Effects of melatonin alone or in combination with Bio-Oss® on early osteoblastic activity: An in vitro study

Background Melatonin modulates bone metabolism and enhances osteogenic activity; however, whether these effects are maintained when combined with xenogeneic bone substitutes during early osteoblastic responses remains unclear. This study investigated the effects of melatonin alone and combined with the xenogeneic bone substitute Bio-Oss® on early osteoblastic activity in vitro . Methods Human osteoblast-like cells (SaOS-2) were allocated to four groups: control, melatonin (0.1 mM), Bio-Oss® (10 mg/mL), and melatonin plus Bio-Oss®. Three independent biological experiments were performed. Cell proliferation (Trypan blue exclusion), viability (MTT assay), and type I collagen secretion (ELISA) were assessed at 24 h, 72 h, and 7 days. Data were analyzed using the Kruskal-Wallis test followed by Dunn's post hoc test ( p < 0.05). Results Proliferation and viability increased over time in all groups. At 7 days, Bio-Oss®-containing groups showed significantly reduced proliferation compared with the control group ( p < 0.05), whereas the melatonin-only group did not differ significantly ( p > 0.05). Cell viability was lower in Bio-Oss®-containing groups at 72 h and in the melatonin plus Bio-Oss® group at 7 days ( p < 0.05). Type I collagen secretion did not differ significantly among groups at any time point ( p > 0.05). Melatonin alone did not differ significantly from the control, whereas its combination with Bio-Oss® did not enhance early osteoblastic activity. Conclusion Combining melatonin with Bio-Oss® did not enhance early osteoblastic activity in this in vitro model. These findings provide useful information for future studies investigating combinations of bioactive molecules and xenogeneic bone substitutes in bone regeneration.