Periodontal Fibroblasts—Macrophage Crosstalk in External Inflammatory Root Resorption

Introduction This study aimed to understand the influence of periodontal fibroblasts (PDLFs) on clastic differentiation of macrophages (Mφ) in different resorptive environments. Methods PDLF-Mφ direct coculture (juxtacrine) was seeded on dentin, cementum, and polystyrene with/without lipopolysaccharide, macrophage colony-stimulating factor, and receptor activator of nuclear factor kappa beta ligand for 7 and 14 days and stained for tartrate-resistant acid phosphatase (TRAP) activity. PDLF-Mφ cocultured on polystyrene were immunostained for CD80, CD206, NFATc1, STAT6, and periostin, and cell culture supernatants were assessed for cytokines on days 2 and 7. Mφ grown in conditioned media of PDLFs (paracrine) and Mφ monoculture were used as controls. Data was analyzed using Student t test and one-way analysis of variance with the Tukey multiple comparisons test (P < .05). Results PDLF-Mφ coculture showed a higher number of TRAP-positive multinucleated cells than Mφ monoculture on dentin and polystyrene. No TRAP-positive multinucleated cells were observed in paracrine and cementum. The expression of CD80 and CD206 in PDLF-Mφ was similar at day 2, whereas CD206 was greater than CD80 at day 7. The expression of STAT6 was greater than NFATc1 at both days 2 and 7 (P < .05). Periostin expression in the presence of the lipopolysaccharide, macrophage colony-stimulating factor, and receptor activator of nuclear factor kappa beta ligand combination was down-regulated in PDLF monoculture, whereas it was up-regulated in PDLF-Mφ coculture. The cytokine profile of PDLF-Mφ on day 2 was predominated by interleukin (IL)-1β, tumor necrosis factor alpha, and MMP9 and MMP2 on day 7. IL-6 and IL-8 showed steady expression at both days 2 and 7. Conclusions The study highlights the juxtacrine effect of PDLFs on the clastic differentiation of Mφ with a difference in clastic activity between dentin and cementum. The study also emphasizes the temporal effect of tumor necrosis factor alpha, MMP2, MMP9, and IL-1β on intercellular crosstalk in resorptive environments.