Mesenchymal stem cells (MSCs) have tremendous therapeutic potential as they are capable of differentiating into various mesenchymal lineages such as bone, adipose, and cartilage. However, MSCs represent only a fraction of the cells that are found in the bone marrow and lack unique identifying markers, proving them difficult to isolate precisely. There are several limitations to traditional plastic adherence, including potentially harmful interactions between MSCs and the other cell types within the bone marrow, possible loss of late-adhering MSCs, and the undesired expansion of non-MSC adherent cells found in the bone marrow. The goal of this proposal is two-fold. First to overcome the limitations of traditional plastic adherence by designing a unique material with tuned mechanical and surface properties to strongly and selectively adhere MSCs in a heterogeneous population. Second, to culture and differentiate the enriched captured MSC population on the same material.
The completed work focused on the development of a surface-modified material for the attachment and differentiation of MSCs. To develop our material, we first investigated the role of stiffness on MSC adhesion and morphology. We found that MSC adhesion was increased with increasing stiffness, and continued with the optimized mechanical properties in our investigation of MSC ECM protein tethering. The protein fibronectin was tethered to the material surface and we were able to show that the resulting MSC adhesion and morphology mimicked that of the current standard, tissue culture polystyrene. Using the material that we optimized for mechanical properties and protein modification we were able to investigate two key parameters. First, we showed that MSCs seeded onto our scaffolds were able to successfully differentiate into the three major cell types derived from the mesenchyme: osteoblasts, chondrocytes, and adipocytes. Second, we were able to investigate the adhesion and proliferation of MSCs seeded onto our material in a dynamic environment. Here, we were able to show that MSCs proliferated at points of modification on the material surface in response to the dynamic culture environment. Overall, the completed work resulted in increased knowledge of material properties, modification techniques, and the influence of these properties on MSC adhesion, proliferation, and function.
