title: Sonoelastography can be used to monitor the restoration of Achilles tendon elasticity after injury.
abstract: OBJECTIVE
  The aim of the current study was to evaluate an ultrasound approach for depicting elastic recovery after stem cell application on injured Achilles tendons.
  
  
  METHODS
  A rabbit Achilles tendon injury model was used and randomized hind limbs received an extracellular matrix either with autologous mesenchymal stem cells (group 2, n = 6) or without (group 3, n = 6). The cells were harvested from the rabbits' nuchal fat body. Untreated Achilles tendons (group 1, n = 6) served as controls. Specimens were harvested after 8 weeks and analyzed longitudinally for elasticity using a high resolution 6-15 MHz matrix linear probe. For each tendon, real-time color-coded sonoelastography sequences were recorded for 20 seconds and 10 color histogram frames were obtained. Defined regions of interest (ROIs) were placed on the injury (n = 3) and on the adjacent uninjured tendon tissue (n = 3). In total, 180 measurements were obtained for semi-quantitative analysis.
  
  
  RESULTS
  Repeated measures ANOVA demonstrated a higher elasticity for the stem cell-seeded matrix (group 2) in comparison to the unseeded matrix (group 3) (p < 0.001). No significant difference was found between the injured tendon tissue treated with stem cell-seeded matrix (group 2) and the uninjured Achilles tendons (group 1) (p > 0.05). Moreover, no differences were found between the measurements at different points in time (p > 0.05).
  
  
  CONCLUSIONS
  Our results indicate that autologous mesenchymal stem cell application successfully restores the mechanical properties of injured tendon tissue. Furthermore, sonoelastography makes it possible to monitor the elasticity of injured Achilles tendons.
authors.affiliation: Plastische Chirurgie, Universität Regensburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Gehmert
authors.forename: E M
authors.initials: EM
authors.lastname: Jung
authors.forename: T
authors.initials: T
authors.lastname: Kügler
authors.forename: S
authors.initials: S
authors.lastname: Klein
authors.forename: S
authors.initials: S
authors.lastname: Gehmert
authors.forename: K
authors.initials: K
authors.lastname: Zeitler
authors.forename: M
authors.initials: M
authors.lastname: Loibl
authors.forename: L
authors.initials: L
authors.lastname: Prantl
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000473:pathology; D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D004195:Disease Models, Animal; D004548:Elasticity / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005109:Extracellular Matrix; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation; D011817:Rabbits; D013708:Tendon Injuries / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy*; D014945:Wound Healing / Q000502:physiology*