Induced MSC Are Not Neurons Figure 7. Electrophysiological recordings of K+ current. A) Voltage-dependent K+ current recorded from primary culture neuron (A1), non- induced MSC (A2) and chemically-induced MSC (A3 and A4). B) I/V curves calculated from traces in A showing decreased K+ current for treated MSC (B1, B2). C) Single-channel K+ current recordings showing frequent channel opening in primary culture neurons (C1) but absent in chemically-induced MSC (C2). doi:10.1371/journal.pone.0005222.g007 action) and can behave in a non-physiological way, leading to artifacts [35]. Alternatively, neurons derived from bone marrow stromal cells after transplantation could be explained by cell fusion, giving rise to uncertainties over ‘‘real’’ transdifferentiation [36,37]. In this context, the demonstration of whether or not MSC can differentiate into neurons is not unequivocal. Herein we emphasize that morphological and gene expression alterations should be accompanied by electrophysiological demonstrations that MSC derived neurons are functional cells. The main findings of this work are summarized: i) the seeming induction triggered by one specific protocol based on chemical compounds is reversible and caused by cytoplasmic retraction due PLoS ONE | www.plosone.org 8 April 2009 | Volume 4 | Issue 4 | e5222