Transcript Document
Wound Healing Education
July 17th 2013
Breda Cullen PhD
1
Learning objectives :
Pathophysiology of wound healing
The role of proteases in healing & non-healing wounds
Which proteases predominate in chronic non-healing wounds
Measurement of protease activity
What current treatments are available to deal with excessive
proteases and clinical evidence
How could a point of care measurement of proteases help in
future practice
Wound Healing principles
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Skin Structure
Skin provides
Protection
Temperature control
Sensation
Vitamin D synthesis
Elimination
Psychological/sexual
Also known as
Subcutaneous
Skin
15% of total body weight
Thickness varies dependant on levels of friction encountered
Consists of two main layers - Epidermis and Dermis
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The Epidermis
Properties of the Epidermis:
Avascular layer which consists of five sub layers
Receives blood flow/perfusion from dermis
As cells move towards the surface they become keratinised
Keratin is a fibrous protein that is present in the outer layer of skin
The stratum corneum being completely keratinised acts as a moisture repellent barrier
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The Dermis
• Connective tissue layer located below the epidermis
– contain nerve endings, sweat /sebaceous glands, hair follicles, blood and lymph vessels
– Ground Substance present
• Matrix which supports fibers and cells of dermis
• Retains water in the skin
• Collagen is major component which supports all structures within the dermis
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Cells Present in the Skin
Keratinocytes
Fibroblasts
Endothelial cells
In dermis & epidermis
White blood cells – neutrophiles & moncytes/macrophages
Red blood cells
Platelets
In blood
vessels
•There are multiple types of cells with widely different roles needed to facilitate
wound healing
Neutrophils
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Monocytes / Macrophages
Fibroblasts
Endothelial cells
Keratinocytes
Types of Wound Healing
Primary Intention
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Secondary Intention
The “3 R’s” of Healing
Removal of damaged tissue & foreign
materials
INFLAMMATION
Repair of lost or damaged tissue
GRANULATION TISSUE
Remodelling of newly deposited
granulation tissue
WOUND CLOSURE & SCAR FORMATION
Wound Healing Cascade
Inflammation
0.1
0.3
1
Reconstruction
3
10
Remodeling
30
100
Days
Wound Healing Process
Time
minutes
3 days
Haemostasis
Inflammation
IMPAIRED
HEALING
Bacterial Contamination
14 days
Angiogenesis
Granulation
Epithelialization
6 months
Remodeling
Chronic wounds - Pathophysiology
12
Worrying Facts
Diabetic foot ulcers
246 million people are living with Diabetes
46% of diabetics are between 40 –59 years old
Globally a leg is amputated due to diabetes every 30 seconds
60% of amputations are due to infection
45% of amputees die within 5 years
1 in 14 adults in the world will have diabetes by 2025
Venous leg ulcers
1 - 1.3% of the world’s population have a venous leg ulcer
In the USA alone this is estimated at 2.5 million people
The cost to treat in UK represents the 3rd biggest NHS cost after cancer
and cardiovascular disease
UK, Germany, France & Italy combined cost is est. at $12 billion
Prevalence is increasing due to sedentary lifestyle and obesity
Diabetic Foot Ulcers
Characterised by vascular & neurological abnormalities
Caused by neuropathy, ischemia & infection
Autonomic nerve failure
Neuropathy, decreased sweating, dry easily damaged skin
45% of diabetics develop peripheral vascular disease
Increased susceptibility to infection
Diabetes has a detrimental effect on neutrophil function
Venous Leg Ulcers
Characterised by long-standing venous hypertension
Results from faulty communicating & superficial vein valves
damaged deep vein valves
deep vein occlusion
muscle dysfunction or pump failure
Caused by leakage of macromolecules e.g. fibrinogen (fibrin cuff)
development of lipodermatosclerosis
iron deposition & free radical formation
tissue damage & impaired healing
Pressure Sores
Characterised by deep tissue necrosis
Necrosis & ulceration determined by degree & duration of pressure
Muscle fibres show degenerative changes with 60 mmHg for 1 hr
Over bony prominences compression can reach 2600 mmHg
Increased external pressure = oedema, ischemia, cell autolysis
Persistent occlusion of vessels - cell damage & epidermal injury
Development Of An Ulcer
Development Of An Ulcer
Development Of An Ulcer
Development Of An Ulcer
Development Of An Ulcer
Why Don’t Chronic Wounds Heal?
