Welcome to Brenda's Science Communication Project on Healing
Great... So are all wounds the same???
Um no... Let me explain the different kinds. Healing processes differ slightly depending on the severity of the wound.
A wound is defined as disruption to the anatomical structure and function (Velnar et al. 1529). Wound healing begins at the moment of injury and involves both resident and migratory cell populations, extracellular matrix, and the action of soluble mediators (Velnar et al. 1529). Healing time may be diverse and take up to a year or more to heal completely (Velnar et al. 1529). Completely healed wounds are those that have returned to normal structure, function and appearance of the tissue over time (Velnar et al. 1529).
Let me just write some stuff here.. I'm about to go off.
Meet Brenda. She fell out of bed this morning and scraped her face in attempt to get out of her 8:30 biology class. Unfortunately she got hurt pretty bad.
Kids these days
Acute wounds are wounds that repair themselves and proceed normally throughout the healing process by restoring the structure and appearance of a wound (Velnar et al. 1530). Chronic wounds are those that fail to progress normally and can't be repaired in an orderly and timely manner. The healing process is disturbed by factors which prolong some phases of haemostats, inflammation, proliferation or remodelling (Velnar et al. 1530). Complicated wounds require a special entity and is a combination of an infection and a tissue defect. Infection poses a constant threat to the wound (Velnar et al. 1530).
I'm learning so much! This is pretty incredible.
Alright then. Let's fix you up shall we?
Hello child. What have you done to yourself this time?
Well you see doc, I hit my head pretty hard against the wall and got some scrapes on my face. Can ya help me out?
Atta girl. I knew we had a biologist in the making..
The healing process is continuous and is divided into four phases: 1. Coagulation and haemostasis 2. Inflammation (early & late) 3.Proliferation 4. Wound remodelling It is divided into parts to understand the physiological phases that take place in the wound and surrounding tissue (Velnar et al. 1531).
Oh and ignore the random pills on the loose over there lol
Alright lets head to the examining room... Say, do you know anything about healing and cell regeneration?
What did I get myself into???
Random nurse (ignore her she's irrelevant)
Coagulation and Haemostats This phase aims to prevent exsanguination. This protects the vascular system by keeping it in tact so that the vital organs remain unharmed despite the injury. This phase provides a matrix for invading cells that are needed in the later phases of healing (Velnar et al. 1531).
Oh child.. Get ready to be MIND BLOWN!!!
You see as you scraped your face earlier today, coagulation and haemostats began to occur.
Soo... What is there to know???
This is so much more complex than I ever thought...
Wound healing involves multiple cell populations, the extracellular matrix and the action of soluble mediators such as growth factors and cytokines (Velnar et al. 1528). Wound healing remains a challenging clinical problem and correct, efficient wound management is essential (Velnar et al. 1529). Now, before we go into detail we should identify what kind of wounds there are and what makes each different. You ready for this?
The Inflammatory Phase The aim of this phase is to establish an immune barrier against micro-organisms (Velnar et al. 1532). The early inflammatory phase activates the molecular events leading to the infiltration of the wound side by neutrophils, whose main function is to prevent infection (Velnar et al. 1532). 48-72 hours after the injury, the wound undergoes phagocytosis where cells act as regulatory cells providing an abundant reservoir of potent tissue growth factors (Velnar et al. 1533).
Brenda, because you clearly came here to get out of your biology class this morning, I should teach you something. Get ready for this lesson. It's a big one and it involves many steps and many roles for the body.
Right?! Took me 12 years of med school to memorize this stuff.
The Proliferative Phase This phase starts on the 3rd day after wounding and lasts about 2 weeks (Velnar et al. 1533). It is characterized by fibroblast migration and deposition of newly synthesized extracellular matrix, acting as a replacement of fibrin and fibronectin (Velnar et al. 1533). Following the injury, fibroblasts and myofibroblasts are stimulated to proliferate for the first three days (Velnar et al. 1534).
Side note: The fibroblasts contain thick actin bundles below the plasma membrane that actively extend pseudopodia, attaching to fibronectin and collagen in the extracellular matrix (Velnar et al. 1534). Modelling and establishing new blood vessels are critical in wound healing and takes place concurrently during all phases of the restorative process (Velnar et al. 1534).
Ya good thing...
Adhesion is a particularly important step in cell migration as it is medicated by interns which act as the primary receptors for extracellular martix proteins and are consequently required for cell motility (Velnar et al. 1535). Adhesion and motility are proportional; an optimal rate of migration is achieved with increasing adhesion (Velnar et al. 1535). Collagens act as a foundation for the intracellular matrix formation within the wound (Velnar et al. 1534). They impart integrity and strength to all tissues and play a key role in the modelling phases of repair (Velnar et al. 1534).
