Microengineered Platforms for High-throughput Characterization of Cellular Microenvironments

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Osteoarthritis is the most common form of arthritis, affecting 1 out of every 10 people in Canada. The total cost of arthritis is estimated at $33 billion dollars per year. Similarly, millions of patients in Canada undergo procedures to correct bone deformities each year. Tissue engineering seeks to provide an alternate therapeutic approach using stem cells. Mesenchymal stem cells derived from bone marrow retain a multi-lineage potential to differentiate to fat cells, heart muscle cells, bone cells, and cartilage cells. The physical properties of local microenvironments will play an important role in the differentiation of mesenchymal stem cell. A number of studies have been aimed at combining stem cells with biomaterials for cartilage and bone regeneration, but to date, no study has systematically examined the combinatorial factors to control the physical properties for stem cell differentiation in a 3-D microenvironment. In the 3-D cellular microenvironment, cells interact with their surroundings by processing various chemical and physical signals. To control cellular microenvironments for stem cells, hydrogels have attracted great interests due to high water content, biocompatibility, and mechanical properties resembling natural tissues. However, various parameters of hydrogels are associated with controlling stem cell fate; the optimization of the parameters is essential. Therefore, a high-throughput screening technology to test many parameters in one experiment will facilitate the systematic examination and the optimization of cellular microenvironments generated by hydrogels. High-throughput screening technology is a method of using robotic liquid handling devices to quickly fabricate microarrays of chemical, genetic, and pharmacological materials and conduct tests in a high-throughput manner. In this research program, we adopt this technology to develop a hydrogel microarray with hundreds of micrometer-sized functional hydrogel spots (diameter: ~500µm; thickness: ~100µm) printed on a standard microscope slide. We will use alginate hydrogels that can be polymerized by ultra violet light. We will test 27 combinations of alginate hydrogels with three different parameters and three different conditions of each parameter that control physical properties. We will characterize the physical properties, such as microstructure, stiffness, and adhesion, using advanced characterization techniques such as atomic force microscopy and scanning electron microscopy. The developed alginate microarray will be used to optimize the effects of physical properties on mesenchymal stem cell differentiation. Although the molecular mechanisms associated with the biological responses have yet to be clarified, such technology may be widely applicable in cell-microenvironment research. Also, the physical properties identified in this program could be used as design parameters for engineering new biomaterials and microenvironments for tissue regeneration. In this program, we propose to engineer and apply high-throughput screening technology for the identification of cell-microenvironment interactions that increase stem cell differentiation into the bone and cartilage. The results of this research will have high potential to positively affect the large number of patients that undergo procedures to repair bone and cartilage each year. Thus, the orthopedic community in Canada would benefit from the new treatment techniques composed of osteogenic and chondrogenic biomaterials that not only support, but also induce tissue formation. The developed platforms will also be applicable to numerous tissue regeneration applications, such as cardiovascular and nerve tissues and beneficial for biomaterials and tissue engineering research in Canada.