High glucose levels increase osteopontin production and pathologic calcification in rat dental pulp tissues.
BACKGROUND
Pulp stones are frequently formed as a pathologic calcification product in dental pulp tissues, but the pathogenesis is poorly understood. We previously found that osteopontin (OPN) was produced by dental pulp cells, and its expression was associated with formation of the pulp stone matrix. It was reported that amorphous calcification appeared in the dental pulp of diabetic patients. The aim of this study was to determine the relationship between OPN expression and pathologic calcification in rat diabetic pulp.


METHODS
The effect of glucose on OPN production and alkaline phosphatase activity in cultured rat dental pulp cells (RPC-C2A) was investigated, and then dental pulp calcification and OPN expression in diabetic rats were determined and compared with those in healthy rats by histologic and immunohistochemical analyses.


RESULTS
In RPC-C2A cells, biochemical analysis showed that a high concentration of glucose (50 mmol/L) increased OPN protein production and alkaline phosphatase activity 1.3-fold and 1.5-fold, respectively. Histologic observations showed more calcified particles in dental pulp tissues in diabetic than in nondiabetic rats. Moreover, a thickened layer of predentin was formed in the radicular pulp of diabetic rats. OPN was more strongly stained around the calcified particles and in the odontoblast zone under the thickened predentin in diabetic rats.


CONCLUSIONS
OPN might be a key molecule involved in the increase of pathologic pulp calcifications, which are frequently observed in diabetic patients.
Inagaki
Yuji
Y
Department of Periodontology and Endodontology, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima, Japan.
Yoshida
Kaya
K
Ohba
Hirofumi
H
Seto
Hiroyuki
H
Kido
Jun-ichi
J
Haneji
Tatsuji
T
Nagata
Toshihiko
T
D000469:Alkaline Phosphatase / Q000032:analysis / Q000187:drug effects; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D018929:Cell Culture Techniques; D002460:Cell Line; D003782:Dental Pulp / Q000187:drug effects* / Q000473:pathology; D003784:Dental Pulp Calcification / Q000209:etiology* / Q000473:pathology; D003804:Dentin / Q000187:drug effects / Q000473:pathology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications; D005947:Glucose / Q000494:pharmacology*; D006442:Glycated Hemoglobin / Q000032:analysis; D008297:Male; D009804:Odontoblasts / Q000187:drug effects / Q000473:pathology; D053495:Osteopontin / Q000032:analysis / Q000187:drug effects*; D051381:Rats; D020334:Rats, Inbred OLETF; D020318:Rats, Long-Evans; D013997:Time Factors; D014092:Tooth Root / Q000187:drug effects / Q000473:pathology
D000469:Alkaline Phosphatase; D001786:Blood Glucose; D005947:Glucose; D006442:Glycated Hemoglobin; D053495:Osteopontin