Nuclear reprogramming with a non-integrating human RNA virus

Engineering single-cycle MeV vector for CRISPR-Cas9 gene editing

CRISPR-Cas9-mediated gene editing has vast applications in basic and clinical research and is a promising tool for several disorders. Our lab previously developed a non-integrating RNA virus, measles virus (MeV), as a single-cycle reprogramming vector by replacing the viral attachment protein with the reprogramming factors for induced pluripotent stem cell generation. Encouraged by the MeV reprogramming vector efficiency, in this study, we develop a single-cycle MeV vector to deliver the gRNA(s) and Cas9 nuclease to human cells for efficient gene editing. We show that the MeV vector achieved on-target gene editing of the reporter (mCherry) and endogenous genes (HBB and FANCD1) in human cells. Additionally, the MeV vector achieved precise knock-in via homology-directed repair using a single-stranded oligonucleotide donor. The MeV vector is a new and flexible platform for gene knock-out and knock-in modifications in human cells, capable of incorporating new technologies as they are developed.

Advances in RNA Viral Vector Technology to Reprogram Somatic Cells: The Paramyxovirus Wave

Ethical issues are a significant barrier to the use of embryonic stem cells in patients due to their origin: human embryos. To further the development of stem cells in a patient application, alternative sources of cells were sought. A process referred to as reprogramming was established to create induced pluripotent stem cells from somatic cells, resolving the ethical issues, and vectors were developed to deliver the reprogramming factors to generate induced pluripotent stem cells. Early viral vectors used integrating retroviruses and lentiviruses as delivery vehicles for the transcription factors required to initiate reprogramming. However, because of the inherent risk associated with vectors that integrate into the host genome, non-integrating approaches were explored. The development of non-integrating viral vectors offers a safer alternative, and these modern vectors are reliable, efficient, and easy to use to achieve induced pluripotent stem cells suitable for direct patient application in the growing field of individualized medicine. This review summarizes all the RNA viral vectors in the field of reprogramming with a special focus on the emerging delivery vectors based on non-integrating  Paramyxoviruses, Sendai and measles viruses. We discuss their design and evolution towards being safe and efficient reprogramming vectors in generating induced pluripotent stem cells from somatic cells.

miRNA-mediated control of exogenous OCT4 during mesenchymal-epithelial transition increases measles vector reprogramming efficiency

OCT4 is a key mediator of induced pluripotent stem cell (iPSC) reprogramming, but the mechanistic insights into the role of exogenous OCT4 and timelines that initiate pluripotency remain to be resolved. Here, using measles reprogramming vectors, we present microRNA (miRNA) targeting of exogenous OCT4 to shut down its expression during the mesenchymal to the epithelial transition phase of reprogramming. We showed that exogenous OCT4 is required only for the initiation of reprogramming and is dispensable for the maturation stage. However, the continuous expression of SOX2, KLF4, and c-MYC is necessary for the maturation stage of the iPSC. Additionally, we demonstrate a novel application of miRNA targeting in a viral vector to contextually control the vector/transgene, ultimately leading to an improved reprogramming efficiency. This novel approach could be applied to other systems for improving the efficiency of vector-induced processes.

Live Attenuated Measles Virus Vaccine Expressing Helicobacter pylori Heat Shock Protein A

Measles virus (MV) Edmonston derivative strains are attractive vector platforms in vaccine development and oncolytic virotherapy. Helicobacter pylori heat shock protein A (HspA) is a bacterial heat shock chaperone with essential function as a Ni-ion scavenging protein. We generated and characterized the immunogenicity of an attenuated MV strain encoding the HspA transgene (MV-HspA). MV-HspA showed faster replication within 48 h of infection with >10-fold higher titers and faster accumulation of the MV proteins. It also demonstrated a superior tumor-killing effect in vitro against a variety of human solid tumor cell lines, including sarcoma, ovarian and breast cancer. Two intraperitoneal (i.p.) doses of 10⁶ 50% tissue culture infectious dose (TCID₅₀) MV-HspA significantly improved survival in an ovarian cancer xenograft model: 63.5 days versus 27 days for the control group. The HspA transgene induced a humoral immune response in measles-permissive Ifnarko-CD46Ge transgenic mice. Eight of nine animals developed a long-term anti-HspA antibody response with titers of 1:400 to 1:12,800 without any negative impact on development of protective anti-MV immune memory. MV-HspA triggered an immunogenic cytopathic effect as measured by an HMGB1 assay. The absence of significant elevation of PD-L1 expression indicated that vector-encoded HspA could act as an immunomodulator on the immune check point axis. These data demonstrate that MV-HspA is a potent oncolytic agent and vaccine candidate for clinical translation in cancer treatment and immunoprophylaxis against H. pylori.

