A functional genetic screen identifies aurora kinase b as an essential regulator of Sox9-positive mouse embryonic lung progenitor cells.

Development of a branching tree in the embryonic lung is crucial for the formation of a fully mature functional lung at birth. Sox9+ cells present at the tip of the primary embryonic lung endoderm are multipotent cells responsible for branch formation and elongation. We performed a genetic screen in murine primary cells and identified aurora kinase b (Aurkb) as an essential regulator of Sox9+ cells ex vivo. In vivo conditional knockout studies confirmed that Aurkb was required for lung development but was not necessary for postnatal growth and the repair of the adult lung after injury. Deletion of Aurkb in embryonic Sox9+ cells led to the formation of a stunted lung that retained the expression of Sox2 in the proximal airways, as well as Sox9 in the distal tips. Although we found no change in cell polarity, we showed that loss of Aurkb or chemical inhibition of Aurkb caused Sox9+ cells to arrest at G2/M, likely responsible for the lack of branch bifurcation. This work demonstrates the power of genetic screens in identifying novel regulators of Sox9+ progenitor cells and lung branching morphogenesis.

Reproductive biology research down under: highlights from the Australian and New Zealand Annual Meeting of the Society for Reproductive Biology, 2021.

Against the backdrop of a global pandemic, the Society for Reproductive Biology (SRB) 2021 meeting reunited the Australian and New Zealand reproductive research community for the first time since 2019 and was the first virtual SRB meeting. Despite the recent global research disruptions, the conference revealed significant advancements in reproductive research, the importance of which span human health, agriculture, and conservation. A core theme was novel technologies, including the use of medical microrobots for therapeutic and sperm delivery, diagnostic hyperspectral imaging, and hydrogel condoms with potential beyond contraception. The importance of challenging the contraceptive status quo was further highlighted with innovations in gene therapies, non-hormonal female contraceptives, epigenetic semen analysis, and in applying evolutionary theory to suppress pest population reproduction. How best to support pregnancies, particularly in the context of global trends of increasing maternal age, was also discussed, with several promising therapies for improved outcomes in assisted reproductive technology, pre-eclampsia, and pre-term birth prevention. The unique insights gained via non-model species was another key focus and presented research emphasised the importance of studying diverse systems to understand fundamental aspects of reproductive biology and evolution. Finally, the meeting highlighted how to effectively translate reproductive research into policy and industry practice.

The LIM-domain only protein 4 contributes to lung epithelial cell proliferation but is not essential for tumor progression.

BACKGROUND: The lung is constantly exposed to environmental challenges and must rapidly respond to external insults. Mechanisms involved in the repair of the damaged lung involve expansion of different epithelial cells to repopulate the injured cellular compartment. However, factors regulating cell proliferation following lung injury remain poorly understood. Here we studied the role of the transcriptional regulator Lmo4 during lung development, in the regulation of adult lung epithelial cell proliferation following lung damage and in the context of oncogenic transformation. METHODS: To study the role of Lmo4 in embryonic lung development, lung repair and tumorigenesis, we used conditional knock-out mice to delete Lmo4 in lung epithelial cells from the first stages of lung development. The role of Lmo4 in lung repair was evaluated using two experimental models of lung damage involving chemical and viral injury. The role of Lmo4 in lung tumorigenesis was measured using a mouse model of lung adenocarcinoma in which the oncogenic K-Ras protein has been knocked into the K-Ras locus. Overall survival difference between genotypes was tested by log rank test. Difference between means was tested using one-way ANOVA after assuring that assumptions of normality and equality of variance were satisfied. RESULTS: We found that Lmo4 was not required for normal embryonic lung morphogenesis. In the adult lung, loss of Lmo4 reduced epithelial cell proliferation and delayed repair of the lung following naphthalene or flu-mediated injury, suggesting that Lmo4 participates in the regulation of epithelial cell expansion in response to cellular damage. In the context of K-Ras(G12D)-driven lung tumor formation, Lmo4 loss did not alter overall survival but delayed initiation of lung hyperplasia in K-Ras(G12D) mice sensitized by naphthalene injury. Finally, we evaluated the expression of LMO4 in tissue microarrays of early stage non-small cell lung cancer and observed that LMO4 is more highly expressed in lung squamous cell carcinoma compared to adenocarcinoma. CONCLUSIONS: Together these results show that the transcriptional regulator Lmo4 participates in the regulation of lung epithelial cell proliferation in the context of injury and oncogenic transformation but that Lmo4 depletion is not sufficient to prevent lung repair or tumour formation.

