The immunoexpression patterns of fibroblast growth factors in the pregnant and postpartum rat ovary

FGF2 promotes the proliferation of injured granulosa cells in premature ovarian failure via Hippo-YAP signaling pathway

Young women undergoing anticancer treatment are at risk of premature ovarian failure (POF). Endometrial-derived stem cells (EnSCs) have demonstrated significant therapeutic potential for treating ovarian insufficiency, although the underlying mechanisms remain to be fully understood. This study aims to further investigate the therapeutic effects of EnSCs, particularly through the paracrine action of fibroblast growth factor 2 (FGF2), on POF. The findings show that exogenous FGF2 enhances the survival of ovarian granulosa cells damaged by cisplatin. FGF2 stimulates the proliferation of these damaged cells by suppressing the Hippo signaling pathway and activating YAP expression. In vivo experiments also revealed that FGF2 treatment significantly improves ovarian reserve and endocrine function in mice with POF. These results suggest that FGF2 can boost the proliferative capacity of damaged ovarian granulosa cells through the Hippo-YAP signaling pathway, providing a theoretical foundation for using EnSCs and FGF2 in clinical treatments for POF.

Growth factors and female reproduction in vertebrates

Female reproductive efficiency is influenced by the outcomes of various processes, including folliculogenesis, apoptosis, response to gonadotropin signaling, oocyte maturation, and ovulation. The role of hormones in regulating these processes and other reproductive activities has been well established. It is becoming increasingly evident that in addition to well-characterized hormones, growth factors play vital roles in regulating some of these reproductive activities. Growth factors and their receptors are widely distributed in vertebrate ovaries at different stages of ovarian development, indicating their involvement in intraovarian reproductive functions. In the ovary, cell surface receptors allow growth factors to regulate intraovarian reproductive activities. Understanding these actions in the reproductive axis would provide a tool to target growth factors and/or their receptors to yield desirable reproductive outcomes. These include enrichment of in vitro maturation and fertilization culture media, and management of infertility. This review discusses some widely characterized growth factors belonging to the TGF, EGF, IGF, FGF, and BDNF family of peptides and their role in female reproduction in vertebrates, with a focus on mammals.

Mechanisms of angioregression of the corpus luteum

The corpus luteum is a transient ovarian endocrine gland that produces the progesterone necessary for the establishment and maintenance of pregnancy. The formation and function of this gland involves angiogenesis, establishing the tissue with a robust blood flow and vast microvasculature required to support production of progesterone. Every steroidogenic cell within the corpus luteum is in direct contact with a capillary, and disruption of angiogenesis impairs luteal development and function. At the end of a reproductive cycle, the corpus luteum ceases progesterone production and undergoes rapid structural regression into a nonfunctional corpus albicans in a process initiated and exacerbated by the luteolysin prostaglandin F2α (PGF2α). Structural regression is accompanied by complete regression of the luteal microvasculature in which endothelial cells die and are sloughed off into capillaries and lymphatic vessels. During luteal regression, changes in nitric oxide transiently increase blood flow, followed by a reduction in blood flow and progesterone secretion. Early luteal regression is marked by an increased production of cytokines and chemokines and influx of immune cells. Microvascular endothelial cells are sensitive to released factors during luteolysis, including thrombospondin, endothelin, and cytokines like tumor necrosis factor alpha (TNF) and transforming growth factor β 1 (TGFB1). Although PGF2α is known to be a vasoconstrictor, endothelial cells do not express receptors for PGF2α, therefore it is believed that the angioregression occurring during luteolysis is mediated by factors downstream of PGF2α signaling. Yet, the exact mechanisms responsible for angioregression in the corpus luteum remain unknown. This review describes the current knowledge on angioregression of the corpus luteum and the roles of vasoactive factors released during luteolysis on luteal vasculature and endothelial cells of the microvasculature.

Basic fibroblast growth factor induces proliferation and collagen production by fibroblasts derived from the bovine corpus luteum†

Cyclic regression of the ovarian corpus luteum, the endocrine gland responsible for progesterone production, involves rapid matrix remodeling. Despite fibroblasts in other systems being known for producing and maintaining extracellular matrix, little is known about fibroblasts in the functional or regressing corpus luteum. Vast transcriptomic changes occur in the regressing corpus luteum, among which are reduced levels of vascular endothelial growth factor A (VEGFA) and increased expression of fibroblast growth factor 2 (FGF2) after 4 and 12 h of induced regression, when progesterone is declining and the microvasculature is destabilizing. We hypothesized that FGF2 activates luteal fibroblasts. Analysis of transcriptomic changes during induced luteal regression revealed elevations in markers of fibroblast activation and fibrosis, including fibroblast activation protein (FAP), serpin family E member 1 (SERPINE1), and secreted phosphoprotein 1 (SPP1). To test our hypothesis, we treated bovine luteal fibroblasts with FGF2 to measure downstream signaling, type 1 collagen production, and proliferation. We observed rapid and robust phosphorylation of various signaling pathways involved in proliferation, such as ERK, AKT, and STAT1. From our longer-term treatments, we determined that FGF2 has a concentration-dependent collagen-inducing effect, and that FGF2 acts as a mitogen for luteal fibroblasts. FGF2-induced proliferation was greatly blunted by inhibition of AKT or STAT1 signaling. Our results suggest that luteal fibroblasts are responsive to factors that are released by the regressing bovine corpus luteum, an insight into the contribution of fibroblasts to the microenvironment in the regressing corpus luteum.

LPS- and LTA-Induced Expression of TLR4, MyD88, and TNF-α in Lymph Nodes of the Akkaraman and Romanov Lambs

Toll-like receptor (TLR)-mediated inflammatory processes play a critical role in the innate immune response during the initial interaction between the infecting microorganism and immune cells. This study aimed to investigate the possible microanatomical and histological differences in mandibular and bronchial lymph nodes in Akkaraman and Romanov lambs induced by lipopolysaccharide (LPS) and lipoteichoic acid (LTA) and study the gene, protein, and immunoexpression levels of TLR4, myeloid differentiation factor 88 (MyD88), and tumor necrosis factor-α (TNF-α) that are involved in the immune system. Microanatomical examinations demonstrated more intense lymphocyte infiltration in the bronchial lymph nodes of Akkaraman lambs in the LPS and LTA groups compared to Romanov lambs. TLR4, MyD88, and TNF-α immunoreactivities were more intense in the experimental groups of both breeds. Expression levels of MyD88 and TNF-α genes in the bronchial lymph node of Akkaraman lambs were found to increase statistically significantly in the LTA group. TLR4 gene expression level in the mandibular lymph node was found to be statistically significantly higher in the LTA + LPS group. In conclusion, dynamic changes in the immune cell populations involved in response to antigens such as LTA and LPS in the lymph nodes of both breeds can be associated with the difference in the expression level of the TLR4/MyD88/TNF-α genes.