Stem cells have been increasingly recognized as a potential tool to replace or support cells damaged by the neurodegenerative process that underlies Parkinson's disease (PD). In this frame, human adult mesenchymal stem cells (hMSCs) have been proposed as an attractive alternative to heterologous embryonic or neural precursor cells. To address this issue, in this study we implanted undifferentiated hMSCs into the striatum of rats bearing a lesion of the nigrostriatal pathway induced by local injection of 6-hydroxydopamine (6-OHDA), a widely recognized rodent model of PD. Before grafting, cultured hMSCs expressed markers of both undifferentiated and committed neural cells, including nestin, GAP-43, NSE, β-tubulin III, and MAP-2, as well as several cytokine mRNAs. No glial or specific neuronal markers were detected. Following transplantation, some hMSCs acquired a glial-like phenotype, as shown by immunoreactivity for glial fibrillary acid protein (GFAP), but only in animals bearing the nigrostriatal lesion. More importantly, rats that received the striatal graft showed increased survival of both cell bodies and terminals of dopaminergic, nigrostriatal neurons, coupled with a reduction of the behavioral abnormalities (apomorphine-induced turning behavior) associated with the lesion. No differentiation of the MSCs toward a neuronal (dopaminergic) phenotype was observed in vivo. In conclusion, our results suggest that grafted hMSCs exert neuroprotective effects against nigrostriatal degeneration induced by 6-OHDA. The mechanisms underlying this effect remain to be clarified, although it is likely that the acquisition of a glial phenotype by grafted hMSCs may lead to the release of prosurvival cytokines within the lesioned striatum.
Abstract Background There are multiple promising treatment strategies for central nervous system trauma and disease. However, to develop clinically potent and safe treatments, models of human-specific conditions are needed to complement in vitro and in vivo animal model-based studies. Methods We established human brain stem and spinal cord (cross- and longitudinal sections) organotypic cultures (hOCs) from first trimester tissues after informed consent by donor and ethical approval by the Regional Human Ethics Committee, Stockholm (lately referred to as Swedish Ethical Review Authority), and The National Board of Health and Welfare, Sweden. We evaluated the stability of hOCs with a semi-quantitative hOC score, immunohistochemistry, flow cytometry, Ca 2+ signaling, and electrophysiological analysis. We also applied experimental allogeneic human neural cell therapy after injury in the ex vivo spinal cord slices. Results The spinal cord hOCs presented relatively stable features during 7–21 days in vitro (DIV) (except a slightly increased cell proliferation and activated glial response). After contusion injury performed at 7 DIV, a significant reduction of the hOC score, increase of the activated caspase-3 + cell population, and activated microglial populations at 14 days postinjury compared to sham controls were observed. Such elevation in the activated caspase-3 + population and activated microglial population was not observed after allogeneic human neural cell therapy. Conclusions We conclude that human spinal cord slice cultures have potential for future structural and functional studies of human spinal cord development, injury, and treatment strategies.
Post-transcriptional regulation exerted by neural-specific RNA-binding proteins plays a pivotal role in the development and maintenance of the nervous system. Neural ELAV proteins are key inducers of neuronal differentiation through the stabilization and/or translational enhancement of target transcripts bearing the AU-rich elements (AREs), whereas Musashi-1 maintains the stem cell proliferation state by acting as a translational repressor. Since the gene encoding Musashi-1 (Msi1) contains a conserved ARE in its 3′ untranslated region, we focused on the possibility of a mechanistic relationship between ELAV proteins and Musashi-1 in cell fate commitment. Colocalization of neural ELAV proteins with Musashi-1 clearly shows that ELAV proteins are expressed at early stages of neural commitment, whereas interaction studies demonstrate that neural ELAV proteins exert an ARE-dependent binding activity on the Msi1 mRNA. This binding activity has functional effects, since the ELAV protein family member HuD is able to stabilize the Msi1 ARE-containing mRNA in a sequence-dependent way in a deadenylation/degradation assay. Furthermore activation of the neural ELAV proteins by phorbol esters in human SH-SY5Y cells is associated with an increase of Musashi-1 protein content in the cytoskeleton. We propose that ELAV RNA-binding proteins exert an important post-transcriptional control on Musashi-1 expression in the transition from proliferation to neural differentiation of stem/progenitor cells.
Given the lack of effective drug treatments for amyotrophic lateral sclerosis (ALS), compelling preclinical data on stem cell research has targeted this disease as a candidate for stem cell treatment. Stem cell transplantation has been effective in several animal models, but the underlying biological pathways of restorative processes are still unresolved. Several mechanisms such as cell fusion, neurotrophic factor release, endogenous stem cell proliferation, and transdifferentiation may explain positive therapeutic results in preclinical animal models, in addition to replacement of lost motor neurons. The clinical target in ALS has shifted from being neuroncentered to focus on the interaction between motor neurons and non-neuronal cells (mainly astroglial or microglial). In fact, one of the fundamental unanswered questions in ALS is whether and how much motor neuron death depends on neighboring cells, and how wildtype non-neuronal cells may protect motor neurons expressing an ALS-causing mutation. Lately, motor neuron replacement has been successfully achieved in animal models with reinnervation of the muscle target. Even if many biological issues need to be solved in preclinical models, preliminary stem cell transplantation trials have been performed in ALS patients with conflicting results. The review discusses relevant topics regarding the application of stem cell research to ALS focusing on their therapeutic relevance and mechanisms of action. Keywords: Amyotrophic lateral sclerosis, motor neuron, stem cells, transplantation, protection, replacement
