BACKGROUND15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), one of the major metabolites from prostaglandin D2 in arachidonic acid metabolic pathway, has potential anti-inflammatory properties. The objective of this study was to explore the effects of 15d-PGJ2-loaded poly(D,L-lactide-co-glycolide) nanocapsules (15d-PGJ2-NC) on inflammatory responses and bone regeneration in local bone defect.

METHODSThe study was conducted on 96 Wistar rats from June 2014 to March 2016. Saline, unloaded nanoparticles, free 15d-PGJ2or 15d-PGJ2-NC, were delivered through a collagen vehicle inside surgically created transcortical defects in rat femurs. Interleukin-6 (IL-6), interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) levels in the surrounding soft tissue were analyzed by Western blot and in the defect by quantitative real-time polymerase chain reaction over 14 days. Simultaneously, bone morphogenetic protein-6 (BMP-6) and platelet-derived growth factor-B (PDGF-B) messenger RNA (mRNA) in the defect were examined. New bone formation and EphrinB2 and osteoprotegerin (OPG) protein expression in the cortical defect were observed by Masson's Trichrome staining and immunohistochemistry over 28 days. Data were analyzed by one-way analysis of variance. Least-significant difference and Dunnett's T3 methods were used with a bilateral P< 0.05.

RESULTSApplication of l5d-PGJ2-NC (100 μg/ml) in the local bone defect significantly decreased IL-6, IL-1β, and TNF-α mRNA and protein, compared with saline-treated controls (P < 0.05). l5d-PGJ2-NC upregulated BMP-6 and PDGF-B mRNA (P < 0.05). New bone formation was observed in the cortical defect in l5d-PGJ2-NC-treated animals from 7th day onward (P < 0.001). Expression of EphrinB2 and OPG presented early on day 3 and persisted through day 28 in 15d-PGJ2-NC group (P < 0.05).

CONCLUSIONStable l5d-PGJ2-NC complexes were prepared that could attenuate IL-6, IL-1β, and TNF-α expression, while increasing new bone formation and growth factors related to bone regeneration.