Subacromial bursa increases the failure force in a mouse model of supraspinatus detachment and repair.

Overview

abstract

BACKGROUND: It has been shown that subacromial bursa (SAB) harbors connective tissue progenitor cells (CTPCs). The purpose of this study was to evaluate the effects of implantation of subacromial bursa-derived cells (SBCs) suspended in a fibrin sealant bead and implantation of SAB tissue at rotator cuff repair site on biomechanical properties of the repair in a mouse (C57Bl/6) model of supraspinatus tendon (ST) detachment and repair. METHODS: Part One: Murine SAB tissue was harvested and cultured. Viability of SBCs suspended in 10μl of fibrin sealant beads was confirmed in vitro and in vivo. Eighty mice underwent right ST detachment and repair augmented with either fibrin sealant bead (control group) or fibrin sealant bead with 100,000 SBCs (study group) applied at the repair site. Part Two: 120 mice underwent right ST detachment and repair and were randomized equally into 4 groups: 1) tissue group received a piece of freshly harvested SA tissue; 2) cell group received SBCs suspended in fibrin sealant bead; 3) fibrin sealant group received plain fibrin sealant bead without cells; and 4) control group received nothing at ST repair site. An equal number of mice in each group were sacrificed at 2- and 4-weeks. Specimens underwent biomechanical testing to evaluate failure force (Part One and Two) and histologic analysis of the repair site (Part One only). RESULTS: Part One: The mean failure force in the study group was statistically higher than controls at 2- and 4-weeks (3.25 ± 1.03 N vs 2.43 ± 0.56 N, p = 0.01 and 4.08 ± 0.99 N vs 3.02 ± 0.8 N, p = 0.004, respectively). Mean cell density of the ST at the repair site was significantly lower in the study group at 2 weeks than in controls (18292.13 ± 1706.41 vs 29501.90 ± 3627.49, p = 0.001). Study group specimens had lower proteoglycan contents than controls but this difference was not statistically significant. Part Two: There was no difference in failure force between cell and tissue groups at 2- and 4-week time points (p = 0.994 and p =0.603, respectively). There was no difference in failure force between fibrin sealant bead and control groups at 2- and 4-week time points (p = 0.978 and p =0.752, respectively). CONCLUSION: This study shows that the application of SBCs and SAB tissue at the rotator cuff repair site increases the strength of repair in a murine model of rotator cuff detachment and repair.