Abstract
Interleukin (IL)-31 receptor (R), also called gp130-like monocyte-receptor (GLM-R; Ghilardi et al. J. Biol. Chem.277:16831, 2002) is related to gp130 (~25% homology), and G-CSF-R (~24%). Its signaling activates STAT3 and STAT5. IL-31 is a four helix bundle cytokine preferentially produced by T helper 2 cells. Nothing is known of the possible hematopoietic effects of IL-31R and IL-31. However, since: IL-31 signals through a receptor composed of IL-31RA and Oncostatin M R (Dillon et al. Nature Immunol. 5:752,2004), Oncostatin M is implicated in homeostasis of myeloid progenitor cells (Broxmeyer et al. Immunity.16:815, 2002), and STAT3 and 5 are implicated by a number of groups in cytokine regulation of hematopoiesis, we hypothesized that the IL-31/IL-31R axis would be involved in regulation of hematopoiesis. We first compared myeloid progenitor cell (MPC: CFU-GM, BFU-E, and CFU-GEMM) numbers and cycling status in marrow and spleen of IL-31R −/− vs. littermate control mice (+/+) using a combination of Epo, SCF and PWMSCM to stimulate in vitro the cells taken from these mice. IL-31R −/− mice had significantly decreased numbers of MPC per femur (~51%) and spleen (~36–45%) with significantly decreased MPC cycling status in marrow (% MPC in S-phase: 0–3% in IL-31R −/− vs. 41–53% in +/+ mice). MPC in spleen of IL-31 −/− and +/+ were both in a slow or non cycling state (0–3% in S-phase). In contrast to CFU-GM from +/+ mice, CFU-GM from IL-31R −/− mice demonstrated little or no synergistic response to combined stimulation in vitro with GM-CSF or IL-3 with either SCF or Flt3-ligand (FL). This translated to decreased absolute numbers per femur of GM-CSF+SCF-, GM-CSF+FL-, IL-3+SCF-, and IL-3+FL- responsive CFU-GM in IL-31R −/− mice. However, there were no significant differences between GM-CSF- or IL-3- responsive CFU-GM per femur between IL-31R −/− vs. +/+ mice suggesting effects on immature subsets of MPC. Recombinant IL-31 was assessed for effects in vitro. IL-31, at concentrations up to 100ng/ml, did not stimulate colony formation by marrow MPC, nor did it enhance or suppress colony formation stimulated by GM-CSF, Epo, Epo+SCF, or Epo+SCF+GM-CSF. However, IL-31 did enhance survival of MPC subjected to delayed growth factor addition in a manner similar to, but not as potent as, that of SDF-1/CXCL12. IL-31 manifested no chemotaxis activity for +/+ MPC, and IL-31R −/− and +/+ MPC were equally responsive to the chemotactic effects of SDF-1/CXCL12. These results suggest that the IL-31R in vivo acts to positively regulate numbers and cycling of immature subsets of MPC in the marrow, and that IL-31 has survival enhancing effects on MPC in vitro.
Transgenic Expression of Stromal Cell-Derived Factor-1/CXC Chemokine Ligand 12 Enhances Myeloid Progenitor Cell Survival/Antiapoptosis In Vitro in Response to Growth Factor Withdrawal and Enhances Myelopoiesis In Vivo
