Delivery of erythropoietin by encapsulated myoblasts in a genetic model of severe anemia.

BACKGROUND Existing animal models of anemia inadequately reflect the hematocrit usually present in chronic renal failure (CRF) patients and do not permit long-term treatment studies. The transgenic mouse strain 134.3LC (Epo-TAg(H)) displays a severe chronic anemia resembling that observed clinically during CRF, while displaying an active, normal life span. This phenotype makes it a particularly interesting mouse model for testing erythropoietin (Epo)-based gene transfer strategies. METHODS Ex vivo gene therapy was employed to administer mouse Epo to homozygous anemic Epo-TAg(H) mice. Encapsulated C(2)C(12) myoblasts genetically engineered to secrete 163 IU mouse Epo/10(6) cells/day were subcutaneously transplanted on the dorsal flank of the mice. Efficacy of delivered Epo was monitored by weekly measurements of animal hematocrit. RESULTS Most treated homozygous Epo-TAg(H) mice displayed only a transient rise in hematocrit before eventually decreasing to levels as low as 3%. Administering the immunosuppressor anti-CD4+ monoclonal antibody (mAb) to homozygous Epo-TAg(H) mice, beginning at the time of implantation, permitted a rise in hematocrit that remained stable at elevated levels in cases of continued immunosuppression. CONCLUSIONS Mice having the T antigen insertion in both Epo alleles appeared to develop an immune response to the natural mouse Epo delivered by encapsulated cells. By preventing this reaction using immunosuppression, we demonstrate that encapsulated myoblasts can deliver therapeutic doses of mouse Epo systemically and restore hemopoiesis in a genetic model of severe anemia.

[1]  E. Svensson,et al.  Long-term erythropoietin expression in rodents and non-human primates following intramuscular injection of a replication-defective adenoviral vector. , 1997, Human gene therapy.

[2]  P. Ratcliffe,et al.  Identification of the renal erythropoietin-producing cells using transgenic mice. , 1993, Kidney international.

[3]  P Aebischer,et al.  Continuous delivery of human and mouse erythropoietin in mice by genetically engineered polymer encapsulated myoblasts , 1998, Gene Therapy.

[4]  J. Leiden,et al.  Immune responses to transgene–encoded proteins limit the stability of gene expression after injection of replication–defective adenovirus vectors , 1996, Nature Medicine.

[5]  T. Stockley,et al.  Suppression of immunological response against a transgene product delivered from microencapsulated cells. , 1998, Human gene therapy.

[6]  H. Roberts,et al.  Current management of hemophilia B. , 1993, Hematology/oncology clinics of North America.

[7]  D. Trono,et al.  Lentivirus-mediated Bcl-2 expression in βTC-tet cells improves resistance to hypoxia and cytokine-induced apoptosis while preserving in vitro and in vivo control of insulin secretion , 1999, Gene Therapy.

[8]  L. Kedes,et al.  Myoblast transfer of human erythropoietin gene in a mouse model of renal failure. , 1995, The Journal of clinical investigation.

[9]  J. Salisbury,et al.  Iron metabolism in transgenic mice with hypoplastic anaemia due to incomplete deficiency of erythropoietin , 1997, British journal of haematology.

[10]  W. Jelkmann.  Erythropoietin: structure, control of production, and function. , 1992, Physiological reviews.

[11]  N. Déglon,et al.  A gene therapy approach to regulated delivery of erythropoietin as a function of oxygen tension. , 1997, Human gene therapy.

[12]  A. Clowes,et al.  Gene therapy for long-term expression of erythropoietin in rats. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[13]  W. Vainchenker,et al.  Sustained delivery of erythropoietin in mice by genetically modified skin fibroblasts. , 1995, Proceedings of the National Academy of Sciences of the United States of America.