A1 Wound Healing[1]

SURGERY I WOUND HEALING © UST Medicine WOUND REPAIR •effort of the tissue to restore normal function and structure after injury •to reform barriers to fluid loss and infection •limit further entry of foreign organisms and materials •re-establish normal blood and lymph flow •restore mechanical integrity

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REGENERATION

•perfect restoration of the preexisting tissue architecture without scar formation

•ideal •can only be found in embryonic tissue, bone and liver *All wounds undergo the same series of events. *The phases overlap in both time and activity. ACUTE WOUNDS • orderly • timely • to achieve restoration of structure and function

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CHRONIC WOUNDS • does not proceed to a restoration of functional integrity • prolonged due to inflammatory phase • does not proceed to closure

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WOUND CLOSURE TYPES 1. PRIMARY/ FIRST INTENTION

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closures that are immediately sealed with simple suturing Ex: simple suturing, skin graft, flap closure

highly contaminated wound closed by reepithelialization and contraction of wound

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contaminated wound initially treated with debridement or antibiotics for several days

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when ready for closure  surgical interventions Ex: simple suturing, skin graft, flap closure * Clinically, as the first phase of healing evolves, the area will have increased temperature (warmth), some local swelling and feel firmer, and in response the surrounding skin will often show a color change of red or dark brown to purple as metabolic activity of the area increases.

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PROLIFERATIVE/ REGENERATIVE / REPARATIVE PHASE • reepithelialization , matrix synthesis and neurovascularization MATURATIONAL / REMODELING PHASE • period of scar contraction with collagen cross-linking, shrinking and loss of edema

I. INFLAMMATORY PHASE A. Hemostasis and Inflammation • represents tissue's attempt to limit damage by:

collagen to platelets  platelet aggregation and activation of the coagulation pathway exposure of types IV and V collagen  platelet aggregation initial contact between platelets and collagen requires vWF initial intense local vasoconstriction of arterioles and

plugging of capillaries with erythrocytes and platelets

platelet adhesion to the endothelium is principally mediated through the interaction between highaffinity glycoprotein receptors and the integrin receptor GPIIb-IIIa (αIIbβ3) platelets express other integrin receptors that mediate direct binding of collagen (α2β1), laminin (α6β1), or indirectly by attaching to subendothelial matrix-bound fibronectin (α5β1), vitronectin (αvβ3), and other ligands

B. Increased Vascular Permeability

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binding  changes in platelet conformation  intracellular signal transduction pathways  platelet activation and release of biologically active proteins

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WOUND HEALING PHASES 1. INFLAMMATORY / REACTIVE PHASE • aimed at limiting the amount of damage and preventing further injury 2.

blood vessel damage  exposure of subendothelial

 adhere to the damaged capillary endothelium  cessation of hemorrhage

3. TERTIARY/ DELAYED PRIMARY CLOSURE

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characterized by: 1. increased vascular permeability 2. migration of cells into the wound by chemotaxis 3. secretion of cytokines and growth factors into the wound 4. activation of the migrating cells

capillaries  vasodilation and increased vascular permeability

2. SECONDARY/ SPONTANEOUS INTENTION • no active intention to close the wound

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stopping the bleeding sealing the surface of the wound removing any necrotic tissue, foreign debris, or bacteria present

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platelet α granules contain: a. platelet-derived growth factor (PDGF) b. transforming growth factor (TGF)-β c. insulin-like growth factor (IGF)-l d. fibronectin e. fibrinogen f. thrombospondin g. vWF dense bodies  vasoactive amines (serotonin)  vasodilation and increased vascular permeability mast cells  histamine and serotonin  leakage of plasma from the intravascular space to the extracellular compartment activated platelets  membrane phospholipids bind clotting factor V  interaction with clotting factor X  membrane-bound prothrombinase activity  thrombin production

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thrombin activates platelets and catalyzes the formation of fibrinogen into fibrin

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fibrin strands trap red blood cells, forming the clot, and seal the wound

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thromboxane A2 and prostaglandin F2α assist with platelet aggregation and vasoconstriction

C. Polymorphonuclear cells ▫ are activated in acute inflammation. ▫ they appear from day 0-5 ▫ Promote phagocytosis ▫ They are attracted by the chemicals in plasma and on injured tissues

