Early Osteogenic and Stromal Marker Responses of Osteoblast-like and Bone-Marrow Stromal Cell Lines to a Hyaluronic Acid-Coated Xenogeneic Bone Graft: An Exploratory In Vitro Analysis

Background: To investigate whether coating xenogeneic bone grafts with hyaluronic acid influences early osteogenic and fibrotic marker expression in vitro. Methods: Three xenograft materials were evaluated, including one hyaluronic acid-coated product and two uncoated deproteinized bovine bone mineral products, all commercially available. Human osteoblast-like cells (U2OS) and bone marrow stromal cells (HS5) were cultured with material extracts. Proliferation was assessed using XTT assay at 24 and 48 h. Cell adhesion was evaluated through fluorescence microscopy. Osteogenic markers (RUNX2, COL1A1) and fibrotic markers (COL3A1, TGF-β3) were quantified using quantitative real-time PCR. Statistical analysis employed one-way ANOVA with Benjamini–Krieger–Yekutieli (BKY) two-stage FDR correction for datasets that met the normality assumption, and the Kruskal–Wallis test with Dunn’s post hoc test for non-normally distributed data (HS5 XTT assay). Pairwise comparisons were restricted to each xenograft group versus the untreated control; an adjusted p-value < 0.05 was considered statistically significant. Results: At 48 h, the HA-coated xenograft (Xeno1) showed the highest mean metabolic activity in U2OS cells (0.538 ± 0.056) compared with the uncoated Xeno2 (0.450 ± 0.120) and Xeno3 (0.439 ± 0.073); however, after FDR correction no statistically significant differences were observed between groups. The coated material was associated with upregulation of early osteogenic markers, 2.61-fold RUNX2 upregulation (p = 0.01) compared to untreated cells. Both coated and uncoated xenografts demonstrated equivalent suppression of fibrotic markers in HS5 cells, reducing COL3A1 by 92.7% (p = 0.001) and TGF-β3 by 92.1% (p = 0.001). Conclusions: These exploratory in vitro findings suggest that HA coating may enhance early osteogenic marker expression. The observed effects on stromal markers warrant further investigation using primary cells, additional fibrotic endpoints (e.g., TGF-β1, ACTA2), and in vivo models before translational conclusions can be drawn.