Translation, but not transfection limits clinically relevant, exogenous mRNA based induction of alpha-4 integrin expression on human mesenchymal stem cells

Mesenchymal stem cell engineering by ARCA analog-capped mRNA

We previously have shown that mRNA-based engineering may enhance mesenchymal stem cell (MSC) trafficking. However, optimal conditions for in vitro mRNA engineering of MSCs are unknown. Here, we investigated several independent variables: (1) transfection factor (Lipofectamine 2000 vs. TransIT), (2) mRNA purification method (spin column vs. high-performance liquid chromatography [HPLC] column), and (3) mRNA capping (ARCA vs. β-S-ARCA D1 and β-S-ARCA D2). Dependent variables included protein production based on mRNA template (measured by the bioluminescence of reporter gene luciferase over hours), MSC metabolic activity corresponding with their wellbeing measured by CCK-8 over days, and endogenous expression of genes by RT-qPCR related to innate intracellular immune response and decapping at two time points: days 2 and 5. We have found that Lipofectamine 2000 outperforms TransIT, and used it throughout the study. Then, we showed that mRNA must be purified by HPLC to be relatively neutral to MSCs in terms of metabolic activity and endogenous protein production. Ultimately, we demonstrated that β-S-ARCA D1 enables higher protein production but at the cost of lower MSC metabolic activity, with no impact on RT-qPCR results. Thus Lipofectamine 2000-based in vitro transfection of HPLC-purified and ARCA- or β-S-ARCA D1-capped mRNA is optimal for MSC engineering.

Cutting-edge advances in modeling the blood-brain barrier and tools for its reversible permeabilization for enhanced drug delivery into the brain

The blood-brain barrier (BBB) is a sophisticated structure whose full functionality is required for maintaining the executive functions of the central nervous system (CNS). Tight control of transport across the barrier means that most drugs, particularly large size, which includes powerful biologicals, cannot reach their targets in the brain. Notwithstanding the remarkable advances in characterizing the cellular nature of the BBB and consequences of BBB dysfunction in pathology (brain metastasis, neurological diseases), it remains challenging to deliver drugs to the CNS. Herein, we outline the basic architecture and key molecular constituents of the BBB. In addition, we review the current status of approaches that are being explored to temporarily open the BBB in order to allow accumulation of therapeutics in the CNS. Undoubtedly, the major concern in field is whether it is possible to open the BBB in a meaningful way without causing negative consequences. In this context, we have also listed few other important key considerations that can improve our understanding about the dynamics of the BBB.

Proteomic Analysis Reveals Molecular Differences in the Development of Gastric Cancer

Gastric cancer (GC) is the 3rd leading cause of death from cancer and the 5th most common cancer worldwide. The detection rate of GC among Tibetans is significantly higher than that in Han Chinese, probably due to differences in their living habits, dietary structure, and environment. Despite such a high disease burden, the epidemiology of gastric cancer has not been studied in this population. Molecular markers are required to aid the diagnosis and treatment of GC. In this study, we collected gastric tissue samples from patients in Tibet with chronic nonatrophic gastritis (CNAG) (n = 6), chronic atrophic gastritis (CAG) (n = 7), gastric intraepithelial neoplasia (GIN) (n = 4), and GC (n = 5). The proteins in each group were analyzed using coupled label-free mass spectrometry. In addition, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein interaction networks were used to analyze the differentially expressed proteins (DEPs) among groups. DEPs were quantified in comparisons of GC versus CNAG (223), GC versus GIN (100), and GIN versus CNAG (341). GO and KEGG analyses showed that the DEPs were mainly associated with immunity (GC versus CNAG) and cancer proliferation and metastasis (GC versus GIN, and GIN versus CNAG). Furthermore, the expression levels of cell proliferation and cytoskeleton-related proteins increased consistently during cancer development, such as ITGA4, DDC, and CPT1A; thus, they are potential diagnostic markers. These results obtained by proteomics analysis could improve our understanding of cancer biology in GC and provide a rich resource for data mining and discovering potential immunotherapy targets.

