Haematopoietic progenitor cells from adult bone marrow differentiate into cells that express oligodendroglial antigens in the neonatal mouse brain

Effects of exercise in combination with autologous bone marrow stem cell transplantation for patients with type 1 diabetes

Stem cell therapy is a promising approach for the treatment of type 1 diabetes mellitus (T1D). Previous studies recommended regular exercise for the control of T1D. Experimental studies showed that a combination of stem cells and exercise yielded a better outcome. Yet, the effect of exercise programs following stem cell transplantation in patients with T1D has not been investigated. Thus, the current study aimed to examine the effect of a combined exercise program on measures of glycemic control in patients with T1D who received autologous bone marrow stem cell transplantation (ABMSCT). Thirty patients with controlled T1D were assigned into two equal groups. Both groups underwent ABMSCT and received insulin therapy and a diabetic diet regime. Only the exercise group followed the combined exercise program. Outcome measures of glycemic control (i.e. fasting blood glucose level [FBG], post-prandial blood glucose level [PPG], HbA1c, daily insulin dosage, and C-peptide levels) were tested before and after a 3-month rehabilitation period. There were significant (p < 0.05) decreases in all outcome measures except C-peptides after ABMSCT compared with before in both groups. Moreover, there was a significant decrease in the mean value of HbA1c in the exercise group compared with the control group after rehabilitation. Overall, this study strengthens the idea that adding exercise to ABMSCT is important to help control diabetes in patients with T1D.

Improvement of Combined FISH and Immunofluorescence to Trace the Fate of Somatic Stem Cells after Transplantation

Fluorescence in situ hybridization (FISH) combined with immunohistochemistry of tissue-specific markers provides a reliable method for characterizing the fate of somatic stem cells in transplantation experiments. Furthermore, the association between FISH and fluorescent gene reporter detection can unravel cell fusion phenomena, which could account for apparent transdifferentiation events. However, despite the widespread use of these techniques, they still require labor-extensive protocol adjustments to achieve correct and satisfactory simultaneous signal detection. In the present paper, we describe an improvement of simultaneous FISH and immunofluorescence detection. We applied this protocol to the identification of transplanted human and mouse hematopoietic stem cells in murine brain and muscle. This technique provides unique opportunities for following the path taken by transplanted cells and their differentiation into mature cell types.

Adult neural stem cells: Long-term self-renewal, replenishment by the immune system, or both?

The current model of adult neurogenesis in mammals suggests that adult-born neurons are generated by stem cells that undergo long-term self-renewal, and that a lifetime supply of stem cells resides in the brain. In contrast, it has recently been demonstrated that adult-born neurons in crayfish are generated by precursors originating in the immune system. This is particularly interesting because studies done many years ago suggest that a similar mechanism might exist in rodents and humans, with bone marrow providing stem cells that can generate neurons. However, the relevance of these findings for natural mechanisms underlying adult neurogenesis in mammals is not clear, because of uncertainties at many levels. We argue here that the recent findings in crayfish send a strong signal to re-examine existing data from rodents and humans, and to design new experiments that will directly test the contributions of the immune system to adult neurogenesis in mammals.

Oligodendrocytes engineered with migratory proteins as effective graft source for cell transplantation in multiple sclerosis

Multiple sclerosis (MS) is characterized by widespread immunomodulatory demyelination of the CNS resulting in nerve cell dysfunction. Accordingly, treatment strategies have been centered on immunodulation and remyelination, with the former primarily focused on reducing the pathology rather than enhancing myelin repair which the latter targets. While conceding to the emerging view of heterogeneity in the pathology of MS, which precludes variations in degree of immune response (i.e., inflammation) and demyelination, the concept of enhancing myelin repair is appealing since it is likely to provide both disease-reducing and disease-inhibiting therapeutic approach to MS. In this regard, we and several others, have proposed that cell replacement therapy is an effective strategy to repair the myelin in MS. Here, we hypothesize that transplantation of mouse bone marrow-derived oligodendrocytes (BMDOs) and BMDOs transfected with Ephrin proteins (BMDO+Ephrin), which are known to enhance cell and axonal migratory capacity, may produce therapeutic benefits in animal models of MS.

Acute and chronic MRI changes in the spine and spinal cord after surgical stem cell grafting in patients with definite amyotrophic lateral sclerosis: post-infusion injuries are unrelated with clinical impairment

OBJECTIVE

To report MRI spinal changes after surgical infusion of bone marrow stem cells (BMSc) in ALS patients and assess their correlation with clinical events and functional performance.

METHODS

BMSc were surgically injected in the thoracic spinal cord of 11 ALS patients (6/5 male/female; median age 46years). We performed first-week and third, sixth, ninth and twelfth post-surgical months spinal MRIs. The spinal changes in the postsurgical week and follow-up MRIs, as well as clinical events, functional scales and respiratory and electromyography data, were longitudinally monitored. Correlations between the imaging and clinical data were evaluated with the Spearman's test.

RESULTS

Transient extradural fluid collections (100%), transient spinal cord T2 hyperintensity (81.8%), and chronic spinal cord deformities (63.6%) were the dominating MRI changes. Spinal cord hemorrhages (27.3%) and cystic myelomalacia (1/11 patients) were important although unusual findings. During the follow-up, minor adverse events of mild to moderate intensity eventually improved. Initial and follow-up imaging scores showed a strongly positive correlation (r 0.879, P<0.001). The initial and delayed clinical scores did not correlate. There was no significant correlation between any of the imaging scores and clinical data.

CONCLUSIONS

Infusion of BMSc produces a variety of spinal changes apparently unrelated with clinical events and disease worsening.

Prevention of seizures and reorganization of hippocampal functions by transplantation of bone marrow cells in the acute phase of experimental epilepsy

In this study, we investigated the therapeutic potential of bone marrow mononuclear cells (BMCs) in a model of epilepsy induced by pilocarpine in rats. BMCs obtained from green fluorescent protein (GFP) transgenic mice or rats were transplanted intravenously after induction of status epilepticus (SE). Spontaneous recurrent seizures (SRS) were monitored using Racine's seizure severity scale. All of the rats in the saline-treated epileptic control group developed SRS, whereas none of the BMC-treated epileptic animals had seizures in the short term (15 days after transplantation), regardless of the BMC source. Over the long-term chronic phase (120 days after transplantation), only 25% of BMC-treated epileptic animals had seizures, but with a lower frequency and duration compared to the epileptic control group. The density of hippocampal neurons in the brains of animals treated with BMCs was markedly preserved. At hippocampal Schaeffer collateral-CA1 synapses, long-term potentiation was preserved in BMC-transplanted rats compared to epileptic controls. The donor-derived GFP(+) cells were rarely found in the brains of transplanted epileptic rats. In conclusion, treatment with BMCs can prevent the development of chronic seizures, reduce neuronal loss, and influence the reorganization of the hippocampal neuronal network.

Adult stem cell therapies for neurological disorders: benefits beyond neuronal replacement?

The modest capacity of endogenous repair processes in the central nervous system (CNS) justifies the broad interest in the development of effective stem cell based therapies for neurodegenerative disorders and other acute or chronic lesions. Motivated by the ambitious expectation to achieve functional neuronal replacement, several studies have already evidenced a potential benefit of stem cell grafts in animal models of human disorders. Nevertheless, growing evidence suggests that the effects orchestrated by stem cells, in most experimental cases, are not necessarily associated with the generation of new neurons. This hypothesis correlates with the versatile properties of adult and embryonic stem cells. When introduced into the lesioned CNS, nondifferentiated stem cells can have a positive influence through intrinsic neuroprotective capacities related to the production of neurotrophic factors, stimulation of endogenous neurogenesis, and modulation of neuroinflammation. Stem cells are also endowed with a multipotent differentiation profile, suggesting that a positive outcome could result from the replacement of nonneuronal cell types, in particular astrocytes and oligodendrocytes. Focusing on adult stem cells, this Review aims at summarizing experimental observations supporting the concept that, in cell-based therapies, stem cells operate not through a unidirectional mechanism (e.g., generating neurons) but rather as cellular mediators of a multitude of biological activities that could provide a favorable outcome for diverse nervous disorders.

Autologous bone marrow stem cells--properties and advantages

The properties of self-renewal and multi-lineage differentiation make stem cells attractive candidates for use in cellular reparative therapy, particularly in neurological diseases where there is a paucity of treatment options. However, clinical trials using foetal material in Parkinson's disease have been disappointing and highlighted problems associated with the use of embryonic stem cells, including ethical issues and practical concerns regarding teratoma formation. Understandably, this has led investigators to explore alternative sources of stem cells for transplantation. The expression of neuroectodermal markers by cells of bone marrow origin focused attention on these adult stem cells. Although early enthusiasm has been tempered by dispute regarding the validity of reports of in vitro (trans)differentiation, the demonstration of functional benefit in animal models of neurological disease is encouraging. Here we will review some of the required properties of stem cells for use in transplantation therapy with specific reference to the development of bone marrow-derived cells as a source of cells for repair in demyelination.

Neuroprotective effect of adult hematopoietic stem cells in a mouse model of motoneuron degeneration

Degenerative spinal motor diseases, like amyotrophic lateral sclerosis, are produced by progressive degeneration of motoneurons. Their clinical manifestations include a progressive muscular weakness and atrophy, which lead to paralysis and premature death. Current pharmacological therapies fail to stop the progression of motor deficits or to restore motor function. The purpose of our study was to explore the possible beneficial effect of mouse adult hematopoietic stem cells (hSCs) transplanted into the spinal cord of a mouse model of motoneuron degeneration. Our results show that grafted hSCs survive in the spinal cord. In addition, the number of motoneurons in the transplanted spinal cord is larger than in non-transplanted mdf mice at the same spinal cord segments and importantly, motor function significantly improves. These effects can be explained by the increased levels of glial cell line derived neurotrophic factor (GDNF) around host motoneurons produced by the grafted cells. Thus, these experiments demonstrate the neuroprotective effect of adult hSCs in the model employed and indicate that this cell type may contribute to ameliorating motor function in degenerative spinal motor diseases.

Bone marrow-derived stem cells in neurological diseases: stones or masons?

In spite of the commonly held belief that ‘the brain does not regenerate’, it is now accepted that postnatal neurogenesis does occur. Thus, one wonders whether cellular-replacement therapy might be used to heal the brain in diseases caused by neuronal cell loss. The existence of neural stem cells has been demonstrated by many scientists and is now generally accepted. The exact role of these cells, how their numbers are regulated and how they participate in CNS and spinal cord regeneration in postnatal life are still not well known. There are many reviews summarizing work on these cells; consequently, I will focus instead on other cells that may participate in postnatal neurogenesis: bone marrow-derived stem cells. The possibility that bone marrow-derived stem cells populate the CNS and differentiate into various neural elements is certainly not universally accepted.

