Enhanced in vitro survival and growth of foetal human mesencephalic dopaminergic neurones on laminin and collagen: implications for cell banking

Structural and Functional Plasticity of Collagen Fibrils

Collagen is a major component of the subendothelial matrix and participates in bleeding arrest by activating and aggregating platelets at the site of vascular injury. The most common type I collagen exists in both soluble and fibrillar forms, but structural exchangeability between the two forms is currently unknown. Using atomic force microscopy, we show that type I collagen switches between soluble and fibrillar forms in a pH-dependent and ion-independent manner. Fibrillar collagen is rope like with characteristic "D-bands." The collagen fibrils can be disrupted with 0.1 M acetic acid and will reform when the pH is adjusted to 7.4. This structural plasticity leads to drastically different activities, with fibrillar collagen being significantly more active for platelets under static and flow conditions. More important, by probing with noncontact hopping probe ion-conductance microscopy, we find that platelets adherent to fibrillar collagen present primarily as high-density bubble shapes that have undergone rapid microvesiculation.

The influence of oxygen supply on metabolism of neural cells cultured on a gas-permeable PTFE foil

The influence of oxygen on neural stem cell proliferation, differentiation, and apoptosis is of great interest for regenerative therapies in neurodegenerative disorders, such as Parkinson's disease. These oxygen depending mechanisms have to been considered for the optimization of neural cell culture conditions. In this study, we used a cell culture system with an oxygen-permeable polytetrafluorethylene (PTFE) foil to investigate the effect of oxygen on metabolism and survival of neural cell lines in vitro. Human glial astrocytoma-derived cells (GOS-3) and rat pheochromacytoma cells (PC12) were cultured on the gas-permeable PTFE foil as well as a conventional non oxygen-permeable cell culture substrate at various oxygen concentrations. Analyses of metabolic activity, gene expression of apoptotic grade, and dopamine synthesis were performed. Under low oxygen partial pressure (2%, 5%) the anaerobic metabolism and apoptotic rate of cultured cells is diminished on PTFE foil when compared with the conventional culture dishes. In contrast, under higher oxygen atmosphere (21%) the number of apoptotic cells on the PTFE foil was enhanced. This culture model demonstrates a suitable model for the improvement of oxygen dependent metabolism under low oxygen conditions as well as for induction of oxidative stress by high oxygen atmosphere without supplementation of neurotoxins.

Environmental cues to guide stem cell fate decision for tissue engineering applications

The human body contains a variety of stem cells capable of both repeated self-renewal and production of specialised, differentiated progeny. Critical to the implementation of these cells in tissue engineering strategies is a thorough understanding of which external signals in the stem cell microenvironment provide cues to control their fate decision in terms of proliferation or differentiation into a desired, specific phenotype. These signals must then be incorporated into tissue regeneration approaches for regulated exposure to stem cells. The precise spatial and temporal presentation of factors directing stem cell behaviour is extremely important during embryogenesis, development and natural healing events, and it is possible that this level of control will be vital to the success of many regenerative therapies. This review covers existing tissue engineering approaches to guide the differentiation of three disparate stem cell populations: mesenchymal, neural and endothelial. These progenitor cells will be of central importance in many future connective, neural and vascular tissue regeneration technologies.

Production of dopaminergic neurons for cell therapy in the treatment of Parkinson's disease

Dopaminergic cell therapy is a potential viable treatment for Parkinson's disease. However, lack of a well-characterized cell preparation of known phenotypic composition containing a high percentage of dopaminergic neurons, has prevented a definitive, controlled, pilot clinical trial from being conducted. We report the successful in vitro expansion of rat E12 mesencephalic progenitors to produce 5-fold the normal number of dopaminergic neurons. The expanded neurons (MAP2+) were detached, resuspended, and formed into small aggregates of 10-200 neurons containing 25-50% of dopaminergic neurons (TH+) that will likely be optimal for use in successful cell therapy. After storage in DPBS, in 0 mM Ca(2+) for up to 24 h at room temperature, aggregated cells were still 90% viable. These results demonstrate that it might be feasible to use a similar protocol to expand human dopaminergic progenitors in vitro. If successful, the requisite large numbers of dopaminergic neurons required to conduct a pilot clinical trial for Parkinson's disease will be produced in vitro. Indications are that the cells can be maintained at optimal viability for the duration of the neural transplantation procedure, under real operating conditions.

