Erratum: Modified Fear Conditioning for Inducing Flight Behaviors in Mice.

This corrects the article 10.3791/66266.

Disruption of sphingomyelin synthase 2 gene alleviates cognitive impairment in a mouse model of Alzheimer's disease.

The membrane raft accommodates the key enzymes synthesizing amyloid ß (Aß). One of the two characteristic components of the membrane raft, cholesterol, is well known to promote the key enzymes that produce amyloid-ß (Aß) and exacerbate Alzheimer's disease (AD) pathogenesis. Given that the raft is a physicochemical platform for the sound functioning of embedded bioactive proteins, the other major lipid component sphingomyelin may also be involved in AD. Here we knocked out the sphingomyelin synthase 2 gene (SMS2) in 3xTg AD model mice by hybridization, yielding SMS2KO mice (4S mice). The novel object recognition test in 9/10-month-old 4S mice showed that cognitive impairment in 3xTg mice was alleviated by SMS2KO, though performance in the Morris water maze (MWM) was not improved. The tail suspension test detected a depressive trait in 4S mice, which may have hindered the manifestation of performance in the wet, stressful environment of MWM. In the hippocampal CA1, hyperexcitability in 3xTg was also found alleviated by SMS2KO. In the hippocampal dentate gyrus of 4S mice, the number of neurons positive with intracellular Aß or its precursor proteins, the hallmark of young 3xTg mice, is reduced to one-third, suggesting an SMS2KO-led suppression of syntheses of those peptides in the dentate gyrus. Although we previously reported that large-conductance calcium-activated potassium (BK) channels are suppressed in 3xTg mice and their recovery relates to cognitive amelioration, no changes occurred by hybridization. Sphingomyelin in the membrane raft may serve as a novel target for AD drugs.

Association between preoperative lactate level and early complications after surgery for isolated extremity fracture.

BACKGROUND: The role of lactate level in selecting the timing of definitive surgery for isolated extremity fracture remains unclear. Therefore, we aimed to elucidate the use of preoperative lactate level for predicting early postoperative complications. METHODS: This was a single-center retrospective observational study of patients with isolated extremity fracture who underwent orthopedic surgery. Patients who underwent lactate level assessment within 24 h prior to surgery were included. The incidence of early postoperative complications was compared between patients with a preoperative lactate level of ≥ 2 and < 2 mmol/L. Moreover, subgroup analyses were performed based on the time from hospital arrival to surgery and fracture type. RESULTS: In total, 187 patients were included in the study. The incidence of postoperative complications was significantly higher in patients with a preoperative lactate level of ≥ 2 mmol/L than those with a preoperative lactate level of < 2 mmol/L. This result did not change after adjusting for age and severity. Further, a high preoperative lactate level was associated with a greater incidence of postoperative complications in patients who underwent definitive surgery within 6 h after arrival. CONCLUSION: A preoperative lactate level of ≥ 2 mmol/L was associated with a greater incidence of early postoperative complications in isolated extremity fractures. Nevertheless, this correlation was only observed among patients who underwent definitive fixation within 6 h after hospital arrival.

Spatiotemporal development of the neuronal accumulation of amyloid precursor protein and the amyloid plaque formation in the brain of 3xTg-AD mice.

The amyloid plaque is a hallmark of Alzheimer's disease. The accumulation of the amyloid precursor protein (APP) in the neuronal structure is assumed to lead to amyloid plaque formation through the excessive production of ß-amyloid protein. To study the relationship between the neuronal accumulation of APP and amyloid plaque formation, we histologically analyzed their development in the different brain regions in 3xTg-AD mice, which express Swedish mutated APP (APPSWE) in the neurons. Observation throughout the brain revealed APPSWE-positive somata in the broad regions. Quantitative model analysis showed that the somatic accumulation of APPSWE developed firstly in the hippocampus from a very early age (<1 month) and proceeded slower in the isocortex. In line with this, the hippocampus was the first region to form amyloid plaques at the age of 9-12 months, while amyloid plaques were rarely observed in the isocortex. Females had more APPSWE-positive somata and plaques than males. Furthermore, amyloid plaques were observed in the lateral septum and pontine grey, which did not contain APPSWE-positive somata but only the APPSWE-positive fibers. These results suggested that neuronal accumulation of APPSWE, both in somatodendritic and axonal domains, is closely related to the formation of amyloid plaques.

Immediate Angiography and Decreased In-Hospital Mortality of Adult Trauma Patients: A Nationwide Study.