Oh so this is how contractile forces, transmitted through the integrin-cytoskeletal connections, allow the cell to pull the cytoplasm forward by generating traction to the substratum (Velnar et al. 1536).
She's finally starting to get it...
The last phase... Thank God.
The Remodelling Phase This is the final phase of wound healing that is responsible for the development of the new epithelium and the final scar tissue formation (Velnar et al. 1536). This phase can last up to 1-2 years (Velnar et al. 1536). Synthesis and breakdown of collagen as well as extracellular matrix remodelling take place and tend to equilibrate about 3 weeks after injury (Velnar et al. 1536). The new collagen matrix become more oriented and cross-linked over time (Velnar et al. 1537).
She's so interested. What a good student.
Wound-healing technologies include traditional dressings, antimicrobial dressings, anti-inflammatory dressings, advanced dressings containing biological or naturally derived agents, medicated sutures, and tissue-engineered skin substitutes (Gwak, Jae Ha, and Young Sohn, 2). Synthetic polymers have good moisture absorption capacity and can help to maintain a moist wound environment. In traditional dressings, cotton, wool, bandages, and gauzes are mostly used because of their ease of use, accessibility to most surgical hospitals, and low cost (Gwak, Jae Ha, and Young Sohn, 3). Antimicrobial dressings are used to kill bacteria or fungi that are present in infected wounds, and can reduce the risks of reinfection during wound-healing, surgical procedures, or when changing the dressing (Gwak, Jae Ha, and Young Sohn, 3).
Side note: Healing is a complex process involving co-ordinated interactions between diverse immunological and biological systems. It involves carefully and precisely regulated steps that have to do with the appearance of various cell types in the wound (Velnar et al. 1531).
So you see Brenda, numerous pathological and metabolic factors can affect wound healing which can result in a poor outcome (Velnar et al. 1537). Factors such as infection, metabolic disease and nutritional status impede healing and can turn an acute wound to a chronic one (Velnar et al. 1537).
I am Doc. It's grind time you know? Gotta write 3 assignments in 2 days with 1 more week of school left.
Say Brenda I didn't mean to scare you... You seem stressed.
Well you know, stress can affect many features of cellular immune function including cytokine production which is fundamental for your wound to heal (Marucha et al. 1).
I hope you have learned something new by watching this presentation on wound healing and restoration! We have called your teacher Ms. Blais to come pick you up. Good luck!
Side note: Interleukin is also important in the destruction and remodelling phase of connective tissue (Marucha et al. 3). It regulates fibroblast chemotaxis and the production of collagen and stimulates the production of other cytokines important for wound healing (Marucha et al. 3).
Ya that makes sense because don't cytokines help to protect against infection, prepare injured tissue for repair, and enhance phagocyte recruitment and activation (Marucha et al. 1)?
It's a good thing you won't be needing surgery then. Wounds after surgery are serious because they increases infection to the surgical site Li, (Yoshihiro TakemotoTao-Sheng, et al, 1). Wound inflammation is central to the formation of new tissue (Yoshihiro TakemotoTao-Sheng, et al, 1).
Side note: Wound infection after surgeries are more common in patients with an advanced age, diabetes mellitus, chronic renal failure, and other systematic diseases (Yoshihiro TakemotoTao-Sheng, et al, 1).
Lucky for those people though because the implantation of stem/progenitor cells have been demonstrated to improve wound healing after surgery (Yoshihiro TakemotoTao-Sheng, et al, 1).
Side note: Surgical injury increases the release of cytokines/chemokines that induces the mobilization of stem/progenitor cells (Yoshihiro TakemotoTao-Sheng, et al, 5). Surgical stress is sufficient to induce cytokine secretion and stem/porgenitor cells mobilization (Yoshihiro TakemotoTao-Sheng, et al, 5).
Such a stupid idea... I should have just gone to class.
Ok now let's talk about wound healing technologies so that you can heal faster... Back to the white board!
The application of physical therapies to wound-healing accelerates the natural healing process by using an electric or current laser.
Nah don't you worry about that right now. Just something to know.
Ya but I wont need that right?!
Ok Brenda let's get you fixed up here. I'm going to use traditional dressing with synthetic polymers for a speedy recovery. After this, you should be good to go!
Ok Doc. Thank you so much!
Let's go Brenda... I'm glad you learned something. You still have your quiz to write when you get to class.