Tissue Engineering

...

is no risk of rejection although it is uncertain whether the transplant will survive and grow. Another disadvantage of autografting is that there is a limit on how much tissue can be harvested and the process of harvesting tissues include surgical procedures which incur large costs ad have the risk if infections, blood loss and pain.

Allografting is the process of obtaining natural tissue from a donor than transplanting to the recipient. These procedures include blood transfusions and usually involve organ structures. A benefit of allografting is the procedure allows for the complete recovery of a lost/non functioning organ. A major disadvantage of allografting is there is a lack of donors. In addition, should a recipient receive an allograft, there is a high risk of rejection of the transplanted tissues. Thus in order to prevent rejection, the recipient must receive life long anti-rejection medication. Furthermore, some tissues have a limited life span, such as kidneys which have a 10 year life span. As a result, allograft recipients would be required to undergo another procedure in the future.

Xenografting: Xenografting is the harvesting of tissues from one species to another. Examples of this procedure include the implantation of human tumour cells into immunocompromised mice for research purposes, the use of porcine heart valves in human heart valve replacement surgery prior to the development of engineered heart valves and the use of porcine insulin to treat diabetes prior to the development of human recombinant insulin. Human xenotransplantation offers a potential treatment organ failure and could alleviate the deficit of allograft donors. Xenografting procedures have a lot of disadvantages such as the extremely high possibility for rejection. In addition, ethical issues such as the risk of xenozoonosis (disease transmission), the ban of specific animal consumption due to cultural/religious beliefs, and the rights of animals are introduced with this procedure.

Medical Implants are often permanent implants that are created by scientists and engineers to restore, improve or maintain tissue function. Examples of such implants include prosthetic hips, breast implants and artificial hearts. An advantage to medical implants is that the implants can replace the most of the function of the natural tissue. In addition, the materials used for implants can not be destroyed by an immune response. Conversely, the implants may cause inflammation and are subject to wear and tear, toxicity and fracture due to the materials they are made of, which result in the implants having a defined lifespan, which in turn will require implant recipients to undergo further expensive and dangerous surgeries in the future.

Tissue engineered products also restore, improve or maintain tissue function but are newly generated tissue constructs. Examples would include the in vitro growing of skin for a skin graft or the use of a patients stem cells to place on a scaffold and implanting back into the patient to regenerate fully functioning bone, muscle or potentially organs. Tissue engineered products would alleviate the current tissue donor deficit and would overcome the problem of allograft/medical implant lifespans. Furthermore, the use of a patients own cells for generation of the tissue constructs would eliminate implant rejection and the need for life long anti rejection medication. Unfortunately, the production of functional tissue constructs improving to be the largest obstacle. Although the general structure of the tissue can be produced, the organelles, blood vessels and other complex structures required for the tissue to function at its optimal capacity has not been achieved yet.