Neural transplantation of human MSC and NT2 cells in the twitcher mouse model

BACKGROUND

Accumulating evidence has demonstrated that the NT2 embryonal carcinoma cell line and multipotential stem cells found in BM, mesenchymal stromal cells (MSC), have the ability to differentiate into a wide variety of cell types. This study was designed to explore the efficacy of these two human stem cell types as a graft source for the treatment of demyelinating disorders such as Krabbe's disease and multiple sclerosis (MS).

METHODS

We examined the engraftment and in vivo differentiation of adult MSC and NT2 cells after transplantation into two demyelinating environments, the neonatal and postnatal twitcher mouse brain.

RESULTS

Both types of xenografts led to anatomical integration, without tumor formation, and remained viable in the normal and twitcher mouse brain, showing differentiation into neurons, astrocytes and oligodendrocytes.

DISCUSSION

This study represents a platform for further stem cell transplantation studies in the twitcher model and potentially has important therapeutic implications.

Adult stem cell therapy: Dream or reality?

Adult stem cells may be an invaluable source of plastic cells for tissue regeneration. The bone marrow contains different subpopulations of adult stem cells easily accessible for transplantation. However the therapeutic value of adult stem cell is a question of debate in the scientific community. We have investigated the potential benefits of adult hematopoietic stem cell transplantation in animal models of demyelinating and motor neuron diseases. Our results suggest that transplantation of HSC have direct and indirect neuroregenerative and neuroprotective effects.

Differential effects of Th1, monocyte/macrophage and Th2 cytokine mixtures on early gene expression for immune-related molecules by central nervous system mixed glial cell cultures

Cytokines secreted within the central nervous system (CNS) are important in the development of multiple sclerosis (MS) lesions. The balance between Th1, monocyte/macrophage (M/M) and Th2 cytokines in the CNS may be pivotal in determining the outcome of lesion development. We examined the effects of mixtures of cytokines on gene expression by CNS glial cells, as mixtures of cytokines are present in MS lesions, which in turn contain mixtures of glial cells. In this initial analysis by gene array, we examined changes at 6 hours to identify early changes in gene expression that represent primary responses to the cytokines. Rat glial cells were incubated with mixtures of Th1, M/M and Th2 cytokines for 6 hours and examined for changes in early gene expression employing microarray gene chip technology. A minimum of 814 genes were differentially regulated by one or more of the cytokine mixtures in comparison to controls, including changes in expression in a large number of genes for immune system-related proteins. Expression of the proteins for these genes likely influences development and inhibition of MS lesions as well as protective and regenerative processes. Analysing gene expression for the effects of various combinations of exogenous cytokines on glial cells in the absence of the confounding effects of inflammatory cells themselves should increase our understanding of cytokine-induced pathways in the CNS.

Neurogenic potential of progenitors derived from human circulating CD14+ monocytes

We previously reported a primitive cell fraction derived from human circulating CD14+ monocytes, named monocyte-derived multipotential cells (MOMC), that can differentiate along mesenchymal lineages, including bone, cartilage, fat, skeletal muscle and cardiac muscle. In this study, we investigated whether MOMC can differentiate into the neuronal lineage. MOMC were fluorescently labelled and cocultivated with a primary culture of rat neurons for up to 4 weeks. The protein and gene expressions of neuron-specific markers in the human MOMC were evaluated over time using immunohistochemistry, in situ hybridization and reverse transcription followed by PCR. Shortly after cocultivation with rat neurons, nearly all the MOMC expressed early neuroectodermal markers, Mash1, Neurogenin2 and NeuroD, together with nestin, an intermediate filament expressed in neurogenesis. After 14 days of coculture, a subpopulation of MOMC displayed a multipolar morphology with elongated neurites and expressed mature neuron-specific markers, including neurofilament, microtubule-associated protein type 2, beta3-tubulin, NeuN and Hu. Transdifferentiation of monocytes into the neuroectodermal lineage was shown by the simultaneous expression of proneural markers and CD45/CD14 early in the differentiation process. The cocultivated MOMC retained their proliferative capacity for at least 16 days. Finally, the neuronal differentiation of MOMC was observed when they were cultured with neurons without cell-to-cell contact. The capacity of MOMC to differentiate into both mesodermal and neuroectodermal lineages suggests that circulating CD14+ monocytes are more multipotential than previously thought.

CD117 expression in glial tumors

C-kit is a proto-oncogene involved in normal growth and development and neoplastic processes, and its product, CD117, is a highly specific immunohistochemical diagnostic marker for gastrointestinal stromal tumors (GISTs). Because GISTs that express immunohistochemically-detectable CD117 respond dramatically to treatment with tyrosine kinase inhibitors, identification of central nervous system tumors that express CD117 might open new therapeutic approaches for treatment of brain tumors. Specimens from 52 glial tumors of various histologic types and grades were assayed for CD117 immunoreactivity, and about 75% of the tumors were positive for CD117 expression; all except a few exhibited strong cytoplasmic and membranous staining. The proportion of high grade tumors of all tumor types with detectable CD117 immunoreactivity was statistically significantly greater than low grade tumors, and glioblastoma and anaplastic oligodendroglioma showed the highest staining grade. These findings support further investigation into the possibility that CD117 has an important role in growth of glial tumors and that patients with brain tumors expressing CD117 might benefit from treatment with receptor tyrosine kinase inhibitors.

