Expression And Regulation Of SPARC In Mouse Ovary During Follicular Development And Corpus Luteum Formation

SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matrix-associated glycoprotein that involves in a variety of cellular activities. SPARC and its related peptides bind to several proteins of the extracellular matrix (ECM), affect ECM protein expression, alter cell shape, reduce cellular adhesion, influence migration, and modulate growth factor-induced cell proliferation and angiogenesis. SPARC is also important for tumorigenesis, tissue injury and embryonic development. In this study, we used in situ hybridization to examine the temporal and spatial expression patterns of SPARC in mouse ovary during follicular development and corpus luteum formation. Furthermore, we examined the regulation of SPARC expression in mouse ovary by several models, such as sexual maturation, follicular development induced by eCG, ovulation induced by hCG and corpus luteum formation and regression. We found that during sexual maturation, a low level of SPARC expression occurred in ovary matrix, and moderate in theca cells, but there was no signal in granulosa cells and oocytes. During follicular development induced by eCG, the expression of SPARC in ovary matrix and theca cells was up-regulated after 6 hours of eCG injection and achieve summit 48 hours later. We injected hCG 48 hours after eCG injection to simulate the effect of LH in vivo and a continuing high level was found in matrix and theca cells. 9 hours later, there was a low expression in granulosa cells and increased gradually. At the time of ovulation, a strong signal was detected. 24 hours post-hCG treatment, there was a high level of SPARC expression in newly formed corpus luteum, and this occurred until structural regression of corpus luteum when a basal level was observed in ovary matrix and moderate level in theca cells. Our data suggest that SPARC may play a role in follicular development and corpus luteum formation.