Bio artificial pancreas BAP: cells, matrix and in between

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Development of Bio-Artificial Pancreas
Laboratory of Diabetes Research, Felsenstein
Medical Research Center, Faculty of Medicine, Tel
Aviv University
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TYPE I DIABETESChallenges

• Prevention of diabetes
• Improve life of diabetic patients
• Reverse insulin dependent state

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Endogenous Insulin Secretion
Insulin response
Daily insulin secretion profile
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Reversal Of Insulin Dependency

• Closed-loop artificial pancreas
• (engineered sensing and insulin delivery)
• Transplantation of insulin-producing cells
• (natural sensing and insulin secretion)
• Induction of insulin production in non beta-cells
  

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Engineered BG Sensing And Insulin Delivery A
suboptimal solution
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Whole human pancreas Weighs 70 g
Contains 1 000 000 islets 1-2 500-1500
cells1 islet 80 - beta cells
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The Islet Transplant
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Islets Transplantation Obstacles

• Cells Source
• human, animals, stem cells
• Protection from autoimmunity and rejection
• general, local

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Protection Approaches

• General
• Immunosupression drugs
• Local
• Immunoisolation, using matrix
• with controlled trans-membranal
• passage of compounds

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600
Pre-transplant
500
400
Blood glucose (mg/dl)
300
200
100
0
600
500
Post-transplant
400
300
Blood glucose (mg/dl)
200
100
0
2
4
6
8
10
12
2
4
6
8
10
12
a.m.
p.m.
Time of day
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Edmonton protocol (2003)Complications related
to therapy

• Portal vein thrombosis (n2/54)
• Expanding hematoma requiring surgery (1/2)
• Bleeding (n4), requiring transfusion (3/4).
• Transient disturbed liver function (46).
• Development of hypercholesterolemia (65)
• Development of hypertension (53).

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Immunoisolation suboptimal solution

• Free trans membranal penetration of small
  injurious molecules (cytokines, free radicals)
• Islet central Hypoxia

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Bio-artificial Pancreasresearch targets

• Cell engineering
• Matrix Selection
• Islets oxygenation

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Cell Engineering

• Beta-cell low defense system is reflected by
• Beta-cell high fragility to
• Autoimmunity
• Infectious agents
• Chemical toxins

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H202-Dependent ?-cell Injury

• H202 produces highly toxic hydrogen radicals,
  causing lipid peroxidation and cell death.
• The ?-cell is extremely sensitive to oxidative
  stress induced by H202 due to very low level of
  catalase (enzyme accountable for H202
  inactivation) in ?-cell

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Improvement Of Beta Cell Defense
Capacity(literature reports)

• Gene transfection and overexpression of
• Anti-oxidants
• (catalase, glutathione peroxidase)
• Anti-apoptotis
• (Bcl-2)

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Cell selection technology
Exposure to H2O2, STZ, Alloxan, cytokines
Resistant cells
Mass production
Immunoisolation in BAP
Transplantation
Bloch Vardi,, Diabetologia, 1998
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H202 selection ProcedureResults
CAT
RINmHP
RINm
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Bio-artificial pancreas research targets

• Cell engineering
• Matrix Selection
• Islets oxygenation

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Polymeric Matrix Requisites

• Semipermeable, cell supporting, and cell
  protective system
• Biocompatible
• Highly porous (oxygen diffusion, prevents islets
  clumping)
• Induce blood vessels formation
• Mechanically stable
• Easy insertion and removal

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Alginate commonly used natural polymer for cell
immunoisolation
Non-toxic Non immunogenic
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Islets Morphology In Cryogel Sponge Culture
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Reaction Of Islets Transplanted In Macroporous
Cryogels

• Higher basal insulin secretion after short and
  long culture in cryogel
• Fail to respond to high glucose stimulation after
  14 days
• 2-fold lower insulin content

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Bio-artificial pancreas research targets

• Cell engineering
• Matrix Selection
• Islets oxygenation

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Immunoisolation Barriers
Lack of oxygen
Fibrosis
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Hypoxia-induced Central Islet Necrosis
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Devices Designed To Improve O2 Supply To
Transplanted Islets

• Addition of 02carriers
• (c Ricordi)

• H20 electrolysis
• (C Colton)

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How to overcome the obstacle of insufficient O2
diffusion Is it possible to develop a
miniature oxygen generator
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Photosynthesis
light
6H2O 6CO2 ------gt C6H12O6 6O2
Carbon dioxide is converted to sugars
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Earth atmosphere
Atmospheric oxygen built up in the early history
of the Earth as the waste product of
photosynthetic organisms (micro-algae)
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Algae
Unicelullar algae
Multicellular algae
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Alga Requirements

• Thermophylic
• Non toxic
• Photosynthesizing

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Microalga Adaptation To Extreme Environment
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Microalga Symbiosis
The green color of sea anemone, hydra and coral
is due to symbiotic algae living within their
tissues.
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Pancreatic islets/microalge co-culture
encapsulated islets
encapsulated algae islets
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Chlorella Diameter 1 um Temperature
37C Non-toxic, edible
10 algal cells compensate the respiration of 1
islet cell
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• System optimization
• Light intensity
• Algal cell density
• Algae Islets ratio
• Medium for both

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Effects of irradiance and algae density on
photosynthetic 02 production
irradiance
cell density
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Determination of algal cells number able to
compensate pancreatic cells oxygen consumption at
2 different irradiances. 10 alga cells are
sufficient to compensate the respiration of 1
islet cell
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Alga/islets co-culture Perifusion test under
anoxia

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Micro-alga as Photosynthetic Oxygen Generator
for Bio-Artificial Pancreas
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Light Emitting Diodes ( LEDs )
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In a celebrated experiment in 1772, Joseph
Priestley kept a mouse in a jar of air until it
collapsed. He found that a mouse kept with a
plant would survive.
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The Team
K Yavriyanz
P Vardi
K Bloch
M Vorobeychik
Collaborators
Lozinsky V Moscow State University, Russia
Beer S Tel Aviv University Israel
Galaev I Lund University Sweden