ABSTRACT
<p><b>OBJECTIVE</b>To investigate the role of tumor necrosis factor (TNF) alpha on the homing efficiency of hematopoietic stem/progenitor cells (HS/PC) into bone marrow and its mechanism.</p><p><b>METHODS</b>CFSE-labeled umbilical cord blood (UCB) CD34+ cells were transplanted into irradiated (control group) or combined with TNF alpha prepared (experimental group) BALB/c recipient mice. The distribution in peripheral blood, liver, lung and homing characteristics in bone marrow and spleen of UCB CD34+ cells, in BALB/c recipient mice were determined 20 hours after xenotransplantation by flow cytometry (FACS) and their homing efficiency was calculated. ELISA was used to measure serum SDF-1 alpha level. CXCR4 expression levels of on UCB CD34+ cells were assessed by FACS pre-/post-manipulation with TNF alpha. SDF-1 alpha expression level in bone marrow and spleen was tested by immunohistochemistry.</p><p><b>RESULTS</b>UCB CD34+ cells mainly home into recipient mice bone marrow and spleen; The homing efficiency in experimental group bone marrow [(0.65 +/- 0.13)%] was significantly higher than that in control ones [(0.30 +/- 0.09)%, P < 0.01], whereas the homing efficiency in experimental group spleen was dramatically lower than that in control ones (P < 0.01); Treatment with TNF alpha did not affect recipient serum SDF-1 alpha level; After 18 hours co-cultured with TNF alpha, the CXCR4e expression level on UCB CD34+ cells was similar to that on fresh ones; TNF alpha treatment induced significantly higher SDF-1 alpha expression on osteoblastic and stromal cells in bone marrow, and reversed spleen SDF-1 alpha gradient that was originally favorable for CD34+ cells homing.</p><p><b>CONCLUSION</b>TNF alpha enhances the homing efficiency of HS/PC via up-regulating SDF-1 alpha gradient in bone marrow, and might be an useful enhancer for HS/PC homing in clinical practice.</p>
Subject(s)
Animals , Female , Humans , Mice , Antigens, CD34 , Bone Marrow , Cell Movement , Cell Separation , Chemokine CXCL12 , Metabolism , Fetal Blood , Cell Biology , Hematopoietic Stem Cell Transplantation , Hematopoietic Stem Cells , Allergy and Immunology , Metabolism , Mice, Inbred BALB C , Receptors, CXCR4 , Metabolism , Transplantation Conditioning , Transplantation, Heterologous , Tumor Necrosis Factor-alpha , PharmacologyABSTRACT
Myeloid differentiation factor MyD88 is a critical adaptor molecule that integrates and transduces intracellular signals in inducing the differentiation of dendritic cells (DCs).The domain regions within MyD88 was searched,it could potentially affect the function of dendritic cells and found that MyD88 aa155-171 motif not only regulate the activity of transcription factor NF-?B, but also control the production of cytokines and expression of costimulatory molecules. Indeed, aa155-171 motif deleted type MyD88 (MyD88155-171) transfected RAW264.7 cells exhibited the reduced NF-?B and AP-1 activity and interrupted the expression of CD86 and B7H1. Meanwhile, lower level expression of cytokines such as IL-12,IFN-? were also observed by means of cytokine array in MyD88-/-DC trasfected with MyD88155-171 as compared to the MyD88 transfected cells. Thus, aa155-171 motif inside MyD88 could affect the expression of costimulatory molecules, production of cytokines and transduction of Toll like receptor signal pathway, suggesting that this motif may play an important role in regulating responses of innate immune system.