A Greek Drama in Three Parts

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A Greek Drama in Three Parts

• Acute inflammation
• Healing
• Chronic Inflammation

2
Inflammation and Healing Clinical Issues

• minor cuts, scarring red lines vs. red streaks
• protection vs. pathology
• mechanisms to interdict with drugs, including
  specific enzyme inhibitors, anti-cytokines, and
  soluble receptors.

3
Inflammation and HealingObjectives

• Use a process based approach building upon
  previous knowledge to develop the basic pathology
  of acute inflammation, chronic inflammation, and
  healing.
• Integrate elicitation and control with the
  cellular, tissue and systemic responses leading
  to clinical signs and symptoms.

4
Knowledge Base

• Histology Anatomy Microbiology
• Systemic and cell physiology
• Functions of the cells of innate and adaptive
  immunity
• Extracellular matrix, cytokines and chemokines
• Biology of acute and chronic inflammation
• Complement system elicitation and effects
• Gell and Coombs Hypersensitivities (biology)
• ABO/Rh blood group serology
• Lab medicine technologies RIA, ELISA,Western
  Blot, electrophoresis, IFE, Coombs test, etc.
• Path necrosis etc.

5
Acute Inflammation as a Process

• a very common, complex, stereotypic reaction of
  vasculature and cells to cell injury leading to
  the accumulation of fluid and leukocytes in
  tissues
• seen in normal wound healing
• is a normal aspect of innate immunity to
  infections where it helps contain and retard
  microbes, and improves focusing of antigen to the
  adaptive immune system

6
Acute Inflammation Pathology Instead of
Protection

• pathological if inappropriately triggered
  magnitude, duration, target
• allergy, and some autoimmune diseases (e.g. SLE
  or rheumatoid arthritis)
• induces local and systemic changes (liver, brain,
  and the immune system)
• several outcomes are possible including healing
  or "chronic inflammation"

7
Regulation

• Target Cell Responses
• enhanced by
• enhanced by guanylyl cyclase stimulation, e.g. by
  Ach or TxA2
• inhibited by
• adenylyl cyclase stimulation, e.g. by PGI2 or
  isoproterenol
• Overall Process
• Up regulated by sequential cascades of mediators
• eicosanoids, cytokines, proteins/peptides
• Down regulated
• clearing provocation, degrading mediators, enzyme
  inhibitors
• Mixed regulation
• neuroendocrine immunological triad
• cellular level release, response, cell
  development

8
What are the The Five Cardinal Signs of Acute
Inflammation ?

• heat (Calor)
• dilatation/permeability causes hyperemia, which
  raises extremities to core body temperature
• pain (Dolor)
• pressure and mediators irritate nerves
• redness (Rubor)
• hyperemia pools rbc in capillaries
• swelling (Tumor)
• exudate causes edema in interstitial tissues
• loss of function (Functio Laesa)
• changes in mircoenvironment interfere with
  function

9
Other clinical signs associated with inflammation

• mucus production
• (mast cells-histamine-mucus glands)
• smooth muscle contraction (spasmogens), e.g.
  bronchoconstriction
• systemic acute phase reactions
• elevated ESR (erythrocyte sedimentation rate)
• iron is sequestered (anemia of inflammation)
• fever (cytokines)

10
Vascular/tissue changes in Acute Inflammation are
typified by

• increased vascular permeability and vessel
  dilatation,
• a protein rich fluid (exudate) from the blood
  entering the tissue,
• cellular infiltrate the early arrival of
  neutrophils replaced later by macrophage and
  occasional lymphocytes, then fibroblasts for
  healing

11
Acute Inflammation is usually elicited by Tissue
Damage

• physical
• trauma e.g. knife wound or impact
• electromagnetic (heat, UV light)
• chemical
• simple, e.g. acids
• enzymatic, e.g. microbial or parasitic exotoxins,
  endotoxins
• ischaemic necrosis
• immunological
• ADCC, CTL, activated phagocytes
• mast cell/basophil triggering

12
Initial Results of Tissue Injury

• damaged tissue activates plasma enzyme systems
• broken or damaged blood vessels clot
• activated cells release proinflammatory mediators
• preformed histamine, serotonin, lysosomal
  enzymes
• newly synthesized cytokines, lipid products,
  nitric oxide
• neurological responses (pain)
• pressure, damaged nerves, prostaglandins,
  bradykinin

