FK506 and cyclosporin A enhance the survival of cultured and grafted rat embryonic dopamine neurons

An alginate-based encapsulation system for delivery of therapeutic cells to the CNS

Treatment options for neurodegenerative conditions such as Parkinson's disease have included the delivery of cells which release dopamine or neurotrophic factors to the brain. Here, we report the development of a novel approach for protecting cells after implantation into the central nervous system (CNS), by developing dual-layer alginate beads that encapsulate therapeutic cells and release an immunomodulatory compound in a sustained manner. An optimal alginate formulation was selected with a view to providing a sustained physical barrier between engrafted cells and host tissue, enabling exchange of small molecules while blocking components of the host immune response. In addition, a potent immunosuppressant, FK506, was incorporated into the outer layer of alginate beads using electrosprayed poly-ε-caprolactone core–shell nanoparticles with prolonged release profiles. The stiffness, porosity, stability and ability of the alginate beads to support and protect encapsulated SH-SY5Y cells was demonstrated, and the release profile of FK506 and its effect on T-cell proliferation in vitro was characterized. Collectively, our results indicate this multi-layer encapsulation technology has the potential to be suitable for use in CNS cell delivery, to protect implanted cells from host immune responses whilst providing permeability to nutrients and released therapeutic molecules.

Novel composite cell encapsulation system: dual-layer, micro-scale beads maintain cell survival while releasing immunomodulatory FK506 in a sustained manner. This biotechnology platform could be applicable for treatment of CNS and other disorders.

Intracerebral Xenotransplantation of GFP Mouse Bone Marrow Stromal Cells in Intact and Stroke Rat Brain: Graft Survival and Immunologic Response

The present study characterized survival and immunologic response of bone marrow stromal cells (BMSCs) following transplantation into intact and stroke brains. In the first study, intrastriatal transplantation of BMSC (60,000 in 3 μl) or vehicle was performed in normal adult Sprague-Dawley male rats that subsequently received daily cyclosporin A (CsA, 10 mg/kg, IP in 3 ml) or vehicle (olive oil, similar volume) starting on day of surgery up to 3 days posttransplantation. Animals were euthanized at 3 or 30 days posttransplantation and brains were processed either for green fluorescent protein (GFP) microscopy or flow cytometry (FACS). Both GFP epifluorescence and FACS scanning revealed GFP+ BMSCs in both groups of transplanted rats with or without CsA, although significantly increased (1.6- to 3-fold more) survival of GFP+ BMSCs was observed in the immunosuppressed animals. Further histologic examination revealed widespread dispersal of BMSCs away from the graft core accompanied by many long outgrowth processes in non-CsA-transplanted animals, whereas a very dense graft core, with cells expressing only sporadic short outgrowth processes, was observed in CsA-transplanted animals. There were no detectable GFP+ BMSCs in nontrans-planted rats that received CsA or vehicle. Immunologic response via FACS analysis revealed a decreased presence of cytotoxic cells, characterized by near complete absence of CD8+ cells, and lack of activation depicted by low CD69 expression in CsA-treated transplanted animals. In contrast, elevated levels of CD8+ cells and increased activation of CD69 expression were observed in transplanted animals that received vehicle alone. CD4+ helper cells were almost nondetectable in transplanted rats that received CsA, but also only minimally elevated in transplanted rats that received vehicle. Nontransplanted rats that received either CsA or vehicle displayed very minimal detectable levels of all three lymphocyte markers. In the second study, a new set of male Sprague-Dawley rats initially received bilateral stereotaxic intrastriatal transplantation of BMSCs and 3 days after were subjected to unilateral transient occlusion of middle cerebral artery. The animals were allowed to survive for 3 days after stroke without CsA immunosuppression. Epifluorescence microscopy revealed significantly higher (5-fold more) survival of transplanted GFP+ BMSCs in the stroke striatum compared with the intact striatum. The majority of the grafts remained within the original dorsal striatal transplant site, characterized by no obvious migration in intact striatum, but with long-distance migration along the ischemic penumbra in the stroke striatum. Moreover, FACS scanning analyses revealed low levels of immunologic response of grafted BMSCs in both stroke and intact striata. These results, taken together, suggest that xenotransplantation of mouse BMSCs into adult rats is feasible. Immunosuppression therapy can enhance xenograft survival and reduce graft-induced immunologic response; however, in the acute phase posttransplantation, BMSCs can survive in intact and stroke brain, and may even exhibit long-distance migration and increased outgrowth processes without immunosuppression.

Liposomal Formulations of Tacrolimus and Rapamycin Increase Graft Survival and Fiber Outgrowth of Dopaminergic Grafts

The immunosuppressive drugs tacrolimus (TAC) and rapamycin (RAPA) have both been found to have neuroprotective effects on dopaminergic neurons. The purpose of the present study was to investigate whether liposomal formulations of these drugs administered directly into the brain improve cell survival and fiber outgrowth. Rats with unilateral 6-hydroxydopamine lesions were transplanted with 800,000 fetal rat ventral mesencephalic cells and randomly divided to one of four groups. Group 1 received a transplant containing cells only; group 2 received a cell suspension containing 0.68 μM liposomal RAPA (LRAPA); group 3 received a cell suspension containing 2.0 μM liposomal TAC (LTAC); and group 4 received a cell suspension containing a liposomal formulation of both 0.68 μM RAPA and 2.0 μM TAC (LRAPATAC). Rats were sacrificed after 6 weeks, and cell survival and fiber outgrowth were assessed using tyrosine hydroxylase (TH) immunohistochemistry. The animals receiving a cell suspension containing either LTAC or LRAPATAC were found to have significantly more surviving TH-immunoreactive (TH-ir) cells than the control group receiving cells only. The group receiving LTAC had significantly longer fibers, the group receiving LRAPA had significantly more fibers close to the graft, and the group receiving LRAPATAC had significantly more fibers at all distances. This study shows the feasibility of using liposomal formulations of neuroimmunophilins directly in the brain at the time of implantation to improve graft survival and fiber outgrowth. Furthermore, we have shown that the combination of LTAC and LRAPA has a synergistic effect. These compounds may play an important role in optimizing graft survival and host reinnervation in cellmediated brain repair strategies for the treatment of neurological conditions.

