Long-term in vivo monitoring of injury induced brain
regeneration of the adult zebrafish by using spectral
domain optical coherence tomography
Jian Zhang (张 建), Zhi-Wei Zhang (张志伟), Wei Ge (葛 伟), and Zhen Yuan (袁 振)*
Faculty of Health Sciences, University of Macau, Macau SAR, China
*Corresponding author: zhenyuan@umac.mo
Received April 4, 2016; accepted June 14, 2016; posted online July 8, 2016
Brain regenerative studies require precise visualization of the morphological structures. However, few imaging
methods can effectively detect the adult zebrafish brain in real time with high resolution and good penetration
depth. Long-term in vivo monitoring of brain injuries and brain regeneration on adult zebrafish is achieved in this
study by using 1325 nm spectral-domain optical coherence tomography (SD-OCT). The SD-OCT is able to
noninvasively visualize the skull injury and brain lesion of adult zebrafish. Valuable phenomenon such as
the fractured skull, swollen brain tissues, and part of the brain regeneration process can be conducted based
on the SD-OCT images at different time points during a period of 43 days.
OCIS codes: 170.0170, 170.4500, 170.1420.
doi: 10.3788/COL201614.081702.
Regeneration is widely recognized as one of the most
intriguing and fascinating topics in the biomedical
fields
[1,2]
. Revealing the nature of regeneration in organ-
isms opens a new avenue for the longstanding question of
regeneration mechanisms, which provides assistance for
devising therapeutic applications for humans. Recently,
a rapidly growing interest in the zebrafish, which serve
as a model organism of vertebrate biology for the investi-
gation of regeneration, has appeared largely due to its
pronounced regenerative capacity in several organs and
tissues including the muscle, heart, pancreas, liver, skin,
pigment cells, fins, and the central nervous system
(CNS)
[2–4]
. More importantly, the adult zebrafish has man-
ifested its unique ability during recovery from CNS inju-
ries by generating new neurons to replenish the lost neural
tissues
[5,6]
.
In vivo imaging is a powerful tool for studying brain re-
generation in CNS, which has the ability to characterize
the damaged tissue, measure the safety and efficacy of
therapy, and monitor the regeneration process. In particu-
lar, the neuroimaging techniques including magnetic res-
onance microscopy and ultrasound microscopy enable us
to noninvasively measure the changes of the brain struc-
tures and functions based on the adult zebrafish model
[7,8]
.
However, the imaging resolution (50–100 μm) and con-
trast as well as the imaging speed from the two methods
mentioned above are insufficient for identifying the vol-
ume changes of brain structures in real time. In contrast,
optical imaging methods including confocal and two-
photon microscopy have shown their merits in capturing
the structures of the zebrafish brain at embryonic stages
with a high resolution (0.5–5 μm)
[9–12]
. However, the zebra-
fish brains will lose their transparency after their first two-
weeks of development, and most available optical imaging
methods will not be able to effectively image the zebrafish
brain at the adult stage. As such, it is crucial to develop
and use new optical imaging techniques which can achieve
high-resolution imaging of the adult zebrafish brain
with an excellent penetration depth and video-rate imag-
ing speed.
Optical coherence tomography (OCT) is a robust and
attractive imaging method that uses scattering light to re-
construct the three-dimensional (3D) images of biological
tissues with a micrometer resolution
[13–15]
. The most recent
advance in OCT technologies is the development of the
spectral-domain (SD) OCT imaging system, which has
shown promise in the biological and biomedical imaging
field
[16–19]
. Compared to other approaches used for imaging
the zebrafish brain, OCT has competitive advantages in
that both the im age quality and the imaging depth is
effective for providing detailed 3D information on the
micro-structure of an intact adult zebrafish brain. In this
study, a long-range SD-OCT system was employed for the
long-term monitoring of brain tissue regeneration using an
adult zebrafish model of brain injury. It is suggested t hat
the long-range SD-OCT system used in this study is able
to provide high-resolution and real-time monitoring of
brain regeneration at different stages in a mechanically
damaged brain of an adult zebrafish.
Figure
1 displays the standard Thorlabs SD-OCT
(TELESTO-II-1325LR) imaging system that was utilized
for the present work. This SD-OCT system applies a single
super luminescent diode (SLD) with a 1325 nm central
wavelength and an over 100 nm spectral bandwidth as
the light source. The spectrometer design is optimized
for the light source of this system, and our SD-OCT im-
aging setup can achieve an axial resolution of 12 μm and a
lateral resolution of 13 μm in the air. The imaging depth of
this system can achieve around 6 mm for the agar phan-
tom and about 2 mm for tissues such as chicken breast
[20]
.
COL 14(8), 081702(2016) CHINESE OPTICS LETTERS August 10, 2016
1671-7694/2016/081702(4) 081702-1 © 2016 Chinese Optics Letters