Neurotrophic Enhancers as Therapy for Behavioral Deficits in Rodent Models of Huntington's Disease: Use of Gangliosides, Substituted Pyrimidines, and Mesenchymal Stem Cells

The interest in using neurotrophic factors as potential treatments for neurodegenerative disorders, such as Huntington's disease, has grown in the past decade. A major impediment for the clinical utility of neurotrophic factors is their inability to cross the blood-brain barrier in therapeutically significant amounts. Although several novel mechanisms for delivering exogenous neurotrophins to the brain have been developed, most of them involve invasive procedures or present significant risks. One approach to circumventing these problems is using therapeutic agents that can be administered systemically and have the ability to enhance the activity of neurotrophic factors. This review highlights the use of gangliosides, substituted pyrimidines, and mesenchymal stem cells as neurotrophic enhancers that have significant therapeutic potential while avoiding the pitfalls of delivering exogenous neurotrophic factors through the blood-brain barrier. The review focuses on the potential of these neurotrophic enhancers for treating the behavioral deficits in rodent models of Huntington's disease.

Reductions in behavioral deficits and neuropathology in the R6/2 mouse model of Huntington's disease following transplantation of bone-marrow-derived mesenchymal stem cells is dependent on passage number

Introduction

Huntington’s disease (HD) is an autosomal dominant disorder caused by an expanded CAG repeat (greater than 38) on the short arm of chromosome 4, resulting in loss and dysfunction of neurons in the neostriatum and cortex, leading to cognitive decline, motor dysfunction, and death, typically occurring 15 to 20 years after the onset of motor symptoms. Although an effective treatment for HD has remained elusive, current studies using transplants of bone-marrow-derived mesenchymal stem cells provides considerable promise. This study further investigates the efficacy of these transplants with a focus on comparing how passage number of these cells may affect subsequent efficacy following transplantation.

Methods

In this study, mesenchymal stem cells isolated from the bone-marrow of mice (BM MSCs), were labeled with Hoechst after low (3 to 8) or high (40 to 50) numbers of passages and then transplanted intrastriatally into 5-week-old R6/2 mice, which carries the N-terminal fragment of the human HD gene (145 to 155 repeats) and rapidly develops symptoms analogous to the human form of the disease.

Results

It was observed that the transplanted cells survived and the R6/2 mice displayed significant behavioral and morphological sparing compared to untreated R6/2 mice, with R6/2 mice receiving high passage BM MSCs displaying fewer deficits than those receiving low-passage BM MSCs. These beneficial effects are likely due to trophic support, as an increase in brain derived neurotrophic factor mRNA expression was observed in the striatum following transplantation of BM MSCs.

Conclusion

The results from this study demonstrate that BM MSCs hold significant therapeutic value for HD, and that the amount of time the cells are exposed to in vitro culture conditions can alter their efficacy.

Local control of the host immune response performed with mesenchymal stem cells: perspectives for functional intracerebral xenotransplantation

Foetal pig neuroblasts are interesting candidates as a cell source for transplantation, but xenotransplantation in the brain requires the development of adapted immunosuppressive treatments. As systemic administration of high doses of cyclosporine A has side effects and does not protect xenotransplants forever, we focused our work on local control of the host immune responses. We studied the advantage of cotransplanting syngenic mesenchymal stem cells (MSC) with porcine neuroblasts (pNb) in immunocompetent rat striata. Two groups of animals were transplanted, either with pNb alone or with both MSC and pNb. At day 63, no porcine neurons were detected in the striata that received only pNb, while four of six rats transplanted with both pNb and MSC exhibited healthy porcine neurons. Interestingly, 50% of the cotransplanted rats displayed healthy grafts with pNF70+ and TH+ neurons at 120 days post-transplantation. qPCR analyses revealed a general dwindling of pro- and anti-inflammatory cytokines in the striata that received the cotransplants. Motor recovery was also observed following the transplantation of pNb and MSC in a rat model of Parkinson's disease. Taken together, the present data indicate that the immunosuppressive properties of MSC are of great interest for the long-term survival of xenogeneic neurons in the brain.

Intrastriatal transplantation of adenovirus-generated induced pluripotent stem cells for treating neuropathological and functional deficits in a rodent model of Huntington's disease

Induced pluripotent stem cells (iPSCs) show considerable promise for cell replacement therapies for Huntington's disease (HD). Our laboratory has demonstrated that tail-tip fibroblasts, reprogrammed into iPSCs via two adenoviruses, can survive and differentiate into neuronal lineages following transplantation into healthy adult rats. However, the ability of these cells to survive, differentiate, and restore function in a damaged brain is unknown. To this end, adult rats received a regimen of 3-nitropropionic acid (3-NP) to induce behavioral and neuropathological deficits that resemble HD. At 7, 21, and 42 days after the initiation of 3-NP or vehicle, the rats received intrastriatal bilateral transplantation of iPSCs. All rats that received 3-NP and vehicle treatment displayed significant motor impairment, whereas those that received iPSC transplantation after 3-NP treatment had preserved motor function. Histological analysis of the brains of these rats revealed significant decreases in optical densitometric measures in the striatum, lateral ventricle enlargement, as well as an increase in striosome size in all rats receiving 3-NP when compared with sham rats. The 3-NP-treated rats given transplants of iPSCs in the 7- or 21-day groups did not exhibit these deficits. Transplantation of iPSCs at the late-stage (42-day) time point did not protect against the 3-NP-induced neuropathology, despite preserving motor function. Transplanted iPSCs were found to survive and differentiate into region-specific neurons in the striatum of 3-NP rats, at all transplantation time points. Taken together, these results suggest that transplantation of adenovirus-generated iPSCs may provide a potential avenue for therapeutic treatment of HD.

