Efficient Generation of Dopamine Neurons by Synthetic Transcription Factor mRNAs

Therapeutic applications of cell engineering using mRNA technology

Engineering and reprogramming cells has significant therapeutic potential to treat a wide range of diseases, by replacing missing or defective proteins, to provide transcription factors (TFs) to reprogram cell phenotypes, or to provide enzymes such as RNA-guided Cas9 derivatives for CRISPR-based cell engineering. While viral vector-mediated gene transfer has played an important role in this field, the use of mRNA avoids safety concerns associated with the integration of DNA into the host cell genome, making mRNA particularly attractive for in vivo applications. Widespread application of mRNA for cell engineering is limited by its instability in the biological environment and challenges involved in the delivery of mRNA to its target site. In this review, we examine challenges that must be overcome to develop effective therapeutics.

Reduced Cytotoxicity by Repetitive mRNA Transfection in Differentiated Neurons

Background and Objectives

mRNA-based protein expression technology has been used to express functional proteins. We have previously generated dopamine neurons from rat-embryo derived neural precursor cells (NPCs) through repeated transfection of synthetic transcription factor mRNA encoding dopamine-inducible genes. However, NPCs began to die approximately 10 d post-transfection. In this study, we examined a long-term transfection protocol that did not affect cell viability.

Methods and Results

Experiments were performed in eight groups sorted according to the start date of mRNA transfection. mRNA was transfected into NPCs daily for 21 d and live cell images of each group were recorded. NPCs which were differentiated for more than five days showed sustained gene expression and appreciable viability despite daily mRNA transfection for 21 d.

Conclusions

Repeated mRNA transfection requires cells with a sufficient differentiation period.

Combining NGN2 programming and dopaminergic patterning for a rapid and efficient generation of hiPSC-derived midbrain neurons

The use of human derived induced pluripotent stem cells (hiPSCs) differentiated to dopaminergic (DA) neurons offers a valuable experimental model to decorticate the cellular and molecular mechanisms of Parkinson's disease (PD) pathogenesis. However, the existing approaches present with several limitations, notably the lengthy time course of the protocols and the high variability in the yield of DA neurons. Here we report on the development of an improved approach that combines neurogenin-2 programming with the use of commercially available midbrain differentiation kits for a rapid, efficient, and reproducible directed differentiation of hiPSCs to mature and functional induced DA (iDA) neurons, with minimum contamination by other brain cell types. Gene expression analysis, associated with functional characterization examining neurotransmitter release and electrical recordings, support the functional identity of the iDA neurons to A9 midbrain neurons. iDA neurons showed selective vulnerability when exposed to 6-hydroxydopamine, thus providing a viable in vitro approach for modeling PD and for the screening of small molecules with neuroprotective proprieties.

Injury to dopaminergic neurons development via the Lmx1a/Wnt1 autoregulatory loop induced by simazine

Simazine is a kind of persistent organic pollutant that is detected in both ground and water and has several routes of exposure. Here, we explored the mechanisms underlying simazine-related effects on dopaminergic neurons via development-related factors using mouse embryos and embryonic mesencephalic hybrid cell line (MN9D cells). We treated pregnant mice with 50 μg/kg bw, 200 μg/kg bw simazine from the 0.5 day to the 10.5 day of embryonic phase and MN9D cells with 600 μM simazine for 24 h to research the mechanism of dopaminergic neurons acute respond to simazine through preliminary experiments. Protein expressions of LIM homeobox transcription factor 1-alpha (Lmx1a) and LIM homeobox transcription factor 1-beta (Lmx1b) displayed a dose- and time-dependent increase after the exposure to simazine. In the 200 μg/kg bw of embryos and the 24h-600 μM of MN9D cells, protein levels of dopaminergic developmental factors were significantly upregulated, and dopaminergic function was significantly damaged for the abnormal expression of Dyt5b. We demonstrated simazine induced the injury to dopaminergic neurons via the Lmx1a/wingless-related integration site 1 (Wnt1) and Lmx1b pathways. In the transfection experiments, we knocked down Lmx1a and Lmx1b of cells to verify the potential target of simazine-induced injury to dopaminergic neurons, respectively. We detected the protein and mRNA levels of development-related genes of dopaminergic neurons and intracellular dopamine levels in different treatment groups. Based on our experiments' results, we demonstrated an acute response to 24 h-600 μM simazine treatment, the simazine-induced injury to dopaminergic neuronal which leads to abnormal dopamine levels and dopaminergic impairment is via the activation of the Lmx1a/Wnt1 autoregulatory loop. Lmx1a is a promising target in the search for the mechanisms underlying simazine-induced dopaminergic injury.

