What growth factor is important during the inflammatory phase of wound healing?

Platelet-Derived Growth Factor is Important During the Inflammatory Phase of Wound Healing

The correct answer is C. Platelet-derived growth factor (PDGF) is the primary growth factor responsible for stimulating chemotaxis and mitogenicity of neutrophils, monocytes, macrophages, and fibroblasts during the inflammatory phase of wound healing. 1

Role of PDGF in the Inflammatory Phase

During wound healing, four partially overlapping phases occur:

1. Hemostasis
2. Inflammatory phase
3. Granulation phase
4. Maturation phase

In the inflammatory phase, PDGF plays a critical role through several mechanisms:

• Following blood clot formation, degranulating platelets release PDGF, which initiates the inflammatory response 1
• PDGF stimulates chemotaxis (cell migration) and mitogenicity (cell proliferation) of:
  • Neutrophils
  • Monocytes
  • Macrophages
  • Fibroblasts 1, 2

Comparison with Other Growth Factors

While multiple growth factors are involved in wound healing, they serve different primary functions:

• PDGF (Option C): Primary in the inflammatory phase, stimulating chemotaxis and proliferation of inflammatory cells 1, 2
• VEGF (Option D): Released during the inflammatory phase but primarily functions to increase vascular permeability rather than stimulate inflammatory cell recruitment 1
• AKT kinase (Option A): Not a growth factor but a signaling protein involved in cellular pathways
• Androgen (Option B): A hormone, not a growth factor involved in wound healing

Evidence Supporting PDGF's Role

Multiple studies confirm PDGF's critical role in the inflammatory phase:

• PDGF is a potent activator for cells of mesenchymal origin and stimulates chemotaxis, proliferation, and new gene expression in monocytes-macrophages and fibroblasts 2
• In experimental wound models, exogenously administered PDGF significantly augments the time-dependent influx of inflammatory cells and fibroblasts 2
• PDGF appears to transduce its signal through wound macrophages and may trigger positive autocrine feedback loops 2
• PDGF-BB has demonstrated acceleration of healing by 30% in excisional wounds and increased wound breaking strength by 50-70% in incisional wounds 2

Clinical Applications

The understanding of PDGF's role has led to therapeutic applications:

• The FDA has approved recombinant human PDGF-BB in combination with beta-tricalcium phosphate for treatment of:

  • Intrabony periodontal defects
  • Furcation defects
  • Gingival recessions 1

• PDGF works synergistically with other growth factors, particularly when combined with insulin-like growth factor I, enhancing connective tissue formation 3

In conclusion, while multiple growth factors participate in wound healing, PDGF is specifically critical during the inflammatory phase by stimulating the chemotaxis and proliferation of key inflammatory cells that initiate the wound healing cascade.