Viral and non-viral gene delivery and its role in pluripotent stem cell engineering

Mutation-Directed Therapeutics for Neurofibromatosis Type I

Significant advances in biotechnology have led to the development of a number of different mutation-directed therapies. Some of these techniques have matured to a level that has allowed testing in clinical trials, but few have made it to approval by drug-regulatory bodies for the treatment of specific diseases. While there are still various hurdles to be overcome, recent success stories have proven the potential power of mutation-directed therapies and have fueled the hope of finding therapeutics for other genetic disorders. In this review, we summarize the state-of-the-art of various therapeutic approaches and assess their applicability to the genetic disorder neurofibromatosis type I (NF1). NF1 is caused by the loss of function of neurofibromin, a tumor suppressor and downregulator of the Ras signaling pathway. The condition is characterized by a variety of phenotypes and includes symptoms such as skin spots, nervous system tumors, skeletal dysplasia, and others. Hence, depending on the patient, therapeutics may need to target different tissues and cell types. While we also discuss the delivery of therapeutics, in particular via viral vectors and nanoparticles, our main focus is on therapeutic techniques that reconstitute functional neurofibromin, most notably cDNA replacement, CRISPR-based DNA repair, RNA repair, antisense oligonucleotide therapeutics including exon skipping, and nonsense suppression.

Targeted Delivery of Secretory Promelittin via Novel Poly(lactone-co-β-amino ester) Nanoparticles for Treatment of Breast Cancer Brain Metastases

Breast cancer brain metastases (BCBM) is a devastating disease with dismal prognosis. Although chemotherapy is widely used for clinical management of most tumors, it is often ineffective for BCBM. Therefore, alternative approaches for improved treatment of BCBM are in great demand. Here, an innovative gene therapy regimen is reported that is designed for effective treatment of BCBM. First, poly(lactone-co-β-amino ester) nanoparticles that are capable of efficient gene delivery are synthesized and are engineered for targeted delivery to BCBM through surface conjugation of AMD3100, which interacts with CXCR4 enriched in the tumor microenvironment. Next, an artificial gene, proMel, is designed for the expression of secretory promelittin protein, which has limited toxicity on its own but releases cytolytic melittin after activation by MMP-2 accumulated in tumors. It is demonstrated that delivery of the proMel via the AMD3100-conjugated nanoparticles effectively inhibits tumor progression in a BCBM mouse model. This study suggests a new direction to treat BCBM through targeted delivery of promelittin-mediated gene therapy.

Polylysine-modified polyethylenimine polymer can generate genetically engineered mesenchymal stem cells for combinational suicidal gene therapy in glioblastoma

Glioblastoma remains the most resistant malignant brain tumor owing to the lack of an efficient delivery system for therapeutic genes or drugs, especially in outgrowing tumor islands. Cell-based delivery systems such as mesenchymal stem cells (MSCs) are a potential candidate in this regard. Conventionally, MSCs have been genetically modified for cancer therapy by using viral vectors that can illicit oncogenicity and limit their use in clinical trials. In this study, we have used nonviral agents such as the polylysine-modified polyethylenimine (PEI-PLL) copolymer to generate genetically engineered MSCs with suicidal genes, namely, HSV-TK and TRAIL. Our results demonstrated that an intratumoral injection of polymer-double-transfected MSCs along with prodrug ganciclovir injections can induce a significant synergistic therapeutic response both in vitro and in vivo compared to single plasmid transfections or untransfected MSCs. The proliferation marker Ki67 and the angiogenesis marker VEGF were also significantly reduced in treatment groups, whereas the TUNEL assay demonstrated that apoptosis is significantly increased after treatment. Our findings suggest that the PEI-PLL copolymer can successfully modify MSCs with therapeutic genes and can produce a pronounced impact during glioblastoma therapy. This study proposes a potential nonviral approach to develop a cell-based therapy for the treatment of glioma. STATEMENT OF SIGNIFICANCE: In this study, we have used a polylysine-modified polyethylenimine polymer (PEI-PLL) copolymer, a non viral transfection agent, for gene delivery in mesenchymal stem cells. These PEI-PLL-transfected mesenchymal stem cells with HSV-TK and TRAIL genes have the potential to treat glioma both in vitro and in vivo. This combinational therapy through PEI-PLL-transfected mesenchymal stem cells can provide cost-effective, low immunogenic, and tumor-targeted delivery of suicideal genes (HSV-TK and TRAIL) for promising glioblastoma treatment.

