Joanna Garcia | Albert-Ludwigs-Universität Freiburg (original) (raw)
Papers by Joanna Garcia
Molecular Therapy, 2015
Recombinant adeno-associated virus (AAV) vectors are one of the most widely used gene transfer sy... more Recombinant adeno-associated virus (AAV) vectors are one of the most widely used gene transfer systems in research and clinical trials. AAV can transduce a wide range of biological tissues, however to date, there has been no investigation on targeted AAV transduction of the enteric nervous system (ENS). Here, we examined the efficiency, tropism, spread, and immunogenicity of AAV transduction in the ENS. Rats received direct injections of various AAV serotypes expressing green fluorescent protein (GFP) into the descending colon. AAV serotypes tested included; AAV 1, 2, 5, 6, 8, or 9 and the AAV2 and AAV8 capsid mutants, AAV2-Y444F, AAV2-tripleY-F, AAV2-tripleY-F+T-V, AAV8-Y733F, and AAV8-doubeY-F+T-V. Transduction, as determined by GFP-positive cells, occurred in neurons and enteric glia within the myenteric and submucosal plexuses of the ENS. AAV6 and AAV9 showed the highest levels of transduction within the ENS. Transduction efficiency scaled with titer and time, was translated to the murine ENS, and produced no vector-related immune response. A single injection of AAV into the colon covered an area of ~47 mm 2 . AAV9 primarily transduced neurons, while AAV6 transduced enteric glia and neurons. This is the first report on targeted AAV transduction of neurons and glia in the ENS.
Neurobiology of Disease, 2012
Dyskinesia seen in the off-state, referred as graft-induced dyskinesia (GID), has emerged as a se... more Dyskinesia seen in the off-state, referred as graft-induced dyskinesia (GID), has emerged as a serious complication induced by dopamine (DA) cell transplantation in parkinsonian patients. Although the mechanism underlying the appearance of GID is unknown, in a recent clinical study the partial 5-HT(1A) agonist buspirone was found to markedly reduce GID in three grafted patients, who showed significant serotonin (5-HT) hyperinnervation in the grafted striatum in positron emission tomography scanning (Politis et al., 2010, 2011). Prompted by these findings, this study was performed to investigate the involvement of serotonin neurons in the appearance of GID in the rat 6-hydroxydopamine model. L-DOPA-primed rats received transplants of DA neurons only, DA plus 5-HT neurons or 5-HT neurons only into the lesioned striatum. In DA cell-grafted rats, with or without 5-HT neurons, but not in 5-HT grafts, GID was observed consistently after administration of amphetamine (1.5mg/kg, i.p.) indicating that grafted DA neurons are required to induce GID. Strikingly, a low dose of buspirone produced a complete suppression of GID. In addition, activation of 5-HT(1A) and 5-HT(1B) receptors by 8-OH-DPAT and CP 94253, known to inhibit the activity of 5-HT neurons, significantly reduced GID, whereas induction of neurotransmitter release by fenfluramine administration significantly increased GID, indicating an involvement of the 5-HT system in the modulation of GID. To investigate the involvement of the host 5-HT system in GID, the endogenous 5-HT terminals were removed by intracerebral injection of 5,7-dihydroxytryptamine, but this treatment did not affect GID expression. However, 5-HT terminal destruction suppressed the anti-GID effect of 5-HT(1A) and 5-HT(1B) agonists, demonstrating that the 5-HT(1) agonist combination exerted its anti-GID effect through the activation of pre-synaptic host-derived receptors. By contrast, removal of the host 5-HT innervation or pre-treatment with a 5-HT(1A) antagonist did not abolish the anti-GID effect of buspirone, showing that its effect is independent from activation of either pre- or post-synaptic 5-HT(1A) receptors. Since buspirone is known to also act as a DA D(2) receptor antagonist, the selective D(2) receptor antagonist eticlopride was administered to test whether blockade of D(2) receptors could account for the anti-dyskinetic effect of buspirone. In fact, eticlopride produced complete suppression of GID in grafted animals already at very low dose. Together, these results point to a critical role of both 5-HT(1) and D(2) receptors in the modulation of GID, and suggest that 5-HT neurons exert a modulatory role in the development of this side effect of neuronal transplantation.
