The Application of a Statistical Model Investigating Reactive Oxygen Species in Premature Ageing Syndromes

The premature ageing syndromes Hutchison-Gilford Progeria Syndrome (HGPS) and Restrictive Dermopathy (RD) are rare genetic disorders that result in greatly accelerated ageing. RD is neonatal fatal, whereas children suffering from HGPS age approximately 8 times faster than normal individuals and die during their second decade of life -usually from either stroke or heart disease. The underlying genetic causes of these diseases affect the post-translational processing of the protein lamin A. Lamin A is a Class V intermediate filament protein which resides in the cell nucleus, where it forms a cage-like structure against mechanical strain and is involved in transcriptional regulation, protecting the cell’s genome from damage. HGPS is caused by a mutation in LMNA, the gene encoding lamin A, which results in a truncated mutant protein termed progerin. RD, on the other hand, has genetic roots in the mutation of the metalloprotease Zmpste24, which has a vital role in the processing of prelamin A. The mutation results in the accumulation of immature prelamin A at the nuclear membrane. As a result of increased understanding of the defects in HGPS arising from LMNA mutations a number of therapeutic routes are currently being trialled, but with little success. Work in my supervisor’s laboratory has suggested that defective forms of lamin A may lead to the production of reactive oxygen species (ROS) in cells. ROS can cause a range of damage in cells including DNA damage. This type of damage eventually leads to cellular senescence which is thought to be a precursor to normal ageing. The results put forth here suggest that primary dermal fibroblasts from these premature ageing syndromes show defects in both DNA damage repair and ROS buffering ability. This is shown from my statistical modelling of immunofluorescence data showing DNA double strand break repair over time. RD and HGPS fibroblasts showed persistent γ-H2AX foci after DNA damage induction with oxidative stress, yet showed improved repair after induction with a direct DNA break inducing agent, etoposide. Proliferative markers indicated a reduced proliferative capacity in premature ageing fibroblasts, which was heightened after treatment with oxidative stress. Taken together these results suggest that RD and HGPS fibroblasts more readily enter a state of cellular senescence when exposed to oxidising conditions than control fibroblasts from both and young and old donors. Phenotypical aberrant cellular morphology associated with these diseases was shown to be independent of the defect in ROS buffering ability, supporting evidence showing improvements in abnormal nuclear shape by treatment with farnesyltransferase inhibitors (FTIs) have little impact on the DNA damage repair defects associated with these diseases. From the results here, N-acetyl cysteine (NAC), a powerful antioxidant, has shown to be effective in reducing the proportion of irreparable DNA damage in HGPS and RD fibroblasts. It has also been shown to increase repair rates by actively reducing ROS levels as detected by flow cytometry. NAC treatment therefore shows beneficial properties in treating certain phenotypes associated with progeria and may require consideration as a cooperative form of treatment. The implications of these results are that HGPS is a useful model for normal ageing as fibroblasts from an elderly donor showed signs not dissimilar to those of HGPS, albeit in milder form. These included an increase in the number of persistent γ-H2AX foci and increased ROS levels. This suggests that activation of the HGPS cryptic splice site in normal ageing may account for increased age-associated genomic instability Thus it is tempting to speculate that lamin A is a modulator of both premature and normal ageing through its regulation of cellular oxidative damage

Uncoupling of circadian and other maternal cues in decidualizing endometrial cells

