Human umbilical vein endothelial cells (HUVECs) enhance osteogenic differentiation of fibrocartilage stem cells (FCSCs). (a) Alizarin red staining of a calcium deposition assay with varying ratios of FCSCs and HUVECs co-cultured in osteogenic media for 2 wk. (b) Alizarin red staining was quantitated at an absorbance of 405 nm. Data are mean ± SD; n = 4 experiments; *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001; 2-way analysis of variance (ANOVA) followed by Tukey’s post hoc test. (c) Alkaline phosphatase assay with various concentrations of FCSCs and HUVECs co-cultured in osteogenic media for 1 wk. Data are mean ± SD; n = 3 experiments; *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001; 2-way ANOVA followed by Tukey’s post hoc test. (d) Quantitative reverse transcription polymerase chain reaction of FCSCs and HUVECs co-cultured in various proportions in osteogenic media for 1 wk. Data are normalized to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and mean fold change relative to FCSCs alone ± SD; n = 3 experiments; *P ≤ 0.05; ***P ≤ 0.001; 2-way ANOVA followed by Tukey’s post hoc test.