Cell culture systems are indispensable tools that are used in a wide range of basic and clinical in vitro research studies. Cell-based assays have also been an important pillar of the drug discovery process. Today they could provide a simple, fast, and cost-effective tool for the development of new and personalized drug or cell therapies to support muscle rehabilitation programs in patients with movement disorders. Traditionally, the majority of cell-based assays use two-dimensional (2D) monolayer cells cultured on flat and rigid substrates. Although 2D cell culture is a valuable method for cell-based studies, its limitations have been increasingly recognized. Since cells in a tissue environment are surrounded by other cells and connective tissue structured in a three-dimensional (3D) fashion, 2D cell cultures do not adequately recapitulate the natural 3D organization of tissues and organs. Thus, 3D cell culture systems represent more accurately the actual microenvironment where cells reside in tissues. Additional dimensionality not only influences the spatial organization of the cells and their surface receptors engaged in interactions with surrounding cells and connective tissue, but it also induces physical constraints to cells. These aspects affect the signal transduction from the outside to the inside of cells, and ultimately influence gene expression and cellular behavior. In this proposed work, we aim to leverage the versatility of 3D printing to define optimal in vitro 3D environments that can serve as tissue mimetics for different type of cells.
3D printing is the process of creating a three-dimensional (3D) model by laying down successive layers of material extruded from a syringe layer-by-layer in a computer controlled fashion with control over parameters such as strut spacing and angle of orientation between successive layers. Printing materials or “inks” can be a variety of substances including plastics, polymers, metal alloys, hydrogels and other biomaterials. When the ink being used includes or supports living cells, the 3D printing is called 3D bioprinting. It provides the unique advantage to precisely pattern a variety of both cells and biomaterials in three spatial dimensions in a way that more closely mimics natural tissue structure compared to traditional 2D culture. Our close collaborator, Dr. Ramille Shah at the Simpson Querrey Institute for BioNanotechnology, Northwestern University has previously developed a range of biomaterials for tissue engineering applications, most notably cell-laden hydrogels and electrically conductive and neurogenic graphene-PLGA composites. Our two laboratories are setting up a collaboration to investigate muscle stem cells growth and differentiation within 3D-printed biocompatible structures.
We expect these assays to open new possibilities to investigate the cellular and molecular reasons why cerebral palsy and other movement disorders like stroke and spinal cord injury are associated with muscle contractures and unequal muscle tissue development. They will also provide indispensable in vitro tissue assays to develop new diagnostic and therapeutic biomarkers for drug development and testing, in cerebral palsy and other muscle conditions. Also, it is not impossible to imagine that engineered muscle tissue could be used in the future to support surgical procedures and their outcomes after muscle-tendon repair in patients with cerebral palsy and other muscle conditions.