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.

Genetic mechanisms influencing COVID-19 susceptibility are not well understood. Here, the authors analyzed whole blood RNA-seq data of 465 Japanese individuals with COVID-19, highlighting thousands of fine-mapped variants affecting expression and splicing of genes, as well as the presence of COVID-19 severity-interaction eQTLs.

Multi-trait and cross-population genome-wide association studies across autoimmune and allergic diseases identify shared and distinct genetic component

OBJECTIVES

Autoimmune and allergic diseases are outcomes of the dysregulation of the immune system. Our study aimed to elucidate differences or shared components in genetic backgrounds between autoimmune and allergic diseases.

METHODS

We estimated genetic correlation and performed multi-trait and cross-population genome-wide association study (GWAS) meta-analysis of six immune-related diseases: rheumatoid arthritis, Graves' disease, type 1 diabetes for autoimmune diseases and asthma, atopic dermatitis and pollinosis for allergic diseases. By integrating large-scale biobank resources (Biobank Japan and UK biobank), our study included 105 721 cases and 433 663 controls. Newly identified variants were evaluated in 21 778 cases and 712 767 controls for two additional autoimmune diseases: psoriasis and systemic lupus erythematosus. We performed enrichment analyses of cell types and biological pathways to highlight shared and distinct perspectives.

RESULTS

Autoimmune and allergic diseases were not only mutually classified based on genetic backgrounds but also they had multiple positive genetic correlations beyond the classifications. Multi-trait GWAS meta-analysis newly identified six allergic disease-associated loci. We identified four loci shared between the six autoimmune and allergic diseases (rs10803431 at PRDM2, OR=1.07, p=2.3×10-8, rs2053062 at G3BP1, OR=0.90, p=2.9×10-8, rs2210366 at HBS1L, OR=1.07, p=2.5×10-8 in Japanese and rs4529910 at POU2AF1, OR=0.96, p=1.9×10-10 across ancestries). Associations of rs10803431 and rs4529910 were confirmed at the two additional autoimmune diseases. Enrichment analysis demonstrated link to T cells, natural killer cells and various cytokine signals, including innate immune pathways.

CONCLUSION

Our multi-trait and cross-population study should elucidate complex pathogenesis shared components across autoimmune and allergic diseases.

Respiratory Impedance is Associated with Ventilation and Diffusing Capacity in Patients with Idiopathic Pulmonary Fibrosis Combined with Emphysema

Purpose

Pulmonary fibrosis and emphysema result in relatively maintained ventilation and reduced diffusing capacity. This pulmonary functional impairment complicates the evaluation of pulmonary function in patients with combined pulmonary fibrosis and emphysema (CPFE). Therefore, a single and easy-to-use pulmonary function index to evaluate patients with CPFE warrants further studies. Respiratory impedance can easily be provided by oscillometry and might be a candidate index to evaluate pulmonary function in patients with CPFE. As a preliminary study to assess the utility of respiratory impedance, we investigated the associations of physiological indices, including respiratory impedance, in patients with idiopathic pulmonary fibrosis (IPF) with and without emphysema.

Patients and Methods

This retrospective study evaluated patients with IPF who did and did not satisfy the diagnostic criteria of CPFE. All patients underwent oscillometry, spirometry, and diffusing capacity for carbon monoxide (D_LCO). Correlations of the obtained physiological indices were analyzed.

Results

In total, 47 patients were included (18 and 29 patients with CPFE and IPF, respectively). Respiratory reactance (Xrs) at 5 Hz (X5) in the inspiratory phase was associated with forced vital capacity (FVC) % predicted in patients with CPFE (r_S=0.576, P=0.012) and IPF (r_S=0.539, P=0.003). Inspiratory X5 positively correlated with D_LCO % predicted only in patients CPFE (r_S=0.637, P=0.004).

Conclusion

Emphysema might associate Xrs with ventilation and diffusing capacity in patients with IPF and emphysema. Given the multiple correlations of Xrs with FVC and D_LCO, this study warrants further studies to verify the utility of oscillometry in a large-scale study for patients with CPFE.