PURPOSE: This study aimed to elucidate whether immediate angiography within 30 min is associated with lower in-hospital mortality compared with non-immediate angiography. MATERIALS AND METHODS: We conducted a retrospective cohort study using a nationwide trauma databank (2019-2020). Adult trauma patients who underwent emergency angiography within 12 h after hospital arrival were included. Patients who underwent surgery before angiography were excluded. Immediate angiography was defined as one performed within 30 min after arrival (door-to-angio time ≤ 30 min). In-hospital mortality and non-operative management (NOM) failure were compared between patients with immediate and non-immediate angiography. Inverse probability weighting with propensity scores was conducted to adjust patient demographics, injury mechanism and severity, vital signs on hospital arrival, and resuscitative procedures. A restricted cubic spline curve was drawn to reveal survival benefits by door-to-angio time. RESULTS: Among 1,455 patients eligible for this study, 92 underwent immediate angiography. Angiography ≤ 30 min was associated with decreased in-hospital mortality (5.0% vs 11.1%; adjusted odds ratio [OR], 0.42 [95% CI, 0.31-0.56]; p < 0.001), as well as lower frequency of NOM failure: thoracotomy and laparotomy after angiography (0.8% vs. 1.8%; OR, 0.44 [0.22-0.89] and 2.6% vs. 6.5%; OR, 0.38 [0.26-0.56], respectively). The spline curve showed a linear association between increasing mortality and prolonged door-to-angio time in the initial 100 min after arrival. CONCLUSION: In trauma patients, immediate angiography ≤ 30 min was associated with lower in-hospital mortality and fewer NOM failures. LEVEL OF EVIDENCE: Level 3b, non randomized controlled cohort/follow up study.

Development of a rapid and comprehensive genomic profiling test supporting diagnosis and research for gliomas.

A prompt and reliable molecular diagnosis for brain tumors has become crucial in precision medicine. While Comprehensive Genomic Profiling (CGP) has become feasible, there remains room for enhancement in brain tumor diagnosis due to the partial lack of essential genes and limitations in broad copy number analysis. In addition, the long turnaround time of commercially available CGPs poses an additional obstacle to the timely implementation of results in clinics. To address these challenges, we developed a CGP encompassing 113 genes, genome-wide copy number changes, and MGMT promoter methylation. Our CGP incorporates not only diagnostic genes but also supplementary genes valuable for research. Our CGP enables us to simultaneous identification of mutations, gene fusions, focal and broad copy number alterations, and MGMT promoter methylation status, with results delivered within a minimum of 4 days. Validation of our CGP, through comparisons with whole-genome sequencing, RNA sequencing, and pyrosequencing, has certified its accuracy and reliability. We applied our CGP for 23 consecutive cases of intracranial mass lesions, which demonstrated its efficacy in aiding diagnosis and prognostication. Our CGP offers a comprehensive and rapid molecular profiling for gliomas, which could potentially apply to clinical practices and research primarily in the field of brain tumors.

Delta Shock Index and higher incidence of emergency surgery in older adults with blunt trauma.

PURPOSE: Vital signs are important for predicting clinical outcomes in patients with trauma. However, their accuracy can be affected in older adults because hemodynamic changes are less obvious. This study aimed to examine the usefulness of changes in vital signs during transportation in predicting the need for hemostatic treatments in older patients with trauma. METHODS: This retrospective cohort study was conducted using data from the Japan Trauma Data Bank (2004-2019). Patients aged ≥ 65 years who were hemodynamically stable at the scene were included in this study. The incidence of emergency surgery within 12 h after hospital arrival was compared between patients with delta Shock Index (dSI) > 0.1 and those with dSI ≤ 0.1. Predicting ability was examined after adjusting for patient demographics, comorbidities, vital signs at the scene and on hospital arrival, Injury Severity Score, and abbreviated injury scale in each region. RESULTS: Among the 139,242 patients eligible for the study, 3,701 underwent urgent hemostatic surgery within 12 h. Patients with dSI > 0.1 showed a significantly higher incidence of emergency surgery than those with dSI ≤ 0.1 (871/16,549 [5.3%] vs. 2,830/84,250 [3.4%]; odds ratio (OR), 1.60 [1.48-1.73]; adjusted OR, 1.22 [1.08-1.38]; p = 0.001). The relationship between high dSI and a higher incidence of intervention was observed in patients with hypertension and those with decreased consciousness on arrival. CONCLUSION: High dSI > 0.1 was significantly associated with a higher incidence of urgent hemostatic surgery in older patients.

