Developmental toxicity of Cry1Ab protein in the embryonic stem-cell model / 北京大学学报(医学版)

ABSTRACT

Objective:To evaluate the developmental toxicity of Cry1Ab protein by studying its effects on cell proliferation and differentiation ability using a developmental toxicity assessment model based on embryonic stem-cell.Methods:Cry1Ab protein was tested in seven dose groups(31.25,62.50,125.00,250.00,320.00,1 000.00,and 2 000.00 μg/L)on mouse embryonic stem cells D3(ES-D3)and 3T3 mouse fibroblast cells,with 5-fluorouracil(5-FU)used as the positive control and phos-phate buffer saline(PBS)as the solvent control.Cell viability was detected by CCK-8 assay to calculate the 50％inhibitory concentration(IC50)of the test substance for different cells.Additionally,Cry1 Ab protein was tested in five dose groups(125.00,250.00,320.00,1 000.00,and 2 000.00 μg/L)on ES-D3 cells,with PBS as the solvent control and 5-FU used for model validation.After cell treatment,cardiac differentiation was induced using the embryonic bodies(EBs)culture method.The growth of EBs was observed under a microscope,and their diameters on the third and fifth days were measured.The proportion of EBs differentiating into beating cardiomyocytes was recorded,and the 50％inhibition con-centration of differentiation(ID50)was calculated.Based on a developmental toxicity discrimination func-tion,the developmental toxicity of the test substances was classified.Furthermore,at the end of the cul-ture period,mRNA expression levels of cardiac differentiation-related markers(Oct3/4,GATAA-4,Nkx2.5,and β-MHC)were quantitatively detected using real-time quantitative polymerase chain reaction(qPCR)in the collected EBs samples.Results:The IC50 of 5-FU was determined as 46.37 μg/L in 3T3 cells and 32.67 μg/L in ES-D3 cells,while the ID50 in ES-D3 cells was 21.28 μg/L.According to the discrimination function results,5-FU was classified as a strong embryotoxic substance.There were no sta-tistically significant differences in cell viability between different concentrations of Cry 1 Ab protein treat-ment groups and the control group in both 3T3 cells and ES-D3 cells(P＞0.05).Moreover,there were no statistically significant differences in the diameter of EBs on the third and fifth days,as well as their morphology,between the Cry1Ab protein treatment groups and the control group(P＞0.05).The cardi-ac differentiation rate showed no statistically significant differences between different concentrations of Cry1Ab protein treatment groups and the control group(P＞0.05).5-FU significantly reduced the mRNA expression levels of β-MHC,Nkx2.5,and GATA-4(P＜0.05),showing a dose-dependent trend(P＜0.05),while the mRNA expression levels of the pluripotency-associated marker Oct3/4 exhibited an increasing trend(P＜0.05).However,there were no statistically significant differences in the mRNA expression levels of mature cardiac marker β-MHC,early cardiac differentiation marker Nkx2.5 and GATA-4,and pluripotency-associated marker Oct3/4 between the Cry1Ab protein treatment groups and the control group(P＞0.05).Conclusion:No developmental toxicity of Cry1Ab protein at concen-trations ranging from 31.25 to 2 000.00 μg/L was observed in this experimental model.