Cyclosporin promotes neurorestoration and cell replacement therapy in pre-clinical models of Parkinson's disease

BACKGROUND

The early clinical trials using fetal ventral mesencephalic (VM) allografts in Parkinson's disease (PD) patients have shown efficacy (albeit not in all cases) and have paved the way for further development of cell replacement therapy strategies in PD. The preclinical work that led to these clinical trials used allografts of fetal VM tissue placed into 6-OHDA lesioned rats, while the patients received similar allografts under cover of immunosuppression in an α-synuclein disease state. Thus developing models that more faithfully replicate the clinical scenario would be a useful tool for the translation of such cell-based therapies to the clinic.

RESULTS

Here, we show that while providing functional recovery, transplantation of fetal dopamine neurons into the AAV-α-synuclein rat model of PD resulted in smaller-sized grafts as compared to similar grafts placed into the 6-OHDA-lesioned striatum. Additionally, we found that cyclosporin treatment was able to promote the survival of the transplanted cells in this allografted state and surprisingly also provided therapeutic benefit in sham-operated animals. We demonstrated that delayed cyclosporin treatment afforded neurorestoration in three complementary models of PD including the Thy1-α-synuclein transgenic mouse, a novel AAV-α-synuclein mouse model, and the MPTP mouse model. We then explored the mechanisms for this benefit of cyclosporin and found it was mediated by both cell-autonomous mechanisms and non-cell autonomous mechanisms.

CONCLUSION

This study provides compelling evidence in favor for the use of immunosuppression in all grafted PD patients receiving cell replacement therapy, regardless of the immunological mismatch between donor and host cells, and also suggests that cyclosporine treatment itself may act as a disease-modifying therapy in all PD patients.

Dietary supplementation with blueberry extract improves survival of transplanted dopamine neurons

The exact mechanisms contributing to poor neuronal survival in cell transplantation paradigms for Parkinson's disease (PD) are unknown. However, transplantation-induced host immune response, inflammation, and subsequent oxidative stress are likely contributors to cell death since dopamine (DA) neurons are exquisitely sensitive to oxidative damage. Multiple studies have attempted to improve cell survival by treating transplant material with antioxidant and antiinflammatory compounds, whereas far fewer studies have attempted to modify the host environment to reduce these threats. Flavonoids, phytochemicals found in fruits and vegetables, have antioxidant, antiinflammatory, and immunomodulatory properties. For example, supplementation with dietary blueberry extract (BBE) prevents oxidative stress-associated impairment of striatal motor function during aging and restores lost motor function in aged rats. We hypothesized that dietary supplementation of rodent diets with BBE would improve the survival of embryonic DA neurons transplanted into the unilaterally DA-depleted striatum. Inclusion of 2% BBE in a custom chow diet significantly increased the survival of implanted DA neurons and ameliorated rotational behavior asymmetries as compared to transplanted animals consuming a standard diet. These findings provide support for the potential of dietary phytochemicals as an easily administered and well-tolerated therapy that can be used to improve the effectiveness of DA neuron replacement.

FK506 ameliorates cell death features in Huntington's disease striatal cell models

Huntington's disease (HD) is a genetic neurodegenerative disorder characterized by striatal neurodegeneration, involving apoptosis. FK506, an inhibitor of calcineurin (or protein phosphatase 3, formerly known as protein phosphatase 2B), has shown neuroprotective effects in several cellular and animal models of HD. In the present study, we show the protective effects of FK506 in two striatal HD models, primary rat striatal neurons treated with 3-nitropropionic acid (3-NP) and immortalized striatal STHdh cells derived from HD knock-in mice expressing normal (STHdh(7/7)) or full-length mutant huntingtin (FL-mHtt) with 111 glutamines (STHdh(111/111)), under basal conditions and after exposure to 3-NP or staurosporine (STS). In rat striatal neurons, FK506 abolished 3-NP-induced increase in caspase-3 activation, DNA fragmentation/condensation and necrosis. Nevertheless, in STHdh(111/111) cells under basal conditions, FK506 did not prevent, in a significant manner, the release of cytochrome c and apoptosis inducing factor (AIF) from mitochondria, or alter Bax/Bcl-2 ratio, but significantly reverted caspase-3 activation. In STHdh(111/111) cells treated with 0.3mM 3-NP or 25 nM STS, linked to high necrosis, exposure to FK506 exerted no significant effects on caspase-3 activation. However, treatment of STHdh(111/111) cells exposed to 10nM STS with FK506 effectively prevented cell death by apoptosis and moderate necrosis. The results suggest that FK506 may be neuroprotective against apoptosis and necrosis under mild cell death stimulus in the presence of FLmHtt.

Effects of low intensity pulsed ultrasound on rat Schwann cells metabolism

The effects of low intensity pulsed ultrasound to tenocytes and osteocytes are well understood and applied clinically. However, its effects on cultured Schwann cells are still not well elucidated. This study was designed to elucidate the effects of low intensity pulsed ultrasound on cultured Schwann cells and their possible molecular mechanism. Schwann cells were harvested from sciatic nerves of 3-day-old Sprague-Dawley rats. Low intensity pulsed ultrasound stimulator (frequency: 1 MHz, duration: 2 min, duty cycle: 20%, total treatment time: 3 min) was applied to three different culture conditions: regular culture medium containing 0, 5, or 10% fetal bovine serum. The viability, damage, and differentiation of Schwann cells were examined; gene expression was also analyzed. In the presence of 0.3 W/cm(2) pulsed ultrasound stimulation, increases in cell viability and decreases in cell apoptosis were observed in the serum deprivation group; in this culture condition, interleukin-1, tumor necrosis factor-alpha, and protein zero genes expression were downregulated and Desert Hedgehog transcripts gene expression was upregulated. We concluded that intervention with low intensity pulsed ultrasound could promote Schwann cell proliferation, prevent cell death, and keep adequate phenotype presentation for peripheral nerve recovery. The low intensity pulsed ultrasound stimulation to an injured nerve site could be applied as early as possible especially when the microenvironment is almost serum-free to obtain the most benefit.

