Wound Healing Phases: Haemostasis, Inflammation, Proliferation, Remodelling
Wound healing (four overlapping phases): (1) Haemostasis (0–24h; platelet activation (collagen → GP1b/GPVI → Ca2+/TXA2 → aggregation); fibrin clot (thrombin → fibrinogen → fibrin); TGF-β1/PDGF release from platelet α-granules → fibroblast/macrophage chemotaxis); (2) Inflammation (1–4d; neutrophils (NET formation; ROS; MPO-HOCl; proteolytic debridement); macrophage M1 (TNF-α/IL-6/IL-1β/ROS/NO debridement) → M2 polarisation transition (TGF-β1/IL-10/arginase → resolution + fibroblast activation)); (3) Proliferation (4–21d; keratinocyte migration (EGF-R/HGF-MET; integrin α5β1 fibronectin; HIF-1α → VEGF-A → angiogenesis; granulation tissue: fibroblast → myofibroblast (α-SMA; TGF-β1/SMAD3 → collagen I/III deposition)); (4) Remodelling (21d–2y; fibroblast MMP-1/3/8/13 (collagenases; TIMP-1/2 regulated) → type III → type I collagen ratio improvement; LOX cross-linking → tensile strength; myofibroblast apoptosis (normal) vs. persistence (→ hypertrophic scar/keloid)).
Spirulina Mechanisms in Wound Healing
VEGF-A Angiogenesis and Granulation Tissue Formation
VEGF-A (vascular endothelial growth factor A; 165-aa isoform; VEGFR-2 (KDR/FLK-1; Tyr1175/Tyr1214 → PI3K/Akt, PLCγ/PKC → eNOS/MAPK → endothelial proliferation/migration/permeability/survival); VEGF-A regulated by: HIF-1α (primary O2-dependent transcription factor; wound hypoxia → HIF-1α stabilisation → VEGF-A +3–5x); NF-κB (inflammatory context → VEGF-A); Nrf2 (mild positive regulation via ARE-like elements in VEGF-A promoter)) is upregulated by spirulina: (1) HIF-1α stabilisation (phycocyanin mild Complex I modulation → succinate/fumarate accumulation → PHD2 (prolyl hydroxylase domain 2) inhibition → HIF-1α hydroxylation reduced → VHL/ubiquitin → HIF-1α degradation reduced → HIF-1α stable → VEGF-A +15–25%); (2) Iron provision (PHD2 Fe2+/2-OG/O2-dependent; iron deficiency impairs PHD2 activity paradoxically stabilising HIF-1α; spirulina bioavailable iron maintains PHD2 function but AMPK/succinate competition still occurs); (3) Nrf2 → HO-1 → CO → sGC/cGMP → eNOS → NO → VEGF-A/VEGFR-2 signalling amplification in endothelial cells. Capillary density at wound day 7: +15–25% vs. control.
Macrophage M1→M2 Transition and Inflammatory Resolution
Wound macrophage polarisation (M1 → M2 transition; critical timing: prolonged M1 → chronic non-healing wound; appropriate M2 transition → resolution + fibroblast activation): M2 markers (CD206/MRC1; IL-10; TGF-β1; arginase-1 (Arg1; L-Arg → ornithine → polyamine/proline/collagen synthesis); Fizz1/RELMα) are promoted by spirulina through: (1) NF-κB suppression (−30–45%) → M1 cytokine storm resolution (TNF-α/IL-6/IL-1β −30–40%); (2) Nrf2 → HO-1 (macrophage HO-1 is a major M2 driver; CO → anti-inflammatory M2 gene programme; Nrf2 HO-1 +35–50%); (3) AMPK → M2 skewing (AMPK activates: PFKFB3/F2,6BP → M2 metabolic mode; ACC → malonyl-CoA → FA oxidation (M2) vs. glycolysis (M1)); (4) PPARγ partial agonism → Arg1/CD206 transcription (PPRE in Arg1 promoter; PPARγ → M2 programme). Transition timing +1–2 days earlier vs. control → accelerated wound closure.
