Characterization of telomerase activity in the human oocyte and preimplantation embryo

Telomerase, a ribonucleoprotein, has been described as an essential compone nt of highly proliferative cells as it stabilizes the telomeres and avoids cellular senescence. The objective of this study was to modify the polymera se chain reaction-based telomeric repeat amplification protocol to detect t elomerase activity in the single cell and to characterize the activity expr essed in the human oocyte through to the blastocyst stage embryo. A compara tive evaluation of telomerase activity and developmental stage was conducte d using discarded or donated human oocytes and embryos. Telomerase activity was detected in all developmental stages evaluated from immature oocytes t hrough to blastocyst stage embryos. Immature oocytes and blastocysts had si milar levels of telomerase activity; however, both groups had significantly (P < 0.05) higher activity than zygote through to pre-morula stage embryos . Seventy-five thawed zygotes were cultured to day 3, biopsied by removing 1-2 cells, and the biopsied embryos were cultured to blastocyst stage. Ther e was no difference (P < 0.05) in telomerase activity between cells biopsie d from embryos that reached the blastocyst stage and cells from those that arrested in growth. This study has shown that human oocytes through to blas tocyst stage embryos express telomerase activity, but that the level of tel omerase activity in biopsied blastomeres, of the day 3 cleavage stage embry o, is not predictive of embryonic growth potential.