Bone marrow stromal cells (MSC) are attractive candidates for developing cell therapies for central nervous system (CNS) disorders. They can be easily obtained, expanded in culture, and promote modest functional recovery following transplantation into animal models of injured or degenerative CNS. While syngeneic MSC grafts can be used efficiently, achieving long-term survival of allogeneic MSC grafts has been a challenge. We hypothesize that improved graft survival will enhance the functional recovery promoted by MSC. To improve MSC graft survival, we tested two dosages of the immune suppressant cyclosporin A (CsA) in an allogeneic model. Syngeneic transplantation of MSC where cells survive well without immune suppression was used as a control. Sprague-Dawley rats treated with standard dose (n = 12) or high-dose (n = 12) CsA served as allogeneic hosts; Fisher 344 rats (n = 12) served as syngeneic hosts. MSC were derived from transgenic Fisher 344 rats expressing human placental alkaline phosphatase and were grafted into cervical spinal cord. Animals treated with standard dose CsA showed significant decreases in allograft size 4 weeks posttransplantation; high CsA doses yielded significantly better graft survival 4 and 8 weeks posttransplantation compared to standard CsA. As expected, syngeneic MSC transplants showed good graft survival after 4 and 8 weeks. To investigate MSC graft elimination, we analyzed immune cell infiltration and cell death. Macrophage infiltration was high after 1 week in all groups. After 4 weeks, high-dose CsA and syngeneic animals showed significant reductions in macrophages at the graft site. Few T lymphocytes were detected in any group at each time point. Cell death occurred throughout the study; however, little apoptotic activity was detected. Histochemical analysis revealed no evidence of neural differentiation. These results indicate that allogeneic transplantation with appropriate immune suppression permits long-term survival of MSC; thus, both allogeneic and syngeneic strategies could be utilized in devising novel therapies for CNS injury.
INTRODUCTIONaxonal regeneration and survival of host neurons and glia (12,13,22,45,49,51). MSC are multipotent adult stem cells derived from Cell transplantation has emerged as a promising therapeutic approach for CNS disorders, including spinal bone marrow, with the capacity to differentiate along various mesenchymal lineages (37). They have also been cord and traumatic brain injury. Specialized cell types and a variety of stem cells have been transplanted into shown to promote functional recovery in animal models of spinal cord injury (SCI) (2,14,19,35,36,49), as well experimental models of spinal cord and brain injury, including Schwann cells [for review see (8)], olfactory enas brain disorders and injury [for review see (13)]. In addition, some studies showed that a small number of sheathing glia [for review see (5,41)], neural stem cells [for review see (9,43)], and bone marrow stromal cells MSC transplanted into the adult CNS may differen...