Expansion of mouse sertoli cells on microcarriers

BACKGROUND

Sertoli cells (SCs) have been described as the 'nurse cells' of the testis whose primary function is to provide essential growth factors and create an appropriate environment for development of other cells [for example, germinal and nerve stem cells (NSCs), used here]. However, the greatest challenge at present is that it is difficult to obtain sufficient SCs of normal physiological function for cell transplantation and biological medicine, largely due to traditional static culture parameter difficult to be monitored and scaled up.

OBJECTIVE

Operational stirred culture conditions for in vitro expansion and differentiation of SCs need to be optimized for large-scale culture.

MATERIALS AND METHODS

In this study, the culturing process for primary SC expansion and maintaining lack of differentiation was optimized for the first time, by using microcarrier bead technology in spinner flask culture. Effects of various feeding/refreshing regimes, stirring speeds, seed inoculum levels of SCs, and concentrations of microcarrier used for expansion of mouse SCs were also explored. In addition, pH, osmotic pressure and metabolic variables including consumption rates of glucose, glutamine, amino acids, and formation rates of lactic acid and ammonia, were investigated in culture.

RESULTS

After 6 days, maximal cell densities achieved were 4.6 x 10(6) cells/ml for Cytodex-1 in DMEM/FBS compared to 4.8 x 10(5) cells/ml in static culture. Improved expansion was achieved using an inoculum of 1 x 10(5) cells/ml and microcarrier concentration of 3 mg/ml at stirring speed of 30 rpm. RESULTS indicated that medium replacement (50% changed everyday) resulted in supply of nutrients and removal of waste products inhibiting cell growth, that lead to maintenance of cultures in steady state for several days. These conditions favoured preservation of SCs in the undifferentiated state and significantly increased their physiological activity and trophic function, which were assessed by co-culturing with NSCs and immunostaining.

CONCLUSION

Data obtained in this study demonstrate the vast potential of this stirred culture system for efficient, reproducible and cost-effective expansion of SCs in vitro. The system has advantages over static culture, which has major obstacles such as lower cell density, is time-consuming and susceptible to contamination.

3-nitropropionic acid-induced mitochondrial permeability transition: comparative study of mitochondria from different tissues and brain regions

The adult rat striatum is particularly vulnerable to systemic administration of the succinate dehydrogenase inhibitor 3-nitropropionic acid (3NP), which is known to induce degeneration of the caudate-putamen, as occurs in Huntington's disease. The aim of the present study was to compare the susceptibility of isolated mitochondria from different rat brain regions (striatum, cortex, and cerebellum) as well as from the liver, kidney, and heart to mitochondrial permeability transition (MPT) induced by 3NP and Ca(2+). In the presence of micromolar Ca(2+) concentrations, 3NP induces MPT in a dose-dependent manner, as estimated by mitochondrial swelling and a decrease in the transmembrane electrical potential. A 3NP concentration capable of promoting a 10% inhibition of ADP-stimulated, succinate-supported respiration was sufficient to stimulate Ca(2+)-induced MPT. Brain and heart mitochondria were generally more sensitive to 3NP and Ca(2+)-induced MPT than mitochondria from liver and kidney. In addition, a partial inhibition of mitochondrial respiration by 3NP resulted in more pronounced MPT in striatal mitochondria than in cortical or cerebellar organelles. A similar inhibition of succinate dehydrogenase activity was observed in rat tissue homogenates obtained from various brain regions as well as from liver, kidney, and heart 24 hr after a single i.p. 3NP dose. Mitochondria isolated from forebrains of 3NP-treated rats were also more susceptible to Ca(2+)-induced MPT than those of control rats. We propose that the increased susceptibility of the striatum to 3NP-induced neurodegeneration may be partially explained by its susceptibility to MPT, together with the greater vulnerability of this brain region to glutamate receptor-mediated Ca(2+) influx.

Cyclosporine A reduces dendritic outgrowth of neuroblasts in the subgranular zone of the dentate gyrus in C57BL/6 mice

In the present study, we observed the effects of cyclosporine A (CsA), an efficient immunosuppressant, on cell proliferation and neuroblast differentiation in the subgranular zone of the dentate gyrus (SZDG) in normal C57BL/6 mice using Ki67 and doublecortin (DCX) immunohistochemical staining, respectively. At 8 weeks of age, vehicle (physiological saline) or CsA was daily administered (40 mg/kg, i.p.) for 1 week. Animals were sacrificed at 2 weeks after last administration. CsA treatment did not show any influences in neurons, astrocytes and microglia based on immunohistochemistry for its markers, respectively. However, in the CsA-treated group, Fluoro-Jade B, a marker for neurodegeneration, positive cells were found in the SZDG, not in the vehicle-treated group. In the vehicle-treated group, Ki67 immunoreactive (+) nuclei were clustered in the SZDG, whereas in the CsA-treated group Ki67(+) nuclei were scattered in the SZDG, showing no difference in cell numbers. Numbers of DCX(+) neuroblasts with well-developed processes (tertiary dendrites) were much lower in the CsA-treated group than those in the vehicle-treated group; however, numbers of DCX(+) neuroblasts with secondary dendrites were similar in both the groups. These results suggest that CsA significantly reduces dendritic outgrowth and complexity from neuroblasts in the SZDG without any affecting in neurons, astrocytes and microglia in normal mice.

Intracerebral co-transplantation of liposomal tacrolimus improves xenograft survival and reduces graft rejection in the hemiparkinsonian rat

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 tacrolimus (TAC) and rapamycin (RAPA), have been investigated for their neuroprotective properties on dopaminergic neurons. These drugs have been formulated into liposomal preparations [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 hemiparkinsonian 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 transplants of the following: 1) a cell suspension containing 400,000 fetal mouse ventral mesencephalic cells; 2) the cell suspension containing 0.63 microM LRAPA; 3) the cell suspension containing a dose of 2.0 microM LTAC; 4) the cell suspension containing 2.0 microM LTAC and 0.63 microM 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 immunorejection 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 immunosuppression in experimental neural transplantation in the laboratory and its translation into the clinical setting.

Neuroprotectants FK-506 and cyclosporin A ameliorate the course of pilocarpine-induced seizures

The present study was designed to examine whether neuroprotective agents, FK506 or cyclosporin A (CsA), applied to rats undergoing pilocarpine-induced seizures can minimize further development of the status epilepticus. In order to solve this problem, pilocarpine was injected in 60-day-old Wistar rats to evoke status epilepticus. When epileptic seizures reached a defined, moderate level of intensity, the rats received a single FK506 or CsA injections. During a 6-h period following pilocarpine injection, the animals were observed continuously and motor symptoms were recorded and rated. In epileptic rats injected with FK-506 or CsA, signs of significant amelioration of the course of epilepsy accompanied by longer survival periods were observed. Moreover, some differences between effects of the two agents were seen. The obtained results appear to show that, in addition to neuroprotective action, FK506 and CsA can exert also antiepileptic influences.

Sustained survival of xenografted human neural stem/progenitor cells in experimental brain trauma despite discontinuation of immunosuppression

Neural stem cells have emerged as a promising therapeutic tool in CNS disease and injuries. In the clinical setting, cultured human neural stem/progenitor cells (hNSC) are an attractive possibility for transplantation to the damaged brain. However, transplantation of hNSC requires toxic immunosuppressive treatment to avoid rejection. The aim of the current study was to evaluate if shortening the duration of immunosuppression by cyclosporin A would affect hNSC survival and differentiation after transplantation to the site of a focal brain injury in the rat. hNSC were xenografted to the hippocampus and the medial limit of an experimentally induced cortical contusion. The animals received immunosuppression for either 6 or 3 weeks or no immunosuppression. The status of the grafted human cells was analysed by immunohistochemistry. No statistically significant differences were observed between the two immunosuppressed groups regarding graft survival, migration or proliferation at 6 weeks post-transplantation. In contrast, the graft survival was extremely poor in the non-immunosuppressed group. Furthermore, the expression of the differentiation markers nestin, neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) in the transplanted cells did not differ significantly between the two immunosuppressed groups. Moreover, a fourth group of eight animals that were immunosuppressed for 3 weeks were allowed to survive for 6 months. Five of these rats demonstrated robust graft survival in the hippocampus and scattered cells in the cortex. This study demonstrates the importance of immunosuppression but also the possibility of shortening immunosuppression without impacting on the phenotype of the grafted hNSC.

The effect of high outflow permeability in asymmetric poly(dl-lactic acid-co-glycolic acid) conduits for peripheral nerve regeneration

This study attempted to accelerate the peripheral nerve regeneration, using the high outflow rate of asymmetric poly(dl-lactic acid-co-glycolic acid) (PLGA) nerve conduits. Asymmetric PLGA nerve conduits of monomer ratio 85/15 were prepared by immersion-precipitation method to serve as possible materials. In this study, mandrels were immersed into a 20% (wt/wt) of PLGA/1,4-dioxane solution and precipitated in a non-solvent bath followed by freeze-drying. Different concentrations of isopropyl alcohol (95%, 40% and 20%) were used as precipitation baths where non-asymmetric (95%) and asymmetric (40% and 20%) conduits could easily form. The asymmetric nerve conduits that consisted of macrovoids on the outer layer, and interconnected micropores in the inner sublayer, possessed characters of larger outflow rate than inflow rate. The asymmetric conduits were implanted to 10mm right sciatic nerve defects in rats. Autografts, silicone and non-asymmetric PLGA conduits were performed as the control and the contrast groups. Implanted graft specimens of all groups were harvested for histological analysis at 4 and 6 weeks following surgery. The asymmetric PLGA conduits maintained a stable supporting structure and inhibited exogenous cells invasion during entire regeneration process. Asymmetric PLGA conduits were found to have statistically greater number of regenerated axons at the midconduit and distal nerve site of implanted grafts, as compared to the silicone and non-asymmetric groups at 4 and 6 weeks. Of interest was that the results of 4 weeks in asymmetric groups were better than the non-asymmetric groups at 6 weeks in number of axons. According to the results of permeability, the asymmetric structure in the conduit wall seemed to enhance the removal of the blockage of the waste drain from the inner inflamed wound in the early stage, which may have improved the efficacy of the peripheral nerve regeneration. The asymmetric structure could be adequately employed in the future as optimal nerve conduits in peripheral nerve regeneration.