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pro-inflammatory cytokine, an acute-phase- response cytokine o detectable within the first 24 hrs, peak between 72 hrs and then rapidly decline throughout the first week o causes lymphocyte activation and stimulation of hypothalamus febrile response o directly affects hemostasis by causing release of vasodilators and stimulating coagulation o effects: enhancement of collagenase production, stimulation of cartilage degradation and bone reabsorption, Europhile activation, adhesion molecule regulation and promotion of chemo taxis o also promotes other cells to secrete proinflammatory cytokines o effects also extend into proliferate phase, increasing fibroblast and Microbial bykeratinocyte growth and TNF-α collagen synthesis o presence after 1 week IL-6 chronic Macrophage inflammation/ injury

Enters the injured area and clean up foreign material, bacteria and dead cells. Migration of PMN’s stops when wound contamination has been controlled. They do not survive longer than 24 hours. After 24-48 hours mononuclear cells predominates in wound healing. PMNs are not essential to wound healing because their role in phagocytosis and antimicrobial defense may be taken over by macrophages. Sterile incisions heal normally w/o PMNs. Increase vascular permeability and other chemotactic factors facilitate diapedesis of neutrophils into the inflammatory cells. Diapedesis- a passage of intravascular cells through vessel walls and into the extravascular space of the wounds. With the combination of vasodilatation and increase vascular permeability leads to clinical findings of inflammation: o Rubor, o Calor o Tumor o Dolor After extravasation, PMNs migrate through the ECM by transient interactions with integrin receptors and their ligands. Four phases of integrin mediated cell motility: o Adhesion o Spreading o Contractility or Traction o Retraction

o IL-1

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IL-8

TNF-α

Chemotactic for the cellular components of inflammation • Upregulates cell surface adhesion molecules (promote interaction of immune cells and endothelium. • Detected in the wound within 12 hours after acquisition of wound. • Peaks after 72 hours EFFECTS • Hemostasis, increased vascular permeability, increased endothelial proliferation. • Induces fever, increased collagenase production, cartilage and bone reabsorption and release of PDGF • Excessive: MOF due to activation of macrophages and neutrophils. •

Growth Factors PDGF TGF-α TGF –β EGF FGF

KGF IGF-1 VEGF

*abrenica

MACROPHAGES ▫ central to wound healing, serving to orchestrate the release of cytokines and stimulate many of the subsequent processes of wound healing. o Appear when neutrophils disappear o induce PMN apoptosis o chemo taxis of migrating blood monocytes occurs within 24 to 48 hours(factors: bacterial products, complement degradation products (C5a), thrombin, fibronectin, collagen, TGF- and PGDF-BB) o have specific receptors for IgG (Fc receptor), C3b (CR1 and CR3), and fibronectin (integrin receptors), which permit surface recognition of opsonized pathogens and facilitate phagocytes o bacterial debris monocyte to release free radicals and cytokines (angiogenesis and fibroplasias) ; with IL-2 increase free radicals and bacterial activity activation of monocytes o activation of monocytes and macrophage phospholipase enzymatic degradation of cell membrane phospholipids, releasing thromboxane A2 and prostaglandin F2

also release leukotrienes B4 (potent chemotaxin for Europhiles and increases their adherance to endothelial cells) and C4 and 15- and 5hydroxyeicosatetr aenoic acid release proteinases, including matrix metalloproteinases (MMP-1, MMP-2, MMP-3 and MMP-9) degrade ECM and are crucial for removing foreign material, promoting cell movement through tissue spaces and regulating ECM turnover secrete numerous cytokines and growth factors

IFN-γ

IL-6 • • •

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Acute wounds: secreted by PMNs and fibroblasts Rise parallels the increase in PMN counts locally From monocytes and macrophages Involved in stem cell growth, activation of B and T cells, hepatic acute-phase protein synthesis regulation. Detectable within 12 hours of experimental wounding Persist at high concentrations for longer than a week Works synergistically with IL-1, TNF-α and endotoxins Potent stimulator of fibroblasts proliferation that is decreased in aging fibroblasts and fetal wounds

