From the Guidelines
Tissue healing involves a complex interplay of various cell types, including platelets, inflammatory cells, fibroblasts, endothelial cells, epithelial cells, and stem cells, which work together to repair damaged tissue. The process begins with platelets, which form a clot to stop bleeding and release growth factors, such as platelet-derived growth factor (PDGF), that initiate healing 1. Inflammatory cells, including neutrophils and macrophages, then arrive to clear debris and fight infection, with macrophages playing a key role in wound debridement and secreting growth factors, such as PDGF, transforming growth factor-beta (TGF-β), and vascular endothelial growth factor (VEGF) 1.
Key Cell Types Involved in Tissue Healing
- Fibroblasts produce collagen and other proteins that form the extracellular matrix, providing structure to the healing tissue
- Endothelial cells create new blood vessels (angiogenesis) to supply oxygen and nutrients to the regenerating tissue
- Epithelial cells migrate and proliferate to cover exposed surfaces
- Stem cells differentiate into specialized cells needed for tissue repair
Growth Factors and Cytokines
Growth factors and cytokines, including PDGF, TGF-β, and VEGF, coordinate the healing process by stimulating cell migration, proliferation, and matrix production 1. The extracellular matrix provides structural support and influences cell behavior during healing. This complex, coordinated process involves multiple cell types and signaling molecules working together to restore tissue integrity and function after injury. The use of recombinant human growth factors, such as rhPDGF-BB and rhBMP-2, has shown promise in enhancing wound healing events and promoting tissue regeneration 1.
From the Research
Components of Tissue Involved in Healing
The components of tissue involved in healing include:
- Platelets: play a critical role in tissue repair and regeneration, regulating cellular migration, proliferation, and angiogenesis 2, 3, 4
- Neutrophils: contribute to the process of wound healing, releasing cytokines and growth factors that manipulate the inflammatory phase of healing 2, 5
- Macrophages: primarily contribute to the process of wound healing, releasing cytokines and growth factors that manipulate the inflammatory phase of healing 2
- Fibroblasts: lay down the extracellular matrix, and their proliferation is initiated by growth factors such as platelet-derived growth factor (PDGF) 2
- Endothelial cells: help create a pro-coagulant, cytokine-rich environment that promotes the capture, activation and proliferation of circulating immune cells and recruitment of key pro-fibrotic cell types such as myofibroblasts 5
- Stem cells: play a role in regenerative healing, producing new skin cells from stem cell reservoirs, resulting in healing with minimal or no scarring 6
- Growth factors: such as PDGF, initiate fibroblast and keratinocyte proliferation, and manipulate the inflammatory phase of healing 2, 6
- Cytokines: such as interleukins (ILs) and TNF-α, are chemotactic for white cells and fibroblasts, and manipulate the inflammatory phase of healing 2
- Extracellular matrix: laid down by fibroblasts, and removed by matrix metalloproteinases (MMPs) 2
- Matrix metalloproteinases (MMPs): remove damaged structural proteins such as collagen 2
- Tissue inhibitors of metalloproteinases (TIMPs): inhibit the activity of MMPs 2