Substance P increases production of proinflammatory cytokines and formation of osteoclasts in dental pulp fibroblasts in patients with severe orthodontic root resorption.
BACKGROUND
The objective of this study was to determine the extent to which substance P (SP) increases proinflammatory cytokine production and osteoclast formation of human dental pulp fibroblasts (HDPF) in patients with severe orthodontically induced inflammatory root resorption (OIIRR).


METHODS
HDPF were obtained from 5 patients with severe apical root resorption after orthodontic treatment. The levels of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha were determined after 24 hours by using ELISA kits. Furthermore, culture supernatants were added to cultured human osteoclasts, and osteoclast formation was observed after tartrate-resistant acid phosphatase (TRAP) staining and the formation of resorption cavities.


RESULTS
Stimulation with SP increased the levels of IL-1beta, IL-6, and TNF-alpha, in a time- and concentration-dependent manner, although the increase was greater in the severe root resorption (SRR) group than in the nonresorption (NR) group (P < 0.001, 3-way repeated measures ANOVA). As for osteoclast formation, the numbers of TRAP-positive multinucleate cells and resorptive pits were significantly increased in the SRR group compared with the NR group (P < 0.001, 2-way repeated measures ANOVA).


CONCLUSIONS
These results suggest that HDPF stimulated with SP might be deeply involved in the progress of inflammation in pulp tissue and the incidence of SRR during orthodontic treatment.
Yamaguchi
Masaru
M
Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan. yamaguchi.masaru@mascat.nihonu.ac.jp
Ozawa
Yasuhito
Y
Mishima
Hiroyuki
H
Aihara
Norihito
N
Kojima
Tadashi
T
Kasai
Kazutaka
K
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D056657:Cathepsin K; D002403:Cathepsins / Q000096:biosynthesis; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis*; D003782:Dental Pulp / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D053583:Interleukin-1beta / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D008297:Male; D009971:Orthodontics, Corrective / Q000009:adverse effects*; D010010:Osteoclasts / Q000166:cytology; D011671:Pulpitis / Q000378:metabolism*; D012391:Root Resorption / Q000209:etiology* / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D016207:Cytokines; D053583:Interleukin-1beta; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D013373:Substance P; D002403:Cathepsins; C534130:CTSK protein, human; D056657:Cathepsin K