We investigated the capacity'of a clonal osteogenic cell line MC3T3-EI, established from newborn mouse calvaria and selected on the basis of high alkaline phosphatase (ALP) activity in the confluent state, to differentiate into osteoblasts and mineralize in vitro. The cells in the growing state showed a fibroblastic morphology and grew to form multiple layers. On day 21, clusters of cells exhibiting typical osteoblastic morphology were found in osmiophilic nodular regions. Such nodules increased in number and size with incubation time and became easily identifiable with the naked eye by day 40-50. In the central part of well-developed nodules, osteocytes were embedded in heavily mineralized bone matrix. Osteoblasts were arranged at the periphery of the bone spicules and were surrounded by lysosome-rich cells and a fibroblastic cell layer. Numerous matrix vesicles were scattered around the osteoblasts and young osteocytes. Matrix vesicles and plasma membranes of osteoblasts, young osteocytes, and lysosome-rich cells showed strong reaction to cytochemical stainings for ALP activity and calcium ions. Minerals were initially localized in the matrix vesicles and then deposited on well-banded collagen fibrils. Deposited minerals consisted exclusively of calcium and phosphorus, and some of the crystals had matured into hydroxyapatite crystals. These results indicate that MC3T3-EI cells have the capacity to differentiate into osteoblasts and osteocytes and to form calcified bone tissue in vitro.Recently, we established eight cell lines from newborn mouse calvaria and selected a clone, designated MC3T3-EI, from one of these lines on the basis of its high alkaline phosphatase (ALP) activity in the resting state (l). Cells of this clonal line had very low ALP activity in the growing state, but enzyme activity increased several hundredfold after cultures reached a confluent state. The cells produced abundant fibrous intercellular substances. In addition, intercellular spaces in day-30 cultures stained positively with alizarin red S. These observations suggest that MC3T3-EI cells are an osteogenic cell line, having the capacity to differentiate into osteoblasts and deposit minerals in vitro.We undertook the studies described here to further characterize the process of differentiation of MC3T3-E1 cells and calcification in vitro. We found that calcified bone tissue was formed in MC3T3-E 1 cultures by a process closely resembling that observed in intramembranous osteogenesis in vivo. Mineral deposits were identified as hydroxyapatite by energy dispersive x-ray analysis and electron diffraction analysis. MATERIALS AND METHODSCell Culture: The MC3T3-EI cells were grown in alpha modification of Eagle's minimal essential medium (a-MEM) (Flow Laboratories, McLean, VA) supplemented with 10% newborn calf serum (Flow Lab., Stanmore, New South Wales, Australia) and 60 lag/ml of kanamycin sulfate (Meiji Seika, Tokyo, Japan). CelLs were maintained at 37°C in a fully-humidified atmosphere of 5% CO2 in air and subcultured every 3 ...

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We established a clonal preadispose cell line from newborn mouse calvaria. Cells of this cell line, designated MC3T3-G2/PA6, had the capacity to convert to adipose cells, to accumulate triglycerides in their cytoplasm, and to mature to differentiated fat cells in a resting state. This adipose conversion was markedly accelerated by addition of dexamethasone, which was the most potent inducer among the steroid hormones tested. The presence of dexamethasone was needed during the steroid hormones tested. The presence of dexamethasone was needed during logarithmic growth phase for maximal conversion. The frequency of adipose conversion was dependent on exposure time to the hormone, but cells already committed to differentiation continued to accumulate lipid and developed into mature adipose cell even in its absence. This indicates that the hormone accelerates the initiation of the adipose conversion, but is not required for the ongoing conversion process. In fact, it was rather inhibitory for the process of fat accumulation. Insulin alone slightly inhibited the adipose conversion, but its combination with dexamethasone neutralized the above inhibitory effect of dexamethasone. The responsiveness of this cell line is consistent with that observed for mouse bone marrow preadipocytes in primary culture but differs from that for preadipose cell lines derived from extramedullary tissues. These results strongly suggest that the MC3T3-G2/PA6 cell line was derived from bone marrow.

A clonal preadipose cell line MC3T3-G2/PA6, established from newborn mouse calvaria, responds to glucocorticoids and converts to adipose cells in a fashion similar to bone marrow preadipocytes. We investigated the effect of the cells on in vitro hemopoiesis of mouse bone marrow cells by cocult~vation. When bone marrow cells were inoculated into confluent cultures of MC3T3-G2/PA6 cells (104-106 celM25-cm2 flask), the number of hemopoietic stem cells (CFU-S) significantly increased during 7-day cultivation in proportion to inoculum size. Under these conditions, active replication of CFU-S was maintained for several weeks until MC3T3-G2/PA6 cell layers detached from the substratum. This capacity of the MC3T3-G2/PA6 line was unique because other established cell lines, including the MTF preadipose line, failed to support CFU-S growth. When bone marrow cells were not allowed to contact the MC3T3-GZiPA6 cell layer, only a small number of CFU-S survived for 7 days. Moreover, MC3T3-G2/PA6 cell-conditioned medium did not show any growth-promoting activity for CFU-S. These results indicate that the MC3T3-G2/PA6 cell line has the ability to promote the proliferation of CFU-S through a short range cell-to-cell interaction by providing an in vitro microenvironment probably similar to that for in vivo hemopoiesis.

