The etiology of RSA is complicated, as more than 40% of RSA cases do not have clear causes and are categorized as URSA(26). URSA arises from a malfunction or interruption in the maternal-fetal interface's immune tolerance mechanisms.. It depends on a complex network of interactions between multiple cells at the maternal-fetal interface. Decidualization, enrichment, and infiltration of decidual immune cells are crucial events for the successful establishment of pregnancy. Numerous studies in recent years have shed light on the role of autophagy in both the normal physiological and pathophysiological processes of the endometrium(9). Relevant research has pointed out that autophagy is significantly increased in the process of endometrial decidualization, and impaired autophagy might be related to an adverse pregnancy outcome(27). In other studies, autophagy deficient transgenic mice with autophagy related protein FIP200 and ATG16L mutation knockout were also observed to have abnormal decidualization and decreased embryo implantation(28) (29). From the above research, we speculated that autophagy is pivotal to the endometrium's decidualization. However, the physiological significance and molecular mechanism of changes in autophagy during decidualization of the endometrium are still unclear and need to be further explored (9) (30). Thus, the differences between autophagy markers or their expression levels that are associated with RSA also need exploration.
We undertook an analysis of gene expression profiling data, specifically GSE165004 and GSE26787, which were screened from the GEO database, and identified the 109 DEARGs between the endometrial of the RSA group and the control group. To investigate the biological processes of DEARGs involved in RSA, we performed enrichment analysis using GO and KEGG. DEARGs were primarily enriched in autophagy, regulation of autophagy, endosome membrane, GTP binding, autophagy-animal pathway, apoptosis pathway, JAK-STAT pathway, PI3K-Akt pathway, and others. Some of these pathways are involved in the process of RSA. The combination of GSEA results suggested that most of the genes were primarily enriched in the Chemokine, PI3K/AKT, and JAK/STAT signaling pathways.
The chemokine/cytokine signaling pathway participates as a mediator of communication between the mother and fetus to promote a healthy pregnancy. Chemokines and their receptors are critical factors in embryo implantation and placental angiogenesis(31), and cytokines are involved in regulating the development of endometrial stromal cells into specialized decidual cells(32). At the same time, a relevant study found that the level of chemokine CXL16 increased when researcher used autophagy inhibitors, and this demonstrated that autophagy could negatively regulate the chemokine CXL16(31). GSEA in the current study suggested that DEARGs might be negatively correlated with the chemokine/cytokine pathway in the endometrium of RSA patients; These results align with those from preceding research
PI3K has an indispensable biological function in a myriad of biological mechanisms such as cell growth, proliferation, angiogenesis, and autophagy(33). PI3K could be used to link the activity of receptor tyrosine kinase and mTOR kinase through a variety of cytokine receptors, regulating autophagy activity in cells(34). A previous study has revealed that activity of the PI3K/Akt pathway, and activity of Akt and Akt isoforms protein levels decreased after decidualization induction(35). Furthermore, during endometriosis, activity of the PI3K/Akt pathway increased and decidual markers (IGFBP1 and PRL) decreased(36). Our results hints that the PI3K/Akt pathway may potentially regulate endometrial autophagy activity in RSA. However, the mechanism of this pathway in regulating the autophagy of endometrial deciduous cells still needs further experimental verification.
The JAK/STAT signaling pathway transduces multiple developmental and homeostatic signals. It is one of the key pathways of decidualization(37), and it has been previously reported that the formation of endometrial receptivity is mediated by the JAK/STAT signal pathway through IFNT induction(38). In the implantation period of sheep, the mRNA level of key signal components of the JAK/STAT pathway in the endometrial lumen epithelium was low(39). The JAK-STAT pathway could also regulate autophagy, As shown in the study of Guo et al(40), when STAT3 is inhibited in lung adenocarcinoma epithelial cells, it will induce autophagy and cell cycle arrest. At the same time, the current study suggested that the JAK-STAT pathway might negatively regulate autophagy in RSA patients.
In the PPI network discerned from this investigation, ten DEARGs- namely AKT2, RPS27A, PTPN11, PIK3CD, PTEN, CTNNB1, KRAS, GSK3B, BCL2L1, and GRB2, were underscored as paramount hub genes. These genes are conjectured to have essential functions in the decidualization of the endometrium in RSA. The top trio targeted DEARGs within the microRNA-gene matrix and transcription factor-gene matrix were PTEN, KRAS, and GSK3B, as well as BCL2L1, AKT2, and PTEN, respectively. The AUC for these ten hub genes was scrutinized for their diagnostic relevance; the AUCs for genes KRAS, PTEN, AKT2, PTPN11, GRB2 ,and PIK3CD fell within 0.800–0.960. This implies that these genes maintain a moderate level of diagnostic precision and could be prospective diagnostic markers for RSA.
