Characterization of vasoactive intestinal peptide on hematopoiesis

Vasoactive intestinal peptide(V1P) is reported to modulate immune responses. In this study, we evaluated the role of VIP in hematopoiesis. Stem cells isolated from cord blood was treated with VIP for up to 15 days. Cell sizes, CD4 1 expression and polyploidity was analyzed by flow cytometry. VIP increased cell sizes of stem cells, percentage of CD41 positive cells and polyploidities. VIP produced synergistic effects when co-treated with thrombopoietin(TPO), which is known to be a major cytokine responsible for megakaryocytopoiesis. These results indicates that VIP might be one of the regulator for megakyryocytopoiesis and the administration of VIP with TPO might have the potential of accelerating platelet recovery after chemotherapy or stem cell transplantation. Our results might also be applicable for the expansion of megakaryocyte progenitor cells in vitro. Introduction Vasoactive intestinal peptide(V1P) is a 28 amino acid neuropeptide that is widely distributed in mammalian tissues( 1). The name, VIP, was coined to describe its potent vasodilatory action in lung tissue(2). VIP function as a neurotransmitter, a hormone, and also as an immune regulator,(3) but, to our knowledge, a possible role in hematopoiesis has not been explored. Neuropeptide modulation of the immune response has been well documented(4,5). The effects of VIP, somatostatin, and substance P on immune functions are mediated via specific, high affinity receptors on both T and B lymphocytes as well as on monocytes(6-9). VIP modulates lymphocytes proliferation, IgA production, natural killer cell cytotoxicity, and lymphocyte migration. Recently, neuropeptides have been shown to regulate hematopoiesis( 10-1 1). Substance P regulates hematopoiesis by inducing the release of IL-3 and granulocyte-macrophage colony stimulating factor fkom bone marrow(BM) mononuclear cells( 10). Thrombopoietin(TP0) is considered to be the primary growth factor for regulating megakaryocytopoiesis and thrombopoiesis. In both mouse and human, TPO supports the differentiation and proliferation of megakaryocyte progenitor cells and it is essential for the complete maturation of megakaryocytes in vitro( 12). In the present study, we used a liquid culture system to facilitate flowcytometric analysis. TPO selectively stimulated the growth of megakaryocytic cells from CD34+ cord blood cells. We also demonstrate a new property of VIP and indicate that VIP is a new regulatory protein of normal megakaryocyte development. Materials and Methods Collection of cord blood (CB): Cord blood samples were aspirated in heparinized plastic syringes from the umbilical vein at normal delivery. Blood was collected in tubes containing heparin (1 0 U/ml) and was stored at 2-6 0 until processed within 24 hr after collection. , Purification of haemopoietic progenitor cells: After collection CB was separated by density centrifbgation over Percoll(Pharmacia, Sweden). The mononuclear cells(MNCs) were collected 0-7803-5729-9/99/$10.00