Transplantation of umbilical cord-derived mesenchymal stem cells into the striata of R6/2 mice: behavioral and neuropathological analysis

Introduction

Huntington’s disease (HD) is an autosomal dominant disorder caused by an expanded CAG repeat on the short arm of chromosome 4 resulting in cognitive decline, motor dysfunction, and death, typically occurring 15 to 20 years after the onset of motor symptoms. Neuropathologically, HD is characterized by a specific loss of medium spiny neurons in the caudate and the putamen, as well as subsequent neuronal loss in the cerebral cortex. The transgenic R6/2 mouse model of HD carries the N-terminal fragment of the human HD gene (145 to 155 repeats) and rapidly develops some of the behavioral characteristics that are analogous to the human form of the disease. Mesenchymal stem cells (MSCs) have shown the ability to slow the onset of behavioral and neuropathological deficits following intrastriatal transplantation in rodent models of HD. Use of MSCs derived from umbilical cord (UC) offers an attractive strategy for transplantation as these cells are isolated from a noncontroversial and inexhaustible source and can be harvested at a low cost. Because UC MSCs represent an intermediate link between adult and embryonic tissue, they may hold more pluripotent properties than adult stem cells derived from other sources.

Methods

Mesenchymal stem cells, isolated from the UC of day 15 gestation pups, were transplanted intrastriatally into 5-week-old R6/2 mice at either a low-passage (3 to 8) or high-passage (40 to 50). Mice were tested behaviorally for 6 weeks using the rotarod task, the Morris water maze, and the limb-clasping response. Following behavioral testing, tissue sections were analyzed for UC MSC survival, the immune response to the transplanted cells, and neuropathological changes.

Results

Following transplantation of UC MSCs, R6/2 mice did not display a reduction in motor deficits but there appeared to be transient sparing in a spatial memory task when compared to untreated R6/2 mice. However, R6/2 mice receiving either low- or high-passage UC MSCs displayed significantly less neuropathological deficits, relative to untreated R6/2 mice.

Conclusions

The results from this study demonstrate that UC MSCs hold promise for reducing the neuropathological deficits observed in the R6/2 rodent model of HD.

Survival and differentiation of adenovirus-generated induced pluripotent stem cells transplanted into the rat striatum

Induced pluripotent stem cells (iPSCs) offer certain advantages over embryonic stem cells in cell replacement therapy for a variety of neurological disorders. However, reliable procedures, whereby transplanted iPSCs can survive and differentiate into functional neurons, without forming tumors, have yet to be devised. Currently, retroviral or lentiviral reprogramming methods are often used to reprogram somatic cells. Although the use of these viruses has proven to be effective, formation of tumors often results following in vivo transplantation, possibly due to the integration of the reprogramming genes. The goal of the current study was to develop a new approach, using an adenovirus for reprogramming cells, characterize the iPSCs in vitro, and test their safety, survivability, and ability to differentiate into region-appropriate neurons following transplantation into the rat brain. To this end, iPSCs were derived from bone marrow-derived mesenchymal stem cells and tail-tip fibroblasts using a single cassette lentivirus or a combination of adenoviruses. The reprogramming efficiency and levels of pluripotency were compared using immunocytochemistry, flow cytometry, and real-time polymerase chain reaction. Our data indicate that adenovirus-generated iPSCs from tail-tip fibroblasts are as efficient as the method we used for lentiviral reprogramming. All generated iPSCs were also capable of differentiating into neuronal-like cells in vitro. To test the in vivo survivability and the ability to differentiate into region-specific neurons in the absence of tumor formation, 400,000 of the iPSCs derived from tail-tip fibroblasts that were transfected with the adenovirus pair were transplanted into the striatum of adult, immune-competent rats. We observed that these iPSCs produced region-specific neuronal phenotypes, in the absence of tumor formation, at 90 days posttransplantation. These results suggest that adenovirus-generated iPSCs may provide a safe and viable means for neuronal replacement therapies.

Early cognitive dysfunction in the HD 51 CAG transgenic rat model of Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder in humans caused by an expansion of a CAG trinucleotide repeat that produces choreic movements, which are preceded by cognitive deficits. The HD transgenic rat (tgHD), which contains the human HD mutation with a 51 CAG repeat allele, exhibits motor deficits that begin when these rats are 12 months of age. However, there are no reports of cognitive dysfunction occurring prior to this. To assess whether cognitive dysfunction might precede motor deficits in tgHD rats, one group of 9-month-old male rats with homozygotic mutated genes and one group of wild-type (WT) rats underwent three testing phases in a unique Spatial Operant Reversal Test (SORT) paradigm, as well as assessment of spontaneous motor activity. After testing, morphological and histological examination of the brains were made. Results indicated that tgHD rats acquired the cued-response (Phase 1) portion of the SORT, but made significantly more errors during the reversal (Phase 2) and during the pseudorandomized reversals (Phase 3) portion of the study, when compared to WT rats. Analysis of the data using mathematical principles of reinforcement revealed no memory, motor, or motivational deficits. These results indicate that early cognitive dysfunction, as measured by the SORT, occur prior to motor deficits, gross anatomical changes, or cell loss in the tgHD rat with 51 CAG repeats, and suggest that this protocol could provide a useful screen for therapeutic studies.

Assessing the potential clinical utility of transplantations of neural and mesenchymal stem cells for treating neurodegenerative diseases

Treatments for neurodegenerative diseases have little impact on the long-term patient health. However, cellular transplants of neuroblasts derived from the aborted embryonic brain tissue in animal models of neurodegenerative disorders and in patients have demonstrated survival and functionality in the brain. However, ethical and functional problems due to the use of this fetal tissue stopped most of the clinical trials. Therefore, new cell sources were needed, and scientists focused on neural (NSCs) and mesenchymal stem cells (MSCs). When transplanted in the brain of animals with Parkinson's or Huntington's disease, NSCs and MSCs were able to induce partial functional recovery by promoting neuroprotection and immunomodulation. MSCs are more readily accessible than NSCs due to sources such as the bone marrow. However, MSCs are not capable of differentiating into neurons in vivo where NSCs are. Thus, transplantation of NSCs and MSCs is interesting for brain regenerative medicine. In this chapter, we detail the methods for NSCs and MSCs isolation as well as the transplantation procedures used to treat rodent models of neurodegenerative damage.