Endometrial Origins of Stillbirth (EOS), a case-control study of menstrual fluid to understand and prevent preterm stillbirth and associated adverse pregnancy outcomes: study protocol.

INTRODUCTION: Current research aimed at understanding and preventing stillbirth focuses almost exclusively on the role of the placenta. The underlying origins of poor placental function leading to stillbirth, however, remain poorly understood. There is evidence demonstrating that the endometrial environment in which the embryo implants impacts not only the establishment of pregnancy but also the development of some pregnancy outcomes. Menstrual fluid has recently been applied to the study of menstrual disorders such as heavy menstrual bleeding or endometriosis, however, it has great potential in the study of adverse pregnancy outcomes. This study aims to identify differences in menstrual fluid and menstrual cycle characteristics of women who have experienced preterm stillbirth and other associated adverse pregnancy outcomes, compared with those who have not. The association between menstrual fluid composition and menstrual cycle characteristics will also be determined. METHODS AND ANALYSIS: This is a case-control study of women who have experienced a late miscarriage, spontaneous preterm birth or preterm stillbirth or a pregnancy complicated by placental insufficiency (fetal growth restriction or pre-eclampsia), compared with those who have had a healthy term birth. Cases will be matched for maternal age, body mass index and gravidity. Participants will not currently be on hormonal therapy. Women will be provided with a menstrual cup and will collect their sample on day 2 of menstruation. Primary exposure measures include morphological and functional differences in decidualisation of the endometrium (cell types, immune cell subpopulations and protein composition secreted from the decidualised endometrium). Women will complete a menstrual history survey to capture menstrual cycle length, regularity, level of pain and heaviness of flow. ETHICS AND DISSEMINATION: Ethics approval was obtained from Monash University Human Research Ethics Committee (27900) on 14/07/2021 and will be conducted in accordance with these conditions. Findings from this study will be disseminated through peer-reviewed publications and conference presentations.

Endometrial Stem/Progenitor Cells-Their Role in Endometrial Repair and Regeneration.

The human endometrium is a remarkable tissue, undergoing ~450 cycles of proliferation, differentiation, shedding (menstruation), repair, and regeneration over a woman's reproductive lifespan. Post-menstrual repair is an extremely rapid and scar-free process, with re-epithelialization of the luminal epithelium completed within 48 h of initiation of shedding. Following menstruation, the functionalis grows from the residual basalis layer during the proliferative phase under the influence of rising circulating estrogen levels. The regenerative capacity of the endometrium is attributed to stem/progenitor cells which reside in both the epithelial and stromal cell compartments of the basalis layer. Finding a definitive marker for endometrial epithelial progenitors (eEPCs) has proven difficult. A number of different markers have been suggested as putative progenitor markers including, N-cadherin, SSEA-1, AXIN2, SOX-9 and ALDH1A1, some of which show functional stem cell activity in in vitro assays. Each marker has a unique location(s) in the glandular epithelium, which has led to the suggestion that a differentiation hierarchy exists, from the base of epithelial glands in the basalis to the luminal epithelium lining the functionalis, where epithelial cells express different combinations of markers as they differentiate and move up the gland into the functionalis away from the basalis niche. Perivascular endometrial mesenchymal stem cells (eMSCs) can be identified by co-expression of PDGFRß and CD146 or by a single marker, SUSD2. This review will detail the known endometrial stem/progenitor markers; their identity, location and known interactions and hierarchy across the menstrual cycle, in particular post-menstrual repair and estrogen-driven regeneration, as well as their possible contributions to menstruation-related disorders such as endometriosis and regeneration-related disorder Asherman's syndrome. We will also highlight new techniques that allow for a greater understanding of stem/progenitor cells' role in repair and regeneration, including 3D organoids, 3D slice cultures and gene sequencing at the single cell level. Since mouse models are commonly used to study menstruation, repair and regeneration we will also detail the mouse stem/progenitor markers that have been investigated in vivo.

Comparison of Organoids from Menstrual Fluid and Hormone-Treated Endometrium: Novel Tools for Gynecological Research.

