Experimental study of low dose irradiation for treatment of immuno-mediated aplastic anemia in mice / 中国实验血液学杂志

As the lymphocytes of immuno-mediated aplastic anemia (IMAA) are in active state, and the hematopoietic stem cells are in silence, this study was aimed to design a new strategy to treat IMAA. To utilize the difference of radiosensitivity between active lymphocytes and silent hematopoietic stem cells, the animals suffered from IMAA were treated with a single low dose of irradiation, killing the active lymphocytes to release its suppression to hematopoietic stem cells without injuring the hematopoietic stem cells. Therefore, the hematopoiesis can be restored. Experiments were completed in IMAA mouse model. At day 4 after making IMAA, the model mice were giren total body irradiation of 150 cGy, the non-treated model mice and normal mice irradiated with 150 cGy were used as control. The survive time and survive rate of mice, blood picture, the account of nucleated cell of bone marrow, and pathological changes of bone marrow and lymphoid tissues of each group mice were observed. The results were as follows: (1) Survive rate of IMAA mice in non-treated group was 12.5%, the average survive time was 27.4 +/- 13.4 days. 100% of IMAA mice in irradiation-treated group survived over 60 days. The mice of irradiation control group all survived. (2) The account of WBC of IMAA mice in non-treated group dramatically decreased until to die, and in the irradiation-treated group it was gradually increased since the 10th day after treatment and close to normal level at the 28th day. (3) The RBC hematocrit of IMAA mice in non-treated group progressively decreased at day 14, and IMAA mice of irradiation-treated group gradually recovered closely to normal level after slightly fall at day 14, similar to the mice of irradiation control group. (4) The account of nucleated cells of bone marrow in non-treated IMAA mice dramatically decreased, and in the IMAA mice of the irradiation-treated group it was rapidly increased following transient fall, and restored to normal. (5) Pathological observations showed that the bone marrow and spleen of non-treated IMAA mice demonstrated typical aplastic anemia pattern, including bone marrow failure, marked splenatrophy, but the bone marrow and lymphoid tissues in the IMAA mice of irradiation-treated group were recovered to normal at day 28 after treatment. It is concluded that the low dose of irradiation displayed a significant therapeutic effect to IMAA mice, their hematopoisis could be completely restored to normal. The mechanism of therapeutic effect may contribute to low dose of irradiation killing the immunocompetent lymphocytes, therefore, suppressing hematopoiesis. The experiment results not only set up a new strategy for IMAA treatment, but also provided a clue to study the mechanism of IMAA.

Activation of auto-mesenchymal stem cells of skeletal muscle by bone morphogenetic protein for rescuing bone marrow failure / 中国医学科学院学报

<p><b>OBJECTIVE</b>To explore the effect of bone morphogenetic protein (BMP) to activate mesenchymal stem cells of skeletal muscle for rescuing bone marrow failure.</p><p><b>METHODS</b>The study was performed on lethal rat acute aplastic anemia model induced by combined 5-fluorouracil (5-FU) and busulfan. The rh-BMP-2 was implanted into the thigh muscle of the rats at 3 days before aplastic anemia was induced. In the control group the rats were implanted with agar into the thigh muscle. The blood picture, pathologic changes and the mortality in two groups were observed. At the same time, rh-BMP-2 were implanted into the thigh muscle of normal Kun-min mice for dynamic control observation of the implantation local morphological changes, colony forming units-spleen (CFU-S) and stem cell growth factor (SCF) expression of the stroma cells of ectopic ossicles induced by BMP.</p><p><b>RESULTS</b>At 7 days after BMP implantation in the mice the mesenchymal cells around BMP in muscle proliferated, and appeared in bone marrow to form an ectopic ossicles. The SCF expression of stroma cells in ectopic ossicles were higher than that of self-bone marrow. 56.3% of BMP-treated aplastic rats were survived over 3 months and its hematopoiesis was completely reconstituted and the histo-morphological picture of the spleen and bone marrow were recovered to normal. But in the control group only one of 23 rats was survived, the remainder died of hematopoietic failure.</p><p><b>CONCLUSIONS</b>BMP-implantation into the skeletal muscle could rescue the bone marrow hematopoietic failure. The mechanism might be related to the BMP activated auto-mesenchymal cells of skeletal muscles to direct hematopoietic cell differentiation. In our hands it might create a new pathway for utilization of auto-muscle derived mesenchymal cells to reconstitute hematopoiesis.</p>

Study of Low Dose Irradiation Enhancing the Effect of Chemotherapeutic Agents against Leukemia and Its Mechanism / 中国实验血液学杂志

For effectively enhancing the anti-leukemia effect of chemotherapeutic agents, and meanwhile decreasing the side effect of these agents, the study has been made to explore the synergistic effect of low dose irradiation (LDI) combined with Ara-C on murine leukemia and its mechanism. Firstly, an optimal scheme of low dose total body irradiation combined with Ara-C was established in L615 leukemia (T lymphocytic leukemia) mouse model. The machanism of the enhancing effect was explored by patho-morphological observation, examination of residual leukemia cells, the expression of GM-CSF on the surface of marrow stromal cells and in the bone marrow cultural supernatants. The results showed that the optimal scheme was 300 cGy irradiation at 4 days after inoculation of leukemic cells followed by Ara-C 30 mg/kg x 3 days in an interval of 1, 2 or 3 days after irradiation. The mean survival time of the L615 leukemia mice in LDI + Ara-C combined treatment groups was longer than that of control groups. The percentage of long-term survival mice (> 30 days) was the highest (58% - 72%), too. 17% of the mice were be cured. The numbers of blood leukocytes and marrow nucleated cells were transiently decreased in combined treatment group, and then recovered rapidly. Slight myelosuppression and marrow sinus dilation and congestion were seen after 300 cGy irradiation. The expression of GM-CSF either on the stromal cells or in marrow cultural supernatant after irradiation increased strikingly (P < 0.05). Therefore, LDI combined with Ara-C possesses synergistic effect. The mechanism is possibly related to three facts: LDI could increase the permeability of bone marrow sinus; LDI could promote marrow stromal cells to produce some cytokines (such as GM-CSF, etc.) which drive leukemia cells into cell cycle to make the cells more sensitive to chemotherapeutic agents; and LDI could augment Ara-C-induced cytotoxicity through the mechanism of apoptosis.