Use of mesenchymal stem cells in a collagen matrix for achilles tendon repair

Abstract This investigation tested the hypothesis that delivering mesenchymal stem cell‐seeded implants to a tendon gap model results in significantly improved repair biomechanics. Cultured, autologous, marrowderived mesenchymal stem cells were suspended in a collagen gel delivery vehicle; the cell‐gel composite was subsequently contracted onto a pretensioned suture. The resulting tissue prosthesis was then implanted into a 1‐cm‐long gap defect in the rabbit Achilles tendon. Identical procedures were performed on the contralateral tendon, but only the suture material was implanted. The tendon‐implant constructs were evaluated 4, 8, and 12 weeks later by biomechanical and histological criteria. Significantly greater load‐related structural and material properties were seen at all time intervals in the mesenchymal stem cell‐treated tendons than in the contralateral, treated control repairs (p < 0.05), which contained suture alone with natural cell recruitment. The values were typically twice those for the control tissues at each time interval. Load‐related material properties for the treated tissues also increased significantly over time (p < 0.05). The treated tissues had a significantly larger cross‐sectional area (p < 0.05), and their collagen fibers appeared to be better aligned than those in the matched controls. The results indicate that delivering mesenchymal stem cell‐contracted, organized collagen implants to large tendon defects can significantly improve the biomechanics, structure, and probably the function of the tendon after injury.