trauma-related bleeding episodes. In the last 50 years, treatment has seen dramatic improvements which have improved the quality of life of persons with hemophilia.

AREAS COVERED

This review will provide a summary of current pharmacological approaches for hemophilia A as well as discuss novel agents which are either approved recently or in phase II-III clinical trials, plasma-derived and recombinant factor VIII (FVIII) products, extended half-life FVIII products, bypassing agents and non-replacement therapies.

EXPERT OPINION

Novel therapies are already changing the way that hemophilia A is managed, and as more new therapies get approved, there will be a revolution in the management of this serious condition. Clinicians will have both the opportunities as well as the challenges of incorporating such new technologies into clinical practice.

Investigating Optimal Autologous Cellular Platforms for Prenatal or Perinatal Factor VIII Delivery to Treat Hemophilia A

Patients with the severe form of hemophilia A (HA) present with a severe phenotype, and can suffer from life-threatening, spontaneous hemorrhaging. While prophylactic FVIII infusions have revolutionized the clinical management of HA, this treatment is short-lived, expensive, and it is not available to many A patients worldwide. In the present study, we evaluated a panel of readily available cell types for their suitability as cellular vehicles to deliver long-lasting FVIII replacement following transduction with a retroviral vector encoding a B domain-deleted human F8 transgene. Given the immune hurdles that currently plague factor replacement therapy, we focused our investigation on cell types that we deemed to be most relevant to either prenatal or very early postnatal treatment and that could, ideally, be autologously derived. Our findings identify several promising candidates for use as cell-based FVIII delivery vehicles and lay the groundwork for future mechanistic studies to delineate bottlenecks to efficient production and secretion of FVIII following genetic-modification.

Tolerance induction and microglial engraftment after fetal therapy without conditioning in mice with Mucopolysaccharidosis type VII

Mucopolysaccharidosis type VII (MPS7) is a lysosomal storage disorder (LSD) resulting from mutations in the β-glucuronidase gene, leading to multiorgan dysfunction and fetal demise. While postnatal enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation have resulted in some phenotypic improvements, prenatal treatment might take advantage of a unique developmental window to penetrate the blood-brain barrier or induce tolerance to the missing protein, addressing two important shortcomings of postnatal therapy for multiple LSDs. We performed in utero ERT (IUERT) at E14.5 in MPS7 mice and improved survival of affected mice to birth. IUERT penetrated brain microglia, whereas postnatal administration did not, and neurological testing (after IUERT plus postnatal administration) showed decreased microglial inflammation and improved grip strength in treated mice. IUERT prevented antienzyme antibody development even after multiple repeated postnatal challenges. To test a more durable treatment strategy, we performed in utero hematopoietic stem cell transplantation (IUHCT) using congenic CX3C chemokine receptor 1-green fluorescent protein (CX3CR1-GFP) mice as donors, such that donor-derived microglia are identified by GFP expression. In wild-type recipients, hematopoietic chimerism resulted in microglial engraftment throughout the brain without irradiation or conditioning; the transcriptomes of donor and host microglia were similar. IUHCT in MPS7 mice enabled cross-correction of liver Kupffer cells and improved phenotype in multiple tissues. Engrafted microglia were seen in chimeric mice, with decreased inflammation near donor microglia. These results suggest that fetal therapy with IUERT and/or IUHCT could overcome the shortcomings of current treatment strategies to improve phenotype in MPS7 and other LSDs.

Reflections on the genetics-first approach to advancements in molecular genetic and neurobiological research on neurodevelopmental disorders

BACKGROUND

Neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD) and intellectual disability (ID), are common diagnoses with highly heterogeneous phenotypes and etiology. The genetics-first approach to research on NDDs has led to the identification of hundreds of genes conferring risk for ASD, ID, and related symptoms.

MAIN BODY

Although relatively few individuals with NDDs share likely gene-disruptive (LGD) mutations in the same gene, characterization of overlapping functions, protein networks, and temporospatial expression patterns among these genes has led to increased understanding of the neurobiological etiology of NDDs. This shift in focus away from single genes and toward broader gene-brain-behavior pathways has been accelerated by the development of publicly available transcriptomic databases, cell type-specific research methods, and sequencing of non-coding genomic regions.

