Hypoxia Supports Reprogramming of Mesenchymal Stromal Cells Via Induction of Embryonic Stem Cell–Specific microRNA-302 Cluster and Pluripotency-Associated Genes

Abstract

Pluripotency is characterized by specific transcription factors such as OCT4, NANOG, and SOX2, but also by pluripotency-associated microRNAs (miRs). Somatic cells can be reprogrammed by forced expression of these factors leading to induced pluripotent stem cells (iPSCs) with characteristics similar to embryonic stem cells (ESCs). However, current reprogramming strategies are commonly based on viral delivery of the pluripotency-associated factors, which affects the integrity of the genome and impedes the use of such cells in any clinical application. In an effort to establish nonviral, nonintegrating reprogramming strategies, we examined the influence of hypoxia on the expression of pluripotency-associated factors and the ESC-specific miR-302 cluster in primary and immortalized mesenchymal stromal cells (MSCs). The combination of hypoxia and fibroblast growth factor 2 (FGF2) treatments led to the induction of OCT4 and NANOG in an immortalized cell line L87 and primary MSCs, accompanied with increased doubling rates and decreased senescence. Most importantly, the endogenous ECS-specific cluster miR-302 was induced upon hypoxic culture and FGF2 supplementation. Hypoxia also improved reprogramming of MSCs via episomal expression of pluripotency factors. Thus, our data illustrate that hypoxia in combination with FGF2 supplementation efficiently facilitates reprogramming of MSCs.

Inhibition of miR‐302 Suppresses Hypoxia‐Reoxygenation‐Induced H9c2 Cardiomyocyte Death by Regulating Mcl‐1 Expression

“…The binding of the seed sequence in miRs to a complementary sequence in the mRNA 3′UTR promotes mRNA degradation, whereas failure to bind due to the sequences not being complementary can result in translation inhibition [21]. miR-302 transcriptionally regulates gene expression and methylation [22] and supports reprogramming in stem cells during hypoxia [23, 24]. As a putative upstream regulator of Mcl-1 expression, the role of miR-302 in protecting cardiomyocytes from H/R remains unknown.…”

Significant improvement of direct reprogramming efficacy of fibroblasts into progenitor endothelial cells by ETV2 and hypoxia

“…Several studies have reported that hypoxia could improve reprogramming of cells. Foja et al [ 46 ] showed that hypoxia improved the reprogramming of MSCs into induced pluripotent stem cells (iPSCs). Adipose stem cells were also stimulated for reprogramming to iPSCs by hypoxia [ 47 ].…”

Concise Review: Harmonies Played by MicroRNAs in Cell Fate Reprogramming

“…Hypoxia, which stimulates glycolysis, has been reported to induce a human ESC‐like transcriptional signature in several cancer cell lines, upregulating NANOG, OCT4, SOX2, KLF4, c‐MYC, and the miR‐302 cluster . It was also shown to activate the miR‐302 cluster and other pluripotency TFs during iPSC production . These findings explain, at least partially, why iPSC generation is enhanced under hypoxic conditions .…”