Fetal dopamine (DA) cell transplantation has shown to be efficient in reversing behavioral impair... more Fetal dopamine (DA) cell transplantation has shown to be efficient in reversing behavioral impairments associated with Parkinson's disease. However, the beneficial effects on motor behavior and L-DOPA-induced dyskinesia have varied greatly in between clinical trials and patients within the same trial. Recently, the inclusion of serotonin (5-HT) neurons in the grafted tissue has been suggested to play an important negative role, in particular, on the effect of L-DOPA-induced dyskinesia. In the present study we have evaluated the influence of different ratios of DA neurons in relation to 5-HT neurons in the graft on spontaneous motor behavior and L-DOPA-induced dyskinesia in a rat model of Parkinson's disease. We show that using the standard dissection method that gives rise to a DA:5-HT ratio in the graft of 2:1 to 1:2 there is significant and consistent improvement in spontaneous motor behavior and reversal of L-DOPA-induced dyskinesia. Increasing the ratio of 5-HT neurons in the graft, to a DA:5-HT ratio of in between 1:3 and 1:10, still induces significant reduction of L-DOPA-induced dyskinesia, suggesting that the detrimental effect of 5-HT neurons on L-DOPA-induced dyskinesia is prevented even by small numbers of DA neurons in the graft. Nonetheless, while the post-synaptic responses were normalized following peripheral L-DOPA delivery in animals with low DA:5-HT ratio, we observed a pharmacological indication of hyperactive pre-synaptic response in these animals. These data suggests that 5-HT cells within a graft are neither detrimental nor beneficial for functional effects of DA-rich transplants; however, in absence of sufficient numbers of DA neurons, the 5-HT neurons may induce negative effects following L-DOPA therapy. In summary, our data indicate that for future clinical trials the inclusion of 5-HT neurons in grafted tissue is not critical as long as there are sufficient numbers of DA cells in the graft.
Experimental Neurology, 2012
High frequency stimulation of the subthalamic nucleus (HFS-STN) has been successfully introduced ... more High frequency stimulation of the subthalamic nucleus (HFS-STN) has been successfully introduced to treat symptoms of advanced Parkinson's disease (PD) (rigidity, tremor and akinesia). In spite of its extensive clinical practice, little is known at cellular level about the effects of a continuous train of electrical stimuli (> 100 Hz) delivered in the STN. In this manuscript we examine the synaptic responses of substantia nigra pars compacta (SNpc) dopaminergic cells, upon continuous HFS-STN delivered in a rat brain slice preparation. We report that HFS-STN, delivered at frequencies resembling those used during DBS (100-130 Hz), caused synaptic responses in SNpc dopaminergic neurons, which summated progressively, until they reached a plateau within few tens of ms. However, if the HFS was maintained, a rapid fading of the synaptic response was observed, with an almost complete loss after 10 s. Accordingly, the postsynaptic excitability, evaluated by the tonic firing rate of the SNpc dopaminergic neurons, remained unaltered during a continuous HFS-STN. Upon HFS termination, there was a rapid recovery of synaptic function. Neither a converging synaptic input, evoked by intranigral stimulation, nor the depolarizing responses to locally-applied AMPA, were affected during HFS. The loss of synaptic response by continuous HFS-STN was not prevented by inhibition of AMPA receptor desensitization, nor by antagonists of a variety of neurotransmitter receptors, known to depress synaptic transmission in the SNpc. We conclude that a HFS in the STN, with patterns resembling in vivo DBS, induces a rapid and input-specific suppression of the synaptic transmission from STN to SNpc dopaminergic neurons, that is maintained during an ongoing stimulation. The deficit of transmission between the STN and the SNpc could have a role in the therapeutic effects of the DBS procedure.