The vicious circle of delayed wound healing
Degradation of ECM and
growth factors
Delayed
Wound
Healing
Cells produce
excess proteases
Bacterial proteases
and toxins
Increased inflammatory
response
Falanga V. The Chronic Wound: Impaired Healing and Solutions in the Context of Wound Bed Preparation. Blood Cells and Diseases, 2004;32:88-94.
Gibson D, Cullen B, Legersterr E, Harding KG, Schultz G. MMPs Made Easy. Wounds International 2009; 1 (1): Available from http://www.woundsinternational.com
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Chronic, Stalled, Delayed Wounds Exhibit:
HIGH LEVELS
PROTEASES
MMP’S & elastase
BIOBURDEN INFECTION
GROWTH FACTORS
INFLAMMATORY
CYTOKINES
CELL PROLIFERATION
LOW LEVELS
Falanga V. The Chronic Wound: Impaired Healing and Solutions in the Context of Wound Bed Preparation. Blood Cells and Diseases, 2004;32:88-94.
Gibson D, Cullen B, Legersterr E, Harding KG, Schultz G. MMPs Made Easy. Wounds International 2009; 1 (1): Available from http://www.woundsinternational.com
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Role of Proteases in Wound Healing
Selected
Growth factor
Activation
Migration
& Stimulation
Fibroblasts
Formation &
degradation of
fibrin clot
Proteases
Cell Migration
Keratinocytes Epithelialization
Nwomeh BC, Yager DR, Cohen,IKC. Physiology of
the chronic wound. Clinics in Plastic Surgery July
1998 25(3):341-356.
Cleans
wound of
bacteria
Migration of
Inflammatory
cells
Debrides
wound of ECM
fragments
Protease Activity
Proteases in Chronic Wounds
Time
Healing wound
Non-healing wound
Bacterial Bioburden
Contamination:
–presence of bacteria without a host reaction
Colonization:
–presence of bacteria that initiates a host
reaction
Critical Colonization:
–multiplication of bacteria, creates a delay in
wound healing
Infection:
–Multiplication of bacteria with host reaction,
creates a delay in wound healing
Biofilm Formation:
–Complex community embedded in a
polysaccharide matrix
Grey, J. E et al. 2006c. wound assessment. British Medical Journal, 332, 285-288.
Healy, B. & Freedman, A. 2006. Infections. British Medical Journal, 332, 838-841
Bowler, P. G. & Davies, B. J. 1999. The Microbiology of Acute and Chronic wounds. Wounds, 11, 72-78
Dowd, S. E et al. 2008a. Survey of Bacterial diversity in Chronic wounds using Pryosequencing, DGGE, and full ribome shotgun sequencing. BMC Microbiology, 8, 15.
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Microflora of Chronic Wounds
P. aeruginosa
All wounds are colonised (1)
70 different microbial isolates from 12 infected chronic
wounds(2)
Our ability to determine when bacteria is causing a
problem in a wound is limited – is level or species or both
important?
Anaerobes thought to play a major role in certain wounds
(<60%) (2,3)
Biofilms protect bacteria in the wound
Bacteria produce virulence factors when stressed - these
include bacterial proteases which can add to the hostile
wound environment
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1. Grey, J. E et al. 2006c. British Medical Journal, 332, 285-288.
