Differential gene expression of periodontal ligament cells after loading of static compressive force.
BACKGROUND
Compressive force is an important mechanical stimulus on the periodontal ligament (PDL) and is closely related to therapeutic tooth movement. In this study, early or late response genes related to the compressive stress in PDL cells were evaluated. Particularly, the expression of interleukin (IL)-6, IL-8, and alkaline phosphatase (ALP) was studied.


METHODS
The primary cultured cells from PDL were grown in a three-dimensional collagen gel, and received a continuous static compressive force (1.76 g/cm(2)). The expressed genes were screened by cDNA microarray assays for 2 or 12 hours after the initiation of the mechanical force application. The genes of interest that showed significant changes in expression in the cDNA microarray assay were analyzed further by quantitative reverse transcriptase polymerase chain reaction (RT-PCR), enzyme-linked immunoabsorbent assays (ELISA), and ALP assays.


RESULTS
ALP, IL-6, and IL-8 were selected among the genes that significantly changed expression (/M/ >0.7) and subsequently were confirmed by quantitative RT-PCR. The secreted protein concentrations for IL-6, IL-8, and ALP activity were measured at 72 hours after application of continuous static compressive force. The protein level of IL-6 was significantly increased at 72 hours (P <0.001), but there was no significant change in IL-8 (P >0.05). ALP activity was decreased approximately 41.5% compared to the control (P = 0.015).


CONCLUSIONS
Considering that IL-6 is a potent osteoclast activator and the compressive side of PDL during orthodontic tooth movement shows the resorption of calcified tissue, the changed expression of IL-6 and ALP in response to the static compressive force in PDL cells may contribute to the orthodontic tooth movement or alveolar bone remodeling.
Lee
Yeon-Hee
YH
Department of Orthodontics, College of Dentistry, Seoul National University, Seoul, Korea.
Nahm
Dong-Seok
DS
Jung
Youn-Kwan
YK
Choi
Je-Yong
JY
Kim
Sahng Gyoon
SG
Cho
Michael
M
Kim
Myung-Hee
MH
Chae
Chang-Hoon
CH
Kim
Seong-Gon
SG
D000469:Alkaline Phosphatase / Q000096:biosynthesis / Q000235:genetics; D016723:Bone Remodeling / Q000235:genetics; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D019245:Compressive Strength; D003799:Dental Stress Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D015850:Interleukin-6; D016209:Interleukin-8; D000469:Alkaline Phosphatase