Stimulation of the hypothalamic-pituitary-adrenal axis by chronic stress and its effect on the progression of periapical injury

Author(s)

Giovanna Bignoto Minhoto

• Document type: Master's Dissertation
• Press: São José dos Campos. 2020-02-05.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Ciência e Tecnologia. São José dos Campos
• Defense date: 2019-12-06
• Advisor: Marcia Carneiro Valera

Abstract

Since chronic stress may excessively stimulate the sympathetic nervous system, leading to a decreased immune response, favoring bone loss in the face of an inflammatory process, the aim of this study was to evaluate the effect of chronic stress on the progression of induced periapical injury and the best time to evaluate the progression of this lesion. Forty-eight Wistar rats were submitted to an animal model of induction of periapical lesion by exposing the right and left lower first molar pulp cavity to the oral environment. The animals were divided into 2 groups: with stress (E) and without stress (SE), which were subdivided into 3 subgroups according to the period of evaluation of periapical lesion progression (n = 8): stress and 14 days of periapical lesion formation (E14); stress and 21 days of periapical lesion formation (E21); stress and 28 days of periapical lesion formation; without stress and 14 days of periapical lesion formation (SE14); without stress and 21 days of periapical lesion formation (SE28); without stress and 28 days of periapical lesion formation (SE28). Stress groups (E) began to undergo chronic stress 21 days before the induction of periapical lesion began and were maintained in this stress condition throughout the experiment. The following analyzes were performed: a) weight of the animals at the beginning and end of the experiment; b) blood corticosterone level for stress confirmation; c) microtomography to evaluate the progression of the lesion; d) Histological and histomorphometric analysis; d) Immunohistochemistry to evaluate RANKL and OPG expression. Data were evaluated by Graphpad prism 6 software using the Two Way Anova test. From the results obtained it was observed a smaller weight gain in the stressed groups in relation to the non stressed ones. The lesion was significantly higher in the stressed group with 21 days of periapical lesion. No statistical difference was observed in relation to the inflammatory infiltrate, since all groups presented moderate inflammatory infiltrate. Regarding the extension of the lesion through histomorphometric evaluation, it was observed that the lesion was significantly larger in stressed animals than in non-stressed animals in the 21-day period. Through immunohistochemistry no significant difference was observed in the expression of RANKL and OPG (p <0.05). It is concluded that chronic stress influences the formation of periapical lesion in Wistar rats, increasing bone loss and that the best period for this analysis is 21 days of progression of induced periapical lesion in rats. (AU)

• FAPESP's process: 18/12438-4 - Stimulation of the hypothalamic-pituitary-adrenal axis by chronic stress and its effect on the progression of the periapical lesion
• Grantee: Giovanna Bignoto Minhoto
• Support Opportunities: Scholarships in Brazil - Master