Mitogenic and cytogenetic evaluation of transforming growth factor-β on murine preimplantation embryonic development in vitro

Abstract

Slow cleavage rate has been a major contributory factor influencing embryo morphology in in vitro fertilization (IVF) programs. The role of transforming growth factor-β (TGFβ 1) in improving this characteristic was evaluated using the murine model. Replicate batches of eight-cell compacting embryos from superovulated mice were divided into three groups. Group A were treated with 0.3 ng/ml TGFβ 1 at the initial compacting stage, followed by a second treatment of 0.1 ng/mL 22 h later at the cavitating stage; group B received 0.3 ng/ml TGFβ 1 at the cavitating stage; group C were controls. The percentages of treated embryos reaching fixed embryonic stages, total cell number (TCN), mitotic index, and incidence of chromosome anomalies were monitored. The percentage of embryos reaching the cavitating, expanded, hatching, and hatched stages in both treatment groups were not significantly different from control (96.6% ± 4.2% to 37.7% ± 12.7% vs. 95.3% ± 7.3% to 47.0% ± 3.5%; P > 0.05). Values between the two treatment groups were also not significantly different. Embryos in groups A and B produced significantly greater TCN at expanded blastocyst and hatching stages compared to controls (Group A: 107.0 ± 18.9 vs. 89.9 ± 17.4, P < 0.05 and 125.5 ± 16.4 vs. 113.9 ± 12.1, P < 0.05; Group B: 107.9 ± 14.0 vs. 89.9 ± 17.4, P < 0.05 and 124.9 ± 17.4 vs. 113.9 ± 12.1, P < 0.05). Values, however, were not significantly different between treatment groups. The mean mitotic index for eight-cell compacting embryos treated with a single dose of 0.3 ng/ml TGFβ 1 was significantly greater than control (0.1944 ± 0.1376 vs. 0.1282 ± 0.2573, P < 0.05). No significant increase in the incidence of chromosome anomalies was observed in embryos exposed to TGFβ 1. The results demonstrate that TGFβ 1 had a tremendous mitogenic effect on late murine embryonic stages and may thus be useful to improve embryo morphology in IVF programs and to produce adequate metaphases from biopsied embryos for preimplantation cytogenetic diagnosis.