Survivorship of implanted bone marrow-derived mesenchymal stem cells in acute rotator cuff tear.

BACKGROUND: This study examined whether a mesenchymal stem cells (MSCs)-seeded 3-dimensional construct into a tendon defect would promote cellular differentiation and matrix healing.
MATERIALS AND METHODS: Bone marrow was harvested from the iliac crests of 2 male New Zealand White rabbits. The MSCs were cultured, and an open-cell polylactic acid (OPLA) scaffold was encapsulated with these cells. The injury model was a 5-mm × 5-mm-sized full-thickness window defect in the central part of each rotator cuff tendon. The defects on the right side were grafted with the autologous MSCs-seeded OPLA scaffold implant and a biodegradable suture. The same procedure was done on the left side, except a cell-free OPLA scaffold was used. Three rabbits were used as controls, without treatment of the tendon defect. Samples were harvested at 2, 4, and 6 weeks for analysis, which included evaluation of gross morphology, fluorescent analysis, histologic assessment, and immunohistochemistry studies.
RESULTS: The expression of immunohistochemical stainings for collagen I was higher in the scaffold with MSCs than in the scaffold without MSCs. The expression of collagen II, however, was not different between the scaffolds with and without MSCs.
CONCLUSIONS: Even though this is a short-term study, we demonstrated that many MSCs in the scaffold survived after implantation in an acute rabbit rotator cuff defect. Furthermore, the generation of type I collagen increased more in the scaffold with MSCs than it did in the scaffold without MSCs. MSCs are thought to promote tendon healing by producing type I collagen when they are applied at the tendon defect.