2. Bowler, P. G. & Davies, B. J. 1999. Wounds, 11, 72-78
3. Dowd, S. E et al. 2008a. BMC Microbiology, 8, 15.
S. aureus
Inflammatory Cytokines in Wound Healing
Inflammatory cells
stimulated by
Cytokines produced
by
Cytokines produced
include
ECM Fragments
Macrophages
TNF-alpha
Bacterial Endotoxins
Neutrophils
IL-1 alpha & beta
Platelet Products
Damaged skin cells
IL-6, IL-8
Role of Inflammatory Cytokines
To Clean & Protect the Wound
Migration of neutrophils to wound site
Activation of inflammatory cells
Up regulate more inflammation & cytokine production
Regulation of protease production & their inhibitors
Chemotaxis & migration of macrophages to wound site
Regulate next phase of wound healing
Stimulates production of growth factors for wound healing
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Chronic Wounds & Inflammatory Mediators
Wound Type
TNF-a
IL-6
IL-8
Normal Acute
0.55 (0.1-3.2)
27 (2.3 -132)
23 (2.7-78)
Healing Burn
1.0 (0.1-3.0)
25 (0.3 -156)
36 (5.2-51)
Delayed Burn
6.4 (0.1-74)
25 (1.7-118)
89 (22-292)
Values mean ng/ml; range in parenthesis
Henry et al. Surg. Clin. N. Am. Vol 83 2003
Elevated TNF-a & inflammatory cytokines linked with deficient healing
Chronic wounds said to be ‘stuck’ in the inflammatory phase of healing
Cooney, R. J. TNF-a & chronic abdominal sepsisTrauma Injury Infect. Crit. Care 42; 415-420 1997
Trengrove NJ. et al Cytokine levels in non-healing & healing chronic leg ulcers Wound Repair Reg.
8; 13-25 2000
Growth Factors in Wound Healing
EGF
PDGF
TGF-b
FGF
IGF
To stimulate new tissue formation & wound closure
Migration of fibroblasts & endothelial cells to wound site
Cell proliferation
Protease production
Extracellular matrix production (granulation tissue formation)
Formation of new blood vessels (angiogenesis)
Migration of keratinocytes (re-epithelisation)
Wound remodelling
Growth Factors in Chronic Wounds
Chronic wounds have high levels of proteases which can degrade growth factors
Growth
Factor
Degraded Growth Factors renders
them inactive
Diminished growth factor activity
may delay healing
Wound
Fluid Proteases
Tarnuzzer, R.W., Schulz, G.S., (1996) Wound Rep Reg. 4: 321-325
POD 1 - POD 7:
Acute Wound Exudate
I-13 - I-42:
Chronic Wound Exudate
The Chronic Wound Environment
Biological Properties of Wound Fluid
Healing Wounds
Stimulates cell growth
Numerous growth factors
Promotes matrix synthesis
Chronic Wounds
Kills cells
Inactives growth factors
Inhibits matrix synthesis
Need to Rebalance the Chronic Wound Environment
Removal of
Negative factors
Stimulation of
Positive factors
Reduce inflammation
Remove excess proteases
(Host & Bacterial Derived Proteases)
Control bacterial levels
Increase cell numbers /migration
Protect growth factors / ECM
Promote tissue formation
Proteases in chronic wounds
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Proteases in Wound Healing
• Proteases are protein-degrading enzymes
• 2 categories of proteases
– Serine proteases eg. Elastase
– Matrix metalloproteases eg. MMPs
• Function optimally under physiological conditions
• Proteases are required for wound healing
Zn
Ca
Z
Ca
• Collectively, can degrade all components of the extracellular
matrix
• Normally controlled at the tissue level by natural inhibitors eg.
TIMPs, AAT
• Synthesised and stored as inactive pro-enzymes
Armstrong DG, Jude E, The Role of Matrix Metalloproteinases in Wound Healing. Journal of the American Podiatric Medical Association Volume 92 Number 1 12-18 2002
Ovington LG, Overview of matrix metalloprotease modulation and growth factor protection in wound healing. Ostomy Wound Manage. 2002 Jun;48(6 Suppl):3-7.
Nwomeh BC, Yager DR, Cohen IK. Physiology of the chronic wound. Clin Plast Surg. 1998 Jul;25(3):341-56.
MMP Family >20 members
Collagenases
MMP1, MMP8, MMP13
Gelatinases (A&B)
MMP2, MMP9
Stromelysins
MMP3, MMP10, MMP11
Matrilysins
MMP7, MMP26
Membrane-bound MMPs
MMP14, MMP15, MMP16
Production, Activation and Inhibition of MMPs
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Proteases
MMP Family
>20 members
Collagenases
MMP1, MMP8, MMP13
1
8
Helix unravels exposing sites for MMP 2&9
9
Gelatinases (A&B)
MMP2, MMP9
2
Other chains broken
Proteases
MMP Family
>20 members
7
Stromelysins
MMP3, MMP10, MMP11
3
3
Mixture of peptides
Matrilysins
MMP7, MMP26
10
7
Inflammatory Proteases: Neutrophil-derived Elastase
Cleavage of Adhesion
Sites, Receptors
Degradation of Growth
Factors, Fibronectin,
ECM etc.