Experimental Neurology, 2011
Parkinson's disease 6-OHDA Motor behavior Graft-induced side-effects Abnormal involuntary movemen... more Parkinson's disease 6-OHDA Motor behavior Graft-induced side-effects Abnormal involuntary movements AIM Graft-induced dyskinesia has emerged as a problematic side effect after transplantation of fetal dopamine cells into the striatum of patients with Parkinson's disease. These adverse effects of dystonic and choreatiform hyperkinesias that persisted even after withdrawal of L-DOPA medication are not yet fully understood, which poses a main obstacle for the re-initiation of neural transplantation in Parkinson's disease. The severity of pre-operative L-DOPA-induced dyskinesia has been proposed as one of several parameters influencing the development of graft-induced dyskinesia. We have therefore characterized graft-induced dyskinesia in the rat model of Parkinson's disease in animals with either mild or severe pre-operative L-DOPA-induced dyskinesia. We show that animals with intrastriatal grafts of fetal dopamine cells and severe pre-operative L-DOPA-induced dyskinesia will reduce their L-DOPA-induced dyskinesia scores by more than 75% but at the same time develop graft-induced dyskinesia of intermediate to strong severity. In contrast, animals with dopamine grafts of similar size but only mild pre-operative L-DOPA-induced dyskinesia also developed graft-induced dyskinesia but this was very mild and of intermediate severity only in a single animal. Severity of pre-operative L-DOPA-induced dyskinesia was correlated with the severity of graft-induced dyskinesia. Our data suggest that patients with no or only mild L-DOPA-induced dyskinesia may carry a lower risk for the development of graft-induced dyskinesia and therefore are better candidates to receive intracerebral grafts of fetal dopamine cells as compared to patients with more pronounced L-DOPA-induced dyskinesia.
European Journal of Neuroscience, 2014
Subthalamic nucleus (STN) modulation is currently the gold standard in the treatment of Parkinson... more Subthalamic nucleus (STN) modulation is currently the gold standard in the treatment of Parkinson's disease (PD) cases refractory to medication. Cell transplantation is a tissue-restorative approach and is a promising strategy in the treatment of PD. One of the obstacles to overcome in cell therapy is the poor dopaminergic cell survival. Our experiment investigates the impact of a partial subthalamotomy prior to ventral mesencephalic (VM) embryonic cell transplantation on dopaminergic cell survival and functional outcome. Unilateral dopamine depletion was carried out in rats, via medial forebrain bundle (MFB) injection of 6-hydroxydopamine, and half of the animals went on to receive unilateral excitotoxic lesions of the STN/Zone Incerta (ZI) causing partial lesion of these structures on the same side as the MFB lesion. All MFB-lesioned animals, with or without the STN/ZI lesion, received striatal ipsilateral embryonic VM cell grafts. The data suggest that the STN/ZI lesion could boost the dopamine cell survival in the grafts by 2.6-fold compared with the control grafted-only group. Moreover, performance on the drug-induced rotation and the spontaneous behavior tests were ameliorated on the STN/ZI-lesioned group to a significantly greater extent than the grafted-only group. These data suggest that the STN/ZI partial lesion optimized the striatal environment, promoting an improvement in cell survival. Further studies are needed to see whether the synergy between STN modulation via deep brain stimulation and cell therapy might have clinical applications in the management of PD.
Graft-induced dyskinesia (GID), covering a range of dystonic and choreiform involuntary movements... more Graft-induced dyskinesia (GID), covering a range of dystonic and choreiform involuntary movements, has been observed in some patients with Parkinson's disease (PD) after intracerebral cell transplantation. These dyskinesias have been severe in a number of patients and represent one of the main obstacles for further development of the cell therapy in PD. Serotonin neurons, included into the dopaminergic cell suspension due to the nature of the dissection process, have been suggested as a key factor for the development of GID, since the administration of the serotonin (5-HT)(1A)-receptor agonist buspirone reduced dyskinesia in transplanted PD patients. In the present study, we characterized GID in the rat PD model after transplantation of dopaminergic grafts containing different amounts of serotonin neurons. The severity of GID was significantly correlated with the amount of grafted dopamine and serotonin neurons, but the r-values were low. However, neither the innervation density of dopamine and serotonin fibers in the grafted striatum nor the dopamine-to-serotonin cell ratio correlated significantly with the severity of GID. The results extend prior knowledge of the role of dopaminergic grafts in the development of GID and show that, in the animal model, serotonin neurons within the graft suspension might be involved, but given sufficient dopamine cells, their impact on GID may be minor.
