title: Reevaluation of in vitro differentiation protocols for bone marrow stromal cells: disruption of actin cytoskeleton induces rapid morphological changes and mimics neuronal phenotype.
abstract: Bone marrow stromal cells (MSC), which represent a population of multipotential mesenchymal stem cells, have been reported to undergo rapid and robust transformation into neuron-like phenotypes in vitro following treatment with chemical induction medium including dimethyl sulfoxide (DMSO; Woodbury et al. [2002] J. Neurosci. Res. 96:908). In this study, we confirmed the ability of cultured rat MSC to undergo in vitro osteogenesis, chondrogenesis, and adipogenesis, demonstrating differentiation of these cells to three mesenchymal cell fates. We then evaluated the potential for in vitro neuronal differentiation of these MSC, finding that changes in morphology upon addition of the chemical induction medium were caused by rapid disruption of the actin cytoskeleton. Retraction of the cytoplasm left behind long processes, which, although strikingly resembling neurites, showed essentially no motility and no further elaboration during time-lapse studies. Similar neurite-like processes were induced by treating MSC with DMSO only or with actin filament-depolymerizing agents. Although process formation was accompanied by rapid expression of some neuronal and glial markers, the absence of other essential neuronal proteins pointed toward aberrantly induced gene expression rather than toward a sequence of gene expression as is required for neurogenesis. Moreover, rat dermal fibroblasts responded to neuronal induction by forming similar processes and expressing similar markers. These studies do not rule out the possibility that MSC can differentiate into neurons; however, we do want to caution that in vitro differentiation protocols may have unexpected, misleading effects. A dissection of molecular signaling and commitment events may be necessary to verify the ability of MSC transdifferentiation to neuronal lineages.
authors.affiliation: Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
authors.forename: Birgit
authors.initials: B
authors.lastname: Neuhuber
authors.forename: Gianluca
authors.initials: G
authors.lastname: Gallo
authors.forename: Linda
authors.initials: L
authors.lastname: Howard
authors.forename: Lisa
authors.initials: L
authors.lastname: Kostura
authors.forename: Alastair
authors.initials: A
authors.lastname: Mackay
authors.forename: Itzhak
authors.initials: I
authors.lastname: Fischer
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D015415:Biomarkers; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D019070:Cell Lineage / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects / Q000502:physiology; D003470:Culture Media / Q000494:pharmacology; D004627:Embryonic Induction / Q000187:drug effects / Q000235:genetics; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics; D006133:Growth Substances / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000187:drug effects; D016501:Neurites / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology; D010641:Phenotype; D051381:Rats; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000199:Actins; D015415:Biomarkers; D003470:Culture Media; D006133:Growth Substances; D009419:Nerve Tissue Proteins