CONCLUSIONS

The genetics-first approach to research on NDDs has advanced the identification of critical protein function pathways and temporospatial expression patterns, expanding the impact of this research beyond individuals with single-gene mutations to the broader population of patients with NDDs.

A narrative review of in utero gene therapy: advances, challenges, and future considerations

The field of in utero gene therapy (IUGT) represents a crossroad of technologic advancements and medical ethical boundaries. Several strategies have been developed for IUGT focusing on either modifying endogenous genes, replacing missing genes, or modifying gene transcription products. The list of candidate diseases such as hemoglobinopathies, cystic fibrosis, lysosomal storage disorders continues to grow with new strategies being developed as our understanding of their respective underlying molecular pathogenesis increases. Treatment in utero has several distinct advantages to postnatal treatment. Biologic and physiologic phenomena enable the delivery of a higher effective dose, generation of immune tolerance, and the prevention of phenotypic onset for genetic diseases. Therapeutic technology for IUGT including CRISPR-Cas9 systems, zinc finger nucleases (ZFN), and peptide nucleic acids (PNAs) has already shown promise in animal models and early postnatal clinical trials. While the ability to detect fetal diagnoses has dramatically improved with developments in ultrasound and next-generation sequencing, treatment options remain experimental, with several translational gaps remaining prior to implementation in the clinical realm. Complicating this issue, the potential diseases targeted by this approach are often debilitating and would otherwise prove fatal if not treated in some manner. The leap from small animals to large animals, and subsequently, to humans will require further vigorous testing of safety and efficacy.

Delivery technologies for in utero gene therapy

Advances in prenatal imaging, molecular diagnostic tools, and genetic screening have unlocked the possibility to treat congenital diseases in utero prior to the onset of clinical symptoms. While fetal surgery and in utero stem cell transplantation can be harnessed to treat specific structural birth defects and congenital hematological disorders, respectively, in utero gene therapy allows for phenotype correction of a wide range of genetic disorders within the womb. However, key challenges to realizing the broad potential of in utero gene therapy are biocompatibility and efficiency of intracellular delivery of transgenes. In this review, we outline the unique considerations to delivery of in utero gene therapy components and highlight advances in viral and non-viral delivery platforms that meet these challenges. We also discuss specialized delivery technologies for in utero gene editing and provide future directions to engineer novel delivery modalities for clinical translation of this promising therapeutic approach.

In utero Therapy for the Treatment of Sickle Cell Disease: Taking Advantage of the Fetal Immune System

Sickle Cell Disease (SCD) is an autosomal recessive disorder resulting from a β-globin gene missense mutation and is among the most prevalent severe monogenic disorders worldwide. Haematopoietic stem cell transplantation remains the only curative option for the disease, as most management options focus solely on symptom control. Progress in prenatal diagnosis and fetal therapeutic intervention raises the possibility of in utero treatment. SCD can be diagnosed prenatally in high-risk patients using chorionic villus sampling. Among the possible prenatal treatments, in utero stem cell transplantation (IUSCT) shows the most promise. IUSCT is a non-myeloablative, non-immunosuppressive alternative conferring various unique advantages and may also offer safer postnatal management. Fetal immunologic immaturity could allow engraftment of allogeneic cells before fetal immune system maturation, donor-specific tolerance and lifelong chimerism. In this review, we will discuss SCD, screening and current treatments. We will present the therapeutic rationale for IUSCT, examine the early experimental work and initial human experience, as well as consider primary barriers of clinically implementing IUSCT and the promising approaches to address them.

The Theoretical Basis of In Utero Hematopoietic Stem Cell Transplantation and Its Use in the Treatment of Blood Disorders

Since its conception, prenatal therapy has been successful in correction of mainly anatomical defects, although the range of application has been limited. Research into minimally invasive fetal surgery techniques and prenatal molecular diagnostics has facilitated the development of in utero stem cell transplantation (IUT)-a method of delivering healthy stem cells to the early gestation fetus with the hope of engraftment, proliferation, and migration to the appropriate hematopoietic compartment. An area of application that shows promise is the treatment of hematopoietic disorders like hemoglobinopathies. The therapeutic rationale of IUT with hematopoietic stem cells (HSCs) is based on the proposed advantages the fetal environment offers based on its unique physiology. These advantages include the immature immune system facilitating the development of donor-specific tolerance, the natural migration of endogenous hematopoietic cells providing space for homing and engraftment of donor cells, and the fetal environment providing HSCs with the same opportunity to survive and proliferate regardless of their origin (donor or host). Maternal immune tolerance to the fetus and placenta also implies that the maternal environment could be accepting of donor cells. In theory, the fetus is a perfect recipient for stem cell transplant. Clinically, however, IUT is yet to see widespread success calling into question these assumptions of fetal physiology. This review aims to discuss and evaluate research surrounding these key assumptions and the clinical success of IUT in the treatment of thalassemia.

