An alternative method for obtaining high-viability cell suspensions from neonatal mouse brain

New tissue dissociation protocol for scaled-up production of neural stem cells in suspension bioreactors

The successful dissociation of mammalian neural stem cell (NSC) aggregates (neurospheres) into a single-cell suspension is an important procedure when expanding NSCs for clinical use, or when performing important assays such as clonal analyses. Until now, researchers have had to rely primarily on destructive mechanical methods such as trituration with a pipette tip to break apart the aggregates. In this study we report on a new chemical dissociation procedure that is efficient, cost effective, reproducible, and much less harmful to murine NSCs than both mechanical and enzymatic techniques. This method, involving the manipulation of environmental pH levels, resulted in 40% higher measured cell densities and 15-20% higher viabilities compared with mechanical dissociation. Moreover, chemical dissociation resulted in the production of significantly less cellular debris. Chemical dissociation was found to have no adverse effects on the long-term proliferation of the NSCs, which retained the ability to proliferate, form neurospheres, self-renew, and exhibit multipotentiality. This chemical method represents a new approach for the dissociation of tissues.

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

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

Neuron-enriched second trimester human cultures: growth factor response and in vivo graft survival

Grafts of first trimester fetal tissue show limited survival and integration in the adult CNS. Alternative grafting strategies have been sought for treatment of neurodegenerative disease. We have developed cultures of human second trimester fetal tissues to study neuronal differentiation. Grafted into the SCID mouse striatum, aggregates of these cultures formed neuron-rich xenografts for at least 8 months. We examined the influence of various neurotrophic factors, including basic fibroblast growth factor (bFGF), brain-derived neurotrophic factor (BDNF), transforming growth factor-beta 1 (TGF-beta1), and hepatocyte growth factor (HGF), on the growth and differentiation of neuronal and glial cell populations. BDNF promoted the survival and differentiation of second trimester neurons whereas bFGF exhibited a strong proliferative effect on precursors and the astroglial population. Our data suggest that second trimester human fetal cultures contain neuroprogenitor cells that can be directed to the neuronal lineage. This process may be amplified by treatment with BDNF, which we hypothesize could improve the long-term in vivo survival of neuron-enriched grafts.

A serum-free, pyruvate-free medium that supports neonatal neural/glial cultures

Tissue culture media with serum generally cause excessive astrocyte proliferation in neonatal brain cultures, and often fail to support neonatal neurons. Published serum-free media for brain cultures contain sodium pyruvate, which interferes with lactate dehydrogenase (LDH) assays for cell death. We wanted to use neonatal neural-glial cultures in LDH assays while avoiding astrocyte proliferation, so we developed a serum-free medium without sodium pyruvate. Our initial medium was based on that of Romijn et al. (J Neurosci Methods 23:75-83, 1988), testing selected additives. Cell survival in 8-10-day-old cultures was measured using 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). N-acetylcysteine, citrate, superoxide dismutase, ascorbate, supplemental amino acids, and high levels of transferrin improved survival. The optimized medium supported neonatal brain cells in reaggregates or in monolayers of 400 cells/mm2 for several weeks with large, healthy-appearing neurons and very little astrocyte proliferation. Neurons stained strongly for the neuronal marker class III beta-tubulin and the synapse marker synaptophysin. Electron microscopy of reaggregate cultures demonstrated abundant neurons with synapses in a dense neuropil. This medium will be useful for various in vitro applications, especially those using LDH assays or requiring the use of neonatal cells.