The use of stem cells in regenerative medicine for Parkinson's and Huntington's Diseases

Cell transplantation has been proposed as a means of replacing specific cell populations lost through neurodegenerative processes such as that seen in Parkinson's or Huntington's diseases. Improvement of the clinical symptoms has been observed in a number of Parkinson and Huntington's patients transplanted with freshly isolated fetal brain tissue but such restorative approach is greatly hampered by logistic and ethical concerns relative to the use of fetal tissue, in addition to potential side effects that remain to be controlled. In this context, stem cells that are capable of self-renewal and can differentiate into neurons, have received a great deal of interest, as demonstrated by the numerous studies based on the transplantation of neural stem/progenitor cells, embryonic stem cells or mesenchymal stem cells into animal models of Parkinson's or Huntington's diseases. More recently, the induction of pluripotent stem cells from somatic adult cells has raised a new hope for the treatment of neurodegenerative diseases. In the present article, we review the main experimental approaches to assess the efficiency of cell-based therapy for Parkinson's or Huntington's diseases, and discuss the recent advances in using stem cells to replace lost dopaminergic mesencephalic or striatal neurons. Characteristics of the different stem cells are extensively examined with a special attention to their ability of producing neurotrophic or immunosuppressive factors, as these may provide a favourable environment for brain tissue repair and long-term survival of transplanted cells in the central nervous system. Thus, stem cell therapy can be a valuable tool in regenerative medicine.

Effects of Human Alpha-Synuclein A53T-A30P Mutations on SVZ and Local Olfactory Bulb Cell Proliferation in a Transgenic Rat Model of Parkinson Disease

A transgenic Sprague Dawley rat bearing the A30P and A53T α-synuclein (α-syn) human mutations under the control of the tyrosine hydroxylase promoter was generated in order to get a better understanding of the role of the human α-syn mutations on the neuropathological events involved in the progression of the Parkinson's disease (PD). This rat displayed olfactory deficits in the absence of motor impairments as observed in most early PD cases. In order to investigate the role of the mutated α-syn on cell proliferation, we focused on the subventricular zone (SVZ) and the olfactory bulbs (OB) as a change of the proliferation could affect OB function. The effect on OB dopaminergic innervation was investigated. The human α-syn co-localized in TH-positive OB neurons. No human α-syn was visualized in the SVZ. A significant increase in resident cell proliferation in the glomerular but not in the granular layers of the OB and in the SVZ was observed. TH innervation was significantly increased within the glomerular layer without an increase in the size of the glomeruli. Our rat could be a good model to investigate the role of human mutated α-syn on the development of olfactory deficits.

Mesenchymal stem cell transplantation and DMEM administration in a 3NP rat model of Huntington's disease: morphological and behavioral outcomes

Transplantation of mesenchymal stem cells (MSCs) may offer a viable treatment for Huntington's disease (HD). We tested the efficacy of MSC transplants to reduce deficits in a 3-nitropropionic acid (3NP) rat model of HD. Five groups of rats (Sham, 3NP, 3NP+vehicle, 3NP+TP(low), 3NP+TP(high)), were given PBS or 3NP intraperitoneally, twice daily for 42 days. On day 28, rats in all groups except Sham and 3NP, received intrastriatal injections of either 200,000 MSCs (TP(low)), 400,000 (TP(high)) MSCs or DMEM (VH, the vehicle for transplantation). MSCs survived 72 days without inducing a strong inflammatory response from the striatum. Behavioral sparing was observed on tests of supported-hindlimb-retraction, unsupported-hindlimb-retraction, visual paw placement and stepping ability for 3NP+TP(low) rats and on the unsupported-hindlimb-retraction and rotarod tasks for 3NP+VH rats. Relative to 3NP controls, all treated groups were protected from 3NP-induced enlargement of the lateral ventricles. In vitro, MSCs expressed transcripts for numerous neurotrophic factors. In vivo, increased striatal labeling in BDNF, collagen type-I and fibronectin (but not GDNF or CNTF) was observed in the brains of MSC-transplanted rats but not in DMEM-treated rats. In addition, none of the transplanted MSCs expressed neural phenotypes. These findings suggest that factors other than neuronal replacement underlie the behavioral sparing observed in 3NP rats after MSC transplantation.

Mesenchymal stem cells induce a weak immune response in the rat striatum after allo or xenotransplantation

Mesenchymal stem cells (MSCs) have attracted attention for their potential use in regenerative medicine such as brain transplantation. As MSCs are considered to be hypoimmunogenic, transplanted MSCs should not trigger a strong host inflammatory response. To verify this hypothesis, we studied the brain immune response after transplantation of human or rat MSCs into the rat striatum and MSC fate at days 5, 14, 21 and 63 after transplantation. Flow cytometry analysis indicated that both MSCs express CD90 and human leucocyte antigen (MHC) class I, but no MHC class II molecules. They do not express CD45 or CD34 antigens. However, MSC phenotype varies with passage number. Human MSCs have mRNAs for interleukin (IL)-6, IL-8, IL-12, tumour necrosis factor (TNF)-alpha and TGF-beta(1), whereas rat MSCs express IL-6-, IL-10-, IL-12- and TGF-beta(1)-mRNAs. The quantification shows higher levels of mRNAs for the anti-inflammatory molecules IL-6 and TGF-beta(1) than for pro-inflammatory cytokines IL-8 and IL-12; ELISA analysis showed no IL-12 whereas TGF-beta(1) and IL-6 were detected. Transplant size did not significantly vary between 14 and 63 days after transplantation, indicating an absence of immune rejection of the grafts. Very few mast cells and moderate macrophage and microglial infiltrations, observed at day 5 remained stable until day 63 after transplantation in both rat and human MSC grafts. The observations of very few dendritic cells, T alphabeta-cells, and no T gammadelta-lymphocytes, all three being associated with Tp rejection in the brain, support the contention that MSCs are hypoimmunogenic. Our results suggest that MSCs are of great interest in regenerative medicine in a (xeno)transplantation setting.