Combining topographical and genetic cues to promote neuronal fate specification in stem cells

There is little remedy for the devastating effects resulting from neuronal loss caused by neural injury or neurodegenerative disease. Reconstruction of damaged neural circuitry with stem cell-derived neurons is a promising approach to repair these defects, but controlling differentiation and guiding synaptic integration with existing neurons remain significant unmet challenges. Biomaterial surfaces can present nanoscale topographical cues that influence neuronal differentiation and process outgrowth. By combining these scaffolds with additional molecular biology strategies, synergistic control over cell fate can be achieved. Here, we review recent progress in promoting neuronal fate using techniques at the interface of biomaterial science and genetic engineering. New data demonstrates that combining nanofiber topography with an induced genetic program enhances neuritogenesis in a synergistic fashion. We propose combining patterned biomaterial surface cues with prescribed genetic programs to achieve neuronal cell fates with the desired sublineage specification, neurochemical profile, targeted integration, and electrophysiological properties.

New routes for transgenesis of the mouse

Transgenesis refers to the molecular genetic techniques for directing specific insertions, deletions and point mutations in the genome of germ cells in order to create genetically modified organisms (GMO). Genetic modification is becoming more practicable, efficient and predictable with the development and use of a variety of cell and molecular biology tools and DNA sequencing technologies. A collection of plasmidial and viral vectors, cell-type specific promoters, positive and negative selectable markers, reporter genes, drug-inducible Cre-loxP and Flp/FRT recombinase systems are available which ensure efficient transgenesis in the mouse. The technologies for the insertion and removal of genes by homologous-directed recombination in embryonic stem cells (ES) and generation of targeted gain- and loss-of function alleles have allowed the creation of thousands of mouse models of a variety of diseases. The engineered zinc finger nucleases (ZFNs) and small hairpin RNA-expressing constructs are novel tools with useful properties for gene knockout free of ES manipulation. In this review we briefly outline the different approaches and technologies for transgenesis as well as their advantages and disadvantages. We also present an overview on how the novel integrative mouse and human genomic databases and bioinformatics approaches have been used to understand genotype-phenotype relationships of hundreds of mutated and candidate disease genes in mouse models. The updating and continued improvements of the genomic technologies will eventually help us to unraveling the biological and pathological processes in such a way that they can be translated more efficiently from mouse to human and vise-versa.

Advances in microRNA-mediated reprogramming technology

The use of somatic cells to generate induced-pluripotent stem cells (iPSCs), which have gene characteristic resembling those of human embryonic stem cells (hESCs), has opened up a new avenue to produce patient-specific stem cells for regenerative medicine. MicroRNAs (miRNAs) have gained much attention over the past few years due to their pivotal role in many biological activites, including metabolism, host immunity, and cancer. Soon after the discovery of embryonic-stem-cell- (ESC-) specific miRNAs, researchers began to investigate their functions in embryonic development and differentiation, as well as their potential roles in somatic cell reprogramming (SCR). Several approaches for ESC-specific miRNA-mediated reprogramming have been developed using cancer and somatic cells to generate ESC-like cells with similarity to iPSCs and/or hESCs. However, the use of virus-integration to introduce reprogramming factors limits future clinical applications. This paper discusses the possible underlying mechanism for miRNA-mediated somatic cell reprogramming and the approaches used by different groups to induce iPSCs with miRNAs.

Advancements in reprogramming strategies for the generation of induced pluripotent stem cells

Direct reprogramming of somatic cells into induced pluripotent stem (iPS) cells has emerged as an invaluable method for generating patient-specific stem cells of any lineage without the use of embryonic materials. Following the first reported generation of iPS cells from murine fibroblasts using retroviral transduction of a defined set of transcription factors, various new strategies have been developed to improve and refine the reprogramming technology. Recent developments provide optimism that the generation of safe iPS cells without any genomic modification could be derived in the near future for the use in clinical settings. This review summarizes current and evolving strategies in the generation of iPS cells, including types of somatic cells for reprogramming, variations of reprogramming genes, reprogramming methods, and how the advancement iPS cells technology can lead to the future success of reproductive medicine.

Imaging and recording subventricular zone progenitor cells in live tissue of postnatal mice

The subventricular zone (SVZ) is one of two regions where neurogenesis persists in the postnatal brain. The SVZ, located along the lateral ventricle, is the largest neurogenic zone in the brain that contains multiple cell populations including astrocyte-like cells and neuroblasts. Neuroblasts migrate in chains to the olfactory bulb where they differentiate into interneurons. Here, we discuss the experimental approaches to record the electrophysiology of these cells and image their migration and calcium activity in acute slices. Although these techniques were in place for studying glial cells and neurons in mature networks, the SVZ raises new challenges due to the unique properties of SVZ cells, the cellular diversity, and the architecture of the region. We emphasize different methods, such as the use of transgenic mice and in vivo electroporation that permit identification of the different SVZ cell populations for patch clamp recording or imaging. Electroporation also permits genetic labeling of cells using fluorescent reporter mice and modification of the system using either RNA interference technology or floxed mice. In this review, we aim to provide conceptual and technical details of the approaches to perform electrophysiological and imaging studies of SVZ cells.