title: Hierarchical model of fibrillar collagen organization for interpreting the second-order susceptibility tensors in biological tissue.
abstract: The second-order nonlinear polarization properties of fibrillar collagen in various rat tissues (vertebrae, tibia, tail tendon, dermis, and cornea) are investigated with polarization-dependent second-harmonic generation (P-SHG) microscopy. Three parameters are extracted: the second-order susceptibility ratio, R = [Formula: see text] ; a measure of the fibril distribution asymmetry, |A|; and the weighted-average fibril orientation, <δ>. A hierarchical organizational model of fibrillar collagen is developed to interpret the second-harmonic generation polarization properties. Highlights of the model include: collagen type (e.g., type-I, type-II), fibril internal structure (e.g., straight, constant-tilt), and fibril architecture (e.g., parallel fibers, intertwined, lamellae). Quantifiable differences in internal structure and architecture of the fibrils are observed. Occurrence histograms of R and |A| distinguished parallel from nonparallel fibril distributions. Parallel distributions possessed low parameter values and variability, whereas nonparallel distributions displayed an increase in values and variability. From the P-SHG parameters of vertebrae tissue, a three-dimensional reconstruction of lamellae of intervertebral disk is presented.
authors.affiliation: Department of Physics, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Adam E
authors.initials: AE
authors.lastname: Tuer
authors.forename: Margarete K
authors.initials: MK
authors.lastname: Akens
authors.forename: Serguei
authors.initials: S
authors.lastname: Krouglov
authors.forename: Daaf
authors.initials: D
authors.lastname: Sandkuijl
authors.forename: Brian C
authors.initials: BC
authors.lastname: Wilson
authors.forename: Cari M
authors.initials: CM
authors.lastname: Whyne
authors.forename: Virginijus
authors.initials: V
authors.lastname: Barzda
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D024022:Fibrillar Collagens / Q000737:chemistry*; D007403:Intervertebral Disc / Q000033:anatomy & histology; D008859:Microscopy, Polarization; D008958:Models, Molecular; D009928:Organ Specificity; D051381:Rats; D013623:Tail; D013710:Tendons
chemical_list: D024022:Fibrillar Collagens