Direct Reprogramming of Fibroblasts into Neural Stem Cells by Defined Factors

Abstract

Recent studies have shown that defined sets of transcription factors can directly reprogram differentiated somatic cells to a different differentiated cell type without passing through a pluripotent state, but the restricted proliferative and lineage potential of the resulting cells limits the scope of their potential applications. Here we show that a combination of transcription factors (Brn4/Pou3f4, Sox2, Klf4, c-Myc, plus E47/Tcf3) induces mouse fibroblasts to directly acquire a neural stem cell identity-which we term as induced neural stem cells (iNSCs). Direct reprogramming of fibroblasts into iNSCs is a gradual process in which the donor transcriptional program is silenced over time. iNSCs exhibit cell morphology, gene expression, epigenetic features, differentiation potential, and self-renewing capacity, as well as in vitro and in vivo functionality similar to those of wild-type NSCs. We conclude that differentiated cells can be reprogrammed directly into specific somatic stem cell types by defined sets of specific transcription factors.

Specification of functional neurons and glia from human pluripotent stem cells

“…Transdifferentiation from other type of somatic cells into functional neurons has allowed the generation of mature neurons in a relatively shorter period, which seems to be an ideal source of cells for transplantation, nevertheless, the efficiency of transdifferentiation is low, and the iNs are not expandable for large quantity. Alternative procedures that convert other type of somatic cells into expandable neural stem cells are also under extensive exploration (Kim et al, 2011;Han et al, 2012;Lujan et al, 2012;Ring et al, 2012;Sheng et al, 2012;Thier et al, 2012). In contrast to the iNs, the induced neural stem cells (iNSCs) are capable to proliferate, thus allow yield of larger quantity of cells through selectively amplification of the induced neural stem cells.…”

Direct lineage conversion: induced neuronal cells and induced neural stem cells

“…More recently, several independent groups have shown that a combination of transcription factors could directly reprogram mouse fibroblasts toward stably expandable induced neural stem cells (Han et al, 2012;Thier et al, 2012). These studies present alternative strategies for reprogramming somatic cells to neural stem cell identity.…”

“…Han et al showed that reprogramming with a combination of transcription factors (Brn4/Pou3f4, Sox2, Klf4, c-Myc, plus E47/Tcf3) directly induced neural stem cell identity in mouse fibroblasts and that iNS cells did not generate teratomas after injection into immunosuppressed mice (Han et al, 2012). The multipotent iNS cells display NS cell morphology, differentiation capacity, and self-renewing potential with gene expression features and epigenetic profiles similar to those of brain-derived NS cells.…”

“…Furthermore, somatic cells other than fibroblasts have been directly converted into other cell types, and even direct endoderm-to-ectoderm switching has been achieved . It has been also demonstrated that fibroblasts can be reprogrammed into neural stem cells (Kim et al, 2011a;Han et al, 2012;Thier et al, 2012). In this review, we will discuss these recent studies in iN cells and iNS cells conversion from terminally differentiated cells by different combinations of transcription factors (Fig.…”

Stem cells: from biomedical research towards clinical applications

“…iPS cells exhibit properties very similar to ES cells and can give rise to an entire organism. Similarly, fibroblasts are readily reprogrammed into neural cells and neural stem cells by expression of yet another sets of transcription factors [3][4][5]. Furthermore, procedures were developed that allow the development of three-dimensional organ-like structures in vitro from tissue-resident adult stem cells or pluripotent stem cells, referred to as organoids [6,7].…”