Kei Takayama

Kei Takayama

orcid

Research Focus & Metrics

Academic Career Length

15Years (2012-Present)

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

Representative Publications

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1 May 2016 in Free Radical Biology and Medicine
Verified
Journal Article
Closed access
FYFuxiang Ye
Fuxiang Ye
HKHiroki Kaneko
Hiroki Kaneko
YHYumi Hayashi
Yumi Hayashi
KTKei Takayama
Kei Takayama
SHShiang-Jyi Hwang
Shiang-Jyi Hwang
HTHiroko Terasaki
Hiroko Terasaki

11 October 2018 in Scientific Reports
Verified
Journal Article
Open access
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KTKei Takayama
Kei Takayama
HKHiroki Kaneko
Hiroki Kaneko
YIYasuki Ito
Yasuki Ito
KKKeiko Kataoka
Keiko Kataoka
TITakeshi Iwase
Takeshi Iwase
HTHiroko Terasaki
Hiroko Terasaki
The traditional classification of hypertensive retinopathy was based on the Keith–Wagener–Barker (KWB) grading, which is a subjective scaling system, and it is difficult to distinguish between the first and second grades. Retinal and choroidal vasculatures are affected by systemic hypertension, although retinal vasculature changes with age, axial length, intraocular pressure, and retinal diseases. It is necessary to establish a new objective method to assess hypertensive vascular changes. In the present study, we have examined the vasculature of the macular choriocapillaris in order to establish a new objective method to assess hypertensive vascular changes using optical coherence tomography angiography (OCTA). Choriocapillaris vessel density (VD), vessel length, and vessel diameter index in a 3 × 3 mm macular area were measured by OTCA in a total of 567 volunteers (361 healthy subjects and 206 subjects with systemic hypertension) who attended a basic health check-up. Ocular factors, systemic factors, and medications were evaluated. We detected significant differences in normative choriocapillaris vasculature between the left and right eyes in 53 healthy subjects and revealed correlations between age, intraocular pressure, axial length, and choriocapillaris vasculature in 308 healthy subjects. Normative foveal VD was correlated with age only and the efficiency was weak. The analysis of 206 right eyes (KWB grade 0, 159 eyes; grade 1, 35 eyes; and grade 2, 12 eyes) revealed that foveal VD was strongly correlated with KWB grade only (P < 0.001). This is the first report suggesting that OCTA for foveal choriocapillaris measurement by OCTA would might provide the advantage of evaluating be objective method for evaluating the progression of systemic hypertension.

9 January 2015 in Scientific Reports
Verified
Journal Article
Open access
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FYFuxiang Ye
Fuxiang Ye
HKHiroki Kaneko
Hiroki Kaneko
YNYosuke Nagasaka
Yosuke Nagasaka
RIRyo Ijima
Ryo Ijima
KNKae Nakamura
Kae Nakamura
HTHiroko Terasaki
Hiroko Terasaki
Choroidal neovascularization (CNV) is the main pathogenesis of age-related macular degeneration (AMD), which leads to severe vision loss in many aged patients in most advanced country. CNV compromises vision via hemorrhage and retinal detachment on account of pathological neovascularization penetrating the retina. Plasma medicine represents the medical application of ionized gas “plasma” that is typically studied in the field of physical science. Here we examined the therapeutic ability of plasma-activated medium (PAM) to suppress CNV. The effect of PAM on vascularization was assessed on the basis of human retinal endothelial cell (HREC) tube formation. In mice, laser photocoagulation was performed to induce CNV (laser-CNV), followed by intravitreal injection of PAM. N-Acetylcysteine was used to examine the role of reactive oxygen species in PAM-induced CNV suppression. Fundus imaging, retinal histology examination, and electroretinography (ERG) were also performed to evaluate PAM-induced retinal toxicity. Interestingly, HREC tube formation and laser-CNV were both reduced by treatment with PAM. N-acetylcysteine only partly neutralized the PAM-induced reduction in laser-CNV. In addition, PAM injection had no effect on regular retinal vessels, nor did it show retinal toxicity in vivo. Our findings indicate the potential of PAM as a novel therapeutic agent for suppressing CNV.