Endometrial organoids (EMO) are an important tool for gynecological research but have been limited by generation from (1) invasively acquired tissues and thus advanced disease states and (2) from women who are not taking hormones, thus excluding 50% of the female reproductive-aged population. We sought to overcome these limitations by generating organoids from (1) menstrual fluid (MF; MFO) using a method that enables the concurrent isolation of menstrual fluid supernatant, stromal cells, and leukocytes and (2) from biopsies and hysterectomy samples from women taking hormonal medication (EMO-H). MF was collected in a menstrual cup for 4-6 h on day 2 of menstruation. Biopsies and hysterectomies were obtained during laparoscopic surgery. Organoids were generated from all sample types, with MFO and EMO-H showing similar cell proliferation rates, proportion and localization of the endometrial basalis epithelial marker, Stage Specific Embryonic Antigen-1 (SSEA-1), and gene expression profiles. Organoids from different disease states showed the moderate clustering of epithelial secretory and androgen receptor signaling genes. Thus, MFO and EMO-H are novel organoids that share similar features to EMO but with the advantage of (1) MFO being obtained non-invasively and (2) EMO-H being obtained from 50% of the women who are not currently being studied through standard methods. Thus, MFO and EMO-H are likely to prove to be invaluable tools for gynecological research, enabling the population-wide assessment of endometrial health and personalized medicine.

Partial pulmonary embolization disrupts alveolarization in fetal sheep.

BACKGROUND: Although bronchopulmonary dysplasia is closely associated with an arrest of alveolar development and pulmonary capillary dysplasia, it is unknown whether these two features are causally related. To investigate the relationship between pulmonary capillaries and alveolar formation, we partially embolized the pulmonary capillary bed. METHODS: Partial pulmonary embolization (PPE) was induced in chronically catheterized fetal sheep by injection of microspheres into the left pulmonary artery for 1 day (1d PPE; 115d gestational age; GA) or 5 days (5d PPE; 110-115d GA). Control fetuses received vehicle injections. Lung morphology, secondary septal crests, elastin, collagen, myofibroblast, PECAM1 and HIF1 alpha abundance and localization were determined histologically. VEGF-A, Flk-1, PDGF-A and PDGF-R alpha mRNA levels were measured using real-time PCR. RESULTS: At 130d GA (term approximately 147d), in embolized regions of the lung the percentage of lung occupied by tissue was increased from 29 +/- 1% in controls to 35 +/- 1% in 1d PPE and 44 +/- 1% in 5d PPE fetuses (p < 0.001). Secondary septal crest density was reduced from 8 +/- 0% in controls to 5 +/- 0% in 1d PPE and 4 +/- 0% in 5d PPE fetuses (p < 0.05), indicating impaired alveolar formation. The deposition of differentiated myofibroblasts (23 +/- 1% vs 28 +/- 1%; p < 0.001) and elastin fibres (3 +/- 0% vs 4 +/- 0%; p < 0.05) were also impaired in embolized lung regions of PPE fetuses compared to controls. PPE did not alter the deposition of collagen or PECAM1. At 116d GA in 5d PPE fetuses, markers of hypoxia indicated that a small and transient hypoxic event had occurred (hypoxia in 6.7 +/- 1.4% of the tissue within embolized regions of 5d PPE fetuses at 116d compared to 0.8 +/- 0.2% of tissue in control regions). There was no change in the proportion of tissue labelled with HIF1 alpha. There was no change in mRNA levels of the angiogenic factors VEGF and Flk-1, although a small increase in PDGF-R alpha expression at 116d GA, from 1.00 +/- 0.12 in control fetuses to 1.61 +/- 0.18 in 5d PPE fetuses may account for impaired differentiation of alveolar myofibroblasts and alveolar development. CONCLUSIONS: PPE impairs alveolarization without adverse systemic effects and is a novel model for investigating the role of pulmonary capillaries and alveolar myofibroblasts in alveolar formation.

Cellular Origins of Endometriosis: Towards Novel Diagnostics and Therapeutics.

Endometriosis remains an enigmatic disease of unknown etiology, with delayed diagnosis and poor therapeutic options. This review will discuss the cellular, physiological, and genomic evidence of Sampson's hypothesis of retrograde menstruation as a cause of pelvic endometriosis and as the basis of phenotypic heterogeneity of the disease. We postulate that collaborative research at the single cell level focused on unlocking the cellular, physiological, and genomic mechanisms of endometriosis will be accompanied by advances in personalized diagnosis and therapies that target unique subtypes of endometriosis disease. These advances will address the clinical conundrums of endometriosis clinical care-including diagnostic delay, suboptimal treatments, disease recurrence, infertility, chronic pelvic pain, and quality of life. There is an urgent need to improve outcomes for women with endometriosis. To achieve this, it is imperative that we understand which cells form the lesions, how they arrive at distant sites, and what factors govern their ability to survive and invade at ectopic locations. This review proposes new research avenues to address these basic questions of endometriosis pathobiology that will lay the foundations for new diagnostic tools and treatment pathways.

