Impact of Adipose-Derived Stem Cells on Aortic Tensile Strength in an Abdominal Aortic Aneurysm Model

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INTRODUCTION: Abdominal aortic aneurysm (AAA) is a highly morbid condition with treatment currently limited to operative interventions. Prior literature has demonstrated the ability of mesenchymal stem cells (MSCs) in attenuating AAA formation. We aim to demonstrate the mechanical and structural characteristics of the aorta with MSC treatment. METHODS: 16 Yorkshire pigs underwent retroperitoneal exposure of the aorta. Peri-adventitial elastase and collagenase was applied to induce AAA formation. The aorta was treated with media-soaked (aneurysm) or MSC-soaked (treatment) GelFoam. Aortic diameter was monitored serially at postoperative (POD) 0, 7, 14, and 21. Histopathologic staining was performed for hematoxylin and eosin. Tensile strength was measured using a tensiometer and calculations were made for Young’s modulus and peak maximum strain. RESULTS: All animals survived the surgery and postoperative course. At POD21, mean aortic diameter increased to 1.483 cm +/- 0.31 for the aneurysm group vs 1.11 cm +/- 0.04 for the treatment animals (p < 0.004). The elastic modulus for the aneurysm group was 15.83 mPa +/- 1.61 compared to 22.13 mPa +/- 2.34 for the treatment groups (p = 0.034) (Fig. 1). There was no difference in the peak stress (p = 0.564). Medial thickness in the aneurysm group was reduced compared to the treatment animals (590.5 υm +/- 19.35 vs 646.10 υm +/- 11.97, p = 0.044). CONCLUSION: This is the first study to demonstrate the mechanical effects of stem-cell therapy on a porcine AAA model. Young’s modulus characterizes the capacity of tissue to withstand stress and was preserved in the MSC-treated animals. This mechanical test can be utilized to develop additional cell and drug-based therapies for AAA.