The legacy of mRNA engineering: A lineup of pioneers for the Nobel Prize

mRNA is like Hermes, delivering the genetic code to cellular construction sites, so it has long been of interest, but only to a small group of scientists, and only demonstrating its remarkable efficacy in coronavirus disease 2019 (COVID-19) vaccines allowed it to go out into the open. Therefore, now is the right timing to delve into the stepping stones that underpin this success and pay tribute to the underlying scientists. From this perspective, advances in mRNA engineering have proven crucial to the rapidly growing role of this molecule in healthcare. Development of consecutive generations of cap analogs, including anti-reverse cap analogs (ARCAs), has significantly boosted translation efficacy and maintained an enthusiasm for mRNA research. Nucleotide modification to protect mRNA molecules from the host's immune system, followed by finding appropriate purification and packaging methods, were other links in the chain enabling medical breakthroughs. Currently, vaccines are the central area of mRNA research, but it will reach far beyond COVID-19. Supplementation of missing or abnormal proteins is another large field of mRNA research. Ex vivo cell engineering and genome editing have been expanding recently. Thus, it is time to recognize mRNA pioneers while building upon their legacy.

mRNA-based therapies: Preclinical and clinical applications

At the fundamental level, messenger RNA (mRNA)-based therapeutics involves the delivery of in vitro-transcribed (IVT) mRNA into the cytoplasm of a target cell, where it is translated into the desired protein. IVT mRNA presents various advantages compared to DNA and recombinant protein-based approaches that make it ideal for a broad range of therapeutic applications. IVT mRNA, which is translated in the cytoplasm after transfection into cells, can encode virtually any target protein. Notably, it does not enter the nucleus, which avoids its integration into the genome and the risk of insertional mutagenesis. The large-scale production of IVT mRNA is less complex than production of recombinant proteins, and Good Manufacturing Practice-compliant mRNA production is easily scalable, ideally poising mRNA for not only off-the-shelf, but more personalized treatment approaches. IVT mRNA's safety profile, pharmacokinetics, and pharmacodynamics, including its inherent immunostimulatory capacity, can be optimized for different therapeutic applications by harnessing a wide array of optimized sequence elements, chemical modifications, purification techniques, and delivery methods. The value of IVT mRNA was recently proved during the COVID-19 pandemic when mRNA-based vaccines outperformed the efficacy of established technologies, and millions of doses were rapidly deployed. In this review, we will discuss chemical modifications of IVT mRNA and highlight numerous preclinical and clinical applications including vaccines for cancer and infectious diseases, cancer immunotherapy, protein replacement, gene editing, and cell reprogramming.

Endothelial nitric oxide synthase-engineered mesenchymal stromal cells induce anti-inflammation in experimental immune models

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) remain an area of interest in the field of regenerative medicine. Although there is clear evidence of safety, a lack of substantial efficacy has led to many MSC-based clinical trials to stall in phase 1. Therefore, potentiating MSCs with biologically relevant messenger RNA (mRNA) transcripts presents a relatively safe and efficient way to increase functionality.

METHODS

In this study, human bone marrow-derived MSCs were transfected with endothelial nitric oxide synthase (eNOS) mRNA and evaluated for transfection efficiency and immunosuppressive ability. To assess MSC-eNOS functionality, T-cell proliferation assays and mouse models of experimental autoimmune encephalomyelitis and graft-versus-host disease were used.

RESULTS

The authors found that MSC-eNOS retained MSC characteristics and exhibited significantly enhanced immunosuppressive effects compared with naive MSCs in both in vitro and in vivo models.

CONCLUSIONS

It is feasible to pursue eNOS mRNA transfection to potentiate the immunomodulatory capacity of MSCs for clinical applications in the future.

Transfection types, methods and strategies: a technical review

Transfection is a modern and powerful method used to insert foreign nucleic acids into eukaryotic cells. The ability to modify host cells' genetic content enables the broad application of this process in studying normal cellular processes, disease molecular mechanism and gene therapeutic effect. In this review, we summarized and compared the findings from various reported literature on the characteristics, strengths, and limitations of various transfection methods, type of transfected nucleic acids, transfection controls and approaches to assess transfection efficiency. With the vast choices of approaches available, we hope that this review will help researchers, especially those new to the field, in their decision making over the transfection protocol or strategy appropriate for their experimental aims.

mRNA-Enhanced Cell Therapy and Cardiovascular Regeneration

mRNA has emerged as an important biomolecule in the global call for the development of therapies during the COVID-19 pandemic. Synthetic in vitro-transcribed (IVT) mRNA can be engineered to mimic naturally occurring mRNA and can be used as a tool to target "undruggable" diseases. Recent advancement in the field of RNA therapeutics have addressed the challenges inherent to this drug molecule and this approach is now being applied to several therapeutic modalities, from cancer immunotherapy to vaccine development. In this review, we discussed the use of mRNA for stem cell generation or enhancement for the purpose of cardiovascular regeneration.