13
Acute Inflammation Triggered Without Direct
Tissue Damage

• stimuli activate cells to respond without first
  having significant tissue damage.
• by mast cell degranulation/activation or
  neutrophil activation
• Example Complement Fixation may lead to tissue
  damage

14
Interrelated Plasma Enzyme Systems Related to
Injury

• These cascading enzyme systems are interrelated,
  proinflammatory, and active during tissue injury
• Coagulation pathways
• Kinin system
• Fibrinolytic reaction
• Complement fixation
• Diagram follows

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Activation of Complement Cascades

• Classical pathway
• Binding of C1q (requires adjacent Fc regions) by
  immune complexes, or C reactive protein, etc.
  and activation by proteases e.g. plasmin
• Alternate pathway
• surfaces and substances that stabilize C3b and
  C3bB, e.g., Lps activation by proteases e.g.
  plasmin

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Biological Activities of Complement

• anaphylatoxins/ vascular permeability agents C3a
  and C5a mainly act by histamine release from
  mast cells
• chemotaxin C5a, also activates lipoxygenases of
  neutrophils and macrophage, and the release of
  free radicals thus enhancing the inflammation
• opsonin C3b
• cell lysis by MAC (C5-9)

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Activation of EndotheliumReceptors

• selectins and addressins (ligands for selectins),
  and integrins (ICAM and ICAM2) expressed in
  greater number or active form

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Activated Endothelium Releases Mediators

• releases mediators PAF (thrombosis) IL-1,
  IL-6/8, TNF-? (liver and brain) reduced amounts
  of NO (decreases granulocyte and platelet
  adherence and vascular tone)
• release of alpha chemokines attracts macrophage,
  e.g. macrophage chemotactic peptide-1 and beta
  chemokines, e.g. IL-8 are chemotactic for
  granulocytes.

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Activation of EndotheliumMorphology

• retraction of activated endothelium widens
  junctions between cells and allowing fluid loss
• fluid creates edema and effusion
• loss of fluid raises the protein concentration in
  capillary plasma

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Endothelial Retraction Effects

• vWF released, subendothelial collagen exposed
• platelets and fibrinogen adhere
• Damaged tissue releases Tissue Factor
  (thromboplastin), to initiate the cascade
• Thrombin is formed
• converts the soluble fibrinogen into insoluble
  fibrin
• direct effects on a variety of cells, e.g.
  activating endothelium
• activates Complement.

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Endothelium enters a Procoagulant State

• reduced levels of factors to discourage platelet
  aggregation and adhesion create a procoagulant
  state for the endothelium
• No longer releases factors PGI2, NO
  thrombomodulin decreases, procoagulant tissue
  factor increases.
• Retraction leaves the subendothelial matrix
  exposed, to which platelets may pavement
• onto the collagen/ vWF as does Hageman Factor
  (Factor XII).
• Aggregated platelets release proinflammatory
  factors.
• PAF, ADP serotonin...

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When Severe Damage of Endothelium Occurs

• Severely damaged vessels can lose endothelium
• thrombi form, may infarct
• healing takes longer

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Platelets

• adhere to exposed collagen VWF, and contribute
  to the hemostatic plug occluding small vessels.
• aggregate and adhere in response to
• thrombin, collagen, immune complexes, PAF

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Platelet Released Mediators

• cell growth factors
• serotonin and histamine (increased vasodilatation
  and permeability)
• epinephrine (release of neutrophils)
• Ca needed in the coagulation sequence, ADP
  PAF(a potent agent of vasodilatation and
  increased permeability and platelet aggregation)
• TXA2 (facilitates aggregation and
  vasoconstrictor)

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Blood Clot Terminology

• Hemostasis is a response to vascular injury, and
  leading to arrest of the hemorrhage, involving
  vasoconstriction, tissue swelling, the
  coagulation cascade, and thrombosis.
• Coagulation is the conversion of soluble plasma
  fibrinogen to insoluble fibrin polymer as
  catalyzed by the protease thrombin, and resulting
  from a cascade of reactions.
• Thrombosis, a blood clot in the circulation, is
  an aggregate of coagulated blood containing
  platelets, fibrin, erythrocytes, and leukocytes.