Phenotypic and functional characteristics of mesenchymal stem cells differentiated along a Schwann cell lineage

We have investigated the phenotypic and bioassay characteristics of bone marrow mesenchymal stromal cells (MSCs) differentiated along a Schwann cell lineage using glial growth factor. Expression of the Schwann cell markers S100, P75, and GFAP was determined by immunocytochemical staining and Western blotting. The levels of the stem cell markers Stro-1 and alkaline phosphatase and the neural progenitor marker nestin were also examined throughout the differentiation process. The phenotypic properties of cells differentiated at different passages were also compared. In addition to a phenotypic characterization, the functional ability of differentiated MSCs has been investigated employing a co-culture bioassay with dissociated primary sensory neurons. Following differentiation, MSCs underwent morphological changes similar to those of cultured Schwann cells and stained positively for all three Schwann cell markers. Quantitative Western blot analysis showed that the levels of S100 and P75 protein were significantly elevated upon differentiation. Differentiated MSCs were also found to enhance neurite outgrowth in co-culture with sensory neurons to a level equivalent or superior to that produced by Schwann cells. These findings support the assertion that MSCs can be differentiated into cells that are Schwann cell-like in terms of both phenotype and function.

The behavioral effect of human mesenchymal stem cell transplantation in cold brain injured rats

We investigated the effect of stereotaxically transplanted human mesenchymal stem cells (hMSCs) on behavioral change after traumatic cold brain injury in adult rats. Cortical lesions (n= 20) were induced by touching a metal stamp, cooled with liquid nitrogen, to the dura over the forelimb motor cortex of adult rats. The procedure produced a localized lesion, and the animals showed significant motor deficits. hMSCs were freshly isolated from human iliac bone and cultured in tissue culture flasks with 10 ml Dulbecco's modified Eagle's medium. The animals received hMSC grafts (3 x 10(5) hMSCs) 6 days after cold lesion (n = 10). All rats were sacrificed 3 or 7 weeks after cold injury, and immunohistochemical staining was performed on brain sections to identify donor hMSCs. Neurological evaluations were performed with the forepaw adjusting step test and modified neurological scoring. Treatment with 3 x 10(5) hMSCs improved the rat's neurological functions. We also found that the transplanted cells successfully migrated into the injured brain, preferentially localized around the injury site, and expressed the neuronal and astrocyte marker. These data suggest that hMSCs may be a potential therapeutic tool for brain injuries.

Medicina regenerativa con células madre adultas

The present state of clinical regenerative medicine with adult stem cells in the cardiology, digestive, corneal and neurological fields are reviewed. From the cardiology point of view, there is clinical experience with bone marrow stem cells and peripheral blood cells and with skeletal myoblasts. At present, the adult stem cells (bone marrow hematopoietic or mesenchymal) constitute the best option for the regeneration of heart tissue, the clinical studies showing favorable results without ethical or safety problems. Most of the studies with skeletal myoblasts have also been demonstrated to significantly contribute to improve heart function, above all, the systolic one. However they have the disadvantage that has not been totally clarified that they induce malignant ventricular arrhythmias. In either case, the clinical studies are in the initial phase and new studies, above all randomized, are necessary. In the digestive field, there is the pioneer experience of the Hospital La Paz on the use of stem cells from abdominal fat in the treatment of fistulous condition of patients with Crohn's disease. In ophthalmology, the limbal corneal transplant is a recognized practice, using cells from the contralateral eye when the damage is in a single eye and cells from a donor when the damage is bilateral. Finally, in the neurological field, different zones of the adult mammal brain where there are stem cells have been identified: the hippocampus, subventricular zone, olfactory bulb and periependymal zone of the spinal cord. On the other hand, neurons may be obtained from adult stem cells from other tissues, such as the bone marrow or adipose tissue, which means a practically unendable source of neural precursors, either by direct implant after their selection or after their in vitro culture. However, most of the experimentation is animal up to now, clinical trails on safety in amyotrophic lateral sclerosis are now being initiated.

Bone marrow transplantation combined with gene therapy to induce antigen-specific tolerance and ameliorate EAE

Hematopoietic stem cell (HSC) transplantation is a potential therapy that can offer multiple sclerosis patients a radical, potentially curative treatment. Using experimental autoimmune encephalomyelitis (EAE) as a model, we previously reported that retrovirally transduced B cells expressing myelin basic protein (MBP), MBP Ac1-11, or myelin oligodendrocyte glycoprotein p35-55 induced tolerance and reduced symptoms. Here, we extend our tolerance approach using bone marrow (BM) cells expressing full-length phospholipid protein (PLP) in a model for relapsing, remitting EAE. Using GFP expression as a marker, we found that up to 50% of cells were positive for transgene expression in peripheral blood after 900 rad irradiation and transduced BM transplantation, and expression was stable in hematopoietic lineages for over 10 weeks. Upon challenge, T cell proliferation in response to PLP p139-151 was reduced and EAE was completely abolished in a pretreatment protocol. In addition, protection from EAE could be achieved with PLP-transduced BM cells given on day 12 after immunization, a potential therapeutic protocol. Finally, the protective effect of PLP-expressing BM could also be observed using a nonmyeloablative protocol, albeit with lower efficacy. Our results suggest that HSC may be useful to achieve long-lasting tolerance to protect mice from EAE and possibly to promote CNS repair in ongoing EAE.

