Neural Regeneration Research ›› 2016, Vol. 11 ›› Issue (4): 578-590.doi: 10.4103/1673-5374.180742

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Cell proliferation and apoptosis in optic nerve and brain integration centers of adult trout Oncorhynchus mykiss after optic nerve injury

Evgeniya V. Pushchina1, *, Sachin Shukla2, Anatoly A. Varaksin1, Dmitry K. Obukhov3   

  1. 1 Laboratory of Cytophysiology, A.V. Zhirmunsky Institute of Marine Biology Far Eastern Branch of Russian Academy of Sciences, Vladivostok, Russia
    2 Prof. Brien Holden Eye Research Centre, L.V. Prasad Eye Institute, Hyderabad, India
    3 St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, Russia
  • Received:2015-12-22 Online:2016-04-30 Published:2016-04-30
  • Contact: Evgeniya V. Pushchina, D.Sc., Ph.D., puschina@mail.ru.
  • Supported by:

    This work was supported by a grant from President of Russian Federation (No. MD-4318.2015.4), a grant from Program for Basic Research of the Far East Branch of the Russian Academy of Sciences 2015–2017 (No. 15-I-6-116, section III), and DST-INSPIRE Faculty Grant (No. IFA14-LSBM-104) from the Department of Science and Technology (DST), Government of India.

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Abstract:

Fishes have remarkable ability to effectively rebuild the structure of nerve cells and nerve fibers after central
nervous system injury. However, the underlying mechanism is poorly understood. In order to address this
issue, we investigated the proliferation and apoptosis of cells in contralateral and ipsilateral optic nerves,
after stab wound injury to the eye of an adult trout Oncorhynchus mykiss. Heterogenous population of
proliferating cells was investigated at 1 week after injury. TUNEL labeling gave a qualitative and quantitative
assessment of apoptosis in the cells of optic nerve of trout 2 days after injury. After optic nerve injury,
apoptotic response was investigated, and mass patterns of cell migration were found. The maximal concentration
of apoptotic bodies was detected in the areas of mass clumps of cells. It is probably indicative of
massive cell death in the area of high phagocytic activity of macrophages/microglia. At 1 week after optic
nerve injury, we observed nerve cell proliferation in the trout brain integration centers: the cerebellum and
the optic tectum. In the optic tectum, proliferating cell nuclear antigen (PCNA)-immunopositive radial
glia-like cells were identified. Proliferative activity of nerve cells was detected in the dorsal proliferative
(matrix) area of the cerebellum and in parenchymal cells of the molecular and granular layers whereas local
clusters of undifferentiated cells which formed neurogenic niches were observed in both the optic tectum
and cerebellum after optic nerve injury. In vitro analysis of brain cells of trout showed that suspension cells
compared with monolayer cells retain higher proliferative activity, as evidenced by PCNA immunolabeling.
Phase contrast observation showed mitosis in individual cells and the formation of neurospheres which
gradually increased during 1–4 days of culture. The present findings suggest that trout can be used as a
novel model for studying neuronal regeneration.

Key words: nerve regeneration, proliferation, apoptosis, optic nerve, brain, radial glia cells, neurogenic niches, neurospheres, neural regeneration