The differentiation of human endometrial stromal cells (HESCs) into specialised decidual cells prepares the endometrium for embryonic implantation. The biochemical and morphological transformation of these cells is highly temporally regulated in order to define a transient period of endometrial receptivity. Currently, the involvement of circadian machinery, and clock dependent pathways in this process are not fully understood. Firstly, analysis of circadian rhythms in HESCs revealed a consistent loss of oscillations in clock components upon decidualization. Down-regulation of Period 2 (PER2) expression, apparent in the early stages of differentiation, was shown to be sufficient to cause this aperiodicity. In turn, temporal suppression of PER2 expression was achieved via reduced CLOCK binding to a non-canonical Ebox enhancer in the PER2 promoter. RNA sequencing analysis upon premature PER2 knockdown revealed a disorganised decidual phenotype in which cell cycle and mitotic regulators were perturbed. As such, PER2 acts to uncouple the endometrium from circadian oscillations during decidualization. Secondly, the gene PRIP-1 was shown to be PER2 dependent in undifferentiated HESCs. Endometrial expression of PRIP-1 was induced and maintained upon decidualization by the post-ovulatory rise in progesterone. Analysis of Ca2+ fluxes demonstrated the ability of PRIP-1 to act as a chelator of IP3 signalling. Additionally, PRIP-1, via its regulation of the AKT pathway, is shown to be an anti-apoptotic regulator in decidual HESCs. Together, these results indicate PRIP-1 functions as a molecular switch in response to progesterone signalling. High PRIP-1 levels during differentiation enable AKT and IP3 mediated cell survival, whilst declining levels upon P4 withdrawal leads to decidual apoptosis. In summary, I provide a novel paradigm whereby both PER2 and PRIP-1 act to uncouple the endometrium from various signalling inputs, enabling an autonomous decidual response. Asynchrony in these pathways can lead to a cascade of events resulting in an array of adverse pregnancy complications

The role of decidual subpopulations at implantation, menstruation and miscarriage

In each menstrual cycle, the endometrium becomes receptive to embryo implantation while preparing for tissue breakdown and repair. Both pregnancy and menstruation are dependent on spontaneous decidualization of endometrial stromal cells, a progesterone-dependent process that follows rapid, estrogen-dependent proliferation. During the implantation window, stromal cells mount an acute stress response, which leads to the emergence of functionally distinct decidual subsets, reflecting the level of replication stress incurred during the preceding proliferative phase. Progesterone-dependent, anti-inflammatory decidual cells (DeC) form a robust matrix and recruit bone marrow-derived decidual progenitors to accommodate the conceptus whereas pro-inflammatory, progesterone-resistant stressed and senescent decidual cells (senDeC) control tissue remodelling and breakdown. To execute these functions, each decidual subset engage innate immune cells: DeC partner with uterine natural killer (uNK) cells to eliminate senDeC, while senDeC co-opt neutrophils and macrophages to assist with tissue breakdown and repair. Thus, successful transformation of cycling endometrium into the decidua of pregnancy not only requires continues progesterone signalling but dominance of DeC over senDeC, aided by recruitment and differentiation of circulating NK cells and bone marrow-derived progenitors. We discuss how the frequency of cycles resulting in imbalanced decidual subpopulations determines the recurrence risk of miscarriage and discuss emerging therapeutic strategies

JAZF1-SUZ12 dysregulates PRC2 function and gene expression during cell differentiation

Polycomb repressive complex 2 (PRC2) methylates histone H3 lysine 27 (H3K27me3) to maintain gene repression and is essential for cell differentiation. In low-grade endometrial stromal sarcoma (LG-ESS), the PRC2 subunit SUZ12 is often fused with the NuA4/TIP60 subunit JAZF1. We show that JAZF1-SUZ12 dysregulates PRC2 composition, genome occupancy, histone modification, gene expression, and cell differentiation. Loss of the SUZ12 N terminus in the fusion protein abrogates interaction with specific PRC2 accessory factors, reduces occupancy at PRC2 target genes, and diminishes H3K27me3. Fusion to JAZF1 increases H4Kac at PRC2 target genes and triggers recruitment to JAZF1 binding sites during cell differentiation. In human endometrial stromal cells, JAZF1-SUZ12 upregulated PRC2 target genes normally activated during decidualization while repressing genes associated with immune clearance, and JAZF1-SUZ12-induced genes were also overexpressed in LG-ESS. These results reveal defects in chromatin regulation, gene expression, and cell differentiation caused by JAZF1-SUZ12 that may underlie its role in oncogenesis

Covalent attachment of fibronectin onto emulsion‐templated porous polymer scaffolds enhances human endometrial stromal cell adhesion, infiltration, and function