Genetically engineered mesenchymal stem cells reduce behavioral deficits in the YAC 128 mouse model of Huntington's disease

The purpose of this study was to evaluate the therapeutic effects of the transplantation of bone-marrow mesenchymal stem cells (MSCs), genetically engineered to over-express brain-derived neurotrophic factor (BDNF) or nerve growth factor (NGF) on motor deficits and neurodegeneration in YAC 128 transgenic mice. MSCs, harvested from mouse femurs, were genetically engineered to over-express BDNF and/or NGF and these cells, or the vehicle solution, were injected into the striata of four-month old YAC 128 transgenic and wild-type mice. Assessments of motor ability on the rotarod and the severity of clasping were made one day prior to transplantation and once monthly, thereafter, to determine the effects of the transplanted cells on motor function. The mice were sacrificed at 13-months of age for immunohistological examination. All YAC 128 mice receiving transplants had reduced clasping, relative to vehicle-treated YAC 128 mice, while YAC 128 mice that were transplanted with MSCs which were genetically engineered to over-express BDNF, had the longest latencies on the rotarod and the least amount of neuronal loss within the striatum of the YAC 128 mice. These results indicate that intrastriatal transplantation of MSCs that over-express BDNF may create an environment within the striatum that slows neurodegenerative processes and provides behavioral sparing in the YAC 128 mouse model of HD. Further research on the long-term safety and efficacy of this approach is needed before its potential clinical utility can be comprehensively assessed.

New lines of GFP transgenic rats relevant for regenerative medicine and gene therapy

Adoptive cell transfer studies in regenerative research and identification of genetically modified cells after gene therapy in vivo require unequivocally identifying and tracking the donor cells in the host tissues, ideally over several days or for up to several months. The use of reporter genes allows identifying the transferred cells but unfortunately most are immunogenic to wild-type hosts and thus trigger rejection in few days. The availability of transgenic animals from the same strain that would express either high levels of the transgene to identify the cells or low levels but that would be tolerant to the transgene would allow performing long-term analysis of labelled cells. Herein, using lentiviral vectors we develop two new lines of GFP-expressing transgenic rats displaying different levels and patterns of GFP-expression. The "high-expresser" line (GFP(high)) displayed high expression in most tissues, including adult neurons and neural precursors, mesenchymal stem cells and in all leukocytes subtypes analysed, including myeloid and plasmacytoid dendritic cells, cells that have not or only poorly characterized in previous GFP-transgenic rats. These GFP(high)-transgenic rats could be useful for transplantation and immunological studies using GFP-positive cells/tissue. The "low-expresser" line expressed very low levels of GFP only in the liver and in less than 5% of lymphoid cells. We demonstrate these animals did not develop detectable humoral and cellular immune responses against both transferred GFP-positive splenocytes and lentivirus-mediated GFP gene transfer. Thus, these GFP-transgenic rats represent useful tools for regenerative medicine and gene therapy.

Rat model of Parkinson's disease with bilateral motor abnormalities, reversible with levodopa, and dyskinesias

Parkinson's disease (PD) is characterized by the bilateral degeneration of the midbrain dopamine-containing neurons with the most severe lesion in the posterolateral part of the substantia nigra pars compacta (SNpc). In humans, such lesions lead to specific motor abnormalities (i.e., akinesia, rigidity, and tremor) that are greatly improved by levodopa treatment. After a few years, the beneficial effect of the treatment is frequently offset by the development of dyskinesias. To improve treatment strategies, an animal model showing most of the histological and clinical characteristics of the human disease is mandatory. Ten rats received a bilateral injection of small doses of 6-OHDA in the medial forebrain bundle (MFB) and were compared with five sham-lesioned rats. The 6-OHDA-lesioned rats progressively developed abnormal motor behavior (assessed by the stepping test) compared with the sham-lesioned rats. The lesioned rats greatly improved under levodopa treatment, but developed concomitant dyskinesias. All 6-OHDA-lesioned animals had bilateral partial lesions of the SNpc, with the most severe lesion being in its posterolateral part. There was a significant correlation between the severity of the dopaminergic cell loss and the severity of the levodopa-induced dyskinesias. These rats constitute an interesting model of PD, sharing some of the main characteristics of the human disease.

The novel substituted pyrimidine, KP544, reduces motor deficits in the R6/2 transgenic mouse model of Huntington's disease

PURPOSE

The purpose of this study was to test the potential therapeutic effects of the substituted pyrimidine, KP544, which has been shown to amplify the effects of nerve growth factor in vitro, on motor deficits in the R6/2 transgenic mouse model of Huntington's disease (HD).

METHODS

Young, female R6/2 mice were given daily oral intubation of either 10 mg/kg KP544 or vehicle (0.5% methylcellulose) at 6 weeks of age and tested from postnatal weeks 8 through 12 on a battery of motor tasks, including assessments of clasping (drawing of the limbs to the torso when suspended by the tail), motor coordination on the rotarod, and spontaneous motor activity in the open-field. Following testing, the mice were sacrificed and the brains were sectioned and stained with cresyl violet for histological examination.

RESULTS

KP544 treatment decreased balance deficits on the rotarod task, reduced clasping, delayed the onset of hypoactivity, and reduced enlargement of the lateral ventricles in R6/2 mice.

CONCLUSION

These results suggest that KP544 can reduce motor deficits and anatomical alterations in R6/2 mice. Further research into the use of KP544 as a potential pharmacotherapy HD is warranted.