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Lipid Mediators of Inflammation
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Arachidonic Acid Metabolites

• Phospholipase A2 releases arachidonic acid
  from membrane phospholipids (inhibited by
  steroids), and goes into
• lipoxygenase pathway
• 5-HETE (chemotactic)
• LTB4 chemotactic for granulocytes and macrophage
  
• LTC4, LTD4, LTE4 potent vasopermeability and
  bronchial spasm
• cyclooxygenase pathway (inhibited by aspirin,
  indomethacin)
• PGI2 vasodilation, inhibits platelet aggregation
• TXA2 vasoconstriction, promotes platelet
  aggregation
• PGD2, PGE2, PGF2? vasodilation
• lipoxins (platelet 12-lipoxygenase on neutrophil
  LTA4)
• LXA4 vasodilation, reduces LTC4 vasoconstriction

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Inhibition of Arachidonic Acid Metabolism

• glucocorticoids inhibit genetic expression of
  cyclooxygenase, cytokines e.g. (IL-1 and TNF-?) ,
  and iNOS, and upregulate anti-inflammatory
  proteins e.g., lipocortin 1, an inhibitor of PLA2
  
• dietary fish oil, linoleic acid, makes less
  potent mediators than those from AA.
• specific COX-2 inhibitors
• COX aspirin, indomethacin, etc.
• COX-1 (homeostatic) and COX-2 (inflammatory)

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Basophils and Mast cells

• Similar to each other, but functional differences
  exist in responses of basophils, serosal and
  connective tissue mast cells

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Actions of Mast cells (and basophils)

• triggered by allergens, drugs, C3a C5a,
  cationic peptides, injury, ...
• primary mediators, in granules immediate
  reactions,
• edema, mucus, bronchial constriction, recruitment
  of granulocytes.
• newly synthesized secondary mediators from mast
  cells and infiltrating granulocytes, and direct
  effects of the granulocytes (neutrophils and
  eosinophils) constitute the late phase reaction
  in 2-3 hours.

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Lipid Mediators from Mast Cells

• PAF platelet activating factor aggregates
  platelets, histamine release, bronchial spasm,
  vascular permeability, vascular dilatation,
  chemotactic for eosinophils and neutrophils
• Arachidonic acid products
• lipoxygenase pathway
• LTC4, LTD4 potent vasoactive and spasmogenic
• LTB4 chemotactic for granulocytes and macrophage
• cyclooxygenase pathway
• PD2 vasoactive, mucus production

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Non lipid Mediators from Mast Cells

• Biogenic amines
• histamine bronchial spasm (smooth muscle
  contraction), vascular permeability, mucus
  secretion
• adenosine bronchial spasm, decreased platelet
  aggregation
• Chemotaxins/cell activators
• eosinophil chemotactic factor, neutrophil
  chemotactic factor
• Enzymes
• proteases and acid hydrolases that activate
  kinins and C
• Cytokines
• TNF-alpha, chemotactic for neutrophils and
  eosinophils IL1,3,4,5,6, gm-csf, chemokines

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Increased Vascular Permeability Produces an
Inflammatory Exudate

• activation/retraction of endothelium leads to
  increased vascular permeability
• histamine (and serotonin), PAF, bradykinin, LTC4,
  LTD4, LTE4 often begins in 10-15 minutes
• extravascular protein-rich exudate osmotically
  draws water
• includes fibrinogen (clotting and opsonin),
  globulins (antibodies), albumen
• fluid accumulation produces edema (and cutaneous
  wheal).
• edema (extravascular interstitial fluid) (or
  effusion in cavities) with cutaneous wheal

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Vasodilatation

• smooth muscle relaxes
• rapid histamine, serotonin
• slower nitric oxide, kallikrein, PGE2, PGI2,
  PGD2 (mast cells)
• opening of precapillary arteriole sphincters
  causes more flow and pooling of blood (hyperemia)
  in post capillary venules (creates flare on skin)
  
• Prostaglandins, histamine
• veinules relax as well

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Vascular changes alter blood cell movement

• Flow slows and stasis develops
• Instead of trains of wbc leading rbc, axial
  flow develops with a plasmatic zone
• activated leukocytes marginate and adhere to
  endothelium
• smaller vessels become packed with rbc (stasis)
  
• capillary fluid is lost, plasma becomes, high in
  protein (albumen and fibrinogen), viscous,
  increases erythrocytes tendency to form rouleaux
  (coin-like stacks)
• reduced dielectric constant due to increased
  albumin and fibrinogen (asymmetrically charged)
  coating that overcomes zeta potential and cells
  associate

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A neutrophil dominated infiltrate develops

• Mediators initiate neutrophil activation and
  chemotaxis
• neutrophils become the hallmark cell of the early
  acute inflammatory infiltrate.
• Neutrophils are attracted mainly by
• C5a, LTB4 and later by chemokines, TNF-?
• Bacterial infections provide n-formyl peptides
  e.g. FMLP.
• Neutrophil infiltration peaks at 6-24 hours,
  often release contents of lysozomes and secrete
  lipid mediators, which contribute to the clinical
  "late phase reaction (4hrs.) along with mast
  cells .

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Margination and Pavementing

• leukocytes localize outside the axial flow and
  become activated express cell adhesion molecules
• marginating neutrophils adhere due to increased
  contact and sticking to endothelial selectins on
  activated endothelium
• pavementing over an endothelial gap (neutrophil
  integrins) leads to extravascularization

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Emigration and Infiltration

• Diapedesis
• pseudopods lead, dissolving basement membrane and
  the neutrophils leave the vasculature through
  open gaps
• Transmigration (emigration)
• chemotactic signals draw leukocytes into tissues
  haptotaxis, movement along insoluble gradient,
  e.g.attractants on ECM

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Products from Neutrophils and Macrophage

• Eicosanoids
• 5-lipoxygenaseLTB4 (chemotactic), LTC4, LTD4,
  LTE4 (vasoconstriction, bronchospasm, and
  vascular permeability)
• from Lysosomes
• PLA2, proteases, myeloperoxidase, defensins,
  cationic proteins

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Products from Activated Macrophage

• Cytokines
• IL-1, IL-6, TNF, chemokines e.g. IL-8
• activate endothelium, liver (IL-1 and 6, TNF-?),
  brain (IL-1), IL-8 is chemotactic for
  neutrophils, and especially TNF, contribute to
  toxic shock.
• Other
• proteases, hydrolases, coagulation factors,
  Complement, growth factors (PDGF,
  EGF,FGF,TGF-beta), eicosanoids, nitric oxide,
  reactive oxygen metabolites
• Nitric oxide
• from macrophage and endothelium, relaxes smooth
  muscle (vasodilation), reduces platelet and
  neutrophil aggregation and adhesion

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Oxygen Derived Products (neutrophils)

• kill microbes, damage endothelial, rbc, and
  parenchymal cells inactivate antiproteases
  (which can lead to destruction of the ECM).
• A respiratory burst of oxygen consumption and HMP
  shunt support NADPH oxidase generation of
  superoxide (O2-), which is converted to H2O2 by
  superoxide dismutase.
• H2O2 reacts with myeloperoxidase plus halide
  (Chloride) to form hypochlorous acid (HOCl), the
  major bactericidal agent made by phagocytes
  (neutrophils, not monocytes).
• Enhanced by Fe2, H2O2 forms the potent hydroxyl
  radical (? OH).
• Nitric oxide (NO) reacts with oxidants to form a
  variety of toxic NO derivatives.
• Oxygen derived radicals are detoxified by
  ceruloplasmin, transferrin, superoxide dismutase,
  catalase glutathione peroxidase (H2O2),
  produced by various cells.

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Lymphatics

• a striking increase in the flow of interstitial
  fluid
• carries mediators and plasma proteins into
  tissues
• drainage focuses the materials (mediators
  antigens) and possibly microorganisms into the
  lymphatic duct system and the regional draining
  nodes, for an adaptive immune response.
• Washes mediators out of the site
• drainage of debris, mediators, antigen, or toxin
  may extend a severe inflammatory reaction into
  the lymphatics microbes extending the infection
• lymphangitis (channels), or lymphadenitis (nodes)
  
• mediators from the lesion drain away and cause
  systemic effects

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Systemic Acute Phase Reactions

• IL-1, IL-6, TNF from macrophage and endothelium
  at higher levels stimulate the liver, brain,
  muscle and indirectly other tissues
• sustained increase in CSFs e.g. GM-CSF, G-CSF,
  M-CSF, FGF stimulates marrow production of new
  cells
• liver metabolism changes blood protein levels
• rapid ?CRP and SAA, SAP
• slow ?transthyretin, albumin, transferrin
• slow ? fibrinogen, protease inhibitors
• acute phase proteins e.g. fibrinogen elevate the
  ESR
• fibrinogen and CRP are opsonins

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Acute Phase Blood Changes

• CBC
• leukocytosis (but can vary)
• increased hematopoiesis (left shift leukemoid
  reaction)
• decreased erythropoiesis, anemia
• Anemia of chronic disease (chelation and storage)
• MPS sequesters iron
• ? serum ferritin
• ? in lactoferrin (iron-chelator)
• ? hepatic synthesis of transferrin
• ? TIBC

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Presentation of an Acute Phase Reaction

• Behavior shiver, chills, anorexia, somnolence,
  malaise, septic shock.
• Autonomic changes reduce cutaneous blood flow
  favoring core circulation (conserves heat) rapid
  pulse and elevated blood pressure, decreased
  sweating.
• Endocrine and metabolic
• Increased glucocorticoids that induce a stress
  response decreased vasopressin, which reduces
  blood volume.

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Are there common variations in the acute
inflammatory vascular response?

• The stereotypic pattern for the classic acute
  inflammatory response may vary depending upon the
  elicitation, severity of the damage, the tissues
  effected, and the eliciting stimuli.
• In particular, the damage to the endothelium will
  affect the onset and duration of the response.

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Factors that Modify the Inflammatory Reaction

• Host related factorsimmune status, malnutrition,
  immune modulation by chemotherapy or infection
• Elicitation related factorsamount, virulence of
  micro-organism, durationintrinsic properties of
  the agent
• microbial spreading factors digest ECM and tissue
• microbial enzymes digest coagulated lymph which
  would otherwise limit the spread of infection
• susceptibility of micro-organism to destruction
  (biology, aggressins)
• ionizing (fibrinoid necrosis) vs nonionizing
  radiation (burns)

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Classifying Inflammatory Reactions

• by duration
• acute days subacute weeks chronic
  months-years
• by anatomical location
• solid tissue
• serosal surfaces
• epithelium lined surfaces
• by type of exudate

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Serous Inflammatory Exudates

• Commonly a thin exudate, mainly water and salt
  loss with insufficient fibrinogen conversion to
  fibrin, from blood or secretions of mesothelial
  cells lining spaces.
• Collects in pleural, peritoneal, and pericardial
  cavities (effusion) or joint spaces, or spreads
  throughout subcutaneous tissue or along fascial
  planes.
• e.g. burned skin or viral blisters pleuritis,
  pericarditis,etc.

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Fibrinous Acute Inflammation

• exudate with substantial amounts of fibrin
  (eosinophilic threads in a mesh or an amorphous
  clump) due to either sufficient damage for fibrin
  to pass the vascular barrier, or due to a
  procoagulant stimulus in the interstitium
• characteristically occurs in an inflammation in
  serosal lined cavities where the mesothelial
  cells become covered by fibrin polymerization
  with a dull surface
• on the surface of an organ it appears rough,
  "bread and butter or vegetations
• pain is noted with movement of underlying
  viscera, "catch in breath" in fibrinous pleurisy
  an on examination , a "friction rub" creaking
  sound on auscultation
• e.g. certain virulent bacterial infections,
  fibrinous pericarditis (shown here)

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Hemorrhagic and Catarrhal Responses

• Hemorrhagic
• a fibrinous reaction with damage to small blood
  vessels allowing rbc to escape into the
  extravascular space.
• E.g., typhus, anthrax, viral influenzal pneumonia
• Catarrhal
• Some allergic reactions and infections of mucosa
  produce marked mucus production
• E.g., runny nose with viral infections, coryza
  (cold in the head) of measles catarrhal stage of
  Whooping Cough

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(Pseudo)membranous reaction

• toxins stimulate a necrotic inflammation of
  mucous membranes
• inflammatory exudate forms an adherent , gray,
  pseudomembrane on the mucosal surface containing
  cells, necrotic debris, organisms, fibrin.
• E.g., Corynebacterium diphtheriae (oropharynx
  shown above), Clostridium difficile, S. typhi.