![Research paper thumbnail of [18F]desmethoxyfallypride as a novel PET radiotracer for quantitative in vivo dopamine D2/D3 receptor imaging in rat models of neurodegenerative diseases](https://attachments.academia-assets.com/45049520/thumbnails/1.jpg)
](Nuclear Medicine and Biology, 2012
Introduction: [ 18 F]desmethoxyfallypride ([ 18 F]DMFP) is a promising tracer for longitudinal as... more Introduction: [ 18 F]desmethoxyfallypride ([ 18 F]DMFP) is a promising tracer for longitudinal assessment of striatal dopamine D2/D3-receptor (D2R) availability by positron emission tomography (PET) in small animal models. We explored the feasibility of [ 18 F]DMFP-PET to image D2R availability in rat models of Huntington's (HD) and Parkinson's disease (PD). Methods: Animals received either unilateral intrastriatal quinolinic acid lesions or medial forebrain bundle injections of 6-OHDA to produce the loss of striatal projection neurones or deplete the striatal dopamine, corresponding to established animal models for HD and PD, respectively. Three weeks after lesioning, PET scans were acquired on a microPET Focus 120 system following the tail vein injection of [ 18 F]DMFP. Results: [ 18 F]DMFP-PET clearly visualized lesion induced decreases and increases of D2R availability. In vivo estimates of D2R binding and changes thereof gained by pharmacokinetic analyses correlated significantly with D2R density and its change provided by in vitro [ 3 H]raclopride-autoradiography. Conclusions: In conclusion, [ 18 F]DMFP-PET is a suitable method for in vivo D2R-assessment in preclinical research, e.g for monitoring cell-based therapies.
Cell Transplantation, 2013
Cell replacement therapy by intracerebral transplantation of fetal dopaminergic neurons has becom... more Cell replacement therapy by intracerebral transplantation of fetal dopaminergic neurons has become a promising therapeutic option for patients suffering from Parkinson's disease during the last decades. However, limited availability of human fetal tissue as well as ethical issues, lack of alternative nonfetal donor cells, and the absence of standardized transplantation protocols have prevented neurorestorative therapies from becoming a routine procedure in patients suffering from neurodegenerative diseases. Improvement of graft survival, surgery techniques, and identification of the optimal target area are imperative for further optimization of this novel treatment. In the present study, human primary fetal ventral mesencephalon-derived tissue from 7-to 9-week-old human fetuses was transplanted into 6-hydroxydopamine-lesioned adult Sprague-Dawley rats. Graft survival, fiber outgrowth, and drug-induced rotational behavior up to 14 weeks posttransplantation were compared between different intrastriatal transplantation techniques (full single cell suspension vs. partial tissue pieces suspension injected by glass capillary or metal cannula) and the intranigral glass capillary injection of a full (single cell) suspension. The results demonstrate a higher survival rate of dopamine neurons, a greater reduction in amphetamine-induced rotations (overcompensation), and more extensive fiber outgrowth for the intrastriatally transplanted partial (tissue pieces) suspension compared to all other groups. Apomorphine-induced rotational bias was significantly reduced in all groups including the intranigral group. The data confirm that human ventral mesencephalon-derived cells serve as a viable cell source, survive in a xenografting paradigm, and functionally integrate into the host tissue. In contrast to rat donor cells, keeping the original (fetal) neuronal network by preparing only a partial suspension containing tissue pieces seems to be beneficial for human cells, although a metal cannula that causes greater tissue trauma to the host is required for injection. In addition, homotopic intranigral grafts may represent a complimentary grafting approach to the "classical" ectopic intrastriatal target site in PD.