AKT2 is instrumental in cellular locomotion, invasive behavior, and metastasis(41). Moreover, it mitigates autophagy through constraining the operation of the transcription factor EB (TFEB), a regulator of various autophagy-associated genes, including LC3B(42). Furthermore, AKT2 serves as a critical catalyst in TTF-instigated autophagy in glioblastoma multiforme, whereby the introduction of an active form of AKT2 diminishes the conversion of LC3-II(43).The RPS27A gene encodes the 40s ribosome protein S27A, it could perform extra-ribosomal functions, and it is reported to be over-expressed in some benign and malignant tumors. However, the specific role of the RPS27A in RSA remains to be determined. PTPN11 is an atypical phosphatase, which could regulate the intracellular kinase-mediated signaling pathways(44). It could also increase or decrease P13K/AKT and JAK/STAT signaling activity(45) (46); the PTPN11-mediated signaling pathway was found to regulate cell proliferation, differentiation, migration, and adhesion(47). PTEN is a natural inhibitor of the PI3K/AKT pathway and could regulate protein synthesis, cell cycle progression, migration, and survival(48). PTEN could also induce autophagy through the PI3K/AKT pathway(49). Relevant data have previously shown that PTEN is involved in alborixin-induced autophagy in neuronal cells(48). KRAS is a GTPase, involved in cell growth, differentiation, and survival pathways(50). KRAS protein regulates multiple cellular functions by mediating KRAS -dependent downstream signaling pathways such as the the RAF-MEK-ERK(MAPK) and PI3K-PTEN-AKT pathways (51) (52). GSK3B represents an isoform of a persistently active serine/threonine kinase, participating in multiple signal transduction pathways that govern a diverse range of vital cellular functions. GSK3B has been shown to suppress autophagy through activating mTORC1 in breast cancer cells(53). Furthermore, inhibition of GSK3B activity could lead to a significant increase of AMP/ATP ratio, thus leading to autophagy induction(54). BCL2L1 involves in apoptosis. The current study demonstrated that BcL-X could interact with Beclin1 to suppress autophagy through dissociating the Beclin1 and PIK3C3 complex, which is an important initiation complex of autophagy. It is speculated that these 10 hub genes might participate in pathogenesis of the endometrium of RSA patients by regulating autophagy.
Successful decidualization of the endometrium promotes immune regulation on the maternal-fetal interface. In recent years, increasing evidence indicates that immune imbalance is involved in maternal-fetal immune tolerance. For example, the high proportion of CD16+ CD56+ NK cells suggests that NK cells in RSA patients have high cytotoxicity(55); and M2 macrophages participate in trophoblast invasion and vascular remodeling.
We utilized the CIBERSORT algorithm to delve deeper into the function of immune cell infiltration in the endometrium of RSA. Autophagy's role in modulating components of the immune system, principally encompassing NK cells, DCs, macrophages along with T and B lymphocytes, has been documented. Hence, we examined the relationship between hub genes and infiltrating immune cells, discovering that these DEARGs (AKT2, BCL2L1, CTNNB1, GRB2, GSK3B, PTEN, and PTPN11) exhibited substantial correlation with immune cells. This could suggest a potential interplay between autophagy and immune response in decidualization of the endometrial microenvironment of RSA patients. Among the immune cells, these DEARGs displayed a positive correlation with activated dendritic cells, resting mast cells, and neutrophils. Conversely, a negative correlation was seen with naive B cells, memory B cells, and plasma cells. However, the intricate molecular mechanisms underpinning these interactions remain elusive and warrant further investigation. Although our approach in the current study helped us to further understand the association between autophagy and abnormal decidualization of the endometrium in RSA, inevitably, Our study is not without limitations. Primarily, it was a retrospective analysis based on bioinformatic data. Future studies should strive to increase the sample size and conduct prospective investigations. Secondly, the volume of data available in public databases is finite. To elucidate autophagy's precise role in the progression of endometrium in RSA, and to circumvent potential inaccuracies and biases comprehensively, all clinical factors and uniform interventional measures should be taken into consideration. Finally, the understanding of DEARGs function is not sufficiently comprehensive; we could not illustrate the expression of DEARGs from protein level, and also could not clearly evaluate the specific pathophysiological mechanisms of DEARGs involved in the development of RSA, which needs further investigation.