# Fibr Facilitates Mesenchymal Stem Cells to Ameliorate Rats with Polycystic Ovary Syndrome
###### Abstract  
Polycystic ovarian syndrome (PCOS) is a ubiquitous hormonal disorder and induces female infertility and heterogeneous syndromes, for which there is still no effective treatment. Thanks to the properties of immunomodulatory and endocrine regulation, mesenchymal stem cells (MSCs) have been widely used in various disease types. There were few reports for MSCs injected to ovaries due to the size limitation and complicated vascular network. Here, we develop one simple and efficient approach to deliver and stabilize MSCs in the outside of the ovary without blood leaking through the fibrin gelation, which also possesses excellent biocompatibility to support MSC survival. Notably, the transplantation of MSCs, encapsulated in fibrin hydrogel, could rescue ovarian function more efficiently compared to only MSC control in terms of elevated estradiol (E2) and progesterone (P) levels, diminished gonadotropins (LH/FSH), testosterone (T), and transforming growth factor-\(\beta\)1 (TGF-\(\beta\)1) levels, regular estrous cycles, enhanced number of granulosa cells, and reduced number of immature cystic follicles. The size and weight of the ovary increased for MSCs both within and without fibrin in PCOS rat models in two weeks. Moreover, we have shown the versatility of fibrin hydrogel as a cell-compatible platform for advanced stem cell translation, including identifying novel mechanisms of cell survival support, tissue development, and regenerative medicine.  
PCOS; MSCs; fibrin; ovarian structure; TGF-\(\beta\)1 +
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effective and beneficial to improve ovulation as a supplementation of clomiphene citrate [9; 10]; it was reported there was no sufficient evidence to demonstrate the availability for the administration of myo-inositol in PCOS patients experiencing ovulation induction [11]. Moreover, hydrolaparoscopic ovarian drilling is a unique treatment for anovulatory women with PCOS, but this surgery causes tissue adhesion and other complications [12]. Therefore, due to such limitations, there is a need to identify an ideal treatment for PCOS.  
Human mesenchymal stem cells (hMSCs) have become a research focus of clinical therapeutics owing to their properties of stemness, anti-inflammatory activity, the secretion of active factors, and differentiation into various types of somatic cells. MSCs can secrete numerous active factors such as vascular endothelial growth factor (VEGF), IL-10, and TNF-\(\alpha\)[13; 14; 15] that are anti-inflammatory, angiogenic, and antifibrotic [16; 17; 15], which therefore can be helpful to impaired lungs, liver, kidney, endometrium, and ovary [18; 19]. Moreover, MSCs can secrete estrogen, which, in consequence, may be potentially used as an effective treatment for patients with estrogen deficiency [20]. A previous study has demonstrated that MSCs administered to mice via tail vein injection had inhibited inflammation in PCOS [21].  
Furthermore, MSCs improve the fertility of women with premature ovarian failure through intrarovarian injection, which can minimize MSC diffusion to other tissues [22; 23]. In particular, umbilical cord MSCs (UC-MSCs) entrapped in fibrin gels have been used in in vitro/in vivo construction of bone [24; 25], cartilage [26], and the microvascular network [27]. Fibrin has been widely used as a desirable scaffold and carrier for MSCs, which can help MSCs reach the specific organ or tissue and subsequently decrease/stop bleeding after cell transplantation [28; 29]. It has been used to construct artificial ovaries to preserve the fertility of a patient. In adults, fibrin clots can recruit hMSCs; however, the strong fibrinolytic activity of hMSCs plays a similar role as fibrin in matrix remodeling and wound healing [30]. This study aims to investigate whether intrarovarian injection of UC-MSCs alone or within fibrin hydrogels can restore ovarian function in a PCOS rat model, to elucidate its underlying mechanism. This study also identifies therapeutic targets for assisted reproduction technology.