INTRACEREBRAL CO-TRANSPLANTATION OF LIPOSOMAL TACROLIMUS IMPROVES XENOGRAFT SURVIVAL AND REDUCES GRAFT REJECTION IN THE HEMIPARKINSONIAN RAT A. Y. ALEMDAR, a D. SADI, a V. MCALISTER b AND I. MENDEZ a,c * a Neural Transplantation Laboratory, Department of Anatomy and Neu- robiology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3A7 b Division of General Surgery, Department of Surgery, Dalhousie Uni- versity, Halifax, Nova Scotia, Canada B3H 3A7 c Division of Neurosurgery, Department of Surgery, Queen Elizabeth II Health Sciences Centre, Halifax Infirmary, Dalhousie University, 3806- 1796 Summer Street, Halifax, Nova Scotia, Canada B3H 3A7 Abstract—Immunosuppression remains a key issue in neural transplantation. Systemic administration of cyclosporin-A is currently widely used but has many severe adverse side effects. Newer immunosuppressive agents, such as tacroli- mus (TAC) and rapamycin (RAPA), have been investigated for their neuroprotective properties on dopaminergic neurons. These drugs have been formulated into liposomal prepara- tions [liposomal tacrolimus (LTAC) and liposomal rapamycin (LRAPA)] which retain these neuroprotective properties. Due to the slower release of the drugs from the liposomes, we hypothesized that co-transplantation of either LTAC or LRAPA within a xenogeneic cell suspension would increase cell survival and decrease graft rejection in the hemiparkin- sonian rat, and that a combination of the two drugs may have a synergistic effect. 6-Hydroxydopamine-lesioned rats were divided to four groups which received intra-striatal trans- plants of the following: 1) a cell suspension containing 400,000 fetal mouse ventral mesencephalic cells; 2) the cell suspension containing 0.63 M LRAPA; 3) the cell suspen- sion containing a dose of 2.0 M LTAC; 4) the cell suspen- sion containing 2.0 M LTAC and 0.63 M LRAPA. Functional recovery was assessed by amphetamine-induced rotational behavior. Animals were killed at 4 days or 6 weeks post- transplantation, and immunohistochemistry was performed to look at the expression of tyrosine hydroxylase and major histocompatibility complex classes I and II. Only the group receiving LTAC had a decrease in rotational behavior. This observation correlated well with significantly more surviving tyrosine hydroxylase immunoreactive cells compared with the other groups and significantly lower levels of immunore- jection as assessed by major histocompatibility complex class I and II staining. This study has shown the feasibility of using local immunosuppression in xenotransplantation. These findings may be useful in optimizing immunosuppres- sion in experimental neural transplantation in the laboratory and its translation into the clinical setting. © 2007 IBRO. Published by Elsevier Ltd. All rights reserved. Key words: neural transplantation, local immunosuppres- sion, Parkinson’s disease, rodent model of Parkinson’s dis- ease. Although the need for immunosuppression and findings of immune rejection in clinical trials using fetal dopaminergic cells in patients with Parkinson’s disease have been vari- able and controversial, it appears that there is some de- gree of allograft rejection following intracerebral transplan- tation (Kordower et al., 1997; Lopez-Lozano et al., 1997a,b). As there is a focus away from human fetal tissue, and toward alternative cell sources such as stem cells, resolving the issue of immunosuppression is of crit- ical importance. Cyclosporin-A (CsA) is currently the most widely used immunosuppressant drug in neural transplan- tation. However, the drug has many harmful systemic side effects which bring up the question as to whether the immunosuppressive treatment does more harm than good. Many alternatives to systemic immunosuppression with CsA in neural transplantation have been investigated, such as anti-interleukin 2 (IL-2) antibodies (Honey et al., 1990), anti-CD4 antibodies (Wood et al., 1996), and photody- namic therapy (Honey et al., 2000) to name a few. As well, local immunosuppression has been successfully at- tempted with the co-transplantation of testes-derived Ser- toli cells (Sanberg et al., 1996; Saporta et al., 1997). How- ever, a readily available, easy to titrate local immunosup- pressive drug may prove to be more advantageous and facilitate translation into the clinical setting. In recent years the neuroimmunophilin ligands have been investigated for their role in neural transplantation. Two key drugs have been tacrolimus (TAC) or FK-506, and rapamycin (RAPA) or sirolimus. In addition to their potent immunosuppressive effects, these drugs have also been found to have neuroprotective effects. Studies have shown that TAC increases the survival of dopaminergic cells both in culture and in grafting models in rodents (Castilho et al., 2000). As well, the drug increases the length of neurites extending from these cells (Costantini et al., 1998; Costan- tini and Isacson, 2000). RAPA on the other hand, has been found to increase the extent of neurite branching from *Correspondence to: I. Mendez, Division of Neurosurgery, Depart- ment of Surgery, Queen Elizabeth II Health Sciences Centre, Hali- fax Infirmary, Dalhousie University, 3806-1796 Summer Street, Halifax, Nova Scotia, Canada B3H 3A7. Tel: +1-902-473-7046; fax: +1-902-473-3343. E-mail address: ivar.mendez@dal.ca (I. Mendez). Abbreviations: Ab, antibody; ANOVA, analysis of variance; AP, antero- posterior; CsA, cyclosporin-A; DA, dopamine; DMEM, Dulbecco’s modified Eagle’s medium; DNase, deoxyribonuclease; DV, dorsoven- tral; FKBP, FK-binding protein; IL-2, interleukin 2; LRAPA, liposomal rapamycin; LRAPATAC, liposomal rapamycin/tacrolimus; LTAC, lipo- somal tacrolimus; MHC, major histocompatibility complex; ML, medio- lateral; PB, phosphate buffer; PBS, phosphate-buffered saline; RAPA, rapamycin; TAC, tacrolimus; TH, tyrosine hydroxylase; THir, tyrosine hydroxylase immunoreactive; VM, ventral mesencephalon; 6-OHDA, 6-hydroxydopamine. Neuroscience 146 (2007) 213–224 0306-4522/07$30.00+0.00 © 2007 IBRO. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.neuroscience.2007.01.006 213