Which molecule is a mitogen that contributes to vascular smooth muscle proliferation?

• A. Insulin
• B. Angiotensin II
• C. Albumin
• D. Glucagon

Answer: (B)

Angiotensin II acts as a mitogen for vascular smooth muscle cells, driving their proliferation and contributing to vascular remodeling. When Ang II binds to the AT1 receptor on smooth muscle cells, it activates signaling pathways such as MAPK/ERK and PI3K/AKT, and stimulates NADPH oxidase to generate reactive oxygen species. These signals push cells from quiescence into the cell cycle, increasing DNA synthesis and cell division, which thickens the vessel wall and promotes constriction. This mitogenic effect on vascular smooth muscle is a key part of how the renin-angiotensin system contributes to hypertension and vascular disease. By contrast, the other molecules listed are not primary mitogens for vascular smooth muscle in this context; they may have metabolic or transport roles, but they do not robustly drive VSMC proliferation via mitogenic signaling.