Frozen section with improved H&E staining for follicular morphometric analysis of mouse ovary in oestrus cycle

Careful analysis of follicular morphology and numbers of different follicular maturation stages, in combination with the measurements of gonadotropic and sex hormone profiles, provide an accurate and rapid evaluation system of the ovarian function. The aim of this study is to improve the existing methods of ovarian tissue section preparation and staining methods, and to establish a fast and easy method to observe and evaluate follicular maturation stage and numbers using mouse ovary samples. Ovaries were collected at menstrual phases of proestrus, oestrus, metestrus and diestrus from C57BL/6J female mice. Then the ovaries were fixed in 4% paraformaldehyde, dehydrated with graded sucrose, embedded with OCT, frozen-sectioned at 7 μm thick, and subjected to quick haematoxylin & eosin staining for observation. The results showed that the present method was able to distinguish secondary, preantral, antral, and preovulatory follicles. Although our method was unable to discriminate and distinguish primordial follicles and primary follicles, the results were comparable to those from more complicated techniques. We conclude that this improved and quick method can be used in combination with hormone analysis to investigate ovarian development and function in different mouse models.