Co-culture of buffalo (Bubalus bubalis) preantral follicles with antral follicles: a comparative study of developmental competence of oocytes derived from in vivo developed and in vitro cultured antral follicles

The present study was undertaken to examine whether the presence of antral follicles (AFs) affects the survival, growth and steroidogenesis of preantral follicles (PFs) and compare the maturation and developmental competence of buffalo oocytes derived from in vivo developed and in vitro cultured AFs. Two experiments were carried out. In experiment I, PFs (200-250 mu m) were isolated and cultured with or without AFs (3-5 mm) in TCM-199 medium that contained 10% fetal bovine serum (FBS), 1% insulin transferin selenium (ITS), 20 ng/ml epidermal growth factor (EGF), 0.5 mu g/ml follicle-stimulating hormone (FSH) and 100 ng/ml insulin-like growth factor (IGF)-I. In experiment II, in vitro developmental competence was compared for the cumulus-oocyte complexes (COCs) recovered from in vivo developed and in vitro cultured AFs. Survival, growth, development of antrum, accumulation of estradiol and progesterone was (P < 0.05) higher when PFs were co-cultured with AFs. Developmental competence of both types of follicular oocytes did not differ significantly in terms of maturation and cleavage rate, but morula and blastocyst production rate were (P < 0.05) higher with in vivo developed AFs as compared with the in vitro cultured antral follicular oocytes. In conclusion, co-culture of PFs with AFs supports long-term survival and growth of buffalo PFs and this co-culture system plays a dual role for in vitro production of embryos as well as understanding the relationship between developing PFs and AFs.