A 38-year-old woman with poorly controlled type 2 diabetes (HbA1c 9.2%) undergoes abdominal wall reconstruction for ventral hernia repair. At 3 weeks postoperatively, the surgical wound shows delayed epithelialization with thin, friable granulation tissue. Tensile strength testing reveals only 30% of normal wound strength at this timepoint. Which cellular/molecular mechanism is primarily impaired in this patient?

Explanation

## Diabetes and Impaired Wound Healing — Molecular Basis **Key Point:** Hyperglycemia (HbA1c 9.2%) impairs the **proliferative phase** of wound healing, specifically **fibroblast function and collagen synthesis**. ### Mechanisms of Diabetic Wound Healing Impairment: | Mechanism | Effect | Timeframe | |-----------|--------|----------| | **Impaired growth factor signaling** (↓VEGF, ↓TGF-β responsiveness) | ↓ Fibroblast proliferation, ↓ Collagen I/III synthesis | Proliferative phase (POD 5–21) | | ↑ Advanced glycation end-products (AGEs) | Cross-link collagen prematurely, ↓ elasticity | Remodeling phase | | ↓ Angiogenesis (↓ VEGF signaling) | Poor blood flow, hypoxia | Proliferative phase | | Impaired PMN function | ↓ Chemotaxis, ↓ phagocytosis | Inflammatory phase | | ↑ Protease activity (MMPs) | Excessive collagen degradation | Late proliferative/remodeling | **Clinical Pearl:** At POD 21, the wound should be in the **late proliferative/early remodeling phase** with robust collagen deposition. Only 30% tensile strength (vs. expected 50–60% at 3 weeks) indicates **impaired collagen synthesis**, not degradation. **High-Yield:** Hyperglycemia → ↓ TGF-β and VEGF signaling → ↓ fibroblast proliferation → ↓ collagen deposition → weak, friable granulation tissue. **Mnemonic:** **DM Wounds = Delayed Maturation** — impaired growth factors, not excessive breakdown.