Ray Vanderby

Mesenchymal Stem Cell Therapy on Tendon/Ligament Healing

A normal healing response after ligament and tendon rupture results in scar formation and an inferior tissue that fails to emulate its original structure, composition, and function. More regenerative healing (closer to the original) can be obtained through early suppression of inflammatory cells and associated cytokines. Examination of the immune mediated response of mesenchymal stem/stromal cells (MSCs) during healing indicates that MSCs reprogram macrophages from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype. Based on these studies our objective was to treat ligament and tendon injuries with MSCs in order to modulate their inflammatory response. Our initial studies using allogeneic cells demonstrated an in vivo dose dependency of MSCs on ligament healing. Medial collateral ligaments (MCLs) treated with 1 × 106 (low dose) MSCs exhibited less inflammation and a reduced number of M1 macrophages compared to ligaments treated with 4 × 106 (high dose) MSCs. Strength of ligament was also improved with the low dose treatment. We then examined the in vivo effects of MSCs that had been preconditioned to be more anti-inflammatory. Treatment with these preconditioned MSCs was compared with normally processed (unconditioned) MSCs using the rat Achilles tendon and MCL healing models. Pre-conditioned MSCs significantly reduced inflammation by increasing the M2 macrophages and decreasing the M1 macrophages. Most importantly, treatment with pre-conditioned MSCs improved tissue strength to levels comparable to intact tissue. Overall, pre-conditioned MSC-treatment out-performed unconditioned MSCs to improve ligament and tendon healing by stimulating a more robust, paracrine-mediated immunosuppressive response.

Addition of Mineral-Coated Microparticles to Soluble Interleukin-1 Receptor Antagonist Injected Subcutaneously Improves and Extends Systemic Interleukin-1 Inhibition

IL‐1 receptor antagonist (IL‐1Ra) inhibits the pro‐inflammatory activity of IL‐1β. However, its short in vivo half‐life and high dose required to inhibit IL‐1β may limit its use in all but a few clinical scenarios. This study examines whether the addition of mineral‐coated microparticles (MPs) to a solution of IL‐1Ra extends its ability to inhibit IL‐1β activity when administered as a subcutaneous injection. MPs efficiently bind proteins in solution and provide sustained protein delivery. In vitro assays demonstrate that IL‐1Ra released from MPs is biologically active and inhibits IL‐1β activity. When MPs are added to an IL‐1Ra solution and injected subcutaneously into a murine model, serum IL‐1Ra is elevated for a longer duration compared to the treatment with the IL‐1Ra solution alone. Further, the addition of MPs to the IL‐1Ra solution results in the inhibition of IL‐1β activity for 7 days. A novel MP formulation that layered IL‐1Ra throughout the coating extends inhibition of IL‐1β activity in vivo for at least 14 days, suggesting potential for long‐term IL‐1β inhibition. Overall addition of MPs to an IL‐1Ra solution injected subcutaneously prolongs the duration of elevated serum concentration of IL‐1Ra and extends its ability to inhibit IL‐1β activity.