Ionizable lipid nanoparticles for in utero mRNA delivery

Clinical advances enable the prenatal diagnosis of genetic diseases that are candidates for gene and enzyme therapies such as messenger RNA (mRNA)-mediated protein replacement. Prenatal mRNA therapies can treat disease before the onset of irreversible pathology with high therapeutic efficacy and safety due to the small fetal size, immature immune system, and abundance of progenitor cells. However, the development of nonviral platforms for prenatal delivery is nascent. We developed a library of ionizable lipid nanoparticles (LNPs) for in utero mRNA delivery to mouse fetuses. We screened LNPs for luciferase mRNA delivery and identified formulations that accumulate within fetal livers, lungs, and intestines with higher efficiency and safety compared to benchmark delivery systems, DLin-MC3-DMA and jetPEI. We demonstrate that LNPs can deliver mRNAs to induce hepatic production of therapeutic secreted proteins. These LNPs may provide a platform for in utero mRNA delivery for protein replacement and gene editing.

Gene and Stem Cell Therapies for Fetal Care: A Review

Importance

Gene and stem cell therapies have become viable therapeutic options for many postnatal disorders. For select conditions, prenatal application would provide improved outcomes. The fetal state allows for several theoretical advantages over postnatal therapy, including immune immaturity and cellular niche accessibility.

Observations

Advances in prenatal diagnostic accuracy and surgical precision, as well as improvements in stem cell and gene therapy methods, have made prenatal gene and stem cell therapy realistic. Studies in mouse models and early human trials demonstrate the feasibility of these approaches. Additional efforts are under way to streamline fetal applications of stem cell and gene therapy while carefully considering best ethical practice and following established regulatory pathways.

Conclusions and Relevance

Fetal stem cell and gene therapy bring important therapeutic opportunities for select disorders that present in the fetal and neonatal periods. While this field is in its infancy, these therapies are starting to be available clinically, and clinicians should be aware of their benefits and challenges.

Lysosomal storage disease spectrum in nonimmune hydrops fetalis: a retrospective case control study

OBJECTIVES

Nonimmune hydrops fetalis (NIHF) accounts for 90% of hydrops fetalis cases. About 15% to 29% of unexplained NIHF cases are caused by lysosomal storage diseases (LSD). We review the spectrum of LSD and associated clinical findings in NIHF in a cohort of patients referred to our institution.

METHODS

We present a retrospective case-control study of cases with NIHF referred for LSD biochemical testing at a single center. Cases diagnosed with LSD were matched to controls with NIHF and negative LSD testing and analyzed according to the STROBE criteria to the extent the retrospective nature of this study allowed.

RESULTS

Between January 2006 and December 2018, 28 patients with NIHF were diagnosed with a LSD. Eight types of LSD were diagnosed: galactosialidosis 8/28 (28.6%), sialic acid storage disease (SASD) 5/28 (17.9%), mucopolysaccharidosis VII 5/28 (17.9%), Gaucher 4/28 (14.3%), sialidosis 2/28 (7.1%), GM1 gangliosidosis 2/28 (7.1%), Niemann-Pick disease type C 1/28 (3.6%), and mucolipidosis II/III 1/28 (3.6%). Associated clinical features were hepatomegaly 16/21 (76.2%) vs 22/65 (33.8%), P < .05, splenomegaly 12/20 (60.0%) vs 14/58 (24.1%), P < .05, and hepatosplenomegaly 10/20 (50.0%) vs 13/58 (22.4%) P < .05.

CONCLUSION

The most common LSD in NIHF were galactosialidosis, SASD, mucopolysaccharidosis VII, and Gaucher disease. LSD should be considered in unexplained NIHF cases, particularly if hepatomegaly, splenomegaly, or hepatosplenomegaly is visualized on prenatal ultrasound.