Soluble factors from neuronal cultures induce a specific proliferation and resistance to apoptosis of cognate mouse skeletal muscle precursor cells

The mechanisms or the physiological events, which control the regeneration of skeletal muscle through muscle precursor cell multiplication and differentiation, are still largely unknown. To address the question of the involvement of neurons in this process, skeletal muscle progenitors were grown in the presence of conditioned media obtained from 3-day-old cultures of embryonic neurons (derived from either the dorsal or the ventral region of 11-day-old mouse embryos) or media conditioned with satellite cells. Strikingly, only satellite cells cultured in medium conditioned from ventral embryonic neurons exhibited increased proliferation, as well as resistance to staurosporine (STS)-induced apoptosis. Our results suggest the existence of specific anti-apoptogenic neural soluble signals, which could be involved in skeletal muscle regeneration pathways.

Autologous adult bone marrow stem cell transplantation in an animal model of huntington's disease: behavioral and morphological outcomes

We investigated the effects of autologous bone marrow stem cell transplantation in a rat model of Huntington's Disease. Thirteen days after bilateral quinolinic lesions (QA), bone marrow was implanted into the damaged striatum. The ability of the transplants to reverse QA-induced cognitive deficits in the radial-arm water maze (RAWM) was examined. The transplants significantly reduced working memory deficits. Most of the transplanted cells appeared quite primitive. Because only a few cells expressed neural phenotypes, we suggest that the release of growth factors by the transplants allowed surviving cells within the caudate to function more efficiently and to facilitate other compensatory responses.

Differences in memory impairment and response to GM1 ganglioside treatment following electrolytic or ibotenic acid lesions of the nucleus basalis magnocellularis

Alzheimer's disease is a progressive dementia associated with cholinergic cell loss in the nucleus of Meynert that induces deficiencies in cholinergic neurotransmission in the neocortex. The nucleus basalis magnocellularis (NBM) is the rodent homologue to the nucleus of Meynert in humans. In this study, we examined the effects of GM1 ganglioside, a neuroprotective agent, on morphological and functional recovery after electrolytic or ibotenic acid lesions of the NBM. In animals, GM1 ganglioside has been shown to reduce some of the behavioral deficits that follow Central Nervous System lesions. Electrolytic or ibotenic acid lesions produced deficits in passive avoidance learning, as assessed by the number of trails taken to acquire the avoidance response. Only the electrolytic lesions impaired spatial memory in the Morris Water Maze (MWM), and GM1 administration did not improve performance on this task. Facilitation of passive avoidance acquisition was observed in animals receiving GM1 treatment after electrolytic or ibotenate lesions. Both types of injuries induced equivalent amounts of damage to the nucleus basalis but the electrolytic lesions produced greater damage to adjacent structures that could be responsible for the additional deficits observed on the MWM task.

Behavioral and morphological consequences of primary astrocytes transplanted into the rat cortex immediately after nucleus basalis ibotenic lesion

Adult male rats received transplants of dissociated 30-day old cultured cortical astrocytes into the ipsilateral frontal and parietal cortex immediately after unilateral ibotenic acid lesion of the NBM or after sham injury. We hypothesized that transplants of astrocytes into the acetylcholine-deprived cortex might provide trophic support to terminals arising from damaged NBM neurons. Twenty four hours after transplantation and every other day for 11 days post surgery, the animals were tested for locomotion and habituation in an open field. NBM lesion reduced vertical movements only as compared to no lesion and no transplant counterparts. Nine days after surgery rats with NBM lesion and astrocyte-transplants into the cortex were as impaired in the acquisition of a passive avoidance (PA) task as untreated counterparts. Animals with no lesions and transplants into the cortex also had significant PA acquisition deficits. All rats with ibotenic lesion were significantly impaired on PA retention as compared to rats with no lesions. Astrocyte-transplants survived up to 2 months after cortical implantation but these transplants produced severe laminar disruption and gliosis. This effect was greater in rats with NBM lesion than in intact animals with transplants into the cortex. These data show that astrocyte-transplants do not promote functional recovery after NBM lesion and suggest an immune rejection of the astrocyte transplants by the host brain.

Macrophages enhance muscle satellite cell proliferation and delay their differentiation

This study investigated the effect of macrophages on in vitro satellite cell myogenesis in the turkey and mouse. Macrophages are considered to act as scavengers of tissue debris during the muscle degeneration-regeneration process. The number of dividing cells and of myoblasts expressing the myogenic regulatory factor MyoD indicated that macrophages enhanced satellite cell proliferation in both species. This was confirmed by observations with cultures treated for bromodeoxyuridine (BrdU) incorporation. In mouse and turkey macrophage-satellite cell cocultures, the number of differentiated myoblasts, the frequency of myogenin-positive cells, and the expression of developmental myosin isoforms were reduced as compared with control cultures, indicating that macrophages delayed satellite cell differentiation. The possibility that macrophages facilitate muscle fiber reconstitution by enhancing satellite cell proliferation should be taken into consideration in designing future strategies of satellite cell transplantation as a treatment for muscular dystrophies.

Blood borne macrophages are essential for the triggering of muscle regeneration following muscle transplant

The transplantation of satellite cells may constitute a strategy for rebuilding muscle fibres in inherited myopathies. However, its development requires a great understanding of the role of environmental signals in the regenerative process. It is therefore essential to identify the key events triggering and controlling this process in vivo. We investigated whether macrophages play a key role in the course of the regenerative process using skeletal muscle transplants from transgenic pHuDes-nls-LacZ mice. Before grafting, transplants were conditioned with macrophage inflammatory protein 1-beta (MIP 1-beta; stimulating the macrophages infiltration or vascular endothelial growth factor (VEGF) stimulating angiogenesis). Treatment of transplants with MIP 1-beta and VEGF both accelerated and augmented monocyte-macrophage infiltration and satellite cell differentiation and/or proliferation, as compared to controls. In addition, VEGF treatment enhanced the number of newly formed myotubes. When a complete depletion of host monocyte-macrophages was experimentally induced, no regeneration occurred in transplants. Our data suggest that the presence of blood borne macrophages is required for triggering the earliest events of skeletal muscle regeneration. The understanding of macrophage behaviour after muscle injury should allow us to develop future strategies of satellite cell transplantation as a treatment for muscular dystrophies.

