Kosuke Yamaka

Dr. Kosuke Yamaka

orcid

Research Focus & Metrics

Academic Career Length

3Years (2024-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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Verified
Journal Article
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TNTakayuki Nimura
Takayuki Nimura
DADaiki Aomura
Daiki Aomura
MHMakoto Harada
Makoto Harada
AYAkinori Yamaguchi
Akinori Yamaguchi
KYKosuke Yamaka
Kosuke Yamaka
Yuji KamijoYuji Kamijo
Yuji Kamijo
Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) can occasionally trigger thrombotic microangiopathy (TMA). Cytomegalovirus (CMV) may be reactivated during intensive immunosuppressive therapy for AAV and cause TMA. Therefore, we aimed to evaluate the clinical features of and the association between vascular endothelial injury markers and TMA due to CMV in patients with AAV. A 61-year-old female was diagnosed with AAV and severe kidney injury. Immunosuppressive therapy gradually improved her symptoms and laboratory findings. However, 2 weeks after induction therapy initiation, she exhibited altered consciousness, a significant decrease in platelet count, and hemolytic anemia, resulting in a TMA diagnosis. Plasma exchange did not improve TMA findings and routine screening test revealed CMV infection. Ganciclovir injection improved the infection and TMA findings. Consequently, we diagnosed her with CMV-induced TMA. Both AAV and CMV may induce severe vascular endothelial injury, potentially leading to TMA development. CMV-induced TMA should be considered when TMA develops during induction therapy against AAV. Moreover, of the three serum markers of vascular injury—serum sulfatides, soluble thrombomodulin, and pentraxin 3—serum sulfatides may be associated with the development of TMA, and a high level of soluble thrombomodulin may be associated with the development of CMV viremia during the clinical course of AAV.

9 August 2025 in Hepatology Research
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Journal Article
Open access
HKHiroyuki Kobayashi
Hiroyuki Kobayashi
MOMasao Ota
Masao Ota
KMKatsuhiko Matsuzaki
Katsuhiko Matsuzaki
HYHiromi Yamada
Hiromi Yamada
DADaiki Aomura
Daiki Aomura
SJSatoru Joshita
Satoru Joshita
Background and Aims: Hepatitis C virus (HCV) infection remains a global public health concern, with many carriers remaining undiagnosed because of its asymptomatic nature. Although Japan was previously considered to be on track for national HCV elimination by 2030, recent global modeling studies and updated elimination dashboards indicate that Japan is currently not on track. This underscores the importance of locally coordinated efforts to detect residual cases. Micro‐elimination has recently emerged as a pragmatic and scalable approach by targeting defined populations or geographic areas. The Nagawa Project sought to identify HCV positive individuals through community‐wide screening and directing viremic cases to appropriate direct‐acting antiviral (DAA) therapy. The present study describes the implementation and outcomes of this cohort‐based HCV micro‐elimination strategy. Methods: All 5027 adult residents of Nagawa town, Japan, aged ≥ 20 years were prospectively targeted for HCV antibody testing through routine health check‐ups, outpatient visits, and mailed invitations between June 2021 and March 2024. HCV Antibody positive individuals underwent additional HCV core antigen testing to confirm viremia. Results: A total of 3121 residents (62.1%) underwent HCV antibody testing. Testing rates were significantly higher in early‐stage elderly (65–74 years; 73.7%) residents than in both adult (20–64 years; 54.5%) ( p < 0.001) and late‐stage elderly (≥ 75 years; 66.7%) ( p < 0.001) residents. Twenty‐eight individuals (0.897%) were HCV antibody positive, with three cases (0.096%) confirmed as viremic. Antibody positivity was significantly higher in late‐stage elderly residents (1.91%; p < 0.001 vs. adult and p = 0.031 vs. early‐stage elderly residents). Two viremic individuals received DAA therapy and achieved a sustained virological response. After adjusting for age and sex by propensity score matching, no significant difference in overall survival was observed between HCV antibody positive and negative individuals. Conclusion: The Nagawa Project illustrates the success of a locally coordinated HCV micro‐elimination approach. It offers a practical framework for identifying and managing residual HCV infections, contributing to progress toward Japan's alignment with the World Health Organization's 2030 HCV elimination goals.