Integrin signaling via the PI3-kinase-Akt pathway increases neuronal resistance to glutamate-induced apoptosis

Integrins are integral membrane proteins that mediate adhesive interactions of cells with the extracellular matrix and with other cells. Integrin engagement results in activation of intracellular signaling cascades that effect several different cellular responses including motility, proliferation and survival. Although integrins are known to provide cell survival signaling in various types of non-neuronal cells, the possibility that integrins modulate neuron survival has not been explored. We now report data demonstrating a neuroprotective function of integrins in embryonic hippocampal neurons. Neurons grown on laminin, an integrin ligand, exhibit increased resistance to glutamate-induced apoptosis compared with neurons grown on polylysine. Neurons expressed integrin beta1 and treatment of cultures with an antibody against integrin beta1 abolished the protective effect of laminin. Neurons maintained on laminin exhibited a sustained activation of the Akt signaling pathway demonstrated in immunoblot analyses using an antibody that selectively recognizes phosphorylated Akt. The neuroprotective effect of integrin engagement by laminin was mimicked by an IKLLI-containing integrin-binding peptide and was abolished by treatment of neurons with the PI3 kinase inhibitor wortmanin. Levels of the anti-apoptotic protein Bcl-2 were increased in neurons grown on laminin and decreased by wortmanin, suggesting a mechanism for the neuroprotective effect of integrin-mediated signaling. The ability of integrin-mediated signaling to prevent glutamate-induced apoptosis suggests a mechanism whereby neuron-substrate interactions can promote neuron survival under conditions of glutamate receptor overactivation.

Influence of extracellular matrix proteins on membrane potentials and excitability in NG108-15 cells

Previous studies have demonstrated that components of the extracellular matrix can induce neurite extension and cell adhesion in the neuroblastoma x glioma hybrid cell line, NG108-15. Using standard intracellular recording techniques, we examined the resting membrane potential (RMP) and membrane excitability of NG108-15 cells differentiated under serum-free media with representative extracellular matrix (ECM) protein components as the substrate. Surfaces coated with collagen IV and a laminin-1 synthetic peptide induced a significantly (P < 0.05) more hyperpolarized RMP than control polystyrene surfaces. For example, after > or =8 days in culture NG108-15 cells plated on polystyrene exhibited a RMP of -33.2+/-0.8 mV (mean+/-SEM, n=158 cells) whereas cells cultured on the laminin-1 peptide C16 and collagen IV showed a RMP of -37.6+/-0.7 mV (n=157) and -37.5+/-1.5 mV (n=68), respectively. Furthermore, the proportions of cells on ECM substrates showing membrane excitability, i.e. evoked action potentials (APs) and the capability for regular firing, were significantly greater compared to those cells cultured on polystyrene. Among excitable cells cultured on the different substrates, characteristics of the action potentials, such as AP duration, amplitude, and the maximum rate of rise, dV/dtMAX, were examined in detail. While little or no differences were observed between polystyrene and the laminin-1 peptide groups, significant differences in the AP parameters were apparent for collagen IV. For example, dV/dtMAX for polystyrene and the laminin-1 peptide C16 were only 71.7+/-24.5 V/s (n=11) and 59.0+/-8.9 V/s (n=9), respectively, whereas cells cultured on collagen IV surfaces exhibited a dV/dtMAX reaching 156.1+/-22.0 V/s (n=7). These data support a role for ECM components in the maintenance of the RMP and membrane excitability in NG108-15 cells.