In situ expression and localisation of MMP-2, MMP-9, TIMP-2, and TIMP-3 in different stages of follicle development
The protein expression patterns and localisation in each stage of follicle development are shown in Fig. 4. MMP-2 was mostly detected in the granulosa cells of normal pigs and was highly expressed in the theca externa of the developing follicles. During follicle development, higher levels of MMP-2 were observed in miniature pigs than in normal pigs. During this period, MMP-2 expression was low in theca externa cells, but high in theca interna and granulosa cells. In the Graafian follicles, MMP-2 expression was higher in miniature pigs than in normal pigs, both in theca interna and granulosa cells. MMP-2 was also highly expressed in theca lutein and granulosa lutein cells of the ovulated follicles (Fig. 4a).