Primary Cilia Restrain PI3K-AKT Signaling to Orchestrate Human Decidualization

Modulation of PI3K/AKT/mTOR signaling pathway in the ovine liver and duodenum during early pregnancy

The liver and intestine play a critical role in nutrient absorption, storage, and metabolism. The aim of this study was to evaluate expression pattern of phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of the rapamycin (mTOR) signaling pathway that included PI3K, AKT1, mTOR, FoxO1, SREBP-1, PPARα, PTEN and FXR in the maternal liver and duodenum. Ovine livers and duodenums were sampled at day 16 of the estrous cycle, and at days 13, 16 and 25 of gestation, and RT-qPCR, western blot and immunohistochemistry analysis were used to detect mRNA and protein expression. The results showed that expression of PI3K, AKT1, p-mTOR, FoxO1, SREBP-1 and PTEN upregulated in the maternal liver, and PPARα upregulated in the duodenum. However, expression of FoxO1, SREBP-1 and PTEN in the duodenum downregulated during early pregnancy. In addition, expression levels of SREBP-1, PTEN and PPARα in the maternal liver, and PI3K in the duodenum peaked at day 13 of pregnancy. In addition, expression levels of PI3K, p-mTOR and FoxO1 in the liver, and AKT1 and p-mTOR in the duodenum peaked at day 16 of pregnancy. Nevertheless, expression levels of FXR both in the maternal liver duodenum downregulated at days 13 and 16 of pregnancy. In conclusion, early pregnancy regulated expression pattern of PI3K/AKT/mTOR signaling pathway in the ovine liver and duodenum in a pregnancy stage-specific and tissue-specific manner, which may be necessary for the adaptations in maternal hepatic nutrient metabolism and intestinal nutrient absorption early pregnancy.

Structure, function, and research progress of primary cilia in reproductive physiology and reproductive diseases

Primary cilia, serving as the central hub for cellular signal transduction, possess the remarkable ability to translate diverse extracellular signals, both chemical and mechanical, into intracellular responses. Their ubiquitous presence in the reproductive system underscores their pivotal roles in various cellular processes including development, differentiation, and migration. Emerging evidence suggests primary cilia as key players in reproductive physiology and associated pathologies. Notably, primary cilia have been identified in granulosa cells within mouse ovaries and uterine stromal cells, and perturbations in their structure and function have been implicated in a spectrum of reproductive dysfunctions and ciliary-related diseases. Furthermore, disruptions in primary cilia-mediated signal transduction pathways under pathological conditions exacerbate the onset and progression of reproductive disorders. This review provides a comprehensive overview of current research progress on primary cilia and their associated signaling pathways in reproductive physiology and diseases, with the aim of furnishing theoretical groundwork for the prevention and management of primary cilia-related structural and functional abnormalities contributing to reproductive system pathologies.

Primary cilia abnormalities participate in the occurrence of spontaneous abortion through TGF-β/SMAD2/3 signaling pathway

Spontaneous abortion is the most common complication in early pregnancy, the exact etiology of most cases cannot be determined. Emerging studies suggest that mutations in ciliary genes may be associated with progression of pregnancy loss. However, the involvement of primary cilia on spontaneous abortion and the underlying molecular mechanisms remains poorly understood. We observed the number and length of primary cilia were significantly decreased in decidua of spontaneous abortion in human and lipopolysaccharide (LPS)-induced abortion mice model, accompanied with increased expression of proinflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. The length of primary cilia in human endometrial stromal cell (hESC) was significantly shortened after TNF-α treatment. Knocking down intraflagellar transport 88 (IFT88), involved in cilia formation and maintenance, promoted the expression of TNF-α. There was a reverse regulatory relationship between cilia shortening and TNF-α expression. Further research found that shortened cilia impair decidualization in hESC through transforming growth factor (TGF)-β/SMAD2/3 signaling. Primary cilia were impaired in decidua tissue of spontaneous abortion, which might be mainly caused by inflammatory injury. Primary cilia abnormalities resulted in dysregulation of TGF-β/SMAD2/3 signaling transduction and decidualization impairment, which led to spontaneous abortion.

Hormonal regulation of cilia in the female reproductive tract

This review intends to bridge the gap between our knowledge of steroid hormone regulation of motile cilia and the potential involvement of the primary cilium focusing on the female reproductive tract functions. The review emphasizes hormonal regulation of the motile and primary cilia in the oviduct and uterus. Steroid hormones including estrogen, progesterone, and testosterone act through their cognate receptors to regulate the development and biological function of the reproductive tracts. These hormones modulate motile ciliary beating and, in some cases, primary cilia function. Dysfunction of motile or primary cilia due to genetic anomalies, hormone imbalances, or loss of steroid hormone receptors impairs mammalian fertility. However, further research on hormone modulation of ciliary function, especially in the primary cilium, and its signaling cascades will provide insights into the pathogenesis of mammalian infertility and the development of contraceptives or infertility treatments targeting primary and/or motile cilia.

