From molecular structure to tissue architecture: collagen organization probed by SHG microscopy.
Second-harmonic generation (SHG) microscopy is a fantastic tool for imaging collagen and probing its hierarchical organization from molecular scale up to tissue architectural level. In fact, SHG combines the advantages of a non-linear microscopy approach with a coherent modality able to probe molecular organization. In this manuscript we review the physical concepts describing SHG from collagen, highlighting how this optical process allows to probe structures ranging from molecular sizes to tissue architecture, through image pattern analysis and scoring methods. Starting from the description of the most relevant approaches employing SHG polarization anisotropy and forward - backward SHG detection, we then focus on the most relevant methods for imaging and characterizing collagen organization in tissues through image pattern analysis methods, highlighting advantages and limitations of the methods applied to tissue imaging and to potential clinical applications.
European Laboratory for Non-linear Spectroscopy LENS, Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy. rcicchi@lens.unifi.it
Riccardo
R
Cicchi
Nadine
N
Vogler
Dimitrios
D
Kapsokalyvas
Benjamin
B
Dietzek
Jürgen
J
Popp
Francesco Saverio
FS
Pavone
D000818:Animals; D016880:Anisotropy; D003238:Connective Tissue / Q000378:metabolism / Q000648:ultrastructure; D024022:Fibrillar Collagens / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D005583:Fourier Analysis; D006801:Humans; D008853:Microscopy / Q000379:methods* / Q000706:statistics & numerical data; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods; D008859:Microscopy, Polarization / Q000379:methods; D008962:Models, Theoretical; D057054:Molecular Imaging / Q000379:methods; D015394:Molecular Structure; D055620:Optical Phenomena; D010363:Pattern Recognition, Automated; D014018:Tissue Distribution
D024022:Fibrillar Collagens