Objective: To assess the expression and cellular distribution of pregnancy-associated plasma protein-A (PAPP-A) and major basic protein (MBP) in human ovarian tissue during the menstrual cycle.
Design: Ovarian tissues (n = 50) and corpora lutea (n = 18) were obtained from patients undergoing hysterectomy/oophorectomy for benign conditions and tissue sections were immunostained for MBP and PAPP-A.
Setting: University medical center.
Intervention(s): Immunostaining of tissue sections using antibodies to PAPP-A and MBP.
Main outcome measure(s): Microscopic evaluation to assess the presence, distribution, and cellular co-localization of MBP and PAPP-A and to describe any variations in their expression during the menstrual cycle.
Result(s): Major basic protein (MBP) is found in several ovarian cell types throughout the menstrual cycle. The MBP immunostaining of ovarian follicles varied depending on the size, with primordial follicles staining in the ooplasm with a lack of staining in the granulosa and theca cells. In the intermediate/mature follicles, MBP was immunolocalized in theca, but not in granulosa cells except in the mature follicles. Pregnancy-associated plasma protein-A (PAPP-A) was immunolocalized in primordial follicle ooplasm, theca externa of intermediate/mature follicles, and in granulosa cells with increased intensity as luteinization progressed. The luteal tissue is the major site of MBP and PAPP-A with highest intensity found during the midluteal phase associated with both small and large luteal cells.
Conclusion(s): The expression and distinct pattern of MBP and PAPP-A cellular localization in human ovarian tissue during folliculogenesis and in luteal tissue suggest that their individual and combined actions in a cell specific fashion may play a role in growth and differentiation of theca, granulosa, and luteal cells.