Effect of Leptin on Odontoblastic Differentiation and Angiogenesis: An In Vivo Study

Leptin is secreted as a peptide hormone from adipose tissues. The aim of this study was to evaluate the effects of leptin on reparative dentin formation and angiogenesis in the pulp tissue of teeth in vivo. Twenty-four 7-week-old male rats were anesthetized. Cavities were prepared in maxillary first molars. Pulp cappings were performed with collagen scaffold (Col) with a phosphate-buffered saline (PBS) vehicle (Col + PBS), leptin 1 μmol/L with Col (L1 + Col), or leptin 10 μmol/L with Col (L10 + Col). For the negative control group (no pulp capping), pulp capping was not performed. All cavities were sealed with resin-modified glass ionomer followed by a micro–computed tomographic scan, histologic examination, and immunohistochemical analysis. The volume of newly formed mineralized tissue in the leptin group was significantly (P < .01) higher than that in the control group based on micro–computed tomographic analysis. In histologic examination, hard tissue formation was rarely shown in the no pulp capping and Col + PBS groups. However, significantly (P < .01) larger amounts of newly mineralized tissue deposition were observed in the leptin groups. In immunohistochemical analysis, reparative dentin and new vessels formed in the pulp cavity of the leptin groups. Vascular endothelial growth factor, dentin sialoprotein, and dentin sialophosphoprotein were expressed around the newly formed mineralized tissue area. Leptin showed the ability to induce angiogenesis, odontogenic differentiation, and mineralization in exposed rat pulps. Leptin also exhibited favorable inflammatory responses in the pulp tissue. Not only osteodentin but also tubular dentin and new vessels were observed in the pulp cavity.