Date of Award

3-2018

Degree Name

MS in Biomedical Engineering

Department/Program

Biomedical and General Engineering

Advisor

Trevor Cardinal

Abstract

Current treatments for peripheral arterial occlusive disease (PAOD) have limited success, so there is a need to develop more effective treatments. Because patients with native collaterals have a better prognosis, promoting collateral arteriogenesis is a potential PAOD treatment. Additionally, female PAOD patients have a worse response to treatment and a worse prognosis compared to males, which could be due to impaired collateralization. Cell transplantation is a potential treatment option to promote collateral arteriogenesis. Bone marrow derived stem cells are the main cell type that has been investigated, but they have had limited clinical success. Delivering a stem cell type native to the tissue like myogenic stem cells could have improved outcomes. In this study, the lateral spinotrapezius feed artery was ligated in male and female Balb/C mice to induce collateral capillary arteriogenesis, and 7 days post ligation ­­­­arterialized collateral capillary (ACC) number and diameter were determined. There were no differences between sexes, which could be because young, healthy mice were used in this study rather than aged and diseased models. Because we observed no sex differences, we then assessed the effect of myogenic cell transplantation in male mice only. Immediately following ligation of the spinotrapezius feed artery, mice were treated with myogenic cells, thrombin, or vehicle, and 7 days post ligation ACC number and diameter were determined. Thrombin increased ACC number, but myogenic cells had no effect. However, myogenic cells increased ACC diameter, and both myogenic cells and thrombin decreased ACC number in the region of the muscle with the largest collateral, and increased the maximum ACC diameter. Another factor that could affect ACC formation is a pre-existing collateral (PEC), which only some Balb/C mice have, so we also separated mice into PEC and non-PEC groups for analysis. In mice with a PEC, thrombin increased ACC number, and both myogenic cells and thrombin increased ACC diameter. There was a trend toward smaller arterialized capillaries in mice with a PEC, which could be because the majority of the blood flow is redirected through the PEC, so the PEC was the main vessel to remodel. These results are consistent with previous studies that indicated that thrombin augments arteriogenesis as well as increasing V-CAM, and suggest that myogenic cells have a similar effect possibly by secreting arteriogenic factors such as VEGF and MMPs. Because myogenic cells increase arteriogenesis, and macrophages are an essential regulator of arteriogenesis, we also tested the hypothesis that myogenic cells would increase macrophage content. Macrophage number increased with ligation, but there was no difference in macrophage number between any of the treatment groups. The lack of difference in macrophage number could be because the day 7 timepoint was too late, as macrophage content peaks at day 3. Because myoblasts increased arteriogenesis, they also may have increased the number M2 macrophages, which are the main macrophage contributor to arteriogenesis, but we used a general macrophage marker and could not detect an increase in M2 macrophages. In future studies, to determine if there is an increase in M2 macrophages a stain specific to M2 macrophages like CD206 could be added. Additionally, a diabetic Balb/C strain could be used to determine if arteriogenesis is impaired in males compared to females in a diseased model.

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