ABSTRACT
BACKGROUND: Anemia is an inevitable consequence of chronic renal failure. Gene therapy using lentiviral vector (LV) would be an effective tool to treat anemia associated with renal failure. METHODS: A LV carrying the erythropoietin (EPO) cDNA was administered to skeletal muscle of partially nephrectomized rats, which is a model of uremia. The red blood cell production and serum EPO levels were temporally monitored in these rats. Polymerase chain reaction assays were done to validate the presence of the LV in the experimental rats. RESULTS: After a single intramuscular injection of LV at a dose of 55 microg p24 Gag antigen (approximately 5 x 10(7) transducing units), blood hematocrit (Hct) levels increased and peaked at 3 weeks (47.8 +/- 4.2%, p < 0.01, n = 8) with the levels being maintained for at least 20 weeks (duration of study; 44.9 +/- 3.3%, p < 0.01, n = 3). The control rats receiving LV expressing lacZ had Hct levels of 36.9 +/- 4.1% (n = 8) at 3 weeks and 33.1 +/- 3.7% (n = 4) at 20 weeks, respectively. The serum EPO levels in the rats injected with the LV expression EPO significantly increased (p < 0.01) to 156.3 +/- 3.0 mU/ml compared to the control rats (63.9 +/- 1.7 mU/ml). Polymerase chain reaction analysis of the isolated genomic DNA from the LV-injected rats showed specific positive detection of the LV in only the skeletal muscle tissue at the site of injection, whereas the other tissues, including the liver, spleen, and kidney, were negative. CONCLUSIONS: This study demonstrates that intramuscular injection of LV can produce highly efficient and sustained EPO secretion in uremic rats, and suggests that this approach could be an effective tool to deliver secretable proteins at therapeutic levels in various animal disease models.