Messenger RNA/polymeric carrier nanoparticles for delivery of heme oxygenase-1 gene in the post-ischemic brain

Ischemic stroke is a cerebrovascular disease caused by narrowed cerebral arteries. Thrombolytic agents such as tissue-plasminogen activators have been used for recanalization of the blood supply into the ischemic region. However, ischemia-reperfusion damage continues to increase the infarction volume. In this study, heme oxygenase-1 (HO1)-mRNA was delivered into the brain, using a non-viral carrier. Various non-viral carriers such as polyethylenimine (25 kDa, PEI25k), lipofectamine, dexamethasone-conjugated PEI2k (Dexa-PEI2k), deoxycholic acid-conjugated PEI2k (DA-PEI2k), and R3V6 peptides were evaluated as carriers of mRNA into the brain. Gene delivery assays showed that DA-PEI2k and lipofectamine had a higher mRNA delivery efficiency than the other carriers in Neuro2A cells in vitro and a rat brain in vivo. Cytotoxicity assays showed that lipofectamine had higher toxicity than DA-PEI2k. Therefore, DA-PEI2k was used for delivery of HO1-mRNA. Unlike plasmid DNA (pDNA), mRNA is expressed in the cytosol without nuclear translocation. This suggests that mRNA may have higher gene expression than pDNA, since the nuclear location of pDNA is an inefficient step. Indeed, in in vitro transfection assays, HO1-mRNA/DA-PEI2k had higher gene expression than HO1-pDNA/DA-PEI2k without induction of a pro-inflammatory cytokine. The therapeutic effects of HO1-mRNA delivery using DA-PEI2k were evaluated in the middle cerebral artery occlusion animal model after local injection. HO1-mRNA delivery had higher gene expression than HO1-pDNA delivery 24 h after the local injection. In addition, HO1-mRNA delivery reduced the infarct size more efficiently than HO1-pDNA delivery. The results suggest that the delivery of mRNA using DA-PEI2k may be useful for gene therapy of ischemic stroke.

Design, Assembly, Production, and Transfection of Synthetic Modified mRNA

Proteins are drivers of cell functions and are targets of many therapies. Exogenous protein expression techniques, therefore, have been essential for research and medicine. The most common method for exogenous protein expression relies on DNA-based viral or non-viral vectors. However, DNA-based vectors have the potential to integrate into the host genome and cause permanent mutations. RNA-based vectors solve this shortcoming. In particular, synthetic modified mRNA provides non-viral, integration-free, zero-footprint method for expressing proteins. Modified mRNA can direct cell fate specification and cellular reprogramming faster and more efficiently than other methods. Furthermore, when simultaneously express multiple different proteins, mRNA vectors allow for greater flexibility and control over stoichiometric ratios, dose titrations, and complete silencing of expressions. Additionally, modified mRNAs have been shown to be viable and safe as therapeutic agents for gene therapy and vaccine, providing an alternative approach to address diseases. Despite these advantages, technical challenge, mRNA instability, and host immunogenicity have caused significant barriers to widespread use of this technology. The comprehensive method presented here addresses all of these shortcomings. This stepwise protocol describes every step necessary for the synthesis of modified mRNA from any coding DNA sequence of interest. The meticulously detailed protocol enables the users to make alterations to each component of modified mRNA for even more significant customization, allowing the researchers to apply this technology to a wide range of uses. This non-cytotoxic synthetic modified mRNA can be used for protein expression, regulation of cell reprogramming or differentiation, and drug delivery.