IL-8 SURGERY WOUND HEALING Wound Manipulation

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Acute wound: secreted primarily from macrophages and fibroblasts with PEAK expressions within the first 24 hours MAJOR EFFECTS • Inrease PMN and monocyte chemotaxis • PMN degranulation • Expression of endothelial cell adhesion molecules • Increased keratinocyte proliferation

Has been used in the treatment of hypertrophic and keloid scars MAJOR EFFECTS • Macrophage and PMN activation • Increased cytotoxicity • Reduce wound contraction • Aid in tissue remodelling • Slows collagen production and cross-linking while collagenase production increases (MOA in scar Treatment)

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IFN-γ •

Proinflammatory cytokine from T lymphocytes and macrophages

Growth Factors MAJOR EFFECT • Stimulate fibroblast, endothelial cell and keratinocyte proliferation (important in Proliferative Stage) CYTOKINE (Growth Factors)

SOURCE

Platelet-derived growth factor

Platelets, macrophages, endothelial cells, keratinocytes

Transforming growth factorbeta

Platelets, T lymphocytes, macrophages, endothelial cells, keratinocytes, fibroblasts

Epidermal growth factor

Platelets, macrophages

Mitogenic for keratinocytes and fibroblasts; stimulates keratinocyte migration

Transforming growth factoralpha

Macrophages, T lymphocytes, keratinocytes

Similar to TGF-β

Fibroblast growth factor-1 and 2 family

Macrophages, mast cells, T lymphocytes, endothelial cells, fibroblasts

Chemotactic for fibroblasts; mitogenic for fibroblasts and keratinocytes; stimulates keratinocyte migration, angiogenesis, wound contraction and matrix deposition

Keratinocyte growth factor

Fibroblasts

Stimulates keratinocyte migration, proliferation and differentiation

Insulin-like growth factor-1

Macrophages, fibroblasts

Stimulates synthesis of sulfated proteoglycan, collagen, keratinocyte migration and fibroblast proliferation; endocrine effects similar to those of growth hormone

Vascular endothelial cell growth factor

Keratinocytes

Increases vasopermeability; mitogenic for endothelial cells

FUNCTIONS Chemotactic for PMNs, macrophages, fibroblasts and smooth muscle cells; Activates PMNs, macrophages and fibroblasts; mitogenic for fibroblasts, endothelial cells; stimulates angiogenesis and wound contraction; remodelling Chemotactic for PMNs, macrophages, lymphocytes, fibroblasts; stimulates TIMP synthesis, keratinocyte migration, angiogenesis, and fibroplasias; inhibits production of MMPs and keratinocyte proliferation; induces TGF-β production

LYMPHOCYTES IN WOUND HEALING

→ increases fibroblast infiltration

Lymphocytes -agranular leukocytes involved in the body’s immune system - 2nd most numerous among leukocytes

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Fibroblast growth/activating factors → chemotactic for fibroblasts → mitogenic for fibroblasts and keratinocytes → activation (fibrocyte →fibroblast)

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3. IL-4 → fibroblast proliferation, collagen synthesis

T- lymphocytes -appear in significant numbers (5th day) -peak occurrence( 7th day ) B- lymphocytes - no significant role in wound healing Fibroblasts - cells that makes the structural fibers and ground substance of connective tissue. Keratinocyte -the major cell type of the epidermis, making up about 90% of epidermal cells.

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T-lymphocytes’ effect is the production of: Stimulatory cytokines 1. IL-2

Inhibitory cytokines 1. TGF-β (Transforming Growth Factor – beta) → inhibits keratinocyte proliferation (but chemotactic to fibroblasts and causes fibroplasia) 2.

IFN-γ → retards and suppresses collagen synthesis and cross-linking ( collagenase activity) II. PROLIFERATIVE PHASE characterized by the formation of granulation tissue which consists of:

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capillary bed fibroblasts macrophages

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capillary maturation

loose arrangement of collagen fibronectin hyaluronic acid

Refer to the diagram below: • Following injury, the endothelium is exposed to soluble factors and comes in contact with RBC. • This results in the upregulation of the expression of cell surface adhesion molecules such as vascular cell surface adhesion molecule (VCAM-1). Matrix degrading enzymes are also released and activated, degrading the endothelial basement membrane.

