Objective:In order to further reveal the mechanism of hematopoietic injury among people infected with HIV-1, The effect of HIV-1 Tat protein on hematopoiesis support function of bone marrow mesenchymal stem cells(BMSC) was researched. Methods:The bone marrow mesenchymal stem cells were primary cultured and their characters were identified by detecting differentiation potential and immune phenotype. Hematopoietic stem cells (HSC) were sorted with immunomagnetic beads and the purity were detected with flow cytometry. As the feeder layer, the control BMSC (BMSCCon) and the experiment BMSC which have been added HIV-1Tat protein into the medium for culturing 20 days (BMSCTat) were respectively co-cultured with HSC and divided into six groups. Then, a series of detections were carried out, the total numbers of hematopoietic cells were counted, hematopoietic cells clonogenic ability were assayed, hematopoietic growth fator mRNA expression of BMSCCon and BMSCTat were detected with RT-PCR, GM-CSF and IL-6 concentration in the condition medium of BMSCCon and BMSCTat were detected with ELISA. Results:Identification results show that the BMSC were successfully cultured.The purity of HSC sorted by immunomagnetic beads can reach more than 95%. The six groups were compared with each other and the results showed that both the total numbers of hematopoietic cells and the total numbers of hematopoietic cell colony in the groups when BMSCTat were as the feeder layer were significantly less than those in the groups when BMSCCon were as the feeder layer. The hematopoietic growth fator mRNA expression of BMSCTat were significantly weaker than that of BMSCCon. The GM-CSF and IL-6 concentration in the condition medium of BMSCTat were significantly lower than that of BMSCCon. Conclusions:The HIV1 Tat protein was confirmed to inhibit the hematopoiesis support function of bone marrow mesenchymal stem cells.