ABSTRACT
Fluorescence-activated cell sorting (FACS) applying flow cytometry to separate cells on a molecular basis is a widespread method. We demonstrate that both fluorescent and unlabeled live cells in a Petri dish observed with a microscope can be automatically recognized by computer vision and picked up by a computer-controlled micropipette. This method can be routinely applied as a FACS down to the single cell level with a very high selectivity. Sorting resolution, i.e., the minimum distance between two cells from which one could be selectively removed was 50-70 micrometers. Survival rate with a low number of 3T3 mouse fibroblasts and NE-4C neuroectodermal mouse stem cells was 66 ± 12% and 88 ± 16%, respectively. Purity of sorted cultures and rate of survival using NE-4C/NE-GFP-4C co-cultures were 95 ± 2% and 62 ± 7%, respectively. Hydrodynamic simulations confirmed the experimental sorting efficiency and a cell damage risk similar to that of normal FACS.
Subject(s)
Cell Separation/instrumentation , Cell Separation/methods , Image Processing, Computer-Assisted/methods , 3T3 Cells , Animals , Animals, Newborn , Astrocytes/cytology , Cell Line , Cell Survival , Cells, Cultured , Coculture Techniques , Flow Cytometry/instrumentation , Flow Cytometry/methods , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HEK293 Cells , Humans , Keratinocytes/cytology , Mice , Mice, Transgenic , Microglia/cytology , Microscopy, Fluorescence , Microscopy, Phase-Contrast , Microscopy, Video , Reproducibility of ResultsABSTRACT
Despite the accumulating data on the molecular and cell biological characteristics of neural stem/progenitor cells, their electrophysiological properties are not well understood. In the present work, changes in the membrane properties and current profiles were investigated in the course of in vitro-induced neuron formation in NE-4C cells. Induction by retinoic acid resulted in neuronal differentiation of about 50% of cells. Voltage-dependent Na+ currents appeared early in neuronal commitment, often preceding any morphological changes. A-type K+ currents were detected only at the stage of network formation by neuronal processes. Flat, epithelial- like, nestin-expressing progenitors persisted beside differentiated neurons and astrocytes. Stem/progenitor cells were gap junction coupled and displayed large, symmetrical, voltage-independent currents. By the blocking of gap junction communication, voltage-independent conductance was significantly reduced, and delayed-rectifying K+ currents became detectable. Our data indicate that voltage-independent symmetrical currents and gap junction coupling are characteristic physiological features of neural stem and progenitor cells regardless of the developmental state of their cellular environment.
Subject(s)
Astrocytes/physiology , Neurons/physiology , Stem Cells/physiology , Animals , Astrocytes/cytology , Cell Differentiation , Cell Line, Transformed , Cell Membrane/physiology , Delayed Rectifier Potassium Channels/physiology , Ectoderm/cytology , Gap Junctions/physiology , Immunohistochemistry , Ion Channel Gating , Mice , Neurons/cytology , Patch-Clamp Techniques , Sodium Channels/physiology , Stem Cells/cytology , Tretinoin/pharmacologyABSTRACT
gamma-Aminobutyric acid (GABA) has been known to function as an autocrine/paracrine signal molecule in addition to its well-known inhibitory neurotransmitter function. Studies on the developing brain and on primary brain cell cultures provided evidence for a variety of GABA functions in periods preceding the formation of synapses. The exact role of GABA in the early neural development, however, is still not well understood. In this study, one-cell-derived NE-4C neuroectodermal stem cells were induced to form neurons and astrocytes in vitro, and the role of GABA was investigated in defined phases of neurogenesis. Noninduced NE-4C cells contained GABA, expressed GABA(A)R alpha subunits, and carried functional GABA(A) ion channels. A moderate cytoplasmic GABA content was detected during the entire period of differentiation. By the time of the formation of differentiated neurons, neuron-like cells with both high and low GABA content were clearly distinguishable. HPLC analysis indicated that NE-4C cells released GABA into their fluid environment during all stages of neuronal development. By using the patch-clamp technique, GABA-evoked currents were recorded during the entire proliferation/differentiation period, whereas a GABA-evoked increase in intracellular Ca(2+) was detected only during the maturation of postmitotic neuronal precursors. Bicuculline blocked both the ion currents and the [Ca(2+)](i) increase in response to GABA. Neuron formation was facilitated by GABA through GABA(A) ion channels during postmitotic differentiation, but not earlier during the phases of cell fate commitment. Although the data clearly demonstrate an early responsiveness to GABA, understanding the significance of GABA influence in early neural cell fate decisions will require further investigation.
