ABSTRACT
Limited donor-cell engraftment to the injured tissue restricts therapeutic efficacy of stem cell transplantation. Herein, we proposed an alternative strategy by using in utero transplantation (IUT) to create mixed-chimerism environment in recipients and to facilitate donor-cell engraftment followed by postnatal secondary boost with the same cells. Mouse bone marrow stromal cells (BMSCs) were used as the xenogenic donor cells and given into rat fetus as an early exposure of IUT treatment. The engraftment potential was analyzed for the presence of BMSCs by flow cytometry or PCR in recipient tissues. The function of a second boost of mouse BMSCs, in terms of cardioprotection, was tested by given 1×106 cells to rat IUT hearts with ischemia/reperfusion (IR) injury that was induced by a 45 min of left coronary ligation and released for 72 h. Mouse BMSCs demonstrated an immunosuppressive effect when mixed with mouse or rat lymphocytes. IUT treatment only caused few BMSCs engrafted to fetal (embryonic day 20) and adult (4 weeks after birth) rat organs including heart, but engraftment was increased in hearts of the IUT rats after second boost. This was coincided with attenuation of cardiac injury caused by IR. Interestingly, an up-regulation of CXC chemokine receptor type 4 (CXCR4) was seen when BMSCs were exposed to hypoxia. This indicates that enhanced engraftment of mouse BMSCs to post-ischemic rat hearts possibly is dependent on CXCR4. Moreover, results of flow cytometry demonstrated that the presence of CD34⺠cells in rat IUT hearts with IR injury was increased. These observations suggest that enhanced engraftment of donor BMSCs to rat IR hearts by CXCR4 may recruit endogenous CD34⺠cells of recipients which in turn protects heart against IR. This also supports the notion of fetal preconditioning with BMSC enhances the efficiency of progenitor cell-mediated organ protection after a postnatal second boost in xeno-transplantation.