Induction of umbilical cord blood-derived beta2m-c-Met+ cells into hepatocyte-like cells by coculture with CFSC/HGF cells

Several studies have indicated that adult stem cells derived from bone marrow (BM) and cord blood (CB) can differentiate into hepatocyte-like cells. This ability is important for the treatment of hepatic diseases with BM or CB as a potential approach. However, methods are still being developed for the efficient induction of stem cell differentiation and expansion to get enough cells to be useful. In the present study, we enriched a subset of umbilical cord blood beta(2)m(-)c-Met(+) cells (UCBCCs) and investigated the combination effect of liver nonparenchymal cells (cirrhotic fat-storing cells [CFSCs]) and hepatocyte growth factor (HGF) on the induction of UCBCCs into hepatocyte-like cells. UCBCCs were cocultured with CFSC/HGF feeder layers either directly or separately using insert wells. Flow cytometric analysis showed that most UCBCCs were CD34(+/-)CD90(+/-)CD49f(+)CD29(+)Alb(+)AFP(+). After cocultured with transgenic feeder layers for 7 days, UCBCCs displayed some morphologic characteristics of hepatocytes. Reverse-transcription polymerase chain reaction (RT-PCR) and immunofluorescence cell staining proved that the induced UCBCCs expressed several hepatocyte specific genes including AFP, Alb, CYP1B1 and cytokeratins CK18 and CK19. Furthermore, the induced cells displayed liver specific functions of indocyanine green (ICG) uptake, ammonium metabolism and albumin secretion. Hence, our data have demonstrated that UCBCCs might represent a novel subpopulation of CB-derived stem/progenitor cells capable of successful differentiation into hepatocyte-like cells when incubated with CFSC/HGF cells. In conclusion, not only HGF but also CFSCs and/or the secreted extracellular matrix (ECM) have been shown to be able to serve as essential microenvironment for hepatocyte differentiation.

Involvement of CD45 in central nervous system myelination

Myelin is a multi-layered membranous lipid insulator surrounding axons that allows the rapid conduction of neuronal impulses. In the central nervous system (CNS), myelin is produced by oligodendrocytes. During development, morphologically immature oligodendrocyte precursor cells (OPCs) arise from neural stem cells before differentiating into myelinating oligodendrocytes shortly after birth. Fyn tyrosine kinase (Fyn) has been shown to play a central role during OPC differentiation, including inducing morphological changes in the cells and initiating the expression of myelin basic protein (MBP), a major structural protein required for the compaction of myelin sheaths. Recently, we have shown that signaling via the gamma chain of immunoglobulin Fc receptors (FcRgamma) induces the Fyn-MBP cascade and promotes the morphological differentiation of OPCs. The protein tyrosine phosphatases that are responsible for the positive regulation of Fyn tyrosine kinase activity during this cascade, however, remained unknown. Here we report that a protein tyrosine phosphatase, CD45, is involved in this process. Fyn co-immunoprecipitated with CD45 from differentiating wild-type OPCs in vitro, while CD45-deficient OPCs failed to differentiate. Additionally, dysmyelination was observed in CD45-deficient mice in vivo. Our findings suggest that CD45 is a key phosphatase involved in OPC differentiation and provide a preliminary explanation for the previously reported CD45 mutations observed in some multiple sclerosis (MS) patients.

Therapeutic potential of stem cells in perinatal medicine

Increasing evidence suggests that stem cells have tremendous potential to facilitate repair of damaged tissue and to exert protective influences that limit the extent of damage. Their inherent capacity to respond to signals generated by damaged tissue, migrate to these regions and either replace dead tissue or deliver protection by secretion of specific growth hormones and protective factors, suggests that they might have unrivalled therapeutic potential in perinatal medicine. A further potential of stem cells is their use in gene repair strategies for genetic disorders; an application which is exceedingly interesting from a perinatal perspective. Because of the relatively small size of infants and their capacity for future growth, stem cell therapy could be more successful in newborns than in older children or adults. In practical terms, the placenta, with its large reservoir of fetal blood, offers the ideal source of autologous stem cells. This affords the opportunity for stem cells to be collected and used, either directly ex vivo or after in vitro modulation, both for disorders in the neonatal period and for those arising later in life. The organs most affected from tissue damage in the neonatal period are the brain and the lung. So far, the most promising application of stem cells might be in the treatment of neurological injury. In this review we discuss recent research findings with adult stem cell therapy and their potential use in perinatal medicine. Furthermore, specific animal models suitable to explore the patho-physiological mechanisms of stem cell transplantation after neurological injury will be discussed. This review gives an overview of basic science findings and their possible role for clinical application with regards to the therapeutic potential of stem cells in perinatal medicine. Medline was searched for journal selection in peer-reviewed journals with high impact scores, which were relevant to this topic. All articles were in English and the search was not limited by publication year. However, the oldest publication was dated 1988 (reference 1).

Plasticity of bone marrow-derived stem cells

Stem cell plasticity refers to the ability of adult stem cells to acquire mature phenotypes that are different from their tissue of origin. Adult bone marrow cells (BMCs) include two populations of bone marrow stem cells (BMCs): hematopoietic stem cells (HSCs), which give rise to all mature lineages of blood, and mesenchymal stem cells (MSCs), which can differentiate into bone, cartilage, and fat. In this article, we review the literature that lends credibility to the theory that highly plastic BMCs have a role in maintenance and repair of nonhematopoietic tissue. We discuss the possible mechanisms by which this may occur. Also reviewed is the possibility that adult BMCs can change their gene expression profile after fusion with a mature cell, which has brought into question whether this stem cell plasticity is real.

