萩原 玲子

Although the liver possesses remarkable regenerative capacity, the detailed chronology spanning the pre-proliferative preparatory stage, hepatocyte proliferation, liver weight recovery, and the completion of molecular regeneration has not been fully elucidated. Using microarray-guided histological validation, we investigated the temporally ordered physiological events underlying liver regeneration following 70% partial hepatectomy (PH) in C57BL/6 mice. Our results demonstrated that PH induced multiple functional pathways, including the response to stilbenoid, steroid hormone metabolism, lipid transport, and angiogenesis. This was followed by activation of endoplasmic reticulum (ER) stress and insulin processing, accompanied by lipid accumulation, suppression of xenobiotic catabolic capacity, and altered circulating cholesterol levels. After recovery of these processes, hepatocytes and sinusoidal endothelial cells entered the proliferative phase. Notably, although liver weight had returned to preoperative levels, the transcriptome remained distinct from baseline, revealing divergence between macroscopic recovery and molecular-level convergence. At 336 h, two of three samples were assigned to the baseline Cluster 1, whereas one sample remained in Cluster 6 with a small number of altered genes. Together, these findings provide a detailed temporal framework in which metabolic and tissue remodeling during liver regeneration extends beyond macroscopic recovery.

Avian adipocyte differentiation differs from mammalian adipocyte differentiation; however, no useful preadipocyte cell line has been established to study avian adipocyte differentiation. This study investigated whether dedifferentiated fat (DFAT) cells derived from chick mature adipocytes have the same characteristics as stromal vascular fraction (SVF) cells derived from adipose tissues and whether DFAT cells can be used as an avian preadipocyte cell line. The floating top layer, which contained mature adipocytes, was isolated from chick abdominal fat tissue by collagenase digestion and filtration. To induce spontaneous dedifferentiation, the isolated mature adipocytes were cultured using the ceiling culture method. After 14 days of culture, the proliferation and differentiation potential of the resulting DFAT cells was evaluated. The isolated mature adipocytes successfully dedifferentiated into DFAT cells and actively proliferated in ceiling culture. The proliferative capacity of DFAT cells was similar to that of the SVF cells, although the ability of DFAT cells to differentiate into mature adipocytes was significantly higher than that of SVF cells. Subcultured DFAT cells maintained normal proliferation and differentiation into adipocytes for at least 33 passages. This study demonstrated that chicken DFAT cells provide a readily established preadipocyte cell line derived from mature adipocytes, which can be used as a model for investigating adipogenic differentiation in chickens.

Here, we established dedifferentiated fat (DFAT) cells from mature bovine adipocytes and then examined the effects of volatile fatty acids on the differentiation of these DFAT cells into adipocytes in vitro. When mature adipocytes were isolated from bovine adipose tissue and cultured using the ceiling culture method, they were dedifferentiated into fibroblast-like cells without lipid droplets. These fibroblast-like cells, termed bovine DFAT (b-DFAT) cells, actively proliferated. After adipogenic induction, increased expression of adipocyte-specific genes occurred in b-DFAT cells and they redifferentiated into adipocytes with an accumulation of lipid droplets in their cytoplasm. The effects of volatile fatty acids on adipocyte differentiation in b-DFAT cells were also examined. Specifically, acetate, butyrate, and propionate added to adipogenic induction medium significantly enhanced the adipogenesis of b-DFAT cells compared with that observed in control cells; the addition of 10-3  mol of acetate enhanced adipogenesis of b-DFAT cells to the greatest extent. These results suggest that b-DFAT cells derived from bovine mature adipocytes are appropriate for the study of bovine adipocyte differentiation and that the optimum concentration treatment of acetate, a major energy source for ruminants, promotes adipogenesis of b-DFAT cells in vitro.

Mature adipocyte-derived dedifferentiated fat (DFAT) cells have been identified to possess similar multipotency to mesenchymal stem cells, but a method for converting DFAT cells into hepatocytes was previously unknown. Here, using comprehensive analysis of gene expression profiles, we have extracted three transcription factors, namely Foxa2, Hnf4a and Sall1 (FHS), that can convert DFAT cells into hepatocytes. Hepatogenic induction has converted FHS-infected DFAT cells into an epithelial-like morphological state and promoted the expression of hepatocyte-specific features. Furthermore, the DFAT-derived hepatocyte-like (D-Hep) cells catalyzed the detoxification of several compounds. These results indicate that the transduction of DFAT cells with three genes, which were extracted by comprehensive gene expression analysis, efficiently generated D-Hep cells with detoxification abilities similar to those of primary hepatocytes. Thus, D-Hep cells may be useful as a new cell source for surrogate hepatocytes and may be applied to drug discovery studies, such as hepatotoxicity screening and drug metabolism tests.