Mesenchymal stem cells promote ovarian reconstruction in mice

Abstract

Background Studies have shown that chemotherapy and radiotherapy can cause premature ovarian failure and loss of fertility in female cancer patients. Ovarian cortex cryopreservation is a good choice to preserve female fertility before cancer treatment. Following the remission of the disease, the thawed ovarian tissue can be transplanted back and restore fertility of the patient. However, there is a risk to reintroduce cancer cells in the body and leads to the recurrence of cancer. Given the low success rate of current in vitro culture techniques for obtaining mature oocytes from primordial follicles, an artificial ovary with primordial follicles may be a good way to solve this problem. Methods In the study, we established an artificial ovary model based on the participation of mesenchymal stem cells (MSCs) to evaluate the effect of MSCs on follicular development and oocyte maturation. P2.5 mouse ovaries were digested into single cell suspensions and mixed with bone marrow derived mesenchymal stem cells (BM-MSCs) at a 1:1 ratio. The reconstituted ovarian model was then generated by using phytohemagglutinin. The phenotype and mechanism studies were explored by follicle counting, immunohistochemistry, immunofluorescence, in vitro maturation (IVM), in vitro fertilization (IVF), real-time quantitative polymerase chain reaction (RT-PCR), and Terminal-deoxynucleotidyl transferase mediated nick end labeling(TUNEL) assay. Results Our study found that the addition of BM-MSCs to the reconstituted ovary can enhance the survival of oocytes and promote the growth and development of follicles. After transplanting the reconstituted ovaries under kidney capsules of the recipient mice, we observed normal folliculogenesis and oocyte maturation. Interestingly, we found that BM-MSCs did not contribute to the formation of follicles in ovarian aggregation, nor did they undergo proliferation during follicle growth. Instead, the cells were found to be located around growing follicles in the reconstituted ovary. When theca cells were labeled with CYP17a1, we found some overlapped staining with green fluorescent protein(GFP)-labeled BM-MSCs. The results suggest that BM-MSCs may participate in directing the differentiation of theca layer in the reconstituted ovary. Conclusions The presence of BM-MSCs in the artificial ovary was found to promote the survival of ovarian cells, as well as facilitate follicle formation and development. Since the cells didn’t proliferate in the reconstituted ovary, this

1. Introduction

With rapid advancements in cancer therapy, children and reproductive-age women are benefitting from overall improved survival rates [1]. It is well-documented that treatment of girls and women for cancer with radiation, chemotherapeutic drugs, or a combination of the two therapies can result in significant, and often irreversible, side-effect damage to the reproductive system [2, 3]. Anti-cancer therapy is often a cause of premature ovarian insufficiency (POI) due to the high sensitivity of the ovarian follicle reserve to chemotherapy and radiotherapy [4, 5]. Thus, there is an increased number of patients who received a gonadotoxic treatment and who later face fertility issues [6]. Overall, compared to the general population, women who undergo cancer treatment are 38% less likely to become pregnant. This reduction in the likelihood of subsequent pregnancies has been observed in nearly all types of cancer [7]. Consequently, the preservation of the ovarian reserve and prevention of infertility have become the primary quality of life concerns for patients and their physicians.

Fertility preservation refers to the use of surgical, pharmacologic, or laboratory techniques to provide assistance to women or men at risk of infertility in protecting and preserving their ability to have genetically derived offspring [8]. For women, common fertility preservation methods currently used include egg, embryo, and ovarian tissue freezing, whereas for unmarried or prepubertal women, freezing of the ovarian cortex is more appropriate [9–11]. After the patient’s condition has improved or resolved, the preserved ovarian cortex can be thawed and transplanted back to the p