Figure 4. Senescence stimulates RANKL production in human cells.

(A) Representative photomicrographs of SA–β-gal–stained cultures and (B) mRNA levels by qRT-PCR in nonsenescent and senescent IMR-90 cells induced by replicative exhaustion (triplicate cultures). Original magnification, ×100. (C) Representative photomicrographs of SA–β-gal–stained cultures and (D) mRNA levels in human mesenchymal stromal cells isolated from 29 year-old and 33 year-old male donors, cultured with 50 μM etoposide for 4 days. Original magnification, ×100. Line and error bars represent mean ± SD; P values by 2-tailed unpaired t test.