Inflammatory Proteases
ELASTASE
MMPs
Activation of
MMPs
Proteases in Chronic Wounds
Proteases are in excess in chronic wounds
Venous Leg Ulcers
Diabetic Foot Ulcers
Pressure Sores
10000
100
MMP level (ng/ml/mg)
Protease Activity (RFU/min/mg)
Inflammatory Proteases Predominate
1000
100
75
MMP-9
50
MMP-8
MMP-3
25
MMP-2
10
0
Elastase
MMPs
MMP-1
Chronic fluid
Published Data: Cullen, B. et al., (2002) Wound Rep Reg. 10: 16-25
Proteases (MMPs) & Protease Inhibitors Levels
Schultz & Mast Wounds Vol 10 1998 1F-8F
Yager, D.R. et al., (1997) Wound Rep Reg, 5: 23-32
200
(15)
(5)
(3)
(14)
150
100
50
0
(23)
Venous
Ulcer
Diabetic
Vascular
Acute
Wounds
Decubitis
α2 Macroglobulin (µg / mg Protein)
Collagenase ( m g/ml)
250
60
α2 Macroglobulin
40
20
Acute
Chronic
Wound Exudate
Proteases (Elastase) & Protease Inhibitors Levels in VLU wounds
100
Elastase
Alpha 1 Antitrypsin
30000
AAT – Protease Inhibitor Levels
90
Elastase Activity (Average)
80
70
60
50
40
30
20
*
25000
20000
15000
10000
5000
Healing
Non-healing
10
0
0
Week 0
Week 0
Ratio of Elastase:AAT
TIME
Wound Closure > 50%
Wound Closure < 50%
Week 0
3.63
0.94
Better control of protease activity in healing wounds
Growth Factor Levels in Wounds
PDGF in Chronic wounds
120
100
60
40
20
S.pyogenes
200
80
S. aureus
300
100
P. aeruginosa
400
PDGF-AA
PDGF-AB
PDGF-BB
% Functional PDGF-BB
PDGF levels (pg/ml/mg)
500
Proteases degrade PDGF
0
PDGF
0
Chronic fluid
Acute fluid
Published Data: WUWHS, Paris 2004
PDGF&
Elastase
PDGF &
Bacterial Proteases
Published Data: SAWC, San Diego, 2005
Effect on ECM Proteins - Fibronectin
When elastase activity is low (group 1) fibronectin levels are high
When elastase activity is high (group 2) fibronectin levels are significantly reduced
Elastase
Fibronectin
2500000
250
Activity (RFU/min)
(pg/ml)
200
2000000
150
1500000
100
1000000
50
500000
0
0
Group 1
Group 2
Group 1
Group 2
ECM proteins (eg. Fibronectin) are readily degraded by proteases
Clinical Evidence
Number of clinical studies demonstrating that:
Protease activities are in excess in chronic non-healing wounds
Excess Protease Activity (EPA) has a negative impact on wound healing
Protease modulating therapies can reduce these protease activities &
promote healing
So how do we measure protease activity?