Functional neural stem cells derived from adult bone marrow

Pluripotent hematopoietic cells from adult bone marrow may give rise not only to neurons, oligodendrocytes and astrocytes after transplantation into newborn brains, but also to neural stem cells (NSC). These NSC localize to both the ventricular epithelium and subventricular zone, persist in the transplanted brain, and may generate neurospheres 1 month after transplant, which after in vitro expansion differentiate into the different neural lineages. Furthermore, the bone marrow-derived NSC differentiate in vivo into functional oligodendrocytes and neurons following demyelinating lesions, thus, demonstrating the ability of adult bone marrow progenitors to generate self-renewing, functional neural stem cells, validating this approach as an alternative source of long-lasting neural stem cells with therapeutic implications in neurodegenerative diseases.

Neuronal differentiation of murine bone marrow Thy-1- and Sca-1-positive cells

Recent evidence suggests that cells from bone marrow can acquire neuroectodermal phenotypes in cell culture or after transplantation in animal models and in the human brain. However, isolation of the bone marrow cell subpopulation with neuronal differentiation potential remains a challenge. To isolate and expand neural progenitors from whole murine bone marrow, bone marrow was obtained from hind limb bone of C57BL6 mice and plated in culture with neuronal medium with basic fibroblast growth factor and epidermal growth factor. After 5-7 days in culture, cellular spheres similar to brain neurospheres appeared either floating or attached to culture dishes. These spheres were collected, dissociated, and expanded. The bone marrow-derived spheres were positive for nestin as assessed by immunocytochemistry and by reverse transcriptase polymerase chain reaction. Thy-1- and Sca-1-positive bone marrow cells selected by magnetic cell sorting resulted in a higher yield of nestin-positive spheres. After exposure to neuronal differentiative medium retinoic acid with and without Sonic hedgehog, cells positive for neuronal markers tubulin III (TuJ-1) and neurofilament (NF) were detected. The mRNA profile of these cells included the expression of TuJ-1, neuronal-specific enolase (NSE), and NF-light chain. To evaluate the in vivo behavior of these cells, spheres derived from bone marrow-derived cells of transgenic green fluorescent protein (GFP) mice were transplanted into newborn mouse brain. Two months later, the mouse neural cortex contained a minor proportion of GFP(+) cells co-expressing neuronal markers (TuJ-1, NF, MAP-2, NeuN). Although cell fusion phenomena with the host cells could not be ruled out, bone marrow-derived neurosphere transplantation could be a strategy for cellular mediated gene therapy.

High-dose immunosuppression and autologous hematopoietic stem cell rescue for severe multiple sclerosis

Multiple sclerosis is a relatively common and seriously disabling disease of autoimmune pathogenesis, for which there is currently no cure. Available therapies include immunomodulating agents and standard-dose immunosuppressants, which may be helpful but are not curative. Recently, studies in animal models have indicated that control of autoimmune disease can be obtained by high-dose immunosuppression followed by hematopoietic stem cell transplantation (rescue). Autologous transplants for severe and refractory multiple sclerosis were proposed in 1997 and have been performed ever since in selected patients and in the context of phase I/II trials. To date, more than 200 patients have been treated worldwide, and similar results were obtained in different centers: high-dose therapy suppresses inflammation in the brain to a degree superior to any other conventional therapy and seems to delay significantly clinical disease progression. There is, however, a procedure-related mortality risk of 1.5-5%, requiring careful patient selection before transplant. The treatment should be reserved for patients having high chance of response, i.e., young patients with low disability scores but rapidly progressing disease, having inflammatory rather than neurodegenerative changes in the central nervous system. The mechanism of action of transplantation is unclear. The initial concept of immune ablation by high-dose therapy and reconstitution of normal immunity from transplant-derived lymphocyte progenitors has given way to the concept of "resetting" the immune system and of bringing the disease to a lower level of activity. One could also speculate on a tissue repair effect, given the ability of human hematopoietic stem cells to migrate also into the central nervous system. The clinical effect of transplantation remains to be demonstrated in a randomized study. The Autoimmune Disease Working Party of the European Group for Blood and Marrow Transplantation has launched such a trial, comparing transplantation to the currently best available therapy, i.e., mitoxantrone, and in about 5 years we should know whether transplantation offers more than the benefit of a transient immunosuppressive effect.

Adult stem cells--reprogramming neurological repair?

Much excitement has surrounded recent breakthroughs in embryonic stem-cell research. Of lower profile, but no less exciting, are the advances in the field of adult stem-cell research, and their implications for cell therapy. Clinical experience from use of adult haemopoietic stem cells in haematology will facilitate and hasten transition from laboratory to clinic--indeed, clinical trials using adult human stem cells are already in progress in some disease states, including myocardial ischaemia. Here, with particular reference to neurology, we review processes that might underlie apparent changes in adult cell phenotype. We discuss implications these processes might have for the development of new therapeutic strategies using adult stem cells.

Multiple sclerosis

Autologous transplants for severe and refractory multiple sclerosis (MS) were proposed in 1997 and have been performed on about 200 selected patients worldwide. Phase I/II clinical studies have shown that high-dose immunosuppressive therapy suppresses inflammation in the CNS and may delay the progression of clinical disease. The procedure is associated with toxicity from the high-dose cytotoxic therapy and a risk of serious infections. There is a transplant-related mortality risk of 1-5%, requiring careful patient selection before transplantation. Treatment should be reserved for patients who have a significant chance of response, i.e. young patients with low disability scores but rapidly progressing disease who have inflammatory rather than neurodegenerative changes in the CNS. The long term effect of high-dose immunosuppression after transplantation on the frequency of relapse or progression of MS is unclear, but the initial concept of immune ablation by high-dose therapy and the reconstitution of normal immunity and tolerance from transplant-derived lymphocyte progenitors has given way to the concept of 'resetting' the immune system. The clinical effect of transplantation remains to be demonstrated in comparative studies.

