Canadian HealthCare News

In the rabbit, Kitl mRNA and protein were detected in the squamous granulosa cells of some primordial follicles. The cuboidal granulosa cells surrounding growing follicles uniformly expressed high levels of KITL until the antral stage of development, when the presence of KITL became sporadic. Both mRNA and protein for KIT were detected within all oocytes, at every stage of development. In general, the amount of KIT protein localized to the oolemma increased with follicle growth and then decreased within the fully grown oocytes of antral follicles. (more…)

Primordial follicles are the stores of female gametes from which all mature eggs for ovulation and fertilization arise. The recruitment of primordial follicles into the growth phase is tightly controlled and likely involves the action of both stimulatory and inhibitory molecules. Although the exact mechanisms that regulate primordial follicle activation and the initiation of oocyte growth remain elusive, the study of rodent models has shown KITL and KIT to be involved in these processes. (more…)

In cultured untreated ovaries, oocytes from primordial follicles were considerably larger (P < 0.05) than those of primordial follicles in preculture tissues, whereas the mean diameters of oocytes from follicles at all other stages of development were unaffected by culture (Table 2). The spontaneous enlargement of oocytes from primordial follicles was not antagonized by KITL-neutralizing antibody (Table 2), suggesting that some unknown aspect of culture other than endogenous KITL induced the observed growth. (more…)

The proportions of follicles in the early primary stage of development in untreated and recombinant mouse KITL-treated (50 ng/ml and 150 ng/ml) ovaries were not significantly different from each other. Despite a trend toward increased number, there was no significant difference in the proportions of primary and preantral follicles with 50 ng/ml recombinant mouse KITL. However, treatment with 150 ng/ml recombinant mouse KITL significantly (P < 0.05) increased the proportions of primary and preantral follicles (15.7% 6 1.8% and 8.6% 6 1.4%, respectively), compared with untreated cultured ovaries (5.0% 6 0.9% and 2.3% 6 0.5%, respectively) (Fig. 8). (more…)

The addition of neutralizing antibody to the culture media partially inhibited the spontaneous activation of primordial follicles. This was manifested by a significant (P < 0.05) increase in the proportion of primordial follicles in neutralizing antibody-treated ovaries (47.2% 6 3.6%) compared with untreated ovaries (33.0% 6 3.2%) (Fig. 8). This increase in the proportion of primordial follicles was reflected by a decline in the proportions of early primary, primary, and preantral follicles in the antibody-treated group compared with the untreated culture control group, although the differences between these two treatment groups within individual follicle stages were not statistically significant. (more…)

Therefore, recombinant mouse KITL did not enhance the survival of follicles in neonatal mouse ovaries maintained in vitro, nor did KITL-neutralizing antibody promote follicular atresia. (more…)

Recombinant mouse KITL (50 ng/ml and 150 ng/ml) had no stimulatory effect on the diameter of oocytes in the preantral follicle population compared with untreated cultured explants (Table 1). (more…)

Comparisons of oocyte sizes between untreated and recombinant mouse KITL-treated cultured explants were made in order to assess the effect of exogenous recombinant mouse KITL on oocyte growth in vitro. Recombinant mouse KITL was shown to have a major effect on the size of oocytes at the earliest stages of development (Table 1). The mean diameter of primordial follicle oocytes increased significantly (P < 0.05), from 31.7 6 0.2 im in untreated cultured explants, to 34.6 6 0.3 im in explants treated with 50 ng/ml recombinant mouse KITL, to a final diameter of 36.3 6 0.1 im in 150 ng/ml recombinant mouse KITL-treated explants (Table 1). (more…)

In order to determine whether endogenous KITL had a role in promoting the growth of oocytes from primordial and early primary follicles that was observed during in vitro culture, neutralizing antibody to recombinant mouse KITL was added to the culture media. It was anticipated that if endogenous KITL were inducing growth in follicles maintained in vitro, then neutralization of the ligand would result in primordial and early primary follicle diameters comparable to those in preculture tissues. (more…)

However, there was an increase in the proportions of primary and preantral follicles compared with untreated and recombinant mouse KITL-supplemented explants, although this difference was not statistically significant in all pairwise comparisons (Fig. 6). These data suggest that the inhibitory antibody possibly enhances receptor signaling. (more…)