Today we have a lab test
Tomorrow we have a PoC
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Protease Assay Systems
There is no standardized assay for proteases - MMP & Elastase activity
We pre-wet our dressing samples to rule out differences due to physical absorption
We measure not only individual MMP activities but total MMP activity
We have investigated which proteases we need to reduce
We use clinically relevant levels of MMP & Elastase activity in our assays
We have optimized our products (Collagen/ORC) to reduce protease activity
We look at effect of products on protease activity
In the lab - In vitro
In wound fluid - Ex vivo
In patients – Clinical research
Types of Evidence for Protease Inactivation
In-Vitro Studies - Lab data testing effect on one variable
Modulation of elastase, MMP activity
Ex Vivo Studies – Testing carried out in the lab with human samples
Ability of dressings to change the chronic wound environment
Inactivation of proteases present in chronic wound fluid
In Practice - MOA Clinical Research Studies
Correlate change in biochemistry with clinical efficacy
Proof of MOA in patients
Protease Inactivation Assay
Assay measures ability of dressing to inactivate proteases
present in either a standard Protease solution or human chronic wound fluid
Pre-wet dressing &
add to chronic wound fluid
(Inc 37 0C)
Measure remaining activity
over next 24hours
Enzyme Activity measured by fluorescence
Elastase activity: MeOSuc-Ala-Ala-Pro-Val-AMC
MMP activity: Suc-Gly-Pro-Leu-Gly-Pro-AMC
Activity
Reduction in
Enzyme Activity
The Future: A Protease POC Test – The Theory
Excessive
Protease Activity
Week 0
Week 1-4
Increasing levels of Inflammatory Proteases
Following
appropriate therapy
Non-healing due to
high proteases
Detrimental level of
Protease activity
Non-healing for other reasons
OR
Healing wounds
No Protease
Activity
E
Elevated Test
Result
L
Low Test
Result
L
Low Test
Result
L
Low Test
Result
So how do we treat chronic wounds today
54
Factors which Affect Healing
Age
Chronic illness
Immune status
Medications
Smoking
Oxygenation / Circulation
PATIENT
Nutritional status
Stress
Local wound environment
Necrotic tissue / bioburden / proteases /exudate
Advanced wound dressings can help optimise the wound environment
Evolution of Wound Therapies
70’s
80’s
90’s
‘00
‘10
MWH +
INTERACTIVE
Improved
Outcomes
ENVIRONMENT
MOIST WOUND HEALING
PASSIVE
•Hydropolymers
•Hydrocolloids
•Collagen dressings
•Gels
•Saline wet gauze
PROMOTES HEALING
• Collagen/ORC dressings
•Growth factors
• Interactive Biopolymers
• GF/Device combinations
• Pharmaceuticals
• Tissue Engineering
TRADITIONAL
•Gauze
•Sponges
70 + Years - First Wave
15+ Years - Second Wave
Deals with Symptoms:
Effective on large patient cohorts
Third Wave
The need for Diagnostics
Advanced therapies have improved outcomes….but only on subsets of
the population to whom their mode of action is appropriate
NPWT
Improved Outcomes
Growth
Factors
Collagen
Collagen/ORC
Collagen/ORC
Targets
Healing
THE GAP - TARGETING – DIAGNOSIS & SELECTION
Contemporary Wound Care
e.g. Foams, Gels, Hydrocolloids
General Wound Care
e.g. Textiles and Gauze
Applicable wounds
Targets Exudate
Management
Targets Exudate
Absorbency
Standard of Care?
• Treatments are often chosen based on local traditions
• Wet-to-dry gauze dressings are the most widely used primary
dressing material in the USA and may be erroneously considered a
standard of care
• In a review of the literature, Ovington notes that the following can
impede healing and represents good reasons to abandon this
traditional dressing technique:
•
•
•
•
Local tissue cooling
Disruption of angiogenesis by dressing removal
Increased infection risk from frequent dressing changes & strike through
Prolonged inflammation
Hansson C. Interactive wound dressings: a practical guide to their use in older patients. Drugs aging 1997 Oct;11(4):271-84 McCallon ST, Knight CA,
Vallulus P, et al. Vacuum –assisted closure versus saline-moistened gauze in the healing of post-operative diabetic foot wounds. Ostomy Wound
Management 2000;46(8): 28-34 Ovington LG. Hanging wet to dry dressing out to dry. Home Health Nurse 2001;19 (8):1-11
Passive and Active WOUND MANAGEMENT
PASSIVE WOUND MANAGEMENT
ACTIVE WOUND MANAGEMENT
MANAGEMENT BASED ON VISIBLE
WOUND BED CHARACTERISTICS:
COLOR, DEPTH AND EXUDATE LEVELS
INTEGRATED MANAGEMENT BASED ON DELAYED
HEALING CHARACTERISTICS:
↑INFLAMMATION, ↑PROTEASES, ↓GROWTH
FACTORS, ↓CELL NUMBERS
Dry Wound
Wet Wound
Reduce Microbial
Burden
Hydrogels
Reduce Microbial
Burden
Silver
Collagen/ORC Silver
Exudate Absorber:
Alginate, Foam
Reduction /
Removal of
Protease Activity
Collagen/ORC
Dressing
Silver / Antimicrobial
Maintain Moist
Wound
Environment
Advanced Dressings
that Maintain Moist
Environment
Carrie Sussman, Barbara Bates-Jensen. “Wound Care A Collaborative Practice Manual for Health Professionals. Baltimore, MD, 2007. 246-47 Print.
