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BMS354 Tissue engineering > Part 3 > Flashcards

Part 3 Flashcards

1
Q

Boy gets new skin case 2015

A

Gene correcting skin
doctors took stem cells, corrected a faulty mutation within them and then put back in skin
80% replace
- severe injuries
- Syrian refugee, admitted as paediatric burn

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2
Q

Epidermolysis bullosa (EB)

A

Genetic disorders
~1 in 50,000 live births- life expectancy
Spontaneous skin blistering
Painful and life-threatening complications- prone to bacterial infection
“Butterfly children”
High risk of skin cancer- unsure why

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3
Q

Skin blistering

A

epidermis peel off dermis
usually closely attached
Due to the basement membrane usually Structural adhesion, resistance to shearing
BUT Not in patient

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4
Q

Why does the BM allow structural adhesion

A 
TM receptor 
A664 interacts with laminins- interact with collagen 
- very structured 
- adhere 
absence/ mutations effects interaction
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5
Q

Case study: The Patient

A

Splice site mutation within intron 14 of LAMB3
Skin blistering since birth
Infection
Most areas of skin denuded

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6
Q

Normal treatments for EB

A

antibiotics to stop sepsis
skin transplant for denuded skin
end of life treatment

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7
Q

A case study published in 2006: treatment one off

A

A one-off compassionate treatment- he was going to die
Only a small area of the skin was treated
correction of junction EB by transplantation of genetically modified epidermal stem cells

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8
Q

Why is it not developed?

A

No legislation
all procedures done under certain GMP rules
trying to work around this

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9
Q

Why wouldn’t autologous cell therapy work?

A

Isnt enough skin as genetic disease
cells have faulty disease
needed addition or alternative

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10
Q

Gene therapy

A

Aims to repair or replace a mutated gene
Ex vivo versus in vivo
Vectors: viral versus non-viral

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11
Q

Ex and in vivo

A 
Ex= cells taken from patient manipulated in culture and replaced back 
In= corrected version of gene is attempted inside body
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12
Q

Gene therapy strategy for LAMB3

A

A retroviral vector expressing the full-length LAMB3 cDNA

took correct sequence of gene- put in DNA- not correcting mutation itself but deliver correct DNA

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13
Q

Ex vivo steps

A

JEB patient
Feeder layers- 8 days and split
another 3 days with Lamb3 - keratinocyte transduction
another 5 days
PGc analysis- Sequencing analysis
Deliver correct version of gene so integrate randomly

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14
Q

Feeder layers

A

layers of mitotically manipulated cells for kerintocytes

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15
Q

Problems with integration of the corrected mutation

A

Look at where gene has integrated
gene area= integration sites on exons, very little genes composed on exons
look if any were oncogenes or tumour suppressor= they weren’t
hard to predict integration

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16
Q

Different ways of preparing skin substitutes in the ex vivo gene and cell therapy

A

Prepare skin substitutes
tested 2 different conditions- plastic and fibrin
3 different areas of body
fibrin worked best- 3000 cm^2 transplantation of transduced graft

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17
Q

Patient follow up

A

took number of biopsies of skin- in situ, next gen, global analysis
epidermis= regenerated in patient- didn’t come from modified

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18
Q

What is the epidermis made up of

A

genetically modified cells
expressional cadherins
- expression only in transduced cells
add cadherin to tell whether the layers have fused

Keratinocytes present= one transduced with virus so also express the right version of laminin and adhere to the dermis

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19
Q

epidermal-dermal junction after cell therapy

A

Nice expression of laminin after admission and 4 months
21 months no blistering stick together nicely
Lmab3 expressed

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20
Q

Difference in the mutated and genetically corrected keratinocytes

A

Laminin332-B3 null and corrected

difference in adhesive properties of mutant patient-derived and genetically corrected keratinocytes

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21
Q

EB boy now

A

Nice appearance of skin
Not red
stitches with no blistering

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22
Q

Summary of EB study

A
  1. boy EB- results in chronic wounds to skin
  2. Biopsy- skin cells were taken from an area of body not affected
  3. mutated gene fixed
  4. develop in vitro of the corrected cells
  5. large sheets of transgenic epidermis cultivated
  6. entire wounded area of the boys body was treated with grafts
  7. regenerated dermis adhered firmly
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23
Q

Considerations for further work

A 
Longer-term follow up of the patient
Further clinical studies
Alternative gene editing strategies
Patient age
Discolouration of skin- no melanin in- add this q
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24
Q

