wound healing and regeneration, Slides of Pathology

Download wound healing and regeneration and more Slides Pathology in PDF only on Docsity! RYN ETHIOPIAN NEW YEAR, 2014 Healing and Repair Shallo Alemu, MD tissue repair mechanisms by Shallo A, Wound Healing Time Course > Wound ve contraction : Granulation tissue ¢ * Collagen accumulation Remodeling Inflammation T 0.1 0.3 1 3 10 30 100 10/17/2021 Days Elsevier. Kumar et al: Robbins Basic Pathology 8e - www-.studentconsult.com | Coagulation 1 Vasoconstriction 24°45 minutes 10/17/2021 Vasodilation 10 2030 foam PMN neutrophils predominant © Macrophages predominant Fibronka and granulation tissue formation 50% of normal tissue strength Maturation and remodeling Angiogenesis shalialinatian - Incomplete basement membrane Epitheliaieata Beomplete babement membrane | Contraction 1 2734 56°) 2 2345 60 hours 24 48 days7 tissue repair mechanisms by Shallo A, 6 Stages ¢ Exudative stage (day 1-4) Growth factors, .__ wecrophage ¢ Hemostasis: limits blood loss from _ the wound via vasoconstriction. There is a release of inflammatory — om mediators (growth factors, chemokines, and cytokines) via the \ Fibroblast proliferation activation of platelets. Histamine, prostaglandins, ° Inflammation: clears cellular debris kinins, leukotrienes through phagocytosis. There is a ; | migration of inflammatory cells that facilitate tissue regeneration (via growth factors) Neutrophil Lymphocyte Chemotaxis Vasodilation 10/17/2021 tissue repair mechanisms by Shallo A, 7 Granulation Tissue ¢ Hallmark of healing ¢ Term comes from soft, pink, granular appearance when viewed from the surface of a wound ¢ Histology: Proliferation of small blood vessels and fibroblasts; tissue often edematous Granulation Tissue GT 11 tissue repair mechanisms by Shallo A, 10/17/2021 Ulcers: an example of healing by 2rd intention 10/17/2021 tissue repair mechanisms by Shallo A, 12 Reparation ¢ Primary intention: when the tissue surface edges have been approximated ¢ Small defect with little risk of complications and/or infection ¢ Secondary intention: when there are significant tissue losses and the wound surface cannot be brought together (e.g., lacerations, burns, and ulcers) ¢ Scar formation occurs with a higher risk of infection * Tertiary or delayed primary intention: when there is a need to delay the closure of a wound (due to contamination risk, poor circulation, etc.) Primary intention Clean incision Early suture Hairline scar Secondary intention Gaping irregular Epithelium grows Granulation wound over scar Tertiary intention Wound Increased granulation Late suturing with wide scar 10/17/2021 tissue repair mechanisms by Shallo A, 15 So, how repair process comes in to being? ¢ The regeneration of injured cells and tissues involves cell proliferation, which is driven by growth factors and is critically dependent on the integrity of the ECM, and by the development of mature cells from tissue stem cells. Cell Proliferation: Signals and Control Mechanisms ¢ Remnants of the injured tissue (which a. _Intrinsic proliferative capacity attempt to restore normal structure) b. Presence of tissue stem cells ¢ Vascular endothelial cells (to create new vessels that provide the nutrients needed for the repair process) ¢ Fibroblasts (the source of the fibrous tissue that forms the scar to fill defects that cannot be corrected by regeneration) An example of healing by fibrosis: Myocardial Infarction Edge of acute infarct Quiescent Vasodilation vessel (VEGF) Mechanisms Leading ("tip") cell (VEGF, Notch signals) Pericyte detachment (angiopoietin) * Angiogenesis membrane Basement membrane Endothelium degradation (MMPs) ¢ Deposition of Connective Tissue e Activation of Fibroblasts ¢ Remodeling of Connective Tissue 10/17/2021 tissue repair mechanisms by Shallo A, 21 Factors affecting repair * Local ¢ Systemic * Ongoing inflammation (infection, * Diabetes, foreign body) Heart failure, ¢ Tissue under tension (immobility) Pulmonary diseases, ¢ Inadequate perfusion malnutrition * Degree of exudate removal Drugs (steroids) * Tissue type Smoking Pathogenesis ¢ Excessive Fibroblast proliferation ¢ TGF-beta activity * Genetic ¢ African, blacks ¢ Asian descents * Predilection sites ¢ Upper chest, shoulders, upper back, and head and neck, especially on the ear * Keloids never regress, they grow bigger as time passes Hypertrophic scars ¢ Raised scars that do not grow beyond the boundaries of the original wound. ¢ Made of wavy and linearly arranged array of collagen parallel to surface epithelia 10/17/2021 tissue repair mechanisms by Shallo A, 26 Cont’d.,... ¢ Contracture 10/17/2021 tissue repair mechanisms by Shallo A, 27