Abstract
Schwann cell development is hallmarked by the induction of a lipogenic profile. Here we used amniotic fluid stem (AFS) cells and focused on the mechanisms occurring during early steps of differentiation along the Schwann cell lineage. Therefore, we initiated Schwann cell differentiation in AFS cells and monitored as well as modulated the activity of the mechanistic target of rapamycin (mTOR) pathway, the major regulator of anabolic processes. Our results show that mTOR complex 1 (mTORC1) activity is essential for glial marker expression and expression of Sterol Regulatory Element-Binding Protein (SREBP) target genes. Moreover, SREBP target gene activation by statin treatment promoted lipogenic gene expression, induced mTORC1 activation and stimulated Schwann cell differentiation. To investigate mTORC1 downstream signaling we expressed a mutant S6K1, which subsequently induced the expression of the Schwann cell marker S100b, but did not affect lipogenic gene expression. This suggests that S6K1 dependent and independent pathways downstream of mTORC1 drive AFS cells to early Schwann cell differentiation and lipogenic gene expression. In conclusion our results propose that future strategies for peripheral nervous system regeneration will depend on ways to efficiently induce the mTORC1 pathway.
Highlights
Specialized glial cells, known as Schwann cells, are essential for correct development as well as maintenance of the peripheral nervous system (PNS) [1]
After 72 hours, cells were washed with PBS for 3 times and media was replaced with differentiation media consisting of a-MEM, 10% Fetal Bovine Serum (PAA, Austria), 20 ng/mL epidermal growth factor (EGF; Peprotech, UK), 20 ng/mL basic fibroblast growth factor, 5 mM forskolin (Sigma-Aldrich, USA), 5 ng/mL platelet-derived growth factor-AA (PDGF-AA; Peprotech, UK) and 200 ng/mL recombinant human heregulin-beta1 (HRG; Peprotech, UK)
Here we show for the first time that c-kit selected monoclonal amniotic fluid stem (AFS) cells can be induced by a three step protocol to express classic Schwann cell markers like nerve growth factor receptor (NGFR), glial fibrillary acidic protein (GFAP), nestin and S100b
Summary
Specialized glial cells, known as Schwann cells, are essential for correct development as well as maintenance of the peripheral nervous system (PNS) [1]. Amniotic fluid stem (AFS) cells are candidates as a novel stem cell source for Schwann cell differentiation. Since the discovery of Oct4-positive cells within human amniotic fluid [5], several studies have reported the broadly multipotent potential of these cells [6,7,8,9]. C-kit-selected AFS cells can be grown continuously in culture maintaining a stable karyotype and exhibiting high proliferative capacity [10,11]. While mesenchymal stem cells from the bone marrow of rats and humans were successfully differentiated towards Schwann cells [12,13], it is currently unknown whether monoclonal human c-kit and Oct4-positive immuno-selected AFS cells harbor the potential to give rise to Schwann cells
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