Quantitative evaluation of emphysema for predicting immunotherapy response in patients with advanced non-small-cell lung cancer

The efficacy of immune checkpoint inhibitors (ICIs) in patients with advanced non-small-cell lung cancer (NSCLC) might depend on the presence of emphysema, but this association is not established. We aimed to investigate if quantitively and automatically measuring emphysema can predict the effect of ICIs. We retrospectively analyzed 56 patients with NSCLC who underwent immunotherapy at our hospital. We used the Goddard scoring system (GS) to evaluate the severity of emphysema on baseline CT scans using three-dimensional image analysis software. The emphysema group (GS ≥ 1) showed better progression-free survival (PFS) than the non-emphysema group (GS = 0) (6.5 vs. 2.3 months, respectively, p < 0.01). Multivariate analyses revealed that good performance status, GS of ≥ 1, and high expression of PD-L1 were independently associated with better PFS, while smoking status was not. In conclusion, quantitative evaluation of emphysema can be an objective parameter for predicting the therapeutic effects of ICIs in patients with NSCLC. Our findings can be used to generate hypotheses for future studies.

Opposite response of lung adenocarcinoma and its choroidal metastases upon ramucirumab plus docetaxel therapy after immunotherapy: a case report

We report a unique case of advanced non-small cell lung cancer that exhibited the opposite response to its unilateral choroidal metastases upon ramucirumab plus docetaxel treatment. A combination of cisplatin, pemetrexed, and pembrolizumab was administered as first-line treatment, resulting in shrinkage of all the lesions. However, although the patient was continued on a course of pembrolizumab, all the lesions had recurred approximately two months later. Ramucirumab plus docetaxel, administered as sequential treatment, resulted in maintained shrinkage of the choroidal lesions, yet all the other lesions progressed. Ramucirumab may be a suitable therapy for choroidal metastases, especially if administered immediately after immunotherapy.

Bronchoalveolar lavage fluid reveals factors contributing to the efficacy of PD-1 blockade in lung cancer

Bronchoalveolar lavage is commonly performed to assess inflammation and identify responsible pathogens in lung diseases. Findings from bronchoalveolar lavage might be used to evaluate the immune profile of the lung tumor microenvironment (TME). To investigate whether bronchoalveolar lavage fluid (BALF) analysis can help identify patients with non–small cell lung cancer (NSCLC) who respond to immune checkpoint inhibitors (ICIs), BALF and blood were prospectively collected before initiating nivolumab. The secreted molecules, microbiome, and cellular profiles based on BALF and blood analysis of 12 patients were compared with regard to therapeutic effect. Compared with ICI nonresponders, responders showed significantly higher CXCL9 levels and a greater diversity of the lung microbiome profile in BALF, along with a greater frequency of the CD56⁺ subset in blood T cells, whereas no significant difference in PD-L1 expression was found in tumor cells. Antibiotic treatment in a preclinical lung cancer model significantly decreased CXCL9 in the lung TME, resulting in reduced sensitivity to anti–PD-1 antibody, which was reversed by CXCL9 induction in tumor cells. Thus, CXCL9 might be associated with the lung TME microbiome, and the balance of CXCL9 and lung TME microbiome could contribute to nivolumab sensitivity in patients with NSCLC. BALF analysis can help predict the efficacy of ICIs when performed along with currently approved examinations.

CD14 and lipopolysaccharide-binding protein as novel biomarkers for sarcoidosis by proteomics of serum extracellular vesicles

Sarcoidosis is a complex, polygenic, inflammatory granulomatous multi-organ disease of unknown cause. The granulomatous inflammation in sarcoidosis is driven by the interplay between T cells and macrophages. Extracellular vesicles (EVs) play important roles in intercellular communication. We subjected serum EVs, isolated by size exclusion chromatography, from seven patients with sarcoidosis and five control subjects to non-targeted proteomics analysis. Non-targeted, label-free proteomics analysis detected 2292 proteins in serum EVs; 42 proteins were up-regulated in patients with sarcoidosis relative to control subjects; and 324 proteins were down-regulated. The protein signature of EVs from patients with sarcoidosis reflected disease characteristics such as antigen presentation and immunological disease. Candidate biomarkers were further verified by targeted proteomics analysis (selected reaction monitoring) in 46 patients and 10 control subjects. Notably, CD14 and lipopolysaccharide-binding protein (LBP) were validated by targeted proteomics analysis. Up-regulation of these proteins was further confirmed by immunoblotting, and their expression was strongly increased in macrophages of lung granulomatous lesions. Consistent with these findings, CD14 levels were increased in lipopolysaccharide-stimulated macrophages during multinucleation, concomitant with increased levels of CD14 and LBP in EVs. The area under the curve values of CD14 and LBP were 0.81 and 0.84, respectively, and further increased to 0.98 in combination with angiotensin-converting enzyme and soluble interleukin-2 receptor. These findings suggest that CD14 and LBP in serum EVs, which are associated with granulomatous pathogenesis, can improve the diagnostic accuracy in patients with sarcoidosis.

