Müller cell activation, proliferation and migration following laser injury.
OBJECTIVE
Müller cells are well known for their critical role in normal retinal structure and function, but their reaction to retinal injury and subsequent role in retinal remodeling is less well characterized. In this study we used a mouse model of retinal laser photocoagulation to examine injury-induced Müller glial reaction, and determine how this reaction was related to injury-induced retinal regeneration and cellular repopulation.


METHODS
Experiments were performed on 3-4-week-old C57BL/6 mice. Retinal laser photocoagulation was used to induce small, circumscribed injuries; these were principally confined to the outer nuclear layer, and surrounded by apparently healthy retinal tissue. Western blotting and immunohistochemical analyses were used to determine the level and location of protein expression. Live cell imaging of green fluorescent protein (GFP)-infected Müller cells (AAV-GFAP-GFP) were used to identify the rate and location of retinal Müller cell nuclear migration.


RESULTS
Upon injury, Müller cells directly at the burn site become reactive, as evidenced by increased expression of the intermediate filament proteins glial fibrillary acidic protein (GFAP) and nestin. These reactive cells re-enter the cell cycle as shown by expression of the markers Cyclin D1 and D3, and their nuclei begin to migrate toward the injury site at a rate of approximately 12 microm/hr. However, unlike other reports, evidence for Müller cell transdifferentiation was not identified in this model.


CONCLUSIONS
Retinal laser photocoagulation is capable of stimulating a significant glial reaction, marked by activation of cell cycle progression and retinal reorganization, but is not capable of stimulating cellular transdifferentiation or neurogenesis.
Tackenberg
Mark A
MA
Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Tucker
Budd A
BA
Swift
Jesse S
JS
Jiang
Caihui
C
Redenti
Stephen
S
Greenberg
Kenneth P
KP
Flannery
John G
JG
Reichenbach
Andreas
A
Young
Michael J
MJ
D000818:Animals; D015153:Blotting, Western; D002056:Burns / Q000473:pathology; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D056743:Cyclin D3; D016213:Cyclins / Q000378:metabolism; D017075:Laser Coagulation; D051379:Mice; D008810:Mice, Inbred C57BL; D012160:Retina / Q000473:pathology*
C534697:Ccnd3 protein, mouse; D018797:Cell Cycle Proteins; D056743:Cyclin D3; D016213:Cyclins