Labeling and tracing of bone marrow mesenchymal stem cells for tendon-to-bone tunnel healing

Abstract

Purpose: To investigate the effects of bone marrow mesenchymal stem cells (BMSCs) on tendon-to-bone tunnel healing and provide experimental evidence for labeling and tracing of stem cells.

Methods: Rat BMSCs were harvested using the adherence separation technique and labeled by super paramagnetic iron oxide (SPIO) and 1,1-Dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate (Dil) particles. Thirty-nine male Sprague-Dawley (SD) rats aged 8 weeks were randomly divided into two groups: experimental (n = 21) and control (n = 18). Rats from the experimental group were injected with SPIO- and Dil-labeled BMSCs and Pluronic F-127, and rats from the control group were only injected with Pluronic F-127. At 2, 4, and 8 weeks after surgery, biomechanical analysis was performed to evaluate tendon-to-bone tunnel healing. The transplanted BMSCs were observed by fluorescence microscope at 2, 4, and 8 weeks after surgery and traced by magnetic resonance (MR) imaging at 0, 3, and 7 days after surgery.

Results: BMSCs were labeled effectively by SPIO and Dil particles. At 2, 4, and 8 weeks after surgery, Dil-labeled cells were observed at tendon-bone interface by fluorescence microscope. In the experimental group, no obvious signal changes of tendon-bone interface were observed by MR imaging. The maximum biomechanical pull-out strength was not statistically different between experimental and control groups at 2 weeks, but significantly higher in the experimental group at 4 and 8 weeks after surgery (P < 0.05).

Conclusion: The present study indicated that the transplanted BMSCs could promote tendon-to-bone tunnel healing at 4-8 weeks postoperatively. Dil- and SPIO-labeled transplanted BMSCs distributed at the tendon-bone interface and might play a role in promoting tendon-to-bone tunnel healing, which may be translated into practical cytotherapy for patients those who need earlier rehabilitation for ligament reconstruction surgery in clinic.