The effects of inflammation on glial fibrillary acidic protein expression in satellite cells of the dorsal root ganglion.
METHODS
After undergoing L5 hemilaminectomy, chromic gut suture was placed onto the DRG and the animals were sacrificed at various time-points.


OBJECTIVE
The purpose of this study was to identify the effects of inflammation on satellite cells (SCs) of the dorsal root ganglion (DRG) by analyzing glial fibrillary acidic protein (GFAP) expression in of the DRG at various time points.


BACKGROUND
SCs are neuroglial cells that closely interact with nerve cells of the DRG. The role of SC remains unknown GFAP expression increases in response to CNS injury. Loss of GFAP has impaired Schwann cell proliferation and delayed nerve regeneration after injury.


METHODS
Sixty rats underwent a left L5 hemilaminectomy. In Group I, a chromic-gut suture was place topically on the DRG (n = 30), Group II was the sham surgery group (n = 30). DRGs were harvested at 6, 24, 48, 72 hours, and 7 days after surgery. In Group III, 6 control rats were killed and their bilateral L5 DRG harvested. The harvested DRG were analyzed using light microscopy for SC immunoreactivity, using GFAP, HIS-36, TNF-alpha, IL-1alpha, IL-1beta, IL-6 monoclonal antibodies.


RESULTS
One hundred thirty-two DRGs were harvested for analysis. Naïve controls and neurons did not express GFAP. The SC sheath expressed GFAP as early as 6 hours postchromic gut application. In Group I, GFAP expression steadily increased after chromic-gut application with 100% of SC soma and SC sheaths being GFAP positive at 7 days. The contralateral DRG demonstrated delayed GFAP expression, with 83% of SC soma and SC sheaths were GFAP positive at 7 days. In Group II, 89% of sacs expressed GFAP by 7 compared to 79% in the contralateral undisturbed DRG.


CONCLUSIONS
Under physiologic conditions, the expression of GFAP by SCs is undetectable. As the inflammatory process develops, GFAP expression steadily increases with 100% of SCs being GFAP immunoreactive 7 days after chromic gut application. These data suggest that SCs are the primary source of GFAP in the DRG. We hypothesize that SC play an important role in the response to early inflammatory injury.
Siemionow
Krzysztof
K
Department of Orthopedic Surgery, Cleveland Clinic, Cleveland, OH, USA.
Klimczak
Aleksandra
A
Brzezicki
Grzegorz
G
Siemionow
Maria
M
McLain
Robert F
RF
D000818:Animals; D005727:Ganglia, Spinal / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis* / Q000378:metabolism*; D007150:Immunohistochemistry; D007249:Inflammation / Q000503:physiopathology*; D053583:Interleukin-1beta / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D007796:Laminectomy; D008159:Lumbar Vertebrae / Q000601:surgery; D051381:Rats; D011917:Rats, Inbred Lew; D027161:Satellite Cells, Perineuronal; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D005904:Glial Fibrillary Acidic Protein; D053583:Interleukin-1beta; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha