Graduate Student Seminar Series – Kate MacQuarrie

Graduate Student Seminar Series
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Location: MS2158 – 1 King’s College Circle
Presentation Title: Selecting the optimal support cell type for the autologous endothelialization of a vascular graft
Abstract:
The endothelialization of vascular scaffolds, such as small-diameter vascular grafts, has been a long-standing goal in the tissue engineering field. To date, there has been a lack of suitable sources of endothelial cells, and even when endothelial cells are available, they have taken too long to confluently endothelialize the scaffolds, limiting clinical adoption.
Our group has shown that there is a suitable source of endothelial cells within fat tissue, termed human adipose-derived microvascular endothelial cells (HAMVECs). Further, our group has shown that when HAMVECs are cultured across from adipose-derived stromal cells (ASCs) on a porous, electrospun scaffold, the scaffold can be confluently endothelialized in 2 days.
Separately, our lab has shown that these ASCs can be differentiated to produce contractile, smooth muscle cell (SMC)-like cells (VSMCs). Further, VSMCs’ extracellular matrix (ECM) production can be stimulated by the direct co-culture of VSMCs with monocytes.
My project has involved assessing the phenotype of the co-cultured endothelia, determining which support cell type (ASCs, VSMCs, or VSMC+monocytes) is best for producing a confluent endothelium, and ultimately, producing autologously endothelialized grafts.
In studying the effects of co-culture on the resulting endothelia, my work thus far has demonstrated that co-culturing HAMVECs with ASCs significantly increases endothelialization as early as two hours after seeding compared to monocultured HAMVECs. Using an array that detects over 50 proteins produced in the culture media, I found that HAMVEC+ASC co-culture promotes a less angiogenic character. Furthermore, I showed via immunostaining that co-culture increases junctional linearity and HAMVEC elongation, increases vasodilator-related protein production, and decreases inflammatory protein production and white blood cell adhesion.
In assessing which type of support cells are best suited for scaffold endothelialization, I found that ASCs, VSMCs, or VSMC+monocytes could all support 70-80% endothelialization within 24 hours, compared to <25% with HAMVECs alone. I performed mass spectrometry, which validated that any type of co-culture reduced the expression of inflammatory endothelial markers relative to monoculture. However, in the proteomic assessment, and through immunostaining, we saw that using VSMCs or VSMC+monocytes increased the expression of proteins involved in contraction and of SMC character. Furthermore, via histological staining and a biochemical assay, we saw that including monocytes in the co-culture system with VSMCs increased elastin production.
Thus far, we have shown that in addition to accelerating endothelialization, co-culturing HAMVECs with any of the three support cell types produces a healthier and less thrombogenic endothelium, but differentiated VSMCs are needed for the support cells to have a biomimetic, contractile phenotype in co-culture. Furthermore, including monocytes increases elastin deposition, which is important for both compliance and support cell maturity.
Current and future work involves further assessing the hemocompatibility of the endothelia and producing tubular grafts seeded with VSMC+monocytes and endothelialized with HAMVECs in a perfusion bioreactor.
Supervisor Name: Dr. Paul Santerre
Year of Study: 4
Program of Study: PhD
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