A novel strategy for the surface functionalization of emulsion‐templated highly porous (polyHIPE) materials as well as its application to in vitro 3D cell culture is presented. A heterobifunctional linker that consists of an amine‐reactive N‐hydroxysuccinimide ester and a photoactivatable nitrophenyl azide, N‐sulfosuccinimidyl‐6‐(4′‐azido‐2′‐nitrophenylamino)hexanoate (sulfo‐SANPAH), is utilized to functionalize polyHIPE surfaces. The ability to conjugate a range of compounds (6‐aminofluorescein, heptafluorobutylamine, poly(ethylene glycol) bis‐amine, and fibronectin) to the polyHIPE surface is demonstrated using fluorescence imaging, FTIR spectroscopy, and X‐ray photoelectron spectroscopy. Compared to other existing surface functionalization methods for polyHIPE materials, this approach is facile, efficient, versatile, and benign. It can also be used to attach biomolecules to polyHIPE surfaces including cell adhesion‐promoting extracellular matrix proteins. Cell culture experiments demonstrated that the fibronectin‐conjugated polyHIPE scaffolds improve the adhesion and function of primary human endometrial stromal cells. It is believed that this approach can be employed to produce the next generation of polyHIPE scaffolds with tailored surface functionality, enhancing their application in 3D cell culture and tissue engineering whilst broadening the scope of applications to a wider range of cell types

Analysis of chromatin accessibility in decidualizing human endometrial stromal cells

Spontaneous decidualization of the endometrium in response to progesterone signaling is confined to menstruating species, including humans and other higher primates. During this process, endometrial stromal cells (EnSCs) differentiate into specialized decidual cells that control embryo implantation. We subjected undifferentiated and decidualizing human EnSCs to an assay for transposase accessible chromatin with sequencing (ATAC-seq) to map the underlying chromatin changes. A total of 185,084 open DNA loci were mapped accurately in EnSCs. Altered chromatin accessibility upon decidualization was strongly associated with differential gene expression. Analysis of 1533 opening and closing chromatin regions revealed over-representation of DNA binding motifs for known decidual transcription factors (TFs) and identified putative new regulators. ATAC-seq footprint analysis provided evidence of TF binding at specific motifs. One of the largest footprints involved the most enriched motif-basic leucine zipper-as part of a triple motif that also comprised the estrogen receptor and Pax domain binding sites. Without exception, triple motifs were located within Alu elements, which suggests a role for this primate-specific transposable element (TE) in the evolution of decidual genes. Although other TEs were generally under-represented in open chromatin of undifferentiated EnSCs, several classes contributed to the regulatory DNA landscape that underpins decidual gene expression

Progesterone-dependent induction of phospholipase C-related catalytically inactive protein 1 (PRIP-1) in decidualizing human endometrial stromal cells

Decidualization denotes the transformation of endometrial stromal cells into specialized decidual cells. In pregnancy, decidual cells form a protective matrix around the implanting embryo, enabling coordinated trophoblast invasion and formation of a functional placenta. Continuous progesterone (P4) signaling renders decidual cells resistant to various environmental stressors, whereas withdrawal inevitably triggers tissue breakdown and menstruation or miscarriage. Here, we show that PLCL1, coding phospholipase C (PLC)-related catalytically inactive protein 1 (PRIP-1), is highly induced in response to P4 signaling in decidualizing human endometrial stromal cells (HESCs). Knockdown experiments in undifferentiated HESCs revealed that PRIP-1 maintains basal phosphoinositide 3-kinase/Protein kinase B activity, which in turn prevents illicit nuclear translocation of the transcription factor forkhead box protein O1 and induction of the apoptotic activator BIM. By contrast, loss of this scaffold protein did not compromise survival of decidual cells. PRIP-1 knockdown did also not interfere with the responsiveness of HESCs to deciduogenic cues, although the overall expression of differentiation markers, such as PRL, IGFBP1, and WNT4, was blunted. Finally, we show that PRIP-1 in decidual cells uncouples PLC activation from intracellular Ca2+ release by attenuating inositol 1,4,5-trisphosphate signaling. In summary, PRIP-1 is a multifaceted P4-inducible scaffold protein that gates the activity of major signal transduction pathways in the endometrium. It prevents apoptosis of proliferating stromal cells and contributes to the relative autonomy of decidual cells by silencing PLC signaling downstream of Gq protein-coupled receptors

Impact of sustained transforming growth factor-β receptor inhibition on chromatin accessibility and gene expression in cultured human endometrial MSC