Improving therapeutic potential of non-viral minimized DNA vectors

The tragic deaths of three patients in a recent AAV-based X-linked myotubular myopathy clinical trial highlight once again the pressing need for safe and reliable gene delivery vectors. Non-viral minimized DNA vectors offer one possible way to meet this need. Recent pre-clinical results with minimized DNA vectors have yielded promising outcomes in cancer therapy, stem cell therapy, stem cell reprograming, and other uses. Broad clinical use of these vectors, however, remains to be realized. Further advances in vector design and production are ongoing. An intriguing and promising potential development results from manipulation of the specific shape of non-viral minimized DNA vectors. By improving cellular uptake and biodistribution specificity, this approach could impact gene therapy, DNA nanotechnology, and personalized medicine.

PICOT promotes T lymphocyte proliferation by down-regulating cyclin D2 expression

The mammalian protein kinase C-interacting cousin of thioredoxin (PICOT; also termed glutaredoxin 3) is a multi-domain monothiol glutaredoxin that is involved in a wide variety of signaling pathways and biological processes. PICOT is required for normal and transformed cell growth and is critical for embryonic development. Recent studies in T lymphocytes demonstrated that PICOT can translocate to the nucleus and interact with embryonic ectoderm development, a polycomb group protein and a core component of the polycomb repressive complex 2, which contributes to the maintenance of transcriptional repression and chromatin remodeling. Furthermore, PICOT was found to interact with chromatin-bound embryonic ectoderm development and alter the extent of histone 3 lysine 27 trimethylation at the promoter region of selected polycomb repressive complex 2 target genes. PICOT knockdown in Jurkat T cells led to increased histone 3 lysine 27 trimethylation at the promoter region of CCND2, a cell cycle-regulating gene which encodes the cyclin D2 protein. As a result, the expression levels of CCND2 mRNA and protein levels were reduced, concomitantly with inhibition of the cell growth rate. Analysis of multiple data sets from the Cancer Genome Atlas revealed that a high expression of PICOT correlated with a low expression of CCND2 in a large number of human cancers. In addition, this parameter correlated with poor patient survival, suggesting that the ratio between PICOT/CCND2 mRNA levels might serve as a predictor of patient survival in selected types of human cancer.

Measles vector as a multigene delivery platform facilitating iPSC reprogramming

Induced pluripotent stem cells (iPSCs) provide a unique platform for individualized cell therapy approaches. Currently, episomal DNA, mRNA, and Sendai virus-based RNA reprogramming systems are widely used to generate iPSCs. However, they all rely on the use of multiple (three to six) components (vectors/plasmids/mRNAs) leading to the production of partially reprogrammed cells, reducing the efficiency of the systems. We produced a one-cycle measles virus (MV) vector by substituting the viral attachment protein gene with the green fluorescent protein (GFP) gene. Here, we present a highly efficient multi-transgene delivery system based on a vaccine strain of MV, a non-integrating RNA virus that has a long-standing safety record in humans. Introduction of the four reprogramming factors OCT4, SOX2, KLF4, and cMYC via a single, "one-cycle" MV vector efficiently reprogrammed human somatic cells into iPSCs, whereas MV vector genomes are rapidly eliminated in derived iPSCs. Our MV vector system offers a new reprogramming platform for genomic modification-free iPSCs amenable for clinical translation.

Measles Virus Persistent Infection of Human Induced Pluripotent Stem Cells

In this study, we found that the measles virus (MV) can infect human-induced pluripotent stem cells (hiPSCs). Wild-type MV strains generally use human signaling lymphocyte activation molecule (SLAM; CD150) as a cellular receptor, while vaccine strains such as the Edmonston strain can use both CD150 and CD46 as receptors. It is not yet known how early in the embryonal differentiation stages these receptors are expressed. We established two hiPSCs (BGU-iPSCs and EMF-iPSCs) which express CD46 and CD150. Both cell types can be infected by MV to form persistent, noncytopathic cell lines that release infectious MV particles. Following MV persistent infection, BGU-iPSCs and EMF-iPSCs remain pluripotent and can differentiate in vitro into the three germ layers. This includes cells expressing the neuronal differentiation markers: NF68 and miRNA-124. Since the MV does not integrate into the cell's genome, it can be utilized as a vehicle to systematically introduce genes into iPSC, to dissect and to define factors regulating lineage differentiation.