Low-intensity-ultrasound-accelerated nerve regeneration using cell-seeded poly(D,L-lactic acid-co-glycolic acid) conduits: an in vivo and in vitro study

This study investigated the effects of low intensity ultrasound on seeded Schwann cells within poly(DL-lactic acid-co-glycolic acid) (PLGA) conduits by in vitro and in vivo trials for peripheral nerve regeneration. The possible differences in the ultrasonic effects when using biodegradable and non-biodegradable materials as the conduits were also studied, using silicone rubber tubes as comparisons. In the in vitro study, seeded Schwann cells were cultured in serum deprivation culture medium that simulated the environment of mechanical trauma on injury nerve site. After 12, 24, and 48 h, only the PLGA conduit groups exposed to 0.05 W/cm(2), 3 min/treatment of ultrasound exhibited decreased LDH release and increased MTT values compared to the sham groups. Based on the results of the in vitro experiment in LDH and MTT testing, the silicone conduits with seeded Schwann cells group was ignored in the in vivo study. The PLGA nerve conduits seeded with Schwann cells (9 x 10(3) cells) were implanted to 15-mm right sciatic nerve defects in rats. Each conduit received 12 ultrasonic treatment sessions over 2 weeks after 1 day of rest. Ultrasound was applied as follows: frequency, 1MHz; intensity, 0.3 W/cm(2) (SATP); treatment, 5 min/day. Implanted graft specimens were harvested for histological analysis at 8 weeks following surgery. PLGA groups (with and without Schwann cells) treated with pulsed ultrasonic stimulation were found to have significantly greater number and area of regenerated axons at the mid-conduit of implanted grafts, as compared to the sham groups. Ultrasonic stimulation on silicone groups was found to induce a mass of fibrous tissues that covered the nerve conduits and retarded axon regeneration.

Behavioral changes in unilaterally 6-hydroxy-dopamine lesioned rats after transplantation of differentiated mouse embryonic stem cells without morphological integration

OBJECTIVE

Transplantation of fetal mesencephalic cells into the striatum has been performed in about 350 patients with Parkinson's disease and has been intensively studied in rat models of Parkinson's disease. Limited access to this material has shifted the focus toward embryonic stem (ES) cells. The grafting of undifferentiated ES cells to 6-hydroxy-dopamine (6-OHDA)-lesioned rats leads to behavioral improvements but may induce teratoma-like structures. This risk might be avoided by using more differentiated ES cells. In this study, we aimed to investigate differentiated mouse ES cells regarding their in vivo development and fate after transplantation in the striatum in the 6-OHDA rat model and the behavioral changes induced after transplantation.

METHODS

Mouse ES cells were differentiated on PA6 feeder cells for 14 days before grafting. Twenty to twenty-five percent of the neurons obtained were positive for tyrosine-hydroxylase (TH). PKH26-labeled cells were transplanted in the striata of unilaterally 6-OHDA-lesioned rats.

RESULTS

Direct PKH26 fluorescence visualization and TH staining proved the existence of cell deposits in the striata of all grafted animals, indicating cell survival for at least 5 weeks posttransplantation. There was no evidence of tumor formation. Immunocytochemical staining showed glial immunoreactivity surrounding the grafted cell deposits, probably inhibiting axonal outgrowth into the surrounding host tissue. There was a significant reduction in amphetamine-induced rotational behavior seen in grafted animals, which was not observed in sham-operated animals.

CONCLUSIONS

The findings of this study suggest that the amphetamine-induced rotational behavioral test without histological confirmation is not proof of morphological integration with axonal outgrowth within the first 4 weeks posttransplantation.

Increased fiber outgrowth from xeno-transplanted human embryonic dopaminergic neurons with co-implants of polymer-encapsulated genetically modified cells releasing glial cell line-derived neurotrophic factor

We investigated whether a continuous supply of glial cell line-derived neurotrophic factor (GDNF) via encapsulated genetically modified cells can promote survival and fiber outgrowth from xenotransplanted human dopaminergic neurons. Cells genetically engineered to continuously secrete GDNF were confined in hollow fiber-based macrocapsules. Each hemiparkinsonian rat received either a single C2C12-hGDNF capsule (n=8) or a C2C12-control capsule (n=8) concomitantly with human embryonic ventral mesencephalic cell suspension transplants. Our results show that fiber outgrowth in the area between the capsule and the graft is more extensive in rats with GDNF-releasing capsules than in rats with control capsules. We suggest that continuous and safe delivery of GDNF to the brain could be a potential way to optimize neural transplantation as a therapy for Parkinson's disease.

The immunophilin ligand FK506, but not the P38 kinase inhibitor SB203580, improves function of adult rat muscle reinnervated from transplants of embryonic neurons

Injury to the adult CNS often involves death of motoneurons, resulting in the paralysis and progressive atrophy of muscle. There is no effective therapy to replace motoneurons in the CNS. Our strategy to replace neurons and to rescue denervated muscles is to transplant dissociated embryonic day 14-15 (E14-15) ventral spinal cord cells into the distal stump of a peripheral nerve near the denervated muscles. Here, we test whether long-term delivery of two pharmacological inhibitors to denervated muscle, FK506 or SB203580, enhances reinnervation of muscle from embryonic cells transplanted in the tibial nerve of adult Fischer rats. FK506, SB203580 (2.5 mg/kg) or saline was delivered under the fascia of the medial gastrocnemius muscle for 4 weeks, beginning when muscles were denervated by section of the sciatic nerve. After 1 week of nerve degeneration, one million E14-15 ventral spinal cord cells were transplanted into the distal tibial nerve stump of each rat in the three treatment groups. Ten weeks later, all cell transplants had neuron-specific nuclear protein (NeuN) positive neurons. Neuron survival and axon regeneration were similar across treatments. An average (+/-S.E.) of 210+/-66, 100+/-36 and 176+/-58 myelinated axons grew distally from the cell transplants of rats with muscles treated with FK506, SB203580 or saline, respectively. Regenerating axons in muscles of all three treatments groups were detected with antibodies against phosphorylated neurofilaments and synaptophysin, and motor end plates were labeled with alpha-bungarotoxin. Muscles of rats that received transplants of media only had no axon growth, indicating that the muscles were denervated. The mean muscle fiber areas of rats that received cell transplants and had long-term delivery of FK506, SB203580 or saline to muscles were significantly larger than those of denervated muscle fibers. Thus, cell transplantation reduced muscle atrophy. Transplantation of embryonic cells also resulted in functional muscle reinnervation. Electromyographic activity and force were evoked from >90% of the muscles of rats with cell transplants, but not from denervated muscles. FK506-treated muscles were significantly more fatigue resistant than naive control muscles. FK506-treated muscles also had significantly stronger motor units than those in SB203580 or saline-treated muscles. These data suggest that a pathway regulated by FK506 improves the function of muscles reinnervated by embryonic neurons placed in peripheral nerve.

