Senescent endometrial stromal cells transmit reactive oxygen species to the trophoblast-like cells and impair spreading of blastocyst-like spheroids.

Successful implantation requires a fine-tuned dialog between the invading embryo and the maternal endometrium. Recently, we discovered that premature senescence of endometrial stromal cells (EnSC) might mediate improper decidual transformation of endometrial tissue and impair endometrial-blastocyst interaction. Here, we show that senescent EnSC are characterized by elevated intracellular reactive oxygen species (ROS) levels that originate from mitochondrial dysfunction and insufficient antioxidant defense. Decidualization of senescent EnSC is defective and is accompanied by the elevated intracellular and mitochondrial ROS levels. Antioxidant defense during decidualization is significantly less efficient in senescent EnSC compared to healthy ones. Senescent EnSC secrete increased amounts of ROS into the extracellular space. Elevated ROS released by senescent EnSC shift the redox balance and induce DNA damage in the neighboring trophoblast-like cells. In an in vitro implantation model, we observed impaired spreading of blastocyst-like spheroids into a monolayer of decidualizing senescent EnSC, which could be compensated by pretreatment of the senescent cells with the antioxidant, Tempol. Hence, we propose a possible mechanism that might be responsible, at least in part, for the defective embryo implantation realized via ROS transmitting from senescent EnSC to trophoblast cells. Such transmission results in the accumulation of ROS and subsequent DNA damage in trophoblastic cells, which might lead to improper migration and invasion of an embryo. In light of these findings, the application of antioxidants prior to implantation might be a promising strategy to improve implantation efficiency.

Stromal cell senescence contributes to impaired endometrial decidualization and defective interaction with trophoblast cells.

STUDY QUESTION: What are the consequences of endometrial stromal cell (EnSC) senescence for endometrial function? SUMMARY ANSWER: Senescence of EnSC contributes to impaired endometrial decidualization and impaired interaction with trophoblast cells but application of senomorphics diminishes the adverse effects of senescent EnSC on decidualization and implantation. WHAT IS KNOWN ALREADY: A prolonged and highly disordered pro-inflammatory secretory profile of EnSC, which resembles the senescence-associated secretory phenotype, is associated with implantation failure. Furthermore, it has been suggested that implantation failure may be associated with increased EnSC senescence during the proliferative phase of the menstrual cycle. STUDY DESIGN, SIZE, DURATION: Primary EnSC cell cultures were isolated from endometrial biopsies taken from four patients without any endometrial complications planning to undergo IVF. EnSC senescence was induced by oxidative stress (1 h exposure to 200 µM H2O2) followed by 14 days culture but some results were confirmed in a replicative senescence model (after 25 passages). The decidual reaction was evaluated with routine methods and a genetic tool previously designed by us that estimates integral decidual response by fluorescence of a reporter protein. Time-course RNA-sequencing of control and senescent EnSC before and during decidualization was performed using four replicates for each state. To extend our findings, we applied several publicly available datasets. To model implantation in vitro, the choriocarcinoma cell line BeWo b30 was used. To reduce the senescent phenotype of EnSC, two classical senomorphics were applied-rapamycin and metformin. PARTICIPANTS/MATERIALS, SETTING, METHODS: EnSC cultures were used to investigate the effects of senescence on decidualization and on an in vitro implantation model using spheroids derived from BeWo cells. Co-culture models (2D and 3D) were used to explore the effect of senescent cells on neighbouring control cells. The following methods were used to assess cell function, RNA-sequencing, bioinformatic analysis, CRISPR/Cas9 genome editing, FACS, western blotting, RT-PCR, immunofluorescence, molecular cloning, lentiviral transduction and ELISA. MAIN RESULTS AND THE ROLE OF CHANCE: Premature senescence of EnSC could be a cause of impaired decidualization. Hormone-induced decidual transformation of EnSC cultures was negatively affected by senescence. Bioinformatics revealed crucial disturbances in the decidual reaction of senescent EnSC which could affect embryo invasion, alter the 'meta-signature' of human endometrial receptivity, disturb the emergence of mature and senescent decidual cells subpopulations, impair ligand-receptor interaction with trophoblasts and modify the architecture of extracellular matrix. These predictions were functionally validated using an in vitro implantation model. Moreover, we observed that senescent EnSC, likely via the altered secretome, caused 'bystander' quenching of the decidual reaction in adjacent cells, reinforcing dysfunction of the stromal compartment. Application of senomorphics that reduced the senescence phenotype diminished adverse effects of senescent EnSC on decidualization and implantation. LARGE SCALE DATA: The data used in this study are available in the GEO database (GEO identifier GSE160702). LIMITATIONS, REASONS FOR CAUTION: The present study was based on in vitro cell cultures derived from only four women. Further studies involving patients with impaired implantation are needed to confirm our findings. WIDER IMPLICATIONS OF THE FINDINGS: The presence of senescent EnSC within the stromal compartment of the endometrium may be a risk-factor for the failure of embryo implantation. Application of senomorphics during the proliferative phase of the menstrual cycle is a promising strategy to alleviate negative effects of senescent EnSC and to improve embryo implantation rates. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by the Russian Science Foundation (# 19-74-10038). The authors do not have any competing interests to declare.