MyoD, myogenin, and desmin-nls-lacZ transgene emphasize the distinct patterns of satellite cell activation in growth and regeneration

Although satellite cell differentiation is involved in postnatal myogenesis from growth to posttrauma regeneration, the early stages of this process remain unclear. This study investigated pHuDes-nls-lacZ transgene activity, as revealed by X-gal staining and the accumulation of MyoD, myogenin, endogenous desmin, and myosin, in order to determine whether satellite cells share the same activation program during growth and regeneration. After birth, skeletal myonuclei in which myogenin expression was limited were briefly characterized by transgene activity. Satellite cells were only evidenced by MyoD and slow myosin accumulation, but failed to initiate transgene expression. After freeze trauma, satellite cell activation led to MyoD, myogenin, and desmin expression. Subsequently, when myosin expression occurred, transgene activation was apparent in regenerating structures, with more intense X-gal staining in mononucleated cells than regenerating myotubes. After the second week posttrauma, only desmin and myogenin expression were maintained in regenerating structures. In culture, the behavior of satellite cells showed that desmin expression was committed before transgene activation occurred, i.e., concurrently with MyoD, myogenin, myosin expression, and the first fusion events. Quantitative analysis confirmed the discrepancy between endogenous desmin and transgene expression and demonstrated the close correlation between transgene activation and the fusion index. Our results strongly suggest that satellite cells promote distinct pathways of myogenic response during growth and regeneration.

Desmin-lacZ transgene expression and regeneration within skeletal muscle transplants

The purpose of this study was to investigate the initiation and time course of the regeneration process in fragments of skeletal muscle transplants as a function of muscle tissue age at implantation. The appearance of desmin occurs at the very beginning of myogenesis. The transgenic desmin nls lacZ mice used in the study bear a transgene in which the 1 kb DNA 5' regulatory sequence of the desmin gene is linked to a reporter gene coding for Escherichia coli beta-galactosidase. The desmin lacZ transgene labels muscle cells in which the desmin synthesis programme has commenced. We implanted pectoralis muscle fragments from fetal transgenic embryos and mature and old transgenic mice into mature non-transgenic mice. Early events of myogenesis occurring during regeneration started sooner in transplants from 4-month-old (day 3 post-implantation) muscle than in those from 24-month-old (day 5-6 post-implantation) muscle, and they lasted longer in those from young (day 17 post-implantation) than in those from old (day 14 post-implantation) muscle fragments. In adult muscle, transgene activation proceeded from the periphery toward the centre of the transplant. In transplants from fetal 18-day-old pectoralis, myotubes with transgene activity were observed from day 1 to day 19. Desmin immunoreactivity, which appeared about one day after transgene activation, was followed by myosin expression. In adult transplants, the continuity of laminin labelling was disrupted around degenerative fibres, illustrating alteration of the extracellular matrix. Our data suggest that satellite cells from old muscle tissue have lower proliferative capacity and/or less access to trophic substances released by the host (damaged fibres, vascularization) than those from fetal or young adult muscle.

Astrocytes grafted into rat nucleus basalis magnocellularis immediately after ibotenic acid injection fail to survive and have no effect on functional recovery

In order to determine if the "trophic" properties of astrocytes makes them appropriate for use as a therapeutic agent to excitotoxic brain damage, adult male rats received grafts of cultured cerebral cortical astrocytes into the NBM immediately after infusion of ibotenic acid into the same structure. Twenty four hours after grafting and every other day for 11 days post surgery, the animals were tested for locomotor activity and habituation in an open field. Animals with NBM lesions had significantly reduced rearing activity as compared to counterparts with no lesions. Nine days after surgery, rats with NBM lesions and astrocyte grafts were as impaired in the acquisition of passive avoidance (PA) as their untreated counterparts. All animals with ibotenic lesions were impaired on PA retention compared to rats with no lesions. There was no difference between animals that had received grafts and those that had not. Fourteen days after grafting, all brains were processed for Nissl stain, acetylcholinesterase (AChE) histochemistry, GFAP immunocytochemistry, and bisbenzamide fluorescent microscopy. Decreases in the number of neurons in the NBM as well as decreases in the density of AChE staining in the ipsilateral cortex (the area of innervation of the NBM cholinergic neurons) was evident in all animals with NBM lesions. In addition, a large number of host reactive astrocytes were seen within the NBM, its vicinity, and in the ipsilateral neocortex. Grafted astrocytes survived and integrated into the host tissue when they were grafted into the brain of intact animals but no living grafted astrocytes were found in animals injected with ibotenate. In this latter case, two weeks after grafting, instead of surviving astrocytes only fluorescent tissue 'masses' were seen in the NBM, surrounded by a cavity. Grafted astrocytes did not have any effect on the extension of the lesion caused by ibotenic acid infusion. These results suggest that the concentration of ibotenic acid used to injure the NBM killed not only the host cholinergic neurons but also the grafted astrocytes. The failure of astrocytes to ameliorate the behavioral deficits caused by ibotenic acid lesions of the NBM may be due to the ibotenic acid creating a lethal environment for the grafted and freshly dissociated, cultured astrocytes.

Desmin-lacZ transgene, a marker of regenerating skeletal muscle

Transgenic C57 mice bearing a transgene of the desmin gene linked to the lacZ reporter gene which encoded for the enzyme beta-galactosidase were used. In the muscle cell, a blue nuclear product appearing in the presence of the X-gal substrate for the enzyme provided evidence of the expression of the desmin gene. However, no transgene expression was observed 2 weeks postnatal in skeletal muscles, even though endogenous desmin was present. In order to investigate the regulatory mechanisms of the desmin gene during regeneration, adult pectoralis fragments (without expression of the desmin transgene) from transgenic mice were implanted into the tibialis anterior of 4 day or 6 week old Swiss mice. Adult pectoralis transplants reexpressed the transgene from day 4 to 10 after implantation. In addition, lesions were performed in adult transgenic pectoralis and transgenic expression in injured muscles was observed 2 days later. This new transgenic mouse is a powerful tool for the study of the various steps of skeletal muscle regeneration.

