OU‐MRU Vol.39 April 2017

Okayama University Medical Research Updates （OU‐MRU）

2017.04 Vol.39

Source: Okayama University (JAPAN), Public Relations and Information Strategy
For immediate release: 20 April 2017
Okayama University research: Successful test of retinal prosthesis implanted in rats
(Okayama, 20 April) Researchers at Okayama University report in the Journal of Artificial
Organs the promising performance of a retinal prosthesis material when implanted in rats.
The material is capable of converting external light stimuli into electric potentials that arepicked up by neurons. The results signify an important step towards curing certain
hereditary eye diseases.
Retinitis pigmentosa is a hereditary retinal disease, causing blindness due to deadphotoreceptor cells but with other retinal neurons being alive. A potential remedy forpatients diagnosed with this disease are prostheses replacing the non‐functioning
photoreceptor cells with artificial sensors, and making use of the functioning of theremaining, living neurons. Now, a team of researchers from Okayama University led by
Toshihiko Matsuo & Tetsuya Uchida has quantitatively tested the response of a promisingtype of prosthesis, when implanted in rats, to external light flashes — a crucial step in thefurther development of retinal prostheses.
The prosthesis tested by the researchers was developed earlier at Okayama University, andis known as Okayama University‐type retinal prosthesis (OURePTM). The main component ofOURePTM is a photoelectric dye: an organic molecule capable of converting light into electric
potentials. Uchida and colleagues attached the dye molecules to a thin film of polyethylene— a safe and stable biocompatible material — and implanted the dye‐coupled film (of size 1mm x 5 mm) subretinally in the eyes of 10 male rats 6 weeks old. Cranial electrodes forregistering potentials were attached 2–3 weeks later. The researchers also implanted plain,polyethylene films in 10 other rats for comparison purposes.
The scientists tested the response of the implanted OURePTM sensors to flashing white light‐
emitting diodes (LEDs) placed on the surface of the rats’ corneas (the transparent front
parts of the eyes) for different background‐light conditions. The experiments were donewith the rats anesthetized, and after appropriate periods of adaptation to dark or light
conditions. Comparisons between results obtained with dye‐coupled films and plain
polyethylene films showed that the former led to visually evoked potentials — confirming
the potential of OURePTM as a retinal prosthesis for treating diseases like retinitis
pigmentosa.
The use of OURePTM poses no toxicity issues and, because of the high density of the dyemolecules on the polyethylene film, offers a high spatial resolution. Regarding tests onhuman eyes, Matsuo and colleagues point out that “a first‐in‐human clinical trial for

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1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530 Japan© OKAYAMA University

OU‐MRU Vol.39 April 2017

OURePTM at Okayama University Hospital ... will be planned in consultation with [Japan’s]
Pharmaceuticals and Medical Devices Agency”.

Background
OURePTM
Okayama University‐type retinal prosthesis (OURePTM), developed at Okayama University, isa material that mimics the function of photoreceptor cells present in mammalian eyes:
phototransduction, the conversion of light into neuron signals triggering biologicalprocesses. The main component of OURePTM are 2‐[2‐[4‐(dibutylamino)phenyl]ethenyl]‐3‐carboxymethylbenzothiazolium bromide molecules, photoelectric dye molecules that canconvert light into electric potentials. These molecules are attached to the surface of a thinpolyethylene film; the resulting dye‐coupled OURePTM film can be used as an implant
replacing non‐functioning photoreceptor cells. OURePTM is a particularly promising
prosthesis in situations — such as for the disease retinitis pigmentosa — where other retinal
neuron cells, sending neuron signals to the brain, are still active.
Competing strategies
Other approaches for remedying dead photoreceptor cells rely on the use of a digital video
camera integrated into glasses worn by the patient. The video images are converted toelectrical signals transmitted to a receiver implanted in the patient’s body, after whichelectric currents are sent out of an array of electrodes implanted around the patient’s retina.
Challenges associated with this type of approach, as e.g. implemented in the Argus IITM
Retinal Prosthesis System (Second Sight, Inc.), include the miniaturization of thecomponents, their biocompatibility, achieving high spatial resolution, and the need for an
external power source. As demonstrated by the team led by Toshihiko Matsuo, the use ofOURePTM overcomes these issues.

