Fig. 1. Model depicting follicular growth and cumulus expansion. Preantral follicles under the stimulation of gonadotropins and oocyte factors develop into antral follicles. The formation of the antrum separates the granulosa cells into mural and cumulus cells. Mural cells (green) express Lhcgr, Cyp11a1 and Cd34 transcripts more highly than cumulus cells (red), whereas Slc38a3, Amh and Ar transcripts are highly expressed in cumulus cells. At ovulation, the LH surge induces cumulus expansion with associated increases in expansion-related transcripts (Has2, Ptgs2, Ptx3 and Tnfaip6). Real-time PCR analysis of mural and cumulus marker transcripts in freshly isolated COCs and mural cells is also shown. Transcripts were normalized to Rpl19 mRNA. ^*Indicates significant difference by Student's t-test P<0.05.