Falanga V. The Chronic Wound: Impaired Healing and Solutions in the Context of Wound Bed Preparation. Blood Cells and Diseases, 2004;32:8894.
59
Healing Neuropathic Ulcers: Results of a Meta-analysis
Weighted Mean Healing Rates
•This data provide clinicians with a realistic assessment of
their chances of healing neuropathic ulcers
•Even with good, standard wound care, healing neuropathic
ulcers in patients with diabetes continues to be a challenge
Margolis et al. Diabetes Care. 1999;22:692.
Continuing Research: Healing of Diabetic Foot Ulcers
After 4 Weeks
Wounds achieving less than 53% closure at week 4 have minimal
chance of healing with conventional therapy
Sheehan et al. Diabetes Care. 2003;26(6):1879-1882.
Association Between PAR at Week 4 & DFU Closure at
Week 12
N=133
N=117
Data was dichotomized by PAR of <50% or ≥
50% by week 4 to assess the association of
PAR with DFU closure by 12 weeks
Active therapies
63
Active therapies
• Treatments that affect the underlying pathophysiology to help
heal wounds:
• Biomaterials – collagen; collagen/ORC
• Growth factors - PDGF
• Tissue engineering: Scaffolds; dermal equivalents; skin equivalents
• One thing they all have in common
• They are very effective on a sub-group of patients
Wound HealingWhat are the underlying defects?
Benefits of Collagen for Wound Healing
Collagen is a family of proteins with 28 members
Found in all groups of animals & highly conserved between species
Is most abundant protein in animals ; 1/3 of total protein = Collagen
Haemostat – stops bleeding
Enhances the deposition of new collagen fibres
Reduces wound contraction
Substrate for cellular adhesion and migration
Breakdown products - peptides & amino acids can be reused by cells
Collagen proteins & peptides stimulate cells - chemotactic for
neutrophils, macrophages, and fibroblasts
Can act as a sacrificial substrate for excessive MMPs
Beneficial for wound healing
Purna SK, Babu M. Collagen-based dressings –a review. Burns 26(2000):54-62
Benefits of ORC for Wound Healing
Cellulose is the most abundant biomass on the surface of earth
Oxidation is a chemical modification that makes cellulose biodegradable
Degrades in a predictable & consistent manner
Degradation occurs by fluid absorption & subsequent gelling
ORC degrades to sugars (glucose & glucuronic acid) when wet by either wound
exudate or with saline
Haemostat – stops bleeding & used in products such as SURGICEL®
ORC lowers pH as it breaks down which helps control bacterial growth
Studies in vitro have shown that ORC stimulates cell proliferation &
growth factor protection
Breakdown products – sugars which act as nutrients
Inactivates proteases such as Elastase
Beneficial for wound healing
Collagen/ORC
Collagen /ORC (+Silver) rebalances the
chronic wound environment
Binds and inactivates proteases
Both MMPs and Elastase
Protects growth factors
From proteolytic degradation
Stimulates cell growth
Fibroblasts, Endothelial cells & Keratinocytes
Controls bacterial bioburden
ORC lowers pH; Silver is antimicrobial
Improves Clinical Outcomes
Collagen/ORC Evidence
CLINICALLY AND SCIENTIFICALLY PROVEN
Meta analyses
Level 1
7
5
Level 2
20
Clinical Trials (569 patients)
Cohort studies, Clinical research
Case series, Case studies
Editorials, opinions
Level 3
3
>50
Lab Studies
Collagen/ORC Reduces Elastase
Collagen/ORC significantly better than other collagen only containing
dressings on inactivating Elastase Activity
Onugha N & Jones AM. Br J Nursing 2003; 11(5): S14-20
Noble T. J Wound care 2006;15(8): 368-371
How can we improve clinical outcomes
The future
71
Standard of Care
So why are Advanced Wound Therapies not standard of care?
