Epidermal growth factor receptor inhibitor ameliorates excessive astrogliosis and improves the regeneration microenvironment and functional recovery in adult rats following spinal cord injury.
BACKGROUND
Astrogliosis is a common phenomenon after spinal cord injury (SCI). Although this process exerts positive effects on axonal regeneration, excessive astrogliosis imparts negative effects on neuronal repair and recovery. Epidermal growth factor receptor (EGFR) pathway is critical to the regulation of reactive astrogliosis, and therefore is a potential target of therapeutics to better control the response. In this report, we aim to investigate whether blocking EGFR signaling using an EGFR tyrosine kinase specific inhibitor can attenuate reactive astrogliosis and promote functional recovery after a traumatic SCI.


METHODS
The astrocyte scratch injury model in vitro and the weight-drop SCI model in vivo were used as model systems. PD168393 was used to inhibit EGFR signaling activation. Astrocytic activation and phosphorylated EGFR (pEGFR) were observed after immunofluorescence staining and Western blot analysis. The rate of proliferation was determined by immunofluorescence detection of BrdU-incorporating cells located next to the wound. The levels of TNF-α, iNOS, COX-2 and IL-1β in the culture medium under different conditions were assayed by ELISA. Western blot was performed to semi-quantify the expression of EGFR/pEGFR, glial fibrillary acid protein (GFAP) and chondroitin sulfate proteoglycans (CSPGs). Myelin was stained by Luxol Fast Blue Staining. Cresyl violet eosin staining was performed to analyze the lesion cavity volume and neuronal survival following injury. Finally, functional scoring and residual urine recording were performed to show the rats' recovery.


RESULTS
EGFR phosphorylation was found to parallel astrocyte activation, and EGFR inhibitor PD168393 potently inhibited scratch-induced reactive astrogliosis and proinflammatory cytokine/mediator secretion of reactive astrocytes in vitro. Moreover, local administration of PD168393 in the injured area suppressed CSPGs production and glial scar formation, and resulted in reduced demyelination and neuronal loss, which correlated with remarkable hindlimb motor function and bladder improvement in SCI rats.


CONCLUSIONS
The specific EGFR inhibitor PD168393 can ameliorate excessive reactive astrogliosis and facilitate a more favorable environment for axonal regeneration after SCI. As such, EGFR inhibitor may be a promising therapeutic intervention in CNS injury.
Department of Neurology, Wuxi People's Hospital of Nanjing Medical University, Wuxi, PR China. lizaiwang123@gmail.com.
Zai-Wang
ZW
Li
Ji-Jun
JJ
Li
Lan
L
Wang
Jian-Ping
JP
Zhang
Jing-Jing
JJ
Wu
Xu-Qiang
XQ
Mao
Guo-Feng
GF
Shi
Qian
Q
Wang
Feng
F
Wang
Jian
J
Zou
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004195:Disease Models, Animal; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005911:Gliosis / Q000188:drug therapy* / Q000209:etiology; D007674:Kidney Diseases / Q000188:drug therapy / Q000209:etiology; D010766:Phosphorylation / Q000187:drug effects; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000187:drug effects*; D012038:Regeneration / Q000187:drug effects*; D013119:Spinal Cord Injuries / Q000150:complications*
D005904:Glial Fibrillary Acidic Protein; C509204:PD168393; D011799:Quinazolines; D066246:ErbB Receptors