Endometrial mesenchymal stem cells (eMSC) drive the extraordinary regenerative capacity of the human endometrium. Clinical application of eMSC for therapeutic purposes is hampered by spontaneous differentiation and cellular senescence upon large-scale expansion in vitro. A83-01, a selective transforming growth factor-β receptor (TGFβ-R) inhibitor, promotes expansion of eMSC in culture by blocking differentiation and senescence, but the underlying mechanisms are incompletely understood. In this study, we combined RNA-seq and ATAC-seq to study the impact of sustained TGFβ-R inhibition on gene expression and chromatin architecture of eMSC. Treatment of primary eMSC with A83-01 for 5 weeks resulted in differential expression of 1,463 genes. Gene ontology analysis showed enrichment of genes implicated in cell growth whereas extracellular matrix genes and genes involved in cell fate commitment were downregulated. ATAC-seq analysis demonstrated that sustained TGFβ-R inhibition results in opening and closure of 3,555 and 2,412 chromatin loci, respectively. Motif analysis revealed marked enrichment of retinoic acid receptor (RAR) binding sites, which was paralleled by the induction of RARB, encoding retinoic acid receptor beta (RARβ). Selective RARβ inhibition attenuated proliferation and clonogenicity of A83-01 treated eMSC. Taken together, our study provides new insights into the gene networks and genome-wide chromatin changes that underpin maintenance of an undifferentiated phenotype of eMSC in prolonged culture

Recurrent pregnancy loss is associated with a pro-senescent decidual response during the peri-implantation window

During the implantation window, the endometrium becomes poised to transition to a pregnant state, a process driven by differentiation of stromal cells into decidual cells (DC). Perturbations in this process, termed decidualization, leads to breakdown of the feto-maternal interface and miscarriage, but the underlying mechanisms are poorly understood. Here, we reconstructed the decidual pathway at single-cell level in vitro and demonstrate that stromal cells first mount an acute stress response before emerging as DC or senescent DC (snDC). In the absence of immune cell-mediated clearance of snDC, secondary senescence transforms DC into progesterone-resistant cells that abundantly express extracellular matrix remodelling factors. Additional single-cell analysis of midluteal endometrium identified DIO2 and SCARA5 as marker genes of a diverging decidual response in vivo. Finally, we report a conspicuous link between a pro-senescent decidual response in peri-implantation endometrium and recurrent pregnancy loss, suggesting that pre-pregnancy screening and intervention may reduce the burden of miscarriage

Impact of sitagliptin on endometrial mesenchymal stem-like progenitor cells : a randomised, double-blind placebo-controlled feasibility trial

Background: Recurrent pregnancy loss (RPL) is associated with the loss of endometrial mesenchymal stem-like progenitor cells (eMSC). DPP4 inhibitors may increase homing and engraftment of bone marrow-derived cells to sites of tissue injury. Here, we evaluated the effect of the DPP4 inhibitor sitagliptin on eMSC in women with RPL, determined the impact on endometrial decidualization, and assessed the feasibility of a full-scale clinical trial. Methods: A double-blind, randomised, placebo-controlled feasibility trial on women aged 18 to 42 years with a history of 3 or more miscarriages, regular menstrual cycles, and no contraindications to sitagliptin. Thirty-eight subjects were randomised to either 100 mg sitagliptin daily for 3 consecutive cycles or identical placebo capsules. Computer generated, permuted block randomisation was used to allocate treatment packs. Colony forming unit (CFU) assays were used to quantify eMSC in midluteal endometrial biopsies. The primary outcome measure was CFU counts. Secondary outcome measures were endometrial thickness, study acceptability, and first pregnancy outcome within 12 months following the study. Tissue samples were subjected to explorative investigations. Findings: CFU counts following sitagliptin were higher compared to placebo only when adjusted for baseline CFU counts and age (RR: 1.52, 95% CI: 1.32–1.75, P<0.01). The change in CFU count was 1.68 in the sitagliptin group and 1.08 in the placebo group. Trial recruitment, acceptability, and drug compliance were high. There were no serious adverse events. Explorative investigations showed that sitagliptin inhibits the expression of DIO2, a marker gene of senescent decidual cells. Interpretation: Sitagliptin increases eMSCs and decreases decidual senescence. A large-scale clinical trial evaluating the impact of preconception sitagliptin treatment on pregnancy outcome in RPL is feasible and warranted. Funding: Tommy's Baby Charity. Clinical trial registration: EU Clinical Trials Register no. 2016-001120-54