Differences in the culturing conditions of mesenchymal stem cells used in regenerative medicine may affect their differentiation ability, genome instability, and therapeutic effects. In particular, bone marrow derived mesenchymal stem cells cultured under hypoxia are known to proliferate while maintaining an undiffer entiated state and the use of deferoxamine, a hypoxia mimetic reagent, has proven to be a suitable strategy to maintain the cells under hypoxic metabolic state. Here, the deferoxamine effects were investigated in mesenchymal stem cells to gain insights into the mechanisms regulating stem cell survival. A 12 h deferox amine treatment reduced proliferation, oxygen consumption, mitochondrial activity, and ATP production. Microarray analysis revealed that deferoxamine enhanced the transcription of genes involved in glycolysis and the HIF1α pathway. Among the earliest changes, transcriptional variations were observed in HIF1α, NUPR1, and EGLN, in line with previous reports showing that short deferoxamine treatments induce substantial changes in mesenchymal stem cells glycolysis pathway. NUPR1, which is induced by stress and involved in autophagy mediated survival, was upregulated by deferoxamine in a concentration dependent manner. Consistently, NUPR1 knockdown was found to reduce cell proliferation and increase the proapoptotic effect of stauro sporine, suggesting that deferoxamine induced NUPR1 promotes mesenchymal stem cell survival and cytoprotective autophagy. Our findings may substantially contribute to improve the effec tiveness of mesenchymal stem cell based regenerative medicine.

Hepatic stellate cells (HSCs) play a vital role in liver fibrosis, and a greater understanding of their regulation is required. Recent studies have focused on relationships between extracellular matrix (ECM) stiffness and gene expression or cellular metabolism, but none have provided a detailed metabolic analysis of HSC changes in spheroid cultures. Accordingly, in the present study, we created an HSC spheroid culture and analyzed changes in gene expression and metabolism. Expression of α-smooth muscle actin (α-SMA) decreased in the spheroids, suppressing proliferation. Gene expression analysis revealed the cell cycle, sirtuin signaling, mitochondrial dysfunction, and the Hippo pathway to be canonical pathways, believed to result from decreased proliferative ability or mitochondrial suppression. In the Hippo pathway, nuclear translocation of the yes-associated protein (YAP) was decreased in the spheroid, which was associated with the stiffness of the ECM. Metabolome analysis showed glucose metabolism changes in the spheroid, including glutathione pathway upregulation and increased lipid synthesis. Addition of the glycolytic product phosphoenolpyruvate (PEP) led to increased spheroid size, with increased expression of proteins such as α-SMA and S6 ribosomal protein (RPS6) phosphorylation, which was attributed to decreased suppression of translation. The results of our study contribute to the understanding of metabolic changes in HSCs and the progression of hepatic fibrosis.

Organisms living in temperate regions are sensitive to seasonal variations in the environment; they are known to accumulate energy as fat in their livers during the winter when days are shorter, temperatures are lower, and food is scarce. However, the effect of variations in photoperiod alone on hepatic lipid metabolism has not been well studied. Therefore, in this study, we analyzed lipid metabolism in the liver of medaka, Oryzias latipes, while varying the length of days at constant temperature. Larger amounts of fatty acids accumulated in the liver after 14 days under short‐day conditions than under long‐day conditions. Metabolome analysis showed no accumulation of long‐chain unsaturated fatty acids, but showed a significant accumulation of long‐chain saturated fatty acids. Short‐day conditions induced a reduction in the levels of succinate, fumarate, and malate in the tricarboxylic acid cycle, decreased expression of PPARα, and decreased accumulation of acylcarnitine, which suggested inhibition of lipolysis. In addition, transparent medaka fed on a high‐fat diet under short‐day conditions exhibited greater amounts of fat accumulation and developed fatty liver. The findings of our study will be useful for creating a medaka hepatic steatosis model for future studies of hepatic steatosis‐related diseases.

Organisms living in temperate regions are sensitive to seasonal variations in the environment; they are known to accumulate energy as fat in their livers during the winter when days are shorter, temperatures are lower, and food is scarce. However, the impact of variations in photoperiod alone on hepatic lipid metabolism has not been well-studied. Therefore, in this study, we analyzed lipid metabolism in the liver of medaka, Oryzias latipes, while varying the length of days at constant temperature. Larger amounts of fatty acids accumulated in the liver after 14 days under short-day conditions than under long-day conditions. Metabolome analysis showed no accumulation of the long-chain unsaturated fatty acids required at low temperatures, but showed a significant accumulation of long-chain saturated fatty acids. Short-day conditions induced decreased levels of succinate, fumarate, and malate in the tricarboxylic acid cycle, decreased expression of PPARα, and decreased accumulation of acylcarnitine, which suggested inhibition of lipolysis. In addition, when a high-fat diet was administered to transparent medaka under short-day conditions, larger amounts of fat accumulated and medaka with fatty liver were efficiently produced. Detailed analysis of the relationship between seasonal changes and hepatic steatosis will be important in the future as hepatic diseases become more prevalent in modern society; the findings obtained in our study will be useful for research studies pertaining to the relationship between photoperiod and disorders such as hepatic steatosis and non-alcoholic steatohepatitis.