Non-invasive gene targeting to the fetal brain after intravenous administration and transplacental transfer of plasmid DNA using PEGylated immunoliposomes

Exosomes as an Emerging Plasmid Delivery Vehicle for Gene Therapy

Despite its introduction more than three decades ago, gene therapy has fallen short of its expected potential for the treatment of a broad spectrum of diseases and continues to lack widespread clinical use. The fundamental limitation in clinical translatability of this therapeutic modality has always been an effective delivery system that circumvents degradation of the therapeutic nucleic acids, ensuring they reach the intended disease target. Plasmid DNA (pDNA) for the purpose of introducing exogenous genes presents an additional challenge due to its size and potential immunogenicity. Current pDNA methods include naked pDNA accompanied by electroporation or ultrasound, liposomes, other nanoparticles, and cell-penetrating peptides, to name a few. While the topic of numerous reviews, each of these methods has its own unique set of limitations, side effects, and efficacy concerns. In this review, we highlight emerging uses of exosomes for the delivery of pDNA for gene therapy. We specifically focus on bovine milk and colostrum-derived exosomes as a nano-delivery "platform". Milk/colostrum represents an abundant, scalable, and cost-effective natural source of exosomes that can be loaded with nucleic acids for targeted delivery to a variety of tissue types in the body. These nanoparticles can be functionalized and loaded with pDNA for the exogenous expression of genes to target a wide variety of disease phenotypes, overcoming many of the limitations of current gene therapy delivery techniques.

Recent Genome-Editing Approaches toward Post-Implanted Fetuses in Mice

Genome editing, as exemplified by the CRISPR/Cas9 system, has recently been employed to effectively generate genetically modified animals and cells for the purpose of gene function analysis and disease model creation. There are at least four ways to induce genome editing in individuals: the first is to perform genome editing at the early preimplantation stage, such as fertilized eggs (zygotes), for the creation of whole genetically modified animals; the second is at post-implanted stages, as exemplified by the mid-gestational stages (E9 to E15), for targeting specific cell populations through in utero injection of viral vectors carrying genome-editing components or that of nonviral vectors carrying genome-editing components and subsequent in utero electroporation; the third is at the mid-gestational stages, as exemplified by tail-vein injection of genome-editing components into the pregnant females through which the genome-editing components can be transmitted to fetal cells via a placenta-blood barrier; and the last is at the newborn or adult stage, as exemplified by facial or tail-vein injection of genome-editing components. Here, we focus on the second and third approaches and will review the latest techniques for various methods concerning gene editing in developing fetuses.

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.

Diseases and conditions that impact maternal and fetal health and the potential for nanomedicine therapies

Maternal mortality rates in the United States have steadily increased since 1987 to the current rate of over 16 deaths per 100,000 live births. Whereas most of these deaths are related to an underlying condition, such as cardiovascular disease, many pregnant women die from diseases that emerge as a consequence of pregnancy. Both pre-existing and emergent diseases and conditions are difficult to treat in pregnant women because of the potential harmful effects of the treatment on the developing fetus. Often the health of the woman and the health of the baby are at odds and must be weighed against each other when medical treatment is needed, frequently leading to iatrogenic preterm birth. However, the use of engineered nanomedicines has the potential to fill the treatment gap for pregnant women. This review describes several conditions that may afflict pregnant women and fetuses and introduces how engineered nanomedicines may be used to treat these illnesses. Although the field of maternal-fetal nanomedicine is in its infancy, with additional research and development, engineered nanotherapeutics may greatly improve outcomes for pregnant women and their offspring in the future.

Exploiting the placenta for nanoparticle-mediated drug delivery during pregnancy

A major challenge to treating diseases during pregnancy is that small molecule therapeutics are transported through the placenta and incur toxicities to the developing fetus. The placenta is responsible for providing nutrients, removing waste, and protecting the fetus from toxic substances. Thus, the placenta acts as a biological barrier between the mother and fetus that can be exploited for drug delivery. Nanoparticle technologies provide the opportunity for safe drug delivery during pregnancy by controlling how therapeutics interact with the placenta. In this Review, we present nanoparticle drug delivery technologies specifically designed to exploit the placenta as a biological barrier to treat maternal, placental, or fetal diseases exclusively, while minimizing off-target toxicities. Further, we discuss opportunities, challenges, and future directions for implementing drug delivery technologies during pregnancy.

Design of nanomaterials for applications in maternal/fetal medicine

Pregnancy complications are commonplace and the challenges of treatment during pregnancy with few options available pose a risk to the health of both the mother and baby. Patients suffering from conditions such as preeclampsia, placenta accreta, and intrauterine growth restriction have few treatment options apart from emergency caesarean section. Fortunately, researchers are beginning to develop nanomedicine-based therapies that could be utilized to treat conditions affecting the mother, placenta, or fetus to improve the prognosis for mothers and their unborn children. This review summarizes the field's current understanding of nanoparticle biodistribution and therapeutic effect following systemic or vaginal administration and overviews the design parameters researchers should consider when developing nanomedicines for maternal/fetal health. It also describes safety considerations for nanomedicines to limit undesirable maternal or fetal side effects and discusses future work that should be performed to advance nanomedicine for maternal/fetal health. With additional development and implementation, the application of nanomedicine to treat pregnancy complications may mitigate the need for emergency caesarean sections and allow pregnancies to extend to term.