Molecular Therapy, 2015
Recombinant adeno-associated virus (AAV) vectors are one of the most widely used gene transfer sy... more Recombinant adeno-associated virus (AAV) vectors are one of the most widely used gene transfer systems in research and clinical trials. AAV can transduce a wide range of biological tissues, however to date, there has been no investigation on targeted AAV transduction of the enteric nervous system (ENS). Here, we examined the efficiency, tropism, spread, and immunogenicity of AAV transduction in the ENS. Rats received direct injections of various AAV serotypes expressing green fluorescent protein (GFP) into the descending colon. AAV serotypes tested included; AAV 1, 2, 5, 6, 8, or 9 and the AAV2 and AAV8 capsid mutants, AAV2-Y444F, AAV2-tripleY-F, AAV2-tripleY-F+T-V, AAV8-Y733F, and AAV8-doubeY-F+T-V. Transduction, as determined by GFP-positive cells, occurred in neurons and enteric glia within the myenteric and submucosal plexuses of the ENS. AAV6 and AAV9 showed the highest levels of transduction within the ENS. Transduction efficiency scaled with titer and time, was translated to the murine ENS, and produced no vector-related immune response. A single injection of AAV into the colon covered an area of ~47 mm 2 . AAV9 primarily transduced neurons, while AAV6 transduced enteric glia and neurons. This is the first report on targeted AAV transduction of neurons and glia in the ENS.
Neurobiology of Disease, 2012
Dyskinesia seen in the off-state, referred as graft-induced dyskinesia (GID), has emerged as a se... more Dyskinesia seen in the off-state, referred as graft-induced dyskinesia (GID), has emerged as a serious complication induced by dopamine (DA) cell transplantation in parkinsonian patients. Although the mechanism underlying the appearance of GID is unknown, in a recent clinical study the partial 5-HT(1A) agonist buspirone was found to markedly reduce GID in three grafted patients, who showed significant serotonin (5-HT) hyperinnervation in the grafted striatum in positron emission tomography scanning (Politis et al., 2010, 2011). Prompted by these findings, this study was performed to investigate the involvement of serotonin neurons in the appearance of GID in the rat 6-hydroxydopamine model. L-DOPA-primed rats received transplants of DA neurons only, DA plus 5-HT neurons or 5-HT neurons only into the lesioned striatum. In DA cell-grafted rats, with or without 5-HT neurons, but not in 5-HT grafts, GID was observed consistently after administration of amphetamine (1.5mg/kg, i.p.) indicating that grafted DA neurons are required to induce GID. Strikingly, a low dose of buspirone produced a complete suppression of GID. In addition, activation of 5-HT(1A) and 5-HT(1B) receptors by 8-OH-DPAT and CP 94253, known to inhibit the activity of 5-HT neurons, significantly reduced GID, whereas induction of neurotransmitter release by fenfluramine administration significantly increased GID, indicating an involvement of the 5-HT system in the modulation of GID. To investigate the involvement of the host 5-HT system in GID, the endogenous 5-HT terminals were removed by intracerebral injection of 5,7-dihydroxytryptamine, but this treatment did not affect GID expression. However, 5-HT terminal destruction suppressed the anti-GID effect of 5-HT(1A) and 5-HT(1B) agonists, demonstrating that the 5-HT(1) agonist combination exerted its anti-GID effect through the activation of pre-synaptic host-derived receptors. By contrast, removal of the host 5-HT innervation or pre-treatment with a 5-HT(1A) antagonist did not abolish the anti-GID effect of buspirone, showing that its effect is independent from activation of either pre- or post-synaptic 5-HT(1A) receptors. Since buspirone is known to also act as a DA D(2) receptor antagonist, the selective D(2) receptor antagonist eticlopride was administered to test whether blockade of D(2) receptors could account for the anti-dyskinetic effect of buspirone. In fact, eticlopride produced complete suppression of GID in grafted animals already at very low dose. Together, these results point to a critical role of both 5-HT(1) and D(2) receptors in the modulation of GID, and suggest that 5-HT neurons exert a modulatory role in the development of this side effect of neuronal transplantation.
