The Effect of Fetal Mesencephalon Implants in Rats with 6-Hydroxydopamine Lesion of the Nigro-Striatum : Behavioral, Biochemical Immunohistochemical Study

ABSTRACT

Parkinson's disease most consistently involves pathologic changes in the substantia nigra, which is the major source of dopamine to the striatum. It has been shown that either fetal substantia nigra or adrenal medulla tissue implanted to the rat brain survives, produces dopamine, and improves behavioral abnormalities induced by deprivaion of the caudate nucleus of its dopaminergic innervation. Thus, grafts containing dopamine could be potential replacement for destroyed or damaged dopaminergic neurons in patients with Parkinson's disease. In the present study, authors administrated 6-hydroxydopamine into the right substantia nigra, and produced unilateral dopamine denervated Parkinson's experimental model using solid graft method and cell suspension implant, the results of these grafts were examined behaviorally, biochemically, immunohistochemically 3 months after grafting. In this study, a total of forty-five young(4 to 5 week old) rats were used and divided into three experimental groups-control group which underwent dopamine denervation without any grafting(15), solid graft group which was grafted fetal mesencephalon to the caudate-putamien(n=15) and cell suspension implant group which was grafted cell suspension fetal mesencephalon to the caudate-putamen(n=15). The apomorphine induced rotation test was performed at four weeks, eight weeks, twelve weeks after grafting. The dopamine concentration in the caudate-putamen was biochemically measured by High Performance Liquid Chromatography(HPLC) and immunohistochemically these grafts containing dopamine granules were stained by Avidin-Biotin immunoperoxidase staining with dopamine monoclonal antibody. The results were as follows ; 1) Behavioral testing was performed by apomorphine induced rotational test. A mean rotation number during the first five minutes following apomorphine injection was 40.0+/-.5 in control and 18.3+/-.9 in cell suspension implanted group at one month after grafting and these was more reduction of turning than that in solid graft group. The both graft groups demonstrated explicit reduction of turning by 58% and 55.3% when compared to the control group respectively 3 months after grafting. However the difference in reduction of turning between the two grafted groups was statistically not significant. 2) Biochemical measurements of dopamine concentration was done in pathologic and normal caudate-putamen. The concentration of dopamine was 13.5+/-3.1ng/mg of protein in normal subject and 0.6+/-0.2ng/mg of protein in the dopamine denervated caudate-putamen of the control group which was markedly reduced by 4.4% of dopamine concentration in the normal caudate-putamen. The concentration of dopamine in the cell suspension implant group was 3.2+/-1.2ng/mg of protein at three months after grafting and 3.0+/-1.1ng/mg of protein in the solid group and these values were increased in the concentration give 5 times more than those of pregrafting state. 3) In the results of immunohistochemical examination cells containing granules of dopamine were exclusively found in the grafted groups. In experimental Parkinson's disease model of Sprague-Dawley rats, it was found that the grafts of fetal mesencephalon to the caudate nucleus induced an elevation of dopamine concentration and symptomatic improvement. In the method of graft, cell suspension implant method brings faster effect, leaves less amount of damage to the host brain, and can be used in any area of the brain for the transplantation. Therefore graft of fetal mesencephalon using cell suspension grafting method might be effective treatment of patients with Parkinson's disease.