Defining the Optimal FVIII Transgene for Placental Cell-Based Gene Therapy to Treat Hemophilia A

The delivery of factor VIII (FVIII) through gene and/or cellular platforms has emerged as a promising hemophilia A treatment. Herein, we investigated the suitability of human placental cells (PLCs) as delivery vehicles for FVIII and determined an optimal FVIII transgene to produce/secrete therapeutic FVIII levels from these cells. Using three PLC cell banks we demonstrated that PLCs constitutively secreted low levels of FVIII, suggesting their suitability as a transgenic FVIII production platform. Furthermore, PLCs significantly increased FVIII secretion after transduction with a lentiviral vector (LV) encoding a myeloid codon-optimized bioengineered FVIII containing high-expression elements from porcine FVIII. Importantly, transduced PLCs did not upregulate cellular stress or innate immunity molecules, demonstrating that after transduction and FVIII production/secretion, PLCs retained low immunogenicity and cell stress. When LV encoding five different bioengineered FVIII transgenes were compared for transduction efficiency, FVIII production, and secretion, data showed that PLCs transduced with LV encoding hybrid human/porcine FVIII transgenes secreted substantially higher levels of FVIII than did LV encoding B domain-deleted human FVIII. In addition, data showed that in PLCs, myeloid codon optimization is needed to increase FVIII secretion to therapeutic levels. These studies have identified an optimal combination of FVIII transgene and cell source to achieve clinically meaningful levels of secreted FVIII.

Fetal gene therapy and pharmacotherapy to treat congenital hearing loss and vestibular dysfunction

Disabling hearing loss is expected to affect over 900 million people worldwide by 2050. The World Health Organization estimates that the annual economic impact of hearing loss globally is US$ 750 billion. The inability to hear may complicate effective interpersonal communication and negatively impact personal and professional relationships. Recent advances in the genetic diagnosis of inner ear disease have keenly focused attention on strategies to restore hearing and balance in individuals with defined gene mutations. Mouse models of human hearing loss serve as the primary approach to test gene therapies and pharmacotherapies. The goal of this review is to articulate the rationale for fetal gene therapy and pharmacotherapy to treat congenital hearing loss and vestibular dysfunction. The differential onset of hearing in mice and humans suggests that a prenatal window of therapeutic efficacy in humans may be optimal to restore sensory function. Mouse studies demonstrating the utility of early fetal intervention in the inner ear show promise. We focus on the modulation of gene expression through two strategies that have successfully treated deafness in animal models and have had clinical success for other conditions in humans: gene replacement and antisense oligonucleotide-mediated modulation of gene expression. The recent establishment of effective therapies targeting the juvenile and adult mouse provide informative counterexamples where intervention in the maturing and fully functional mouse inner ear may be effective. Distillation of the current literature leads to the conclusion that novel therapeutic strategies to treat genetic deafness and imbalance will soon translate to clinical trials.

Engraftment potential of maternal adipose-derived stem cells for fetal transplantation

Advances in prenatal molecular testing have made it possible to diagnose most genetic disorders early in gestation. In utero mesenchymal stem cell (MSC) therapy can be a powerful tool to cure the incurable. With this in mind, this method could ameliorate potential physical and functional damage. However, the presence of maternal T cells trafficking in the fetus during pregnancy is thought to be the major barrier to achieving the engraftment into the fetus. We investigated the possibility of using maternal adipose-derived stem cells (ADSCs) for in utero transplantation to improve engraftment, thus lowering the risk of graft rejection. Herein, fetal brain engraftment using congenic and maternal ADSC grafts was examined via in utero stem cell transplantation in a mouse model. ADSCs were purified using the mesenchymal stem cell markers, PDGFRα, and Sca-1 via fluorescence-activated cell sorting. The PDGFRα⁺Sca-1⁺ ADSCs were transplanted into the fetal intracerebroventricular (ICV) at E14.5. The transplanted grafts grew for at least 28 days after in utero transplantation with PDGFRα⁺Sca-1⁺ ADSC, and mature neuronal markers were also detected in the grafts. Furthermore, using the maternal sorted ADSCs suppressed the innate immune response, preventing the infiltration of CD8 T cells into the graft. Thus, in utero transplantation into the fetal ICV with the maternal PDGFRα⁺Sca-1⁺ ADSCs may be beneficial for the treatment of congenital neurological diseases because of the ability to reduce the responses after in utero stem cell transplantation and differentiate into neuronal lineages.