Immunophilin expression in the HIV-infected brain

Immunophilins (IP) are receptors for immunosuppressive drugs and also aid protein folding, assembly, and trafficking. This autopsy study analyses the levels of FKBP12 in the brain of patients with HIV encephalitis. We show that the expression of FKBP12 is increased in the deep gray matter and frontal cortex where it colocalizes with markers of pathology. Changes in FKBP12 levels may be linked to the abnormal protein folding and axonal transport that characterize the neurodegenerative process and could also explain the selective vulnerability of the basal ganglia to HIV infection.

Calcineurin-mediated Bad translocation regulates cyanide-induced neuronal apoptosis

In cyanide-induced apoptosis, an increase in cytosolic free Ca2+ and generation of reactive oxygen species are initiation stimuli for apoptotic cell death. Previous studies have shown that cyanide-stimulated translocation of Bax (Bcl-associated X protein) to mitochondria is linked with release of cytochrome c and subsequent activation of a caspase cascade [Shou, Li, Prabhakaran, Borowitz and Isom (2003) Toxicol. Sci. 75, 99-107]. In the present study, the relationship of the cyanide-induced increase in cytosolic free Ca2+ to activation of Bad ( Bcl-2/Bcl-X(L)- antagonist, causing cell death) was determined in cortical cells. Bad is a Ca2+-sensitive pro-apoptotic Bcl-2 protein, which on activation translocates from cytosol to mitochondria to initiate cytochrome c release. In cultured primary cortical cells, cyanide produced a concentration- and time-dependent translocation of Bad from cytosol to mitochondria. Translocation occurred early in the apoptotic response, since mitochondrial Bad was detected within 1 h of cyanide treatment. Mitochondrial levels of the protein continued to increase up to 12 h post-cyanide exposure. Concurrent with Bad translocation, a Ca2+-sensitive increase in cellular calcineurin activity was observed. Increased cytosolic Ca2+ and calcineurin activation stimulated Bad translocation since BAPTA [bis-(o-aminophenoxy)ethane-N, N, N', N'-tetra-acetic acid], an intracellular Ca2+ chelator, and cyclosporin A, a calcineurin inhibitor, significantly reduced translocation. BAPTA also blocked release of cytochrome c from mitochondria as well as apoptosis. Furthermore, treatment of cells with the calcineurin inhibitors cyclosporin A or FK506 blocked the apoptotic response, linking calcineurin activation and the subsequent translocation of Bad to cell death. These observations show that by inducing a rapid increase in cytosolic free Ca2+, cyanide can partially initiate the apoptotic cascade through a calcineurin-mediated translocation of Bad to mitochondria.

Different effects of neuroprotectants FK-506 and cyclosporin A on susceptibility to pilocarpine-induced seizures in rats with brain injured at different developmental stages

Susceptibility of the injured brain to epileptic seizures depends on the developmental stage at which the injury had been inflicted (our previous paper published in Epilepsy Res. 53 (2003) 216-224). The present study was designed to examine whether neuroprotective agents applied following the injury can decrease the seizure susceptibility. In order to solve this problem, the left cerebral hemisphere was mechanically injured in 6- and 30-day-old Wistar rats. Neuroprotectants FK506 or Cyclosporin A (CsA) were injected 20 min and 24h following the injury. On postnatal day 60, all the animals received single i.p. pilocarpine injections to evoke epileptic seizures. During a 6h period following the injection, the animals were observed continuously and pilocarpine-induced symptoms were recorded and rated. The animals were sacrificed 7 days after pilocarpine injection. In rats injured on postnatal days 6 or 30 (P6 or P30, respectively) and injected with FK-506 after the injury, signs of amelioration in the course of epilepsy were observed. Generally, proportions of rats suffering from heavy seizures were lower and/or their survival periods were longer. Following treatment with CsA, proportions of rats displaying heavy seizures were greater. It was accompanied by extremely high mortality (in rats injured on P6) or a longer duration of seizures (in rats injured on P30). The results appear to point to age-dependent differences between the mechanisms of action of the two neuroprotectants.

Ultrastructural characterization of dissociated embryonic ventral mesencephalic tissue treated with neuroprotectants

Poor survival and differentiation of grafted dopamine neurons limits the application of clinical transplantation in Parkinson's disease. The survival of grafted dopamine neurons is only improved by a factor of 2-3 by adding neuroprotectants during tissue preparation. We used dye exclusion cell viability and electron microscopy to investigate the effects of the caspase inhibitor ac-YVAD-cmk and the lazaroid tirilazad mesylate on ultrastructural changes in dissociated embryonic mesencephalic cells. In addition, we examined whether the neuroprotectants selectively counteracted specific signs of neurodegeneration. Cell viability decreased significantly over time in both control and treated cell suspensions, but the number of viable cells remaining was significantly higher in tirilazad mesylate-treated cell suspensions. In control samples, the proportion of cells with an ultrastructure consistent with healthy cells decreased from 70%, immediately after dissociation, to 30% after 8 h of incubation. Similar changes were also observed in cell suspensions treated with neuroprotectants. Thus, the neuroprotectants examined did not block the development of specific morphological signs of neurodegeneration. However, when also taking into account that dead cells lysed and disappeared from each cell suspension with time, we found that the total number of remaining viable cells with healthy nuclear chromatin or intact membrane integrity was significantly higher in the tirilazad mesylate-treated group. The results indicate that tirilazad mesylate protects only a small subpopulation of embryonic mesencephalic cells from degeneration induced by mechanical trauma during tissue dissection and dissociation.