Absence of hematopoiesis from transplanted olfactory bulb neural stem cells

Neural stem cells giving rise to neurons and glia cells have been isolated from the embryonic and adult central nervous system. The extent to which they are able to differentiate into cells of non-neural lineages, such as the hematopoietic lineage, is nonetheless unclear. We previously reported the isolation of stem cells from the mouse olfactory bulb neuroepithelium. In the present study, we analysed whether olfactory bulb stem cells (OBSC) can generate cells with hematopoietic features. Cells were prepared from the olfactory bulbs of transgenic mice expressing enhanced green fluorescent protein (EGFP). In culture, transgenic cells proliferated with the same kinetics as wild-type cells. Following mitogen removal, both cell types gave rise to similar numbers of neurons, astrocytes and oligodendrocytes, indicating that EGFP overexpression does not alter OBSC proliferation and differentiation patterns. When these cells were injected into the tail vein of irradiated mice, no hematopoietic cells derived from the OBSC could be recovered in their peripheral blood, spleen or bone marrow. By contrast, when OBSC were transplanted into the adult brain, EGFP-positive cells were found in the striatum and corpus callosum; differentiated cells expressed antigenic markers of neurons and astrocytes. These results suggest that embryonic olfactory bulb stem cells are not endowed with the potential to produce hematopoiesis.

Primordial hematopoietic stem cells generate microglia but not myelin-forming cells in a neural environment

Finding ways to enhance remyelination is a major challenge in treating demyelinating diseases. Recent studies have suggested that circulating bone marrow cells can home in brain and transdifferentiate into neural cells. To ask whether hematopoietic precursors can form myelinating cells, we investigated the neuropoietic potential of embryonic precursors sorted from the mouse aorta-gonads-mesonephros (AGM) region. This cell fraction is capable of long-term hematopoietic reconstitution and generates colonies containing multipotential precursors and lymphoid or erythro-myeloid progenies. When cultured in hematopoietic growth conditions, a fraction of CD45-positive AGM cells coexpress neural markers such as nestin, the polysialylated form of neural cell adhesion molecule, the betaIII tubulin isoform, and glial fibrillary acidic protein. However, when hematopoietic precursors containing green fluorescent protein were cocultured with embryonic striatal precursors into neurospheres, they maintained their hematopoietic phenotype without undergoing differentiation into neurons, astrocytes, or oligodendrocytes. After intraventricular grafting, hematopoietic precursors integrated into the brain of wild-type or hypomyelinated newborn shiverer mice and gave rise to microglia but not neurons or glia. In contrast, when wild-type embryonic striatal neurospheres were grafted in shiverer, they formed numerous myelin internode patches. Even when neural and hematopoietic precursors were grafted together into shiverer mice, only neural precursors generated myelin-forming cells and synthesized myelin. Thus, embryonic neurospheres have myelin repair properties not shown by embryonic hematopoietic precursors. This suggests that the use of multipotential neural precursors to generate myelin-forming cells remains one of the most promising avenues toward remyelination therapies.

Stem cells for the treatment of neurological disease

Stem cells are widely believed to have significant potential in the treatment of human disease. Comments such as '[stem cells]...could prove the Holy Grail in finding treatments for cancer, Parkinson's disease, diabetes, osteoporosis, spinal cord injuries, Alzheimer's disease, leukaemia and multiple sclerosis...transform[ing] the lives of hundreds of thousands of people' (Yvette Cooper, Public Health minister, quoted in The Times, December 16 2000, authors' italics) serve to reinforce the extraordinary expectations of stem cells, particularly in neurological disease. Stem cells, traditionally defined as clone forming, self-renewing, pluripotent, progenitor cells, have already proved themselves to be an invaluable source of transplantation material in several clinical settings, most notably malignant haematology, and attention is now turning to a wider variety of diseases in which there may be potential for therapeutic intervention with stem cell transplantation. Neurological diseases have been highlighted as a priority and this is understandable given their unenviable reputation for relentless progression and the paucity of disease-modifying treatments. However, it is important that the potential of stem cells to treat neurological disease is critically appraised if the hopes of patients and doctors are not to be raised without foundation.

Hematopoietic progenitors express neural genes

Bone marrow, or cells selected from bone marrow, were reported recently to give rise to cells with a neural phenotype after in vitro treatment with neural-inducing factors or after delivery into the brain. However, we showed previously that untreated bone marrow cells express products of the neural myelin basic protein gene, and we demonstrate here that a subset of ex vivo bone marrow cells expresses the neurogenic transcription factor Pax-6 as well as neuronal genes encoding neurofilament H, NeuN (neuronal nuclear protein), HuC/HuD (Hu-antigen C/Hu-antigen D), and GAD65 (glutamic acid decarboxylase 65), as well as the oligodendroglial gene encoding CNPase (2',3' cyclic nucleotide 3'-phosphohydrolase). In contrast, astroglial glial fibrillary acidic protein (GFAP) was not detected. These cells also were CD34+, a marker of hematopoietic stem cells. Cultures of these highly proliferative CD34+ cells, derived from adult mouse bone marrow, uniformly displayed a phenotype comparable with that of hematopoietic progenitor cells (CD45+, CD34+, Sca-1+, AA4.1+, cKit+, GATA-2+, and LMO-2+). The neuronal and oligodendroglial genes expressed in ex vivo bone marrow also were expressed in all cultured CD34+ cells, and GFAP was not observed. After CD34+ cell transplantation into adult brain, neuronal or oligodendroglial markers segregated into distinct nonoverlapping cell populations, whereas astroglial GFAP appeared, in the absence of other neural markers, in a separate set of implanted cells. Thus, neuronal and oligodendroglial gene products are present in a subset of bone marrow cells, and the expression of these genes can be regulated in brain. The fact that these CD34+ cells also express transcription factors (Rex-1 and Oct-4) that are found in early development elicits the hypothesis that they may be pluripotent embryonic-like stem cells.

