Figure 1.

Bleomycin induces PTSC senescence in a dose-dependent manner. (a) Rat PTSCs were treated without or with bleomycin (Bleo) for 5 days. (b) PTSCs were stained for senescence-associated β-galactosidase (β-gal) activity. As seen, at 10 and 50 μg/ml, the senescent cells look flattened and enlarged (a, yellow arrows) compared to control cells, which are elongated (a, red arrows). Scale bar = 200 μm. (c) Semiquantification shows a marked increase in the number of β-gal-positive cells in a bleomycin-dose dependent manner. Results are expressed as mean ± SD, n = 3. ^∗p < 0.01 compared to the control group. (d) Tendon tissues obtained from 2.5 month-old and 18 month-old rats were stained for the β-gal activity. It is evident that the young tendon is well organized without staining of β-gal; in contrast, aged tendon is disorganized and stained with β-gal.