Clonal isolation of endothelial colony-forming cells from early gestation chorionic villi of human placenta for fetal tissue regeneration

BACKGROUND

Endothelial colony-forming cells (ECFCs) have been implicated in the process of vascularization, which includes vasculogenesis and angiogenesis. Vasculogenesis is a de novo formation of blood vessels, and is an essential physiological process that occurs during embryonic development and tissue regeneration. Angiogenesis is the growth of new capillaries from pre-existing blood vessels, which is observed both prenatally and postnatally. The placenta is an organ composed of a variety of fetal-derived cells, including ECFCs, and therefore has significant potential as a source of fetal ECFCs for tissue engineering.

AIM

To investigate the possibility of isolating clonal ECFCs from human early gestation chorionic villi (CV-ECFCs) of the placenta, and assess their potential for tissue engineering.

METHODS

The early gestation chorionic villus tissue was dissociated by enzyme digestion. Cells expressing CD31 were selected using magnetic-activated cell sorting, and plated in endothelial-specific growth medium. After 2-3 wks in culture, colonies displaying cobblestone-like morphology were manually picked using cloning cylinders. We characterized CV-ECFCs by flow cytometry, immunophenotyping, tube formation assay, and Dil-Ac-LDL uptake assay. Viral transduction of CV-ECFCs was performed using a Luciferase/tdTomato-containing lentiviral vector, and transduction efficiency was tested by fluorescent microscopy and flow cytometry. Compatibility of CV-ECFCs with a delivery vehicle was determined using an FDA approved, small intestinal submucosa extracellular matrix scaffold.

RESULTS

After four passages in 6-8 wks of culture, we obtained a total number of 1.8 × 10⁷ CV-ECFCs using 100 mg of early gestational chorionic villus tissue. Immunophenotypic analyses by flow cytometry demonstrated that CV-ECFCs highly expressed the endothelial markers CD31, CD144, CD146, CD105, CD309, only partially expressed CD34, and did not express CD45 and CD90. CV-ECFCs were capable of acetylated low-density lipoprotein uptake and tube formation, similar to cord blood-derived ECFCs (CB-ECFCs). CV-ECFCs can be transduced with a Luciferase/tdTomato-containing lentiviral vector at a transduction efficiency of 85.1%. Seeding CV-ECFCs on a small intestinal submucosa extracellular matrix scaffold confirmed that CV-ECFCs were compatible with the biomaterial scaffold.

CONCLUSION

In summary, we established a magnetic sorting-assisted clonal isolation approach to derive CV-ECFCs. A substantial number of CV-ECFCs can be obtained within a short time frame, representing a promising novel source of ECFCs for fetal treatments.

Genetic Engineering to Induce Fetal-Like Hematopoietic Stem Cells

Bone marrow transplantation (BMT) or hematopoietic stem cell transplantation (HSCT) is an archetype of cellular therapy. However, to date BMT still suffers from several complications. Recent technological advances have encouraged us to think about an alternative to traditional BMT. Specifically, we propose in utero HSCT (IUHSCT). For this purpose, we suggest that induced fetal-like hematopoietic stem cells (ifHSCs) might be suitable for IUHSCT, and should be seriously evaluated.

Mechanistic Insights into Factor VIII Immune Tolerance Induction via Prenatal Cell Therapy in Hemophilia A

Purpose of Review

Prenatal stem cell and gene therapy approaches are amongst the few therapies that can promise the birth of a healthy infant with specific known genetic diseases. This review describes fetal immune cell signaling and its potential influence on donor cell engraftment, and summarizes mechanisms of central T cell tolerance to peripherally-acquired antigen in the context of prenatal therapies for Hemophilia A.

Recent Findings

During early gestation, different subsets of antigen presenting cells take up peripherally-acquired, non-inherited antigens and induce the deletion of antigen-reactive T-cell precursors in the thymus, demonstrating the potential for using prenatal cell and gene therapies to induce central tolerance to FVIII in the context of prenatal diagnosis/therapy of Hemophilia A.

Summary

Prenatal cell and gene therapies are promising approaches to treat several genetic disorders including Hemophilia A and B. Understanding the mechanisms of how FVIII-specific tolerance is achieved during ontogeny could help develop novel therapies for HA and better approaches to overcome FVIII inhibitors.

