Exp Neurobiol 2020; 29(6): 417-424
Published online December 7, 2020
© The Korean Society for Brain and Neural Sciences
Hwan-Ki Kim1, Dong-won Lee1, Eunmi Kim1, Inyoung Jeong1, Suhyun Kim1*, Bum-Joon Kim2* and Hae-Chul Park1*
1Department of Biomedical Sciences, College of Medicine, Korea University,
2Department of Neurosurgery, Korea University Ansan Hospital, Ansan 15355, Korea
Correspondence to: *To whom correspondence should be addressed.
Hae-Chul Park, TEL: 82-31-412-6713, FAX: 82-31-412-6729
Bum-Joon Kim, TEL: 82-31-412-5050, FAX: 82-31-412-5054
Suhyun Kim, TEL: 82-31-412-6725, FAX: 82-31-412-6729
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The myelination of axons in the vertebrate nervous system through oligodendrocytes promotes efficient axonal conduction, which is required for the normal function of neurons. The central nervous system (CNS) can regenerate damaged myelin sheaths through the process of remyelination, but the failure of remyelination causes neurological disorders such as multiple sclerosis. In mammals, parenchymal oligodendrocyte progenitor cells (OPCs) are known to be the principal cell type responsible for remyelination in demyelinating diseases and traumatic injuries to the adult CNS. However, growing evidence suggests that neural stem cells (NSCs) are implicated in remyelination in animal models of demyelination. We have previously shown that
Oligodendrocytes are glial cells that myelinate axons in the central nervous system (CNS) to provide electrical insulation for axonal conduction. Oligodendrocytes also play a crucial role in promoting neuronal survival by providing metabolic support, including the supply of lactate to neurons . Various factors including genetics, immune system dysfunction, and traumatic injury can induce demyelination, which can be restored through oligodendrocytes. However, persistent demyelination and the failure of remyelination may cause several neurological disorders, such as multiple sclerosis .
Severe traumatic injury to the adult mammalian CNS has catastrophic effects, after which significant regeneration does not occur. In contrast, adult zebrafish possess a remarkable ability to regenerate neurons in the injured CNS. Previous studies have shown that radial glia (RG) detected using markers such as BLBP, GFAP, and S100B exist in the ventricular zone (VZ) and function as neural precursors to generate neurons in the telencephalon of adult zebrafish [3-7]. Injury of the telencephalon induces the proliferation of RGs in the VZ of the injured hemisphere following active neurogenesis for neuronal regeneration [8-11]. In addition, lineage-tracing studies of RG using retroviral and lentiviral vectors and the Cre-loxP system in the normal and injured telencephalon, respectively, have provided direct evidence that RG can act as neural stem cells to generate new neurons in adult zebrafish [8, 12]. However, the cellular and molecular mechanisms underlying the regeneration of oligodendrocytes in the injured brain are largely unknown.
We previously reported that regulatory DNA from the
The following transgenic lines were used:
For LY-411575 treatment, the following stock solution was made and stored at -20°C: 10 mM LY-411575 (medchemexpress, HY50752) in dimethyl sulfoxide (DMSO); this was added to the swimming water at a temperature of 28°C and at a final concentration of 10 μM for 4 days. The control fish were placed in water with 0.1% DMSO.
Adult male fish were 6~10 months old. Fish were anesthetized using Tricaine (Sigma). An insulin syringe (31 gauge, outer diameter: 250 μm) was pushed ~5~7 mm deep along the rostrocaudal body axis until it reached the caudal part of the telencephalon .
To label newborn cells in the adult zebrafish telencephalon, adult zebrafish were placed in water containing 10 mM 5-bromo-2’-deoxyuridine (BrdU, Roche Holding AG, Basel, Switzerland, 10280879001) for 4 days prior to being released into fresh water.
Adult zebrafish brains were fixed in 4% paraformaldehyde prior to being embedded in 1.5% agar blocks containing 5% sucrose and equilibrated in 30% sucrose solution. The frozen blocks were sliced into 10-μm sections using a cryostat microtome, and the transverse sectioned slices were mounted on glass slides. Subsequently, the zebrafish were processed for immunohistochemistry. The following primary antibodies were used: rabbit anti-BrdU (1:200, Rockland, cat # 600-401-C29, RRID: AB_10893609), chicken anti-GFP (1:200, Abcam, cat # ab6556, RRID: AB_300798), mouse anti-proliferating cell nuclear antigen (PCNA) (1:200, DAKO, cat # M0879, RRID: AB_2313584), rabbit anti-BLBP (1:1,000, Abcam, cat # ab27171, RRID: AB_869739), rabbit anti-S100β (1:200, DAKO, cat # Z031101, RRID: AB_10013383), and mouse anti-GFAP (1:250, ZIRC, cat # Zrf-1, RRID: AB_10013806). For fluorescent detection of antibody labeling, we used Alexa Fluor 488-, 568-, and 647-conjugated secondary antibodies (1:1,000, Molecular Probes).
All results are expressed as mean±standard error of the mean (SEM). Ten micrometer-thick sections of the adult telencephalon were used for the statistical analyses (approximately 10 sections per slide). p-values were determined with GraphPad Prism (GraphPad Software, San Diego, CA, USA) using the Mann–Whitney
Previously, we have shown that
To test the response of
To test the hypothesis that increased proliferation of OPCs and
Previously, Notch signaling has been shown to play a crucial role in adult neurogenesis and injury-induced regeneration of neurons in the zebrafish telencephalon [9, 11]. To study the role of Notch signaling in the injury-induced proliferation of
In this study, we showed
In mammals, although genetic fate-mapping studies have demonstrated that parenchymal OPCs are the principal cell type responsible for oligodendrocyte regeneration in demyelinating diseases in the adult brain [23, 24], NSCs in the subventricular zone (SVZ) also have been shown to have the potential to produce oligodendrocytes after injury [25, 26]. The participation of SVZ-derived progenitors in the remyelination process has been demonstrated in several experimental mouse models of demyelination [27, 28]. Taken together, these data suggest that, like zebrafish,
Moreover, we showed that blocking Notch signaling promotes the proliferation of
This research was supported by the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (NRF-2018R1C1B5086223, NRF-2019R1I1A1A01043985).