Fetal dopamine (DA) cell transplantation has shown to be efficient in reversing behavioral impair... more Fetal dopamine (DA) cell transplantation has shown to be efficient in reversing behavioral impairments associated with Parkinson's disease. However, the beneficial effects on motor behavior and L-DOPA-induced dyskinesia have varied greatly in between clinical trials and patients within the same trial. Recently, the inclusion of serotonin (5-HT) neurons in the grafted tissue has been suggested to play an important negative role, in particular, on the effect of L-DOPA-induced dyskinesia. In the present study we have evaluated the influence of different ratios of DA neurons in relation to 5-HT neurons in the graft on spontaneous motor behavior and L-DOPA-induced dyskinesia in a rat model of Parkinson's disease. We show that using the standard dissection method that gives rise to a DA:5-HT ratio in the graft of 2:1 to 1:2 there is significant and consistent improvement in spontaneous motor behavior and reversal of L-DOPA-induced dyskinesia. Increasing the ratio of 5-HT neurons in the graft, to a DA:5-HT ratio of in between 1:3 and 1:10, still induces significant reduction of L-DOPA-induced dyskinesia, suggesting that the detrimental effect of 5-HT neurons on L-DOPA-induced dyskinesia is prevented even by small numbers of DA neurons in the graft. Nonetheless, while the post-synaptic responses were normalized following peripheral L-DOPA delivery in animals with low DA:5-HT ratio, we observed a pharmacological indication of hyperactive pre-synaptic response in these animals. These data suggests that 5-HT cells within a graft are neither detrimental nor beneficial for functional effects of DA-rich transplants; however, in absence of sufficient numbers of DA neurons, the 5-HT neurons may induce negative effects following L-DOPA therapy. In summary, our data indicate that for future clinical trials the inclusion of 5-HT neurons in grafted tissue is not critical as long as there are sufficient numbers of DA cells in the graft.
Experimental Neurology, 2012
High frequency stimulation of the subthalamic nucleus (HFS-STN) has been successfully introduced ... more High frequency stimulation of the subthalamic nucleus (HFS-STN) has been successfully introduced to treat symptoms of advanced Parkinson's disease (PD) (rigidity, tremor and akinesia). In spite of its extensive clinical practice, little is known at cellular level about the effects of a continuous train of electrical stimuli (> 100 Hz) delivered in the STN. In this manuscript we examine the synaptic responses of substantia nigra pars compacta (SNpc) dopaminergic cells, upon continuous HFS-STN delivered in a rat brain slice preparation. We report that HFS-STN, delivered at frequencies resembling those used during DBS (100-130 Hz), caused synaptic responses in SNpc dopaminergic neurons, which summated progressively, until they reached a plateau within few tens of ms. However, if the HFS was maintained, a rapid fading of the synaptic response was observed, with an almost complete loss after 10 s. Accordingly, the postsynaptic excitability, evaluated by the tonic firing rate of the SNpc dopaminergic neurons, remained unaltered during a continuous HFS-STN. Upon HFS termination, there was a rapid recovery of synaptic function. Neither a converging synaptic input, evoked by intranigral stimulation, nor the depolarizing responses to locally-applied AMPA, were affected during HFS. The loss of synaptic response by continuous HFS-STN was not prevented by inhibition of AMPA receptor desensitization, nor by antagonists of a variety of neurotransmitter receptors, known to depress synaptic transmission in the SNpc. We conclude that a HFS in the STN, with patterns resembling in vivo DBS, induces a rapid and input-specific suppression of the synaptic transmission from STN to SNpc dopaminergic neurons, that is maintained during an ongoing stimulation. The deficit of transmission between the STN and the SNpc could have a role in the therapeutic effects of the DBS procedure.
