Differential expression of pluripotent and germ cell markers in ovarian surface epithelium according to age in female mice.

Bo Sun Joo,Kyu-Sup Lee,Ki Hyung Kim,Min Jung Park,In Kook Jung,Jong Kil Joo

doi:10.1186/1477-7827-12-113

Bo Sun Joo, Kyu-Sup Lee + Show 4 more

Open Access

https://doi.org/10.1186/1477-7827-12-113

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Abstract

BackgroundMany studies have proposed that putative ovarian stem cells (OSCs) derived from the ovarian surface epithelium (OSE) layer of adult mammalian ovaries can produce oocytes. Few studies have reported that ovaries of aged mammalian females including mice and women possess rare premeiotic germ cells that can generate oocytes. However, no studies have reported the changes of OSCs according to the age of the female. Therefore, this study evaluated pluripotent and germ cell marker expression in the intact ovary, scraped OSE, and postcultured OSE according to age in female mice.MethodsC57BL/6 female mice of 2 age groups (6–8 and 28–31 weeks) were superovulated by injection with 5 IU equine chorionic gonadotropin (eCG). Both ovaries were removed after 48 hours and scrapped to obtain OSE. Gene expressions of pluripotent (Oct-4, Sox-2, Nanog) and germ cell markers (c-Kit, GDF-9, and VASA) were evaluated by RT-PCR. VASA and GDF-9 were immune-localized in oocyte-like structures.ResultsExpressions of germ cell markers in the intact ovary were significantly decreased in aged females, whereas expressions of pluripotent markers were not detected, regardless of age. Scraped OSE expression of all pluripotent and germ cell markers, except for c-Kit, was similar between both age groups. Three weeks postcultured OSE had significantly decreased expression of GDF-9 and VASA , but not c-Kit, in old mice, as compared to young mice; however there was no difference in the expression of other genes. The number of positively stained Oct-4 by immunohistochemistry in postcultured OSE was 2.5 times higher in young mice than aged mice. Oocyte-like structure was spontaneously produced in postcultured OSE. However, while that of young mice revealed a prominent nucleus, zona pellucida-like structure and cytoplasmic organelles, these features were not observed in old mice.ConclusionsThese results show that aged female mice have putative OSCs in OSE, but their differentiation potential, as well as the number of OSCs differs from those of young mice.

Highlights

Many studies have proposed that putative ovarian stem cells (OSCs) derived from the ovarian surface epithelium (OSE) layer of adult mammalian ovaries can produce oocytes
The expressions of pluripotent and germ cell markers in the intact ovary, scraped OSE, and postcultured OSE were examined by reversetranscription polymerase chain reaction (RT-polymerase chain reaction (PCR)) analyses
All pluripotent and germ cell markers were detected in the scraped OSE, with no significant difference between the two age groups except for c-Kit

Summary

Introduction

Many studies have proposed that putative ovarian stem cells (OSCs) derived from the ovarian surface epithelium (OSE) layer of adult mammalian ovaries can produce oocytes. Since Tilly’s group first reported the existence of proliferative germline stem cells that sustain oocyte and follicle production in the postnatal mouse ovary [5], many studies have subsequently demonstrated that putative ovarian stem cells (OSCs) can be successfully isolated from the ovarian surface epithelium (OSE) of the neonatal and adult mammalian ovary, including mice and human [6,7,8] This concept has challenged the traditional central dogma of mammalian reproductive biology that female are born with a finite and non-renewable pool of oocyte-containing follicles [9]. These findings suggested that postnatal oocyte renewal using OSE-derived OSCs will be helpful to better management and understanding of menopause, reproductive disease, and infertility associated with old age, poor response, or premenopause ovarian failure (POF)

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