Early intra-amniotic gene transfer using lentiviral vector improves skin blistering phenotype in a murine model of Herlitz junctional epidermolysis bullosa

Gene modification therapies for hereditary diseases in the fetus

Proof-of-principle disease models have demonstrated the feasibility of an intrauterine gene modification therapy (in utero gene therapy (IUGT)) approach to hereditary diseases as diverse as coagulation disorders, haemoglobinopathies, neurogenetic disorders, congenital metabolic, and pulmonary diseases. Gene addition, which requires the delivery of an integrating or episomal transgene to the target cell nucleus to be transcribed, and gene editing, where the mutation is corrected within the gene of origin, have both been used successfully to increase normal protein production in a bid to reverse or arrest pathology in utero. While most experimental models have employed lentiviral, adenoviral, and adeno-associated viral vectors engineered to efficiently enter target cells, newer models have also demonstrated the applicability of non-viral lipid nanoparticles. Amelioration of pathology is dependent primarily on achieving sustained therapeutic transgene expression, silencing of transgene expression, production of neutralising antibodies, the dilutional effect of the recipient's growth on the mass of transduced cells, and the degree of pre-existing cellular damage. Safety assessment of any IUGT strategy will require long-term postnatal surveillance of both the fetal recipient and the maternal bystander for cell and genome toxicity, oncogenic potential, immune-responsiveness, and germline mutation. In this review, we discuss advances in the field and the push toward clinical translation of IUGT.

Prenatal Gene Therapy for Metabolic Disorders

Gene therapy has traditionally involved the delivery of exogenous genetic material to a cell-most commonly to replace defective genes causing monogenic disorders. This allows cells to produce proteins that are otherwise absent in sufficient quantities, ideally for a therapeutic purpose. Since its inception over 40 years ago, the field of gene therapy has significantly expanded and now includes targeted gene editing strategies, including, but not limited to, clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), transcription activator-like effector nucleases (TALENs), and zinc-finger nucleases (ZFNs).

The Future of In Utero Gene Therapy

Significant advances in the safety and efficacy of gene therapy have sparked a new frontier in therapeutics for genetic diseases as evidenced by the greater than 700 active gene therapy investigational new drug applications reported by the NIH and the US Food and Drug Association. Although postnatal gene therapy trials are encouraging, limitations to effective therapy including an immune barrier and initiation of treatment after disease onset can exist. Advances in prenatal diagnostics provide hope that many genetic abnormalities will be able to be diagnosed before birth. Prenatal gene therapy has the potential to take advantage of normal developmental properties of the fetus and overcome some of the current limitations to efficient postnatal gene therapy. The rationale for prenatal gene therapy includes the small fetal size, the tolerogenic fetal immune system, the presence of highly proliferative and accessible stem/progenitor cells of multiple organs, and, ultimately, the ability to treat diseases in which irreversible pathology begins prior to birth. This rationale is based on and supported by a number of published animal studies. Unique ethical considerations exist in the context of prenatal gene therapy, including the importance of rigorous evaluation of the effect of the therapy on fetal germ cells and developing organs as well as the mother. To date, animal studies have not demonstrated any significant germline or maternal effect of prenatal gene therapy. Finally, practical considerations of future clinical prenatal gene therapy will include, but not be limited to, determining the initial target disease characteristics and the importance of non-directive prenatal counseling of families carrying a fetus with a genetic diagnosis.