CaptionThe main component of Okayama University‐type retinal prosthesis (OURePTM) is aphotoelectric dye molecule, the structure of which is shown. The dye molecules are
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OU‐MRU Vol.39 April 2017attached to a polyethylene film, resulting in a promising retinal implant. Quantitative
testing experiments were done on the response of dye‐coupled (OURePTM) films and plainfilms, implanted in rats, to flashing LED light.

ReferenceAlamusi, Toshihiko Matsuo, Osamu Hosoya & Tetsuya Uchida. Visual evoked potential in RCS
rats with Okayama University‐type retinal prosthesis (OURePTM) implantation. Journal ofArtificial Organs, 08 February, 2017.
DOI:10.1007/s10047‐016‐0943‐4
https://link.springer.com/article/10.1007%2Fs10047‐016‐0943‐4

Reference (Okayama University e‐Bulletin & OU‐MRU) : Associate Professor Matsuo &Uchida’s teame‐Bulletin Vol.8：Photoelectric dye‐coupled thin film as a novel type of retinal prosthesis
OU‐MRU Vol.8：Light‐responsive dye stimulates sight in genetically blind patients

Correspondence to
Associate Professor Toshihiko Matsuo, M.D., Ph.D.
Department of Ophthalmology, Okayama University
Medical School and Graduate School of Medicine,Dentistry, and Pharmaceutical Sciences, 2‐5‐1
Shikata‐cho, Kita‐ku, Okayama 700‐8558, JapanE‐mail: matsuot@cc.okayama‐u.ac.jp
Associate Professor Toshihiko Matsuo &Tetsuya Uchida(L)Further information
Okayama University
1‐1‐1 Tsushima‐naka , Kita‐ku , Okayama 700‐8530, Japan
Public Relations and Information Strategy
E‐mail: www‐adm@adm.okayama‐u.ac.jp
Website: http://www.okayama‐u.ac.jp/index_e.html
Okayama Univ. e‐Bulletin: http://www.okayama‐u.ac.jp/user/kouhou/ebulletin/
Okayama Univ. e‐Bulletin (PDF Issues): http://www.okayama‐u.ac.jp/en/tp/cooperation/ebulletin.html
About Okayama University (You Tube):https://www.youtube.com/watch?v=iDL1coqPRYIOkayama University Image Movie (You Tube):https://www.youtube.com/watch?v=_WnbJVk2elA
https://www.youtube.com/watch?v=KU3hOIXS5kk

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OU‐MRU Vol.39 April 2017Okayama University Medical Research Updates （OU‐MRU）
Vol.1：Innovative non‐invasive ‘liquid biopsy’ method to capture circulating tumor cells
from blood samples for genetic testing
Vol.2：Ensuring a cool recovery from cardiac arrest
Vol.3：Organ regeneration research leaps forward
Vol.4：Cardiac mechanosensitive integrator
Vol.5：Cell injections get to the heart of congenital defects
Vol.6：Fourth key molecule identified in bone development
Vol.7：Anticancer virus solution provides an alternative to surgery
Vol.8：Light‐responsive dye stimulates sight in genetically blind patients
Vol.9：Diabetes drug helps towards immunity against cancer
Vol.10：Enzyme‐inhibitors treat drug‐resistant epilepsy
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Vol.37：Protein dosage compensation mechanism unravelled
Vol.38：Bioengineered tooth restoration in a large mammal

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1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530 Japan© OKAYAMA University

OU‐MRU Vol.39 April 2017

About Okayama University

Okayama University is one of the largest
comprehensive universities in Japan withroots going back to the Medical Training
Place sponsored by the Lord of Okayama
and established in 1870. Now with 1,300
faculty and 14,000 students, the University
offers courses in specialties ranging frommedicine and pharmacy to humanities
and physical sciences.
Okayama University is located in the heartof Japan approximately 3 hours west ofTokyo by Shinkansen.

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