COVID‐19 in a human T‐cell lymphotropic virus type‐1 carrier

This is the first report of COVID‐19 in a human T‐cell lymphotropic virus type‐1 (HTLV‐1) carrier. HTLV‐1 infection can cause immune dysfunction even in asymptomatic carriers. This case highlights the need for guidance on management of COVID‐19‐HTLV‐1 coinfection, specifically on the appropriate use of corticosteroid treatment while considering secondary infection.

Management of severe hypertension due to lenvatinib in patients with advanced thymic carcinoma: A case report

RATIONALE

Thymic carcinoma (TC) is a malignant mediastinal tumor, and there are no established treatments for pre-treated patients with advanced TC. Recently, lenvatinib was approved for such patients in Japan, ahead of other countries. Higher dose lenvatinib may be more efficacious than conventional treatments, although many patients experience grade 3 hypertension. Therefore, lenvatinib dose reduction remains controversial in terms of efficacy and tolerability.

PATIENT CONCERNS

Case 1 involves a 72-year-old woman who underwent complete resection of TC and was taking cilnidipine and azilsartan for hypertension. Six years later, multiple lung metastases were observed, and lenvatinib was started. Case 2 involves a 60-year-old man with TC, and was taking amlodipine for hypertension. A chest computed tomography showed progression in primary and metastatic lesions, and the patient started lenvatinib.

DIAGNOSES

In both patients, grade 3 hypertension was observed after the administration of lenvatinib.

INTERVENTIONS

In Case 1, lenvatinib dose was reduced 3 times because lenvatinib was not interrupted despite grade 3 hypertension. In contrast, in Case 2, lenvatinib was interrupted when grade 3 hypertension occurred and was resumed after a decrease in blood pressure to baseline.

OUTCOMES

In Case 2, higher tumor regression may have been achieved because of the maintenance of a high dose of lenvatinib compared with that in Case 1.

LESSONS

Lenvatinib is a promising agent for advanced TC; however, hypertension should be addressed cautiously, especially at the outset of administration. Lenvatinib may have to be appropriately interrupted and resumed as soon as the blood pressure is controlled to maximize efficacy and minimize toxicity.

A case of synchronous triple autoimmune disorders secondary to thymoma: Pure red cell aplasia, Good's syndrome, and thymoma-associated multi-organ autoimmunity

Pure red cell aplasia (PRCA), Good's syndrome (GS), and thymoma-associated multiorgan autoimmunity (TAMA) are associated with thymoma. Herein, we describe the case of a 56-year-old woman with PRCA, GS, and TAMA simultaneously. She was treated with cyclosporine, immunoglobulin supplementation, and prednisolone; however, she died of uncontrolled sepsis due to extreme immunosuppression. The combination of these three diseases is likely to lead to fatal infections, and to avoid such infections, it may be necessary to reduce or discontinue immunosuppressants and steroids as soon as possible if the diseases are controlled, as well as regular immunoglobulin supplementation.

Stereotactic Ablative Radiotherapy Using CyberKnife for Stage I Non-small-cell Lung Cancer: A Retrospective Analysis

BACKGROUND/AIM

We evaluated the effectiveness and safety of stereotactic ablative radiotherapy (SABR) delivered using Cyberknife in patients with stage I non-small-cell lung cancer.