Human skin construct

A
  1. immunity
  2. pigmentation
  3. appendages
  4. hypodermis
  5. innervation
    6.. vascularization
    Skin made up of all these things so tissue regeneration is hard to recreate
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25
Q

Primary research article

A

Bioengineering 3D integumentary organ system from IPS cells using in vitro transplantation model

  • Fabrication of the 3D skin and its appendages could contribute to regenerative therapies
  • Difficult to recreate in vitro
  • Hypothesis: pluripotent stem cells can be used to mimic the developmental patterning
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26
Q

Experimental approach of IPS skin constructs

A

Induction of epithelial tissues via the Clustering-dependent EB (CDB) transplantation approach
Day 0- sorting IPS cells
Day 7- in vitro transplantation of CDB method
Day 30- in vivo organogenesis

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27
Q

Analysis of the bioengineered hair follicle

A

The hair shaft – from iPSCs
reflected the original mouse they derived the IPS mouse from
WNT3B stimulated

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28
Q

Analysis of hair follicle in IPSC bioengineered 3D ios

A

The isolated cystic structures with hair follicles were observed macroscopically

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29
Q

Transplantation of the bioengineered 3D integumentary organ system

A

In vitro organized integumentary organ system derived from male IPS cells
add to female SCID mouse
intracutaneously transplantation
orthotopic hair function
*IPS hair follicles had a correct structure and connect with local tissues

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30
Q

The significance of the hair follicle study

A

Fully functional iPSC-derived explants included:
hair follicles and sebaceous glands with proper connections to the epithelium, dermis, fat, arrector pili muscles and nerve fibers
A step towards complete reconstruction of skin

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31
Q

Disease modeling using skin substitutes

A 
Epidermolysis bullosa
Vitiligo
Psoriasis
Skin cancer
Allergic contact dermatitis
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32
Q

Psoriasis

A

Chronic inflammatory skin disease
Red plaques on the skin
Keratinocyte hyperproliferation,immune cell infiltration, increased angiogenesis

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33
Q

In vitro psoriasis models

A

2nd model- Patient keratinocytes, Cytokines (TNFa, IL-1a, IL-17, IL22)
3rd model- Keratinocytes and fibroblasts, Cytokines

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34
Q

Companies to start in vitro testing of chemicals

A

l’Oreal

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35
Q

Peripheral nerve injuries

A

9000 cases in the UK per year
Mainly in young population
Main cause: car accidents
Financial, healthcare and societal burden

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36
Q

Central NS approaches

A

Approaches developed but lagging behind

clinical trial for human pluripotent stem cells with adrenergic transported into parkinsons disease patietns

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37
Q

Peripheral NS

A

Major somatic

sensory and motor pathways to the extremities- ulnar, median, cervical, femoral etc

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38
Q

Peripheral Nerve Anatomy

A

Axons are surrounded by myelinating Schwann cells and are enclosed by endoneurium
Individual axons are bound together by perineurium to form fascicles
Epineurium groups fascicles, creating the nerve cable

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39
Q

Types of peripheral nerve injury

A
  1. Elongation
    The connective tissue of nerves allows 10-20% elongation before structural damage occurs.
    Severe lesions that disrupt the axon.
  2. Laceration
    30% of nerve injuries.
  3. Compression
    External mechanical pressure on the conductive membrane.
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40
Q

Grade 1 of peripheral nerve injury

A

1) NEUROPRAXIA
No/little structural damage, no loss of nerve continuity
Symptoms are transient, reversible
Entrapment neuropaties

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41
Q

Grade 2 of peripheral nerve injury

A

2) AXONOTMESIS
Complete interruption of the axon and its myelin sheath
Perineurium and epineurium intact

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42
Q

Grade 3 of peripheral nerve injury

A

3) NEUROTMESIS
Nerve and the surrounding stroma are completely disconnected
No spontaneous recovery
Weakness and atrophy

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43
Q

Wallerian degeneration

A

Injury- axons of distal end cut away from cell body, start of degeneration because protease activity
cytoskeleton disintegrate and break

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44
Q

Peripheral nerve after injury

A

2 weeks- Wallerian degradation, degrading fibres and myelin sheath
3 weeks- proliferating schwann cells, axonal sprout penetrating band of bungner- atrophied muscle
3 months- successful nerve regeneration- muscle regeneration

