Research Paper Volume 17, Issue 7 pp 1784—1809

Figure 3. The skin model and the BM model show rejuvenated properties when co-cultured with young human serum in a long term dynamic in vitro MPS. The BM model was precultured in the HUMIMIC Chip3plus. After two weeks (culture day 14), the 3D long life skin model (Phenion) was added to the system and the co-culture treated with either young or old human serum for three weeks (culture day 14–35). (A) Immunofluorescence staining of Ki67 (red) of the 3D skin model. Representative images (scale bar = 100 μm) are shown on the left. Bar graphs show the relative proportion of Ki67+ cells normalized to treatment with old serum. (B) Determination of the DNA methylation-based biological age of the 3D skin models using the skin DNA methylation clock [7] and the blood age clock [8]. (C) Mitochondrial membrane potential of BM cells harvested on culture day 17, 24 and 31 normalized to treatment with old serum. (D) Flow cytometric analysis of BM cells. Bar graphs indicate the proportion of progenitor cells (left), monocytes (middle) and granulocytes (right) of all live BM cells after 14, 21, 28 and 35 days of culture. Data were obtained from one (A, C) or two (B, D) experiments with 4–7 replicates, shown as mean values +/− SEM (A, C, D) or mean values +/− SD (B). Unpaired t-test (A, B) or two-way ANOVA with Bonferroni correction (C, D), ^*p < 0.05, ^**p < 0.01.