THBS1 and peripheral arterial disease: Given the fact that the amount of ECs is only a small percentage of all the cells in tissues of tumors or PAD, and other types of cells including smooth muscle cells, stromal fibroblasts and immune cells also secrete TSP-1, there is a need for further model validation in order to sustain and extend our model conclusion, at least qualitatively, to other cell types of interest [26].