THBS1 and atherosclerosis: Thus, in normal low levels, TSP-1 could act as an inducer of VSMC proliferation and, in pathological conditions (e.g., atherosclerosis), whereas TSP-1 is upregulated, high levels of TSP-1 could act as an anti-proliferative agent, although the effects of TSP-1 could be different in function of the pathology concerned [6].