Wound Healing Is Not a Moment — It’s a Dynamic Biological Orchestra
A practical refresher on the biology of wound healing and why it breaks down.
By Nikolai Sopko, MD, PhD Chief Scientific Officer & Chief Operating Officer, PolarityBio
Wounds don’t heal by accident. They heal through a tightly regulated, biologically programmed sequence of events. When that sequence runs smoothly, tissue restores structure and function When it breaks down, wounds stall … and become chronic.
(Read our regeneration blog for more details on why regeneration matters).
A few facts worth pausing on:
Acute wounds are biologically “time-limited” and they are meant to heal
Chronic wounds are not simply slow wounds; they are biologically different
Most chronic wounds are stuck in one phase of healing, rather than progressing through all of them
In conditions like diabetes, vascular disease, and neuropathy, multiple failure points often occur simultaneously
Understanding where and why healing derails is foundational to modern wound care.
The Four Classic Phases of Wound Healing
Wound healing is traditionally divided into four overlapping phases:
Hemostasis
Inflammation
Proliferation
Remodeling (Maturation)
These phases are not strictly linear, but they must occur in the right sequence, intensity, and duration.
Phase 1: Hemostasis
Stopping the Bleed, Starting the Signal
Timeline: Minutes to hours after injury
Primary goals:
Stop bleeding
Form a provisional matrix
Initiate cellular signaling
Key events:
Platelet aggregation
Fibrin clot formation
Release of growth factors (PDGF, TGF-β, VEGF)
Clinical relevance:
The clot is more than a plug; it’s a temporary scaffold and signaling hub that tells surrounding cells a wound has occurred.
How this phase can fail
Impaired platelet function
Poor perfusion
Excessive anticoagulation
Repeated trauma disrupting early clot stability
Chronic wound callout (DFUs):
In ischemic or neuropathic wounds, early microtrauma can repeatedly disrupt hemostasis, preventing progression to downstream phases.
Phase 2: Inflammation
Necessary, but Dangerous if Prolonged
Timeline: Hours to days
Primary goals:
Clear bacteria and debris
Recruit immune and reparative cells
Protect against infection
Key players:
Neutrophils
Macrophages
Mast cells
These cells release cytokines and proteases that prepare the wound for rebuilding.
Important distinction: Inflammation is not the enemy, it’s essential. Persistent inflammation is the problem.
How this phase becomes disrupted
Ongoing bacterial burden or biofilm
Repeated tissue injury
Ischemia and hypoxia
Metabolic dysfunction (e.g., diabetes)
Chronic wound callout:
Many chronic wounds are biologically trapped in inflammation, with elevated proteases degrading growth factors and extracellular matrix faster than they can be rebuilt.
Phase 3: Proliferation
Rebuilding the Tissue Framework
Timeline: Days to weeks
Primary goals:
Fill the wound
Restore vascular supply
Re-epithelialize the surface
Key processes:
Fibroblast proliferation and collagen deposition
Angiogenesis and neovascularization
Keratinocyte migration across the wound bed
Clinical relevance:
This phase depends on viable cells, oxygen, nutrients, and signaling balance. (Check out this blog on cellular vs acellular therapy.)
How proliferation fails
Poor perfusion or oxygenation
Inadequate cellular response
Excessive inflammation destroying new tissue
Deficient extracellular matrix
Chronic wound callout:
In DFUs, fibroblasts and keratinocytes often show reduced responsiveness to growth factors, limiting granulation and epithelial advance.
Phase 4: Remodeling
From Closure to Durability
Timeline: Weeks to years
Primary goals:
Strengthen repaired tissue
Reorganize collagen
Restore functional integrity
Key events:
Collagen III replaced by collagen I
Vascular pruning
Gradual increase in tensile strength
Key insight:
A wound can be “closed” but not truly healed.
How remodeling is compromised
Premature loading or pressure
Recurrent trauma
Persistent inflammation
Poor matrix organization
Chronic wound callout:
Failure to remodel properly contributes to high recurrence rates, particularly in plantar DFUs.
Acute vs. Chronic Wounds: A Biological Shift
Acute wounds:
Progress through all phases
Resolve inflammation
Restore tissue architecture
Chronic wounds:
Stall—most often in inflammation
Exhibit elevated proteases and senescent cells
Lack coordinated cellular signaling
Fail to regenerate full-thickness skin
Clinical takeaway:
Chronic wounds are not just delayed—they are biologically dysregulated.
Why Modern Wound Healing Focuses on Biology, Not Just Coverage
Traditional wound care addressed:
Moisture balance
Protection
Offloading
These remain essential, but often insufficient alone.
Modern strategies increasingly aim to:
Reset the inflammatory environment
Support angiogenesis
Restore cellular signaling
Rebuild tissue across multiple skin layers
This shift reflects a deeper understanding of how wound healing works—as a multicellular, staged biological process, not a surface event.
Final Thought
Wound healing is not about forcing closure. It’s about restarting a stalled biological program. Check out our recent blog on why this is re-start is critical (Skin is Not a Covering)
When we understand where and why healing breaks down, we can choose interventions that support the body’s innate capacity to regenerate, not just cover a defect.
That distinction matters for outcomes, durability, and recurrence, especially in the patients we see every day.