Modeling embryo-endometrial interface recapitulating human embryo implantation.

The initiation of human pregnancy is marked by the implantation of an embryo into the uterine environment; however, the underlying mechanisms remain largely elusive. To address this knowledge gap, we developed hormone-responsive endometrial organoids (EMO), termed apical-out (AO)-EMO, which emulate the in vivo architecture of endometrial tissue. The AO-EMO comprise an exposed apical epithelium surface, dense stromal cells, and a self-formed endothelial network. When cocultured with human embryonic stem cell-derived blastoids, the three-dimensional feto-maternal assembloid system recapitulates critical implantation stages, including apposition, adhesion, and invasion. Endometrial epithelial cells were subsequently disrupted by syncytial cells, which invade and fuse with endometrial stromal cells. We validated this fusion of syncytiotrophoblasts and stromal cells using human blastocysts. Our model provides a foundation for investigating embryo implantation and feto-maternal interactions, offering valuable insights for advancing reproductive medicine.

Trophoblast stem cell-based organoid models of the human placental barrier.

Human placental villi have essential roles in producing hormones, mediating nutrient and waste exchange, and protecting the fetus from exposure to xenobiotics. Human trophoblast organoids that recapitulate the structure of villi could provide an important in vitro tool to understand placental development and the transplacental passage of xenobiotics. However, such organoids do not currently exist. Here we describe the generation of trophoblast organoids using human trophoblast stem (TS) cells. Following treatment with three kinds of culture medium, TS cells form spherical organoids with a single outer layer of syncytiotrophoblast (ST) cells that display a barrier function. Furthermore, we develop a column-type ST barrier model based on the culture condition of the trophoblast organoids. The bottom membrane of the column is almost entirely covered with syndecan 1-positive ST cells. The barrier integrity and maturation levels of the model are confirmed by measuring transepithelial/transendothelial electrical resistance (TEER) and the amount of human chorionic gonadotropin. Further analysis reveals that the model can be used to derive the apparent permeability coefficients of model compounds. In addition to providing a suite of tools for the study of placental development, our trophoblast models allow the evaluation of compound transfer and toxicity, which will facilitate drug development.

CRISPR screening in human trophoblast stem cells reveals both shared and distinct aspects of human and mouse placental development.

The placenta serves as the interface between the mother and fetus, facilitating the exchange of gases and nutrients between their separate blood circulation systems. Trophoblasts in the placenta play a central role in this process. Our current understanding of mammalian trophoblast development relies largely on mouse models. However, given the diversification of mammalian placentas, findings from the mouse placenta cannot be readily extrapolated to other mammalian species, including humans. To fill this knowledge gap, we performed CRISPR knockout screening in human trophoblast stem cells (hTSCs). We targeted genes essential for mouse placental development and identified more than 100 genes as critical regulators in both human hTSCs and mouse placentas. Among them, we further characterized in detail two transcription factors, DLX3 and GCM1, and revealed their essential roles in hTSC differentiation. Moreover, a gene function-based comparison between human and mouse trophoblast subtypes suggests that their relationship may differ significantly from previous assumptions based on tissue localization or cellular function. Notably, our data reveal that hTSCs may not be analogous to mouse TSCs or the extraembryonic ectoderm (ExE) in which in vivo TSCs reside. Instead, hTSCs may be analogous to progenitor cells in the mouse ectoplacental cone and chorion. This finding is consistent with the absence of ExE-like structures during human placental development. Our data not only deepen our understanding of human trophoblast development but also facilitate cross-species comparison of mammalian placentas.

Ocular instillation of conditioned medium from mesenchymal stem cells is effective for dry eye syndrome by improving corneal barrier function.

Dry eye syndrome (DES) is a chronic ocular disease that induces epithelial damage to the cornea by decreasing tear production and quality. Adequate treatment options have not been established for severe DES such as Sjogren's syndrome due to complicated pathological conditions. To solve this problem, we focused on the conditioned medium of human adipose-derived mesenchymal stem cells (hAdMSC-CM), which have multiple therapeutic properties. Here, we showed that hAdMSC-CM suppressed Benzalkonium Chloride (BAC)-induced cytotoxicity and inflammation in human corneal epithelial cells (hCECs). In addition, hAdMSC-CM increased the expression level and regulated the localisation of barrier function-related components, and improved the BAC-induced barrier dysfunction in hCECs. RNA-seq analysis and pharmacological inhibition experiments revealed that the effects of hAdMSC-CM were associated with the TGFß and JAK-STAT signalling pathways. Moreover, in DES model rats with exorbital and intraorbital lacrimal gland excision, ocular instillation of hAdMSC-CM suppressed corneal epithelial damage by improving barrier dysfunction of the cornea. Thus, we demonstrated that hAdMSC-CM has multiple therapeutic properties associated with TGFß and JAK-STAT signalling pathways, and ocular instillation of hAdMSC-CM may serve as an innovative therapeutic agent for DES by improving corneal barrier function.

