Which of the following cells is primarily responsible for collagen deposition during the proliferative phase of wound healing?

Explanation

## Cellular Roles in Wound Healing Proliferative Phase **Key Point:** Myofibroblasts are the primary cell type responsible for collagen synthesis and deposition during the proliferative phase of wound healing. ### Myofibroblast Characteristics - Differentiated from fibroblasts under the influence of TGF-β and other cytokines - Appear 3–5 days post-injury and peak at 1–2 weeks - Possess contractile properties due to α-smooth muscle actin (α-SMA) expression - Responsible for wound contraction and collagen matrix deposition - Produce Types I and III collagen ### Timeline of Wound Healing Phases | Phase | Duration | Key Cells | Primary Function | |-------|----------|-----------|------------------| | Inflammatory | 0–3 days | Neutrophils, macrophages | Hemostasis, debris removal | | Proliferative | 3–21 days | Fibroblasts, myofibroblasts | Collagen synthesis, angiogenesis | | Remodeling | 3 weeks–2 years | Fibroblasts, myofibroblasts | Collagen remodeling, scar maturation | **High-Yield:** Myofibroblasts are identified by α-SMA positivity on immunohistochemistry and are the hallmark cell of the proliferative phase. **Clinical Pearl:** Excessive myofibroblast activity and persistence leads to pathologic wound contraction and hypertrophic scar formation, particularly in deep wounds or burns. [cite:Robbins 10e Ch 3]