A case of renal cell carcinoma with antiphospholipid syndrome treated by robot-assisted partial nephrectomy.

Introduction: Antiphospholipid syndrome is an autoimmune disease that presents with thrombus hyperplasia. Although very rare, this disease is reported to become severe after the surgical invasion and other interventions. To our knowledge, there are no reports of partial nephrectomy in patients with antiphospholipid. Case presentation: A 45-year-old man visited our hospital for treatment of left renal cell carcinoma. He had a history of antiphospholipid syndrome and took two antithrombotic agents. We performed a robot-assisted partial nephrectomy. We selectively ligated only the feeding branch during the procedure. Postoperatively, there were no complications, and the patient was discharged on postoperative day 10. One year after surgery, there was no worsening of antiphospholipid syndrome. Conclusion: We reported the first case of robot-assisted partial nephrectomy for an antiphospholipid syndrome patient. Selective ligation of the renal artery might not have contributed to the severe antiphospholipid syndrome.

Nardilysin determines hematopoietic stem cell fitness by regulating protein synthesis.

Nardilysin (NRDC) is a multifunctional protein required for maintaining homeostasis in various cellular and tissue contexts. However, its role in hematopoietic stem cells (HSCs) remains unclear. Here, through the conditional deletion of NRDC in hematopoietic cells, we demonstrate that NRDC is required for HSCs expansion in vitro and the reconstitution of hematopoiesis in vivo after transplantation. We found NRDC-deficient HSCs lose their self-renewal ability and display a preferential bias to myeloid differentiation in response to replication stress. Transcriptome data analysis revealed the upregulation of heat shock response-related genes in NRDC-deficient HSCs. Additionally, we observed increased protein synthesis in cultured NRDC-deficient HSCs. Thus, loss of NRDC may cause the inability to control protein synthesis in response to replication induced protein stress, leading to the impaired HSC self-renewal ability. This highlights a novel model of action of NRDC specifically in HSCs.

Intravascular Large B-cell Lymphoma Presenting as Pulmonary Ground-glass Nodules That Progressed Slowly over Several Months with No Overt Symptoms.

A 74-year-old man with no overt symptoms was referred for a chest computed tomography (CT) that revealed multiple bilaterally pulmonary ground-glass nodules (GGNs) with subtle changes in size over eight months. Surgical lung biopsies were performed in the left upper lobe. A pathologic study confirmed the intravascular large B-cell lymphoma (IVLBCL). This lesion was a nodule-like cluster of atypical cells, meaning that it had been localized for several months. Pulmonary IVLBCL may form focal lesions presenting as GGN on chest CT and progress slowly without apparent symptoms.

Regulation of lymphoid-myeloid lineage bias through regnase-1/3-mediated control of Nfkbiz.

ABSTRACT: Regulation of lineage biases in hematopoietic stem and progenitor cells (HSPCs) is pivotal for balanced hematopoietic output. However, little is known about the mechanism behind lineage choice in HSPCs. Here, we show that messenger RNA (mRNA) decay factors regnase-1 (Reg1; Zc3h12a) and regnase-3 (Reg3; Zc3h12c) are essential for determining lymphoid fate and restricting myeloid differentiation in HSPCs. Loss of Reg1 and Reg3 resulted in severe impairment of lymphopoiesis and a mild increase in myelopoiesis in the bone marrow. Single-cell RNA sequencing analysis revealed that Reg1 and Reg3 regulate lineage directions in HSPCs via the control of a set of myeloid-related genes. Reg1- and Reg3-mediated control of mRNA encoding Nfkbiz, a transcriptional and epigenetic regulator, was essential for balancing lymphoid/myeloid lineage output in HSPCs in vivo. Furthermore, single-cell assay for transposase-accessible chromatin sequencing analysis revealed that Reg1 and Reg3 control the epigenetic landscape on myeloid-related gene loci in early stage HSPCs via Nfkbiz. Consistently, an antisense oligonucleotide designed to inhibit Reg1- and Reg3-mediated Nfkbiz mRNA degradation primed hematopoietic stem cells toward myeloid lineages by enhancing Nfkbiz expression. Collectively, the collaboration between posttranscriptional control and chromatin remodeling by the Reg1/Reg3-Nfkbiz axis governs HSPC lineage biases, ultimately dictating the fate of lymphoid vs myeloid differentiation.

Hyperoxia for sepsis and development of acute lung injury with increased mortality.

