Tissue Engineering

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Tissue Engineering
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What is Tissue Engineering?

• Emerging interdisciplinary field that applies the
  principles of biology and engineering to the
  development of viable substitutes that restore,
  maintain, or improve the function of human
  tissues.

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Why Do We Need TE?

• Every year, millions of surgical procedures are
  performed that require tissue or organ
  substitutes to repair or replace damaged or
  diseased organs or tissues.

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Conventional Approaches (4)
Autografting
Xenografting
Allografting
Man-Made Devices
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Conventional Approaches

• (1) Autografting
• Harvesting a tissue from one location -
  transplanting it into another part of the same
  patient.
• Rejection is not an issue.
• Example procedures include
• coronary bypass (i.e., veins grafts are removed
  from the leg, then transplanted to the heart as a
  conduit for blood flow around blocked coronary
  arteries)
• spinal fusion (i.e., a bone graft from the
  patient's hip is used to stabilize a segment of
  the patients spine).
• Problems surgical costs infection and pain at
  the harvesting site

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Conventional Approaches

• (2) Allografting
• Harvesting tissue/organs from a donor and then
  transplanting it to the patient.
• The donor might have recently died and donated
  heart, kidney, liver, bone, pancreas, etc.
• Living donors might also be used to donate lungs,
  kidneys livers.
• anti-rejection drugs better
• shortages worse

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Conventional Approaches

• (3) Xenografting
• Tissues / organs from animals into humans
• Tissue rejection disease a huge concern
• Transgenic animals that are recognized as human

Video 1 (13 min.)
Video 2 (6 min.)
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Conventional Approaches

• (4) Man-Made Materials and Devices
• Devices to replicate, augment or extend functions
  performed by biological systems.
• Examples
• artificial hearts/valves
• prosthetic hip
• materials used subject to fatigue, fracture,
  toxicity, inflammation, wear, and do not remodel
  with time)
• Thus, devices like an artificial heart are best
  suited as temporary therapies until a donor organ
  becomes available.

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Not-So Conventional Approaches

• Design/grow human tissues outside the body for
  later implantation skin grafts for over 15
  years
• Implant devices that induce the regeneration of
  tissue bone regrowth
• Use human tissues to replace diseased tissues
  stem cells

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Whats Involved?
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Know Your Tissues!
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A Bit of Bone Biology
Periosteum
Osteoclast
Osteoblast
Compact Bone
Epiphyseal Plate
Spongy Bone
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General sequence of Bone Fracture Repair
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The Ideal Scaffold
Synthetic Scaffold
Normal Response
Osteoblasts Arrive
Most Blood Leaves
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The Ideal Scaffold
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Scaffold Issues (4)

• (1) Cell Concentrations
• Cells migrate to the outside
• Should be more uniform
• Why is it impractical to infuse the scaffold with
  cells while making it?

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Scaffold Issues

• (2) Vascular Supply
• If cells get to interior, need to be nourished
• Takes time
• Interior cells may die

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Scaffold Issues

• (3) Many Cell Types
• What types of cells would be required to grow an
  entire arm?

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Scaffold Issues
Strength
Intermediate
Porous
Flex
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Scaffold Issues

• (4) Growth Factors
• The right concentration of growth factors is
  required

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Whats Out There Now?

• Model of a synthetic scaffolding material

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Whats Out There Now?

• Made from sea coral
• Good to grow bone cells

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Whats Out There Now?

• Vessels

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Whats Out There Now?
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Whats Out There Now?

• Mouse has no immune system

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What About the Future?
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What About the Future?