Intracerebral cytokine profiles in adult rats grafted with neural tissue of different immunological disparity

To understand graft rejection in cell based therapies for brain repair we have quantified IL-1beta, IL-2, IL-4, IL-10, IL-12p40, IFN-gamma and TNF-alpha mRNA levels using real-time PCR, at days 4, 14, and 42 post-transplantation, in rats engrafted with syngeneic, allogeneic, concordant and discordant xenogeneic neural tissues. In addition, in the discordant xenografts immunohistochemistry and in situ hybridization were applied to detect local expression of IFN-gamma, TNF-alpha, IL-10 and TGF-beta. Allografts remained non-rejected but expressed IL-1beta, TNF-alpha and IL-4 transcripts but not IL-12p40 and IFN-gamma. Xenografts demonstrated distinct cytokine profiles that differed from syngeneic and allogeneic grafts. Non-rejected discordant xenografts contained higher levels of TNF-alpha transcripts and lower levels of IL-2 transcripts than the rejected ones at day 42. Discordant xenografts displayed a stronger and earlier expression of IL-1beta and TNF-alpha, followed by T-helper 1 and T-helper 2 associated cytokine expression. The number of cells expressing mRNA encoding TNF-alpha and TGF-beta was significantly increased over time in the discordant group. In conclusion, the immunological disparity of the implanted tissue explains survival rates and is associated with different cytokine profiles. In allografts, a chronic inflammatory reaction was detected and in xenogeneic grafts a delayed hypersensitivity like reaction may be involved in rejection.

Involvement of calcineurin in the neurotoxic effects induced by amyloid-beta and prion peptides

It is usually accepted that prion and amyloid-beta (A beta) peptides induce apoptotic cell death. However, the mechanisms that trigger neuronal death, induced by these amyloidogenic peptides, remain to be clarified. In the present study we analysed the neurotoxic effects of the synthetic prion and A beta peptides, PrP106-126 and A beta 25-35, in primary cultures of rat brain cortical cells. PrP106-126 and A beta 25-35 incubated at a concentration of 25 micro m for 24 h, did not affect cell membrane integrity, but decreased the metabolic capacity of the cells. The intracellular free Ca2+ concentration and reactive oxygen species levels increased significantly after 24 h treatment with PrP106-126 and A beta 25-35. Furthermore, these peptides (after 24 h exposure) also induced cytochrome c release from mitochondria and increased caspase-3-like activity. FK506, an inhibitor of the Ca2+/calmodulin-dependent phosphatase, calcineurin, was able to prevent cytochrome c release, caspase-3 activation and cell death induced by A beta 25-35 or PrP106-126 peptides. Taken together these data suggest that calcineurin is involved in A beta 25-35 and PrP106-126 neurotoxicity.

Expression of voltage-dependent calcium channels in the embryonic rat midbrain

The diversity of expression of high-voltage activated voltage-dependent calcium channels (VDCC) was investigated with whole-cell voltage-clamp recordings from dissociated embryonic rat ventral mesencephalic cells over a 7-day culture period. Cell phenotype was identified post-recording by fluorescent immunocytochemistry as tyrosine hydroxylase positive (TH+) or glutamic acid decarboxylase positive (GAD+). Both TH+ and GAD+ cells displayed high-threshold calcium (Ca(2+)) currents activated by depolarisations positive to -60 mV. In both cell types, pharmacological dissection using selective VDCC inhibitors, omega-agatoxin IVA (Aga IVA), omega-conotoxin GVIA (GVIA) and nifedipine demonstrated the existence of P/Q-, N- and L-type VDCC, respectively. The remaining residual current could be blocked by cadmium. It was found that the contribution to the whole-cell current by the N-type channel was greater in TH+ cells than GAD+ cells at each time point examined, whilst the contribution to the whole-cell current by the L-type channel was greater in GAD+ cells than TH+ cells. However, over the 7-day culture period, the expression of VDCC types in both cell phenotypes changed in a similar fashion, with the contribution to the whole-cell current from the N-type current decreasing, and the contribution from the R-type current increasing. Our data could provide new insights into a range of neurodevelopmental mechanisms related to Ca(2+) homeostasis in developing mesencephalic neurons.

Bradykinin receptor agonist facilitates low-dose cyclosporine-A protection against 6-hydroxydopamine neurotoxicity

Cyclosporine-A (CsA) is neuroprotective in animal models of Parkinson's disease (PD), Huntington's disease and stroke. Because CsA does not easily cross the blood-brain barrier (BBB), high doses (i.e. >10 mg/kg in rats) and chronic administration may be necessary to produce beneficial effects. However, immunosuppressant side effects (including nephrotoxicity and hepatotoxicity) are associated with such CsA dosing regimens. The bradykinin B2 receptor agonist, Cereport (labradimil and formerly called RMP-7), transiently increases the permeability of the BBB to facilitate delivery of drugs to the CNS. Here we examined the effects of co-administration of CsA and Cereport in the unilateral 6-OHDA model of PD. Animals were pretreated with vehicle, CsA alone (1 mg/kg, a low dose without either immunosuppressive or neuroprotective effects, or 10 mg/kg, a high dose that produces both immunosuppression and neuroprotection), or CsA (1 mg/kg) in combination with Cereport (9 microg/kg). Behavioral analyses, using elevated body swing and amphetamine-induced rotational tests, revealed that a low dose of CsA was neuroprotective when combined with Cereport, but not when given alone. Tyrosine hydroxylase immunohistochemistry demonstrated that while near complete (>90%) depletions of nigral TH-ir neurons were noted in lesioned animals that received vehicle infusion or low-dose CsA alone, lesioned animals that received low-dose CsA+Cereport exhibited a significant sparing of nigral TH-ir neurons and a marked reduction in the loss of striatal TH-ir fibers. The safer and effective administration of lower doses of CsA combined with enhanced BBB permeability using Cereport, offers a novel way of producing protective effects in the CNS without the toxic liabilities of high-dose CsA.