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45
Q

Neuronal regeneration in CNS

A

Macrophages infiltrate much more slowly, delaying the removal of inhibitory myelin
“Reactive astrocytes” produce glial scars that inhibit regeneration

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46
Q

Differences in PNS vs. CNS injury

A

In PNS: repair of damage is actively promoted
In CNS: repair of damage is inhibited
CNS and PNS require different regenerative medicine strategies
More success in PNS thus far

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47
Q

Approaches of neuronal tissue repair in PNS

A
  1. surgical reconstruction
  2. Grafts
  3. nerve conduits
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48
Q

surgical reconstruction

A 
put stumps of nerve back together
only possible if close enough together 
Tension reduces blood flow:
Blood flow reduces by 50% when the nerve is stretched 8%
Complete ischemia at 15%
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49
Q

Grafts

A
  1. autologous
    - same person
    + low risk
    - loss of function at donor site, 2 surgeries required, limit to size and type
  2. allogeneic- same species donor
    + no secondary surgery, no loss of function at donor site
    - higher risk of rejection, limit availability
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50
Q

Nerve conduits

A

Guide regenerating axons
Prevent infiltration of scar tissue
Increase concentration of intraluminal proteins

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51
Q

Peripheral nerve regeneration through a nerve conduit

A

Hours- conduit fills with plasma
Days- fibrin cable forms
Months- cell migration and axonal regeneration
Years- resulting tissue is notably thinner

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52
Q

Properties of ideal nerve conduits

A

Plasma pass through
porous
long term degradability

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53
Q

Classes of biomaterials for nerve conduits

A

Natural, systemic, semi-synthetic

54
Q

Decellularised nerve conduits

A

Top down approach

nerve- treat chemical/ biological treatment - scaffold

55
Q

Decellularised nerves conduits

A
  1. Decellularised nerve provides 3D scaffold to support nerve regeneration
  2. Clean pathways allow cell migration and axonal regeneration
  3. Axon regeneration is well distributed throughout the nerve thickness
  4. Functional incorporation of the nerve conduit
56
Q

Bioengineering of conduits

A 
Bottom up approach 
- biodegradeability 
biochemical signals 
incorporation of support cells 
electrical activity 
intraluminal channels 
oriented nerve substratum
57
Q

Natural materials for nerve conduits

A
  1. chitosan- low structural integrity, weak degradability, inflammatory- myelinated axon
  2. collagen- biocompatibility, degradeable, fragile- partial recovered nerve
  3. fibrin- easily manipulated, anigiogenic- glial cells
  4. fibronectin- low structural integrity- fibroblasts
  5. gelatin- low structural integrity, economic- schwann cells
  6. keratin- biocompatible- unmyelinated axon
  7. silk fibronin- biodegrable, biocompatible, increased structural integrity- Nervous tissue
58
Q

Synthetic materials for nerve conduits

A 
1. Biodegradable materials
Poly(lactic) acid (PLA)
Poly(lactic-co-glycolic) acid (PLGA)
Poly(caprolactone)
Poly(ethylene glycol)
2. Electrically active materials
Electrically conducting
Piezoelectric
3. Non-biodegradable
Silicone
Gore-Tex
59
Q

Commercial nerve guides

A

Neurolac (2005) PLCL
Neuragen (2001) Type I collagen
Neurotube (1999) PGA
* all FDA approved

60
Q

Length limitations

A

The chance of successful regeneration with nerve guides is reduced, once an injury gap reaches a certain value
At short gap lengths, the fibrin cable is robust enough to provide a platform for regeneration
At longer lengths, thinning restricts regeneration
No fibrin cable at large lengths

61
Q

Critical gap length

A

Length at which regeneration occurs 50% of the time

62
Q

Approaches for increasing the Critical Gap Length

A
  • ECM components
  • cells grafts
  • intraluminal support
  • neurotrophic factors
63
Q

ECM components (matrices)

A

Matrices generally increase the critical gap length
Effective matrices are:
weak, viscoelastic hydrogels
with a high water content (high concentrations would prevent axonal penetration)
laminin, fibronectin and collagen

64
Q

Matrigel

A

promotes nerve regeneration, but is not suitable for clinic! batch to batch variability

65
Q

Intraluminal support

A

Hollows to promote regeneration

66
Q

Clinical case study gap of nerve injury

A

Significant gap in medial nerve in arm
taken nerve conduit and replaced stamps
results= patient regain appropriate function

