FIG. 1.

Hypoxia prolongs the life span of human VSMC. (A) VSMC life span under normoxia and hypoxia. Primary cultures of human VSMC were passaged under normoxia (21%) or hypoxia (1%) for the indicated number of days, and PD since the onset of the experiment were calculated as described in Materials and Methods. Results with cells derived from two different donors (donors 1 and 2) are shown. Similar results were obtained with cells from four different donors. (B) VSMC morphology at late passages. Cultures propagated under hypoxia retained a morphology characteristic of early passage VSMC (PD 38), whereas normoxic cultures adopted a flat, enlarged shape (PD 33). Both cultures shown here were derived from the same donor. Magnification, ×40. (C) SA β-Gal activity. SA β-Gal staining was performed on normoxic cultures at PD 33. Magnification, ×40.