BME PhD Dissertation Defense - Raphael Yao

2:00 pm on Thursday, December 6, 2012
4:00 pm on Thursday, December 6, 2012
44 Cummington St, Room 203
Joyce Wong (Advisor)
Michael Smith (Chair)
Elise Morgan
Louis Gerstenfeld
Elizabeth Bartolak-Suki

Title: "The Effects of Mechanical Stimulation on Controlling and Maintaining Marrow Stromal Cell Differentiation into Vascular Smooth Muscle Cells"

The construction of tissue engineered blood vessels (TEBV) is a promising solution for treating cardiovascular diseases. In order to attain the proper organization and mechanical properties found in native vessels, vascular smooth muscle cells (VSMC) are used as a crucial component of TEBVs. With the growing interest in stem cells, research has shown that marrow stromal cells (MSC) are a potential cell source for VSMCs due to their easier and less invasive isolation procedure, fast proliferation rates, and most importantly, the ability to differentiate into VSMCs. While current studies have provided evidence that mechanical stimulation can induce MSC alignment and differentiation into VSMCs, a definitive set of conditions must be determined in order to successfully control the differentiation.

The goal of this dissertation is to further define the effects of mechanical stimuli on the differentiation of MSCs. To do so, we created a uniaxial cell stretcher capable of delivering tunable mechanical conditions to cells seeded on a substrate. With this device, we applied a range of controlled stretch frequencies to MSCs and evaluated the final cell type for each condition using quantitative RT-PCR and immunocytochemistry. We found that at 10% strain, a 1 Hz frequency induced differentiation into the VSMC lineage as well as a highly aligned organization while a 0.1 Hz frequency induced osteogenesis. Using these results, we proceeded to investigate the potential of MSC transdifferentiation through mechanical stimulation by applying the two distinct lineage-inducing conditions sequentially and evaluating the final cell type. We found that while mechanical stimulation was capable of inducing MSC transdifferentiation, it could only proceed in the direction toward the VSMC phenotype under the applied conditions.

Our findings revealed the potential use of mechanical stimulation as a tool for controlling MSC differentiation. We

expect the methods and specific mechanical conditioning developed in this project to become a useful and novel approach to not only control, but also maintain the differentiation of MSCs into VSMCs for TEBV construction.