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The Microenvironment of DFU. Mamdouh Radwan El-Nahas Professor of Internal Medicine Diabetic foot team Diabetes and Endocrinology Unit Mansoura University. What happens when wound occur in the skin. wound healing start immediately and can be categorized into 4 stages. Coagulation

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The Microenvironment of DFU

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The microenvironment of dfu l.jpg

The Microenvironment of DFU

Mamdouh Radwan El-Nahas

Professor of Internal Medicine

Diabetic foot team

Diabetes and Endocrinology Unit

Mansoura University


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What happens when wound occur in the skin

wound healing start immediately and can be categorized into 4 stages.


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  • Coagulation

  • Inflammation

  • Cellular proliferation

  • Remodelling


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Haemostasis


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Remodelling

Provisional wound

matrix

Mature scar

consists predominately

of fibrin and fibronectin

collagen molecules

(type III, type I)

cross-linked

by enzymatic action

MMPs


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Matrix metalloproteinases (MMPs)

Plasmin

(-)

Active form

Matrix degradation

Inactive form

tissue inhibitors of metalloproteinases


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The chronic wound is not the acute wound


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Lessons learned from acute wound healing cannot be applied to chronic wound.


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Cellular and molecular abnormalities of Chronic wound

  • Overproduction of the inflammatory cytokines e.g. TNF-α

  • Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts

  • Excessive amounts of MMPs.

  • Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.


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So, for healing to occur, we need to change the environment of chronic wound toward that of acute wound.


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Cellular and molecular abnormalities of Chronic wound

  • Overproduction of the inflammatory cytokines e.g. TNF-α

  • Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts

  • Excessive amounts of MMPs.

  • Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.


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The microenvironment of Chronic wound

  • Overproduction of the inflammatory cytokines e.g. TNF-α

  • Cellular abnormalities: Defective PNL & Macrophages and senescent fibroblasts

  • Excessive amounts of MMPs.

  • Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.


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Exudates from chronic wounds contain very high levels of inflammatory cytokines and proteases.

Removal of the excess exudates can be accomplished by:

  • A foam or an alginate dressing

  • VAC (vacuum assisted closure) device.


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The ancient Egyptian discovery7000 years ago

The ancient Egyptians used a combination of:

  • honey

  • lint

  • animal grease

  • Others

Sekhmet Netjert

(Goddess) of Healing


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The microenvironment of Chronic wound

  • Overproduction of the inflammatory cytokines e.g. TNF-α

  • Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts

  • Excessive amounts of MMPs.

  • Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.


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Debridement

In microenvironmental terms we can think of Debridement as removal of old cells giving space to new cells to start wound healing.


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Cell therapy with bioengineered skin

  • Using living fibroblasts and keratinocytes from neonatal foreskin.

  • The mechanisms of action of bioengineered skin might involve increased availability of growth factors, and perhaps recruitment of stem and progenitor cells to the wound site.


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Stem cell therapy

  • There is great interest in delivery of stem or progenitor cells, either applied topically or recruited from the circulation.

  • Some preliminary work suggests that topically applied autologous bone-marrow cultured cells can heal human chronic wounds.


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Using electricity to revert cells into their normal behavior

  • High-voltage, pulse-galvanic electric stimulation enhances wound healing (Peters et al 2001).


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low-level Laser therapy

low-energy laser has a stimulating effect on cell mitosis, keratinocyte migration, proliferation and cytokine production and it may lead to increased dermal angiogenesis


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Topical Phenytoin

  • The gingival hyperplasia appear during phenytoin therapy, raise interest in its use to prompt wound healing.

  • Habibipour et al (2003) showed that phenytoin treated wounds had significant increase in collagen deposition and neovascularization.

  • Shaw et al (2007) reviewed the effectiveness of topical phenytoin on wound healing and concluded that it had positive effect on wound healing in a variety of wounds including DFU


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The microenvironment of Chronic wound

  • Overproduction of the inflammatory cytokines e.g. THF-α

  • Cellular abnormalities: Defective PNL and Macrophages senescent fibroblsts

  • Excessive amounts of MMPs.

  • Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.


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Inhibitors of MMPs

  • Tetracycline derivatives can reduce the activity of MMPs

  • Supporting this concept, an initial report of a randomized controlled trial showed improved healing of chronic diabetic foot ulcers treated with a topical Doxycycline gel (Chin et al 2003) .


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  • Metallic ions and citric acid e.g Poly Hydrated Ionogen positively restore MMP ratios within chronic wounds.

  • Dressing consisting of metal ions and citric acid (Dermax) decrease MMP-2 production in vitro (van den Berg 2003)

  • Pirayesh et al (2007) reported efficacy of PHI in the treatment of DFU.


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Silver

Silver-containing dressings are effective in sequestering matrix metalloproteinase-2 and -9 (walker et al 2007).

Walker et al: In vitro studies to show sequestration of matrix metalloproteinases by silver-containing wound care products. Ostomy Wound Manage. 2007 Sep;53(9):18-25.


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The microenvironment of Chronic wound

  • Overproduction of the inflammatory cytokines e.g. TNF-α

  • Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts

  • Excessive amounts of MMPs.

  • Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.


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Growth factors

PDGF gel (Regranex) improved healing quality, enhanced angiogenesis, cell proliferation and epithelialization (Li et al 2007).


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But the effectiveness of PDGF is far below our expectations

  • Senescent cells, which may be unresponsive to growth factors.

  • excessive amount of proteases that have been shown to be capable of destroying PDGF.

  • There is a need to improve these results with growth factors. Greater efficiency of delivery of growth factors, by gene therapy or by cell therapy, is now possible and being tested.


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Epidermal growth factor (EGF)

Recombinant human epidermal growth factor (REGEN-D™ 150) has been found to result in healthy granulation and stimulate epithelization (Mohan 2007).


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VEFG

Successful in experimental animals (Galeano et al 2003) but clinical trials using VEGF therapy did not succeed in ameliorating healing as expected (Yla-Herttuala 2006)


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Conclusions


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  • Optimum healing of a wound requires a well-orchestrated integration of complex cellular and molecular factors.

  • It is a complex process that need appropriate and precise cellular response to: inflammatory mediators, to growth factors and cytokines.


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The chronic wound is not the acute wound

  • In chronic wounds the progression of the healing process is impaired and the wound usually stuck in the inflammatory stage.


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  • Enhanced understanding and correction of pathogenic factors, combined with stricter adherence to standards of care is giving new hope to the problem of impaired healing.


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Successful Treatment of DFU depends on how we understand the complex and dynamic interaction of multiple factors that contribute to chronicity of the wound.


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Only then, when we put together what we

‘take off the wound’ (pressure)

with

what we ‘put on’ the wound (advanced dressings)

will we see any real improvement in wound healing

David Armstrong


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Thank you


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