1. ANGIOGENESIS process of new blood vessel formation which is necessary to support a healing wound environment overview: Injury ↓activated endothelial cells degradation of basement membrane of postcapillary venules ↓ migration of cells ↓division tubule or lumen formation ↓ deposition of basement membrane ↓

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Fragmentation of the basement membrane allows endothelial cell migration to the wound and this is promoted by fibroblast growth factor (FGF), platelet derived growth factor (PDGF) and TGF-β.

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Integrinαvβ3 – facilitates endothelial cell migration to the wound PECAM-1 – modulates their interaction as they migrate to the wound

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A f te r in j u r y : e n d o t h e l i u m e x p o s e d t o s o l u b le f a c t o r s a n d R B C V C A M -1

m a t r i x - d e g r a d i n g e n z y m e s ( p l a s m i n , m e t a l lo p r o t e i n a s e s ) d e g ra d e s b a s e m e n t m e m b ra n e F G F , P D G F , T G F -B in te g r in P E C A M -1 e n d o th e li a l c e ll m i g r a ti o n t o t h e w o u n d

Capillary tube formation: consists of cell-cell and cell-matrix interactions PECAM-1: mediates cell-cell contact (stabilized by B1 integrin receptors) Leads to the formation of arterioles and venules or will lead to involution and apoptosis Factors that stimulate angiogenesis: - TNF-α - orchestrates angiogenesis during the inflammation; promotes formation of capillary tube

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Heparin - stimulates the migration of capillary endothelial cells and binds to other angiogenic factors VEGF FGF-1 - provide the initial angiogenic stimulus within 1st 3 days of repair FGF-2 - days 4-7 TGF-β - chemoattractant for fibroblasts; ↑ FGF angiogenin IL-8 lactic acid

2. FIBROPLASIA – proliferation of FIBROBLASTS FIBROBLASTS ▫ specialized cells that differentiate from resting MESENCHYMAL CELLS ▫ normally quiescent (arrested in Go phase) and sparse ▫ upon injury: chemoattracted to the inflammatory site ▫ primary function: SYNTHESIZE COLLAGEN o begins during CELLULAR PHASE of inflammation o LAG PHASE of wound healing

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Time required for mesenchymal cells (undifferentiated) to differentiate into fibroblasts (highly specialized) Time delay of 3-5 days (depends on tissue type)

Accounts for time delay between injury and appearance of collagen on the healing wound Synthesis declines after 4 weeks

At this point, wound now enters the phase of COLLAGEN MATURATION Migrates in response to chemotactic factors: PDGF, TGFβ, TNFα, etc. 

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3. EPITHELIALIZATION EPIDERMIS ▫ Physical barrier to prevent: 1) fluid loss, 2) bacterial invasion ▫ Tight cell junctions: contribute to impermeability

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Basement membrane zone: structural support for epidermis and dermis

RE-EPITHELIALIZATION ▫ Begins within hours after injury ▫ Initial seal for the wound: blood clot  followed by epithelial cell migration (KERATINOCYTES) across the wound ▫ Process: o KERATINOCYTES – originally located at STRATUM BASALE: the epidermal layer full of active mitotic cells

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Travel from stratum basale to surface of wound Undergo a sequence of:

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Detachment – attachments to neighboring cells are loosened Migration – also phagocytoses cell debris along their path Proliferation Differentiation Stratification

If the BASEMENT MEMBRANE ZONE is damaged during the injury, its repair comes first before RE-EPITHELIALIZATION Epithelium rests upon the basement membrane. Therefore it is logical to for the basement membrane to be repaired first.

