Low-Dose Ionizing γ-Radiation Promotes Proliferation of Human Mesenchymal Stem Cells and Maintains Their Stem Cell Characteristics

Mesenchymal stem cells (MSCs), which are multipotent and have self-renewal ability, support the regeneration of damaged normal tissue. A number of external stimuli promote migration of MSCs into peripheral blood and support their participation inwound healing. In an attempt to harness the potential beneficial effects of such external stimuli, we exposed human MSCs (hMSCs) to one such stimulus-low-dose ionizing radiation (LDIR)-and examined their biological properties. To this end, we evaluated differences in proliferation, cell cycle, DNA damage, expression of surface markers (CD29, CD34, CD90, and CD105), and differentiation potential ofhMSCs before and after irradiation with γ-rays generated using a ¹³⁷ CSirradiator.At doses less than 50 mGy, LDIR had no significant effect on the viability or apoptosis of hMSCs. Interestingly, 10 mGyofLDIR increased hMSC viability by 8% (p<0.001) comparedwith non-irradiatedhMSCs.At doses less than 50 mGy, LDIR did not induceDNA damage, including DNA strand breaks, or cause cellular senescence or cell-cycle arrest. Surface marker expression and in vitro differentiation potential of hMSCs were maintained after two exposures to LDIR at 10 mGy per dose. In conclusion, a two-dose exposure to LDIR at 10 mGy per dose not only facilitates proliferation of hMSCs, it alsomaintains the stem cell characteristics of hMSCswithout affecting their viability.These results provide evidence for the potential ofLDIRas an external stimulus for in vitro expansion of hMSCs and application in tissue engineering and regenerative medicine.

The Use of MTT Assay, In Vitro and Ex Vivo, to Predict the adiosensitivity of Colorectal Cancer / 대한방사선종양학회지

PURPOSE: The measurement of radiosensitivity of individuals is useful in radiation therapy. Unfortunately, the measurement of radiation survival using a clonogenic assay, which is the established standard, can be difficult and time consuming. The aim of this study is to compare radiosensitivity results obtained from the MTT and clonogenic assays, and to evaluate whether the MTT assay can be used on clinical specimens. MATERIALS AND METHODS: HCT-8, LoVo, CT-26, and WiDr were the colon cancer cell lines used for this study. The clonogenic assay was performed to obtain the cell survival curves and surviving fractions at a dose of 2 Gy (SF2) as the standard technique for radiosensitivity. Also, the MTT assay was performed for each of the cell lines (in vitro). To simulate clinical specimens, the cell lines were inoculated into nude mice, removed when the tumors reached 1 cm in diameter, and chopped. Next, the tumors were subjected to the same process involved with the MTT assay in vitro. The inhibition rates (IR) of 10 Gy or 20 Gy of irradiation for in vitro and ex vivo were calculated based on the optical density of the MTT assay, respectively. RESULTS: According to SF2 and the cell survival curve, the HCT-8 and WiDr cell lines were more resistant to radiation than LoVo and CT-26 (p<0.05). The IR was measured by in vitro. The MTT assay IR was 17.3%, 21%, 30% and 56.5% for the WiDr, HCT-8, LoVo and CT-26 cell lines, respectively. In addition, the IR measured ex vivo by the MTT assay was 23.5%, 26%, 38% and 53% in the HCT-8, WiDr, LoVo and CT-26 tumors, respectively. CONCLUSION: The radiosensitivity measured by the MTT assay was correlated with the measures obtained from the clonogenic assay. This result highlights the possibility that the MTT assay could be used in clinical specimens for individual radiosensitivity assays.

The micronucleus frequency in cytokinesis-blocked lymphocytes of cattle in the vicinity of a nuclear power plant

Cytogenetic and hematological analyses were performed on the peripheral blood lymphocytes (PBLs) obtained from Korean native cattle bred in the vicinity of three nuclear power plants (Wolsong, Uljin and Yeonggwang) and in a control area. The micronucleus (MN) rates for the cattle from the Wolsong, Uljin and Yeonggwang nuclear power plants and for the control area were 9.87 +/- 2.64, 8.90 +/- 3.84, 9.20 +/- 3.68 and 9.60 +/- 3.91 per 1,000 cytokinesis-blocked lymphocytes, respectively. The apparent difference is not statistically significant. The MN frequencies of PBLs from cattle bred in the four areas are within the background variation for this study. The MN frequencies and hematological values were similar regardless of whether the cattle were bred near a nuclear power plant or in the control area.

Vitamin D and estrogen receptor gene polymorphism and their interaction associated with bone mineral density in Korean postmenopausal women / 대한내과학회지

BACKGROUND: Strong genetic components to the determination of bone mineral density (BMD) have been suggested by family and twin studies. However, association between gene polymorphism and BMD was not consistent in Korean as well as other ethnic groups. The goal of present study is to evaluate the relationship between vitamin D receptor (VDR) and/or estrogen receptor (ER) gene polymorphism and BMD after adjusting for suggested confounding factors and the possibility of VDR gene by ER gene interaction which could impact the bone mass of Korean postmenopausal women. METHODS: We determined the VDR and ER genotypes using a polymerase chain reaction based Bsm I restriction length fragment polymorphism (RFLP) and Pvu II and Xba I RFLP respectively, in a population based DNA sample of 132 Korean postmenopausal women aged 45 to 71. And then related the VDR and ER genotypes to BMD, bone related hormones, biochemical bone markers, and clinical characteristics in these women. Multiple regression analysis was used to predict variables contributing to BMD. Age, height, weight, years since menopause, VDR B genotype, and ER P and X genotypes were used as independent variables. RESULTS: There was no significant relationship of VDR or ER genotypes to lumbar or femoral neck BMD, hormones, and bone turnover markers. However, after controlling for potential confounding factors, a statistically significant ER X genotype effect on femoral neck BMD (p=0.038), but not on lumbar BMD was observed. Moreover, there was more significant effect on femoral neck BMD by an interaction of VDR B * ER X genotype (p=0.013) in multiple regression analysis. CONCLUSION: The ER X genotype was associated with femoral neck BMD in Korean postmenopausal women. This association was more significant with the VDR B genotype interaction.

Dehydroepiandrosterone-dependent induction of peroxisomal proliferation can be reduced by aspartyl esterification without attenuation of inhibitory bone loss in ovariectomy animal model

The purpose of this study was to determine whether esterification of dehydroepiandrosterone with aspartate (DHEA-aspartate) could reduce peroxisomal proliferation induced by DHEA itself, without loss of antiosteoporotic activity. Female Sprague-Dawley rats were ovariectomized, then DHEA or DHEA-aspartate was administered intraperitoneally at 0.34 mmol/kg BW 3 times a week for 8 weeks. DHEA-aspartate treatment in ovariectomized rats significantly increased trabeculae area in tibia as much as DHEA treatment. Urinary Ca excretion was not significantly increased by DHEA or DHEA-aspartate treatment in ovariectomized rats, while it was significantly increased by ovariectomy. Osteocalcin concentration and alkaline phosphatase activity in serum and cross linked N-telopeptide type I collagen level in urine were not significantly different between DHEA-aspartate and DHEA treated groups. DHEA-aspartate treatment significantly reduced liver weight and hepatic palmitoyl-coA oxidase activity compared to DHEA treatment. DHEA-aspartate treatment maintained a nearly normal morphology of peroxisomes, while DHEA treatment increased the number and size of peroxisomes in the liver. According to these results, it is concluded that DHEA-aspartate ester has an inhibitory effect on bone loss in ovariectomized rats with a marked reduction of hepatomegaly and peroxisomal proliferation compared to DHEA.

The Effect of Estrogen on Antioxidant Enzymes in Bone of Oophorectomized Rats / 대한정형외과학회잡지

The purpose of this study is to evaluate an antioxidative effect of estrogen on the bone in oophorectomized rats. Thirty Sprague-Daley rats were equally divided into 3 groups; group 1 as control group with sham operation, group 2 as experimental group with oophorectomy, and group 3 as oophorectomized group treated with estrogen. Estradiol (5mg/kg BW) was administered three times per week from first to sixth week after oophorectomy. Left tibia was obtained to measure the amount of protein carbonyls as an index of oxidative stress and the activity of antioxidant enzymes. The results were as follows: trahecular bone area in proximal tihia decreased after oophorectomy, which increased in response to estrogen administration. The level of protein carbonylation in hone was not significantly different among all groups. Activity of antioxidant enzymes such ais glutathione reductase(GR), glutathione peroxidase(GP) and glutathione transferase(GST) in bone was not significantly different among all groups. However, the activity of catalase in bone markedly increased in group 3 compared with that in group 1 and group 2. In summary, bone trabecular area increased after admin- istration of estrogen. And estrogen induced the activitv of catalase, which might contrihute to prevent the oxidative damage. However, the glutathione utilizing enzymes such as GR, GP and GST were not significantly affected by estrogen status.

Induction of apoptosis by bile acids in HepG2 human hepatocellular carcinoma cells

We studied the effects of bile acids on the induction of apoptosis in HepG2 human hepatocellular carcinoma cells. Treatment with either ursodeoxycholic acid (UDCA) or lithocholic acid (LCA) resulted in a dose- and time-dependent decrease in cell viability assessed by MTT assay. Both UDCA and LCA also induced genomic DNA fragmentation, a hallmark of apoptosis, indicating that the mechanism by which these bile acids induce cell death was through apoptosis. Cycloheximide, a protein synthesis inhibitor, blocked the apoptosis induced by these bile acids, implying that new protein synthesis may be required for the apoptosis. Intracellular Ca2+ release blockers (dantrolene and 3,4,5-trimethoxybenzoic acid-8-(diethylamino)octyl ester) inhibited decreased cell viability and DNA fragmentation induced by these bile acids. Treatment of HepG2 cells with calcium ionophore A23187 induced DNA fragmentation. These results suggest that UDCA and LCA induce apoptosis in the HepG2 cells and that the activation of intracellular Ca2+ signals may play an important role in the apoptosis induced by these bile acids.

The role of fos oncogene protein on the induction of differentiation of F9 teratocarcinoma cells / 대한암학회지

No abstract available.