Toward Transgene-Free Induced Pluripotent Stem Cells: Lessons from Transdifferentiation Studies

Abstract

Regenerative medicine has received much attention over the years due to its clinical and commercial potential. The excitement around regenerative medicine waxes and wanes as new discoveries add to its foundation but are not immediately clinically applicable. The recent discovery of induced pluripotent stem cells has lead to a sustained effort from many research groups to develop clinically relevant regenerative medicine therapies. A major focus of cellular reprogramming is to generate safe cellular products through the use of proteins or small molecules instead of transgenes. The successful reprogramming of somatic nuclei to generate pluripotential cells capable of embryo development was pioneered over 50 years ago by Briggs and King and followed by Gurdon in the early 1960s. The success of these studies, the cloning of Dolly, and more current studies involving adult stem cells and transdifferentiation provide us with a large repository of potential candidate molecules and experimental systems that will assist in the generation of safe, transgene-free pluripotential cells.

Adult ciliary epithelial stem cells generate functional neurons and differentiate into both early and late born retinal neurons under non-cell autonomous influences

“…Reprogramming at this stage exposed their malleability to non-cell autonomous cues for retinal differentiation. Reprogramming of cells either by alterations of their microenvironment [57] or forced expression of specific transcription factors [58-60] may not extinguish parental gene expression completely, and thus emerges an important question if the residual expression would prevent functional lineage conversion. Our results demonstrate that not only the re-programmed cells are capable of generating functional neurons, as demonstrated by the acquisition of the electrophysiological characteristics, but also retinal neurons with some molecular, biochemical and functional attributes of RGCs and rod photoreceptors.…”

Cell Therapy Using Induced Pluripotent Stem Cells or Somatic Stem Cells: This is the Question

“…Specific cell culture conditions may promote changes in chromatin state, resulting in epigenetic reprogramming, in a similar manner to overexpression of a few key genes that allows the generation of iPS [32]. The induction of more cell plasticity in SSC allows obtaining a wide range of cell phenotypes that can be used potentially in distinct transplantation studies.…”

“…Another interesting approach is by using chemical stimulation instead of the addition of the reprogramming factors mentioned before [72,73]. However, efficiency of culture reprogramming in somatic cells is very low [32]. In this sense, not only the reprogramming strategies are important (genetic vs epigenetic induction), but also the potentiality properties of original cells (somatic cells vs SSC).…”

“…For instance, MSC could be in vitro culture reprogrammed to express neural phenotypes and downregulate mesenchymal markers [27][28][29][30][31]. This induction of a new cell fate involves non-genetic manipulation and it termed as epigenetic induction or in vitro culture reprogramming [32]. Therefore, these neural-like cells could be potentially used in neurodegenerative diseases.…”