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.

1.Coagulation 2.Inflammation 3.Cellular proliferation 4.Remodelling

Haemostasis Stop Bleeding Platelet Degranulation Growth factorsSerotonin Provide Matrix for Cell Migration

Inflammation PNL Phagocytose Microorgan. Monocytes Tissue Macrophage phagocytosis Proteol. Enz GFs

Cellular Proliferation Fibroblast EC matrix Deposition Endothelial cells Neovascularization Keratinocytes Epithelialization

Remodelling consists predominately of fibrin and fibronectin collagen molecules (type III, type I) cross-linked by enzymatic action MMPs Provisional wound matrix Mature scar

Matrix metalloproteinases (MMPs) Inactive form Active form Plasmin tissue inhibitors of metalloproteinases Matrix degradation (-)

The chronic wound is not the acute wound

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

Cellular and molecular abnormalities of Chronic wound 1.Overproduction of the inflammatory cytokines e.g. TNF-α 2.Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts 3.Excessive amounts of MMPs. 4.Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.

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

Cellular and molecular abnormalities of Chronic wound 1.Overproduction of the inflammatory cytokines e.g. TNF-α 2.Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts 3.Excessive amounts of MMPs. 4.Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.

The microenvironment of Chronic wound 1.Overproduction of the inflammatory cytokines e.g. TNF-α 2.Cellular abnormalities: Defective PNL & Macrophages and senescent fibroblasts 3.Excessive amounts of MMPs. 4.Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.

Exudates from chronic wounds contain very high levels of inflammatory cytokines and proteases. Removal of the excess exudates can be accomplished by: 1.A foam or an alginate dressing 2.VAC (vacuum assisted closure) device.

The ancient Egyptian discovery 7000 years ago The ancient Egyptians used a combination of:  honey  lint  animal grease  Others Sekhmet Netjert (Goddess) of Healing

The microenvironment of Chronic wound 1.Overproduction of the inflammatory cytokines e.g. TNF- α 2.Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts 3.Excessive amounts of MMPs. 4.Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.

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

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.

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.

Using electricity to revert cells into their normal behavior High-voltage, pulse- galvanic electric stimulation enhances wound healing (Peters et al 2001).

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

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

The microenvironment of Chronic wound 1.Overproduction of the inflammatory cytokines e.g. THF- α 2.Cellular abnormalities: Defective PNL and Macrophages senescent fibroblsts 3.Excessive amounts of MMPs. 4.Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.

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).

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.

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 Sep;53(9):18-25.

The microenvironment of Chronic wound 1.Overproduction of the inflammatory cytokines e.g. TNF- α 2.Cellular abnormalities: Defective PNL & Macrophages and senescent Fibroblasts 3.Excessive amounts of MMPs. 4.Reduced concentration of growth factors e.g. PDGF, VEGF and TGF β.

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

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.

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).

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)

Conclusions

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.

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.

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.

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

O nly 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

Thank you