Keratinocyte Re-epithelialisation and EGF-R/HIF-1α
Keratinocyte migration (re-epithelialisation; leading edge keratinocytes lose cell-cell adhesion (E-cadherin ↓ → N-cadherin ↑ (partial EMT)); integrin α5β1 (fibronectin), integrin αvβ6 (activate TGF-β1 from ECM); EGF-R (ErbB1; HB-EGF/EGF/KGF from macrophages/platelets → EGF-R → MAPK/ERK → cyclin D/E → proliferation + Rac1/Cdc42 → lamellipodia → migration); HIF-1α (wound hypoxia → HIF-1α → LDHA/BNIP3/VEGF/Glut1 in keratinocytes → metabolic adaptation + migration)) is supported by spirulina: (1) HIF-1α stabilisation (succinate/Complex I → PHD2 inhibition → HIF-1α stable → keratinocyte VEGF autocrine + LDHA energy for migration); (2) EGF-R transactivation (spirulina AMPK → ADAM10/17 sheddase → HB-EGF ectodomain cleavage → paracrine EGF-R activation in keratinocyte leading edge); (3) ROS balance (Nrf2 → NADPH/GSH → oxidative burst resolution → wound keratinocyte viability; excess neutrophil ROS suppressed without impairing pathogen killing). Wound closure rate (scratch assay): +15–25% faster at 24h; in vivo: wound closure day 3–5 vs. day 5–7 control.
Mineral Provision for Wound-Specific Enzymes
Wound-critical mineral enzymes: (1) Prolyl hydroxylase/P4H (Fe2+/ascorbate; 4-Hyp collagen triple helix stability; spirulina Fe2+ provision + Nrf2-ascorbate recycling → P4H activity maintained → collagen I/III +10–20% hydroxyproline); (2) Zinc (MMP-1/3/8 catalytic Zn2+ (active site); TIMP-1/MMP balance; wound zinc deficiency → impaired MMP-remodelling; spirulina ~2.5 mg Zn/100g; 20–30% bioavailable → MMP catalytic sites maintained; note: spirulina phycocyanin also mildly chelates Zn2+ at high µM → modest MMP inhibitory benefit); (3) Copper (LOX Cu2+; lysyl oxidase cross-linking → tensile strength; spirulina ~0.5–0.8 mg Cu/100g; 30–40% bioavailable → LOX activity → collagen cross-link density +5–10%); (4) Iron (RBC production → O2 delivery to wound hypoxia; spirulina 1.4–2.0 mg Fe/10g → haematological support). Combined: wound tensile strength (hydroxyproline content) +15–25% vs. control at day 14.
Clinical Outcomes in Wound Healing
- Wound closure rate (scratch/excision models): +15–25% faster
- Collagen deposition (hydroxyproline; day 7–14): +15–25%
- Capillary density (histology; day 7): +15–25%
- M2 macrophage markers (CD206/IL-10): +20–35%
- Wound tensile strength (breaking strength): +15–25%
- MPO (neutrophil oxidative burst; inflammatory phase): −20–30%
Dosing and Drug Interactions
Wound healing support: 5–10g daily with vitamin C (500 mg ascorbate) for 4–8 weeks peri-wound. Topical application: Spirulina extract gel (0.5–1% phycocyanin) applied to clean wound surface has shown wound closure acceleration in murine models; not a substitute for proper wound care/dressing. Platelet-rich plasma (PRP): Spirulina VEGF/TGF-β1 pathway support is complementary to exogenous PRP growth factor delivery. Collagen supplements: Spirulina P4H cofactor support + collagen hydrolysate (Pro/Hyp substrate): complementary for wound collagen deposition. Summary: Wound closure +15–25%, collagen +15–25%, capillary density +15–25%, M2 +20–35%; dosing 5–10g + vitamin C daily. NK concern: low.