title: Semi-automated counting of axon regeneration in poly(lactide co-glycolide) spinal cord bridges.
abstract: BACKGROUND
  Spinal cord injury (SCI) is a debilitating event with multiple mechanisms of degeneration leading to life-long paralysis. Biomaterial strategies, including bridges that span the injury and provide a pathway to reconnect severed regions of the spinal cord, can promote partial restoration of motor function following SCI. Axon growth through the bridge is essential to characterizing regeneration, as recovery can occur via other mechanisms such as plasticity. Quantitative analysis of axons by manual counting of histological sections can be slow, which can limit the number of bridge designs evaluated. In this study, we report a semi-automated process to resolve axon numbers in histological sections, which allows for efficient analysis of large data sets.
  
  
  METHODS
  Axon numbers were estimated in SCI cross-sections from animals implanted with poly(lactide co-glycolide) (PLG) bridges with multiple channels for guiding axons. Immunofluorescence images of histological sections were filtered using a Hessian-based approach prior to threshold detection to improve the signal-to-noise ratio and filter out background staining associated with PLG polymer.
  
  
  RESULTS
  Semi-automated counting successfully recapitulated average axon densities and myelination in a blinded PLG bridge implantation study.
  
  
  METHODS
  Axon counts obtained with the semi-automated technique correlated well with manual axon counts from blinded independent observers across sections with a wide range of total axons.
  
  
  CONCLUSIONS
  This semi-automated detection of Hessian-filtered axons provides an accurate and significantly faster alternative to manual counting of axons for quantitative analysis of regeneration following SCI.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Dylan A
authors.initials: DA
authors.lastname: McCreedy
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Margul
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA; Department of Bioengineering, University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Seidlits
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Jennifer T
authors.initials: JT
authors.lastname: Antane
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Thomas
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Sissman
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Boehler
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Dominique R
authors.initials: DR
authors.lastname: Smith
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Sam W
authors.initials: SW
authors.lastname: Goldsmith
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Todor V
authors.initials: TV
authors.lastname: Kukushliev
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Lamano
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Bansi H
authors.initials: BH
authors.lastname: Vedia
authors.affiliation: Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
authors.forename: Ting
authors.initials: T
authors.lastname: He
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA. Electronic address: ldshea@umich.edu.
authors.forename: Lonnie D
authors.initials: LD
authors.lastname: Shea
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000473:pathology / Q000502:physiology* / Q000648:ultrastructure; D001672:Biocompatible Materials / Q000627:therapeutic use*; D001330:Electronic Data Processing; D005260:Female; D019344:Lactic Acid / Q000627:therapeutic use*; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D004676:Myelin Basic Protein / Q000378:metabolism; D009416:Nerve Regeneration / Q000502:physiology*; D016900:Neurofilament Proteins / Q000378:metabolism; D011100:Polyglycolic Acid / Q000627:therapeutic use*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000601:surgery*
chemical_list: D001672:Biocompatible Materials; D004676:Myelin Basic Protein; D016900:Neurofilament Proteins; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid
keywords: Automated quantification; Hessian filter; Myelination; Spinal cord injury
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