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Suppurative (purulent) Reactions

• Purulent (cell rich)
• suppurative (large amounts of pus is evident)
• pus microorganisms with significant local
  liquifactive necrosis of tissue and neutrophils
• e.g., acute appendicitis or a boil
• typically induced by "pyogenic" bacteria e.g.
  Staphylococcus aureus

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Focal purulent inflammatory reactions contained
in a confined space or tissue

• "abscess"
• A liquefactive necrotic center of dead
  parenchymal tissue and dead/dying neutrophils,
  surrounded by fibrin and live neutrophils, with
  an outer area of vascular growth, new collagen
  fibers, and parenchymal and fibroblastic
  proliferation. May become walled off by
  connective tissue.
• carbuncle is a deep multicompartment abscess
  along facia that erupts at multiple adjacent
  sinuses.
• furuncle (boil) is a single or multiple abscess
  under the skin may remain in this state for long
  periods, but heal faster if drained.
• In contrast, Cellulitis is a spreading
  inflammatory reaction.

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Outcomes
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Wound Healing Process

• The wound healing process leads to a restoration
  of the integrity and function of the tissue
• injury elicits acute inflammation and demolition
• migration and proliferation of parenchymal and
  connective tissue cells
• synthesis of ECM proteins by fibroblasts and
  other cells
• regeneration of parenchymal cells into functional
  tissue
• remodeling of connective tissue and parenchymal
  cell components
• collagenization and development of wound tensile
  strength

60
Types of Cells in Repair

• Labile cells
• replaceable from stem cells
• e.g., squamous epithelium of skin, mucous
  membranes, bone marrow
• Stable cells
• replacement requires forcing G0 cells to cycle
• e.g. kidney tubule cells, hepatocytes, smooth
  muscle cells
• Permanent cells
• nondividing, replaced by a scar or a cavity
• e.g. brain

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The ExtraCellular Matrix

• Stable complex of macromolecules underlying
  epithelial cells and surrounding connective
  tissue cells.
• Provides a structure into which replacement cells
  can come for wound resolution, creating order and
  tissue strength.
• Migrating cells attach to it.
• A special form of it forms basement membranes.

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ECM Composition

• collagens (10 types, vary in location)
• Matrix metalloproteases (zinc dependent) degrade
  and remodel collagen
• elastin provides recoil after stretching for
  skin, etc.
• fibronectin
• proteoglycans
• laminin

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Granulation Tissue

• The initial repair response to a wound,
  consisting of
• richly vascular connective tissue (capillary
  sprouts (leaky new blood vessels)
• collagen
• reactive fibroblasts and myofibroblasts,
• variable numbers of inflammatory cells
  (especially macrophage)
• enzymes and mediators.

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Fibroblasts

• Migration and proliferation of fibroblasts are
  stimulated by growth factors
• PDGF (platelet derived growth factor)
• EGF (epidermal growth factor)
• FGF (fibroblast growth factor)
• TGF-? (transforming growth factor beta)

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TGF-?

• Monocyte chemotaxis
• Fibroblast migration and proliferation
• Increases synthesis of collagen, ECM, and
  fibronectin
• decreases degradation of collagen and ECM
• Growth inhibitor for most epithelial cell types

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Collagen

• 1. intracellular procollagen is hydroxylated (Vit
  C dependent), glycosolated, secreted by
  fibroblasts
• 2. enzymatic modifications
• 3. terminal peptide chains removed by procollagen
  peptidases
• 4. complete fibrils/fibers/bundles form in the
  extracellular space
• 5. cross linkages between alpha chains and
  adjacent molecules form by oxidation rxn over
  weeks
• 6. Wounds are filled with Type 3, later replaced
  by Type 1
• 7. Remodeling requires MMP

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Fibronectins

• Derived from fibroblasts, monocytes, and
  endothelial cells
• Chemotactic for fibroblasts and macrophages
• opsonin
• Organizes endothelial cells into channels
• Cross links with fibrin, fibrinogen and collagen
  to increase tensile strength of collagen
• Binds to ECM components via integrin receptors
• Directly involved in attachment, spreading, and
  migration of cells

