Cumulus Cells Accelerate Aging Of Mouse Oocytes By Secreting A Soluble Factor(s)

In most mammals, matured oocytes are arrested at metaphase-Ⅱ(MⅡ), and will not resume meiosis until activated by penetrating spermatozoa or other stimulations. If the MⅡoocytes are not fertilized or activated timely, some changes occurring in the ctoplasm will lead to decreased quality of the oocytes, this phenomenon is called oocyte-aging. Cumulus cells represent this unique subpopulation of granulose cells that surrounds the oocyte, providing nutrient, metabolic precursors and signals that regulate its development and maturation. Cumulus cells play an important role not only in maturation, ovulation and fertilization of oocytes but also in the aging of oocyte after ovulation. However, we know very little about how the cumulus cells promote the aging of oocyte. In this study, we use the way of co-culture DOs with COCs, conditioned media treatment and co-culture DOs with somatic cells monolays to make it clear how the cumulus cells excrete the factor to promote the aging of mouse oocytes;and we put the COCs or DOs into different thermometric conditions for several hours to make it clear that how different the cumulus cells exrect aging-promoting factor under different conditions; and we heated the conditioned media in different temperature or freezed the conditioned media in -70℃and thawing for three times before treating DOs to make it clear that the response of aging-promoting factor to different thermometric treatments. The results are summarized as follows:1. When we co-cultured in vivo or in vitro DOs with in vivo COCs (DO: COC=1:2),the activation rate of DOs co-cultured with COC was significantly higher than the control group. When we co-cultured in vivo or in vitro DOs with in vitro COCs (DO: COC=1:5), the activation rate of DOs co-cultured with COCs was significantly higher than the control group too.These indicated that in vitro COCs is different from in vivo COCs on the ability of excreting aging-promoting factor (APF).2. The activation rate of COCs and DOs treated with the conditoned media from 30 in vivo COCs aging for 6 hours in 200μl CZB was significantly...