Transplantation of lac-Z-Transduced Microvascular Endothelial Cells into the Skeletal Muscle Capillary Bed of the Rat Hindlimb Occurs Independent of the Duration of Fernoral Artery Occlusion after Injection of Cells

Abstract

The skeletal muscle capillary bed may be an ideal recipient site for transplantation of genetically modified autologous endothelial cells and thus provide a basis for a technique of somatic gene therapy that would be applicable to a variety of acquired and inherited human diseases. The purpose of this study was to test the hypothesis that adhesion of lac-Z -transduced microvascular endothelial cells (MVEC) in the skeletal muscle capillary bed in vivo is dependent on the duration of arterial occlusion after injection of the transduced MVEC. MVEC derived from the abdominal fat pad of syngeneic rats (Wistar F-455) were transfected with the BAG vector, a replication-incompetent retroviral vector containing the lac-Z gene for [beta]-galactosidase and the Tn5 gene for selection of the transduced cells by the neomycin analogue, G418. lac-Z-transduced MVEC were radiolabeled with 125I-PKH-95, and, after the femoral artery was occluded for 10 min, these cells (1 to 2 x 106) were injected intraarterially into the rat hindlimb. In the experimental groups the femoral artery clamp was removed at 0, 60, or 120 min after injection. A control group without pre- or postinjection femoral arterial occlusion was also studied. Adhesion of MVEC in the skeletal muscle capillary bed (mean percentage of injected 125I activity) was determined in groups of 4 rats at 1 day, 1 week, and 1 month after injection. Adhesion of the transduced MVEC did not increase as the duration of femoral artery occlusion after injection was increased. The highest rate was found in the group subjected to only a 10-min preclamp (32% at 1 day, 17% at 1 week, and 15% at 1 month). These results indicate that mechanical forces such as capillary shear rate and perfusion pressure may not be important determinants of adhesion and incorporation of transduced MVEC into skeletal muscle capillaries. Nevertheless, these results document significant adhesion and persistence of genetically modified MVEC transplanted into the capillary bed of the skeletal muscle.