Effect of intermittent administration of hPTH(1-34) on the early stages of alveolar wound healing after rat molar extraction

Author(s)

Juliana dos Santos Neves

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2012-02-28

Examining board members

Pedro Duarte Novaes; Maria Luiza Ozores Polacow; Adriana Fernandes da Silva; Karina Gonzales Silverio; Marcelo Rocha Marques

• Advisor: Pedro Duarte Novaes; Cristiane Ribeiro Salmon

Abstract

The intermittent administration of parathyroid hormone (PTH) promotes an increase in bone mass, and it is currently used to treat osteoporosis. However, few studies have evaluated the effects of PTH on the metabolism of the alveolar bone, and more specifically in the repair process of this structure, which may have a positive effect on alveolar wound healing. Considering that the pattern of the alveolar wound healing post molar extraction in rats is similar to that of the humans and its clinical relevance, this study aimed to analyze the effect of intermittent PTH administration on alveolar wound healing after extraction of rat molars. Wistar rats (200g) had their first molars extracted and received subcutaneous injections of 40 ?g/kg of hPTH (1-34) (PTH group) or vehicle solution (control group) in alternated days after the extraction. The animals were sacrificed at 3, 5, 7 and 11 days after surgery. Histomorphometric analysis of the volume of newly formed bone, number of osteoblasts and TRAP-positive osteoclasts were performed on serial histological sections. Receptor activator of nuclear factor ?? ligand (RANKL), bone sialoprotein (BSP) and osteopontin (OPN) were localized at the healing socket by immunohistochemistry. Collagen 1 (Col1?1), alkaline phosphatase (Alp), insulin growth factor (Igf-1), osteocalcin (Ocn), Bsp, Opn, osteoprotegerin (Opg) and Rankl gene expression was assessed by qRT-PCR. Newly formed bone was observed in sockets from 5 days of repair in both groups. The volume of newly formed bone was significantly higher in PTH group at 5, 7 and 11 days of repair (p <0.05). In the control group there was a gradual increase in the expression of all genes studied, except for Opn, through the periods of healing. Overall, the expression of Col1?1, Alp, Igf-1 and Ocn in the PTH group was higher at the initial periods, followed by a significant down-regulation at 7 days of repair compared to the control group. Bsp expression was similar in both groups, while Opn expression was down-regulated by PTH at 7 and 11 days of repair. Both proteins showed the same distribution on the forming trabeculae in the socket. The number of TRAP-positive osteoclasts was similar in both groups in all periods of repair, as well as the labeling pattern for RANKL. However, viii Rankl:Opg ratio was higher in the PTH group at 11 days of repair, suggesting that PTH may promote osteoclastogenesis from this period. In conclusion, the intermittent treatment with hPTH-(1-34) had an anabolic effect on the alveolar wound healing specifically at 5 days of repair, stimulating an increase on the osteoblast number and on the expression of genes related to the differentiation and production of bone matrix by these cells, thereby resulting in increased volume of newly formed bone in the healing socket (AU)

• FAPESP's process: 08/05212-8 - EFFECT OF INTERMITTENT ADMINISTRATION OF hPTH(1-34) ON ALVEOLAR WOUND HEALING OF RAT MOLARS.
• Grantee: Juliana dos Santos Neves
• Support Opportunities: Scholarships in Brazil - Doctorate