title: Experimental study of tendon healing early phase: is IGF-1 expression influenced by platelet rich plasma gel?
abstract: BACKGROUND
  It is well established that growth factors play a critical role in the healing process of connective tissues. To our knowledge, there are no studies in literature concerning the influence of PRP on growth factors expression.
  
  
  OBJECTIVE
  The aim of this study was to assess the effect of a single application of platelet rich plasma (PRP) gel in a patellar tendon defect on the spatial and temporal expression of Insulin-like Growth Factor 1 (IGF-1) during tendon healing.
  
  
  METHODS
  Twenty-four animals were randomized to receive PRP (PRPFast, Bioteck) in a gel form (PRP group) and 24 to serve as untreated controls (Control group). A defect of 3 mm x 10 mm was surgically created on the tendon under general anaesthetic and in the PRP group, PRP gel was applied to fill the tendon defect whereas no treatment was applied in the control group. Six animals (12 limbs) from each treatment-group were sacrificed after one, two, three and four weeks following treatment. Histological and immunohistochemical staining were performed.
  
  
  RESULTS
  Histology revealed a faster healing process in the tendons of PRP group in comparison with the controls. In the first 2 weeks of healing, IGF-1 was found intracellularly in various type cells, whereas in the last 2 weeks of healing, IGF-1 was detected mainly in tenocytes. Both cytoplasmic and nuclear expressions were present, whereas the larger amounts of immunoexpression were localized in both epitenon and endotenon. A superior expression of IGF-1 was seen in PRP group compared with controls (p<0.0001) in both the epitenon and endotenon at each time point except at 4th week of healing where a superior expression of IGF-1 was shown in the endotenon of control group, compared to the PRP group (p<0.0001).
  
  
  CONCLUSIONS
  PRP may improve tendon defect healing by overexpression of IGF-1.
  
  
  METHODS
  Laboratory control animal study.
authors.affiliation: Democritus University Hospital of Thrace, Department of Orthopaedic and Trauma Surgery, Alexandroupolis, Dragana, Greece. dimitrislyras@yahoo.gr
authors.forename: D N
authors.initials: DN
authors.lastname: Lyras
authors.forename: K
authors.initials: K
authors.lastname: Kazakos
authors.forename: G
authors.initials: G
authors.lastname: Agrogiannis
authors.forename: D
authors.initials: D
authors.lastname: Verettas
authors.forename: A
authors.initials: A
authors.lastname: Kokka
authors.forename: G
authors.initials: G
authors.lastname: Kiziridis
authors.forename: E
authors.initials: E
authors.lastname: Chronopoulos
authors.forename: M
authors.initials: M
authors.lastname: Tryfonidis
mesh_terms: D000818:Animals; D005782:Gels / Q000378:metabolism; D007124:Immunoenzyme Techniques; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D017847:Patellar Ligament / Q000378:metabolism* / Q000473:pathology; D053657:Platelet-Rich Plasma / Q000378:metabolism*; D011817:Rabbits; D011897:Random Allocation; D018709:Statistics, Nonparametric; D014945:Wound Healing / Q000502:physiology
chemical_list: D005782:Gels; D007334:Insulin-Like Growth Factor I