Encapsulation of Equine Mesenchymal Stem Cells in Injectable PEG-Fibrinogen Microspheres for Local Cell Delivery

Abstract

Musculoskeletal injuries are a predominant cause of morbidity and lameness in horses. These include fractures, osteoarthritis, chronic wounds, and tendon and ligament injuries. Due to their regenerative potential and immunomodulatory properties, bone marrow-derived mesenchymal stem cells (bm-MSCs) are considered an alternative treatment option for these types of injuries. However, studies have shown that cell delivery through direct injection leads to low cell viability and retention rates. The use of hydrogels as cell carriers has been studied as an alternative delivery mechanism to provide mechanical protection to the cells and hence improve cell viability after injection. A well-studied material is poly(ethylene glycol)-fibrinogen (PF), which has been used to encapsulate other cell types in microspheres that led to improved cell retention after subcutaneous injection. The purpose of this study was to demonstrate the ability to rapidly encapsulate equine bm-MSC in PF microspheres, and to evaluate the effect of encapsulation on cell viability, phenotype, and ability to differentiate into mesodermal-derived lineages. In addition, encapsulated bm-MSC were exposed to shear through different needle gauges to provide a preliminary assessment of their potential use for local injection. In this project, equine bone marrow-derived mesenchymal stem cells (bm-MSCs) were isolated, and a protocol for their rapid and scalable encapsulation in PEG-Fibrinogen was established. Cell viability, proliferation, tri-lineage differentiation, and multipotency cell marker expression were measured pre- and post-encapsulation. Based on viability and proliferation results this study showed that encapsulated bm-MSCs are a potential alternative for use in large animal cell therapy. In general, the results from this study provide insight on the application of encapsulated MSCs for cell therapy.