67
Q

Neurotropic factors

A

support axonal growth,
migration and proliferation of Schwann cells
increase neuroprotection modulation of intrinsic signalling pathways
Nerve Growth Factor - Neurotrophin-3
Need for controlled release- means of delivery= diffusional based, suspension, affinity based and encapsulation

68
Q

Inclusion of cells within conduits

A

Schwann cells are critical for successful nerve regeneration
-Bands of Bungner
-Secrete neurotrophic factors
-Proliferate (4-17x increase in cell numbers)
The use of stem cells for grafting

69
Q

The role of vascularization in TE

A

Most tissues in the body contain a vasculatory network
Cells are located 100-200µm from capillaries
Differences in cells’ sensitivity to oxygenation
Tissues grown in the lab: bioreactors in vitro, but need vascularization in vivo

70
Q

Classical studies establishing the importance of vascularization of tissues

A

Folkman J (1971) “Tumor angiogenesis: therapeutic implications”
HYPOTHESIS: tumour growth is angiogenesis-dependant
1. vascularized angiogenic tumor
2. treatment with angiogenesis inhibitor
3. vessels begin to regress
4. tumor shrinks

71
Q

Vascularization needed in

A

a) early stages of tissue formation- 100micrometres thick
b) tissue growth and development- 500 micro metres
c) vascularization for TE

72
Q

The role of vascularization in TE constructs

A
  1. Avoid graft necrosis
  2. Generate thicker tissues
  3. Help graft innervation
  4. Improve graft function
73
Q

Blood vessels overview

A

Macrovessels (arteries and veins)
Microvessels (arterioles and venules)
Capillaries

74
Q

VASCULOGENESIS

A 
de novo blood vessel formation from progenitor cells
1. mesoderm 
2, hemogioblasts 
3. tube formation 
4. primary capillary plexus 
Blood vessel formation in embryo
75
Q

ANGIOGENESIS

A

From existing vasculature
Wound healing, ovarian cycle
1. VEGF - Smc pericyte recruitment- SMC/BM/endothelium
* physiological process through which blood vessels form from existing vessels

76
Q

VEGF

A

Vascular endotheial growth factor - endothelial cells proliferate, migrate and differentiate
VEGFA/B- vasculogenesis
VEGF C/D- endothelial cell proliferation/migration/survival, tumor angiogenesis, lymphangiogenesis

77
Q

ARTERIOGENESIS

A

Blood vessel remodeling as a response to fluid shear stress
Increase in shear stress causes endothelial cells to release GFs (TGFb)
Proliferation of endothelial and smooth muscle cells
Matrix remodeling
*(mechanical stimulation

78
Q

Main approaches for vascularization of 3D constructs

A
  1. Strategies for facilitating vascular ingrowth
    A. Scaffold design- Porous
    B. Scaffold functionalization
    Growth factor delivery - VEGF, PDGF, bFGF
    Controlled release of GFs is crucial!
  2. Prevascularization strategies
79
Q

Classical functionalized scaffolds to induce blood vessel formation study

A

” polymeric system for dual GF delivery”
mulitstep
VEGF- initiator of angiogenesis but not sufficient to induce mature vessels
PDGF- promotes maturation of blood vessels
Hypothesis= dual delivery VEGF and PDGF can direct the formation of a mature vasculature

80
Q

Study approach 2 Stage release of GF

A

Stage 1- release of VEGF to stimulate the growth of immature vessels
Stage 2- PDGF to faciliatate maturation of nascent vessels

81
Q

Results

A

Formation of a mature vascular network
a-smooth muscle staining
2 weeks after implantation

82
Q

Significance of the study

A

Multiple angiogenic factors were delivered
distinct kinetics of delivery allowing mimicking of natural processes
highlighted the importance of multiple GF delivery for engineered artificial tissue

83
Q

Disadvantages of strategies for facilitating vascular ingrowth

A

A time cosuming process
microvessel growth rate ~5micrometre per hour
may not be significant to prevent necrosis in 3D constructs after implantation

84
Q

In vitro prevascularization

A

The TE construct is cultured in vitro to build prevascularized structure

The prevascular network create a connection with the existing blood vessels in tissue (ANASTOMOSE)- faster than the new blood vessel formation!

