title: Organization of collagen bundles during tendon healing in rats treated with L-NAME.
abstract: The Achilles tendon can support high tension forces and may experience lesions. The damaged tissue does not regenerate completely, with the organization and mechanical properties of the repaired tendon being inferior to those of a healthy tendon. Nitric oxide (NO) plays an important role in wound repair. We have examined the structural reorganization and repair in Achilles tendon after injury in rats treated with the NO synthase inhibitor L-NAME. The right Achilles tendon of male Wistar rats was partially transected. One group of rats was treated with L-NAME (~300 mg/kg per day, given in drinking water) for 4 days prior to tendon sectioning and throughout the post-operative period. Control rats received water without L-NAME. The tendons were excised at 7, 14, and 21 days post-injury and used to quantify hydroxyproline and for mechanical tests. Tendons were also processed for histomorphological analysis by polarized light microscopy, which showed that the collagen fibers were disorganized by day 7 in non-treated and L-NAME-treated rats. In non-treated rats, the organization of the extracellular matrix was more homogeneous by days 14 and 21 compared with day 7, although this homogeneity was less than that in normal tendon. In contrast, in injured tendons from L-NAME-treated rats, the collagen fibers were still disorganized on day 21. Tendons from treated rats had more hydroxyproline but lower mechanical properties compared with those from non-treated rats. Thus, NO modulates tendon healing, with a reduction in NO biosynthesis delaying reorganization of the extracellular matrix, especially collagen.
authors.affiliation: Department of Anatomy, Cell Biology, Physiology and Biophysics, Institute of Biology, State University of Campinas, UNICAMP, SP, Brazil.
authors.forename: Tatiana Carla
authors.initials: TC
authors.lastname: Tomiosso
authors.forename: Wilson Romero
authors.initials: WR
authors.lastname: Nakagaki
authors.forename: Laurecir
authors.initials: L
authors.lastname: Gomes
authors.forename: Stephen
authors.initials: S
authors.lastname: Hyslop
authors.forename: Edson Rosa
authors.initials: ER
authors.lastname: Pimentel
mesh_terms: D000125:Achilles Tendon / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006909:Hydroxyproline / Q000378:metabolism; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000187:drug effects; D013708:Tendon Injuries / Q000378:metabolism*; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D003094:Collagen; D019001:Nitric Oxide Synthase; D006909:Hydroxyproline; D019331:NG-Nitroarginine Methyl Ester