[Identification of cell apoptosis during premaxillary suture expansion in rat].
OBJECTIVE
To identify the incidence of cell apoptosis during premaxillary suture expansion.


METHODS
Forty SD rats were randomly allotted into experimental and control groups. The experimental animals were subjected to premaxillary suture expansion by a helix spring with (200+/-10)g initial force. They were sacrificed on day 1, 2, 3 and 5(n=5). The sequence of histological changes and osteoblast proliferation in the premaxillary suture were evaluated by hematoxylin and eosin(HE) and toluidine blue staining. Cellular apoptosis was identified by ssDNA immunostaining. The difference between experimental and control groups was analyzed by Student's t test with SPSS 15.0 software package.


RESULTS
The width of premaxillary suture was enlarged 1 day after expansion and osteoblasts were accumulated along the suture. After 2 days of stretching, the number of the osteoblasts increased to the peak. New bone deposition was identified on day 3 and projection of suture with bone trabeculae was apparent on day 5. ssDNA immunostaining showed few apoptotic cells in premaxillary suture during natural growth. Upon expansion, cell apoptosis was identified in osteoblasts along the suture and the osteocytes embedded in premaxillary bone, especially on day 2 and day 3(P<0.01).


CONCLUSIONS
Apoptotic cell death might regulate the growth modification of premaxillary suture upon mechanical stretching.
Zhang
Lei
L
Department of Orthodontics, College of Stomatology, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai 200011, China. everytime_lei@126.com
Chen
Rong-Jing
RJ
Tang
Guo-Hua
GH
D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D003393:Cranial Sutures; D010006:Osteoblasts; D010155:Palatal Expansion Technique; D051381:Rats; D017207:Rats, Sprague-Dawley; D013537:Sutures