Viral and Synthetic RNA Vector Technologies and Applications

Use of RNA is an increasingly popular method to transiently deliver genetic information for cell manipulation in basic research and clinical therapy. In these settings, viral and nonviral RNA platforms are employed for delivery of small interfering RNA and protein-coding mRNA. Technological advances allowing RNA modification for increased stability, improved translation and reduced immunogenicity have led to increased use of nonviral synthetic RNA, which is delivered in naked form or upon formulation. Alternatively, highly efficient viral entry pathways are exploited to transfer genes of interest as RNA incorporated into viral particles. Current viral RNA transfer technologies are derived from Retroviruses, nonsegmented negative-strand RNA viruses or positive-stranded Alpha- and Flaviviruses. In retroviral particles, the genes of interest can either be incorporated directly into the viral RNA genome or as nonviral RNA. Nonsegmented negative-strand virus-, Alpha- and Flavivirus-derived vectors support prolonged expression windows through replication of viral RNA encoding genes of interest. Mixed technologies combining viral and nonviral components are also available. RNA transfer is ideal for all settings that do not require permanent transgene expression and excludes potentially detrimental DNA integration into the target cell genome. Thus, RNA-based technologies are successfully applied for reprogramming, transdifferentiation, gene editing, vaccination, tumor therapy, and gene therapy.

Modeling the autistic cell: iPSCs recapitulate developmental principles of syndromic and nonsyndromic ASD

The opportunity to model autism spectrum disorders (ASD) through generation of patient-derived induced pluripotent stem cells (iPSCs) is currently an emerging topic. Wide-scale research of altered brain circuits in syndromic ASD, including Rett Syndrome, Fragile X Syndrome, Angelman's Syndrome and sporadic Schizophrenia, was made possible through animal models. However, possibly due to species differences, and to the possible contribution of epigenetics in the pathophysiology of these diseases, animal models fail to recapitulate many aspects of ASD. With the advent of iPSCs technology, 3D cultures of patient-derived cells are being used to study complex neuronal phenotypes, including both syndromic and nonsyndromic ASD. Here, we review recent advances in using iPSCs to study various aspects of the ASD neuropathology, with emphasis on the efforts to create in vitro model systems for syndromic and nonsyndromic ASD. We summarize the main cellular activity phenotypes and aberrant genetic interaction networks that were found in iPSC-derived neurons of syndromic and nonsyndromic autistic patients.

Regenerative Medicine for Periodontal and Peri-implant Diseases

The balance between bone resorption and bone formation is vital for maintenance and regeneration of alveolar bone and supporting structures around teeth and dental implants. Tissue regeneration in the oral cavity is regulated by multiple cell types, signaling mechanisms, and matrix interactions. A goal for periodontal tissue engineering/regenerative medicine is to restore oral soft and hard tissues through cell, scaffold, and/or signaling approaches to functional and aesthetic oral tissues. Bony defects in the oral cavity can vary significantly, ranging from smaller intrabony lesions resulting from periodontal or peri-implant diseases to large osseous defects that extend through the jaws as a result of trauma, tumor resection, or congenital defects. The disparity in size and location of these alveolar defects is compounded further by patient-specific and environmental factors that contribute to the challenges in periodontal regeneration, peri-implant tissue regeneration, and alveolar ridge reconstruction. Efforts have been made over the last few decades to produce reliable and predictable methods to stimulate bone regeneration in alveolar bone defects. Tissue engineering/regenerative medicine provide new avenues to enhance tissue regeneration by introducing bioactive models or constructing patient-specific substitutes. This review presents an overview of therapies (e.g., protein, gene, and cell based) and biomaterials (e.g., resorbable, nonresorbable, and 3-dimensionally printed) used for alveolar bone engineering around teeth and implants and for implant site development, with emphasis on most recent findings and future directions.