physiology of wound healing wound healing is: – complicated process that involves at least 4...
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Physiology of wound healing
Wound healing is:– Complicated process that involves at
least 4 distinct cell types– Commonly referred to as occurring in
PHASES– Affected by several factors
Phases of wound healing process (WHP)
Haemostasis
Inflammation
Proliferation
Maturation
Where does a chronic wound get stuck?
Platelet ActivityWOUND
Exposed collagen
Intrinsic pathwayXII
Intrinsic pathwayintermediates IX, VII
Extrinsic pathwayVII
Coagulation pathwayintermediates V, X
Tissue factor
Messengers forAggregation &coagulation
Growth factors(PDGF)
Other enzymes(proteases)
Platelet
Fibrinogen
FIBRIN
Prothrombin & thrombin
XlilaCross-linked fibrin clot(structural support for wound healing)
Role of keratinocytes in wound healing
Migration/Profileration
Protease release
AngiogenesisECMproduction Growth factor/
Cytokine production• Epibloy• Integrins
• Matrix formation• Basement membrane formation
• VEGF• TGF-α• PDGF• PD-ECGF
• Chemoattractants− VEGF− KGF (FGF-7)
• Dissolves− Nonviable tissue− Fibrin barrier
Keratinocyte
Selected growth factors important to wound healing
• EGF (epidermal growth factor). Stimulates wound re-epithelialization and stimulates blood vessels and fibroblasts.
• FGF (fibroblast growth factor). Stimulates new blood vessel and collagen formation.
• PDGF (platelet derived growth factor). Attracts/stimulates smooth muscle cells, fibroblasts, and other cells. Important in ECM formation.
• TGF-β (transforming growth factor-beta). Slows buildup of epithelial cells, suppresses immunoglobulin secretion and is helpful in ECM formation.
• TNF-a (tumor necrosis factor-alpha). Activates neutrophils, causes fibroblasts to multiply, causes bone/cartilage resorption.
• IL-1 (interleukin-1). Attractant for epithelial cells, neutrophils, mono and lymphocytes; also stimulates collagen synthesis.
Chronic wounds – characteristics
• Increased inflammatory cytokines• Altered fibroblast phenotype• Abnormalities growth factors• Increased proteases• Altered keratinocyte function• Senescent cells (increased number)
Wound bed preparation
• Debridement• Bacterial balance• Dressing therapies
(f.i. silver dressings prevent of infections, help reduce healing time)
Local wound care
debridement moisture balance
SurgicalAutolyticEnzymaticBiological
FoamsCalcium alginatesHydrogelsHydrocolloidsAdhesive filmsNegative pressure therapy
Tissue engineering
Biology, medicine and technology are today closely interleaved with each other
Tissue engineering – combining cells and biomaterials into functional tissues
Cells are seeded onto a biomaterial scaffold to be integrated into a specific tissue
Tissue engineering
Advances– Biological wound dressings– Material scaffolds and cell material
interactions– The use of stem cells for tissue
engineering– Combination of stem cells and material
scaffolds into tissue engineered replacements of tissues and organs
Tissue engineering implants
Synthetic polymeric biomaterials• Nonbiodegradable
Is required to provide and maintain optimal cellular function -> e.g. alginate, liposome,…
• Biodegradable To restore the histological structure and
replace the cellular function of recipients -> e.g. poly L-lactic acid, poly glycolic acid, …
Wound healing promoting anti-adhesive matrix
The collagen grafting is also applied to produce a healing / promoting antiadhesive membrane
• Particularly necessary in peritoneal surgery to prevent postoperative adhesion
• To produce skin wound dressing membranes
Methods of tissue bioengineering
Skin replacement
– Cultured epidermal graft– Cultured human autologous and
allogeneic keratinocytes– Semi synthetic materials (composed of
human neonatal dermal fibroblasts cultured onto a bioabsorbable mesh)
Methods of tissue bioengineering
• Active dressings (f.i.: with maggot’s excret, with honey)
• Photobiomodulation (modulate cellular activity in red to near infrared light)
• Hyperbaric oxygen therapy: as therapeutic benefit in WT
• Growth factors (from blood)
Allogeneic cultivated human skin
keratinocytes• Make rapid healing of the ulcers particularly those
that are difficult to heal• No clinical or laboratory evidence of rejection• No evidence of preexisting cytotoxic antibodies
specific fort the HLA class I antigens expressed on HSE cells
• A fibrin-based skin substitute produced in the defined keratinocyte medium could be safely used to threat a number of skin defect
Preparation of autologous fibrin-based skin substitutes
Methods of tissue bioengineering
• Autologous platelet rich plasma product (platelet gel)
• Allogeneic platelet gel
The effect is attributed to the growth factors
Fracture
Delayed unionPseudoarthrosis - nonunion (bone defect)
Infection
?Method of treatment?
