| Leukemia is a malignant disease of hematopoietic tissue, which has significant feature of malignant tumors: unlimited capability to grow, failed to differentiate into functional mature cells, easy invasion into the surrounding tissue to distant metastasis. Induced differentiation is a new potential treatment for large tumors. Differentiation-inducers induce tumor cells to become normal or near normal cells, reversing their proliferation, invasion and metastasis of malignant phenotype to cure cancer. All-trans retinoic acid(ATRA) is the first drug that successfully applied to induce differentiation of leukemia that can specifically induce acute promyelocytic leukemia(APL) cells to differentiate toward mature myeloid cells. HL-60 cell line is a model system for studying APL(acute promyelocytic leukemia) cell differentiation. The effect of all-trans retinoic acid-induced differentiation of HL-60 cell line is similar to acute promyelocytic leukemia(APL) and the clinical trials of all-trans retinoic acid-induced APL are based on the results of HL-60 cell line in vitro.In addition,the number of white blood cells in leukemia patients is large, but the white blood cells are immature naive cells that do not have immune properties, so leukemia patients have an increased risk of infection and always accompanied with inflammatory response. As we know inflammatory response is a complex and multi-step process and needs to overcome the wall shear force that the blood vessel flow triggered under physiological conditions, which involves the phenomenon of cell rolling adhesion and migration between the extracellular matrix. Our research focused on the effects of all-trans retinoic acid(ATRA)-induced HL-60 cell line: proliferation, differentiation, rolling adhesion. The research aims to deepen the understanding of the mechanisms of immune response in the perspective of biomechanics, provide useful information and new ideas for new drug design and cancer treatment.Firstly, HL-60 cell line was treated with different gradients concentration of all-trans retinoic acid. Cells number, morphological changed, biochemical aspect and functional aspect were tested to establish the best model of the induced differentiation. The results showed the growth of HL-60 cell line which was induced by 1 × 10-6M all-trans retinoic acid was inhibited, the ability of HL-60 cell reduction was increased and NBT positive rate( Cell differentiation rate) was close to 90%.Then, the functional of P-selectin-mediated cell initial rolling adhesion was tested by parallel plate flow chamber system. By comparing with controlled experiments,It was tested that the specific interaction of P-selectin and the cell molecule on the HL-60 cell surface mediate the cell initial rolling adhesion. Furthermore, we found that 1% BSA can efficiently block the non-specific adhesion between HL-60 cell and flow chamber substrate but not effect the specific adhesion between HL-60 cell and P-selectin. Thus, we used this method to functionalize flow chamber substrate in the subsequent experiments.Finally, we observed and researched 1×10-6M all-trans retinoic acid-induced HL-60 cell rolling adhesion under various shear stresses(0.1-0.3dyn/cm2) by parallel plate flow chamber system. The experimental results demonstrated that the exposure time of ATRA and shear stresses(0.1-0.3dyn/cm2) have significant impactson the HL-60 cell rolling adhesion. Under the same shear stress with the increase of the exposure time, HL-60 cell rolling speed was gradually reduced. Under the same exposure time, with the increase of shear stress, HL-60 cell rolling speed increased after the first decreased. Furthermore, we found the trend of the cell frational stop time was opposite to cell rolling speed trend. Therefore, the regulation of the exposure time of ATRA and shear stress on the HL-60 cell rolling speed was achieved mainly by regulating the cell frational stop time. |
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