Transamniotic mesenchymal stem cell therapy for neural tube defects preserves neural function through lesion-specific engraftment and regeneration

Neural tube defects (NTDs) lead to prenatal mortality and lifelong morbidity. Currently, surgical closure of NTD lesions results in limited functional recovery. We previously suggested that nerve regeneration was critical for NTD therapy. Here, we report that transamniotic bone marrow-derived mesenchymal stem cell (BMSC) therapy for NTDs during early development may achieve beneficial functional recovery. In our ex vivo rat embryonic NTD model, BMSCs injected into the amniotic cavity spontaneously migrated into the defective neural tissue. Hepatocyte growth factor and its receptor c-MET were found to play critical roles in this NTD lesion-specific migration. Using the in vivo rat fetal NTD model, we further discovered that the engrafted BMSCs specifically differentiated into the cell types of the defective tissue, including skin and different types of neurons in situ. BMSC treatment triggered skin repair in fetuses, leading to a 29.9 ± 5.6% reduction in the skin lesion area. The electrophysiological functional recovery assay revealed a decreased latency and increased motor-evoked potential amplitude in the BMSC-treated fetuses. Based on these positive outcomes, ease of operation, and reduced trauma to the mother and fetus, we propose that transamniotic BMSC administration could be a new effective therapy for NTDs.

Therapeutic potential of adenovirus-encoding brain-derived neurotrophic factor for spina bifida aperta by intra-amniotic delivery in a rat model

Spina bifida aperta is a type of neural tube defect (NTD). Although prenatal fetal surgery has been an available and effective treatment for it, the neurological functional recovery is still need to be enhanced. Our previous results revealed that deficiencies of sensory, motor, and parasympathetic neurons were primary anomalies that occurred with the spinal malformation. Therefore, we emphasized that nerve regeneration is critical for NTD therapy. We delivered an adenoviral construct containing genes inserted for green fluorescent protein and brain-derived neurotrophic factor (Ad-GFP-BDNF) into the amniotic fluid to investigate its prenatal therapeutic potential for rat fetuses with spina bifida aperta. Using immunofluorescence, TdT-mediated dUTP nick-end labeling staining, and real-time polymerase chain reaction analysis, we assessed cell apoptosis in the defective spinal cord and Brn3a positive neuron survival in the dorsal root ganglion (DRG); a protein array was used to investigate the microenvironmental changes of the amniotic fluid. We found that most of the overexpressed BDNF was present on the lesions of the spina bifida fetuses, the number of apoptosis cells in Ad-GFP-BDNF-transfected spinal cords were reduced, mRNA levels of Bcl2/Bax were upregulated and Casp3 were downregulated compared with the controls, the proportion of Brn3a positive neurons in DRG were increased by activating the BDNF/TrkB/Akt signaling pathway, and most of the significant changes in cytokines in the amniotic fluid were related to the biological processes of regulation of apoptotic process and generation of neurons. These results suggest that intra-amniotic Ad-GFP-BDNF gene delivery might have potential as a supplementary approach to treat congenital malformations of neural tubes.

In Utero Gene Therapy (IUGT) Using GLOBE Lentiviral Vector Phenotypically Corrects the Heterozygous Humanised Mouse Model and Its Progress Can Be Monitored Using MRI Techniques

In utero gene therapy (IUGT) to the fetal hematopoietic compartment could be used to treat congenital blood disorders such as β-thalassemia. A humanised mouse model of β-thalassemia was used, in which heterozygous animals are anaemic with splenomegaly and extramedullary hematopoiesis. Intrahepatic in utero injections of a β globin-expressing lentiviral vector (GLOBE), were performed in fetuses at E13.5 of gestation. We analysed animals at 12 and 32 weeks of age, for vector copy number in bone marrow, peripheral blood liver and spleen and we performed integration site analysis. Compared to noninjected heterozygous animals IUGT normalised blood haemoglobin levels and spleen weight. Integration site analysis showed polyclonality. The left ventricular ejection fraction measured using magnetic resonance imaging (MRI) in treated heterozygous animals was similar to that of normal non-β-thalassemic mice but significantly higher than untreated heterozygous thalassemia mice suggesting that IUGT ameliorated poor cardiac function. GLOBE LV-mediated IUGT normalised the haematological and anatomical phenotype in a heterozygous humanised model of β-thalassemia.

