Morphological features and effects on reproductive parameters of ovarian cysts of follicular origin in superovulated rabbit does

The objective of this study was to characterize ovarian cysts produced by a superovulatory treatment in rabbit does and to analyse their effects on re productive parameters. Sixty-one nulliparous rabbit does were superovulated with 75 IU PMSG and 50 IU hCG. Embryos and ovaries were obtained at 24, 44 , 64 and 84 h post-coitum (h pc). Number, type and diameter of ovarian cyst s were registered, as well as number of large antral follicles, ovulations, recovered and transferable embryos. An ovarian cyst was considered to be a n unruptured follicular structure larger than 1.1 mm. Features of ovarian c ysts and large antral follicles were examined by light microscopy. Vascular casts of the surface of ovarian cysts and large antral follicles were also examined by scanning electron microscopy. Three types of ovarian cysts wer e registered: follicular, luteal and mixed cysts. Follicular cysts showed c lear follicular fluid, a lower number of rows of granulosa cells than large antral follicles and dilated capillaries in the theca interna just below t he basement membrane. Luteal cysts showed a follicular wall increased in th ickness as compared with follicular cysts, hypertrophy and luteinization of follicular cells, breakdown of the basement membrane and presence of numer ous red blood cells in the follicular antrum. No morphological differences were observed between luteal cells of luteal cysts and normal corpora lutea . Mixed cysts presented histological features of both follicular and luteal types. Features of the follicular and luteal types were observed in the ap ical and basal zones of the mixed cysts, respectively. The luteinized zone of the mixed cysts showed a crescent form. Large antral follicles were usua lly in atresia, showed a well-defined basement membrane and no increase in size of capillaries of the theca interna as compared with ovarian cysts. Mi crovascular features of the apical area of the follicular wall of ovarian c ysts and large antral follicles showed structural differences. Large antral follicles showed dilatation of some vessels and areas with lack of capilla ries in the follicular apex. In contrast, ovarian cysts of all types presen ted an extensive plexus of vessels on their apical areas. At least one ovarian cyst was registered in 51 does (83.6%). The mean numbe r of ovarian cysts per ovary was 4.5 +/- 6.6 (mean +/- standard deviation). This mean number was higher at 44 h pc than at 26 h pc (p < 0.01). Follicu lar cysts were predominant at 26 h pc, whereas luteal cysts predominated at 44, 64 and 84 h pc(chi(2) = 40.45, df = 6, p = 0.0001). The mean diameter of cysts was higher at 44 h pc than at the other post-coital intervals (p < 0.05). The total number of ovarian cysts, follicular cysts and mixed cysts were negatively correlated to the number of ovulations, number of recovere d and transferable embryos, embryo recovery rate and proportion of transfer able embryos. In contrast, luteal cysts were not correlated to the reproduc tive parameters analysed. In summary, three types of ovarian cysts have been registered (follicular, luteal and mixed cysts) and structural differences have been observed in th e vascular pattern of the apical areas of ovarian cysts and antral follicle s. The results of this study suggest that ovarian cysts of follicular origi n are dynamic structures and affect embryo production in superovulated rabb it does. It is suggested that mixed cysts could be an intermediate stage be tween follicular and luteal types.