Mesenchymal Stem Cell Enrichment and Differentiation through Functionalized Biomaterials

Abstract

The use of mesenchymal stem cells (MSCs) for tissue engineering and cell-based therapies has great potential. MSCs are an adult stem cell population capable of undergoing multilineage differentiation into several key tissue types including bone, fat, and cartilage. However, despite key research and clinical advances, these therapies are still largely in the developmental phases. MSCs are typically isolated from the bone marrow using a multi-step process involving density centrifugation and adherence of the mononuclear fraction of cells to tissue culture polystyrene (TCPS). The majority of MSC-based approaches require in vitro cell expansion in monolayer to produce the cell numbers necessary for subsequent implantation. Recently, it has been suggested that expansion may cause significant changes to the MSC phenotype. In an effort to simplify the process of MSC isolation and use for such applications, our goal was to develop a single-step 3D culture system for the capture, culture, and differentiation of MSCs. To this end, we focused on the adhesion of MSCs to an underlying substrate, specifically how adhesion could facilitate one-step isolation. We showed that there are distinct changes in MSC adhesion during differentiation that can be used to separate populations of differentiating cells to decrease the heterogeneity of the cell population for implantation. By tethering proteins typically found in the MSC extracellular matrix onto the surface of polymer scaffolds, we were able to increase the specific adhesion of MSCs over TCPS, the current gold standard. Additionally, surface functionalization could be used as a method to drive rapid and directed differentiation of MSCs. Upon exposure to the heterogeneous population of the bone marrow, cells captured on the functionalized material surface had a similar phenotypic signature to MSC controls. Using 3D printing technology, our polymer scaffolds were translated into a highly controlled 3D environment that supports MSC adhesion, proliferation, and differentiation. The techniques presented here represent the key criteria for the development of a one-step culture system for MSC isolation and subsequent implantation. This work highlights the feasibility of functionalized biomaterials as a means to simplify the current use of MSCs for regenerative medicine.