PATIENTS AND METHODS

The clinical results of 153 patients with 161 lung cancers treated with CyberKnife between May 2014 and August 2020 at the Osaka University Hospital were retrospectively analyzed. The median age was 80 years (range=48-99 years). Nine patients (5.6%) had interstitial pneumonia. The median radiation dose was 52 Gy (range=40-70 Gy) in 4-10 fractions, and the median follow-up extended to 21.4 months (range=0-68.9 months).

RESULTS

The 2-year local control, progression-free, and overall survival rates were 91.9%, 61.7%, and 84.8%, respectively. Toxicities of grade ≥3 were observed in 13 (8.1%) patients; one patient with interstitial pneumonia developed grade 5 radiation pneumonitis and one patient developed grade 5 bronchopulmonary hemorrhage.

CONCLUSION

In patients with stage I non-small-cell lung cancer, SABR using Cyberknife was effective with acceptable toxicity.

Case report: Acute exacerbation of interstitial pneumonia related to mRNA COVID-19 vaccination

Messenger RNA (mRNA) vaccines that protect against COVID-19 are widely used in many countries owing to their high efficacy and safety profiles. Recently, few severe adverse events, such as anaphylaxis and myocarditis, were reported in healthy individuals. The safety of mRNA COVID-19 vaccines has not been adequately studied in patients with interstitial lung disease. We report 2 cases of acute exacerbation of preexisting interstitial pneumonia associated with mRNA COVID-19 vaccination. In both cases, lung disease was stable before the vaccination. Initial responses to steroid therapy were unfavorable, and intravenous cyclophosphamide was administered in both cases. Both patients were diagnosed with vaccine-related exacerbation of interstitial pneumonia based on laboratory results, radiologic features, and the observed clinical course, which lacked other causative events. We suggest that clinicians should note the possibility of acute exacerbation of pneumonia after mRNA COVID-19 vaccination and carefully monitor patients with interstitial lung disease.

Comprehensive and long-term surveys of COVID-19 sequelae in Japan, an ambidirectional multicentre cohort study: study protocol

INTRODUCTION

The rapid spread of COVID-19 posed a global burden. Substantial number of people died of the disease in the acute phase of infection. In addition, a significant proportion of patients have been reported to suffer from post-acute phase symptoms, sequelae of COVID-19, which may negatively influence the quality of daily living and/or socioeconomic circumstances of the patients. However, no previous study has comprehensively and objectively assessed the quality of life of patients by using existing international scales. Further, evidence of socioeconomic consequences among patients with COVID-19 is scarce. To address the multidimensional issues from sequelae of COVID-19, evidence from comprehensive surveys beyond clinical perspectives is critical that investigates health, and social determinants of disease progression as well as socioeconomic consequences at a large scale.

METHODS AND ANALYSIS

In this study, we plan to conduct a nationwide and comprehensive survey for the sequelae of COVID-19 in a total of 1000 patients diagnosed at 27 hospitals throughout Japan. This study will evaluate not only the health-related status of patients from clinical perspectives but also the Health-related Quality of Life (HRQoL) scores, socioeconomic status and consequences to discuss the sequelae of the disease and the related risk factors. The primary endpoint is the frequency of long-term complications of COVID-19 infection. The secondary endpoints are risk factors for progression to sequelae of COVID-19 infection. The study will provide robust and important evidence as a resource to tackle the issues from the sequelae of COVID-19 from the multi-dimensional perspectives.

ETHICS AND DISSEMINATION

This trial was approved by the Keio University School of Medicine Ethics Committee (20200243, UMIN000042299). The results of this study will be reported at a society meeting or published in a peer-reviewed journal.

Prolonged corticosteroid therapy and cytomegalovirus infection in patients with severe COVID-19