Gene expression profiling during increased fetal lung expansion identifies genes likely to regulate development of the distal airways.

Growth and development of the fetal lungs is critically dependent on the degree to which the lungs are expanded by liquid; increases in fetal lung expansion accelerate lung growth, whereas reductions in lung expansion cause lung growth to cease. The mechanisms mediating expansion-induced lung growth are unknown but likely include alterations in the expression of genes that regulate lung cell proliferation. Our aim was to isolate and identify genes that are up- or downregulated by increased fetal lung expansion. In chronically catheterized fetal sheep at 126 days gestational age (GA), the left lung was expanded for 36 h, while the right lung remained at a control level of expansion. Subtraction hybridization was used to isolate genes differentially expressed between the left and right lungs. Screening of approximately 6,000 clones identified 1,138 and 118 cDNA fragments that were up- and downregulated by increased lung expansion, respectively. Northern blot analyses in separate groups of control fetuses and fetuses exposed to increased lung expansion were used to verify differential expression. Increased fetal lung expansion upregulated heat shock protein 47, thrombospondin-1, TROP2, tropoelastin, and tubulin-alpha3 in fetal lung tissue by approximately 200-300%; connective tissue growth factor and cysteine-rich angiogenic inducer 61 were increased by 20-30%. Genes downregulated by increased fetal lung expansion included CCSP-related protein-1, elongation factor-1alpha and vitamin D3 upregulated protein 1. We conclude that an increase in fetal lung expansion differentially regulates the expression of numerous genes in lung tissue, many of which have important putative roles in lung development, while the functions of others are currently unknown.

Adult lung stem cells and their contribution to lung tumourigenesis.

The isolation and characterization of lung stem and progenitor cells represent an important step towards the understanding of lung repair after injury, lung disease pathogenesis and the identification of the target cells of transformation in lung carcinogenesis. Different approaches using prospective isolation of progenitor cells by flow cytometry or lineage-tracing experiments in mouse models of lung injury have led to the identification of distinct progenitor subpopulations in different morphological regions of the adult lung. Genetically defined mouse models of lung cancer are offering new perspectives on the cells of origin of different subtypes of lung cancer. These mouse models pave the way to further investigate human lung progenitor cells at the origin of lung cancers, as well as to define the nature of the lung cancer stem cells. It will be critical to establish the link between oncogenic driver mutations recently discovered in lung cancers, target cells of transformation and subtypes of lung cancers to enable better stratification of patients for improved therapeutic strategies.

Stimulation of Activin A/Nodal signaling is insufficient to induce definitive endoderm formation of cord blood-derived unrestricted somatic stem cells.

INTRODUCTION: Unrestricted somatic stem cells (USSC) derived from umbilical cord blood are an attractive alternative to human embryonic stem cells (hESC) for cellular therapy. USSC are capable of forming cells representative of all three germ line layers. The aim of this study was to determine the potential of USSC to form definitive endoderm following induction with Activin A, a protein known to specify definitive endoderm formation of hESC. METHODS: USSC were cultured for (1) three days with or without 100 ng/ml Activin A in either serum-free, low-serum or serum-containing media, (2) three days with or without 100 ng/ml Activin A in combination with 10 ng/ml FGF4 in pre-induction medium, or (3) four days with or without small molecules Induce Definitive Endoderm (IDE1, 100 nM; IDE2, 200 nM) in serum-free media. Formation of definitive endoderm was assessed using RT-PCR for gene markers of endoderm (Sox17, FOXA2 and TTF1) and lung epithelium (surfactant protein C; SPC) and cystic fibrosis transmembrane conductance regulator; CFTR). The differentiation capacity of Activin A treated USSC was also assessed. RESULTS: Activin A or IDE1/2 induced formation of Sox17+ definitive endoderm from hESC but not from USSC. Activin A treated USSC retained their capacity to form cells of the ectoderm (nerve), mesoderm (bone) and endoderm (lung). Activin A in combination with FGF4 did not induce formation of Sox17+ definitive endoderm from USSC. USSC express both Activin A receptor subunits at the mRNA and protein level, indicating that these cells are capable of binding Activin A. CONCLUSIONS: Stimulation of the Nodal signaling pathway with Activin A or IDE1/2 is insufficient to induce definitive endoderm formation from USSC, indicating that USSC differ in their stem cell potential from hESC.