BACKGROUND: Supraphysiological oxygen administration causes unfavourable clinical outcomes in various diseases. This study aimed to determine whether hyperoxia would be associated with increased mortality in patients with severe infection. METHODS: A post-hoc analysis of a nationwide multicentre prospective observational study on sepsis (SPICE Study) was conducted, including adult patients admitted to the intensive care unit with available arterial partial pressure of oxygen (PaO2) at the treatment initiation for severe infection. Hyperoxia was defined as a PaO2 level of ≥300 mm Hg and in-hospital mortality was compared between patients with and without hyperoxia. RESULTS: Of the 563 patients eligible for the study, 49 had hyperoxia at treatment initiation for severe infection. The in-hospital all-cause mortality rates of patients with and without hyperoxia were 14 (29.2%) and 90 (17.6%), respectively. Inverse probability weighting analyses with propensity scores revealed the association between hyperoxia and increased in-hospital mortality rate (28.8% vs 18.8%; adjusted OR 1.75 (1.03 to 2.97); p=0.038), adjusting for patient demographics, comorbidities, site of infection, severity of infection, haemodynamic and respiratory status, laboratory data and location of patient at infection development. Acute lung injury developed more frequently in patients with hyperoxia on the following days after infection treatment, whereas sepsis-related mortality was comparable regardless of hyperoxia exposure. CONCLUSION: Hyperoxia with PaO2 ≥300 mm Hg at treatment initiation of severe infection was associated with an increased in-hospital mortality rate in patients requiring intensive care. The amount of oxygen to administer to patients with severe infection should be carefully determined. TRIAL REGISTRATION NUMBER: University Hospital Medical Information Network Clinical Trial Registry (UMIN000027452).

dsRID: in silico identification of dsRNA regions using long-read RNA-seq data.

MOTIVATION: Double-stranded RNAs (dsRNAs) are potent triggers of innate immune responses upon recognition by cytosolic dsRNA sensor proteins. Identification of endogenous dsRNAs helps to better understand the dsRNAome and its relevance to innate immunity related to human diseases. RESULTS: Here, we report dsRID (double-stranded RNA identifier), a machine-learning-based method to predict dsRNA regions in silico, leveraging the power of long-read RNA-sequencing (RNA-seq) and molecular traits of dsRNAs. Using models trained with PacBio long-read RNA-seq data derived from Alzheimer's disease (AD) brain, we show that our approach is highly accurate in predicting dsRNA regions in multiple datasets. Applied to an AD cohort sequenced by the ENCODE consortium, we characterize the global dsRNA profile with potentially distinct expression patterns between AD and controls. Together, we show that dsRID provides an effective approach to capture global dsRNA profiles using long-read RNA-seq data. AVAILABILITY AND IMPLEMENTATION: Software implementation of dsRID, and genomic coordinates of regions predicted by dsRID in all samples are available at the GitHub repository: https://github.com/gxiaolab/dsRID.

Simple parameters to identify patients treatable with early definitive fixation: A nationwide study.

INTRODUCTION: Early appropriate care (EAC) is widely accepted as a safe strategy to perform early definitive fracture fixation, and good clinical outcomes have been reported in selected, multiply injured patients, although the optimal candidate for early definitive fixation (EDF) has not been validated. The aim of this study was to identify simple clinical parameters to help select patients who could undergo EDF. METHODS: Patients with extremity injuries who underwent open reduction and internal fixation were retrospectively identified, using data from the Japan Trauma Data Bank (JTDB). Age, vital signs on hospital presentation, and the injury severity score (ISS) were examined by transforming these variables to binary categories. Patients were divided into categories based on these variables, and in-hospital mortality was compared between patients treated with EDF (EDF group) and those treated without EDF (non-EDF group) in each category. RESULTS: Of the 12,735 patients who were eligible for the analyses, 3706 (29.1 %) were managed with EDF. In-hospital mortality was significantly higher in the EDF group than in the non-EDF group among patients with a low Glasgow Coma Scale (GCS) score (<13), low systolic blood pressure (sBP) (<90 mmHg), and ISS≥15, whereas in-hospital mortality was comparable between the EDF and non-EDF groups among patients with GCS scores ≥13, sBP ≥90 mmHg, and ISS <15. DISCUSSION: In this large nationwide database of trauma patients, EDF was performed without affecting mortality in patients with GCS scores ≥13 and sBP ≥90 mmHg on hospital presentation, as well as ISS <15. These parameters might be useful as screening tools to select the candidates who could be treated with EDF safely.