Toward an orofacial gene regulatory network

Orofacial clefting is a common birth defect with significant morbidity. A panoply of candidate genes have been discovered through synergy of animal models and human genetics. Among these, variants in interferon regulatory factor 6 (IRF6) cause syndromic orofacial clefting and contribute risk toward isolated cleft lip and palate (1/700 live births). Rare variants in IRF6 can lead to Van der Woude syndrome (1/35,000 live births) and popliteal pterygium syndrome (1/300,000 live births). Furthermore, IRF6 regulates GRHL3 and rare variants in this downstream target can also lead to Van der Woude syndrome. In addition, a common variant (rs642961) in the IRF6 locus is found in 30% of the world's population and contributes risk for isolated orofacial clefting. Biochemical studies revealed that rs642961 abrogates one of four AP-2alpha binding sites. Like IRF6 and GRHL3, rare variants in TFAP2A can also lead to syndromic orofacial clefting with lip pits (branchio-oculo-facial syndrome). The literature suggests that AP-2alpha, IRF6 and GRHL3 are part of a pathway that is essential for lip and palate development. In addition to updating the pathways, players and pursuits, this review will highlight some of the current questions in the study of orofacial clefting.

In utero and exo utero fetal surgery on histogenesis of organs in animals

Until recently, fetal surgery was only used for fetuses with very poor prognosis who were likely to die without intervention. With advances in imaging, endoscopic techniques, anesthesia and novel interventions, fetal surgery is becoming a realistic option for conditions with less severe prognoses, where the aim is now to improve quality of life rather than simply allow survival. Until forty years ago, the uterus shielded the fetus from observation and therapy. Rapid changes in the diagnosis and treatment of human fetal anatomical abnormalities are due to improved fetal imaging studies, fetal sampling techniques (e.g., amniocentesis and chorionic villus sampling), and a better understanding of fetal pathophysiology derived from laboratory animals. Fetal therapy is the logical culmination of progress in fetal diagnosis. In other words, the fetus is now a patient. Now-a-days, in utero (IU) and exo utero (EU) surgical methods are popular for experimental analyses of the histogenesis of organ development. Using these surgical methods, developmental anomalies can be created and then repaired. By applying microinjection and/or fetal surgery with these methods, models of developmental anomalies such as neural tube defects, temporomandibular joint defects, hip joint defects, digit amputation, limb and digit development and regeneration, and tooth germ transplantation in the jaw could be created and later observed. After observing different types of anomalies, novel IU and EU surgical techniques would be the best approach for repairing or treating those anomalies or diseases. This review will focus on the rationale for the IU and EU creation of animal models of different organ defects or anomalies and their repair, based on analyses of organ histogenesis and pathologic observations. It will also focus in detail on the surgical techniques of both IU and EU methods.

Gene therapy for skin diseases

The skin possesses qualities that make it desirable for gene therapy, and studies have focused on gene therapy for multiple cutaneous diseases. Gene therapy uses a vector to introduce genetic material into cells to alter gene expression, negating a pathological process. This can be accomplished with a variety of viral vectors or nonviral administrations. Although results are promising, there are several potential pitfalls that must be addressed to improve the safety profile to make gene therapy widely available clinically.

The case for intrauterine gene therapy

Single-gene disorders can cause perinatal mortality or severe permanent morbidity. Intrauterine gene therapy seeks to correct the genetic defect in the early stages of pathogenesis through delivery of a vector system expressing the therapeutic transgene to the fetus. Advantages of intrauterine gene therapy include prevention of irreversible organ damage, potentially inducing central tolerance and wider bio-distribution, including the brain after delivery of vector. Already, proof-of-cure has been demonstrated in knockout animal models for several diseases. Long-term outcomes pertaining to efficacy and durability of transgene expression and safety are under investigation in clinically relevant non-human primate models. Bystander effects in the mother from transplacental vector trafficking require further assessment. In this chapter, we discuss the candidate diseases amenable to intrauterine gene therapy, current state-of-the-art evidence, and potential clinical applications.