Effect of Aging on Telomere Lengths in Bovine Oocytes and Granulosa Cells

Abstract: Age-associated telomere shortening in oocytes and granulosa cells is considered a sign of ageassociated decline in oocyte quality. The present study examined the effect of aging on telomere lengths (TLs) in bovine oocytes, embryos, and granulosa cells, as well as the relationship between the TLs in oocytes and granulosa cells. TL was directly assessed by real-time PCR, using a telomeric standard of 84 bp length TTAGGG, repeated 14 time). TLs in immature oocytes derived from early antral follicles (EAFs) and antral follicles (AFs) as well as for in vitro matured oocytes derived from aged cows (>120 months) were shorter than their respective counterparts in younger cows (20–70 months, 0.45-, 0.82-, and 0.84- fold, respectively, P < 0.05). Telomeres elongate extensively during embryo development until the blastocyst stage (4.2-fold, P < 0.05); however, TLs in the blastocysts did not differ between the two age groups. TLs in the granulosa cells of both AFs and EAFs were shorter in aged cows than in younger cows, and showed a positive correlation with TLs in oocytes (r=0.66, P < 0.05). In conclusion, aging affects TL in oocytes, and the TLs in granulosa cells and oocytes are correlated.