Background: This study proposed to examine the possibility of homing of bone marrow derived-mesenchymal stem cells after allograft transplantation in irradiated and healthy bone marrows.

Materials and Methods: 65 rats were divided into 13 groups (1 healthy and 12 irradiated). Mesenchymal stem cells were isolated from femoral bone marrow of male rats. The cells were cultured under morphological observations, differentiation tests and immunocytochemistry staining. Then, the mesenchymal cells were injected to the tail vein of the healthy and irradiated (7Gy gamma ray) female rats. During defined time gaps after injection, the transplanted rats were killed and their isolated bone marrow was cultured. DNA of the cultured cells was extracted and was amplified by PCR with specific primers for chromosome Y (SRY). Finally, the PCR products were analyzed on gel electrophoresis.

Results: Morphological observations and, differentiation and immunocytochemistry tests conformd that the isolated cells were mesenchymal stem cells. PCR results for the healthy and irradiated rats in all time gaps after transplantation were negative indicating that male mesenchymal stem cells were failed to home in bone marrow of transplanted female rats.

Conclusion: We concluded that due to low number of the injected mesenchymal stem cells or trapping of the cells in other organs Implantation the cells in bone marrow was not considerably detectable