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Tissue Engineering: Artificial Pancreas
#1
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Tissue engineering is combining latest technological discoveries, materials and methods with living cells to replace, repair or improve affected organ.

List of tissues and organs that are manufactured in laboratory using engineering techniques is long, but some of the most famous are:
In-vitro meat, bioartificial liver device, artificial pancreas, bone marrow, skin, bladder, vessels etc

This type of engineering utilizes living cells as building elements. Using enzymes, cells could be extracted from the solid or liquid environment (depending of the cell type and tissue) and further manipulated.

Cells used for engineering could be:
  • Autologues (donated by the same person that will use artificial organ/tissue)
  • Allogeneic (when derived from the same species)
  • Xenogenic (when derived from other species)
  • Syngenic or isogenic (isolated from twins or clones)
  • Primary (when donated by organism)
  • Secondary (when donated by cell bank)
  • Stem cells (with multiple application as they could differentiate in every cell line needed)

Organs have specific structure and cellular organization that are associated with the role they play in the body. Tissue engineering is examining cellular architecture to design artificial organ to resemble real one as much as possible. Isolated or donated cells are incorporated in “familiar” environment, where solid structure providesbiomechanical stability. This structure, called scaffold, acts as a frame forfuture organ.

Beside stability, it allows diffusion of necessary nutrients, delivers and retains cells and biological factors, allows cellular migration and attachment. Some scaffolds are made out of biodegradable materials as they need to break down once organ of interest is regenerated. Collagen, fibrin, chitosan or glycosaminoglycans are examples of naturally derived materials used for scaffold manufacture. Synthetic materials such as polylactic acid, polyglycolic acid and polycaprolactone are often used as they degrade to lactic acid that can be easily removed from the body.

Tissue culture demands certain oxygen level, temperature, humidity, osmotic pressure…for normal functioning. As culture is growing bigger, other mechanisms are added to ensure further working of the system (diffusion as only mechanism for nutrients exchange could be “upgraded” with capillary network, for example). Hormones, growth factors and chemical or physical stimuli (such as physical pressures applied on cardiovascular tissue) are essential for normal tissue/organ development.

Pancreas is organ with numerous functions. It works as endocrine gland producing hormones that regulate blood sugar level and as exocrine organ, producing enzymes essential for proper food digestion. Most famous and spread illness resulting from pancreas dysfunction is diabetes. Every 1 out of 400 children have diabetes as well as 11.3% of adults over 20 years and 26.9% of people over 65 years. People suffering from diabetes need to monitor blood sugar level regularly and prevent hyperglycemic crises by injecting insulin subcutaneously. Main goal of artificial pancreas is to ease the insulin therapy or to improve the insulin replacement therapy.

Couple approaches are used: gene therapy, artificial organ development and insulin pumps that are monitoring blood sugar level continuously.
 
Gene therapy uses viral vectors equipped with insulin sequence. After orally ingested, virus will deliver its genetic information to the upper part of the intestinal tract. Infected cells are acting like any virus containing cells by replicating newly derived genetic material. If targeted delivery is made and cells responsive to glucose are infected – full control may be achieved (insulin will be produced only when needed). Cells containing insulin sequence will die after some time (intestinal cells don’t have long lifespan) and new cells will be infected with additional oral medication. Another way to use gene therapy is to turn duodenum cells into beta cells by delivering beta cell DNA. Some of the cells will turn into insulin producing beta cells that could divide further and ensure stable and self renewable number of beta cells in duodenum.

Artificial pancreas is created using mesh of fibers (ensuring strength), encapsulated clusters of islet cells (to avoid immune response), semi-permeable coating (to ensure normal diffusion of nutrients and hormones) and biocompatible outer layer (to keep them all together without inducing fibrotic response). Main goal is to ensure normal functioning of islet cells, where insulin, glucagon and amylin will be secreted in response to glucose in the blood.

Some of the insulin pumps with continuous monitoring of blood sugar level are already in the clinical trials. Glucose sensor need to be inserted in the neck vein. Electric wire transmits information on glucose level to the insulin pump that is releasing necessary dose of insulin. Those devices proved to be effective, but glucose sensor doesn’t last long and needs to be replaced every 9 months.  

It may sound like science fiction, but era of artificial organs and tissue engineering is our reality. Saving lives, making treatments easier, eradicating serious illnesses – it looks promising for sure.
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#2
Tissue engineering

Tissue engineering can perhaps be best defined as the use of a combination of cells, engineering materials, and suitable biochemical factors to improve or replace biological functions.

While the semi-official definition of tissue engineering covers a broad range of applications, in practice the term has come to represent applications that repair or replace structural tissues (i.e., bone, cartilage, blood vessels, bladder, etc).

These are tissues that function by virtue of their mechanical properties.

A closely related (and older) field is cell transplantation.

This field is concerned with the transplantation of cells that perform a specific biochemical function (e.g., an artificial pancreas, or an artificial liver).

Tissue engineering solves problems by using living cells as engineering materials.

These could be artificial skin that includes living fibroblasts, cartilage repaired with living chondrocytes, or other types of cells used in other ways.
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