Cell signaling in wound repair: Which factor released from a blood clot specifically stimulates surrounding cells to grow and proliferate during the healing process?

Introduction / Context:
After tissue injury, blood clotting is rapidly followed by a complex cascade of cell signaling events that promote wound healing. Platelets trapped in the clot release an array of growth factors. Understanding which factor directly stimulates neighboring cells to proliferate is fundamental in cell biology and medical physiology.

Given Data / Assumptions:

• A blood clot contains activated platelets.
• Platelets secrete multiple growth factors stored in alpha granules.
• Question asks for the factor that stimulates cell growth during healing.

Concept / Approach:
PDGF (platelet-derived growth factor) is a potent mitogen released from platelets within the clot. It binds PDGF receptors (RTKs) on fibroblasts, smooth muscle cells, and other mesenchymal cells to activate downstream signaling (for example, Ras → MAPK and PI3K → Akt), driving cell cycle entry and proliferation, which are essential for granulation tissue formation and matrix deposition.

Step-by-Step Solution:

Verification / Alternative check:
Histologic wound-healing phases show early fibroblast chemotaxis and proliferation coinciding with PDGF and TGF-β release; PDGF is specifically highlighted as a mitogen and chemoattractant for fibroblasts.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing any growth factor with the specific clot-derived mitogen. Remember that the keyword is “from a blood clot,” pointing to platelet products and thus PDGF.

Final Answer:
PDGF (platelet-derived growth factor).