title: Second harmonic generation microscopy reveals altered collagen microstructure in usual interstitial pneumonia versus healthy lung.
abstract: BACKGROUND
  It is not understood why some pulmonary fibroses such as cryptogenic organizing pneumonia (COP) respond well to treatment, while others like usual interstitial pneumonia (UIP) do not. Increased understanding of the structure and function of the matrix in this area is critical to improving our understanding of the biology of these diseases and developing novel therapies. The objectives herein are to provide new insights into the underlying collagen- and matrix-related biological mechanisms driving COP versus UIP.
  
  
  METHODS
  Two-photon second harmonic generation (SHG) and excitation fluorescence microscopies were used to interrogate and quantify differences between intrinsic fibrillar collagen and elastin matrix signals in healthy, COP, and UIP lung.
  
  
  RESULTS
  Collagen microstructure was different in UIP versus healthy lung, but not in COP versus healthy, as indicated by the ratio of forward-to-backward propagating SHG signal (FSHG/BSHG). This collagen microstructure as assessed by FSHG/BSHG was also different in areas with preserved alveolar architecture adjacent to UIP fibroblastic foci or honeycomb areas versus healthy lung. Fibrosis was evidenced by increased col1 and col3 content in COP and UIP versus healthy, with highest col1:col3 ratio in UIP. Evidence of elastin breakdown (i.e. reduced mature elastin fiber content), and increased collagen:mature elastin ratios, were seen in COP and UIP versus healthy.
  
  
  CONCLUSIONS
  Fibrillar collagen's subresolution structure (i.e. "microstructure") is altered in UIP versus COP and healthy lung, which may provide novel insights into the biological reasons why unlike COP, UIP is resistant to therapies, and demonstrates the ability of SHG microscopy to potentially distinguish treatable versus intractable pulmonary fibroses.
authors.affiliation: Department of Medicine, University of Rochester, Rochester, NY, USA. Matt_Kottmann@URMC.Rochester.edu.
authors.forename: Robert Matthew
authors.initials: RM
authors.lastname: Kottmann
authors.affiliation: Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA. jsharp7@u.rochester.edu.
authors.forename: Jesse
authors.initials: J
authors.lastname: Sharp
authors.affiliation: Department of Medicine, University of Rochester, Rochester, NY, USA. Kristina_Owens@urmc.rochester.edu.
authors.forename: Kristina
authors.initials: K
authors.lastname: Owens
authors.affiliation: Department of Biostatistics and Computational Biology, University of Rochester, Rochester, NY, USA. psalzman@bst.rochester.edu.
authors.forename: Peter
authors.initials: P
authors.lastname: Salzman
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, NY, USA. Guang-qian_Xiao@URMC.Rochester.edu.
authors.forename: Guang-Qian
authors.initials: GQ
authors.lastname: Xiao
authors.affiliation: Department of Environmental Medicine, University of Rochester, Rochester, NY, USA. Richard_Phipps@urmc.rochester.edu.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Phipps
authors.affiliation: Department of Medicine, University of Rochester, Rochester, NY, USA. Patricia_Sime@urmc.rochester.edu.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Sime
authors.affiliation: Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA. Edward_Brown@urmc.rochester.edu.
authors.forename: Edward B
authors.initials: EB
authors.lastname: Brown
authors.affiliation: Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA. Seth_Perry@urmc.rochester.edu.
authors.forename: Seth W
authors.initials: SW
authors.lastname: Perry
mesh_terms: D003094:Collagen / Q000648:ultrastructure*; D006801:Humans; D008168:Lung / Q000473:pathology* / Q000648:ultrastructure*; D017563:Lung Diseases, Interstitial / Q000473:pathology*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*
chemical_list: D003094:Collagen