Each year in the United States, over 1 million bone reconstruction procedures are performed. Electrical stimulation (ES) has been shown to exhibit profound effects on bone repair and regeneration in clinical applications. However, current ES devices present many drawbacks including the inefficiency of generated electrical fields (for external ES devices), the bulky size and toxic materials used in electrical stimulators, and the non-degradability of implanted ES devices. Piezoelectric materials, which can generate electric charge during deformation and vice versa, can be employed to create self-powered electrical stimulators that can effectively to stimulate bone repair and regeneration. Specifically, piezoelectric charges generated on the surface of the piezoelectric materials have proven to effectively stimulate stem cell proliferation, migration, osteogenic differentiation and remodeling both in vitro and in vivo. However, the underlying molecular mechanism responsible for these observations is still unclear. The preliminary results demonstrated that surface charge on a biomaterial could alter the calcium signaling pathways, which could possess intrinsic osteoinductivity by stimulating the production and secretion of cell-based osteoinductive protein growth factor (BMP-2). The hypothesis of this grant application is that surface charge generated on piezoelectric materials will induce enhanced Ca2+ oscillation and/or ECM protein adsorption, and such a change may trigger the stem cell osteo-differentiation and/or cytokine-based inductive autocrine and paracrine loops. The main goal of this application is to investigate the fundamental molecular mechanism of how the surface charge of piezoelectric materials can positively influence the degree of healing and promote bone tissue regeneration.
Three specific aims are proposed to test the hypothesis of our proposal.
In Aim 1, we will design, fabricate, and characterize piezoelectric materials for the study of osteogenic signal mechanisms.
In Aim 2, we will study how Ca2+ signaling mechanisms and/or ECM deposition in respond to the piezoelectric charges generated on the piezoelectric materials.
In Aim 3, using microarrays, we will examine the expression profile of a variety of genes during osteogenic differentiation of the seeded mesenchymal stem cells (MSC) on the piezoelectric materials. The data from this project will provide the necessary information to explore further the nature of piezoelectric surface charge for bone repair and regeneration applications. The first milestone achievable through this proposal is the development of a piezoelectric scaffold and the setup for studying the osteogenic signaling mechanisms and the related characterizations of the scaffold itself. The second achievable milestone is the evaluation of the role of Ca2+ signaling mechanisms as well as ECM adsorption in response to the surface charges generated on the piezoelectric materials. The third milestone is the assessment of the expression profiles of a variety of genes during osteogenic differentiation of MSCs on the piezoelectric scaffold.
People of all ages can suffer from bone fractures and breaks, sometimes too severe to heal naturally. Certain biomaterials that can generate electric charge have been shown to exhibit profound effects on bone repair and regeneration. By combining the expertise in cell biology, biochemistry, bioengineering, and material sciences, we will investigate the detailed mechanism of how the surface electrical charges have positively influence the degree of healing and promote bone tissue regeneration.