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DNA topoisomerases-mediated DNA damages are generated from exogenous and endogenous effects, which need to be metabolized or repaired to maintain genome stability involving in many of repair enzymes. Tyrosyl-DNA phosphodiesterase 1 (TDP1) and tyrosyl-DNA phosphodiesterase 2 (TDP2) are two DNA repair enzymes discovered recently. TDP1 and TDP2 have the ability to hydrolyze the tyrosyl-phosphodiester bond of the phenol of tyrosine with 3'-and 5'-DNA end, respectively, which are contained in the metabolites of the damaged DNA mediated by topoisomerase 1 and topoisomerase 2, respectively. The abnormal activation and expression of TDP1 or TDP2 is the important reason for cancer development. Therefore, TDP1 and TDP2 have been regarded as potential targets in cancer therapy. In this review, we discuss the rationales of their potential as targets and development of their inhibitors together with topoisomerase poisons or DNA damaging agents.
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Objective To investigate the therapeutic effect of bone marrow mesenchymal stem cell (MSC)transplantation on cerebral ischemic reperfusion injury.Methods Sprague-Dawleye rat models of cerebral ischemiareperfusion injury were established with suture method.Ninety-six rats were divided into 4 groups:model group,MSC transplantation group,control group (injection of phosphate buffer saline,PBS) and sham operation group,with 24 rats in each group.The 6th generation of bone marrow MSCs cultured in vitro were selected and labeled with hoechst 33342,and then transplanted into rats through Penile vein 24 hours after the establishment of model.Equivalent PBS was injected into the control group.Neurological severity score (NSS) was assessed on the 2nd day,3rd day,4th day,8th day,15 th day,and the 22th day in each group.The plantation of MSC in the brain tissue was observed by fluorescence microscope.Furthermore,serial paraffin sections were subsequently stained with 2,3,5-triphenyl tetrazolium chloride,and immunohistochemistry stain with Nestin,neuron-specific enolase (NSE) and glial fibrillary acidic protein (GFAP),which could be used as the specific markers of neural stem cells,neurons and astrocytes.Results The distribution of blue fluorescent in the impaired brain tissue could be seen at 2 days after transplantation of MSC,and it reached the peak at the 15th day.The result of immunohistochemistry showed that the cells positive for Nestin,NSE or GFAP in the impaired local brain tissue were increased greatly in the MSC transplantation group compared with the model group and control group,and the differences were statistically significant (all P ＜ 0.05).The scope of cerebral infarction in the impaired brain tissue diminished from the 8th day in the MSC transplantation group,the score of NSS was also decreased evidently,the differences were statistically significant compared with the model group and control group (all P ＜ 0.05).Conclusions Bone marrow MSC transplantation can increase the number of neural stem cells,neurons and astrocytes in the location of cerebral ischemic reperfusion injuries,which may promote the repairment of nerve injury.
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Objective To explore whether human umbilical venous endothelial cells could be used as feeder layer to support the growth of embryonic stem cells (ESC) and keep ESC undifferentiated.Methods The venous vessels of umbilical cord obtained from healthy puerperal were perfused with collagenase.The isolated endothelial cells went through primary culture and passages for expansion.Factor Ⅷ antigens determination was implemented.Endothelial cells with good growth and 3 or above passages were treated with mitomycin-C(10 mg/L) and prepared as feeder layer,on which E14.1 ESC was transplanted for subculturing to observe the morphological characterization and determine ESC alkaline psphatase (AKP) activity and the expression of stem cell marker Oct-4.Severe combined immune deficiency(SCID) mouse in vivo terotoma formation experiment was performed to identify its pluripotent properties.Results Human umbilical vein-derived endothelial cells grew well in culturing in vitro and regenerate in large numbers.The endothelial cells maintained normal cellular morphological and biological characterization after 10 passages.The cells stopped proliferating after being treated with mitomycin-C,but its activity and morphological properties were well-maintained with 24 hours,which was a fundamental property of serving as feeder layer.E14.1 ESC remained undifferentiated in human umbilical venous endothelial cells after 3-8 passages,the cells grew in colony and showed high expression of AKP and stem cell Oct-4.In vivo pluripotency experiment showed that 6 weeks after being transplanted to SCID mice E14.1 ESC of 6 and 10 passages in endothelial cells both could form teratoma containing 3 layers of tissue cells.Conclusions Human umbilical venous endothelial cell serve as a convenient feeder layer cell with rich sources.It can effectively support ESC growth and heterogenous and prevent the heterogeneous protein pollution and pathogenic microorganisms caused by animal cell feeder layers,thus solve the problem of biological safety of ESC clinical application.
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Objective To explore hemodynamic parameter changes in pulmonary arterial hypertension(PAH)treated by transplantation of bone marrow mesenchymal stem cells(MMSCs)in the experimental rats.Methods MMSCs cells were collected from bone marrow of Sprague-Dawleye(SD)rat's femoral and tibial bones,cultured and passaged in vitro,then stained by Hoechst 33342 fluorescence dye stuff.Ninety healthy male SD rats were randomly divided into 3 groups(n=30):normal control group(group N),MMSCs transplanted group(group M),PAH model group(group H).The rats in the two latter groups were given a single subcutaneous crotaline(50 mg/kg)to establish the model of PAH.The rats of group N were injected respectively a single subcutaneous 9 g/L saline water(6 mL/kg).After 21 days,5?109 L-1 MMSCs cultured in 1 mL phosphate-buffered saline were infused into the rats respectively in group M by sublingual vein and 1 mL L-DMEM was given in group H.The indexalso of right ventricle systolic pressure(RVSP),right ventricle hypertrophy index,arterial blood gas analysis and the changes of small pulmonary blood vessel were observed after 28 days.Results The administration of MMSCs 28 days after PAH nearly completely prevented the increase in RVSP with PAH alone [(32.20?2.32)mmHg vs(48.30?1.56)mmHg P