Mitochondrial Dynamics Is Critical for the Full Pluripotency and Embryonic Developmental Potential of Pluripotent Stem Cells.

While the pluripotency of stem cells is known to determine the fate of embryonic development, the mechanisms underlying the acquisition and maintenance of full pluripotency largely remain elusive. Here, we show that the balance between mitochondrial fission and fusion is critical for the full pluripotency of stem cells. By analyzing induced pluripotent stem cells with differential developmental potential, we found that excess mitochondrial fission is associated with an impaired embryonic developmental potential. We further uncover that the disruption of mitochondrial dynamics impairs the differentiation and embryonic development of pluripotent stem cells; most notably, pluripotent stem cells that display excess mitochondrial fission fail to produce live-born offspring by tetraploid complementation. Mechanistically, excess mitochondrial fission increases cytosolic Ca2+ entry and CaMKII activity, leading to ubiquitin-mediated proteasomal degradation of ß-Catenin protein. Our results reveal a previously unappreciated fundamental role for mitochondrial dynamics in determining the full pluripotency and embryonic developmental potential of pluripotent stem cells.

Phosphatidic Acid Improves Reprogramming to Pluripotency by Reducing Apoptosis.

Generation of induced pluripotent stem cells (iPSCs) requires a considerable amount of lipids, such as phosphatidic acid (PA), to meet the needs of subsequent rapid cell division and proliferation. However, it is unclear whether PA, a biosynthetic precursor of lipids, affects reprogramming. By using lentiviral expression of the Yamanaka factors in mouse embryonic fibroblasts for reprogramming, we identified that PA is beneficial for the generation of iPS colonies. Inhibiting the generation of cellular PA dramatically decreased the number of iPSCs. Consistently, 400 µM PA improved iPSC generation by more than 4- to 5-fold. iPSCs generated in the presence of PA (PA-iPS) expressed pluripotent markers such as Oct4 and Nanog, differentiated into cells of the three germ layers in vitro, and contributed to chimeric mice when injected into blastocysts. The improved efficiency was primarily due to reduction of apoptosis as sufficient PA increased the accumulation of cardiolipin in the inner membrane of the mitochondria, which reduced the release of cytochrome c and, in turn, suppressed apoptosis by inhibiting caspase-7. The relatively higher amount of Bcl-2 in PA treatment also inhibited apoptosis. In addition, an accompanied sequential change from epithelial-to-mesenchymal transition (EMT) at the initial phase of reprogramming to mesenchymal-to-epithelial transition (MET) was also detected. Our microarray data, which also supported our results, indicated the presence of significant membrane enrichment genes, thus suggesting that PA may function through membrane-anchored proteins. We thus identified a novel type of culture supplement that improves the efficiency of reprogramming and could be valuable for the generation of high-quality iPS cells.