The miR-669a-5p/G3BP/HDAC6/AKAP12 Axis Regulates Primary Cilia Length

Primary cilia are conserved organelles in most mammalian cells, acting as "antennae" to sense external signals. Maintaining a physiological cilium length is required for cilium function. MicroRNAs (miRNAs) are potent gene expression regulators, and aberrant miRNA expression is closely associated with ciliopathies. However, how miRNAs modulate cilium length remains elusive. Here, using the calcium-shock method and small RNA sequencing, a miRNA is identified, namely, miR-669a-5p, that is highly expressed in the cilia-enriched noncellular fraction. It is shown that miR-669a-5p promotes cilium elongation but not cilium formation in cultured cells. Mechanistically, it is demonstrated that miR-669a-5p represses ras-GTPase-activating protein SH3-domain-binding protein (G3BP) expression to inhibit histone deacetylase 6 (HDAC6) expression, which further upregulates A-kinase anchor protein 12 (AKAP12) expression. This effect ultimately blocks cilia disassembly and leads to greater cilium length, which can be restored to wild-type lengths by either upregulating HDAC6 or downregulating AKAP12. Collectively, these results elucidate a previously unidentified miR-669a-5p/G3BP/HDAC6/AKAP12 signaling pathway that regulates cilium length, providing potential pharmaceutical targets for treating ciliopathies.

Identification of m6A Modification Regulated by Dysregulated circRNAs in Decidua of Recurrent Pregnancy Loss

N6-methyladenosine (m6A) modification is a prevalent modification of messenger ribonucleic acid (mRNA) in eukaryote cells and is closely associated with recurrent pregnancy loss (RPL). Circular RNAs (circRNAs) play critical roles in embryo implantation, trophoblast invasion and immune balance, which are important events during pregnancy. However, how m6A modification is regulated by circRNAs and the potential regulatory mechanism of circRNAs on RPL occurrence remain largely unclassified. We displayed the expression profiles of circRNAs and mRNAs in the decidua of normal pregnancies and RPL patients based on circRNA sequencing and the Gene Expression Omnibus database. A total of 936 differentially expressed circRNAs were identified, including 509 upregulated and 427 downregulated circRNAs. Differentially expressed circRNAs were enriched in immune, metabolism, signaling and other related pathways via the analysis of Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. The competitive endogenous RNA (ceRNA) network was predicted to supply the possible role of circRNAs in RPL occurrence, and we further analyzed the profiles of nine m6A regulators (seven readers, one writer and one eraser) managed by circRNAs in this network. We also showed the expression profiles of circRNAs in the serum, trying to seek a potential biomarker to help in the diagnosis of RPL. These data imply that circRNAs are involved in pathogenesis of RPL by changing immune activities, metabolism and m6A modification in the ceRNA network. Our study might provide assistance in exploring the pathogenesis and diagnosis of RPL.

Diabetes impairs fracture healing through Foxo1 mediated disruption of ciliogenesis

Foxo1 upregulation is linked to defective fracture healing under diabetic conditions. Previous studies demonstrated that diabetes upregulates Foxo1 expression and activation and diabetes impairs ciliogenesis resulting in defective fracture repair. However, the mechanism by which diabetes causes cilia loss during fracture healing remains elusive. We report here that streptozotocin (STZ)-induced type 1 diabetes mellitus (T1DM) dramatically increased Foxo1 expression in femoral fracture calluses, which thereby caused a significant decrease in the expression of IFT80 and primary cilia number. Ablation of Foxo1 in osteoblasts in OSXcretTAFoxo1f/f mice rescued IFT80 expression and ciliogenesis and restored bone formation and mechanical strength in diabetic fracture calluses. In vitro, advanced glycation end products (AGEs) impaired cilia formation in osteoblasts and reduced the production of a mineralizing matrix, which were rescued by Foxo1 deletion. Mechanistically, AGEs increased Foxo1 expression and transcriptional activity to inhibit IFT80 expression causing impaired cilia formation. Thus, our findings demonstrate that diabetes impairs fracture healing through Foxo1 mediated inhibition of ciliary IFT80 expression and primary cilia formation, resulting in impaired osteogenesis. Inhibition of Foxo1 and/or restoration of cilia formation has the potential to promote diabetes-impaired fracture healing.