Bone marrow-derived cells that populate the adult mouse brain preserve their hematopoietic identity

Cytogenesis in the adult brain can result from the recruitment of circulating precursors, but the proposal that some such cells transdifferentiate into neural elements is controversial. We have reinvestigated this issue by following the phenotypic fate of bone marrow cells expressing the green fluorescent protein transplanted into the systemic circulation of irradiated mice. Thousands of donor-derived cells were detected throughout brains of recipients killed 1-12 months after transplantation, but none displayed neuronal, macroglial, or endothelial characteristics, even after injury. Among those that crossed the endothelium of the cerebral cortex, >99.7% were identified as perivascular macrophages. Newly formed parenchymal microglia were found in significant numbers only in the cerebellum and at injury sites. Therefore, bone marrow does supply the mature brain with new specialized cells; however, mesenchymal precursors neither adopt neural phenotypes nor contribute to cerebral vascular remodeling. This continuous traffic of macrophages across the blood-brain barrier provides a vehicle to introduce therapeutic genes into the nervous system.

Molecular biology of hematopoietic stem cells

Human CD34+ hematopoietic stem and progenitor cells are capable of maintaining a life-long supply of the entire spectrum of blood cells dependent on systemic needs. Recent studies suggest that hematopoietic stem cells are, beyond their hematopoietic potential, able to differentiate into nonhematopoietic cell types, which could open novel avenues in the field of cellular therapy. Here, we concentrate on the molecular biology underlying basic features of hematopoietic stem cells. Immunofluorescence analyses, culture assays, and transplantation models permit an extensive immunological as well as functional characterization of human hematopoietic stem and progenitor cells. New methods such as cDNA array technology have demonstrated that distinct gene expression patterns of transcription factors and cell cycle genes molecularly control self-renewal, differentiation, and proliferation. Furthermore, several adhesion molecules have been shown to play an important role in the regulation of hematopoiesis and stem cell trafficking. Progress has also been made in elucidating molecular mechanisms of stem cell aging that limit replicative potential. Finally, more recent data provide the first molecular basis for a better understanding of transdifferentiation and developmental plasticity of hematopoietic stem cells. These findings could be helpful for non-hematopoietic cell therapeutic approaches.

Multiple paths towards repair in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS, affecting approximately 1/1000 individuals in the Western world. Available treatments limit CNS inflammation and strategies to repair damage in the CNS offer the potential of recovery of both tissue and function. With further fundamental knowledge developing, this area is ripe for 'translation' to clinical application.

Early oligodendrocyte progenitor cells in the human fetal telencephalon

Oligodendrocytes, the myelin-producing cells in the central nervous system, represent a large portion of the total number of cells in the human brain. Using cell-specific markers and antibodies to ventral homeodomain transcription factors, NKX2.1 and DLX2, we show here that a subpopulation of early oligodendrocyte progenitor cells (OPCs) in the human telencephalon may originate in the ganglionic eminence (GE). DLX2-labeled OPCs form a well-delineated stream of cells connecting the GE subventricular zone (SVZ) to the cortical intermediate zone through the anterior cortical SVZ. This population of cells is labeled by early OPCs markers, PDGFRalpha, Olig1, and NG2, and not with either neuronal, astrocyte, or late OPCs markers. Intriguingly, numerous CD68(+) microglia/macrophages, nestin(+) neural stem cells, and CD34(+) hematopoietic stem cells (HSCs) are also present in both the GE stream and the cortical SVZ. These cells could be colabeled with DLX2 as well as early OPCs markers. A separate subpopulation of early OPCs, present in the GE and cortical SVZ, did not express either DLX2 or CD68. These findings suggest that different subpopulations of early OPCs, characterized with different sets of transcription factors and cell-specific markers, are present in human forebrain. These subpopulations may have different origins; one may originate in the cortical SVZ, while others may come from the GE and/or outside the CNS as hematopoietic stem cells.

In utero transplantation of wild-type fetal liver cells rescues factor X-deficient mice from fatal neonatal bleeding diatheses

Factor X (FX)-deficient embryos suffer partial embryonic lethality with approximately 30% of the embryos arresting at midgestation. The remaining animals survive to term but die perinatally mainly from abdominal or intracranial hemorrhage. We have rescued FX-deficient mice by transplanting fetal liver cells from FX+/+, Rosa26 fetuses into midgestation embryos derived from FX+/- heterozygous crosses. FX-/- embryos were born at the expected frequency and approximately 50% of the FX-/- neonates survived longer than 4 months. FX-/- embryos receiving saline injections that survived to term died perinatally similar to untreated FX-deficient mice. The plasma levels of FX in the rescued 16-week-old FX-/- mice were approximately 1-6% of wild-type levels. beta-Galactosidase-staining cells derived from the donor Rosa26 fetal liver cells were detected in 47% of the livers of adult mice. In addition, donor-derived cells were also recovered in the bone marrow, spleen, lung, and occasionally in the brain and testis. These results suggest that in utero cell transplantation could be an effective therapeutic strategy to treat pathologies resulting from the deficiency of hepatic-expressed factors.