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Angiogenesis New blood vessels

• 2-3 days after wounding, vascular proliferation
  in granulation tissue begins, lasting several
  days
• induction by
• Fibroblast Growth Factor (FGF)
• Vascular permeability factor (VPF)
• Vascular Endothelial growth factor (VEGF)
• phases in the process
• Proteolytic degradation of the basement membrane
  allowing for formation of a capillary sprout
• Migration of endothelial cells toward an
  angiogenic stimulus
• Proliferation of endothelial cells
• Maturation of endothelial cells and organization
  into capillary tubes

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Healing by "primary union", or "first intention

• Early events during Days 1-3
• Wound occurs hemorrhage, clotting, cell injury,
  minor acute inflammation
• Neutrophils appear at margins.
• Mitotic epithelial cells at margins migrate
  across the wound
• Macrophages infiltrate the defect and break down
  fibrin. Thin surface epithelial layer forms by
  cell migration and fusion.
• Surface layer is thickening. Macrophage
  predominate.
• Vertical collagen fibrils appear along the
  margins.
• Granulation tissue progressively enters the
  tissue space

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Wound HealingWeek 1 and 2

• Day 5 Wound space is filled with granulation
  tissue, collagen fibrils begin to bridge the
  site, surface epithelium is normal thickness and
  architecture, acute inflammation is regressing.
• Day 7 Sutures are removed. Wound has 10 of
  tensile strength of normal skin.
• Day 7-15 More fibroblast proliferation and
  collagen deposition follows the lines of tissue
  stress with an increase in wound strength
  Leukocytic infiltrate, edema, increased
  vascularity decreases.

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Wound Healing Final Stages

• Day 30 Wound now is devoid of infiltrate,
  largely covered by intact normal epidermis 50
  strength, Type III collagen is slowly being
  replaced by Type I via action of collagenases and
  MMPs
• 3 Months Wound is 80 of normal. Complete
  blanching of a scar takes longer

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Issues in Successful Resolution

• extent of tissue necrosis
• Support stroma must be intact
• type of parenchymal cells involved
• cells must be able to regenerate
• adequacy of demolition
• debris and fibrin impair healing, induce scarring
• arterial perfusion and venous drainage
• e.g., scaphoid bone (hand) has poor circulation
• approximation- rough or tight
• Hint evert wound edges

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An Ulcer

• This slide shows in lining of the stomach with
  two punched out areas
• An erosion which extends down past the muscularis
  mucosa is an ulcer

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Occurrence of Larger Deficits

• More extensive tissue loss means a loss of ECM
  upon which to pattern tissue architecture
• Objective
• seal the surface, and when possible, fill the
  hole to preserve overall structure
• Examples
• e.g. ragged wound edges, ulcer or an infarct
• permanent parenchymal cells which cannot divide

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How is secondary union different than primary?

• large gaps have more fibrin and more necrotic
  debris, thus more intense inflammatory reactions
• more granulation tissue occurs and thus more
  scarring
• patent wound contraction is possible, esp. in
  skin (to 90) (myofibroblasts)
• result is healing by "secondary union, secondary
  intention
• progression into chronic inflammation is possible

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Scars
77
Mechanical Interference with Healing

• Mechanical stress on the wound creates a larger
  scar, may cause dehiscence
• hypertrophic scarring where skin is repetitively
  stretched neck, back, joints
• inject steroids into scar to reduce size
• cut skin along Langers lines, with bundles,
  causes less wound gapping
• evert edges

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Physiological impairments to normal healing

• Physiological impairments weaken the immune
  system and healing
• malnutrition or specific deficiency of Vitamin C,
  Copper, or zinc
• tissue hypoxia
• leukopenia (monocytes or neutrophils)
• Fibrinogen deficiency
• Diabetes
• severe anemia
• hormonal imbalances and various syndromes

79
Other Interferences to Normal Healing

• Infection (most common), or foreign bodies can
  lead to "chronic inflammation"
• Excessive contractures, e.g. burns
• Genetic and idiopathic predispositions lead to
  improper healing
• Keloid genetically predisposed production of
  hypertrophic scar tissue (type III collagen) more
  common in Blacks.
• exuberant granulation tissue formation (Proud
  flesh) protrudes above the skin and blocks
  re-epithelialization
• Desmoids (aggressive fibromatosis) reoccurring
  proliferation of fibroblasts follows incision of
  scars or traumatic injuries

