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PATH3308 > 3 - Skin reconstruction & dermal equivalents > Flashcards

3 - Skin reconstruction & dermal equivalents Flashcards

1
Q

Epithelial layer

A
  • Keratinocytes (90%)
  • Melanocytes (pigmentation)
  • Immune cells
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2
Q

Dermal layer

A
  • Fibroblasts (matrix)
  • Endothelial cells (vascular supply)
  • Hair follicle cells
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3
Q

Merkel’s cells

A

Touch

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4
Q

Hair receptor

A

Movement

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5
Q

Pacinian corpuscles

A

Rapid vibration

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6
Q

Ruffini’s corpuscles

A

Lateral stretch

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7
Q

Meissner’s corpuscles

A

Vibration

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8
Q

Importance of treating skin injuries

A
  • Sepsis and death
  • Delayed healing increases scar risk
  • Infection leads to delay in healing
  • Oedema increases risk of infection
  • Inflammation increases oedema
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9
Q

Response to injury

A
  1. Clotting
  2. Vascular response
  3. Inflammation
  4. Scar formation
  5. Epithelial healing
  6. Contraction
  7. Scar remodelling
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10
Q

Ctritical burn injury treatment factors

A

Depth and surface area

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11
Q

Epidermolysis Bullosa

A
  • 40% die before adolescence
  • Entire epidermis regenerated using transgenic stem cells
  • Transgenic cells have selective advantage (don’t detach)
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12
Q

How many deaths from fire related burns each year worlidwide

A

~300,000

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13
Q

Wound debridement

A
  • Removal of dead tissue
  • Cut by surgeon or use of bromelain (pineapple enzymes)
  • Too much tissue cut off leads to slow healing, too little leads to infection
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14
Q

Wound debridement using Rapid Evaporative Ionisation- Mass Spectrometry (REIMS)

A
  • Diathermy knife used to cut necrotic tissue
  • Smoke extracted and sent to mass spectrometer
  • Profile of healthy and dead tissue is different, can help guide surgeon in what to cut out and what to leave
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15
Q

Skin grafts

A
  • Graft taken from patient’s healthy skin
  • Skin is meshed to cover large wound
  • Limited size (1:3 expansion)
  • Mesh pattern of healed skin
  • Donor site morbidity
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16
Q

Xenografts

A
  • From animals
  • Usually not cultured
  • Vigorous rejection, limited to temporary biological dressing
17
Q

Allografts

A
  • *From humans, typically cadaveric or neonatal donors
  • May or may not be cultured
  • Eventual rejection due to HLA-DR antigens
  • Immunosuppressive therapy must be given to prevent early rejection
  • Risk of cross-contamination
18
Q

Cell types and therapeutic approaches

A
  • Keratinocytes (epithelial cover)
  • Fibroblasts (dermal matrix)
  • Melanocytes (appropriate pigmentation)
  • Endothelial cells (revascularisation)
  • Cultured or non-cultured (time to application)
  • Combined therapies (with dermal matrices/scaffolds)
19
Q

Cultured Epithelial Autograft (CEA) sheets

A
  • Cultured using a large, full-thickness biopsy
  • Cultured as confluent sheets in the laboratory
  • Generally 3 to 10 cell layers thick
  • Clipped to a petrolatum gauze backing
20
Q

Time and scar risk

A
  • !0 days to heal –> 4% scar risk
  • > 21 days to heal –> 78% scar risk
  • Early treatment decreases risk and level of scarring
21
Q

Spray on skin (ReCell)

A
  • Stamp size piece of skin taken
  • Subject skin piece to enzymatic digestion to break down cells to individual cell suspension
  • Sprayed onto wound (greater coverage)
22
Q

Importance of ECM and dermal scaffold use

A
  • Physical characteristics (strength and stress)
  • Biological characteristics (secreted factors and glycosylation)
  • Can affect cells and determine phenotype
23
Q

Use of matrices

A
  • With deep/extensive burns, rapid replacement of dermal template can enhance recovery
  • Limited by angiogenesis into new template to achieve epidermal coverage
  • E.g. integra
24
Q

Integra

A
  • Porous, biological collagen based matrix
  • Biodegradable so can be left in wound
  • Add integrae to wound then ReCell
25
Q

Matriderm guided tissue regeneration and cell activation

A
  • Invading cells use the fibers as guiding ridges for structured healing
  • The cells recognise binding sites on the native collagen fiber and get activated by binding to them
  • Activated fibroblasts start to produce the body’s own collagen
26
Q

Biodegradable Temporizing Matrix (BTM)

A
  • Porous, synthetic polymer
  • Top layer non-biodegradable, bottom layer biodegradable
  • BTM applied to wound bed, limiting water loss
  • After 2-3 weeks, cells have integrated and blood vessels have formed
  • Once integrated, sealing membrane removed
27
Q

Bilayered replacements (Apligraf)

A
  • Cultured allogeneic graft that contains both epidermal and dermal layers
  • Contains all layers of skin
  • Does not contain blood vessels, hair follicles, or sweat glands or
    other cell types such as Langerhans’ cells, melanocytes, macrophages, or lymphocytes
28
Q

Examples of difficult to treat burn cases

A
  • Deep, highly pigmented and vascularised scars
  • Hands due to curves
  • Joints
29
Q

Laser scar amelioration

A
  • Adjunct therapy
  • Laser burns small holes in skin (re-injuring)
  • Resulting re healing of the scar with less inflammation and stress improves scar outcome
  • Also affacts vascularisation
30
Q

Adult multipotent stem cells

A

Hematopoietic stem cells
- fibrocytes
- Mesenchymal stem cells
- Adipose derived stem cells

31
Q

Reprogrammed stem cells

A
  • Somatic cell nuclear transfer
  • Cell fusion
  • Induced pluripotent stem cells
32
Q

Possible functions of cultured MSC

A
  • Immunomodulation
  • Anti apoptosis
  • Angiogenesis
  • Support of growth and differentiation of stem and progenitor cells
  • Anti scarring (anti fibrosis)
  • Chemoattraction
33
Q

Too much vs too little vascularisation

A
  • Too much = scarring
  • Too little = inefficient scar healing
34
Q

3D bioprinting

A
  • Drop-on-demand printhead
  • Bioinks and cells suspended in activators in the printhead
  • Printing layering of bioink and activator
35
Q

Split Thickness Skin Graft (STSG)

A
  • A graft that contains the epidermis and a portion of the dermis,
  • Still widely used

PATH3308 (8 decks)

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