Association between serum ferritin level and decreased diffusion capacity 3 months after the onset of COVID-19 pneumonia.

BACKGROUND: Coronavirus disease 2019 (COVID-19) pneumonia can have prolonged sequelae and lead to respiratory dysfunction, mainly because of impaired diffusion capacity for carbon monoxide (DLCO). The clinical factors associated with DLCO impairment, including blood biochemistry test parameters, remain unclear. METHODS: Patients with COVID-19 pneumonia who underwent inpatient treatment between April 2020 and August 2021 were included in this study. A pulmonary function test was performed 3 months after onset, and the sequelae symptoms were investigated. Clinical factors, including blood test parameters and abnormal chest shadows on computed tomography, of COVID-19 pneumonia associated with DLCO impairment were investigated. RESULTS: In total, 54 recovered patients participated in this study. Twenty-six patients (48%) and 12 patients (22%) had sequelae symptoms 2 and 3 months after, respectively. The main sequelae symptoms at 3 months were dyspnea and general malaise. Pulmonary function tests showed that 13 patients (24%) had both DLCO <80% predicted value (pred) and DLCO/alveolar volume (VA) <80% pred, and appeared to have DLCO impairment not attributable to an abnormal lung volume. Clinical factors associated with impaired DLCO were investigated in multivariable regression analysis. Ferritin level of >686.5 ng/mL (odds ratio: 11.08, 95% confidence interval [CI]: 1.84-66.59; p = 0.009) was most strongly associated with DLCO impairment. CONCLUSIONS: Decreased DLCO was the most common respiratory function impairment, and ferritin level was a significantly associated clinical factor. Serum ferritin level could be used as a predictor of DLCO impairment in cases of COVID-19 pneumonia.

Genomic imprinting in human placentation.

Background: Genomic imprinting (GI) is a mammalian-specific epigenetic phenomenon that has been implicated in the evolution of the placenta in mammals. Methods: Embryo transfer procedures and trophoblast stem (TS) cells were used to re-examine mouse placenta-specific GI genes. For the analysis of human GI genes, cytotrophoblast cells isolated from human placental tissues were used. Using human TS cells, the biological roles of human GI genes were examined. Main findings: (1) Many previously identified mouse GI genes were likely to be falsely identified due to contaminating maternal cells. (2) Human placenta-specific GI genes were comprehensively determined, highlighting incomplete erasure of germline DNA methylation in the human placenta. (3) Human TS cells retained normal GI patterns. (4) Complete hydatidiform mole-derived TS cells were characterized by aberrant GI and enhanced trophoblastic proliferation. The maternally expressed imprinted gene p57KIP2 may be responsible for the enhanced proliferation. (5) The primate-specific microRNA cluster on chromosome 19, which is a placenta-specific GI gene, is essential for self-renewal and differentiation of human TS cells. Conclusion: Genomic imprinting plays diverse and important roles in human placentation. Experimental analyses using TS cells suggest that the GI maintenance is necessary for normal placental development in humans.

The whole blood transcriptional regulation landscape in 465 COVID-19 infected samples from Japan COVID-19 Task Force.

