Abstract 11503: Examination of Paracrine Effects of Ultrasound-Mediated Survivin Gene Therapy for Heart Failure
The anti-apoptotic protein, Survivin (SURV), was recently shown to be secreted extracellularly, where it retains its anti-apoptotic potential. We hypothesized that extracellular SURV is capable of promoting cell survival in vitro, and may be an important mechanism whereby SURV gene therapy ameliorates left ventricular (LV) systolic dysfunction in doxorubicin (DOX)-induced cardiomyopathy (DOX-CMP). H9c2 cells were transfected with SURV, and protein levels in the culture supernate were measured by ELISA at days 1, 2 and 4 (n=9). Apoptosis rates in response to DOX treatment were measured in control, SURV-transfected and non-transfected cells incubated with SURV-conditioned media. SURV gene therapy using ultrasound-mediated gene delivery (UMGD) was performed in a rat model of DOX-CMP. Animals were treated with either SURV (N=30) or empty vector (EMPTY N=8) via UMGD at week 3. Control animals (CON N=24) received no treatment. Echocardiography was performed at week 0, 3 and 6, with invasive pressure volume (PV) loop assessment at week 6 (N=7-8 per group). SURV was detected in the supernate at all time points after transfection (p<0.01). DOX stress in non-transfected cells increased apoptosis (n=5, 50 ± 7%, p<0.01) and SURV transfected cells showed a decrease in apoptosis (n=4, 23 ± 2%, p<0.01 vs non-transfected). SURV-conditioned media had a modest effect on apoptosis (n=5, 35 ± 13%, p=0.07). In vivo analysis of LV fractional shortening (LVFS) was comparable in all groups at week 0 (DOX 47 ± 1%, SURV 48 ± 1%, EMPTY 50 ± 1%, p=NS). At week 6, LVFS in CON and EMPTY animals declined from week 3 (39 ± 2% and 39 ± 2%, respectively, p<0.01) whereas LVFS was maintained in SURV animals (44 ± 1%, p=NS). PV loop analysis demonstrated reduced systolic function (ESPVR) in DOX (vs CON, p<0.05). SURV treatment improved systolic function (ESPVR, p<0.01 vs EMPTY). TGFb-1 mRNA was increased in DOX and EMPTY animals (p<0.05 vs CON) but SURV animals had TGFb-1 levels comparable to that of control (p=NS). SURV gene therapy can prevent the progression of LV systolic dysfunction in DOX-CMP. This effect may be attributed to the decrease in apoptosis of functional cells and preventing maladaptive LV remodeling, by both direct transfection of cells and by paracrine mechanisms.
- © 2011 by American Heart Association, Inc.