Potential harms of emergency department thoracotomy in patients with persistent cardiac arrest following trauma: a nationwide observational study.

Emergency department thoracotomy (EDT) was incorporated into traumatic out-of-hospital cardiac arrest (t-OHCA) resuscitation. Although current guidelines recommend EDT with survival predictors, futility following EDT has been demonstrated and the potential risks have not been thoroughly investigated. This study aimed to elucidate the benefits and harms of EDT for persistent cardiac arrest following injury until hospital arrival. This retrospective cohort study used a nationwide trauma registry (2019-2021) and included adult patients with t-OHCA both at the scene and on hospital arrival. Survival to discharge, hemostatic procedure frequency, and transfusion amount were compared between patients treated with and without EDT. Inverse probability weighting using a propensity score was conducted to adjust age, sex, comorbidities, mechanism of injury, prehospital resuscitative procedure, prehospital physician presence, presence of signs of life, degree of thoracic injury, transportation time, and institutional characteristics. Among 1289 patients, 374 underwent EDT. The longest transportation time for survivors was 8 and 23 min in patients with and without EDT, respectively. EDT was associated with lower survival to discharge (4/374 [1.1%] vs. 22/915 [2.4%]; adjusted odds ratio [OR], 0.43 [95% CI 0.22-0.84]; p = 0.011), although patients with EDT underwent more frequent hemostatic surgeries (46.0% vs. 5.0%; adjusted OR, 16.39 [95% CI 12.50-21.74]) and received a higher amount of transfusion. Subgroup analyses revealed no association between EDT and lower survival in patients with severe chest injuries (1.0% vs. 1.4%; adjusted OR, 0.72 [95% CI 0.28-1.84]). EDT was associated with lower survival till discharge in trauma patients with persistent cardiac arrests after adjusting for various patient backgrounds, including known indications for EDT. The idea that EDT is the last resort for t-OHCA should be reconsidered and EDT indications need to be deliberately determined.Trial registration This study is retrospectively registered at University Hospital Medical Information Network (UMIN ID: UMIN000050840).

Early restricted oxygen therapy after resuscitation from cardiac arrest (ER-OXYTRAC): protocol for a stepped-wedge cluster randomised controlled trial.

INTRODUCTION: Cardiac arrest is a critical condition, and patients often experience postcardiac arrest syndrome (PCAS) even after the return of spontaneous circulation (ROSC). Administering a restricted amount of oxygen in the early phase after ROSC has been suggested as a potential therapy for PCAS; however, the optimal target for arterial partial pressure of oxygen or peripheral oxygen saturation (SpO2) to safely and effectively reduce oxygen remains unclear. Therefore, we aimed to validate the efficacy of restricted oxygen treatment with 94%-95% of the target SpO2 during the initial 12 hours after ROSC for patients with PCAS. METHODS AND ANALYSIS: ER-OXYTRAC (early restricted oxygen therapy after resuscitation from cardiac arrest) is a nationwide, multicentre, pragmatic, single-blind, stepped-wedge cluster randomised controlled trial targeting cases of non-traumatic cardiac arrest. This study includes adult patients with out-of-hospital or in-hospital cardiac arrest who achieved ROSC in 39 tertiary centres across Japan, with a target sample size of 1000. Patients whose circulation has returned before hospital arrival and those with cardiac arrest due to intracranial disease or intoxication are excluded. Study participants are assigned to either the restricted oxygen (titration of a fraction of inspired oxygen with 94%-95% of the target SpO2) or the control (98%-100% of the target SpO2) group based on cluster randomisation per institution. The trial intervention continues until 12 hours after ROSC. Other treatments for PCAS, including oxygen administration later than 12 hours, can be determined by the treating physicians. The primary outcome is favourable neurological function, defined as cerebral performance category 1-2 at 90 days after ROSC, to be compared using an intention-to-treat analysis. ETHICS AND DISSEMINATION: This study has been approved by the Institutional Review Board at Keio University School of Medicine (approval number: 20211106). Written informed consent will be obtained from all participants or their legal representatives. Results will be disseminated via publications and presentations. TRIAL REGISTRATION NUMBER: UMIN Clinical Trials Registry (UMIN000046914).

Association between longitudinal changes in striatal dopamine transporter uptake and clinical features of dementia with Lewy bodies.

