title: A comparison of tenocytes and mesenchymal stem cells for use in flexor tendon tissue engineering.
abstract: OBJECTIVE
  Tissue-engineered tendon grafts will meet an important clinical need. To engineer tendons, we used acellularized allogeneic tendon as scaffold material. To determine the ideal cell type to seed the scaffolds, we studied in vitro characteristics of epitenon tenocytes, tendon sheath fibroblasts, bone marrow-derived mesenchymal stem cells (BMSCs), and adipoderived mesenchymal stem cells (ASCs). Subsequently, we implanted reseeded acellularized tendons in vivo as flexor tendon grafts.
  
  
  METHODS
  Tenocytes, sheath fibroblasts, BMSCs, and ASCs were obtained from adult rabbits. For all cell lines, collagen 1, 2, and 3 immunocytochemistry was performed, and proliferation was assessed by hemacytometry and senescence by beta-galactosidase staining. Flexor tendons were acellularized after harvest. Tendons were assessed by histology after in vitro reseeding with each of the cell types after 1, 4, and 8 weeks. Finally, reseeded tendons and controls were implanted in a flexor profundus tendon defect. After 6 weeks, the reseeded tendons were harvested and assessed by histology. Statistical analysis for cell proliferation was performed using analysis of variance and t-tests with Bonferroni correction.
  
  
  RESULTS
  All cell types had similar collagen expression. Cell proliferation was higher in ASCs in late passage compared with early passage and in ASCs compared with epitenon tenocytes at late passage. The other cell types were similar in growth characteristics. No senescence was detected. In vitro assessment of reseeded constructs showed the presence of cells on the construct surface. In vivo assessment after implantation showed viable cells seen within the tendon architecture in all cell types.
  
  
  CONCLUSIONS
  This study suggests that the four cell types may be successfully used to engineer tendons. Adipoderived mesenchymal stem cells proliferate faster in cell culture, but the cell types were similar in other respects. All could be used to successfully repopulate acellularized tendon in vivo as flexor tendon grafts.
authors.affiliation: Division of Plastic Surgery, Stanford University Medical Center, Palo Alto, CA 94304, USA.
authors.forename: Gil S
authors.initials: GS
authors.lastname: Kryger
authors.forename: Alphonsus K S
authors.initials: AK
authors.lastname: Chong
authors.forename: Melinda
authors.initials: M
authors.lastname: Costa
authors.forename: Hung
authors.initials: H
authors.lastname: Pham
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Bates
authors.forename: James
authors.initials: J
authors.lastname: Chang
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology; D007150:Immunohistochemistry; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D023421:Models, Animal; D011817:Rabbits; D013708:Tendon Injuries / Q000601:surgery*; D013710:Tendons / Q000166:cytology* / Q000637:transplantation; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D003094:Collagen