Chromosomal information derived from single blastomeres isolated from cleavage-stage embryos and cultured in vitro

To evaluate the potential of proliferation of single blastomeres isolated from human cleavage-stage embryos for use in preimplantation genetic diagnosis of chromosomal abnormalities.

A laboratory study of chromosomal content of blastomeres isolated from embryos of patients from an in vitro fertilization program.

University hospital laboratory.

Couples undergoing IVF or ICSI.

Blastomeres were isolated from normally fertilized cleavage-stage human embryos, cultured in vitro or fixed immediately, and analyzed by fluorescence in situ hybridization (FISH) probes.

Chromosomal information yielded by blastomeres cultured in vitro compared with those obtained from blastomeres that were processed for chromosomal analysis directly after isolation.

The percentage of cultured blastomeres that produced FISH results was significantly lower than the percentage of blastomeres processed for FISH directly after isolation (72% vs. 90%). Lack of FISH results from cultured cells, which in most cases was related to nuclear anomalies, was significantly more frequent among nondivided than divided blastomeres (39% vs. 21%). Both cultured and noncultured cells showed diploid, aneuploid and polyploid chromosome complements on FISH. Compared with directly processed cells, cultured cells yielded a higher proportion of polyploid patterns (22.9% vs. 6.1%). Of the cultured blastomeres that divided, 18% produced progeny with mosaicism.

Although blastomere culture may increase the number of cells available for chromosomal analysis, the high frequency of nuclear defects and the occurrence of polyploidy and mosaicism among cultured cells discourage the use of blastomere isolation and proliferation strategy for use in preimplantation genetic diagnosis.