  • Endothelial cells spontaneously self-assemble into capillary-like structures
  • Sources of cells
  • Issues with using mature endothelial cells
85
Q

In vivo prevascularization

A

Angiogenic ingrowth

  1. A scaffold is implanted into easily accessible and well vascularized tissue
  2. Microvessels ingrowth from the host
  3. After vascularization, implant is transferred to the defect site
86
Q

In vivo prevascularization 2

A

Flap technique

  1. A scaffold is implanted into a muscle flap
  2. Microvessels ingrowth from the host
  3. After vascularization, the entire flap is transferred to the site in the need of repair
  4. The vascular pedicle of the flap is surgically anastomosed to host vessels
87
Q

In vivo prevascularization 3

A

Arteriovenous loop technqiue
AV
uses veins or synthetic graft to form shunt loop between artery and vein
1. Allows tissue construct vascularization but the tissue is not embedded in the surrounded muscle tissue
2. No major morbidity at the donor site

88
Q

What is limited oxygen diffusion restricting?

A

The size of the successful tissue engineered construct

different strategies promote neovascularization of TE constructs

89
Q

What considerations need to be made about vascularization?

A

Scale up
cost
minimal invasiveness

90
Q

+ and - of scaffold design

A

+ versatile, easy to develop and translate to multiple tissues
- still relies on vessel ingrowth, limited result, can introduce seeding problems

91
Q

+ and - of in vitro prevascularization

A

+ doesnt rely on ingrowth of host, no extra surgery,

- complex, vessel maturation need attention, anastomosis not as fast

92
Q

+ and - of in vivo prevascularization

A

+ direct perfusion after surgery, mature

- extra implantation/surgery, finding proper location, scaffold might be filled with porous tissue

93
Q

+ and - of angiogenic factor delivery

A

+ angiogenic factors effective

- still relies on vessel ingrowth, factors might have neg effect on tissue, release profile of factors is critical

94
Q

Cell basis studies for eye disease

A
  1. limbal production from PSCs corneal endothelium regrowth
  2. improving adult LEC growth
  3. replcae TM with healthy stem cell derived TM cells and restore 10p regulation
  4. transplantation of adult RIPESC derived RPE progenitor cells, RFE on biodegradable, Hspc photoreceptor progenitor/derived RGCs
95
Q

Corneal disease

A

Second leading cause of vision loss

10 million people across the world with vision loss due to this

96
Q

Corneal function

A
  1. aid sight
    - transparency
    - refractive power= focus on retina
  2. eye protection- dust and microbes
97
Q

Structure of cornea

A 
Cornea epithelium 
bowmans membrane 
corneal stroma 
descemet membrane 
corneal endothelium
98
Q

Epithelium of cornea

A

Outermost layer
thickness= 50 micrometres
highly innervated
function= prevent fluid loss, create barrier to pathogens, respond rapidly to wounding

99
Q

Regeneration of epithelium

A

Constantly in a state of turnover- whole layer every 5-7 days

100
Q

Stroma

A

90% of corneal thickness
relatively accellular
collagens, prosetoglycans, glycoproteins
function= provide strength and transparency
Keratinocytes in cornea= long, thin, flattened cells- maintain ECM

101
Q

Endothelium

A

A single layer of cells
metabolically active
function= maintain stoma hydration, important for corneal transparency

102
Q

Function of the leaky pump in the endothelium

A

Solutes and nutrient from aqueous humour
active pump to draw water from stroma
metabolically active- full of mitochondria and atp for allow water in and pump back out

103
Q

Corneal innervation

A

Densely innervated body structure
sensory nerves
important for blink, wound healing and tear production

104
Q

Blood vessel supply to cornea

A 
Avascular supply 
Allow transparency and get vasculature from tear fluid 
- muscular artery 
- anterior cillary artery 
- conjunctional artery 
- deep episcleral plexus 
- congenital vein
105
Q

Ideal corneal substitute

A

Transparent, refractive, prevent angiogenesis, adequate mass transport

106
Q

Which layer of the eye is most amenable?

