OBJECTIVETo study the effect of methotrexate (MTX), a folic acid antagonist which can lead to folic acid deficient, on the cardiac development and on the expressions of BMP2b and HAS2 in zebrafish.

METHODSThe zebrafish embryos at 6-48 hrs post fertilization (hpf) were treated with various concentrations of MTX (0.5 x 10(-3), 1.0 x 10(-3) and 2.0 x 10(-3) M). At 48 hpf, the percentage of cardiac malformation and heart rate were recorded. The zebrafish embryos at 6-10 hpf treated with 1.5 x 10(-3) M MTX were used as the MTX treatment group. At 24 and 48 hpf the cardiac morphology was observed under a microscope. The expressions of BMP2b and HAS2 in zebrafish were detected by in situ antisense RNA hybridization and real-time PCR.

RESULTS6-12 hpf, the early embryonic developmental stage, was a sensitive period that MTX affected cardiac formation of zebrafish. The retardant cardiac development and the evidently abnormal cardiac morphology was found in the MTX treatment group. The results of in situ antisense RNA hybridization showed that the expressions of BMP2b and HAS2 in the zebrafish heart were reduced in the MTX treatment group at 36 and 48 hpf. The real-time PCR results demonstrated that the BMP2b expression decreased at 12, 24, 36 and 48 hpf, and that the HAS2 expression decreased at 24, 36 and 48 hpf in the treatment group compared with the control group without MTX treatment.

CONCLUSIONSThe inhibition of folic acid function may affect cardiac development of early embryos, resulting in a retardant development and a morphological abnormality of the heart in zebrafish, possibly by down-regulating the expressions of BMP2b and HAS2.