A patient presents with a wound on his leg. It heals six weeks later. Which of the following mediators is involved in promoting wound healing?
**Core Concept**
Wound healing is a complex process involving multiple stages, including inflammation, proliferation, and remodeling. It is mediated by various growth factors, cytokines, and chemokines that facilitate the repair of damaged tissues.
**Why the Correct Answer is Right**
Vascular endothelial growth factor (VEGF) plays a crucial role in promoting wound healing by stimulating angiogenesis, which is the formation of new blood vessels. This process is essential for delivering oxygen and nutrients to the wound site, facilitating the proliferation of fibroblasts, and promoting the deposition of extracellular matrix. VEGF acts by binding to its receptors on the surface of endothelial cells, triggering a signaling cascade that leads to the expression of genes involved in angiogenesis.
**Why Each Wrong Option is Incorrect**
**Option A:** Platelet-derived growth factor (PDGF) is involved in wound healing, but it is primarily responsible for promoting the proliferation of fibroblasts and the deposition of extracellular matrix, rather than angiogenesis. PDGF acts by binding to its receptors on the surface of fibroblasts, triggering a signaling cascade that leads to the expression of genes involved in cell proliferation and matrix deposition.
**Option B:** Interleukin-6 (IL-6) is a cytokine involved in the inflammatory response, but it is not primarily involved in promoting wound healing. IL-6 acts by binding to its receptors on the surface of immune cells, triggering a signaling cascade that leads to the production of other cytokines and the activation of immune cells.
**Option C:** Transforming growth factor-beta (TGF-β) is involved in wound healing, but it is primarily responsible for promoting the deposition of extracellular matrix and the differentiation of fibroblasts into myofibroblasts. TGF-β acts by binding to its receptors on the surface of fibroblasts, triggering a signaling cascade that leads to the expression of genes involved in matrix deposition and cell differentiation.
**Option D:** Tumor necrosis factor-alpha (TNF-α) is a cytokine involved in the inflammatory response, but it is not primarily involved in promoting wound healing. TNF-α acts by binding to its receptors on the surface of immune cells, triggering a signaling cascade that leads to the production of other cytokines and the activation of immune cells.
**Clinical Pearl / High-Yield Fact**
VEGF is also involved in tumor angiogenesis, making it a potential target for cancer therapy. Inhibitors of VEGF have been shown to reduce tumor growth and metastasis in various cancer models.
**Correct Answer:** C. Vascular endothelial growth factor (VEGF).