BME Seminar Series: Molly Baumann, Huiming Dong, & Kevin Blum

Huiming Dong: 

"In Vivo Aortic Magnetic Resonance Elastography: Development and Clinical Potential"

Using maximum diameter of an abdominal aortic aneurysm (AAA) alone for management can lead to delayed interventions or unnecessary urgent repairs. AAA stiffness plays an important role in its expansion and rupture. In this study, in vivo aortic magnetic resonance elastography (MRE) was developed to spatially measure AAA stiffness. The aim of this presentation is to demonstrate the technical development, validation as well as application in AAA patients.

Kevin Blum: 

"Effects of Tamoxifen and Gender on Murine Tissue Engineered Vascular Graft Development"

Tissue engineering, and its goal of developing functional tissues from implanted biomaterials, requires detailed understanding of both the physical characteristics of implanted materials as well as the biological host response.  The host response is a complex process involving many mechanisms that are not fully understood. Utilizing a common tamoxifen-inducible genetic knock-out mouse model, we observed unexpected outcomes after implantation of tissue engineered vascular grafts (TEVGs) only in the presence of tamoxifen. We therefore sought to study this observed phenomenon in further detail. Male and female C57BL/6 mice were fed a control chow or a chow containing tamoxifen and implanted with infrarenal inferior vena cava interposition TEVGs and followed for two weeks. We observed weight loss in the tamoxifen chow group, and to account for this potential confounder, completed an additional group of female mice treated with intraperitoneal injections of tamoxifen. Explanted TEVGs revealed differences between the male and female response to the implant, including higher cellular infiltration in the female mice and a much higher rate of foreign body giant cell formation, despite similar levels of macrophage infiltration between the genders. Tamoxifen treatment in females led to increased occlusion and decreased cellular infiltration, extracellular matrix deposition, and foreign body giant cell formation. Results of this study indicate that tamoxifen is a critical confounder for studies involving tissue engineered vascular grafts. Careful study design and evaluation of the interplay between biomaterials and host biology is crucial for the evaluation of tissue engineering mechanisms and critical evaluation of tissue engineering products.

Molly Baumann:

"Fractional CO2 Laser Ablation of Porcine Burn Scars Post-Grafting"

Fractional CO₂ lasers have been increasingly used in clinical settings to improve scarring following burn injury despite a lack of well-defined settings for use.  The goal of this study was to examine the role of ablation depth on scar outcomes in a highly-controlled porcine model for burn scars-post grafting. Full-thickness burn wounds were created on the dorsum of red Duroc pigs with the eschar excised and grafted with a split-thickness autograft.  After four weeks of healing, sites were treated with either 20, 70, or 150 mJ pulse energy from a fractional CO₂ laser or left untreated as a control. Sites were treated every four weeks for three total sessions. Scar properties (area, color, biomechanics) were not significantly altered by laser therapy at any of the laser energies tested versus controls. Average scar roughness was improved by laser therapy in a dose dependent manner with scars treated with 150 mJ of energy having the smoothest surface. Overall, the study suggests that there is little difference in outcomes as a function of laser energy, thus highlighting the need for additional clinical investigation of laser therapy efficacy with non-treated controls and objective measures of outcome.