A

Epithelium as regenerate every 7 days

107
Q

Corneal transplantation

A
  1. damaged cornea removed
  2. donor cornea in place
  3. sutures
108
Q

Medical devices

A

Keratoprosthesis

  • patients with repeated failed grafts
  • life long regime of antibiotics
  • medications to control inflammation and gluvcoma
109
Q

Different eye layer diseases

A
  1. epithelial disease- limbal stem cell dificency
  2. stomal disease- dystrophy
  3. Endothelial disease- bullous keratopathy
110
Q

Epithelial wound healing of limbal epithelial stem cells

A

Located on corneal rim at the border between sclera and cornea
undilated niches- see this in some people

111
Q

The limbal epithelial stem cell proliferation/differentiation

A

Limbal stem cells – asymmetric division
Transit-amplifying cells – divide rapidly in the basal cell layer
Post-mitotic cells – wing cell layer
Terminally differentiated cells – squamous layer

112
Q

LSC deficiency

A
  1. Congenital- aniridia, sclerocornea
  2. external- thermal, alkali, acid burns, pseudopermphigoid
  3. internal- stevens johnson syndrome, ocular pemphiogoid
113
Q

Regenerative medicine treatment using limbal stem cell (LSC) transplant

A
  1. healthy eye
  2. direct transplant to disease eye
  3. healthy limbal epithelium used to seed a culture to produce a sheet of epithelial cells- diseased eye
    - 37 degrees= change PH allow denature of sheet
    - 20 degrees
114
Q

Cultured limbal studies

A

Studies using expanded limbal stem cells demonstrated that the ocular surface in patients with ocular burns can be restored
“ long term restoration of damaged corneal surface with autologous cultivated corneal epithelium”

115
Q

Holoclar method

A

Europes first stem cell therapy
cornea- biopsy- cell extraction- primary cell culture- freezing until patient ready for surgery
secondary culture- 1 batch= 1 patient - shipment- surgery

116
Q

Holoclar study

A

74/104 patients showed stable corneal suface with no defects, little or no grown blood vessels, reductions in pain/ inflammation and improvement in vision

117
Q

Advantages and disadvantages of autologous limbal stem cell implant

A

Patients own cellls, capitulate function well

genetic problem cant use own cells, delay to make graft, potential damage

118
Q

Other sources of cells for corneal epithelium

A

Where limbal not possible
patient with difficient sc- oral surgery- oral mucosa tissue- culture- harvest cell sheet- culturvated oral mucosa epithelial sheet- transplant

119
Q

Pos and neg of oral mucosa

A

Pos- no scarring in the mucosa

neg- a risk of neovascularization of the cornea

120
Q

Stromal injury and wound healing

A
  1. stroma
  2. release Il-1, TNF-a
  3. Activate keratinocyte to fibroblast and myoblast
  4. done by transdifferentiation using TGF-b
  5. apoptosis or sourction of irregular ECM and haze
121
Q

Regenerative approaches for corneal stucture

A
  1. Biomaterials-based

2. Cell-based

122
Q
  1. Biomaterials-based
A 
Acellular at the time of implantation
Promote repopulation by the host’s cells and innervation
A range of materials: 
-decellularised cornea
- collagen (+recombinant)
- self-assembling peptides
123
Q

Advantages of biomaterial based approach for stroma replacement

A

Recombinant human collagen cell-free implants
Endogenous cell recruitment
Regenerated neo-corneas stably integrated
No need for immune suppression
Nerve and stromal cell repopulation

124
Q

Disadvantage for biomaterialbased approach for stromal replacement

A

Visual acuity could be improved (better materials

125
Q

Study for biomaterial enabling cornea regeneration in patients at high risk of rejection of donor tissue transplantation

A

recombinant human collagen and a synthetic lipid
7 patients
implants improved vision and relived pain

126
Q

Cell-based approach for stromal replacement

A

Limbal stromal stem cells:
- Remodel stromal scarring in model animals
- Suppress fibrotic scar formation
LV Prasad Eye Institute, ongoing clinical trial

127
Q

Challenges for Tissue Engineering the Cornea- Recreating epithelium

A

Recreating epithelium:
Continuous replacement of the epithelial cells
Maintaining integrity as a barrier
Optical transparency

128
Q

challenges for TE in recreating stroma

A

High tensile strength

Optical transparency

129
Q

endothelial regeneration

A

Human corneal endothelium does not regenerate!
Endothelial cells have a finite life span leading to a decrease in density with age
At birth: 3500-4000 cells/mm2 -> only 2300 cells/mm2 by age 85
Minimum amount necessary for function is ~500 cells/mm2

130
Q

challenges for endothelial regeneration

A

Limited proliferative ability in culture
Can be ‘immortalised’ but that has implications for both research and the clinical use
Recent development: Can be derived from pluripotent stem cells (PSCs)

BMS354 Tissue engineering (5 decks)

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