title: Characteristics of Reconstituted Lyophilized Tendon Hydrogel: An Injectable Scaffold for Tendon Regeneration.
abstract: BACKGROUND
  The authors have developed a tendon hydrogel that may be injected into the site of tendon injury to improve speed and strength of repair. The aim of this study was to compare the biological and physical properties of fresh, hydrated tendon hydrogel with its reconstituted lyophilized counterpart with the goal of increasing clinical feasibility.
  
  
  METHODS
  Hydrogel was prepared from fresh human cadaveric flexor tendon. Fresh gel was compared to gel aliquots that were lyophilized and reconstituted with sterile deionized water. Scanning electron microscopy was used to examine the microarchitecture of gelated samples. Rat adipose-derived stem cells were seeded in hydrogel, and cell viability was assessed after 7 days. MTS colorimetric assay was used to evaluate both the effect of prolonged storage on gel and the ability of reconstituted lyophilized hydrogel to activate platelet-rich plasma. The viability and proliferation of luciferase-transfected adipose-derived stem cells embedded within hydrogel in vivo was assessed by a bioluminescence in vivo imaging system.
  
  
  RESULTS
  Reconstituted lyophilized hydrogel demonstrated similar handling properties compared to fresh gel. Adipose-derived stem cells remained viable 7 days after reseeding in both conditions. Lyophilized hydrogel retained its ability to activate platelet-rich plasma and retained 95 percent of its maximal proliferative capacity at 30 days. The in vivo imaging system demonstrated similar cell proliferation, with signal persisting through day 13.
  
  
  CONCLUSIONS
  Reconstitution of lyophilized hydrogel stimulated cell proliferation and platelet-rich plasma activation to a greater degree than did fresh hydrogel. Efficacy after prolonged storage was also shown to be superior. Therefore, this lyophilized formulation of tendon hydrogel may have wider clinical applicability.
authors.affiliation: Stanford and Palo Alto, Calif. From the Division of Plastic and Reconstructive Surgery, Stanford University Medical Center; and the Division of Plastic and Reconstructive Surgery, Veterans Affairs Palo Alto Health Care System.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Crowe
authors.forename: Arhana
authors.initials: A
authors.lastname: Chattopadhyay
authors.forename: Rory
authors.initials: R
authors.lastname: McGoldrick
authors.forename: Grace
authors.initials: G
authors.lastname: Chiou
authors.forename: Hung
authors.initials: H
authors.lastname: Pham
authors.forename: James
authors.initials: J
authors.lastname: Chang
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000502:physiology*; D002478:Cells, Cultured; D005612:Freeze Drying / Q000379:methods; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D015552:Injections, Intralesional; D008855:Microscopy, Electron, Scanning; D053657:Platelet-Rich Plasma / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration / Q000502:physiology*; D012680:Sensitivity and Specificity; D013708:Tendon Injuries / Q000628:therapy*; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate