The Level Of Receptor CXCR4 On Megakaryocyte And Its Ligand In Children With Idiopathic Throbocytopenic Purpura

Objective: chemokine receptor CXCR4 : and its ligand stromal-derived factor (SDF-1) have been paid increasing attention for their involvement in megakaryocytic hematopoiesis. It has been discovered in recent two years that they can induce mature and immature megakaryocytes (MKs) to migrate through bone marrow endothelial cell (BMEC) by increasing the affinity of MKs for BMEC. Thus MKs maturity and eventual release of platelet from MKs ensues. While maturity disturbance of MKs and impaired production of platelets have been regarded as the main pathogenesis of ITP, the mechanism of which still remains unclear. Therefore, a clear understanding of the levels of CXCR4 and SDF-1 within bone marrow in children with ITP will help us to elucidate further the mechanism of ITP as well as to provide direct theoretical evidence for predicting treatment effect andevaluating prognosis.Subjects and Methods:28 children with acute IIP 1.5-4ml bone marrow was aspirated from each case before treatment. Of 16/28 patients undergoing high-dose intravenous immunoglobulin (IVIgG) treatment, 10 cases sensitive to IVIgG and 6 cases insensitive to IVIgG were observed . Bone marrow was aspirated once more when patients with the treatment of IVIgG showed normal platelet counts. 12 healthy children as normal controls measurement of CXCR4 level on Mks: 1.5-3ml bone marrow was obtained into modified PBS, MKs were isolated by immunomagenetic beads, CXCR4 levels were determined by ABC kit measurement of SDF-1 in bone marrow plasma: 0.5 ml bone marrow was pipetted into sodium citrate tube, after centrifugation at 400g for 20 minutes, the plasma was collected and SDF-1 was determined by SDF-1 ELISA assay.Results: SDF-1 level in bone marrow plasma before treatment in 28 children with ITP, the mean of SDF-1 level was 0.32+ 7.05E-02, while in the normal control was 0.43+4.46E-02;in patients before and after treatment with IVIgG was 0.31+4.64E-02 and 0.42+ 4.32E-02 respectively. In refractory group, the mean of SDF-1 level was 0.31+4.13E-02.The SDF-1 level was significantly higher in normal controls than in patients before treatment (P<0.05); After treatment with HDIVIgG, the SDF-1 level markedly elevated compared with that before treatment, the difference is significant (P<0.05); There was no difference in SDF-1 level between patients after treatment with IVIgGand normal controls, nor was between refractory ITP and patients before treatment (P>0.05). (2) CXCR4 reactive intensity on MKs before treatment in 28 children with ITP, the mean of CXCR4 reactive intensity was 2.34+0.40, while in normal controls was 3.25 + 0.59, before and after treatment with IVIgG was 2.40 + 0.41 and 3.18+0.57 respectively, while in refractory group was 1.82 + 0.23. The CXCR4 intensity was much higher in normal controls than in patients before treatment (P<0.05). After treatment with HDIVIgG. the CXCR4 level increased significantly by comparison with that before treatment. There was no difference in CXCR4 reactive intensity between patients after treatment with HDIVIgG and normal controls (P>0.05), while in refractory group, it was dramatically lower than that in patients before treatment with IVIgG. (3) CXCR4-Positive cell ratio Before treatment in 20 children with ITP, the mean of CXCR4-positive ratio was 82.68 + 5.92%,while in normal controls was 94.08+4.66%;the mean level of positive rate of CXCR4 before and after treatment with IVIgG was 84.68 + 4.22% and 93.90 + 4.53%; in refractory group was 78.00+ 5.25%. It was much higher in normal controls than in patients before treatment with IVIgG. After treatment with HDIVIgG (P<0.05), the positive ratio increased significantly compared with that treatment with HDIVIgG and normal controls (P>0.05), while CXCR4-positive cell ratio in refractory group was dramatically lower than that in patients before treatment with IVIgG (P<0.05). (4)In normal controls the level of CXCR4 on MKs and SDF-1 level in bone marrow plasma werepositively correlated(r=0.735); the same result can be drawn in patientswith IIP before...