4 November 2016 in Eye
Verified
Journal Article
Open access
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KTKei Takayama
Kei Takayama
YIY Ito
Y Ito
HKH Kaneko
H Kaneko
KKK Kataoka
K Kataoka
TST Sugita
T Sugita
HTH Terasaki
H Terasaki
To compare optical coherence tomographic angiography (OCTA) and indocyanine green angiography (ICGA) images for detecting polypoidal lesions (PLs) and branching vascular networks (BVNs), and to measure the polypoidal areas (PAs) in patients with polypoidal choroidal vasculopathy (PCV). All patients underwent ICGA, optical coherence tomography (OCT), and OCTA. We compared the detection sensitivity for PL and BVN, as evaluated by the ICGA and OCTA images. Furthermore, PA measured by ICGA was divided into two groups: one in which the area could be measured by OCTA (ICGA+OCTA+) and the other in which the area could not be measured by OCTA (ICGA+OCTA−). Twenty-one consecutive eyes of 21 patients (mean age, 73.8±9.8 years) were included. ICGA detected PL in all eyes (100%), whereas OCTA detected PL in 16 eyes (75.2%); ICGA detected BVN in 15 eyes (71.4%), whereas OCTA detected BVN in 20 eyes (95.2%). The mean PA in ICGA+OCTA+ and ICGA+OCTA− was 0.24±0.04 and 0.14±0.01 mm2, respectively; a significant difference was observed between ICGA+OCTA+ PA and ICGA+OCTA− PA (P<0.0001). In addition, the mean PA in the ICGA+OCTA+ group measured by ICGA and OCTA was 0.24±0.04 was 0.19±0.04 mm2, respectively; these values were significantly different (P=0.0046). OCTA might detect more BVNs and fewer PLs compared with ICGA, and PL detected by OCTA might be smaller than those detected by ICGA.

1 October 2014 in Investigative Ophthalmology & Visual Science
Verified
Journal Article
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RIRyo Ijima
Ryo Ijima
HKHiroki Kaneko
Hiroki Kaneko
FYFuxiang Ye
Fuxiang Ye
YNYosuke Nagasaka
Yosuke Nagasaka
KTKei Takayama
Kei Takayama
HTHiroko Terasaki
Hiroko Terasaki
Purpose.: To examine the effectiveness of interleukin-18 (IL-18) on choroidal neovascularization (CNV) and retinal pigment epithelium (RPE) in humans and mice. Methods.: Serum IL-18 levels in patients with wet and dry AMD who were older than 50 years were measured and compared with those of age-matched controls. In mice, laser photocoagulation was performed in the retina to induce experimental CNV, and CNV volume was measured in eyes injected with recombinant IL-18 (rIL-18) and IL-18 neutralizing antibody (nIL-18Ab) compared with those injected with control. Tube formation assay was performed on human retinal endothelial cells (HREC) with rIL-18 administration in vitro. After subretinal injection of rIL-18, fundus change in the injected eyes was evaluated; active caspase-3 level was measured in the RPE/choroid complex, and tight junction integrity in RPE was visualized by zonula occludens-1 (ZO-1) staining. Results.: Serum IL-18 levels in dry AMD patients were higher than those in control. Mouse rIL-18 or nIL-18Ab did not induce significant change in CNV volume compared with controls or change tube formation in HREC. Subretinal injection of rIL-18 induced retinal degeneration in the mice fundus; ZO-1 staining showed considerably disturbed RPE structure, and active caspase-3 expression was significantly higher after rIL-18 induction. Conclusions.: Interleukin-18 did not show a pro- or antiangiogenic effect on mouse laser-induced CNVs (laser-CNVs), whereas it directly induced RPE cell apoptosis in the mouse eye. Our results suggested that IL-18 is associated with dry AMD, but not with wet AMD.

25 May 2017 in Scientific Reports
Verified
Journal Article
Open access
PDF file
HKHiroki Kaneko
Hiroki Kaneko
KTKei Takayama
Kei Takayama
TATetsu Asami
Tetsu Asami
YIYasuki Ito
Yasuki Ito
TTTaichi Tsunekawa
Taichi Tsunekawa
HTHiroko Terasaki
Hiroko Terasaki
Silicone oil (SO) is an intraocular surgical adjuvant that reduces the surgical complications in refractory retinal diseases, although membrane and cellular proliferation is often seen even in SO-filled eyes. We hypothesised that the fluid in the space between the SO and the retina, named the “sub-silicone oil fluid (SOF)”, enhances these biological responses. We proposed a safe method for SOF extraction. We also analysed inflammatory cytokine expressions and SOF osmotic pressures from eyes with rhegmatogenous retinal detachment (RRD), proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR) and macular hole-associated retinal detachment (MHRD). Interleukin (IL)-10, IL-12p40, IL-6, monocyte chemotactic protein-1, and vascular endothelial growth factor (VEGF) in the SOF with PVR were significantly higher than in those with RRD or MHRD. Fibroblast growth factor-2, IL-10, IL-12p40, IL-8, VEGF, and transforming growth factor beta 1 levels in eyes with exacerbated PDR indicated a significantly higher expression than those with simple PDR. IL-6 and tumour necrosis factor alpha in eyes with exacerbated PVR demonstrated a significantly higher expression than in those with simple PVR. However, there was no difference in SOF osmotic pressure between group of each disease. These studies indicate that disease-specific SOF is a significant reflection of disease status.