Influence of chronic L-DOPA treatment on immune response following allogeneic and xenogeneic graft in a rat model of Parkinson's disease

Abstract

Although intrastriatal transplantation of fetal cells for the treatment of Parkinson's disease had shown encouraging results in initial open-label clinical trials, subsequent double-blind studies reported more debatable outcomes. These studies highlighted the need for greater preclinical analysis of the parameters that may influence the success of cell therapy. While much of this has focused on the cells and location of the transplants, few have attempted to replicate potentially critical patient centered factors. Of particular relevance is that patients will be under continued L-DOPA treatment prior to and following transplantation, and that typically the grafts will not be immunologically compatible with the host. The aim of this study was therefore to determine the effect of chronic L-DOPA administered during different phases of the transplantation process on the survival and function of grafts with differing degrees of immunological compatibility. To that end, unilaterally 6-OHDA lesioned rats received sham surgery, allogeneic or xenogeneic transplants, while being treated with L-DOPA before and/or after transplantation. Irrespective of the L-DOPA treatment, dopaminergic grafts improved function and reduced the onset of L-DOPA induced dyskinesia. Importantly, although L-DOPA administered post transplantation was found to have no detrimental effect on graft survival, it did significantly promote the immune response around xenogeneic transplants, despite the administration of immunosuppressive treatment (cyclosporine). This study is the first to systematically examine the effect of L-DOPA on graft tolerance, which is dependent on the donor-host compatibility. These findings emphasize the importance of using animal models that adequately represent the patient paradigm.

Keywords: Dyskinesia; Immune response; L-DOPA; Parkinson’s disease; Stem cell; Transplant.

Fig. 1

Experimental design. (a) Timeline of the study. (b) Treatment and transplantation received by the animals for each group. The group were named after the treatment they received in treatment phase 1 and 2: S = saline, L = L-DOPA thus, SS group received saline in treatment phase 1 and 2, SL group received saline in treatment phase 1 and L-DOPA in treatment phase 2, LS received L-DOPA in Treatment phase 1 and saline in treatment phase 2 and LL received L-DOPA in treatment phase 1 and 2. ^*These groups originally numbered 12 animals but some developed tumors unrelated to the experiment, so had be removed from the study.

Fig. 2

Graft survival and function. (a) The data represent the total number of tyrosine hydroxylase (TH) positive cell bodies present in the transplanted striatum. (b–d) Pictures are representative of each type of graft (these 3 pictures have been selected from the L-DOPA naïve group SS but all the grafts looked similar within each transplant group). (e) Amphetamine-induced rotational behavior. The data represent the relative number of ipsilateral turns performed over 90 min, 10 weeks after transplantation. All data are presented as mean ± SEM for each group, total n = 118.

Fig. 3

L-DOPA induced-dyskinesias. Average of abnormal involuntary movement (AIMs) scores rated before and after striatal transplantation (dotted line) of rat VM (middle panel) mouse VM (bottom panel) or sham surgery (top panel). The different treatments for each phase (I and II) are color-coded: white for saline or grey for L-DOPA. Data presented as mean ± SEM, ^*p < 0.05 compare to last trial prior-transplant.

Fig. 4

Immune response. (a) Comparative number of Ox42 positive cells observed around the graft. (b–e) Representative pictures of microglia immunochemistry staining (Ox42) of the xenografted area. (f) Total number of leukocytes in the grafted striatum and representative pictures of the xenografted striatum (g-j; CD45 staining). Scale bars: 100 μm. (a, f) Data are presented as mean ± SEM, n = 118, ^*p < 0.05, ^**p < 0.01,^***p < 0.0001, relative to the corresponding SS group. (k) Average of CD4 and CD8 positive cells observed in the striatum of xenotransplanted animals, which received L-DOPA through both treatment phases. Presented as mean ± SEM, n = 12, ^*p < 0.05.

Fig. 5

Chronic cyclosporine A treatment. There was no effect of CSA the development of L-DOPA induced dyskinesia (a) and rotational behavior (b).