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.