title: The Neuro-spheroid--A novel 3D in vitro model for peripheral nerve regeneration.
abstract: BACKGROUND
  In order to reduce in vivo animal experiments in peripheral nerve regeneration research, in vitro models are desirable. Common two dimensional (2D) co-culture models lack the complex interactions of three dimensional (3D) physiological structures. The aim of the study was to establish a neuronal 3D spheroidal sprouting assay for peripheral nerve regeneration.
  
  
  METHODS
  Spheroids consisting of Schwann cells (SC, 500 cells/spheroid) and NG108-15 cells (NG, 50 cells/spheroid), a hybrid cell line, were formed in hanging drops and were embedded in a 3D collagen matrix. Spheroid sprout lengths were compared to those of the neurites of NG in a 2D co-culture with SC. Lengths were measured using phase contrast images taken every day over 10 days. Additionally we took fluorescence images to visualize the PKH26-labeled NG in both culture systems.
  
  
  RESULTS
  Initially thin neurites grew out in both co-cultures, over time the sprouts' diameter in the 3D culture increased. The direct comparison of the sprout length revealed significantly longer neurites in the 3D co-culture from day 7 until day 10 (p<0.001).
  
  
  METHODS
  Other co-culture models either display processes in 2D or need complex matrices to create 3D structures. Our spheroidal model is easy to establish, highly flexible and nevertheless 3D.
  
  
  CONCLUSIONS
  The 3D-Schwann cell-neuron spheroid model shows that by simply transferring a 2D into a 3D co-culture with multiplication of cell-cell contacts, a significant increase of neurite length can be achieved. The model is a relatively simple method for the investigation of neurite development in vitro.
authors.affiliation: Department of Plastic and Hand Surgery, University Medical Center Freiburg, Freiburg, Germany. Electronic address: daniel.kraus@uniklinik-freiburg.de.
authors.forename: D
authors.initials: D
authors.lastname: Kraus
authors.affiliation: Clinic for Neurology, Ortenau Klinikum Lahr-Ettenheim, Lahr, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Boyle
authors.affiliation: Department of Hand, Plastic and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Leibig
authors.affiliation: Department of Plastic and Hand Surgery, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: G B
authors.initials: GB
authors.lastname: Stark
authors.affiliation: Department of Plastic and Hand Surgery, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Penna
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D049109:Cell Proliferation; D002478:Cells, Cultured; D018920:Coculture Techniques; D024042:Collagen Type I / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008954:Models, Biological; D009416:Nerve Regeneration / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009930:Organic Chemicals / Q000378:metabolism; D010525:Peripheral Nerves / Q000166:cytology*; D051381:Rats; D009418:S100 Proteins / Q000378:metabolism; D012583:Schwann Cells / Q000502:physiology*; D018874:Spheroids, Cellular; D013997:Time Factors
chemical_list: D024042:Collagen Type I; D009930:Organic Chemicals; C070080:PKH 26; D009418:S100 Proteins
keywords: 3D in vitro model; NG108-15 cells; Peripheral nerve regeneration; Schwann cells; Sprouting assay