Future AAVenues for In Utero Gene Therapy

Fetal gene therapy using safe and effective viral vectors no longer remains a distant prospect. Recently in Nature Medicine, Massaro et al. (2018) demonstrated that prenatal intracranial injection of a viral vector results in improved neurologic function, raising the intriguing possibility that in utero gene therapy may be approaching clinical applications.

Ethical development of stem-cell-based interventions

The process of developing new and complex stem-cell-based therapeutics is incremental and requires decades of sustained collaboration among different stakeholders. In this Perspective, we address key ethical and policy challenges confronting the clinical translation of stem-cell-based interventions (SCBIs), including premature diffusion of SCBIs to clinical practice, assessment of risk in trials, obtaining valid informed consent for research participants, balanced and complete scientific reporting and public communications, regulation, and equitable access to treatment. We propose a way forward for translating these therapies with the above challenges in mind.

Assessment of Short-Term Engraftment Potential of Ex Vivo Expanded Hematopoietic Stem Cells Using Normal Fetal Mouse in Utero Transplantation Model

Objective

Ex vivo expansion is a promising strategy to overcome the low number of human umbilical cord blood hematopoietic stem cells (hUCB-HSCs). Although based on the obtained results in unnatural physiological condition of irradiated genetically immune-deficient mouse models, there has always been concern that the expanded cells have less engraftment potential. The purpose of this study was to investigate effect of common ex vivo expansion method on engraftment potential of hUCB-mononuclear cells (MNCs), using normal fetal mouse, as a model with more similarity to human physiological conditions.

Materials and Methods

In this experimental study, briefly, isolated hUCB-MNCs were cultured in common expansion medium containing stem cell factor, Flt3 ligand and thrombopoietin. The unexpanded and expanded cells were transplanted to the fetal mice on gestational days of 11.5-13.5. After administration of human hematopoiesis growth factors (hHGFs), presence of human CD45⁺ cells, in the peripheral blood of recipients, was assessed at various time points after transplantation.

Results

The expanded MNCs showed 32-fold increase in the expression of CD34⁺38^- phenotype and about 3-fold higher clonogenic potential as compared to the uncultured cells. Four weeks after transplantation, 73% (19/26) of expanded-cell recipients and 35% (7/20) of unexpanded-cell recipients were found to be successfully engrafted with human CD45⁺ cells. The engraftment level of expanded MNCs was significantly (1.8-fold) higher than unexpanded cells. After hHGFs administration, the level was increased to 3.2, 3.8 and 2.6-fold at respectively 8, 12, and 16 weeks of post transplantation. The increased expression of CXCR4 protein in expanded MNCs is a likely explanation for the present findings.

Conclusion

The presented data showed that expanded MNCs compared to unexpended cells are capable of more rapid and higher short-term engraftment in normal fetal mouse. It could also be suggested that in utero transplantation (IUT) of normal fetal mice could be an appropriate substitute for NOD/SCID mice in xenotransplantation studies.

Embryonic intraventricular transplantation of neural stem cells augments inflammation-induced prenatal brain injury

OBJECTIVE

Prenatal brain injury results from undesirable circumstances during the embryonic development. Current endeavors for treating this complication are basically excluded to postnatal therapeutic approaches. Neural stem cell therapy has shown great promise for treating neurodevelopmental disorders. To our knowledge, this is the first study that investigates the therapeutic effect of in utero transplantation of neural stem cells (NSCs) in inflammation model of prenatal brain injury.

METHODS

To induce prenatal injury, time-mated C57BL6J mice were intraperitoneally injected with 50 μg/kg lipopolysaccharide (LPS(on the day 15 of gestation. In the treatment group, NSCs were transplanted into the lateral ventricle of embryos on day 17 of gestation. The expression of GFAP, Iba-1, Olig2, and NeuN were assessed by real time PCR and immunohistochemistry. Changes in IL-6, TNF-α and IL-10 cytokines level, and caspase 3 activity were evaluated in the cortex of pups.

RESULTS

Intrauterine transplanted NSCs homed to the brain cortex of offspring. Brain levels of pro-inflammatory cytokines showed a significant downward trend in the NSCs group. Furthermore, NSCs ameliorated inflammation-induced reactive microgliosis and astrogliosis as well as cellular degeneration. Apoptosis inhibition in the treated group was demonstrated by the decline in the caspase 3 activity and dark neurons.