Effects of fetal forebrain transplants in ibotenic-injured nucleus basalis: an anatomical investigation

Survival of fetal basal forebrain transplant (TP) into ibotenic-injured nucleus basalis of rats was examined after a delay lesion and TP (1 or 2 weeks) and a delay between harvest and TP (1-4.5 hours). Optimal TP survival occurred for TP made 2 weeks postlesion and less than 2 hours after harvesting. In these cases large, healthy TP-neurons displayed robust cytochrome oxidase (CO) activity and sent cholinergic processes throughout the TP and occasionally into host tissue. A mild astrocytic reaction was observed within the TP and at the host-TP interface. Surviving TPs increased choline acetyltransferase innervation and CO activity within the ipsilateral frontoparietal cortex. Therefore data suggest that fetal cholinergic TPs into the damaged NBM reduced neuronal degeneration within the NBM and stimulated remaining neurons spared by the lesion.

Unilateral cortical contusion injury in the rat: vascular disruption and temporal development of cortical necrosis

Cerebrovascular disruption and cortical pathology resulting from either moderate (M-TBI) or severe (S-TBI) traumatic brain injury produced by a pneumatically-driven cortical contusion device were assessed in adult male rats sacrificed at 6 and 24 h or 8 and 30 days after injury to the right sensorimotor cortex. Epidural, subdural, subarachnoid, petechial (cortex and corpus callosum), and/or intraventricular hemorrhage was present in all animals, more extensively and severely following S-TBI. At 6 or 24 h after TBI, acidophilic (acid fuchsin-positive) neurons were numerous and widespread (S-TBI > M-TBI) in the ipsilateral contused cortex. By 8 days few acidophilic neurons were present in peri-impact regions of the ipsilateral neocortex, and none were detected in cortex 30 days postinjury. Both M-TBI and S-TBI groups had enlarged ipsilateral cortical volumes (edema) at 6 and 24 h post-contusion. Eight and 30 days after injury the mean volume of cortical necrosis was significantly larger in S-TBI than in M-TBI rats, and cortical necrosis in both TBI conditions increased between 8 to 30 days postinjury. These results indicate that this pneumatically-driven contusion device produces reliable and consistent primary and secondary cortical histopathology, the extent of which is related to the severity of initial injury.

GM1 ganglioside effects on astroglial response in the rat nucleus basalis magnocellularis and its cortical projection areas after electrolytic or ibotenic lesions

We examined the effects of chronic GM1 ganglioside injections on the astroglial response to bilateral electrolytic or ibotenic acid lesions in the nucleus basalis magnocellularis (NBM) within the NBM and in three cortical projection areas of NBM neurons. Glial fibrillary acidic protein (GFAP) immunohistochemistry was used to visualize the reactive astrocytes. Twenty-six days after injury, extensive astrogliosis was observed within the NBM after both types of lesions. An increased number of GFAP-positive cells were found in the cortex of saline-treated rats following electrolytic but not ibotenic lesions. We suggest that the loss of fibers of passage within the lesion area may account for the difference in cortical gliosis following the two types of damage. Although 17 days of GM1 injections did not affect astrocyte morphology within the NBM, ganglioside treatment reduced the number of GFAP-positive cells after electrolytic but not after ibotenic lesions. Within the cortex, a decrease in GFAP immunoreactivity, size, and number of astrocytes was only observed after electrolytic lesion. These data indicate that a decrease in the astroglial response to injury is the result of an interaction between the type of injury (electrolytic lesion) and chronic GM1 treatment.

Differential effects of chronic ethanol consumptions or thiamine deficiency on spatial working memory in Balb/c mice: a behavioral and neuroanatomical study

This study was aimed to compare the effects of either a thiamine deficiency or a chronic ethanol consumption on memory and on neuronal density within the median mammillary nucleus. Results showed that alcohol-treated (48 weeks) mice exhibited a behavioral impairment in a sequential alternation task characterized by a progressive decay of alternation rates as a function of the number of trials; such a deficit was not observed in controls and thiamine-deficient subjects. A quantitative analysis using histological sections showed an important reduction of neuronal density within the mammillary bodies following the alcohol treatment but not following thiamine deficiency.

Functional recovery following transplants of embryonic brain tissue in rats with lesions of visual, frontal and motor cortex: problems and prospects for future research

In animals, fetal brain tissue grafts into damaged adult host brain reduce some of the functional deficits caused by brain lesions. Although neurons from transplants survive and develop reciprocal connections with host brain tissue, such connections are generally not enough to replace damaged fibers completely and support behavioral recovery observed. Moreover, grafts never exhibit a normal morphological appearance as compared to adult tissue, but some metabolic activity is occasionally detected within the transplant. Release and/or diffusion of trophic substances from the transplant, in addition to those from the damage host brain, may partially restore neuronal and behavioral functions especially after lesions of the visual cortex. In this case, it can be hypothesized that fetal transplants serve as "living mini-pumps". In addition, there is evidence that the combination of trophic substances (e.g. GM1 ganglioside) and fetal brain transplants may provide a better opportunity for recovery than either treatment given by itself.

