title: Effects of laser irradiation on collagen organization in chemically induced degenerative annulus fibrosus of lumbar intervertebral disc.
abstract: OBJECTIVE
  The number of in vitro experimental studies was carried out with the use of intact tissues to establish a mechanism of laser-tissue interaction. However, in the process of degeneration, both biochemical composition and behavior of the disc were altered drastically. The objective of this study was to evaluate the role of the main matrix components in laser modification of annulus fibrosus (AF) under IR laser irradiation.
  
  
  METHODS
  The samples of AF in a motion segment after hyaluronidase treatment, trypsin digestion and glycation by glyceraldehyde were heated in hydrothermal bath (95 degrees C, 2 min) or irradiated by laser at 1.56 microm. Specimens were imaged by cross-polarization optical coherence tomography (CP-OCT), and then analyzed by differential scanning calorimery (DSC).
  
  
  CONCLUSIONS
  According to CP-OCT and DSC data non-significant alteration was revealed in AF after hyaluronidase treatment, glycation led to stabilization of annulus collagen and trypsin digestion resulted in a noticeable impairment of collagen fibrils. Laser treatment induced subsequent damages of AF matrix but these damages cannot be explained by laser heating only. The specificity of chemical modification of AF matrix has an influence on a character of collagen network alteration due to IR laser effect. Minimal and maximal alterations are observed for hyaluronidase and trypsin treated samples respectively. Glyceraldehyde fixed samples showed failure of the collagen structure after moderate laser treatment; at the same time thermal denaturation of collagen macromolecules was negligible. We assume that a mechanical effect of laser irradiation plays an important role in laser-induced annulus collagen modification and propose the scheme of physico-chemical process occurring under non-uniform IR laser treatment in AF tissue.
  
  
  CONCLUSIONS
  CP-OCT and DSC techniques allow us to record the alteration of collagen network organization as a result of chemical modification. There were detected significant and specific effects of the biochemical composition and material properties on the response of AF collagen network on laser irradiation. The results go in accordance with our hypothesis that the primary effect of laser influence on collagen network under tension is the mechanical damage of collagen fiber.
authors.affiliation: Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow, Russia. nyu@kge.msu.ru
authors.forename: Natalia
authors.initials: N
authors.lastname: Ignatieva
authors.forename: Olga
authors.initials: O
authors.lastname: Zakharkina
authors.forename: Irina
authors.initials: I
authors.lastname: Andreeva
authors.forename: Emil
authors.initials: E
authors.lastname: Sobol
authors.forename: Vladislav
authors.initials: V
authors.lastname: Kamensky
authors.forename: Valery
authors.initials: V
authors.lastname: Lunin
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D024022:Fibrillar Collagens / Q000378:metabolism / Q000528:radiation effects*; D006821:Hyaluronoglucosaminidase / Q000494:pharmacology; D007403:Intervertebral Disc / Q000187:drug effects* / Q000528:radiation effects*; D007404:Intervertebral Disc Chemolysis / Q000379:methods; D028022:Low-Level Light Therapy / Q000379:methods*; D008159:Lumbar Vertebrae; D008297:Male; D011336:Probability; D011817:Rabbits; D011897:Random Allocation; D012680:Sensitivity and Specificity; D013122:Spinal Diseases / Q000628:therapy*; D041623:Tomography, Optical Coherence; D014357:Trypsin / Q000494:pharmacology
chemical_list: D024022:Fibrillar Collagens; D006821:Hyaluronoglucosaminidase; D014357:Trypsin