Coronavirus disease 2019 (COVID-19) is a recently-emerged infectious disease that has caused millions of deaths, where comprehensive understanding of disease mechanisms is still unestablished. In particular, studies of gene expression dynamics and regulation landscape in COVID-19 infected individuals are limited. Here, we report on a thorough analysis of whole blood RNA-seq data from 465 genotyped samples from the Japan COVID-19 Task Force, including 359 severe and 106 non-severe COVID-19 cases. We discover 1169 putative causal expression quantitative trait loci (eQTLs) including 34 possible colocalizations with biobank fine-mapping results of hematopoietic traits in a Japanese population, 1549 putative causal splice QTLs (sQTLs; e.g. two independent sQTLs at TOR1AIP1), as well as biologically interpretable trans-eQTL examples (e.g., REST and STING1), all fine-mapped at single variant resolution. We perform differential gene expression analysis to elucidate 198 genes with increased expression in severe COVID-19 cases and enriched for innate immune-related functions. Finally, we evaluate the limited but non-zero effect of COVID-19 phenotype on eQTL discovery, and highlight the presence of COVID-19 severity-interaction eQTLs (ieQTLs; e.g., CLEC4C and MYBL2). Our study provides a comprehensive catalog of whole blood regulatory variants in Japanese, as well as a reference for transcriptional landscapes in response to COVID-19 infection.

Clinical features of organizing pneumonia in anti-aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders.

BACKGROUND: Anti-aquaporin-4 (AQP4) antibody is an autoantibody marker often observed in patients with neuromyelitis optica spectrum disorder (NMOSD). The pathological relevance of complicated pulmonary disorders in anti-AQP4 antibody-positive NMOSD remains unclear. We aimed to assess the clinical and histological relevance of complicated pulmonary disorders in anti-AQP4 antibody-positive NMOSD. METHODS: We retrospectively reviewed the medical records of 52 patients with anti-AQP4 antibody-positive NMOSD and conducted immunohistochemical evaluations of the lung biopsy specimens. RESULTS: Among 52 patients with anti-AQP4 antibody-positive NMOSD, 4 patients showed pulmonary involvement with a diagnosis of organizing pneumonia (OP). The proportion of males was larger (75% vs. 12.5%; p = 0.013) and creatine kinase levels were higher (458.3 U/L vs. 83.9 U/L; p = 0.003) in patients with OP than in those without OP. OP development preceded or coincided with the NMOSD symptoms. Chest computed tomography findings were consistent with OP in all four patients. Bronchoalveolar lavage fluid predominantly contained lymphocytes. Transbronchial lung biopsy revealed intraluminal plugs of inflammatory debris within the alveoli. Alveolar epithelial cells covering the OP lesions exhibited AQP4 loss, immunoglobulin G deposition, and complement activation. Corticosteroid treatment resulted in clinical improvement of OP. CONCLUSION: OP may be considered a pulmonary manifestation of anti-AQP4 antibody-positive NMOSD beyond the central nervous system. Complement-dependent cytotoxicity of the lung epithelial cells caused by anti-AQP4 antibody is at least partly involved in OP development. When diagnosing NMOSD, the possibility of OP should be carefully evaluated based on the detailed history and chest imaging findings.

The microRNA cluster C19MC confers differentiation potential into trophoblast lineages upon human pluripotent stem cells.

The first cell fate commitment during mammalian development is the specification of the inner cell mass and trophectoderm. This irreversible cell fate commitment should be epigenetically regulated, but the precise mechanism is largely unknown in humans. Here, we show that naïve human embryonic stem (hES) cells can transdifferentiate into trophoblast stem (hTS) cells, but primed hES cells cannot. Our transcriptome and methylome analyses reveal that a primate-specific miRNA cluster on chromosome 19 (C19MC) is active in naïve hES cells but epigenetically silenced in primed ones. Moreover, genome and epigenome editing using CRISPR/Cas systems demonstrate that C19MC is essential for hTS cell maintenance and C19MC-reactivated primed hES cells can give rise to hTS cells. Thus, we reveal that C19MC activation confers differentiation potential into trophoblast lineages on hES cells. Our findings are fundamental to understanding the epigenetic regulation of human early development and pluripotency.

Generation of 3D lacrimal gland organoids from human pluripotent stem cells.

Lacrimal glands are the main exocrine glands of the eyes. Situated within the orbit, behind the upper eyelid and towards the temporal side of each eye, they secrete lacrimal fluid as a major component of the tear film. Here we identify cells with characteristics of lacrimal gland primordia that emerge in two-dimensional eye-like organoids cultured from human pluripotent stem cells1. When isolated by cell sorting and grown under defined conditions, the cells form a three-dimensional lacrimal-gland-like tissue organoid with ducts and acini, enabled by budding and branching. Clonal colony analyses indicate that the organoids originate from multipotent ocular surface epithelial stem cells. The organoids exhibit notable similarities to native lacrimal glands on the basis of their morphology, immunolabelling characteristics and gene expression patterns, and undergo functional maturation when transplanted adjacent to the eyes of recipient rats, developing lumina and producing tear-film proteins.

