Trauma-specific and time-dependent changes of the RANK/RANKL/OPG signaling axis in the periapical bone tissue after experimental traumatic dental injuries in rats.

The RANK (receptor activator of NF-κB)/RANKL (RANK ligand)/OPG (osteoprotegerin) system regulates osteoclast differentiation, activity, and survival, as well as inflammatory/immune responses, suggesting its potential involvement in the healing of traumatic dental injuries (TDIs). The aim was to characterize the molecular expression dynamics of the RANK/RANKLOPG axis in periapical bone tissue following TDIs in a rat model. TDIs were reproduced on the maxillary left first molar of rats (n = 18): tooth avulsion (TA); lateral luxation (LL); complicated crown fracture (CCF). Target protein levels in periapical bone tissue were determined by Western blotting on days 3, 14, and 28 following injury (n = 6 per time point subgroup). After TA and LL, no significant changes in RANK content were observed over the healing, while OPG levels gradually declined. However, RANKL expression dynamics differed markedly between these groups: in TA, RANKL increased rapidly, reaching a peak on day 14, then normalized to almost the control value by day 28; in LL, RANKL increased gradually, peaking on day 28. CCF was associated with a distinct, nonlinear pattern of RANK fluctuation: a rapid growth on day 3, followed by a marked decrease on day 14 and a moderate elevation on day 28. OPG reached a minimum on day 14, then increased on day 28. Finally, membrane-bound and soluble RANKL levels increased on day 3 after CCF and subsequently declined. The observed RANK/RANKL/OPG protein expression dynamics in periapical bone tissue were trauma-specific and time-dependent, suggesting that different TDI types are associated with distinct molecular remodeling-related shifts, pending functional validation.