Integrating piggyBac Transposon Transgenes into Mouse Fibroblasts Using Chemical Methods

Xeno- and transgene-free reprogramming of mesenchymal stem cells toward the cells expressing neural markers using exosome treatments

Neural stem cells (NSCs), capable of self-renew and differentiate into neural cells, hold promise for use in studies and treatments for neurological diseases. However, current approaches to obtain NSCs from a live brain are risky and invasive, since NSCs reside in the subventricular zone and the in the hippocampus dentate gyrus. Alternatively, mesenchymal stem cells (MSCs) could be a more available cell source due to their abundance in tissues and easier to access. However, MSCs are committed to producing mesenchymal tissue and are not capable of spontaneously differentiating into neural cells. Thus, the process of reprogramming of MSCs into neural cells to use in clinical and scientific settings has significantly impacted the advancement of regenerative medicine. Previously, our laboratory reported trans-differentiation of MSCs to neural cells through the induced pluripotent stem (iPS) cells state, which was produced by overexpression of the embryonic stem cell gene NANOG. In the current study, we demonstrate that treatment with exosomes derived from NSCs makes MSCs capable of expressing neural cell markers bypassing the generation of iPS cells. An epigenetic modifier, decitabine (5-aza-2'-deoxycytidine), enhanced the process. This novel Xeno and transgene-free trans-differentiation technology eliminates the issues associated with iPS cells, such as tumorigenesis. Thus, it may accelerate the development of neurodegenerative therapies and in vitro neurological disorder models for personalized medicine.

piggyBac-Based Non-Viral In Vivo Gene Delivery Useful for Production of Genetically Modified Animals and Organs

In vivo gene delivery involves direct injection of nucleic acids (NAs) into tissues, organs, or tail-veins. It has been recognized as a useful tool for evaluating the function of a gene of interest (GOI), creating models for human disease and basic research targeting gene therapy. Cargo frequently used for gene delivery are largely divided into viral and non-viral vectors. Viral vectors have strong infectious activity and do not require the use of instruments or reagents helpful for gene delivery but bear immunological and tumorigenic problems. In contrast, non-viral vectors strictly require instruments (i.e., electroporator) or reagents (i.e., liposomes) for enhanced uptake of NAs by cells and are often accompanied by weak transfection activity, with less immunological and tumorigenic problems. Chromosomal integration of GOI-bearing transgenes would be ideal for achieving long-term expression of GOI. piggyBac (PB), one of three transposons (PB, Sleeping Beauty (SB), and Tol2) found thus far, has been used for efficient transfection of GOI in various mammalian cells in vitro and in vivo. In this review, we outline recent achievements of PB-based production of genetically modified animals and organs and will provide some experimental concepts using this system.

Reprogramming Mouse Fibroblasts with piggyBac Transposons

In 2006, Shinya Yamanaka and his student Kazutoshi Takahashi showed that the expression of only four specific genes is sufficient to reprogram fully differentiated somatic cells into pluripotent stem cells. These cells, termed induced pluripotent stem (iPS) cells, share many of their characteristics with embryonic stem (ES) cells. In this protocol, we describe one of the simplest ways of generating iPS cells from mouse fibroblasts. It combines an efficient transposon-mediated transfection and the tetracycline-inducible system to control the expression of the Yamanaka reprogramming factors.