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Healing is faster if the basement membrane zone is not damaged

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KGF-2: topical application of this speeds up epithelialization in animals

NOTE: Extracellular Matrix • Scaffold to stabilize the physical structures of the tissue • Regulate cellular behavior of cells in contact with it • Composed of: – GAGs • forms the ground substance • allows the matrix to withstand compressive forces • Allows nutrients, metabolites and hormones to diffuse rapidly between the blood and tissue cells

Fibrous Proteins (Collagen, elastin, laminin, fibronectin) • Collagen - Strengthen and organizes • Elastin - Resilience and adhesion function Matrix accumulates, changing in composition as wound healing progresses – Balance between new deposition and degradation –

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General flow of events:

Provisional Matrix as scaffold (Fibrin, fibrinogen, Fibronectin, Vitronectin)

GAGs and Proteoglycan synthesis next

Further matrix deposition and remodeling

Collagen (predominant scar protein) •

Attachment proteins (Fibrin and fibronectin) provide attachment to ECM by binding to cell surface integrin receptors

Stimulation of fibroblast by GFs

Upregulation of cell surface intergrin receptors

Facilitation of cell-matrix interactions

Induces integrin clustering – “Focal Adhesion Sites” •

Cell signaling regulated by Mg2+, Mn2+, Ca2+ by inducing conformational changes

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Reciprocal relationship between Fibroblast and ECM • Fibroblast regulation is altered by ECM composition • Ex. Matrix-degrading protein MMP is upregulated after cytokine stimulation of fibrinoblast

Collagen • Found in all multicellular proteins • Long, stiff triple-stranded helix composed of 3 collagen polypeptide alpha chain – forms superhelix • Proline and Glycine-rich – Pro – provides stability – Gly – allows tight packing • Main constituents of CT are – Type I, II, III, V, XI – Type I – most common; skin and bones – Type III – increased expression in early wound healing

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Type I – –

Fibrin-forming collagen Secreted into ECM Collagen Fibrils Collagen Fibers

Other types: – Type IX & XII – fibril-associated collagens; found on surfaces of fibril to connect them to one another and to the ECM – Type IV & VII – network-forming

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IV – assemble to meshlike pattern; major part of mature BL

GAG’S AND PROTEOGLYCANS Glycosaminoglycans

–Unbranched polysaccharide chains composed of repeated disaccharide units - sulfated amino sugar (GalNAc/GluNAc) - uronic acid (glucuronic/iduronic) •Highly negatively charged •4 types: –Hyaluronan (HA)

–Chondroitin Sulfate & Dermatan Sulfate –Heparan Sulfate –Keratan Sulfate –Highly negative charge attratcs osmotically active cations

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•Function: mediated by both their core proteins and GAG chains. •GAGs  sulfonation Role of GAGS in proteoglycans •provide hydrated space around and between cells 2) form gels of different pore size and charge density Function of Proteoglycans •Chemical Signaling •Binds other secreted proteins ( proteases, protease inhibitors)

–Can be components of plasma membranes  Act as coreceptors ( binds cells to ECM) -

FIBRONECTIN o Have multiple domains and can bind to other matrix molecules & surface receptors o Animal embryogenesis o Soluble or fibrillar isoforms o Circulates in various body fluids o Enhances blood clotting, wound healing & phagocytosis

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BASAL LAMINA o Flexible, thin mats of specialized ECM o SKIN: basal lamina is connected to connective tissue (anchoring fibrils)

such as Sodium.

–Result: porous hydrated gels turgor (compressive forces) HYALURONAN •Simplest of the GAG’s •Composed of repeating nonsulfated dissaccharide units •Found in adult tissues •Prevalent in fetal tissues •Synthesized directly from surface of cell

HYALURONAN Role of HA •Wound healing –Physically expanding the ECM

–Reduce strength of adhesion of migrating cells •Cell migration (embryogenesis) –Cell free space PROTEOGLYCANS •Diverse group - # & type of GAG’s attached to the core vary greatly

VII – anchoring fibrils – help attach BL to underlying CT

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Basal lamina + collagen  Basement Membrane

Function of basal lamina •Molecular filter •Selective barrier to certain cells •Scaffold for regenerating cells to migrate •Tissue regeneration DEGRADATION OF ECM •Regulated turnover: crucial •Occurs during metastasis •Injury/infection •MMPs/ Serine proteases: degrade •Proteolysis is tightly regulated

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Collagen Synthesis Collagen polypeptides assembled at membrane-bound ribosomes then transported to ER Enter as Pro-alpha chains with Amino-terminal signal peptides and Propetides at N & C-terminal ends Amino-terminal signal direct Pro-alpha chains towards ER

