Integrating Biomaterials and Biophotonics to Assess How ECM Mechanics Regulate Cell Function in 3-D

University Of California-Irvine, Irvine CA

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 0805164 PI: Putnam, Andrew ORG: University of California-Irvine Title: Integrating Biomaterials and Biophotonics to Assess How ECM Mechanics Regulate Cell Function in 3-D INTELLECTUAL MERIT: The extracellular matrix (ECM) provides both chemical and mechanical cues to cells, and an improved understanding of how these cues govern cell function in 3-D is critically important to design biomimetic materials as morphogenetic guides for tissue engineering. In this proposal the PI plans to utilize a unique biosynthetic hybrid hydrogel based on poly(ethylene glycol) and fibrinogen (PEG-fibrinogen) to explicitly test the hypothesis that local substrate mechanical properties influence cell phenotype in 3-D. This hypothesis will be addressed using vascular smooth muscle cells (SMCs) as a physiologically relevant model cell system, based not only on the PI's documented experience with this cell type but also these cells' well-known ability to respond to static and dynamic mechanical stresses both in vitro and in vivo. Preliminary data demonstrate that PEG-fibrinogen hydrogels support SMC adhesion, spreading, viability, and the expression of differentiation markers in 3-D over relatively long culture periods. This material also provides the means to predictably tune bulk mechanical properties independently from adhesion ligand density and proteolytic sensitivity, something which cannot be achieved using native biopolymers (e.g., collagen, fibrin). The PI also proposes to develop novel methodology to measure the local mechanical properties of PEG-fibrinogen gels, leveraging the co-PI's expertise with optical tweezers to investigate mechanotransduction mechanisms to address a major unanswered question in the area of cell-material interactions. The following three objectives constitute the proposed study: (1) Engineer, characterize, and develop novel biosynthetic hybrid hydrogels using PEG-fibrinogen and demonstrate that their bulk mechanical properties can be predictably manipulated while holding the concentration of fibrinogen constant. (2) Interrogate the local elastic and viscoelastic properties of the PEG-fibrinogen gels, comparing the measured values to the bulk measurements in the previous objective. (3) Assess the impact of gel mechanical properties on the phenotypic switch of SMCs (synthetic to contractile) cultured in 3-D in the context of this PEG-fibrinogen ECM analog, and quantify how the bulk and local mechanical properties of these cell-material constructs change over time. BROADER IMPACTS: Completion of the objectives of this proposal requires an integration of emerging principles from biomaterials, biophotonics, and cell and molecular biology. It will contribute to the near-term research goal of developing material systems and methods to address fundamental questions regarding ECM chemistry and mechanics. Such systems and methods will have a much broader impact defining biomechanical design parameters for biomaterials useful in tissue engineering, and allow fundamental mechanics questions relevant for developmental biology, cardiovascular physiology, wound healing, and tumorigenesis to be addressed in future proposals. To facilitate dissemination of the methods developed here they will be integrated into the Laser Microbeam and Medical Program, an NIH Biomedical Technology Resource Center at the Beckman Laser Institute on the UCI campus. In addition to training graduate students on the project, the PIs have established a working relationship with the California Alliance for Minority Participation (CAMP) and the Mathematics, Engineering, and Science Achievement (MESA) programs on the UCI campus to involve minority undergraduate and high school students in the program.