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BACKGROUND The future in flexor tendon surgery involves tissue engineering approaches directed toward increasing early repair strength to accelerate tendon healing and to allow for earlier onset of rehabilitation. Previous work has shown that pluripotential mesenchymal stem cells may be successfully delivered to a tendon repair site using a suture carrier. The current work describes the use of Myostatin (GDF-8) to help guide these delivered pluripotential stem cells to differentiate down a tenocyte lineage to potentially maximize the reparative effects of these cells at the tendon repair site. METHODS Primary rat bone marrow mesenchymal stem cells isolated from the long bones of male Sprague-Dawley rats were treated with 500 ng/ml myostatin for 24 h, 48 h, and 72 h. Collagen 1 A, scleraxis (Scx), and tenomodulin (Tnmd) expression, indicative of tenogenesis, was analyzed using real time PCR and immunohistochemistry staining. A migration assay was performed to assess the functional activity of BMSCs after they were treated with myostatin. RESULTS Compared to the control cells (without treatment), the cells treated with 500 ng/ml myostatin for 72 h exhibited higher expression of Col 1A, Scx, and Tnmd. The mRNA expression of Col1A, Scx, Tnmd increased 15.3, 13 and 7 times respectively. Immunohistochemistry staining showed Scx and Tnmd were expressed in the cellular cytoplasm. In response to myostatin, the cells also showed a tendency to proliferate and migrate more than the control cells. CONCLUSIONS Myostatin (GDF-8) has the ability to increase rat bone marrow mesenchymal stem cell growth and differentiation toward a tenocyte lineage. This information could be useful for future studies regarding tendon repair.