Macrophage polarization dynamics and the impact of its modulation on the alveolar bone repair process

Author(s)

André Petenuci Tabanêz

• Document type: Doctoral Thesis
• Press: Bauru.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Bauru (FOB/SDB)
• Defense date: 2023-08-25

Examining board members

Gustavo Pompermaier Garlet; Gabriela Gennaro; Rodrigo Cardoso de Oliveira; Elcia Maria Varize Silveira

• Advisor: Gustavo Pompermaier Garlet

Abstract

This study evaluated the dynamics of macrophage polarization and the impact of its modulation, by drugs and by the aging process, on the outcome of the alveolar bone repair process in mice. Initially, C57Bl-6 submitted to upper incisor extraction was treated with Paclitaxel (PTX, at 1 mg/kg/week, 10 mg/kg/week and 10 mg/kg/48h doses), previously described as a M1 polarizing compound. Overall, PTX treated groups tendent to show greater density of fibroblasts and fibers, showing lower density of bone tissue in the 7-days period (p<0.05). PTX groups also showed higher density of vessels. PTX at 1 and 10 mg/kg/week dose, showed mostly a downregulation in inflammatory cells, while PTX at 10 mg/kg/48h dose showed a higher count in the inflammatory cells. Despite of these alterations, alveolar bone repair proceeded appropriately, in all PTX treated groups. Conversely, when tested in a distinct inflammatory context (i.e. chronic inflammatory experimental periapical lesions) PTX administration was associated with increased lesion progression/severity, associated with less M2(CD206+) cells numbers, lower ARG1 expression (p<0.05)and M1(CD80+) cells count associated with higher expression of several pro-inflammatory mediators (p<0.05), suggesting that PTX capacity to promote M1 pro-inflammatory profile may depend on the nature of inflammatory microenvironment. The next step was the evaluation of of Ibuprofen (IBU, 40 mg/kg and 200 mg/kg) effects on macrophages polarization dynamics and alveolar bone repair outcome. Our results showed that the IBU groups showed /decreased (?) inflammatory cells count, which was more pronounced in the at the 200 mg/kg dose (p<0.05). Also, the IBU group, at 40 mg/kg, showed lower count of CD206+ and lower count of GR1+ cells at the 3-days period (p<0.05). Despite such alterations, Ibuprofen therapy didnt show to impair the bone healing process, as commonly mentioned in the literature. Finally, we evaluated the possible influence of early aging associated changes in inflammatory immune response and its impact in bone repair. Our results demonstrated that the AGING group presented increased mRNA expression of pro-inflammatory interleukins and downregulated mRNA expression of the regulatory interleukins. Lower levels of growth factors as FGF1, Tfgb1 and Vegfa mRNA levels were also present in AGING group. Macrophage related markers, such iNOS, ARG and FIZZ showed downregulation in AGING group. Stem cell markers also showed downregulation in the AGING group in several experimental periods, compared with the control group (p<0.05). The AGING group also showed increased density in fibers and fibroblasts accordingly with the upregulation in Col1A2, Col1A1 and MMP8 (p<0.05) and general decrease in BMPs 2, 4 and 7 and in a several bone markers (p<0.05). Accordingly, bone density in the AGING group was lower with lower counts of osteoblasts (p<0.05). Our results points to a possible low grade pro-inflammatory profile and delayed differentiation of bone progenitor cells. However, such alterations didnt seem to impair bone healing process, since the as the alveolar socket was filled with new bone at the end of the experimental period. (AU)

• FAPESP's process: 18/25708-0 - Role of macrophage polarization towards M1 profile in the alveolar bone repair and osseointegration processes in mice
• Grantee: André Petenuci Tabanez
• Support Opportunities: Scholarships in Brazil - Doctorate