BACKGROUND: It is widely known that there is low striatal 123 I-2ß-Carbomethoxy-3ß-(4-iodophenyl)-N-(3- fluoropropyl) nortropane (123 I-FP-CIT) dopamine transporter single photon emission tomography (DaT-SPECT) uptake in patients with dementia with Lewy bodies (DLB). No studies to date have analyzed the association between longitudinal changes of clinical features and DaT uptake in patients with Parkinson syndrome, particularly those with DLB. The aim of this study was to investigate the association between the longitudinal changes in DaT uptake and the severity of parkinsonism and cognitive function in DLB patients. METHODS: A total of 35 outpatients with probable DLB who underwent DaT-SPECT twice (at the initial examination and the follow-up period) in the Memory Disorder Clinic at the Department of Geriatric Medicine, Tokyo Medical University, were enrolled in this study between April 2014 and September 2020. The correlation between annual changes in DaT uptake and clinical features (cognitive function decline and parkinsonism) of the patients was analyzed. RESULTS: A significant correlation was detected between annual changes in parkinsonism symptom severity and DaT uptake in the left posterior putamen (r = -0.39, P = 0.03), and between Mini-Mental State Examination scores and DaT uptake in all regions except the right posterior putamen (P < 0.05) in patients with DLB. CONCLUSIONS: Our results suggested that the pathway from the ventrolateral tier of the substantia nigra to the putamen might be more crucial for motor function than other pathways, not only in Parkinson's disease but also in DLB.

Optimal tentative abdominal closure for open abdomen: a multicenter retrospective observational study (OPTITAC study).

BACKGROUND: Primary fascia closure is often difficult following an open abdomen (OA). While negative-pressure wound therapy (NPWT) is recommended to enhance successful primary fascia closure, the optimal methods and degree of negative pressure remain unclear. This study aimed to elucidate optimal methods of NPWT as a tentative abdominal closure for OA to achieve primary abdominal fascia closure. MATERIALS AND METHODS: A multicenter, retrospective, cohort study of adults who survived OA greater than 48 h was conducted in 12 institutions between 2010 and 2022. The achievement of primary fascia closure and incidence of enteroatmospheric fistula were examined based on methods (homemade, superficial NPWT kit, or open-abdomen kit) or degrees of negative pressure (<50, 50-100, or >100 mmHg). A generalized estimating equation was used to adjust for age, BMI, comorbidities, etiology for laparotomy requiring OA, vital signs, transfusion, severity of critical illness, and institutional characteristics. RESULTS: Of the 279 included patients, 252 achieved primary fascia closure. A higher degree of negative pressure (>100 mmHg) was associated with fewer primary fascia closures than less than 50 mmHg [OR, 0.18 (95% CI: 0.50-0.69), P =0.012] and with more frequent enteroatmospheric fistula [OR, 13.83 (95% CI: 2.30-82.93)]. The methods of NPWT were not associated with successful primary fascia closure. However, the use of the open-abdomen kit was related to a lower incidence of enteroatmospheric fistula [OR, 0.02 (95% CI: 0.00-0.50)]. CONCLUSION: High negative pressure (>100 mmHg) should be avoided in NPWT during tentative abdominal closure for OA.

Healthcare costs for hospitalized COVID-19 patients in a Japanese university hospital: a cross-sectional study.

BACKGROUND: A health-economic evaluation related to COVID-19 is urgently needed to allocate healthcare resources efficiently; however, relevant medical cost data in Japan concerning COVID-19 are scarce. METHODS: This cross-sectional study investigated the healthcare cost for hospitalized COVID-19 patients in 2021 at Keio University Hospital. We calculated the healthcare costs during hospitalization using hospital claims data and investigated the variables significantly related to the healthcare cost with multivariable analysis. RESULTS: The median healthcare cost per patient for the analyzed 330 patients was Japanese yen (JPY) 1,304,431 (US dollars ~ 11,871) (interquartile range: JPY 968,349-1,954,093), and the median length of stay was 10 days. The median healthcare cost was JPY 798,810 for mild cases; JPY 1,113,680 for moderate I cases; JPY 1,643,909 for moderate II cases; and JPY 6,210,607 for severe cases. Healthcare costs increased by 4.0% for each additional day of hospitalization; 1.26 times for moderate I cases, 1.64 times for moderate II cases, and 1.84 times for severe cases compared to mild cases; and 2.05 times for cases involving ICU stay compared to those not staying in ICU. CONCLUSIONS: We clarified the healthcare cost for hospitalized COVID-19 patients by severity in a Japanese university hospital. These costs contribute as inputs for forthcoming health economic evaluations for strategies for preventing and treating COVID-19.