INJURING NEURONS INDUCES NEURONAL DIFFERENTIATION IN A POPULATION OF HIPPOCAMPAL PRECURSOR CELLS IN CULTURE
Abstract number :
3.006
Submission category :
Year :
2002
Submission ID :
2585
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Marc A. Dichter, Henry C. Tseng, Stephen J. Rueegg, Margaret Maronski, Judith B. Grinspan. Neurology and David Mahoney Institute of Neurological Sciences, University of Pennsylvania, Philadelphia, PA; Research Neurology, Children[ssquote]s Hospital of Phi
RATIONALE: Multipotent hippocampal precursor cells (HPCs) were identified in hippocampal cell cultures but traditional neuronal differentiation factors were unable to induce differentiation into cells with neuronal phenotype. We attempted to determine if neuronal differentiation could be induced by injuring nearby mature neurons in the cultures.
METHODS: Cultures of dissociated rat hippocampal neurons were grown in serum free conditions in the presence of platelet-derived growth factor-beta. After 3 weeks, the cultures were first exposed to BrdU for 48 hours and then were treated with excitotoxic concentrations of glutamate or NMDA. Cultures were also treated with supernatants from injured cultures or with cell lysates from sonicated cultures (conditioned medium (CM) experiments). Treated cultures were then allowed to survive for 48 to 96 hours and remaining cells were double stained for BrdU and neuronal markers (MAP2, TUJ1, neurofilament, GluR2/3). Small cells with neuronal appearance were also recorded with patch clamp electrodes.
RESULTS: Within hours of neuronal injury or treatment with CM containing some unknown factor ([dsquote]factor X[dsquote]) HPCs began to extend processes and became positive for the neuronal marker MAP2. Over the next 48 hours, staining intensified and processes became longer. Treated HPCs also stained for neurofilament, TUJ1, and GluR2/3. Patch clamp recordings of the HPCs before differentiation revealed very small, glial-like sodium currents and larger potassium currents. After excitotoxic injury to the cultures or treatment with factor X, the differentiating HPCs exhibited larger sodium currents and some also developed spontaneous synaptic potentials, indicating connections with nearby neurons.
CONCLUSIONS: Injured or dying neurons can release a factor that promotes the differentiation of multipotent precursor cells into cells with neuronal phenotype. This may be related to the neo-neuronogenesis seen in adult hippocampus after status epilepticus. The identification of factor X remains to be determined, as does the mechanism by which it induces neuronal differentiation. At the end of this activity, participants will appreciate a new mechanism for inducing neuronal differentiation in hippocampal progenitor cells that may play a role in epileptogenesis.
[Supported by: NS 24260]