Systemic corticosteroid therapy is frequently used to treat coronavirus disease 2019 (COVID‐19). However, its maximum duration without secondary infections remains unclear. We aimed to evaluate the utility of monitoring cytomegalovirus (CMV) infection in patients with COVID‐19 and estimate the maximum duration of systemic corticosteroid therapy without secondary infections. We included 59 patients with severe COVID‐19 without CMV infection on admission to the intensive care unit (ICU). All patients received systemic corticosteroid therapy under invasive mechanical ventilation, with examination for plasma CMV‐deoxyribonucleic acid (DNA) levels during the ICU stay. We analyzed the correlations among patient characteristics, CMV infection, diseases, and patient mortality. CMV infections were newly identified in 15 (25.4%) patients; moreover, anti‐CMV treatment was administered to six (10.2%) patients during the ICU stay. Four (6.8%) patients had secondary infection‐related mortality. The cumulative incidences of CMV infection and anti‐CMV treatment during the ICU stay were 26.8% (95% confidence interval [CI], 15.8%–39.0%) and 12.3% (95% CI, 4.8%–23.4%), respectively. Furthermore, the median duration of systemic corticosteroid therapy without CMV infection was 15 days (95% CI, 13–16 days). The presence of CMV infection was associated with mortality during the ICU stay (p = 0.003). Monitoring plasma CMV‐DNA levels could facilitate the detection of secondary CMV infection due to prolonged systemic corticosteroid therapy. The duration of systemic corticosteroid therapy for COVID‐19 should be limited.

Hemodynamic Analysis of Cerebral AVMs with 3D Phase-Contrast MR Imaging

BACKGROUND AND PURPOSE

The hemodynamics associated with cerebral AVMs have a significant impact on their clinical presentation. This study aimed to evaluate the hemodynamic features of AVMs using 3D phase-contrast MR imaging with dual velocity-encodings.

MATERIALS AND METHODS

Thirty-two patients with supratentorial AVMs who had not received any previous treatment and had undergone 3D phase-contrast MR imaging were included in this study. The nidus diameter and volume were measured for classification of AVMs (small, medium, or large). Flow parameters measured included apparent AVM inflow, AVM inflow index, apparent AVM outflow, AVM outflow index, and the apparent AVM inflow-to-outflow ratio. Correlation coefficients between the nidus volume and each flow were calculated. The flow parameters between small and other AVMs as well as between nonhemorrhagic and hemorrhagic AVMs were compared.

RESULTS

Patients were divided into hemorrhagic (n = 8) and nonhemorrhagic (n = 24) groups. The correlation coefficient between the nidus volume and the apparent AVM inflow and outflow was .83. The apparent AVM inflow and outflow in small AVMs were significantly smaller than in medium AVMs (P < .001 for both groups). The apparent AVM inflow-to-outflow ratio was significantly larger in the hemorrhagic AVMs than in the nonhemorrhagic AVMs (P = .02).

CONCLUSIONS

The apparent AVM inflow-to-outflow ratio was the only significant parameter that differed between nonhemorrhagic and hemorrhagic AVMs, suggesting that a poor drainage system may increase AVM pressure, potentially causing cerebral hemorrhage.

Detecting halfmetallic electronic structures of spintronic materials in a magnetic field

Band-gap engineering is one of the fundamental techniques in semiconductor technology and also applicable in next generation spintronics using the spin degree of freedom. To fully utilize the spintronic materials, it is essential to optimize the spin-dependent electronic structures in the operando conditions by applying magnetic and/or electric fields. Here we present an advanced spectroscopic technique to probe the spin-polarized electronic structures by using magnetic circular dichroism (MCD) in resonant inelastic soft X-ray scattering (RIXS) under an external magnetic field. Thanks to the spin-selective dipole-allowed transitions in RIXS-MCD, we have successfully demonstrated the direct evidence of the perfectly spin-polarized electronic structures for the prototypical halfmetallic Heusller alloy \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {Co}_2\hbox {MnSi}$$\end{document}Co2MnSi. RIXS-MCD is a promising tool to probe the spin-dependent carriers and band-gap induced in the buried magnetic layers in an element specific way under the operando conditions.

COVID-19 in a patient with sporadic lymphangioleiomyomatosis awaiting lung transplantation

Coronavirus disease 2019 (COVID-19) is an emerging viral disease with a mortality that depends on the individual's condition. Underlying comorbidities are major risk factors for COVID-19-related morbidity and mortality. However, information regarding the clinical course of COVID-19 in patients with rare respiratory system diseases is lacking. Here, we present a case of severe COVID-19 in a patient with advanced sporadic lymphangioleiomyomatosis (LAM) who was awaiting lung transplantation. She experienced a marked worsening of her respiratory status despite the limited size of the infiltrations seen on chest computed tomography. She responded to treatment with dexamethasone and remdesivir, and did not require mechanical ventilation. She recovered her pre-COVID-19 respiratory function. This case illustrates that patients with severe lung parenchymal destruction due to advanced LAM are at risk of worsening hypoxemia, but may not have a bad outcome if managed appropriately. Prevention and early diagnosis of COVID-19 are crucial in patients with advanced LAM. Future studies are needed to improve understanding of the clinical features and optimal treatment of COVID-19 in patients with LAM.