The Problem with Current Advanced Therapies
Unreliable product outcome – doesn’t always result in healing
Results in a perceived lack of efficacy
Due to higher cost, product gets niched into a ‘last chance’ therapy
Current Understanding
New Advanced Technology more expensive
Needs more clinical evidence to drive product adoption & appropriate usage
Only endpoint considered is total healing
Required Outcome for New Therapies
Need to prove clinical effectiveness
Reliability – know when to use and when not to use
Choice of Wound Therapies
MANAGEMENT BASED ON VISIBLE
SIGNS & SYMPTOMS:
MANAGEMENT BASED ON
UNDERLYING BIOLOGY:
COLOR, DEPTH, EXUDATE LEVELS
INFLAMMATION, PROTEASES, GROWTH
FACTORS, CELL BEHAVIOR, BIOFILMS/
MICROBIAL BIOBURDEN
Dry Wound
Hydrogels
Inflammation
Proteases
Wet Wound
Exudate Absorber:
Alginate, Foam
PDGF
Growth factors Platelet releasates
Infected Wound
Necrotic Tissue
Anti-inflammatories
Collagen/ORC dressings
Silver / Antimicrobial
Cell growth
Skin equivalents
Dermal substitutes
Surgical debridement
Bacterial
bioburden
Antimicrobial products
Selection of Wound Therapies
When we cannot see the underlying problem
Diagnostic tests could help determine defect
& selection of appropriate therapy
Right Wound
Right Time
The Targeted Approach
Treatments need to become more targeted
If proteases are high - use a protease modulator
If wound is infected – use an antimicrobial
If no granulation tissue - use growth factors or tissue replacements
Need to learn more about the underlying wound pathogenesis so we
can sub-categorise wounds appropriately
This will drive the need for predictive diagnostic markers to know
when to use these more targeted products and when not to
Targeted products used appropriately will improve clinical efficacy
This approach has been used & validated in other disease states
Predictive Markers Used in Other Disease States
Predictive markers are in routine use today
Prominent examples:
HER2 Tissue Assay required as prerequisite to therapy to
screen for potential “responders” to Herceptin therapy
Hormone receptor status a prerequisite for Tamoxifen
therapy
BCR-ABL testing to predict successful Gleevec therapy
This approach improves clinical outcomes
(& reduces overall treatment cost)
Could Diagnostics Help in Wound Care?
Indicator
• Highlights a potential problem
• Wound colour, pH, temperature
Diagnostic marker
• Measures a biomarker which diagnoses a disease state
• Bacterial number, Biofilms, Virulence factors
Theranostic
• Measures a biomarker which can predict when a specific therapy should be used
• Proteases – Protease modulating dressings
• Growth factors – growth factor therapies
• Nitrates – dietary supplements
The Ideal Diagnostic Tool
To maximize their usefulness and potential for improving the treatment of
wounds, new diagnostic tools must be:
Appropriate for use by clinicians with different skill sets
Quick and easy to use
Be non-invasive and make use of a consistent sample that is easy to collect
and requires no sample preparation
Be used at the point of care (POC)
Be self-contained and not require expensive dedicated hardware
Improve clinical efficacy in a cost-effective manner
POC testing already in existence
Diagnostics and Wounds: A consensus document
World Union of Wound Healing Societies, MEP Ltd. London, 2008
Potential Markers for Chronic Wounds
Infection
Healing
Bacterial load
Microbial species
Biofilms
Host response
Bacterial resistance
Proteases
ECM proteins
Inflammatory mediators
Nitric oxide
Growth factors
Markers
Physical /Chemical
Temperature
pH
Size
Pressure
Colour
Smell
Diagnostics and Wounds: A consensus document
World Union of Wound Healing Societies, MEP Ltd. London, 2008
Preventative Measures
Genetic markers
Genetic polymorphisms
Neuropathy
Wound Diagnostics in Practice
The Challenges
Considerable research required to validate markers
Need to understand what the information is telling us
Need interventions based on these markers to correlate with meaningful
clinical benefits
Current Status
Today we have numerous wound dressings / treatments available
However, we don’t know when to use to gain maximum benefit
The Opportunity
Determine appropriate use of existing products
Develop new products which correct an underlying defect
Proteases as Predictive Markers
Current Understanding
Proteases at appropriate levels are important for wound healing
Elevated Protease Activity (EPA) has a negative impact on wound healing
Protease modulating therapies can help to rebalance high protease levels
Our Approach
Clinical study correlating clinical outcome with protease activities
Wound fluid samples collected pre & post treatment with Collagen/ORC
Outcomes
Inflammatory proteases correlate strongly with healing status
Protease activities reduced when wounds are in a healing trajectory
Wounds with EPA are non-healing & require intervention
A Protease POC Test could help
guide clinicians to an appropriate
targeted therapeutic pathway
The key benefits of PoC Diagnostic Test
Decrease time to decision making
Quick turnaround time
Reduced follow-up visits
Simple to use
Decentralised usage – clinicians’ office, clinics, home
Compact – don’t need specialised equipment / personnel in
clinical laboratories
Improved therapeutic decision making
Enable better treatment management
Improved clinical outcomes – improved efficacy
Reduced overall healthcare costs
Study Design
4 wound healing centres in the USA.
