In vivo gene transfer: Prevention of neointima formation by inhibition of mitogen-activated protein kinase kinase

Background. The mitogen activated protein kinase kinase (MAPKK) is a protein downstream ras which is rapidly activated in cells stimulated with various extracellular signals. These proteins are believed to play a pivotal role in integrating and transmitting transmembrane signals required for cell growth. Methods and Results. To study the effect of inhibition of MAPKK on smooth muscle cell (SMC) proliferation in vivo after vascular injury, we performed experimental balloon angioplasty using the standard Clowes technique in male Wistar rats 14-weeks old. The animals did not receive any treatment after vascular injury (N = 6) or were randomly assigned to receive, after balloon injury, a 30% (w/v) pluronic gel solution applied to the injured carotid artery, containing respectively: 1) no plasmid DNA (n = 10); 2) RSV-lacZ (encoding the β-galactosidase gene) as control gene without effects on SMC proliferation (n = 10); 3) Tg- CAT (encoding cloramphenicol acetyl-transferase gene under the control of thyreoglobulin promoter) as an additional control gene without effects on SMC proliferation (n = 7); 4) a negative mutant of Mitogen-Activated Protein Kinase Kinase (MAPKK ^-) (n = 13). Fourteen days after vascular injury, carotid arteries were removed and cross sections were cut and stained with hematoxylin/eosin. Morphometric analysis demonstrated, in the MAPKK ^--treated rats, a significant reduction of both neointima (0.096 ± 0.018 mm ² vs. 0.184 ± 0.019 mm ², p <0.01) and neointima/media ratio (0.603 ± 0.103 vs. 1.471 ± 0.161, p <0.01) compared to control DNA. Conclusions. The inhibition of MAPKK, by a dominant inhibitor mutant gene, prevents the SMC proliferation after vascular injury in vivo.