16 June 2025 in Frontiers in Immunology
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Journal Article
Open access
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KYKosuke Yamaka
Kosuke Yamaka
DADaiki Aomura
Daiki Aomura
MHMakoto Harada
Makoto Harada
TNTakero Nakajima
Takero Nakajima
TNTakayuki Nimura
Takayuki Nimura
Yuji KamijoYuji Kamijo
Yuji Kamijo
Introduction: Lupus nephritis (LN) is a severe complication of systemic lupus erythematosus, often leading to end-stage kidney disease. Serum sulfatide levels are linked to severe kidney vasculitis. This study aimed to assess serum sulfatide levels as a marker for classifying and evaluating disease activity in LN.Methods: We conducted a retrospective study of patients admitted to our hospital between 2003 and 2022. Serum sulfatide levels were compared between LN patients and controls as well as across LN classes based on the International Society of Nephrology/Renal Pathology Society classification. We also analyzed the association between sulfatide levels and active lesions, the Activity Index, and its components.Results: Serum sulfatide levels were significantly lower in LN patients than in controls (6.90 ± 2.22 vs. 8.34 ± 1.68, P = 0.007). Levels across LN classes were as follows: 9.41 nmol/mL in Class I, 8.21 ± 1.68 nmol/mL in Class II, 7.33 ± 2.25 nmol/mL in Class III, 6.14 ± 1.63 nmol/mL in Class IV, and 7.89 ± 2.12 nmol/mL in Class V, with Class IV having the lowest levels. Serum sulfatides were significantly lower in patients with active lesions (6.38 ± 1.81 vs. 8.23 ± 2.55, P = 0.006) and negatively correlated with the Activity Index (r = −0.51, P < 0.001) and pathological components such as endocapillary hypercellularity, neutrophils/karyorrhexis, and interstitial inflammation (P < 0.001).Conclusions: Serum sulfatide levels were significantly lower in LN patients than in controls and strongly correlated with active lesions and the Activity Index. These findings suggest sulfatide levels as a useful marker for assessing LN disease activity.

Verified
Journal Article
Open access
PDF file
MHMakoto Harada
Makoto Harada
SAShotaro Aso
Shotaro Aso
TNTakayuki Nimura
Takayuki Nimura
KYKosuke Yamaka
Kosuke Yamaka
DADaiki Aomura
Daiki Aomura
Yuji KamijoYuji Kamijo
Yuji Kamijo
Background/Objectives: Personalized treatment approaches are increasingly recognized as essential in the management of anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV), given the substantial heterogeneity in disease severity and patient characteristics. Kidney biopsy has the potential to serve as an effective tool for personalized treatment decision-making in patients with AAV. This study aimed to investigate the association of kidney biopsy with intensive immunosuppressive therapy and clinical outcomes in patients with AAV and kidney impairment. Methods: In this retrospective study, propensity score overlap weighting was applied to compare intensive immunosuppressive therapy and clinical outcomes (ESKD, death, combined ESKD and death, and infectious complications) between patients with AAV who underwent kidney biopsy and those who did not. Results: Out of 74 patients with AAV, 38 underwent kidney biopsy. Overlap weight analysis revealed that kidney biopsy was significantly associated with intensive immunosuppressive therapy (risk difference [RD], 28.9%; 95% confidence interval [CI], 0.017 to 0.562). Kidney biopsy was not associated with combined ESKD and death (RD, −0.2%; 95% CI, −0.302 to 0.298), death (RD, −3.8%; 95% CI, −0.264 to 0.189), ESKD (RD, −7.3%; 95% CI, −0.353 to 0.207), and infectious complications (RD, −25.9%; 95% CI, −0.537 to 0.020). Conclusions: In this observational cohort, kidney biopsy was associated with intensification of immunosuppressive therapy. However, after adjustment using overlap weighting, no statistically significant difference in clinical outcomes was detected, and the reduced effective sample size limited statistical power. These findings should be interpreted cautiously, as causal inference regarding the prognostic impact of kidney biopsy remains limited.