Impaired healing
Impaired healing
• Large bone defect
Lack of osteogenic progenitor cells
• Diabetes, glucocorticoid treatment, chemotherapy, ...
Accepted methods of treatment
• Autologous bone transplants– Cancellous bone graft (contains all necessary
characteristics of bone substitutes)– Corticocancellous graft (possibly vascularized
limited amount)
• Homologous (allogeneic) graftBone banks, treated (no rejection), contains only osteoconductive properties
• Ilizarow intercallary bone transport (traction method)
Properties of bone grafts
• Osteogenesis (bone marrow, cancellous bone)
• Osteoinduction– Demineralized bone matrix– Growth factors (platelet rich plasma,
bone morphogenic proteins – BMPs)• Osteoconduction
– Ceramics– Collagen
Alternatives
Bone substitute (biomaterials for scaffold):
– Demineralized bone matrix– Biocompatible ceramics– Synthetic Calcium phosphate– Mineral bone– Collagen– Composite grafts – Osteoinductive collagen
Alternatives
Role of GROWTH FACTORS
Role of STEM CELLS
Collagen based matrices in tissue engineering
• Skin equivalent• Cartilage repair• Bone repair
Matrices are also prepared from synthetic polymers
Fracture healing promoting molecules
Growth and different factors– The transforming growth factor-β (TGF-β) superfamily
• Bone morphogenetic proteins(osteoprogenitors, mesenchymal cells, osteoblasts and chondrocytes within the extracellular matrix produce BMPs.)BMP-2, BMP-4BMP-5, BMP-6, BMP-7GDF-5 (BMP-14), GDF-6 (BMP-13), GDF-7 (BMP-12)BMP-3 (Osteogenin), GDF-10 (BMP-3b)
– Platelet-derived growth factor (PDGF)– Fibroblast growth factor (FGFs)– Insulin-like growth factor (IGFs)
Platelet rich plasma (contains high concentrations of growth factors) especially TGF-B and PDGF
Autologous Allogeneic
PLATELETS
PDGFPDGF
TGF-TGF-ββ
MONOCITE
MACROPHAGE
FIBROBLAST
ENDOTHELIUM OSTEOBLASTS
NEUTROPHILS
SMOOTH MUSCLE
PDGFTGF-β
• Mesenchymal stem cell: the promise for treating skeletal disorders
• Adult stem cell are being isolated from various tissues
Adult stem cells
Bone marrow contains
– Hematopoietic stem cells (HSCs)• All types of blood cells
– Bone marrow mesenchymal stem cells (MSCs)• Generating bone, cartilage, fat, fibrous connective
tissue
Bone tissue formationBone tissue formation
OOsteogenic progenitor cellssteogenic progenitor cells
Locations:Locations:• PeriostPeriost• Peritrabecular soft tissuePeritrabecular soft tissue• Cancellous bone and bone marrow Cancellous bone and bone marrow
(in BM aspirate up to 40x less (in BM aspirate up to 40x less stem cells stem cells then in cancellous bone)then in cancellous bone)
Our method of tissue engineering
Combined graft
Autologous cancellous bone withstem cells
Allogeneic platelet gel(source of GFs)
manually grounded autologous cancellous bone with stem cells
corresponding amount of allogeneic platelet concentrate (app. 1,4x109 platelets per 1 ml)
AND
Added 0,06 ml human thrombin in 40 mM CaCl2 for the activation of platelets
in 1 minute
the resulting gelled graft can be shaped according to the bone defect and implanted
Mixed
Our graft
Autologous cancellous bone with stem cells and allogeneic platelet gel
Conclusions
The use of autologous cancellous bone with stem cells and allogeneic platelet gel is safety and effective method for the treatment of nonunion of long bones
Future
Gene arrays for gene
discovery
FUTURE
Cell and tissue engineering
Detection of numerous signal pathways activated during physiological
processes
Self (re)restoration and differentiation off mammalian embryonic, fetal and
stem cells of adult tissues
Thank you for attention !