Experimental Neurology, 2011
Parkinson's disease 6-OHDA Motor behavior Graft-induced side-effects Abnormal involuntary movemen... more Parkinson's disease 6-OHDA Motor behavior Graft-induced side-effects Abnormal involuntary movements AIM Graft-induced dyskinesia has emerged as a problematic side effect after transplantation of fetal dopamine cells into the striatum of patients with Parkinson's disease. These adverse effects of dystonic and choreatiform hyperkinesias that persisted even after withdrawal of L-DOPA medication are not yet fully understood, which poses a main obstacle for the re-initiation of neural transplantation in Parkinson's disease. The severity of pre-operative L-DOPA-induced dyskinesia has been proposed as one of several parameters influencing the development of graft-induced dyskinesia. We have therefore characterized graft-induced dyskinesia in the rat model of Parkinson's disease in animals with either mild or severe pre-operative L-DOPA-induced dyskinesia. We show that animals with intrastriatal grafts of fetal dopamine cells and severe pre-operative L-DOPA-induced dyskinesia will reduce their L-DOPA-induced dyskinesia scores by more than 75% but at the same time develop graft-induced dyskinesia of intermediate to strong severity. In contrast, animals with dopamine grafts of similar size but only mild pre-operative L-DOPA-induced dyskinesia also developed graft-induced dyskinesia but this was very mild and of intermediate severity only in a single animal. Severity of pre-operative L-DOPA-induced dyskinesia was correlated with the severity of graft-induced dyskinesia. Our data suggest that patients with no or only mild L-DOPA-induced dyskinesia may carry a lower risk for the development of graft-induced dyskinesia and therefore are better candidates to receive intracerebral grafts of fetal dopamine cells as compared to patients with more pronounced L-DOPA-induced dyskinesia.
European Journal of Neuroscience, 2014
Subthalamic nucleus (STN) modulation is currently the gold standard in the treatment of Parkinson... more Subthalamic nucleus (STN) modulation is currently the gold standard in the treatment of Parkinson's disease (PD) cases refractory to medication. Cell transplantation is a tissue-restorative approach and is a promising strategy in the treatment of PD. One of the obstacles to overcome in cell therapy is the poor dopaminergic cell survival. Our experiment investigates the impact of a partial subthalamotomy prior to ventral mesencephalic (VM) embryonic cell transplantation on dopaminergic cell survival and functional outcome. Unilateral dopamine depletion was carried out in rats, via medial forebrain bundle (MFB) injection of 6-hydroxydopamine, and half of the animals went on to receive unilateral excitotoxic lesions of the STN/Zone Incerta (ZI) causing partial lesion of these structures on the same side as the MFB lesion. All MFB-lesioned animals, with or without the STN/ZI lesion, received striatal ipsilateral embryonic VM cell grafts. The data suggest that the STN/ZI lesion could boost the dopamine cell survival in the grafts by 2.6-fold compared with the control grafted-only group. Moreover, performance on the drug-induced rotation and the spontaneous behavior tests were ameliorated on the STN/ZI-lesioned group to a significantly greater extent than the grafted-only group. These data suggest that the STN/ZI partial lesion optimized the striatal environment, promoting an improvement in cell survival. Further studies are needed to see whether the synergy between STN modulation via deep brain stimulation and cell therapy might have clinical applications in the management of PD.