The immunosuppressant drug FK506 is a potent trophic agent for human fetal neurons

FK506 is a potent immunosuppressive drug used to prevent rejection post-organ transplantation. It is activated upon binding to members of the immunophilin chaperone proteins (e.g. FK506-binding protein, FKBP 12). Studies of the distribution of FKBP12 reveal that it is enriched in neurons throughout the central and peripheral nervous system. In vitro, FK506 augments neurite outgrowth; in animal models, it enhances axonal re-growth and functional recovery following lesioning. The effects on human neurons and glial cells have not yet been studied. Using immunofluorescent laser scanning confocal microscopy we demonstrate that in human fetal brain cultures FK506 significantly increases cell numbers, including neurons, and the expression of the neuronal marker MAP-2. This suggests that the drug has a potent effect in stimulating neuronal survival, proliferation and dendrite extension. Interestingly, in combination with brain-derived neurotrophic factor, FK506 induces a prominent decrease in glial fibrillary acidic protein expression, which indicates an inhibitory effect on astrogliosis in vitro. Our data support a potential role for FK506 and its analogues in the treatment of neurodegenerative disorders.

Liposomal tacrolimus administered systemically and within the donor cell suspension improves xenograft survival in hemiparkinsonian rats

The most widely used immunosuppressant in neural transplantation is cyclosporine- A (CsA). However, CsA has significant toxic effects when administered systemically. Tacrolimus (FK506), is a more potent immunosuppressant than CsA and can be prepared in lipid micelles (LTAC). This liposomal preparation allows for the administration of tacrolimus to the site of transplantation, possibly reducing the systemic side effects of immunosuppression. In this study we investigated the ability of LTAC to promote graft survival in hemiparkinsonian rats implanted with fetal mouse xenografts when LTAC is administered systemically to the host, when added to the donor cell suspension, or in combination. Rats with unilateral 6-hydroxydopamine lesions were transplanted with 800,000 fetal mouse ventral mesencephalic (VM) cells and were randomly divided into four groups. Group 1 was not immunosuppressed; Group 2 received daily systemic injections of LTAC; Group 3 received LTAC within the cell suspensions of mouse VM cells; and Group 4 received LTAC in the cell suspensions along with daily systemic administration of LTAC. Transplanted rats were assessed for rotational behavior 3 and 6 weeks posttransplantation. Cell survival was assessed using tyrosine hydroxylase (TH) immunohistochemistry. A significant reduction in rotational scores was observed only in the group of animals receiving the combination of LTAC-treated donor cells and systemic LTAC administration. This functional improvement correlated with a significantly greater survival of TH-immunoreactive cells in this group of animals. The other groups had poor cell survival and no significant functional improvement. We conclude that a combination of systemic immunosuppression and treatment of the cell suspension with LTAC may be a superior strategy to optimize xenograft survival. This strategy may have important implications for clinical neural transplantation.

Effects of immunosuppressive treatment on host responses against intracerebral porcine neural tissue xenografts in rats

BACKGROUND

Embryonic xenogeneic neural tissue is an alternative for transplantation in Parkinson's disease, but immune responses limit the application. The aims of this study were to enhance the in vitro viability rates by donor tissue pretreatment; to compare the efficacy of cyclosporine A (CsA) and tacrolimus (FK) in inhibiting xenograft rejection in rats; to evaluate additional inductive therapy with prednisolone (PRE) or mycophenolate mofetil (MMF).

METHODS

Tirilazad (a lipid peroxidase inhibitor) or FK and acYVAD-cmk (a caspase inhibitor), were added to embryonic porcine ventral mesencephalic tissue and viability was assessed in vitro. Tirilazad-treated tissue was grafted to the striatum of rats that were either left untreated or immunosuppressed with FK (1 mg/kg) or CsA (15 mg/kg) alone or in combination with a 2-week PRE (20 mg/kg) or MMF (40 mg/kg) induction course. Xenograft survival and host responses were determined using immunohistochemistry.

RESULTS

Pretreatment with tirilazad enhanced tissue survival in vitro. After transplantation into untreated controls, there was no graft survival at twelve weeks. Neural cell counts were significantly improved in immunosuppressed recipients, but there were no differences between the treatment groups. Additional inductive treatment reduced the infiltration with CD4+ and CD8+ cells, and macrophage infiltration was reduced compared with animals given CsA or FK alone.

CONCLUSION

Pretreatment of the donor tissue with free-radical scavengers reduces cell loss caused by tissue trauma. Porcine neural tissue xenografts survive significantly better in animals immunosuppressed with either FK or CsA. Additional inductive treatment with PRE or MMF reduced the infiltration of host cells into the xenografts.

Transplantation therapy for Parkinson's disease

This review paper will provide an overview of the advent of neural transplantation therapy and the milestones achieved over the last 20 years for its use in treating Parkinson's disease. A discussion of technical factors that influence the outcome of neural transplantation is presented, with emphasis given on three sections dealing with immunosuppressants, alternative grafts and trophic factors which have recently been the focus of basic research and development of early phase clinical trials. Some views on the clinical assessment of transplanted Parkinson's disease patients are given at the end of the paper, with a synopsis highlighting the importance of basic research in advancing the potential clinical benefits of neural transplantation therapy in the treatment of Parkinson's disease.