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Extraction of mouse spinal motor neurons from transgenic mouse embryos recapitulating some aspects of neurodegenerative diseases like amyotrophic lateral sclerosis has met with limited success. Furthermore, extraction and long-term culture of adult mouse spinal motor neurons and glia remain also challenging. We present here a protocol designed to extract and purify high yields of motor neurons and glia from individual spinal cords collected on embryos and adult (5-month-old) normal or transgenic mice. This method is based on mild digestion of tissue followed by gradient density separation allowing to obtain two millions motor neurons over 92% pure from one E14.5 single embryo and more than 30,000 from an adult mouse. These cells can be cultured more than 14 days in vitro at a density of 100,000 cells/cm(2) to maintain optimal viability. Functional astrocytes and microglia and small gamma motor neurons can be purified at the same time. This protocol will be a powerful and reliable method to obtain motor neurons and glia to better understand mechanisms underlying spinal cord diseases.

Primary motor neurons are difficult to study in conventional culture systems because of their short-term survival without trophic support from glia. In addition, axonal migration on a two-dimensional Petri dish does not reflect the three-dimensional (3D) environment in vivo. A unique in vitro 3D model of motor nerve regeneration was developed to study motor neuron axonal migration and myelination. Mouse spinal cord motor neurons were seeded on a collagen sponge populated with Schwann cells and fibroblasts. This fibroblast-populated sponge was intended to mimic the connective tissue through which motor axons have to elongate in vivo. Addition of conventional neurotrophic supplements was not required for motor neuron survival but was necessary to promote deep neurite outgrowth, as assessed by immunostaining of neurofilament M. A vigorous neurite elongation was detected inside the sponge after only 14 days of neuron culture, reaching more than 850 microm. The model also allowed the maturation of motor fibers as one-third of them were positive for neurofilament H. Neurites growing in the sponge were subject to myelination when Schwann cells were present, as shown by myelin basic protein immunostaining and electron microscopy. We demonstrated in this model the spontaneous formation of numerous thick myelin sheaths surrounding motor fibers after long-term culture (28 days). Thus, this model might be a valuable tool to study the effect of various cells and/or attractive or repulsive molecules on motor neurite outgrowth in vitro and also for the study of myelination and pathogenesis of motor neuron diseases.

Neuron-glial interactions are important in development of the nervous system and pathogenesis of disease. Primary cell cultures prepared from nervous tissue are often used to study the properties of individual cell types and how they interact with each other. Isolation of pure populations of cells and their culture is challenging, particularly from murine spinal cord. The purpose of this study was to optimize various protocols to achieve efficient, parallel isolation and purification of primary motor neurons, microglia and astrocytes from the same mouse embryonic spinal cord sample. Following dissociation of E12 embryonic spinal cords, motor neurons were isolated at 97% purity by a single step centrifugation of the cell suspension through multiple discontinuous density gradients of NycoPrep. The residual mixed cell pellet was resuspended and cultured for 2 weeks. Mixed cultures were then shaken to release microglia, which were then harvested from the medium and subjected to another round of differential adhesion to achieve 99% purity. The astrocytes remaining in the mixed cultures were culled to 98% purity by treatment with leucine methyl ester and a subsequent vigorous shaking step to remove any remaining microglia and neurons. Furthermore, no cross contamination was observed in the glial cultures. This technique provides a simple, convenient, and reliable method of obtaining highly purified preparations of motor neurons, microglia and astrocytes from embryonic spinal cord for the study of spinal cord cell biology and motor neuron diseases.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset neurodegenerative disease mainly characterized by spasticity in the lower limbs and poor muscle control. The disease is caused by mutations in the SACS gene leading in most cases to a loss of function of the sacsin protein, which is highly expressed in motor neurons and Purkinje cells. To investigate the impact of the mutated sacsin protein in these cells in vitro, induced pluripotent stem cell- (iPSC-) derived motor neurons and iPSC-derived Purkinje cells were generated from three ARSACS patients. Both types of iPSC-derived neurons expressed the characteristic neuronal markers β3-tubulin, neurofilaments M and H, as well as specific markers like Islet-1 for motor neurons, and parvalbumin or calbindin for Purkinje cells. Compared to controls, iPSC-derived mutated SACS neurons expressed lower amounts of sacsin. In addition, characteristic neurofilament aggregates were detected along the neurites of both iPSC-derived neurons. These results indicate that it is possible to recapitulate in vitro, at least in part, the ARSACS pathological signature in vitro using patient-derived motor neurons and Purkinje cells differentiated from iPSCs. Such an in vitro personalized model of the disease could be useful for the screening of new drugs for the treatment of ARSACS. [ABSTRACT FROM AUTHOR]

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disease affecting upper and lower motor neurons (MNs). To investigate whether Schwann cells could be involved in the disease pathogenesis, we developed a tissue‐engineered three‐dimensional (3D) in vitro model that combined MNs cocultured with astrocytes and microglia seeded on top of a collagen sponge populated with epineurium fibroblasts to enable 3D axonal migration. C2C12 myoblasts were seeded underneath the sponge in the presence or absence of Schwann cells. To reproduce an ALS cellular microenvironment, MNs, astrocytes, and microglia were extracted from SOD1G93A mice recapitulating many aspects of the human disease. This 3D ALS in vitro model was compared with a 3D control made of cells isolated from SOD1WT mice. We showed that normal Schwann cells strongly enhanced MN axonal migration in the 3D control model but had no effect in the ALS model. However, ALS‐derived Schwann cells isolated from SOD1G93A mice failed to significantly improve axonal migration in both models. These results suggest that a cell therapy using healthy Schwann cells may not be effective in promoting axonal regeneration in ALS. In addition, this 3D ALS model could be used to study the impact of other cell types on ALS by various combinations of normal and diseased cells. [ABSTRACT FROM AUTHOR]