The clonal preadipose cell line, MC3T3-G2/PA6, has the capacity to differentiate into adipocytes in response to glucocorticoids and to support in vitro growth of hemopoietic stem cells (CFU-S). To study the relationship between these capacities, we precultured the MC3T3-G2/PA6 cells for varying days in the presence or absence of dexamethasone and then cocultured them with mouse bone marrow cells. Logarithmically growing cultures contained no detectable adipocytes and showed the highest growth-supporting activity for CFU-S, whereas cultures containing the largest number of adipocytes showed the lowest activity. When bone marrow cells were seeded onto 3-day-old MC3T3-G2/PA6 preadipocyte layers at 1 X 10(5) cells/35-mm dish, day 12 CFU-S grew with a population doubling time of about 37 hr, and at least 75% of them were associated with the cell layer between days 2 and 7. In the absence of the preadipocytes, CFU-S were not detected in the adherent cell fraction and decreased with a half-life of about 18 hr. More than 80% of CFU-C were also found to be associated with the preadipocyte layer, and they increased about 24-fold in number during 7 days in culture. Morphologically, hemopoietic cells developing into mature granulocytes and macrophages were distributed between the layers of preadipocytes. Dendritic processes of preadipocytes were frequently in close alignment with the hemopoietic cells. However, adipocytes failed to show such an intimate association with hemopoietic cells. These results indicate that MC3T3-G2/PA6 cells in the preadipocyte stage, but not in the adipocyte stage, have the capacity to support CFU-S growth, and that hemopoiesis in our cocultivation system proceed within the microenvironmental milieu provided by MC3T3-G2/PA6 preadipocytes.

Abstract. We investigated the antidiabetic effects of E3030, which is a potent dual activator of peroxisome proliferator-activated receptor (PPAR) α and PPARγ, in an animal model of diabetes, C57BL / KsJ-db/ db mice (db / db mice), and the lipidemic effects of E3030 in beagle dogs, whose PPARα and PPARγ transactivation responses to E3030 were similar to those of humans. E3030 activated human PPARα, mouse PPARα, dog PPARα, human PPARγ, mouse PPARγ, and dog PPARγ with EC 50 values of 65, 920, 87, 34, 73, and 34 nM, respectively, in the chimeric GAL4-PPAR receptor transactivation reporter assay. In db / db mice orally administered E3030 decreased blood glucose, triglyceride (TG), non-esterified fatty acids (NEFA), and insulin levels and increased blood adiponectin levels during a 14-day experimental period. Significant effects on blood glucose and adiponectin levels were observed at a dose of 3 mg / kg or greater. Furthermore, significant effects on blood TG, NEFA, and insulin levels were observed at doses of 1 mg / kg or more. An oral glucose tolerance test (OGTT) performed on Day 15 showed that E3030 at 3 mg / kg improved glucose tolerance in this model. Fourteen days of oral treatment with E3030 at a dose of 0.03 mg / kg or greater showed remarkable TG-and non high-density lipoprotein (non-HDL) cholesterol-lowering effects in beagle dogs. These results were similar to those observed for the PPARα agonist fenofibrate. E3030 also reduced apo C-III levels on Days 7 and 14, and elevated lipoprotein lipase (LPL) levels on Day 15. These results indicate that the TG-and non-HDL cholesterol-lowering actions of E3030 involve combined effects on reduction of apo C-III and elevation of LPL, resulting in increased lipolysis. The experimental results in animals suggest that E3030 has potential for use in the treatment of various aspects of metabolic dysfunction in type 2 diabetes, including dyslipidemia, hyperglycemia, hyperinsulinemia, and impaired glucose disposal.

Oxidative stress affects bone turnover. Preventative effects of antioxidants such as vitamin E on reduced bone mineral density and fractures associated with aging, osteoporosis, and smoking have been examined in animals and humans. The effects of vitamin E (α-tocopherol; αT) on bone health have yielded conflicting and inconclusive results from animal studies. In this study, to determine the bone effects of αT, we investigated the in vivo effects of αT on the bone mineral density, bone mass, bone microstructure, bone resorption, and osteogenesis through peripheral quantitative computed tomography (pQCT) measurements, micro-computed tomography (micro-CT) analyses, and bone histomorphometry of lumbar vertebrae and femurs in normal female Wistar rats fed diets containing αT in different quantities (0, 30, 120, or 600 mg/kg diet) for 8 weeks. To validate our hypotheses regarding bone changes, we examined ovariectomized rats as an osteoporosis model and control sham-operated rats in parallel. As expected, ovariectomized rats had reduced bone mineral density in lumbar vertebrae and the distal metaphyses of their femurs, reduced bone mass and deteriorated microstructure of cancellous bones in the vertebral body and distal femur metaphyses, and reduced bone mass due to resorption-dominant enhanced bone turnover in secondary cancellous bones in these sites. In comparison, αT administered to normal rats, even at the highest dose, did not induce reduced bone mineral density of lumbar vertebrae and femurs or a reduced bone mass or fragile microstructure of cancellous bones of the vertebral body and distal femur metaphyses. Instead, αT-fed rats showed a tendency for an osteogenesis-dominant bone mass increase in secondary cancellous bones in the vertebral body, in which active bone remodeling occurs. Thus, αT consumption may have beneficial effects on bone health.

The response of fibroblasts to the conversion of fibrinogen into fibrin was investigated to clarify the relationship between the conversion and wound healing. The formation of fibrin by thrombin little affected fibroblast attachment and morphology. In contrast cells rapidly attached and subsequently spread on fibrin cross-linked by activated Factor XIII. The introduction of cross-linking also stimulated cell proliferation. However neither enzyme had much effect on cellular behavior. These results indicate that the introduction of cross-linking by activated Factor XIII directly promotes the cellular responses, and suggest that the formation of fibrin stabilized by cross-linking plays a significant role not only in stoppage of blood flow but also in subsequent migration and proliferation of fibroblasts.