Myoblast transfer of human erythropoietin gene in a mouse model of renal failure.

Anemia is an invariable consequence of end-stage renal failure (ESRF) and recombinant erythropoietin has dramatically improved the quality of life of patients with ESRF. As an alternative approach, we developed a myoblast gene transfer system for the systemic delivery of human erythropoietin (EPO). We recently reported that transplantation of 4 x 10(7) cells of a C2 myoblast cell clone that stably secretes high level of functional human EPO, increased hematocrit from 44.6 +/- 3.0 to 71.2 +/- 7.9(%) in 2 wk, and the increase was sustained for at least 12 wk in nude mice. A renal failure model was created by a two-step nephrectomy in nude mice, and myoblasts were transplanted 3 wk after the second nephrectomy, when mean blood urea nitrogen level had increased from 26.3 +/- 6.1 to 85.4 +/- 24.0 (mg/dl) and the hematocrit had decreased from 45.2 +/- 2.7 to 33.9 +/- 3.7(%). After transplantation, the hematocrit markedly increased to 68.6 +/- 4.2(%) 2 wk, and to 68.5 +/- 4.0(%) 7 wk after the transplantation. Serum human EPO concentration determined by ELISA indicated a persistent steady EPO production from the transplanted muscle cells 8 wk after the transplantation. The fate of transplanted myoblasts in uremic mice was monitored by transplanting the EPO-secreting clone which had also been transduced with BAG retrovirus bearing the beta-galactosidase gene. 8 wk later, X-gal positive myofibers were detected in the entire transplanted area. The results demonstrate that myoblasts can be transplanted in uremic mice, and that myoblast gene transfer can achieve sufficient and sustained delivery of functionally active EPO to correct anemia associated with renal failure in mice.