d) representative images of Ki67 and p16Ink4a immunofluorescence and SA-β-Gal staining; e) % of Ki67 positive cells (28 days after co-culture); f) % of p16INK4A positive cells (28days after co-culture); g) % of SA-β-Gal positive cells (28 days after co-culture); h) Western blotting for p21 and quantification; i) MitoSOX fluorescence; 