IL-33 Induces Sema4A Expression in Dendritic Cells and Exerts Antitumor Immunity

Cancer immunotherapy has shown great promise as a new standard therapeutic strategy against cancer. However, the response rate and survival benefit remain unsatisfactory because most current approaches, such as the use of immune checkpoint inhibitors, depend on spontaneous antitumor immune responses. One possibility for improving the efficacy of immunotherapy is to promote antitumor immunity using adjuvants or specific cytokines actively. IL-33 has been a candidate for such cytokine therapies, but it remains unclear how and in which situations IL-33 exerts antitumor immune effects. In this study, we demonstrate the potent antitumor effects of IL-33 using syngeneic mouse models, which included marked inhibition of tumor growth and upregulation of IFN-γ production by tumor-infiltrating CD8⁺ T cells. Of note, IL-33 induced dendritic cells to express semaphorin 4A (Sema4A), and the absence of Sema4A abolished the antitumor activity of IL-33, indicating that Sema4A is intrinsically required for the antitumor effects of IL-33 in mice. Collectively, these results not only present IL-33 and Sema4A as potential therapeutic targets but also shed light on the potential use of Sema4A as a biomarker for dendritic cell activation status, which has great value in various fields of cancer research, including vaccine development.

Fatal cytomegalovirus pneumonia in a critically ill patient with COVID-19

Coronavirus disease 2019 (COVID-19) can cause severe lymphopenia and respiratory failure requiring prolonged invasive mechanical ventilation (MV). COVID-19 patients with severe lymphopenia or respiratory failure are at risk of developing secondary infections. Here, we present the needle autopsy findings of a critically ill patient with COVID-19 who required reintubation and prolonged MV, and eventually died of secondary cytomegalovirus (CMV) pneumonia. This case highlights the potential risk of long-term steroid use and the need for routine monitoring for CMV infection in critically ill patients with COVID-19.

CD9-positive cells in the intermediate lobe of the pituitary gland are important supplier for prolactin-producing cells in the anterior lobe

A supply of hormone-producing cells from stem/progenitor cells is critical to sustain the endocrine activity of the pituitary gland. In the adenohypophysis composing the anterior and intermediate lobe (AL and IL, respectively), stem/progenitor cells expressing sex-determining region Y-box 2 (SOX2) and S100β are located in the marginal cell layer (MCL) facing Rathke's cleft (primary niche) and the parenchyma of the AL (secondary niche). Our previous studies using mice and rats indicated that the tetraspanin superfamily CD9 and CD81 are expressed in S100β/SOX2-positive cells of primary and secondary niches (named CD9/CD81/S100β/SOX2-positive cell), and the cells located in the AL-side niches exhibit plasticity and multipotency. However, it is unclear whether CD9/CD81/S100β/SOX2-positive cells in the IL-side primary niche are stem/progenitor cells for the AL or IL. Here, we successfully isolated pure CD9/CD81/S100β/SOX2-positive cells from the IL-side primary niche. They had a higher level of S100β and SOX2 mRNA and a greater pituisphere forming capacity than those of CD9/CD81/S100β/SOX2-positive cells isolated from the AL. They also had capacity to differentiate into all types of adenohypophyseal hormone-producing cells, concomitantly with the loss of CD9 expression. Loss of CD9 and CD81 function in CD9/CD81/S100β/SOX2-positive cells by siRNA treatment impaired prolactin cell differentiation. Consistently, in the pituitary gland of CD9/CD81 double knockout mice, dysgenesis of the MCL and a lower population of prolactin cells were observed. These results suggest that the CD9/CD81/S100β/SOX2-positive cells in the MCL of the IL-side are potential suppliers of adult core stem cells in the AL.