mTORC1 Is Essential for Early Steps during Schwann Cell Differentiation of Amniotic Fluid Stem Cells and Regulates Lipogenic Gene Expression

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.

Inhibition of glycogen synthase kinase-3 (GSK3) promotes the neural differentiation of full-term amniotic fluid-derived stem cells towards neural progenitor cells

“…Previous studies have shown that hAFS cells could either differentiate into neural cells in vitro or produce neurotrophic factors in vivo (Chen et al, 2015;Preitschopf et al, 2014). Research on neural differentiation capability of adult stem cells found that hAFS cells could respond to neural induction faster.…”

Rapamycin-Induced Hypoxia Inducible Factor 2A Is Essential for Chondrogenic Differentiation of Amniotic Fluid Stem Cells

“…High Oct4‐expressing single‐cell clones, derived from the CD117/2 population, were used in this study [21]. Cells were maintained in Chang media, as previously described [21].…”

“…High Oct4‐expressing single‐cell clones, derived from the CD117/2 population, were used in this study [21]. Cells were maintained in Chang media, as previously described [21]. Chondrocytes were provided by Danube University Krems and were cultured in Dulbecco's modified Eagle's medium (DMEM; Thermo Fisher Scientific, Waltham, MA, https://www.thermofisher.com) supplemented with 10% fetal calf serum, 2.5 mM l ‐glutamine (GE Healthcare, Pasching, Austria, http://www3.gehealthcare.com), 50 mg/l streptomycin sulfate (GE Healthcare), 30 mg/l penicillin (GE Healthcare), and 50 µg/ml ascorbic acid.…”

“…Total RNA was isolated from differentiated pellets on indicated days according to the manufacturer's instructions (Peqlab, Erlangen, Germany, https://de.vwr.com). cDNA synthesis and polymerase chain reaction (PCR) were performed as described [21]. The human primers used are listed in supplemental online Table 1.…”

“…Proteins of AFS cells, human chondrocytes, and chondrogenic differentiated pellets were harvested as previously described [21]. The following antibodies were used: from Cell Signaling Technology: rabbit antiphosphorylated S6 ribosomal protein S240/244 (1:10,000; catalog no.…”