CONCLUSION

This study suggests a promising prospect to initiate the treatment of prenatal brain injury before birth by intrauterine transplantation of NSCs.

In utero nanoparticle delivery for site-specific genome editing

Genetic diseases can be diagnosed early during pregnancy, but many monogenic disorders continue to cause considerable neonatal and pediatric morbidity and mortality. Early intervention through intrauterine gene editing, however, could correct the genetic defect, potentially allowing for normal organ development, functional disease improvement, or cure. Here we demonstrate safe intravenous and intra-amniotic administration of polymeric nanoparticles to fetal mouse tissues at selected gestational ages with no effect on survival or postnatal growth. In utero introduction of nanoparticles containing peptide nucleic acids (PNAs) and donor DNAs corrects a disease-causing mutation in the β-globin gene in a mouse model of human β-thalassemia, yielding sustained postnatal elevation of blood hemoglobin levels into the normal range, reduced reticulocyte counts, reversal of splenomegaly, and improved survival, with no detected off-target mutations in partially homologous loci. This work may provide the basis for a safe and versatile method of fetal gene editing for human monogenic disorders.

Maternal and Fetal Immune Response to in Utero Stem Cell Transplantation

Purpose of Review

In Utero Hematopoietic Cellular Transplantation (IUHCT) is a promising intervention for the non-toxic treatment of congenital disease that hinges on the assumption of fetal immunologic immaturity and an inability to reject a hematopoietic allograft. However, clinical IUCHT has failed except in cases where the fetus is severely immunocompromised. The current review examines recent studies of engraftment barriers stemming from either the fetal or maternal immune system.

Recent Findings

New reports have illuminated roles for maternal humoral and cellular immunity and fetal innate cellular immunity in the resistance to allogeneic IUHCT. These experimental findings have inspired new approaches to overcome these barriers. Despite these advances, postulates regarding a maternal immune barrier to IUHCT provide an inadequate explanation for the well-documented clinical success only in the treatment of fetal immunodeficiency with normal maternal immunity.

Summary

Characterization of the maternal and fetal immune response to allogeneic IUHCT provides new insight into the complexity of prenatal tolerance. Future work in this area should aim to provide a unifying explanation for the observed patterns of success and failure with clinical IUHCT.

Recent advances in understanding hematopoiesis in Fanconi Anemia

Fanconi anemia is an inherited disease characterized by genomic instability, hypersensitivity to DNA cross-linking agents, bone marrow failure, short stature, skeletal abnormalities, and a high relative risk of myeloid leukemia and epithelial malignancies. The 21 Fanconi anemia genes encode proteins involved in multiple nuclear biochemical pathways that effect DNA interstrand crosslink repair. In the past, bone marrow failure was attributed solely to the failure of stem cells to repair DNA. Recently, non-canonical functions of many of the Fanconi anemia proteins have been described, including modulating responses to oxidative stress, viral infection, and inflammation as well as facilitating mitophagic responses and enhancing signals that promote stem cell function and survival. Some of these functions take place in non-nuclear sites and do not depend on the DNA damage response functions of the proteins. Dysfunctions of the canonical and non-canonical pathways that drive stem cell exhaustion and neoplastic clonal selection are reviewed, and the potential therapeutic importance of fully investigating the scope and interdependences of the canonical and non-canonical pathways is emphasized.

Gene Therapy: A Paradigm Shift in Dentistry

Gene therapy holds a promising future for bridging the gap between the disciplines of medicine and clinical dentistry. The dynamic treatment approaches of gene therapy have been advancing by leaps and bounds. They are transforming the conventional approaches into more precise and preventive ones that may limit the need of using drugs and surgery. The oral cavity is one of the most accessible areas for the clinical applications of gene therapy for various oral tissues. The idea of genetic engineering has become more exciting due to its advantages over other treatment modalities. For instance, the body is neither subjected to an invasive surgery nor deep wounds, nor is it susceptible to systemic effects of drugs. The aim of this article is to review the gene therapy applications in the field of dentistry. In addition, therapeutic benefits in terms of treatment of diseases, minimal invasion and maximum outcomes have been discussed.