Bone marrow-derived mesenchymal stem cells obtained during arthroscopic rotator cuff repair surgery show potential for tendon cell differentiation after treatment with insulin.

PURPOSE: The purpose of this study was to determine whether a one-time physiologic dose of insulin when compared with the growth factors insulin-like growth factor 1, β-fibroblastic growth factor, and growth differentiation factor 5 is capable of differentiating bone marrow-derived mesenchymal stem cells (MSCs) into tendon.

METHODS: Eleven patients undergoing arthroscopic rotator cuff repair consented to undergo aspiration of bone marrow. A dose-response curve was calculated to determine the optimal dose of insulin needed to differentiate MSCs into tendon. After purification of bone marrow in the operating room, MSCs were exposed to either insulin or tendon-inducing growth factors or were left untreated to serve as a control. The potential for MSCs in each of these groups to differentiate into tendon was evaluated with a multistep process that included determination of the genetic upregulation for tendon-specific proteins, confirmation that the levels of these proteins were actually increased, staining of the MSCs with antibodies for these proteins to ensure that they were expressed on the cell surface, and finally, evaluation of cell morphology to verify the MSCs' tendon-like appearance.

RESULTS: MSCs treated with insulin showed increased gene expression of tendon-specific markers (P < .05), increased content of tendon-specific proteins (P < .05), and increased receptors on the cell surface (P < .05) compared with control cells. Histologic analysis showed a tendon-like appearance compared with the control cells.

CONCLUSIONS: Bone marrow-derived MSCs treated with a single physiologic dose of insulin differentiated into cells with characteristics consistent with tendon.

CLINICAL RELEVANCE: The potential for MSCs to differentiate into tendon after a 1-time dose of insulin may assist in developing practical biologic options for augmentation of rotator cuff repairs.