Efficient gene knockdowns in mouse embryonic stem cells using microRNA-based shRNAs

MS2 VLP-based delivery of microRNA-146a inhibits autoantibody production in lupus-prone mice

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the presence of pathogenic autoantibodies. Recent studies suggest that microRNAs (miRNAs) play an essential role in immunoregulation and may be involved in the pathogenesis of SLE. Therefore, it was of interest to investigate the potential therapeutic application of miRNAs in SLE, a concept that has not been thoroughly investigated thus far. Virus-like particles (VLPs) are a type of recombinant nanoparticle enveloped by certain proteins derived from the outer coat of a virus. Herein, we describe a novel miRNA-delivery approach via bacteriophage MS2 VLPs and investigate the therapeutic effects of miR-146a, a well-studied and SLE-related miRNA, in BXSB lupus-prone mice.

METHODS

VLPs containing miR-146a, and the control VLPs, were prepared using an Escherichia coli expression system and then administered to lupus-prone mice over a 12-day period. We performed an enzyme-linked immunosorbent assay to evaluate the anti-dsDNA antibody, autoantibody to nuclear antigen (ANA), total IgG and total IgM levels in serum. The expression of miR-146a was analyzed by qRT-PCR. SLE-related cytokines as well as some toll-like receptor signaling pathway molecules were also measured.

RESULTS

Treatment with MS2-miR146a VLP showed profound effects on lupus-prone BXSB mice, including an increased level of mature miR-146a, which led to a significant reduction in the expression of autoantibodies and total IgG. Remarkably, these mice also exhibited reduced levels of proinflammatory cytokines, including IFN-Interferon-α (IFN-α), Interleukin-1β (Il-1β) and Interleukin-6 (Il-6). Moreover, we showed that the toll-like receptor pathway was involved in this regulation.

CONCLUSION

Restoring the loss of miR-146a was effective in eliminating the production of autoantibodies and ameliorating SLE progression in lupus-prone mice. Thus, the induction of dysregulated miRNAs by an MS2 VLP-based delivery system may lead to novel therapies.

Development of a microRNA delivery system based on bacteriophage MS2 virus-like particles

Recently, microRNA (miRNA)-mediated RNA interference has been developed as a useful tool in gene function analysis and gene therapy. A major obstacle in miRNA-mediated RNAi is cellular delivery, which requires an efficient and flexible delivery system. The self-assembly of the MS2 bacteriophage capsids has been used to develop virus-like particles (VLPs) for RNA and drug delivery. However, MS2 VLP-mediated miRNA delivery has not yet been reported. We therefore used an Escherichia coli expression system to produce the pre-miR 146a contained MS2 VLPs, and then conjugated these particles with HIV-1 Tat(47-57) peptide. The conjugated MS2 VLPs effectively transferred the packaged pre-miR146a RNA into various cells and tissues, with 0.92-14.76-fold higher expression of miR-146a in vitro and about two-fold higher expression in vivo, and subsequently suppressed its targeting gene. These findings suggest that MS2 VLPs can be used as a novel vehicle in miRNA delivery systems, and may have applications in gene therapy.

Efficient gene knockdowns in mouse embryonic stem cells using microRNA-based shRNAs

RNA interference (RNAi) is a powerful gene-knockdown technology that has been applied for functional genetic loss-of-function studies in many model eukaryotic systems, including embryonic stem cells (ESCs). Application of RNAi in ESCs allows for dissection of mechanisms by which ESCs self-renew and maintain pluripotency, and also specifying particular cell types needed for cell-replacement therapies. Potent RNAi response can be induced by expression of an microRNA-embedded short-hairpin RNA (shRNA(mir)) cassette that is integrated in the genome by virus infection or site-specific recombination at a defined locus. In this chapter, I will provide detailed protocols to perform shRNA(mir)-mediated RNAi studies in mouse ESCs using retrovirus infection and loxP site-directed recombination for efficient constitutive and inducible gene knockdown, respectively.