Ageing changes in the transplants of fetal substantia nigra grafted to striatum of adult rat

Research in motion: the enigma of Parkinson's disease pathology spread

Neuropathological changes in Parkinson's disease progress slowly and spread according to a characteristic pattern. Recent papers have shed light on this progression of pathology by examining the fate of neurons grafted into the brains of patients with Parkinson's disease. Two of these studies demonstrate that grafted healthy neurons can gradually develop the same pathology as host neurons in the diseased brains. According to these studies, implanted neurons developed alpha-synuclein- and ubiquitin-positive Lewy bodies more than a decade after transplantation. We discuss the possible underlying mechanisms and their implications for how pathology spreads in Parkinson's disease.

Unilateral fetal mesencephalic grafts in intact rats reduce amphetamine-induced dopamine release in both striata. An in vivo voltammetric study

This study investigated amphetamine-induced striatal dopamine release after intraventricular unilateral fetal mesencephalic grafts in otherwise intact rats. Dopamine was monitored in vivo by differential pulse voltammetry. In grafted animals, amphetamine-induced dopamine release was decreased compared to sham-grafted, age-matched controls. This decrease was observed in the grafted as well as in the contralateral striatum five months after intraventricular grafting. There was no measurable effect of the graft on the amphetamine-induced rotational behaviour. Our results exceed former observations reporting decreased amphetamine-induced dopamine release in the contralateral striatum of 6-hydroxydopamine-lesioned and unilaterally-grafted rats which had been attributed to a reduction of dopamine transporters. Furthermore, it was shown that concerning this effect ventral mesencephalic grafts are independent of a previous 6-hydroxydopamine lesion.

Development of fetal hippocampal grafts in intact and lesioned hippocampus

Functional recovery observed in Parkinson's disease patients following grafting of fetal substantia nigra has encouraged the development of similar grafting therapy for other neurological disorders. Fetal hippocampal grafting paradigms are of considerable significance because of their potential to treat neurological disorders affecting primarily hippocampus, including temporal lobe epilepsy, cerebral ischemia, stroke, and head injury. Since many recent studies of hippocampal transplants were carried out with an aim of laying the foundation for future clinical applications, an overview of the development of fetal hippocampal transplants, and their capability for inducing functional recovery under different host conditions is timely. In this review, we will summarize recent developments in hippocampal transplants, especially the anatomical and/or functional integration of grafts within the host brain under specific host conditions, including a comparison of intact hippocampus with various types of hippocampal lesions or injury. Improvements in grafting techniques, methods for analysis of graft integration and graft function will be summarized, in addition to critical factors which enhance the survival and integration of grafted cells and alternative sources of donor cells currently being tested or considered for hippocampal transplantation. Viewed collectively, hippocampal grafting studies show that fetal hippocampal tissue/cells survive grafting, establish both afferent and efferent connections with the host brain, and are also capable of ameliorating certain learning and memory deficits in some models. However, the efficacy of intracerebral fetal hippocampal grafts varies considerably in different animal models, depending on several factors: the mode of donor tissue preparation, the method of grafting, the state of host hippocampus at the time of grafting, and the placement of grafts within the hippocampus. Functional improvement in many models appeared to be caused partially by re-establishment of damaged circuitry and partially by a trophic action of grafts. However, exact mechanisms of graft-mediated behavioral recovery remain to be clarified due to the lack of correlative analysis in the same animal between the degree of graft integration and behavioral recovery. Issues of mechanisms of action, degree of restoration of host circuitry and amelioration of host pathological conditions will need to be sorted out clearly prior to clinical use of fetal hippocampal transplants for susceptible neurological conditions.

Cell surface molecules (NCAM and L1) in intrastriatal transplants of embryonic mesencephalon in rats

Cell surface molecules, NCAM and L1, reported to have a role in synaptogenesis, growth and fasciculation of the neurites in the brain, were traced in the embryonic nigral transplants in the host striatum of adult rats. Substantia nigra of five, 15 and 25 postnatal days were also examined for the same molecules. Tyrosine hydroxylase label was used as a marker to localize the nigral neurons and glial fibrillary acidic protein to detect if glial scar present. In the control as well as transplants large neurons had expressed tyrosine hydroxylase. By 15th postnatal day tyrosine hydroxylase neurons appeared mature and were scattered, suggesting a well-formed neuropil. NCAM and L1 reaction was seen as a peripheral rim in most of the cells on the fifth postnatal day. The reaction was mainly in relation to the large cells and more extensive on the 15th day. Thereafter on the 25th day, activity was negligible. Large neurons demonstrated strong reactivity for NCAM and L1 during early post-transplantation days. After 30 days only smaller cells were reactive, many of which could be identified as neurons. Strong reaction for these molecules was present only until 60 days, though faint reaction could be detected even on the 90th day. These observations indicate that the growth promoting molecules, the type seen in the neonatal period, can be detected normally only until the neurons mature. Prolonged expression of these molecules by the grafted neurons indicate delay in the maturation of these cells due to absence of adequate target sites for synaptic connections. Some of the smaller cells expressing these molecules after 30 days of transplantation could be astroglia, either proliferating or reactive.

Delay in manifestations of aging by grafting NGF cultured chromaffin cells in adulthood

Dopamine agonists or grafts compensate impaired motor functions in aged rats. However, there is no evidence showing whether grafting in adulthood retard aging manifestations. Motor performance of 13-month-old rats was tested on 2 meter-long wooden beams which had a 15 degree inclination and whose thickness varied from 3, 6, 12, 18, to 24 mm. Rats at 14 months were randomly assigned to 3 groups: sham graft (Group 1); intrastriatal graft of chromaffin cells cultured with NGF (Group 2); intrastriatal graft of chromaffin cells (Group 3). Motor performance was tested at monthly intervals up until rats were 26 months old. Two more groups were included: 26-month-old naive rats (Group 4); and 3- to 5-month-old naive rats (Group 5) both evaluated only once. At 26 months, the basal activity of ventral mesencephalic dopaminergic neurons was recorded. Results showed in Group 2 delay of motor detriments seen in aged rats, maintenance of basal firing rates of nigral cells compared to those of younger rats, and greater survival of substantia nigra cells. It is suggested that NGF cultured chromaffin cells produce a delay of motor detriments in aged rats, as a result of inducing survival and firing rates of nigral cells comparable to those seen in young rats.