Rosavin, but not its combination with salidroside, lowers total β-catenin in human osteoblast cultures: an exploratory in vitro study under mineralizing conditions.

Osteoblast dysfunction and altered Wnt/β-catenin-dependent responses accompany bone-remodeling imbalance in rheumatic and degenerative joint disease. Rosavin and salidroside are constituents of Rhodiola rosea preparations used without prescription, and are always encountered together rather than separately. This exploratory in vitro study asked whether the two compounds and their combination differentially affect total β-catenin concentration and cell-covered area in human osteoblasts (HOBs). HOBs from one commercial preparation (passage 7) were cultured in growth medium (GM) or mineralization medium (MM) and exposed to rosavin 50 µM (R50), salidroside 50 µM (Sal50) or both (R50/Sal50). Total β-catenin was quantified by ELISA in four independently cultured, treated, harvested and lysed wells per condition at days 7, 14 and 21. Cell-covered area was estimated from 79 phase-contrast fields. Welch ANOVA with Games-Howell post-hoc testing was pre-specified. Total β-catenin differed between conditions at day 14 (Welch ANOVA p = 0.003, Holm-adjusted p = 0.009; η² = 0.43): 8.9 ± 3.8 ng/mL in R50 versus 28.5 ± 3.8 in Sal50, 26.5 ± 16.9 in R50/Sal50, 23.5 ± 7.9 in MM and 27.4 ± 8.6 in GM. Sal50 versus R50 was the only contrast surviving correction (difference 19.6 ng/mL, 95% CI 13.1-26.1; p = 0.002). No difference was detected at day 7 (p = 0.87) or day 21 (p = 0.23). Cell-covered area differed at days 7 and 21, with R50/Sal50 lowest and most variable (54.5 ± 23.4% versus 98.1 ± 1.8% in GM at day 7). Cell-covered area explained 12% of the variance in group-mean β-catenin (r = - 0.35). Rosavin alone was associated with a marked reduction in total β-catenin at day 14; its combination with salidroside was not. The two constituents therefore do not act interchangeably on human osteoblasts. These observations derive from a single experimental series and require replication before mechanistic or clinical interpretation.