BackgroundRising CO2 concentration was reported to increase phytoplankton growth rate as well as lipid productivity. This has raised questions regarding the NADPH supply for high lipid synthesis as well as rapid growth of algal cells.ResultsIn this study, growth, lipid content, photosynthetic performance, the activity, and expression of key enzymes in Calvin cycle and oxidative pentose phosphate pathway (OPPP) were analyzed in the marine diatom Phaeodactylum tricornutum under three different CO2 concentrations (low CO2 (0.015 %), mid CO2 (atmospheric, 0.035 %) and high CO2 (0.15 %)). Both the growth rate and lipid content of P. tricornutum increased significantly under the high CO2 concentration. Enzyme activity and mRNA expression of three Calvin cycle-related enzymes (Rubisco, 3-phosphoglyceric phosphokinase (PGK), phosphoribulokinase (PRK)) were also increased under high CO2 cultivation, which suggested the enhancement of Calvin cycle activity. This may account for the observed rapid growth rate. In addition, high activity and mRNA expression of G6PDH and 6PGDH, which produce NADPH through OPPP, were observed in high CO2 cultured cells. These results indicate OPPP was enhanced and might play an important role in lipid synthesis under high CO2 concentration.ConclusionsThe oxidative pentose phosphate pathway may participate in the lipid accumulation in rapid-growth P. tricornutum cells in high CO2 concentration.

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Tissue engineering is a rapidly growing technological area for the regeneration and reconstruction of damage to the central nervous system. By combining seed cells with appropriate biomaterial scaffolds, tissue engineering has the ability to improve nerve regeneration and functional recovery. In the present study, mouse induced pluripotent stem cells (iPSCs) were generated from mouse embryonic fibroblasts (MEFs) with the non-integrating episomal vectors pCEP4-EO2S-ET2K and pCEP4-miR-302-367 cluster, and differentiated into neural stem cells (NSCs) as transplanting cells. Electrospinning was then used to fabricate randomly oriented poly(L-lactic acid) (PLLA) nanofibers and aligned PLLA nanofibers and assessed their cytocompatibility and neurite guidance effect with iPSC-derived NSCs (iNSCs). The results demonstrated that non-integrated iPSCs were effectively generated and differentiated into iNSCs. PLLA nanofiber scaffolds were able to promote the adhesion, growth, survival and proliferation of the iNSCs. Furthermore, compared with randomly oriented PLLA nanofibers, the aligned PLLA nanofibers greatly directed neurite outgrowth from the iNSCs and significantly promoted neurite growth along the nanofibrous alignment. Overall, these findings indicate the feasibility of using PLLA nanofiber scaffolds in combination with iNSCs in vitro and support their potential for use in nerve tissue engineering.