ACCELERATED-GROWTH AND SENESCENCE OF ARTERIAL ENDOTHELIAL-CELLS EXPRESSING THE SMALL MOLECULAR-WEIGHT HEAT-SHOCK PROTEIN HSP27

Bovine arterial endothelial cells were stably transfected with the hum an wild-type (wt) HSP27 or a mutant gene (mu) encoding a nonphosphoryl atable form of the protein. At early passage both cultural and cellula r morphology were similar, although the vacuole content in wtHSP27 was much higher than muHSP27 cells. As the cultures aged, wtHSP27 cells b ecame large, polymorphic, highly vacuolated, and reached senescence be fore muHSP27 transfected cultures, which remained small and polygonal with few detectable vacuoles. Vector control cells showed an intermedi ate phenotype. Tritiated thymidine incorporation studies were performe d with multiple wtHSP27 and muHSP27 clones and the results compared wi th 11 vector control clones. The results showed an average increase in growth rate for the wtHSP27 cells of 3.0 +/- 0.6 times. The growth ra te of eight muHSP27 clones showed a slight decrease. Estradiol treatme nt of endothelial cells resulted in an increase in both bovine and hum an HSP27, with peak expression at 100 nM. Treatment of the vector-tran sfected cells with 100 nM estradiol resulted in a 1.44 +/- 0.18 fold i ncrease in growth rate, which was blocked by expression of muHSP27. Th ese data demonstrate a role for HSP27 in controlling the growth rate o f endothelial cells in an estrogen-responsive manner.