title: The effects of laser irradiation of cartilage on chondrocyte gene expression and the collagen matrix.
abstract: OBJECTIVE
  Laser reshaping of cartilage is an emerging technology aimed at replacing conventional techniques for aesthetic and reconstructive surgery. Little is known about the mechanisms of wound healing following the photothermal heating during laser reshaping and, ultimately, how collagen remodels in the irradiated tissue. Healthy hyaline and elastic cartilage as found in the ear, nose, larynx, and trachea does not express collagen type I which is characteristic of fibro-cartilage and scar tissue. The aim of the study was to determine if collagen I and II gene expression occurs within laser irradiated rabbit septal cartilage.
  
  
  METHODS
  Nasal septum harvested from freshly euthanized New Zealand White rabbits were irradiated with an Nd:YAG laser. After 2 weeks in culture, the laser spot and surrounding non-irradiated regions were imaged using immunofluorescence staining and evaluated using reverse transcription polymerase chain reaction (RT-PCR) to determine the presence of collagen I and II, and ascertain collagen I and II gene expression, respectively.
  
  
  RESULTS
  All laser irradiated specimens showed a cessation in collagen II gene expression within the center of the laser spot. Collagen II was expressed in the surrounding region encircling the laser spot and within the non-irradiated periphery in all specimens. Immunohistochemistry identified only type II collagen. Neither collagen I gene expression nor immunoreactivity were identified in any specimens regardless or irradiation parameters.
  
  
  CONCLUSIONS
  Laser irradiation of rabbit septal cartilage using dosimetry parameters similar to those used in laser reshaping does not result in the detection of either collagen I gene expression or immunoreactivity. Only collagen type II was noted after laser exposure in vitro following cell culture, which suggests that the cellular response to laser irradiation is distinct from that observed in conventional wound healing. Laser irradiation of cartilage can leave an intact collagen matrix which likely allows chondrocyte recovery on an intact scaffold.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, Irvine, California 92612, USA.
authors.forename: Paul K
authors.initials: PK
authors.lastname: Holden
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.forename: Victor
authors.initials: V
authors.lastname: Da Costa
authors.forename: Chung-Ho
authors.initials: CH
authors.lastname: Sun
authors.forename: Susan V
authors.initials: SV
authors.lastname: Bryant
authors.forename: David M
authors.initials: DM
authors.lastname: Gardiner
authors.forename: Brian J F
authors.initials: BJ
authors.lastname: Wong
mesh_terms: D000818:Animals; D019902:Chondrocytes / Q000528:radiation effects; D003094:Collagen / Q000235:genetics* / Q000528:radiation effects; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D005109:Extracellular Matrix / Q000235:genetics / Q000528:radiation effects; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D028022:Low-Level Light Therapy / Q000379:methods*; D055171:Nasal Cartilages / Q000473:pathology / Q000528:radiation effects*; D009300:Nasal Septum / Q000473:pathology / Q000528:radiation effects*; D011817:Rabbits; D011829:Radiation Dosage; D012038:Regeneration / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity
chemical_list: D003094:Collagen