Toxicity effect of Auxemma oncocalyx fraction and its active principle oncocalyxone A on in vitro culture of caprine secondary follicles and in vitro oocyte maturation

Abstract

Crude extract of the heartwood of Auxemma oncocalyx (A. oncocalyx) and its main component i.e., Oncocalyxone A (onco A), have elevated antioxidant and anti-tumoral activity, but studies on the action of these drugs regarding folliculogenesis are lacking. The aim of this study was to evaluate the effect of A. oncocalyx and onco A on the in vitro culture of isolated secondary follicles and on the in vitro maturation of oocytes from caprine antral follicles grown in vivo. Isolated secondary follicles were randomly distributed in six groups; the non-cultured control was immediately fixed upon isolation. The remaining follicles were cultured for 7 days in ?-MEM+ alone (control) or supplemented with DMSO, doxorrubicin, A. oncocalyx or onco A. After culture, follicles were evaluated for antrum formation, growth rate, apoptosis (TUNEL) and cellular proliferation (PCNA), as well as gene expression of Bcl2 and Bax. Additionally, cumulus oocyte complexes (COCs) were aspirated and allocated into five treatments for in vitro maturation: control, cultured only in maturation base medium (TCM 199+); or supplemented with DMSO; DXR; A. oncocalyx or onco A. After in vitro maturation, oocyte chromatin configuration and viability were assessed. After 7 days of culture, there was a reduction (P < 0.05) in the percentage of morphologically intact follicles, antrum formation, growth rate and number of PCNA positive granulosa cells in DXR treatment compared to the other treatments. In the DXR treatment a higher percentage (P < 0.05) of TUNEL positive follicles and higher (P < 0.05) relative BAX:BCL2 mRNA ratio’s were observed. After in vitro maturation of the COCs DXR, A. oncocalyx and onco A treatments had a greater (P < 0.05) percentage of abnormal oocytes and a lower (P < 0.05) percentage of viable oocytes as compared with the control group. However, only DXR and onco A treatments increased (P < 0.05) the percentage of alive oocytes with abnormal chromatin configuration. There were no differences in maturation rates between the control group and DXR, A. oncocalyx and onco A treatments. In conclusion, under our culture conditions, A. oncocalyx and onco A do not exhibit a toxic effect on isolated secondary follicles and on maturation rates of COCs recovered from antral follicles, however, these drugs negatively affected the COCs viability.  Thus, the use of culture biotechnologies as an in vitro secondary follicle culture and in vitro oocyte maturation toxicity testing are appropriated methods to evaluate the possible effects of drugs in folliculogesis.