Impact of emphysema on the prognosis of Mycobacterium avium complex pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major comorbid disease of Mycobacterium avium complex pulmonary disease (MAC-PD). Emphysema is one of the main pathological findings in COPD, a risk factor for chronic pulmonary aspergillosis (CPA), and is associated with poor prognosis. We aimed to clarify the effect of emphysema on mortality in MAC-PD. METHODS: We retrospectively analyzed 203 patients with MAC-PD at The Jikei Daisan Hospital between January 2014 and December 2018. We investigated the mortality and CPA development rates after MAC-PD diagnosis in patients with or without emphysema. RESULTS: Multivariate Cox proportional hazards regression analysis showed the following negative prognostic factors in patients with MAC-PD: emphysema (hazard ratio [HR]: 11.46; 95% confidence interval [CI]: 1.30-100.90; P = 0.028); cavities (HR: 3.12; 95% CI: 1.22-7.94; P = 0.017); and low body mass index (<18.5 kg/m2) (HR: 4.62; 95% CI: 1.63-13.11; P = 0.004). The mortality and occurrence of CPA were higher in MAC-PD patients with than without emphysema (log-rank test, P < 0.0001 and P < 0.0001). CONCLUSION: Our study findings showed that emphysema detected by computed tomography was associated with an increased risk of CPA development and mortality in MAC-PD.

Effects of the dipeptide L-glutamic acid-L-tryptophan on dermatitis in mice and human keratinocytes.

Allergic contact dermatitis (ACD) and atopic dermatitis (AD) are inflammatory eczematous skin diseases caused by various factors. Here, we report that topical application of the dipeptide, L-glutamic acid-L-tryptophan (L-Glu-L-Trp), improved symptoms in both ACD and AD in mice. Using a mouse model of ACD induced by repeated application of 2,4-dinitorofluorbenzene (DNFB), we demonstrated that L-Glu-L-Trp attenuated DNFB-induced skin thickening. In addition, quantification of cytokines in serum revealed that L-Glu-L-Trp suppressed the DNFB-induced increase in the interleukin (IL)-22 level. Moreover, L-Glu-L-Trp attenuated mite antigen extract-induced AD model symptoms such as the increase of skin thickening and elevation of serum IL-22. We also confirmed that the dipeptide structure rather than the individual amino acid components was important for the therapeutic effects of L-Glu-L-Trp. Furthermore, we showed that IL-22 decreased the expression level of filaggrin mRNA in human epidermal keratinocytes, and L-Glu-L-Trp attenuated that effect. These results suggested that the topical application of the dipeptide, L-Glu-L-Trp, to the skin may be useful for treating ACD and AD.

Rheumatoid Arthritis Accompanying Diffuse Panbronchiolitis.

A 58-year-old woman with rheumatoid arthritis (RA) visited our hospital complaining of a persistent cough and sputum for the past year. She had a high cold hemagglutinin titer and chronic sinusitis. Chest computed tomography revealed bilateral diffuse centrilobular nodules, bronchiectasis, and bronchial wall thickening. A surgical lung biopsy was performed that confirmed diffuse panbronchiolitis (DPB) because of the lymphocytic and plasmacytic infiltrates in the respiratory bronchioles. Her condition improved after the administration of clarithromycin. Several cases of RA complicating DPB have previously been reported, but only in Japan. We need to consider DPB as a bronchiolitis types accompanying RA among Japanese patients.

How the Morphology of NiOx-Decorated CeO2 Nanostructures Affects Catalytic Properties in CO2 Methanation.

Effects of morphology and exposed crystal planes of NiOx-decorated CeO2 (NiCeO2) nanostructured catalysts on activity during CO2 methanation were examined, using nanorod (NR), nanocube (NC), and nanooctahedron (NO) structures. The NiCeO2 nanorods (NiCeO2-NR) showed superior activity to NiCeO2-NC and NiCeO2-NO along with excellent selectivity for CH4. This material also demonstrated exceptional durability, with no significant loss of catalytic activity or structural change after use. Comprehensive physicochemical characterization as well as density functional theory calculations determined that the high performance of the NiCeO2-NR was closely related to the large quantity of surface oxygen vacancies and the high degree of reversibility associated with the Ce4+ ↔ Ce3+ redox cycle of the support. These effects originate from the enhanced reactivity of oxygen atoms on the (110) surfaces of the oxide compared with the (100) and (111) surfaces. This information is expected to assist in the rational design of practical catalysts for the activation of CO2 molecules and other important transformations.

