[Pax7 and depletion of satellite cell pool in prolonged denervated skeletal muscles of adult rats].
OBJECTIVE
To analyze the expression changes of Pax7 and MyoD in satellite cells of denervated skeletal muscle at the mRNA and protein level, and to explore the pathway concerning with denervation and regeneration of skeletal muscle.


METHODS
Nine male SD rats of 2 months old, weighing 180-200 g were selected. The right gastrocnemius muscle was made denervation model as experimental sides, and the same operation was performed in the left sides as control. The immunofluorescence analysis was done for detecting the protein expressions of Pax7 and MyoD in muscles denervated 3, 7 and 21 days after operation. The RT-PCR analysis was used to explore the mRNA expression of MyoD and Pax7 in extracted tissues from denervated muscles.


RESULTS
Nine rats survived after operation, with limited motion of right hind limbs, and normal motion of left limbs. The result of immunofluorescence with the polyclonal antibody against MyoD and the monoclonal antibody against Pax7 showed that the number of MyoD positive cells in prolonged denervated muscles (experimental sides) increased gradually, and reached the peak 21 days after denervation, there was significant difference compared with that of control sides (P < 0.05). However, the total number of Pax7 positive cells decreased with the prolongation of denervation, the expression of Pax7 was strong only at 3 days, then decreased gradually, and there was no positive cells in denervated muscles of 21 days. There were significant differences in Pax7 positive cells between experimental sides and control sides at 3 and 7 days (P < 0.05). The results of immunostaining showed that MyoD mRNA levels increased , and reached the peak at 21 days of denervation, there was significant difference compared with that of control sides (P < 0.05). Whereas, Pax7 mRNA expressed only in control, denervated muscles of 3 and 7 days, and its expression level decreased gradually.


CONCLUSIONS
One possible reason of the depletion of satellite cell pool in prolonged denervated muscle is the down-regulation of Pax7.
Liao
Hua
H
Institute of Clinical Anatomy, Southern Medical University, Key Laboratory of Tissue Construction and Examination of Guangdong Province, Guangzhou Guangdong, 510515, P.R. China.
Wang
Qi
Q
Xu
Dachuan
D
Qiu
Xiaozhong
X
Yu
Lei
L
Ouyang
Jun
J
D000818:Animals; D004195:Disease Models, Animal; D015536:Down-Regulation; D008297:Male; D009121:Muscle Denervation; D018482:Muscle, Skeletal; D009133:Muscular Atrophy / Q000235:genetics / Q000378:metabolism*; D017570:MyoD Protein / Q000096:biosynthesis / Q000235:genetics; D051761:Paired Box Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D032496:Satellite Cells, Skeletal Muscle / Q000378:metabolism*
D017570:MyoD Protein; C530821:PAX7 protein, rat; D051761:Paired Box Transcription Factors; D012333:RNA, Messenger