Enhancing the Therapeutic Potential of CCL2-Overexpressing Mesenchymal Stem Cells in Acute Stroke

Although intravenous administration of mesenchymal stem cells (MSCs) is effective for experimental stroke, low engraftment and the limited functional capacity of transplanted cells are critical hurdles for clinical applications. C-C motif chemokine ligand 2 (CCL2) is associated with neurological repair after stroke and delivery of various cells into the brain via CCL2/CCR2 (CCL2 receptor) interaction. In this study, after CCL2-overexpressing human umbilical cord-derived MSCs (hUC-MSCs) were intravenously transplanted with mannitol in rats with middle cerebral arterial occlusion, we compared the differences between four different treatment groups: mannitol + CCL2-overexpressing hUC-MSCs (CCL2-MSC), mannitol + naïve hUC-MSCs (M-MSC), mannitol only, and control. At four-weeks post-transplantation, the CCL2-MSC group showed significantly better functional recovery and smaller stroke volume relative to the other groups. Additionally, we observed upregulated levels of CCR2 in acute ischemic brain and the increase of migrated stem cells into these areas in the CCL2-MSC group relative to the M-MSC. Moreover, the CCL2-MSC group displayed increased angiogenesis and endogenous neurogenesis, decreased neuro-inflammation but with increased healing-process inflammatory cells relative to other groups. These findings indicated that CCL2-overexpressing hUC-MSCs showed better functional recovery relative to naïve hUC-MSCs according to the increased migration of these cells into brain areas of higher CCR2 expression, thereby promoting subsequent endogenous brain repair.

Analysis of the Level of Plasmid-Derived mRNA in the Presence of Residual Plasmid DNA by Two-Step Quantitative RT-PCR

In transfection experiments with mammalian cells aiming to overexpress a specific protein, it is often necessary to correctly quantify the level of the recombinant and the corresponding endogenous mRNA. In our case, mouse calvarial osteoblasts were transfected with a vector containing the complete Pex11β cDNA (plasmid DNA). The Pex11β mRNA level, as calculated using the RT-qPCR product, was unrealistically higher (>1000-fold) in transfected compared to non-transfected cells, and we assumed that there were large amounts of contaminating plasmid DNA in the RNA sample. Thus, we searched for a simple way to distinguish between plasmid-derived mRNA, endogenous genome-derived mRNA and plasmid DNA, with minimal changes to standard RT-PCR techniques. We succeeded by performing a plasmid mRNA-specific reverse transcription, and the plasmid cDNA was additionally tagged with a nonsense tail. A subsequent standard qPCR was conducted using appropriate PCR primers annealing to the plasmid cDNA and to the nonsense tail. Using this method, we were able to determine the specific amount of mRNA derived from the transfected plasmid DNA in comparison to the endogenous genome-derived mRNA, and thus the transfection and transcription efficiency.

Mesenchymal stem cells injected into carotid artery to target focal brain injury home to perivascular space

Rationale: The groundbreaking discovery of mesenchymal stem cells (MSCs) with their multifaceted benefits led to their widespread application in experimental medicine, including neurology. Efficient delivery of MSCs to damaged regions of the central nervous system may be a critical factor in determining outcome. Integrin VLA-4 (α4β1) coded by ITGA4 and ITGB1 genes is an adhesion molecule expressed by leukocytes, which is responsible for initiation of their diapedesis through cell docking to the inflamed vessel wall expressing VCAM1 receptor. This function of VLA-4 has been recapitulated in neural stem cells and glial progenitors. Thus, it was prudent to investigate this tool as a vehicle driving extravasation of MSCs. Since MSCs naturally express ITGB1 subunit, we decided to supplement them with ITGA4 only. The purpose of our current study is to investigate the eventual fate of IA delivered ITGA4 engineered and naive MSCs.

Methods: mRNA-ITGA4 transfected and naive MSCs were injected to right internal carotid artery of rats with focal brain injury. Through next three days MSC presence in animals' brain was navigated by magnetic resonance imaging. Transplanted cell location relative to the brain blood vessels and host immunological reaction were analyzed post-mortem by immunohistochemistry. The chemotaxis of modified and naive MSCs was additionally examined in in vitro transwell migration assay.

Results: Both naïve and ITGA4-overexpressing cells remained inside the vascular lumen over the first two days after IA infusion. On the third day, 39% of mRNA-ITGA4 modified and 51% naïve MSCs homed to perivascular space in the injury region (p=NS). The gradual decrease of both naive and mRNA-ITGA4 transfected hBM-MSCs in the rat brain was observed. mRNA-ITGA4 transfected MSCs appeared to be more vulnerable to phagocytosis than naïve cells. Moreover, in vitro study revealed that homogenate from the injured brain repels migration of MSCs, corroborating the incomplete extravasation observed in vivo.

