title: Constant subcutaneous infusion of rhIL-11 in mice: efficient delivery enhances biological activity.
abstract: Previous studies have shown that subcutaneous (SC) bolus administration of recombinant human interleukin-11 (rhIL-11) stimulates megakaryocytopoiesis and increases peripheral platelet counts in naive mice. This study was designed to determine whether administration of rhIL-11 by constant SC infusion altered either the magnitude of the nature of the hematologic response. Female C57BL/6 mice were implanted subcutaneously with 7-day Alzet mini-osmotic pumps containing either rhIL-11 with 0.5% homologous mouse serum (delivery rate of 250 microg/kg/d) or vehicle alone. Mice were sacrificed on days 3, 7, 10, and 13 after pump implantation, and the hematopoietic response was compared to mice receiving an equivalent dose of rhIL-11 administered by SC injection (250 microg/kg/d, 7 days) or vehicle controls. Subcutaneous injection of rhIL-11 resulted in a significant increase in peripheral platelet counts with a maximum platelet increase of 44% over controls observed on day 7 of the study. Platelet counts subsequently declined (24% by day 10) returning to control values by day 13. The increase in peripheral platelet counts was accompanied by an increase in reticulated platelets on day 7 and a shift to higher ploidy bone marrow megakaryocytes on days 3 and 7. Compared to SC injection, both the magnitude and duration of the platelet increase were significantly enhanced following continuous SC infusion of rhIL-11. Maximum platelet counts were detected on day 10 (115% above vehicle controls), and platelets remained significantly elevated on day 13 (84%), 6 days after rhIL-11 administration had stopped. Consistent with the platelet response, the modal ploidy of bone marrow megakaryocytes was shifted from 16N to 32N on days 3 and 7, with increases in 32N megakaryocytes still apparent on days 10 and 13. There was also a significant increase in reticulated platelets detected in the peripheral blood on days 3, 7, and 10 compared to mice administered rhIL-11 by SC injection, The changes in reticulated platelets and bone marrow megakaryocyte ploidy are consistent with the increased and prolonged platelet response following SC infusion of rhIL-11. In addition to the effects observed on peripheral platelet counts, constant SC infusion of rhIL-11 dramatically enhanced splenic hematopoietic activity, increasing spleen weight and cellularity as well as splenic megakaryocyte, erythroid, granulocyte, and macrophage progenitors compared to mice receiving rhIL-11 by SC injection.
authors.affiliation: Preclinical Biology, Genetics Institute, Cambridge, MA 02140, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Leonard
authors.forename: T Y
authors.initials: TY
authors.lastname: Neben
authors.forename: M K
authors.initials: MK
authors.lastname: Kozitza
authors.forename: C M
authors.initials: CM
authors.lastname: Quinto
authors.forename: S J
authors.initials: SJ
authors.lastname: Goldman
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000187:drug effects; D001854:Bone Marrow Cells; D016207:Cytokines / Q000502:physiology; D005260:Female; D006410:Hematopoiesis / Q000187:drug effects*; D007260:Infusion Pumps; D007279:Injections, Subcutaneous; D017370:Interleukin-11 / Q000008:administration & dosage* / Q000494:pharmacology; D008533:Megakaryocytes / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D010976:Platelet Count / Q000187:drug effects; D011003:Ploidies; D051381:Rats; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D016207:Cytokines; D017370:Interleukin-11; D011994:Recombinant Proteins