80
Keloid

• hypertrophic scarring
• an over abundant deposition of Type III collagen
• genetic predisposition is more common in blacks

81
Chronic Inflammatory Disease

• heterogeneous grouping of prolonged duration
  (weeks to months) chronic inflammatory diseases
  resulting from continuing concurrent inflammatory
  tissue destruction and attempts at healing
• typically with granulation tissue (angiogenesis
  and fibrosis) and a monocytic infiltrate of
  macrophage, CD4 T cells, /- plasma cells
  occasionally eosinophils the mixture varies with
  type of response.
• The tissue damage often causes neutrophils to
  infiltrate secondary to the chronic inflammation.

82
Persistent Elicitation

• antigenic or nonantigenic, or de novo, with
  little acute inflammatory predecessor.
• The immunological reactions are of Gell and
  Coombs Type 4 hypersensitivities (Macrophage and
  T cell mediated).
• Thus a similar infiltrate can be the primary
  response to certain infections, tumors, and
  autoimmune diseases.
• Examples
• persistent infections, tubercle bacilli,
  Treponema pallidum
• prolonged chemical exposure particulate silica
  or gout crystals
• autoimmune diseases e.g. RA, SLE

83
Tissue destruction

• Caused by
• Microbes, neutrophils, monocytes, T cells
• characteristically a continuing tissue
  destruction of both parenchymal cells and the
  stromal framework
• Chronic inflammation interferes with the the
  healing process
• evident granulation tissue
• proliferation of fibroblasts and often small
  blood vessels
• fibrosis (increased connective tissue) creates
  scarring
• may heal, then the whole process reoccurs.

84
Participating cells

• Macrophage
• demolition, antigen presentation, secretion
• Lymphocytes
• secretion (Ig and cytokines)
• Fibroblasts
• connective tissue

85
Chronic Inflammation (lung) Cotran et al.

• inflammatory cells
• ? replacement by connective tissue
• ? destruction of parenchyma

86
General Clinical Aspects of Chronic Inflammation

• A delayed appearance of lesions may occur that
  may persist for extended periods, with the course
  and histological response variable and highly
  specific to particular types of eliciting
  conditions.
• Less swelling and hyperemia than acute
  inflammation
• Fever either subsides or is episodic
• Fibrosis (scarring) expected

87
Granulomatous Reactions

• Chronic inflammation of poorly digestible
  particles leads to distinctive focal arrangements
  of tissue in a few widespread diseases.
• Macrophage T cell mutual stimulation
• cytokine driven macrophage differentiation into
  epithelioid cells, foreign body giant cells,
  Langhans giant cells
• tumor like mass of epitheliod cells at the
  center, layer of lymphocytes, surrounded by
  fibroblasts

88
Soft or Caseous Granuloma

• a chronic inflammatory response poorly digestible
  micro-organisms
• epithelioid granuloma with an acellular necrotic
  core
• immune granuloma
• Langhans Giant Cell

89
Foreign Body Granulomas

• chronic inflammatory response to inert particles
  uric acid crystals (Gout), talc, sutures, and
  asbestos produces a
• "noncaseous epithelioid granuloma, or a "hard
  granuloma (non necrotic core)
• Foreign body giant cell

90
Laboratory Tests Useful in Evaluating
Inflammatory Diseases

• CBC (variant examples)
• bacterial left shift (immature forms)
• acute infections or stress neutrophilia
• some viral infections lymphocytosis
• allergy and parasitic infections eosinophilia
• some systemic infections and cancer leukopenia
• some acute viral or other infections or chronic
  inflammation monocytosis
• ESR
• reflects recent acute inflammation
• Specific liver derived acute phase reaction
  proteins
• CRP SAA
• Electrophoresis of serum
• Peroxidase stain or enzyme assay for MPO to
  demonstrate active neutrophils

91
Summary

• Examples
• minor cuts and healing
• a thin red line along surgical cuts is normal
• but not red streaks along the limb
• scarring
• why it occurs and how to reduce it
• chronic inflammation contrasted with acute
  Inflammation