Plasmid DNA gene therapy of the Niemann-Pick C1 mouse with transferrin receptor-targeted Trojan horse liposomes

Niemann-Pick C1 (NPC1) is a lysosomal cholesterol storage disorder, that severely affects the brain, and is caused by mutations in the NPC1 gene, which encodes an intracellular membrane transporter of non-esterified cholesterol. Therapeutic options for NPC1 are few, and classical enzyme replacement therapy with the recombinant protein is not possible as the NPC1 gene product is an insoluble membrane protein, which increases the need for development of gene therapy for NPC1. While viral based gene therapy is under development, it is important to investigate alternative approaches to brain gene therapy without viral vectors. The present work develops a plasmid DNA approach to gene therapy of NPC1 using Trojan horse liposomes (THLs), wherein the plasmid DNA is encapsulated in 100 nm pegylated liposomes, which are targeted to organs with a monoclonal antibody against the mouse transferrin receptor. THLs were encapsulated with a 8.0 kb plasmid DNA encoding the 3.9 kb human NPC1 open reading frame, under the influence of a 1.5 kb platelet derived growth factor B (PDGFB) promoter. THLs were administered weekly beginning at 6–7 weeks in the NPC1^−/− null mouse, and delivery of the plasmid DNA, and NPC1 mRNA expression in brain, spleen, and liver were confirmed by quantitative PCR. THL treatment reduced tissue inclusion bodies in brain, and peripheral organs, but did not prolong lifespan in these mice. The work suggests that early treatment after birth may be required to reverse this disease model with NPC1 gene replacement therapy.

Transplacental Gene Delivery (TPGD) as a Noninvasive Tool for Fetal Gene Manipulation in Mice

Transplacental gene delivery (TPGD) is a technique for delivering nucleic acids to fetal tissues via tail-vein injections in pregnant mice. After transplacental transport, administered nucleic acids enter fetal circulation and are distributed among fetal tissues. TPGD was established in 1995 by Tsukamoto et al., and its mechanisms, and potential applications have been further characterized since. Recently, discoveries of sequence specific nucleases, such as zinc-finger nuclease (ZFN), transcription activator-like effector nucleases (TALEN), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) (CRISPR/Cas9), have revolutionized genome editing. In 2019, we demonstrated that intravenous injection of plasmid DNA containing CRISPR/Cas9 produced indels in fetal myocardial cells, which are comparatively amenable to transfection with exogenous DNA. In the future, this unique technique will allow manipulation of fetal cell functions in basic studies of fetal gene therapy. In this review, we describe developments of TPGD and discuss their applications to the manipulation of fetal cells.

Transplacental delivery of genome editing components causes mutations in embryonic cardiomyocytes of mid-gestational murine fetuses

Genome editing, as exemplified by CRISPR/Cas9, is now recognized as a powerful tool for the engineering of endogenous target genes. It employs only two components, namely, Cas9 in the form of DNA, mRNA, or protein; and guide RNA (gRNA), which is specific to a target gene. When these components are transferred to cells, they create insertion/deletion mutations (indels) within a target gene. Therefore, when fetuses within the uteri of pregnant murine females are exposed to these reagents, fetal cells incorporating them should show mutations in the target gene. To examine a possible genome editing of fetal cells in vivo, we intravenously administered a solution containing plasmid DNA-FuGENE complex to pregnant wild-type female mice [which had been successfully mated with enhanced green fluorescent protein (EGFP)-expressing male transgenic mice] on day 12.5 of gestation. The plasmid DNA induces the expression of gRNA, which was targeted at the EGFP cDNA, and that of the Cas9 gene. All fetuses in the pregnant females should express EGFP systemically, since they are heterozygous (Tg/+) for the transgene. Thus, the delivery of CRISPR system targeted at EGFP in the fetuses will cause a reduced expression of EGFP as a result of the genome editing of EGFP genomic sequence. Of the 24 fetuses isolated from three pregnant females 2 days after gene delivery, 3 were found to have reduced fluorescence in their hearts. Genotyping of the dissected hearts revealed the presence of the transgene construct (Cas9 gene) in all the samples. Furthermore, all the three samples exhibited mutations at the target loci, although normal cells were also present. Thus, transplacental delivery of gene editing components may be a useful tool for developing animal models with heart disorder for heart-related disease research, and gene therapy in congenital heart defects such as hypertrophic cardiomyopathy (HCM). © 2019 IUBMB Life, 9999(9999):1-10, 2019.