Hydroxylation of some Pro and Gly = Hydroxypro & Hydroxygly Hydroxylation stabilizes triple helix through hydrogen bonding 3 Pro-alpha form Procollagen through H-bonding Procollagen secreted into ECM Cleavage of propeptides by proteases Formation of collagen monomers

Collagen Fibrils III. MATURATIONAL PHASE (~Day 8 - 1 or 2 years) Wound contraction is the centripetal movement of the whole thickness of the surrounding skin, reducing the amount of disorganized scar. Wound contracture is a physical constriction or limitation of function and is the result of the process of wound contraction. Contractures occur where excessive scar exceeds normal wound contraction resulting in functional disability. Ex. scars that traverse joints and prevent extension, scars involving eyelid and mouth causing ectropions Model of wound contraction (Ehrlich) • Fibroblast populated collagen lattice. • Fibroblasts adhere to collagen in culture. • Tractional forces caused be movement of the fibroblasts cause the lattice to contract. Wound contraction

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Fibroblasts become myofibroblast (stimulated cells with similar function and structure in common with fibroblasts and smooth muscle cells) • Myofibroblasts - produce smooth muscle actin fiber bundles called stress fibers. - develops contractile ability due to cytoplasmic actinmyosin complexes. - when placed in collagen lattice, contractions become faster! - colchicine (inhibits microtubules) and cytochalasin D (inhibits microfilaments) decreases contraction of collagen lattice. - constant feature in diseases with excessive fibrosis: hepatic cirrhosis, renal and pulmonary fibrosis, Dupuytren’s contracture, neoplasia-induced desmoplastic reactions. • Actin - appears on Day 5 and persists at high levels for 15 days, gone by 4 weeks. - arranged linearly along long axis of the fibroblast. • Fibronexus - attachment between cytoskeleton and ECM. • Stromelysin-1 (MMP 3)

- allows cleavage of attachment between fibroblast and collagen lattice so that lattice can be made to contract. - allows modification of attachment sites between fibroblast and collagen fibrils involving β1 integrins.

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TGF-β1 - affects contraction by increasing β1 integrin expression. Remodeling • ↓ fibroblasts • Dense capillary network regresses • ↑ wound strength w/n 1-6 weeks, then plateaus up to 1 yr after injury • Tensile strength only 30% compared with that of unwounded skin • ↑ breaking strength after ~21 days, due to crosslinking • Epidermodermal intraface is devoid of rete pegs that penetrate papillary dermis • Loss of anchorage results in increased fragility and predisposes to avulsion after minor trauma

ABNORMAL WOUND HEALING ▫ ▫ ▫ ▫ ▫ ▫ ▫ ▫

Amt of tissue lost or damaged Amt of foreign material/bacteria Length of time of exposure to toxic factors Intrinsic factors Chemotherapeutic agents Atherosclerosis Cardiac failure Location in body

Hypertrophic Scars and Keloids ▫ Proliferative scars ▫ Excessive collagen deposition ▫ Decreased collagen degradation ▫ MMP-1(collagenase) and MMP-9 (gelatinase) Keloids ▫ ▫ ▫

Grow beyond borders Rarely regress with time Occur above clavicles,UE, face

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Cannot be prevented

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Remain within orig Regress spontaneously Occur anywhere in the body preventable Perpendicular Flatter Narrower Less collagen formation

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Contraction of muscle cause gaping of wound More tension More scar formation Genetically predisposed to changes in ECM Switched on irreversibly by factors such as TGFB Multiple stimulatory effects Can be reversed, if stimulation is removed

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Appear to have problems in various stages of wound healing Elevated or depressed levels of cytokines, GF, or proteinases Wound fluid

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Greater levels of IL-1, IL-6, and TNF-α than acute wound fluid (these proinflam cytokines decreased as the wound heals)

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TNF-α INVERSELY proportional to essential growth factors (EGF & PDGF)

Proteolytic Degradation of ECM 

essential feature of repair and remodeling during cutaneous repair

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major cause of failure to heal in wound environment excessive proteolysis causes a release of high levels of breakdown products of connective tissue that will inappropriately activate inflammation increased inflammation of the wound:  LESS healing  collagen degradation is favored rather than synthesis