Conclusions: In summary, IA transplanted MSCs are capable of homing to the perivascular space, an integral part of neurovascular unit, which might contribute to the replacement of injured pericytes, a critical element facilitating restoration of CNS function. The mRNA-ITGA4 transfection improves cell docking to vessel but this net benefit vanishes over the next two days due to fast clearance from cerebral vessels of the majority of transplanted cells, regardless of their engineering status. The drawbacks of mRNA-ITGA4 transfection become apparent on day 3 post transplantation due to the lower survival and higher vulnerability to host immune attack.

Nanomedicines to Deliver mRNA: State of the Art and Future Perspectives

The use of messenger RNA (mRNA) in gene therapy is increasing in recent years, due to its unique features compared to plasmid DNA: Transient expression, no need to enter into the nucleus and no risk of insertional mutagenesis. Nevertheless, the clinical application of mRNA as a therapeutic tool is limited by its instability and ability to activate immune responses; hence, mRNA chemical modifications together with the design of suitable vehicles result essential. This manuscript includes a revision of the strategies employed to enhance in vitro transcribed (IVT) mRNA functionality and efficacy, including the optimization of its stability and translational efficiency, as well as the regulation of its immunostimulatory properties. An overview of the nanosystems designed to protect the mRNA and to overcome the intra and extracellular barriers for successful delivery is also included. Finally, the present and future applications of mRNA nanomedicines for immunization against infectious diseases and cancer, protein replacement, gene editing, and regenerative medicine are highlighted.

Genetically Engineered Lung Cancer Cells for Analyzing Epithelial-Mesenchymal Transition

Cell plasticity, defined as the ability to undergo phenotypical transformation in a reversible manner, is a physiological process that also exerts important roles in disease progression. Two forms of cellular plasticity are epithelial-mesenchymal transition (EMT) and its inverse process, mesenchymal-epithelial transition (MET). These processes have been correlated to the poor outcome of different types of neoplasias as well as drug resistance development. Since EMT/MET are transitional processes, we generated and validated a reporter cell line. Specifically, a far-red fluorescent protein was knocked-in in-frame with the mesenchymal gene marker VIMENTIN (VIM) in H2170 lung cancer cells. The vimentin reporter cells (VRCs) are a reliable model for studying EMT and MET showing cellular plasticity upon a series of stimulations. These cells are a robust platform to dissect the molecular mechanisms of these processes, and for drug discovery in vitro and in vivo in the future.

Single-cell, high-throughput analysis of cell docking to vessel wall

Therapeutic potential of mesenchymal stem cells (MSCs) has been reported consistently in animal models of stroke, with mechanism mainly through immunomodulation and paracrine activity. Intravenous injection has been a prevailing route for MSCs administration, but cell quantities needed when scaling-up from mouse to human are extremely high putting into question feasibility of that approach. Intra-arterial delivery directly routes the cells to the brain thus lowering the required dose. Cell engineering may additionally improve cell homing, further potentiating the value of intra-arterial route. Therefore, our goal was to create microfluidic platform for screening and fast selection of molecules that enhance the docking of stem cells to vessel wall. We hypothesized that our software will be capable of detecting distinct docking properties of naïve and ITGA4-engineered MSCs. Indeed, the cell flow tracker analysis revealed positive effect of cell engineering on docking frequency of MSCs (42% vs. 9%, engineered vs. control cells, p < 0.001). These observations were then confirmed in an animal model of focal brain injury where cell engineering resulted in improved homing to the brain. To conclude, we developed a platform to study the docking of cells to the vessel wall which is highly relevant for intraarterial cell targeting or studies on neuroinflammation.

Neutral Lipopolyplexes for In Vivo Delivery of Conventional and Replicative RNA Vaccine

Nucleic acid vaccination relies on injecting DNA or RNA coding antigen(s) to induce a protective immune response. RNA vaccination is being increasingly used in preclinical and clinical studies. However, few delivery systems have been reported for in vivo delivery of RNA of different sizes. Using a tripartite formulation with RNA, cationic polymer, and anionic liposomes, we were able to encapsulate RNA into neutral lipopolyplexes (LPPs). LPPs were stable in vitro and successfully delivered conventional RNA and replicative RNA to dendritic cells in cellulo. Their injection led to reporter gene expression in mice. Finally, administration of LPP-Replicon RNA (RepRNA) led to an adaptive immune response against the antigen coded by the RepRNA. Accordingly, LPPs may represent a universal formulation for RNA delivery.