A retrospective analysis of pembrolizumab plus chemotherapy versus pembrolizumab monotherapy for advanced or recurrent non-small cell lung cancer.

BACKGROUND: Although clinical trials have investigated the addition of pembrolizumab to chemotherapy for non-small cell lung cancer, none have investigated the addition of chemotherapy to pembrolizumab. METHODS: We conducted a retrospective study of 71 NSCLC patients including 33 treated with pembrolizumab plus chemotherapy (combination therapy group) and 38 treated with pembrolizumab monotherapy (monotherapy group) from 1 May 2016 to 31 August 2020. RESULTS: Eleven of 33 (33.3%) patients in the combination therapy group and 37 of 38 (97.4%) patients in the monotherapy group had programmed cell death ligand-1 (PD-L1) tumor proportion score (TPS) ≥50%. Objective response rate (ORR) and median overall survival (OS) were not significantly different between the combination therapy group and monotherapy group (54.5% vs. 47.4, p = 0.637 and 16.6 vs. 27.0 months, p = 0.463). In patients with PD-L1 TPS ≥50%, ORR and median OS were not different between the combination therapy group and the monotherapy group (63.6% vs. 48.6%, p = 0.499 and not reached vs. 27.0 months, p = 0.976). Thirty-three (100%) patients experienced adverse events (AEs) in the combination therapy group and 32 (84.2%) in the monotherapy group. Treatment discontinuation at 1 year due to AEs occurred more frequently in the combination therapy group (45.2%) than in the monotherapy group (21.1%). CONCLUSION: There was no significant difference in ORR and OS between the two groups, and treatment discontinuation was more frequent in the combination group. A randomized controlled trial is needed to evaluate the addition of chemotherapy to pembrolizumab for first-line treatment in patients with PD-L1 TPS ≥50%.

Unique features and emerging in vitro models of human placental development.

BACKGROUND: The placenta is an essential organ for the normal development of mammalian fetuses. Most of our knowledge on the molecular mechanisms of placental development has come from the analyses of mice, especially histopathological examination of knockout mice. Choriocarcinoma and immortalized cell lines have also been used for basic research on the human placenta. However, these cells are quite different from normal trophoblast cells. METHODS: In this review, we first provide an overview of mouse and human placental development with particular focus on the differences in the anatomy, transcription factor networks, and epigenetic characteristics between these species. Next, we discuss pregnancy complications associated with abnormal placentation. Finally, we introduce emerging in vitro models to study the human placenta, including human trophoblast stem (TS) cells, trophoblast and endometrium organoids, and artificial embryos. MAIN FINDINGS: The placental structure and development differ greatly between humans and mice. The recent establishment of human TS cells and trophoblast and endometrial organoids enhances our understanding of the mechanisms underlying human placental development. CONCLUSION: These in vitro models will greatly advance our understanding of human placental development and potentially contribute to the elucidation of the causes of infertility and other pregnancy complications.

High incidence of false-positive results of IgG antibody against SARS-CoV-2 with rapid immunochromatographic antibody test due to human common cold coronavirus infection.

We experienced a 72-year-old man who developed laboratory-confirmed human coronavirus HKU1 pneumonia. PCR testing for SARS-CoV-2 from a nasopharyngeal specimen was negative twice, and rapid immunochromatographic antibody test (RIAT) using a commercially available kit for IgM and IgG against SARS-CoV-2 showed him turning positive for IgG against SARS-CoV-2. We then performed RIAT in stored serum samples from other patients who suffered laboratory-confirmed human common cold coronaviruses (n = 6) and viruses other than coronavirus (influenza virus, n = 3; rhinovirus, n = 3; metapneumovirus, n = 1; adenovirus, n = 1) admitted until January 2019. Including the present case, four of 7 (57%) showed false-positive RIAT results due to human common cold coronaviruses infection. Two of the 4 patients showed initial negative to subsequent positive RIAT results, indicating seroconversion. RIAT was positive for IgG and IgM in viruses other than coronavirus in 2 (25.0%) and 1 (12.5%) patient. Because of high incidence of false positive RIAT results, cross antigenicity between human common cold coronaviruses and SARS-CoV-2 can be considered. Results of RIAT should be interpreted in light of epidemics of human common cold coronaviruses infection. Prevalence of past SARS-CoV-2 infection may be overestimated due to high incidence of false-positive RIAT results.