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 cellular production of ECM proteins cellular expression of integrins MMPs

synthesis of inhibitors of PAI andTIMP

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Therapeutic Intervention ▫ Antagonist of TGF-B and receptor ▫ Inhibition of collagen and ECM synthesis ▫ Cell cycle inhibitor ▫ IFN-y – supress collagen synthesis

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CHRONIC NON-HEALING WOUNDS

structurally related enzymes that can degrade ECM components differentiated by their substrate specificity

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degrade the adhesive substrates for cell migration and signaling molecules (GF & cytokines)

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INHIBITED by TI

TNF-α INCREASES its production, while INHIBITING TIMPs TNF-α levels in wound fluid inflammatory cells

** inhibition of MMPs results to: CHRONIC WOUNDS ex. pressure ulcers

MMPs (MMP-1, 2, 8, 9)

Chronic inflammation

TIMPs

Squamous cell carcinoma

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Development to squamous cell carcinoma in chronic burn scars Osteomyelitis Pressure sores Venous stasis ulcer Hidradenitis

irregular raised above the surface white, pearly discoloration

Pseudoepitheliomatous hyperplasia  pre malignant state  if this is reported on biopsy, the biopsy should be repeated because there may be squamous cell carcinoma present in other areas

Wounds appear DRUGS Doxorubicin (Adriamycin)

Direct inhibition of wound healing

Chemotherapeutic agents nitrogen mustard cyclophosphamide methotrexate BCNU Doxorubicin

Reduction in mesenchymal cell proliferation Reduction in platelets, inflamm cells, GF

Tamoxifen

Decrease cellular proliferation (may be due to decreased TGF-β

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Glucocorticoids

Decrease fibroblast proliferation and collagen synthesis Decreased amount of granulation tissue formed

Steroids

Stabilize the lysosomal membranes Decrease in breaking strength

NSAIDs (except for those in therapeutic range)

Delay healing

DRUGS –Exogenous drugs – inhibit wound healing –Potent wound healing inhibitors •Doxorubicin (Adriamycin) •Nitrogen mustard •Cyclophosphamide •Methotrexate •BCNU

–Reduce mesenchymal cell proliferation –Reduce platelets, inflammatory cells, growth factors DRUGS –Tamoxifen – anti-estrogen; decrease cellular proliferation

–Glucocorticoids – impair fibroblast proliferation and collagen synthesis. Amount of granulation tissue may also be decreased –NSAIDS – delay healing (effect on platelets)

•Bacteria prolongs inflammatory phase •Interferes w/ epithelization, contraction and collagen deposition •Neutrophils releases pro-MMP-8 •Fibroblasts and Macrophages express pro-MMP-1 & proMMP-9 •Bacterial Phospholipase C disrupts normal reepithelization Hypoxia Molecular Oxygen essential for collagen synthesis Ischemia prevents localized perfusion under hypoxic conditions Anemia- decrease in wound oxygen tension and collagen synthesis only when hematocrit levels <15% Smoking- induces vasoconstriction and increases CO that limits O2 carrying capacity of blood Diabetes

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Wound Infection Intact epithelium- prevents the bacterial contaminants normally present in the skin to gain entry into deep tissues Antibiotic prophylaxis- most effective when adequate conc. are present during time of incision Repeated Dosing- essential in decreasing postoperative wound Additional dose of Antibiotics-given for 24 hrs postoperatively in lengthy cases with prosthetic implants

Diabetic patients are prone to: •Tissue ischemia •Repetitive trauma •Infection Lymphocyte & Leukocyte function are impairedincreases collagen degradation and decrease collagen deposition Ionizing Radiation Endothelial Cell Injury causing atrophy, fibrosis and delayed tissue repair

Selection of Antibiotics for Prophylaxis •Depends on the type of surgery •Operative contaminants that might be encountered •Profile of resistant organisms •>105 microorganisms- risk of wound infection is increased

Angiogenesis is not initiated Cells on G2 phase through M phase are most sensitive to radiation

Bacterial count >105/g tissue or if a B-hemolytic strep are present- wound will not heal by any means including flap closures, skin graft replacement nor primary sutures

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Most common organisms responsible for wound infections are (in decreasing order): Staph. Aureus Coagulase (-) Strep Enterococci E.coli