Labeling of human mesenchymal stem cells with different classes of vital stains: robustness and toxicity

Background

Mesenchymal stem cell (MSC) transplantation has been explored as a new clinical approach to repair injured tissues. However, in order to evaluate the therapeutic activity of MSC, cell tracking techniques are required to determine the fate of transplanted cells in both preclinical and clinical studies. In these aspects, different vital stains offer the potential for labeling and monitoring of grafted cells in vivo. It is desirable to have tracking agents which have long-term stability, are not toxic to the cells, and do not affect cell function.

Methods

Here, we selected three different labels: CellTracker™ Green CMFDA, eGFP-mRNA (genetic pre-tag), and Molday ION Rhodamine B™ (nanoparticle-based fluorescent and magnetic label) and performed extensive analysis of their influence on in vitro expansion of human bone marrow-derived mesenchymal stem cells (hBM-MSCs), as well as potential of affecting therapeutic activity and the impact on the durability of staining.

Results

Our study showed that basic hBM-MSC characteristics and functions might be affected by labeling. We observed strong alterations of metabolic activity and morphology after eGFP and CellTracker™ Green CMFDA hBM-MSC staining. Molday ION Rhodamine B™ labeling revealed superior properties relatively to other vital stains. The relative expression level of most of the investigated growth factors remained stable after cell labeling, but we have observed some changes in the case of EGF, GDNF, HGF, and IGF gene expression.

Conclusions

Taken together, we suggest performing similar to ours extensive analysis prior to using any cell label to tag MSC in experiments, as it can thoroughly bias results.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1296-8) contains supplementary material, which is available to authorized users.

Concise Review: Application of Chemically Modified mRNA in Cell Fate Conversion and Tissue Engineering

Chemically modified RNA (cmRNA) has potential as a safe and efficient tool for nucleic acid‐based therapies and regenerative medicine. Modifications in the chemistry of mRNA can enhance stability, reduce immunogenicity, and thus facilitate mRNA‐based nucleic acid therapy, which eliminates risk of insertional mutagenesis. In addition to these valuable advantages, the mRNA‐based method showed significantly higher efficacy for reprogramming somatic cells to pluripotency compared with DNA‐ or protein‐based methods. These findings suggest cmRNA can provide a powerful and safe tool for cell programming and reprogramming. Delivery methods, particularly using lipid nanoparticles, provide strategies for cell and organ‐specific targeting. The present study comprehensively compares studies that have used cmRNAs for cell fate conversion and tissue engineering. The information should be useful for investigators looking to choose the most efficient and straightforward cmRNA‐based strategy and protocol for tissue engineering and regenerative medicine research. stem cells translational medicine2019;8:833&843

Biomedical applications of mRNA nanomedicine

As an attractive alternative to plasmid DNA, messenger RNA (mRNA) has recently emerged as a promising class of nucleic acid therapeutics for biomedical applications. Advances in addressing the inherent shortcomings of mRNA and in the development of nanoparticle-based delivery systems have prompted the development and clinical translation of mRNA-based medicines. In this review, we discuss the chemical modification strategies of mRNA to improve its stability, minimize immune responses, and enhance translational efficacy. We also highlight recent progress in nanoparticle-based mRNA delivery. Considerable attention is given to the increasingly widespread applications of mRNA nanomedicine in the biomedical fields of vaccination, protein-replacement therapy, gene editing, and cellular reprogramming and engineering.

Evaluation of modified Interferon alpha mRNA constructs for the treatment of non-melanoma skin cancer

Application of in vitro transcribed (IVT) messenger ribonucleic acid (mRNA) is an increasingly popular strategy to transiently produce proteins as therapeutics in a tissue or organ of choice. Here, we focused on the skin and aimed to test if whole human skin tissue explant technology can be used to evaluate the expression efficacy of different IVT Interferon alpha (IFN-α) mRNA constructs in situ, after biolistic delivery. Skin explants were viable and intact for at least five days based on histologic analysis and TUNEL staining. Using GFP reporter mRNA formulations, we found mostly epidermal expression after biolistic delivery. Two out of five sequence-optimized IFN-α mRNA variants resulted in significantly improved IFN-α protein expression in human skin compared to native IFN-α mRNA transfection. IFN-α secretion analysis of the surrounding culture media confirmed these results. We provide a proof-of-concept that IFN-α mRNA delivery into intact human full thickness skin explants can be utilized to test mRNA sequence modifications ex vivo. This approach could be used to develop novel mRNA-based treatments of common epidermal skin conditions including non-melanoma skin cancer, where IFN-α protein therapy has previously shown a strong therapeutic effect.