PS1568 MAGIC‐TT (MAGNETISM‐INDUCED CELL TARGET TRANSPLANTATION) IMPROVES THE EFFECT OF INTRA‐BONE MARROW TRANSPLANTATION: FASTER HEMATOPOIETIC RECONSTITUTION AND BETTER SURVIVAL IN MURINE MODEL

Background: Based on 10 years’ research, we have established MagIC‐TT (Magnetism‐induced cell target transplantation) platform to enhance target transplantation of therapeutic cells, such as hematopoietic stem cell (HSC) and mesenchymal stem cell to bone marrow (Blood 2010 116: 2625; 2014 124: 2416; 2015 126:5404 & 5409; 2017 130: 4952 & 5447). To increase the HSC homing, many researches of intra‐bone and intra‐artery HSC transplantation have been carried out, but the effect is limited (According to our research, most HSCs were flushed to peripheral circulation in minutes after injection). By the platform of MagIC‐TT, if a proper magnetism (intensity, direction, action time, shape, magnetic material type, magnet field) was applied to bone marrow, HSCs were retained in bone marrow successfully. Aims: To study the effect and mechanism of hematopoietic reconstitution promotion and the reduction of side effects by MagIC‐TT in autologous and allogeneic murine transplantation model. Methods: 1) In vitro study: (a) Bone marrow mononuclear cells (BMNCs) were magnetized with CD45‐microbead antibody or SPIO‐N‐Au (superparamagnetic iron oxide‐nanoparticles‐Au). Then magnetized cells were separated by MACS column and analyzed for morphology, proliferation and apoptosis. (b) Under proper magnetism, the target migration and proliferation ability of magnetized/unmagnetized BMNCs were studied by Transwell and imitated micro‐blood‐vessel. 2) In vivo study: C57BL/6‐GFP→C57BL/6 autologous transplantation and C57BL/6‐GFP→BALB/c allogeneic transplantation after lethal irradiation with different doses of donor BMNCs were used (see Table 1). Donor cells were intra‐bone marrow injected into unilateral femur by own‐made syringe (Patent. CN201620090904) with/without magnetism applied (MagIC‐TT groups/Non‐MagIC‐TT groups). Mice survival, severity of GvHD, blood routine test, eGFP + % by flow cytometry, duplex real‐time PCR (Patent CN101701253B), histological analysis after semi‐solid decalcification (SSD, Patent CN101785876A) were performed. Results: 1) In vitro study: (a) The magnetization rates of BMSCs was (80.67 ± 3.06)%. No difference in cell morphology, proliferation and apoptosis. (b) Under proper magnetism, the migration ability of magnetized cells was greatly improved and proliferation ability was reserved. Much more magnetized cells grew within imitated micro vessel (black arrow, Figure 1) and in the area with magnetism. More BMNCs migrated through the membrane of transwell with Matrigel in MagIC‐TT group, which was 177.67 ± 4.04 vs 5 ± 1 ( P  < 0.001). 2) In vivo study: The results of hematopoietic reconstitution see Table 1. On d 15 , the survival rate was much better in three allogenic MagIC‐TT groups (P≤0.003), while GvHD (body weight, back arching, fur losting, diarrhea etc. ) in non‐MagIC‐TT groups were more severer (with more donor cells spreading to other such as lung, gut). More eGFP + % was detected in the injected femurs of MagIC‐TT groups 24 h after transplantation (3.73 ± 0.46 v.s. 0.62 ± 0.38, P <0.0001). Figure 2 shows the distributions of BMNCs in organs of each group. SSD and confocal observation displayed the details of interaction among donor cells, recipient cells and micro‐environment. Summary/Conclusion: MagIC‐TT improved the effect of intra‐bone HSC transplantation with faster hematopoietic reconstitution and less GvHD, such platform also helpful for solving the “off‐target” problem in cell therapy as CAR‐T.