Graft-induced dyskinesia (GID), covering a range of dystonic and choreiform involuntary movements... more Graft-induced dyskinesia (GID), covering a range of dystonic and choreiform involuntary movements, has been observed in some patients with Parkinson's disease (PD) after intracerebral cell transplantation. These dyskinesias have been severe in a number of patients and represent one of the main obstacles for further development of the cell therapy in PD. Serotonin neurons, included into the dopaminergic cell suspension due to the nature of the dissection process, have been suggested as a key factor for the development of GID, since the administration of the serotonin (5-HT)(1A)-receptor agonist buspirone reduced dyskinesia in transplanted PD patients. In the present study, we characterized GID in the rat PD model after transplantation of dopaminergic grafts containing different amounts of serotonin neurons. The severity of GID was significantly correlated with the amount of grafted dopamine and serotonin neurons, but the r-values were low. However, neither the innervation density of dopamine and serotonin fibers in the grafted striatum nor the dopamine-to-serotonin cell ratio correlated significantly with the severity of GID. The results extend prior knowledge of the role of dopaminergic grafts in the development of GID and show that, in the animal model, serotonin neurons within the graft suspension might be involved, but given sufficient dopamine cells, their impact on GID may be minor.
Nuclear Medicine and Biology, 2012
Introduction: [ 18 F]desmethoxyfallypride ([ 18 F]DMFP) is a promising tracer for longitudinal as... more Introduction: [ 18 F]desmethoxyfallypride ([ 18 F]DMFP) is a promising tracer for longitudinal assessment of striatal dopamine D2/D3-receptor (D2R) availability by positron emission tomography (PET) in small animal models. We explored the feasibility of [ 18 F]DMFP-PET to image D2R availability in rat models of Huntington's (HD) and Parkinson's disease (PD). Methods: Animals received either unilateral intrastriatal quinolinic acid lesions or medial forebrain bundle injections of 6-OHDA to produce the loss of striatal projection neurones or deplete the striatal dopamine, corresponding to established animal models for HD and PD, respectively. Three weeks after lesioning, PET scans were acquired on a microPET Focus 120 system following the tail vein injection of [ 18 F]DMFP. Results: [ 18 F]DMFP-PET clearly visualized lesion induced decreases and increases of D2R availability. In vivo estimates of D2R binding and changes thereof gained by pharmacokinetic analyses correlated significantly with D2R density and its change provided by in vitro [ 3 H]raclopride-autoradiography. Conclusions: In conclusion, [ 18 F]DMFP-PET is a suitable method for in vivo D2R-assessment in preclinical research, e.g for monitoring cell-based therapies.
Cell Transplantation, 2013
Cell replacement therapy by intracerebral transplantation of fetal dopaminergic neurons has becom... more Cell replacement therapy by intracerebral transplantation of fetal dopaminergic neurons has become a promising therapeutic option for patients suffering from Parkinson's disease during the last decades. However, limited availability of human fetal tissue as well as ethical issues, lack of alternative nonfetal donor cells, and the absence of standardized transplantation protocols have prevented neurorestorative therapies from becoming a routine procedure in patients suffering from neurodegenerative diseases. Improvement of graft survival, surgery techniques, and identification of the optimal target area are imperative for further optimization of this novel treatment. In the present study, human primary fetal ventral mesencephalon-derived tissue from 7-to 9-week-old human fetuses was transplanted into 6-hydroxydopamine-lesioned adult Sprague-Dawley rats. Graft survival, fiber outgrowth, and drug-induced rotational behavior up to 14 weeks posttransplantation were compared between different intrastriatal transplantation techniques (full single cell suspension vs. partial tissue pieces suspension injected by glass capillary or metal cannula) and the intranigral glass capillary injection of a full (single cell) suspension. The results demonstrate a higher survival rate of dopamine neurons, a greater reduction in amphetamine-induced rotations (overcompensation), and more extensive fiber outgrowth for the intrastriatally transplanted partial (tissue pieces) suspension compared to all other groups. Apomorphine-induced rotational bias was significantly reduced in all groups including the intranigral group. The data confirm that human ventral mesencephalon-derived cells serve as a viable cell source, survive in a xenografting paradigm, and functionally integrate into the host tissue. In contrast to rat donor cells, keeping the original (fetal) neuronal network by preparing only a partial suspension containing tissue pieces seems to be beneficial for human cells, although a metal cannula that causes greater tissue trauma to the host is required for injection. In addition, homotopic intranigral grafts may represent a complimentary grafting approach to the "classical" ectopic intrastriatal target site in PD.