Elderly patients

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Contamination- presence of bacteria w/o multiplication

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Colonization-multiplication w/o host response

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Infection-presence of host response in reaction to deposition and multiplication

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Surgical wound rupture Delayed healing Slower healing Collagen: qualitative and quantitative changes Dermal collagen content decreases Aging collagen: distorted architecture and organization Reduced re-epithelialization, decreased collagen synthesis, impaired angiogenesis Decreased Multiple growth factors including factors FGF-2 and VEGF Altered early inflammatory period – impaired macrophage activity, decreased phagocytosis and delayed infiltration of

Mechanism of wound infection SURGERY WOUND HEALING Wound Manipulation

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macrophages and B lymphocytes into wounds Reduced response to hypoxia (decreased MMP activity and TGF-B1 receptor expression in keratinocytes of elderly patients)

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Glucose balance is essential for wound healing.

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Iron, required to transport oxygen.

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Minerals, zinc, copper, are important for enzyme systems and immune systems. Zinc deficiency contributes to disruption in granulation tissue formation.

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Vitamins A, B complex and C, are responsible for supporting epithelialisation and collagen formation. It is also important for the inflammatory phase of wound healing.

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Carbohydrates and fats. These provide the energy required for cell function. When the patient does not have enough, the body breaks down protein to meet the energy needs. Fatty acids and essential for wound healing.

MALNUTRITION o

CHON catabolism delays wound healing

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Hypoalbuminemia (less than 2 g/dL) – delayed wound healing

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CHON supplements can reverse this deficiency

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Vitamins – cofactors

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Vitamin C deprivation (3 months) – delayed healing (Reversed by giving 100-1000g/day Vit. C)

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Vitamin A deficiency – impedes monocyte activation, fibronectin deposition (reduced cellular adhesion and TGF-B receptors)

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Vitamin A – for destabilization of lysozomal membrane; directly counteracts effects of glucocorticoids

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Vitamin K – main effect: synthesis of factors II, VII, IX, X

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Vitamin K metabolism is impeded by antibiotics

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Any impairment in the synthesis of Vit K can have an effect in healing because synthesis of some proclotting factors are dependent on the synthesis of Vit K

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Zinc: cofactor in RNA polymerase and DNA polymerase: deficiency results in delayed healing

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Iron: IDA can cause delayed wound healing (Ferrous ion: cofactor for the conversion of hydroxyproline to praline)

AGE: The physiological changes that occur with ageing place the older patient at higher risk of poor wound healing. Reduced skin elasticity and collagen replacement influence healing. The immune system also declines with age making older patients more susceptible to infection. Older people can also present with other chronic diseases, which affect their circulation and oxygenation to the wound bed. MEDICATION: Anti-inflammatory, cytotoxic, immunosuppressive and anticoagulant drugs all reduce healing rates by interrupting cell division or the clotting process. NUTRITION: Protein is required for all the phases of wound healing, particularly important for collagen synthesis.

Wound Manipulation ▫ Randomized studies (mid-1990’s) ▫ cytokines: TGF-ß, FGF-2, PDGF ▫ More rapid closure of venous stasis ulcers, pressure sores, diabetic foot wounds Future of Wound Healing –Continued research ▫ Elucidation of growth factors involved in:

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Äwound contraction & scarring Äangiogenesis

–Gene therapy –Tissue engineering Gene therapy ▫ Growth factor gene (e.g PDGF) is introduced to the wound via viral vectors. ▫ Enhances expression of genes at the site of injury ▫ Enhances skin regeneration (e.g. burns, genetic skin disease) ▫ Techniques: o Microarrays – rapid, large-scale gene expression o Differential-Display PCR – genetic screening tool Tissue Engineering ▫ Promotes regrowth of cells lost from trauma/ disease ▫ Restores, sustain and enhance tissues/organs ▫ Application of bioengineered skin containing dermal fibroblast to the wound ▫ (+) synthesis of cytokines by donor cells

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host’s skin cells regenerate Wound healing Scaffolds – support for tissue regrowth FDA- approved: treatment of diabetic and venous stasis ulcers

SURGERY WOUND HEALING Wound Manipulation

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