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Acta sci. vet. (Impr.); 41: Pub. 1150, 2013. ilus, tab

Artigo em Inglês | VETINDEX | ID: biblio-1371962

Resumo

Background: The main advantage of the cryopreservation of ovarian fragments is a thinner tissue, which facilitates the penetration of cryoprotective agents, but the size of tissue may not be a limiting factor in achieving a successful cryopreservation of the ovarian tissue. This information is highly significant considering that the cryopreservation of hemi-ovary or whole ovary may preserve the entire or major part of the contingent of primordial follicles of ovarian fragments. Therefore, the aim of this study was to evaluate the vitrification of different dimensions goat ovarian tissue on the follicular morphology, viability, diameter, and the stromal cell density. Materials, Methods & Results: The ovarian tissue was vitrified as fragment, hemi-ovary, or whole ovary, and after warming, the preantral follicles were examined by trypan blue dye exclusion test and histological analysis. Preantral follicles incubated with trypan blue were considered viable if the oocyte and granulosa cells remained unstained. Preantral follicles were classified as morphologically normal only when they contained intact oocyte and granulosa cells. The follicular diameter was measured considering the major and minor axes of each follicle; the average of these 2 measurements was used to determine the diameter of each follicle. Ovarian stroma cells density was evaluated by calculating the number of stromal cell in an area of 100 × 100 µm. There was no difference in the percentage of morphologically normal and viable follicles after vitrification compared to the control (fresh tissue), regardless of the dimension of the vitrified ovarian tissue (P > 0.05). In addition, there were no differences in the follicular diameter after ovarian tissue vitrification, independent of the dimension (P > 0.05). However, after vitrifi cation, a decrease in the ovarian stromal cells density was observed (P < 0.05). This reduction was more intense after the vitrification of the hemi-ovary and whole ovary, compared to the ovarian fragment vitrification (P < 0.05). Discussion: No differences were observed in the percentages of morphologically normal and viable follicles from fresh or vitrified ovarian tissue (fragment, hemi-ovary, and whole ovary). These results are in agreement with other reports which no showed morphological changes after cryopreservation of the whole ovary, and the ovarian fragments. With respect to follicular diameter, only the diameter of the preantral follicles in ovarian tissue vitrified as hemi-ovary was similar to that observed in the fresh control, in the present study. The results demonstrate that fragments and whole ovary vitrification had greater cell dehydration (exposure to VS) and/or less cell rehydration (VS removal), showing that minor adjustments are needed in the protocols of cryoprotectants addition or removal from the fragments and the whole ovary. However, this reduction in follicular diameter did not appear to have affected the follicular architecture or cellular viability, which were maintained in all dimensions of ovarian tissue undergoing vitrifi cation. A reduction in the stromal cell density was observed, especially in the hemi-ovary and whole ovary as compared to the ovarian fragment. Previous reports have shown that ovarian stromal cells are responsible for the production of essential substances for follicular development and these substances are fundamental for follicles development and these cells tend to be more sensitive to cryopreservation procedure than ovarian follicles. In conclusion, the maintenance of follicular morphology and viability demonstrated that vitrification of goat ovarian tissue under the conditions applied in this study can be performed in any dimension of ovarian tissue (fragment, hemi-ovary, and whole ovary).

Biblioteca responsável: BR68.1