A Novel Biomaterial Enables Chemotactic Study of Motile Central Nervous System-derived Tumor Cells

Abstract

The local cell microenvironment plays an important role in maintaining the dynamics of the extracellular matrix (ECM) and the cell-ECM relationship. ECM is a complex network of macromolecules with distinct mechanical and biochemical characteristics [1]. The multifaceted interactions that occur between cells and the ECM are crucial to the regulation of processes that maintain homeostasis. These mechanisms are often deregulated during cancer onset and progression, which cause the ECM to become highly disorganized, alter the cell-matrix interactions, and promote increased hypervascularity and metastasis as these components are indicative of cancer progression. Medulloblastoma (MB) is one of the most common, malignant pediatric brain tumors worldwide [61]. It is characterized by high tumor invasiveness to extraneural tissues and reoccurrence in the cerebellum after total resection [2]. In the case of MBs, the migration of cells from primary tumors to other locations, within the brain or otherwise, has been one of the most clinically challenging and poorly understood processes [3]. Thus, understanding the mechanisms that regulate MB dispersal within the central nervous system (CNS) and beyond is especially important. The migration of brain cancer cells is highly complex, involving significant interactions with ECM, and chemoattractants that either diffuse from blood vessels and/or are produced by neighboring cells [4, 5]. Understanding the cell-ECM relationship provides insight into their interactions and assists in the study of endogenous cell migratory behaviors. ! %! In order to examine the chemotaxis of MB-derived cells, this study first examined how migration along distinct ECM affected cell migratory responses to the well-studied protein, Epidermal Growth Factor (EGF). MB phenotype and motility were examined within 7 different types of ECM Poly-D-Lysine (PDL), Matrigel, Laminin, Collagen-1, Fibronectin, a 10% blend of Laminin-Collagen1, a 20% blend of Laminin-Collagen 1 and a cellulose derived synthetic hydrogel, CMC. The average changes in cell morphology, over time in 2D and 3D are quantified using the NIH software, ImageJ, to reveal that CMC allows for a cell-ECM relationship typically believed to present in tumors when compared to other ECMs tested. The interaction of the cells with the CMC hydrogels exhibited amoeboidal morphology that is believed to indicate the readiness of a cell to migrate within a given environment. Investigation of CMC hydrogels revealed a polysaccharide that enables MB chemotactic study towards EGF with minimal haptotaxis, i.e. migration induced along the ECM alone .CMC gels used as ECM thereby facilitate unique, mechanistic study of MB chemotaxis because the hydrogel itself minimizes integrin interactions between cells and the ECM. This phenomenon was observed via immunocytochemistry staining performed on the Daoy cells seeded onto CMCs. Integrin �v�3 expression was not visualized upon CMC hydrogels when compared to C-1, MGL, and LAM coatings. This data in this study illustrates a new application of biomaterials as in vitro test systems with which to mechanistically examine the migratory responses of cells associated with numerous central nervous system (CNS) disorders, including cancer, �����������, multiple sclerosis (MS) and others. Such investigation can uniquely contribute to the generation of pharmacological compounds and migration-targeted therapies to prevent tumor dispersal in the brain and metastasis.