Wound swabs were taken from chronic wounds.
The swabs were frozen and sent to laboratory for
measurement of inflammatory protease activity.
Wound status was calculated according to the %
reduction in wound area over the previous 4 weeks.
A wound considered in a healing trajectory if over 4 wks:
≥50% reduction in wound area for DFUs or
≥30% reduction in wound area for VLUs & PU
Defining EPA
200
450
180
Elastase Activity (mU/110ul)
500
400
MMP Activity (U/110ul)
Clinical Range of Protease Activity
When is high too high?
We must understand
correlation and impact to
healing
350
300
250
200
150
160
140
120
100
80
60
100
40
50
20
0
0
0
50
100
150
200
250
0
All chronic wounds (n=236)
50
100
150
200
250
Probability healing decreases with excess proteases
140
60
80
60
40
40
30
20
10
20
0
50%
MMP
MMP
Time
55%
60%
Elastase
HNE
0
65%
70%
75%
80%
85%
90%
95%
100%
Healing wound
Non-healing wound
n=93
Probability of a Non-Healing Wound
Serena T, Cullen B, Bayliff S, Gibson M, DeMarco D, Galbraith J, Le N, Mancinelli M, Sabo M, Samies J. Protease
activity levels associated with healing status of chronic wounds. Wounds UK, Harrogate, 2011
Elastase Activity (mU/110uL)
100
50
Protease Activity
MMP activity (U/110uL)
120
Defining EPA (elevated protease activity) associated with non-healing
chronic wounds
Defining the “elevated” in EPA through statistical analysis
A chronic with EPA has a 90% probability it won’t heal (without appropriate intervention)
160
HNE
Elastase
n=93
180
120
100
80
60
160
140
120
100
80
60
40
40
20
20
0
40%
0
50%
60%
70%
80%
Probability of a Non-Healing Wound
Serena T, Cullen B, Bayliff S, Gibson M, DeMarco D, Galbraith J, Le N, Mancinelli M, Sabo M, Samies J. Protease
activity levels associated with healing status of chronic wounds. Wounds UK, Harrogate, 2011
90%
100%
Elastase Activity (mU/110uL)
MMP
MMP
90% probability of a
non healing wound
MMP activity (U/110uL)
140
200
Correlation with Healing Status (n=163)
Elastase Activity
MMP Activity
200
450
Non-healing chronic wounds
400
with
EPA
180
350
Total MMP Activity (U/110ul)
Elastase Activity (mU/110ul)
160
140
120
100
80
60
300
250
200
150
100
40
20
50
0
0
Healing
Non-Healing
Healing
Non-Healing
Correlation Between MMP & Elastase Activity (n=236)
500
450
MMP Activity (U/110ul)
400
350
300
250
200
150
100
50
0
0
20
40
60
80
100
120
Elastase Activity (mU/110ul)
140
160
180
200
Detecting EPA No visual cues
NEW DATA PUBLISHED:
THE IMPORTANCE OF PROTEASES IN WOUND HEALING AND WOUND
ASSESSMENT
Snyder et al.
There are no visual cues to
detect EPA
Detecting EPA No visual cues
In summary
Proteases
Proteases are important, but detrimental when in excess
How we measure protease activity
We can control/reduce protease activity in chronic wounds
Targeted & Early adoption significantly improves outcomes
As our understanding of wound pathogenesis increases
Identification of new predictive markers
Development of POC tests linked to current products
Development of new targeted products
Reset the standard of care in treating wounds
Smaller cohorts of patients for individual therapies
Increase efficacy with existing & new products
Increase understanding of wound healing
Personalised Medicine Can Revolutionise Wound Care