Ocular surface ectoderm instigated by WNT inhibition and BMP4.

We sought to elucidate how and when the ocular surface ectoderm commits to its differentiation into the corneal epithelium in eye development from human induced pluripotent stem cells (hiPSCs) under the influence of WNT signaling and the actions of BMP4. These signals are key drivers ocular surface ectodermal cell fate determination. It was discovered that secreted frizzled related protein-2 (SFRP2) and Dickkopf1 (DKK1), which are expressed in neural ectoderm, are both influential in the differentiation of hiPSCs, where they act as canonical WNT antagonists. BMP4, moreover, was found to simultaneously initiate non-neural ectodermal differentiation into a corneal epithelial lineage. Combined treatment of hiPSCs with exogenous BMP4 aligned to WNT inhibition for the initial four days of differentiation increased the ocular surface ectodermal cell population and induced a corneal epithelial phenotype. Specification of a surface ectodermal lineage and its fate is thus determined by a fine balance of BMP4 exposure and WNT inhibition in the very earliest stages of human eye development.

Cell-Type-Specific Adhesiveness and Proliferation Propensity on Laminin Isoforms Enable Purification of iPSC-Derived Corneal Epithelium.

A treatment for intractable diseases is expected to be the replacement of damaged tissues with products from human induced pluripotent stem cells (hiPSCs). Target cell purification is a critical step for realizing hiPSC-based therapy. Here, we found that hiPSC-derived ocular cell types exhibited unique adhesion specificities and growth characteristics on distinct E8 fragments of laminin isoforms (LNE8s): hiPSC-derived corneal epithelial cells (iCECs) and other non-CECs rapidly adhered preferentially to LN332/411/511E8 and LN211E8, respectively, through differential expression of laminin-binding integrins. Furthermore, LN332E8 promoted epithelial cell proliferation but not that of the other eye-related cells, leading to non-CEC elimination by cell competition. Combining these features with magnetic sorting, highly pure iCEC sheets were fabricated. Thus, we established a simple method for isolating iCECs from various hiPSC-derived cells without using fluorescence-activated cell sorting. This study will facilitate efficient manufacture of iCEC sheets for corneal disease treatment and provide insights into target cell-specific scaffold selection.

Generation and validation of a PITX2-EGFP reporter line of human induced pluripotent stem cells enables isolation of periocular mesenchymal cells.

PITX2 (Paired-like homeodomain transcription factor 2) plays important roles in asymmetric development of the internal organs and symmetric development of eye tissues. During eye development, cranial neural crest cells migrate from the neural tube and form the periocular mesenchyme (POM). POM cells differentiate into several ocular cell types, such as corneal endothelial cells, keratocytes, and some ocular mesenchymal cells. In this study, we used transcription activator-like effector nuclease technology to establish a human induced pluripotent stem cell (hiPSC) line expressing a fluorescent reporter gene from the PITX2 promoter. Using homologous recombination, we heterozygously inserted a PITX2-IRES2-EGFP sequence downstream of the stop codon in exon 8 of PITX2 Cellular pluripotency was monitored with alkaline phosphatase and immunofluorescence staining of pluripotency markers, and the hiPSC line formed normal self-formed ectodermal autonomous multizones. Using a combination of previously reported methods, we induced PITX2 in the hiPSC line and observed simultaneous EGFP and PITX2 expression, as indicated by immunoblotting and immunofluorescence staining. PITX2 mRNA levels were increased in EGFP-positive cells, which were collected by cell sorting, and marker gene expression analysis of EGFP-positive cells induced in self-formed ectodermal autonomous multizones revealed that they were genuine POM cells. Moreover, after 2 days of culture, EGFP-positive cells expressed the PITX2 protein, which co-localized with forkhead box C1 (FOXC1) protein in the nucleus. We anticipate that the PITX2-EGFP hiPSC reporter cell line established and validated here can be utilized to isolate POM cells and to analyze PITX2 expression during POM cell induction.