"Social Life" of Senescent Cells: What Is SASP and Why Study It?

Cellular senescence was first described as a failure of normal human cells to divide indefinitely in culture. Until recently, the emphasis in the study of cell senescence has been focused on the accompanying intracellular processes. The focus of the attention has been on the irreversible growth arrest and two important physiological functions that rely on it: suppression of carcinogenesis due to the proliferation loss of damaged cells, and the acceleration of organism aging due to the deterioration of the tissue repair mechanism with age. However, the advances of the past years have revealed that senescent cells can impact the surrounding tissue microenvironment, and, thus, that the main consequences of senescence are not solely mediated by intracellular alterations. Recent studies have provided evidence that a pool of molecules secreted by senescent cells, including cytokines, chemokines, proteases and growth factors, termed the senescence-associated secretory phenotype (SASP), via autocrine/paracrine pathways can affect neighboring cells. Today it is clear that SASP functionally links cell senescence to various biological processes, such as tissue regeneration and remodeling, embryonic development, inflammation, and tumorigenesis. The present article aims to describe the "social" life of senescent cells: basically, SASP constitution, molecular mechanisms of its regulation, and its functional role.

[RELATIONSHIP BETWEEN p53/p21/Rb AND MAPK SIGNALING PATHWAYS IN HUMAN ENDOMETRIUM-DERIVED STEM CELLS UNDER OXIDATIVE STRESS].

Human endometrium-derived mesenchymal stem cells (hMESC) under the sublethal oxidative stress induced by H2O2 activate both p53/p21/Rb and p38MAPK/MAPKAPK-2 pathways that are responsible for the induction of hMESC premature senescence (Borodkina et al., 2014). However the mutual relations between p53/p21/Rb and MAPK signaling pathways, including ERK, p38 and JNK remain unexplored as yet. Here, we used the specific inhibitors--pifithrin-α (PFT), U0126, SB203580 and SP600125 to "switch off" one of the proteins in these cascades and to evaluate the functional status alterations of the rest proteins. Suppression each of the MAPK significantly increased the p53 phosphorylation levels, as well as p21 protein expression followed by Rb hypophosphorylation. On the other hand, PFT-induced p53 inhibition enhanced mostly the ERK1/2 activation compared with p38 and JNK. These results suppose the existence of the reciprocal negative regulation between p53- and MAPK-dependent signaling pathways. Analyzing the possible interactions among the members of the MAPK family, we showed that p38 and JNK can function as the ERK antagonists: JNK is capable to activate ERK, while p38 may block the ERK activation. Together, these results demonstrate complex links between different signaling cascades in stressed hMESC, implicating ERK, p38 and JNK in regulation of the premature senescence via p53/p21/Rb pathway.