Modifications in number and morphology of dendritic spines resulting from chronic ethanol consumption and withdrawal: a Golgi study in the mouse anterior and posterior hippocampus

Using Golgi-impregnated mice brains, the effects of 2.5, 6.5, and 9.5 months of chronic ethanol consumption were investigated with regard to morphology and number of dendritic spines of CA1 hippocampal pyramidal neurons. The posterior part of the hippocampus was more sensitive to the effects of ethanol consumption than the anterior one. In the posterior part of the structure, the number of dendritic spines was reduced by 25 and 33% after 6.5 and 9.5 months of treatment, respectively, as compared to age-matched controls. Moreover, the remaining spines appeared shorter than normal. After 9 months of ethanol treatment followed by 0.5, 1, and 2 months of withdrawal, the number of dendritic spines was reduced by 24, 19, and 7.5% in the posterior hippocampus, respectively. In the anterior part of the hippocampus, a significant loss of dendritic spines (-20.5%) was observed only after 9.5 months of ethanol consumption. After 1 month of withdrawal, both number and morphology of dendritic spines appeared normal in the anterior hippocampus. These results demonstrate that chronic alcohol consumption leads to morphological alterations and loss of dendritic spines in the hippocampus. However, both dendritic spine number and morphology progressively return to normal values after 2 months of withdrawal. This phenomenon is another example of neuronal plasticity in adult animal brain.

First visualization of dopaminergic neurons with a monoclonal antibody to dopamine: a light and electron microscopic study

A monoclonal antibody recently synthesized against dopamine (DA) was tested in rat and mouse brain sections after further treatment by PAP immunocytochemistry at the light and electron microscopic levels. Distribution of DA-immunoreactive cell bodies was examined in the substantia nigra (sn), the ventral tegmental area (vta), and the raphe nuclei. DA-immunoreactive fibers were investigated in two DA projection systems, the striatum and the septum. Many dopaminergic cell bodies were found in the sn and the vta. Some scattered DA neurons were encountered in the pars reticulata of the sn. The dorsal raphe and linearis raphe nuclei displayed sparse immunoreactive neurons and a dense plexus of DA fibers. Immunoreactive fibers were observed in the entire striatum, more dense in the ventral part. In the septum, immunonegative neurons were outlined by thin DA fibers in synaptic contact with their somata or dendrites. According to our observations, this DA monoclonal antibody seems to be a selective and sensitive tool for studying the dopaminergic neuronal circuitry at both histological and ultrastructural level.

Build-up and release from proactive interference during chronic ethanol consumption in mice: a behavioral and neuroanatomical study

Male mice of the BALB/c strain were given a solution of 15% ethanol as their only source of fluid during either 24 or 48 weeks. They were submitted to a sequential alternation (SA) task in a T-maze (6 successive trials). It was found that 48 but not 24 weeks of alcohol administration lead to a deficit as compared to pair-fed or tap-water controls. Whereas experimental mice performed as well as controls on the first 3 choices, they exhibited a gradual decrease in the SA rate on subsequent trials. We suggest that this deficit might result from an exaggerated vulnerability to proactive interference (PI). In order to further test this hypothesis, a second experiment investigated whether a between-trials variation of context of the maze would increase performance. It was found that the SA rate improved as soon as the variation was provided (5th trial). We suggest that the deficit of experimental mice results from an impairment of retrieval processes. A neuroanatomical study was conducted to quantify cell losses resulting from 8, 24 or 48 weeks of ethanol treatment in the mammillary bodies (MM) or the hippocampus (HPC). At the time of appearance of the deficit, MM exhibited a -32% cellular loss, whereas this was only -18% in the HPC. This result emphasises the importance of MM lesion in memory deficits resulting from long-term alcohol consumption.

Neuroanatomical effects of chronic ethanol consumption on dorsomedial and anterior thalamic nuclei and on substantia innominata in mice

Quantitative analysis, using histological sections, showed that chronic ethanol consumption for 7 months produced a weak but significant cellular loss in the dorsomedial thalamic nucleus, anterior thalamus and substantia innominata in the mouse. These results are in agreement with patterns of neuroanatomical damage observed in human alcoholics.

Effects of long-term ethanol consumption on GABAergic neurons in the mouse hippocampus: a quantitative immunocytochemical study

The effects of 6 months' ethanol consumption by mice on hippocampal GABAergic neurons were investigated by means of an immunocytochemical method using GABA antibodies. Although ethanol treatment did not modify body or brain weights in our experimental conditions, two differences were observed in ethanol-treated mice, as compared to controls: a decrease in the labelling intensity of immunopositive neurons and fibers in the dorsal and the ventral parts of the hippocampus; and a decrease in the number of immunopositive neurons. This neuronal loss was statistically significant in the ventral hippocampus only, where it reached about 25% in the stratum radiatum. It is concluded that chronic ethanol consumption leads to a decrease in GABA content of hippocampal neurons and to a loss of GABAergic neurons, mostly in the ventral part of the hippocampus. These alterations in GABAergic transmission could be related to the well known functional deficits observed in chronic alcoholism.

Effects of chronic ethanol consumption on pyramidal neurons of the mouse dorsal and ventral hippocampus: a quantitative histological analysis

The effects of a 9-month period of ethanol consumption (followed by 3 or 6 months of withdrawal) on the hippocampus of mice were investigated. Compared with control animals, a loss of hippocampal neurons was observed on histological sections from ethanol-treated mice. This loss was greater in the ventral hippocampus (-18.6% to -18.7%) than in the dorsal hippocampus (-5.2% to -8.5%). However, the nucleus diameter, as well as the number of dendritic spines (studied using the Golgi-rapid impregnation) of the remaining neurons was not significantly affected by chronic ethanol consumption in our experimental conditions.

Chronic ethanol consumption induces neuronal loss in mammillary bodies of the mouse: a quantitative analysis

Quantitative analysis, using histological sections, showed that chronic ethanol consumption in the mouse produced neuronal loss in the medial mammillary bodies. This cellular loss was not uniform and was more marked in posterior (-30.1%) than in anterior (-8.8%) parts. Moreover, a reduction of the nucleus diameter of the remaining neurons was found. These results are in agreement with patterns of neuroanatomical damage observed in human alcoholics.