Chapter 1 - Introduction to Tissue Engineering

tissue engineering

interdisciplinary technology, emerged 30 years ago, draws significant attention, ability to construct biological substitutes to repair and replace diseased and damaged tissues

tissue engineering technology has already been used in…

clinical applications, developing effective therapies (for skin, blood vessels, liver)

new techniques

microfabrication, additive manufacturing

organ shortage

huge success in organ transplantation has led to an increase in demand for transplantable solid organs

current therapies for tissue substitutes

organ transplantation, medical device

organ transplantation (tissue transplantation)

autografting, allografting, xenografting

autografting

tissue transplanted from one part of body to another part in the same individual (ex, skin/bone graft)

autografting advantages

no rejection, best clinical results, no disease transfer

autografting limitations

limited available tissues, high surgical costs/second surgery, potential complications

allografting

use tissue/organ donated by living/deceased donors

allografting advantages

prevents need for second surgery, immediate structural support

HOTA

Human Organ Transplant Act (Singapore) - organs can be recovered in event of death for transplantation; those who remain under act have higher transplant priority if needed in future

allografting limitations

donor shortage, high rejection, health of donor, disease transfer, material characteristics can change between batches, less consistent results

xenografting

tissue/organ taken from animal sources and transplanted into human body

xenotransplantation

procedure involving transplantation, implantation, infusion into human recipient of either live cells, tissues, organs from nonhuman animal source, or human body fluids, cells, tissues or organs that have had ex vivo contact with live nonhuman animal cells, tissues or organs

xenografting advantages

broadens supply of tissue sources, production of transgenic animals which contains organs functionally similar to human will be possible in future

xenografting limitations

tissue rejection, disease transmission, cross species infection , infectious agents, ethical concerns

medical device

Defined by FDA - an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including component part or accessory, which is recognized either in US Pharmacopoeia or National Formulary, is intended to be used in diagnosis, cure or prevention of disease, for human or animal, or will have significant impact on body structure or function of humans or animals

Medical Device/Implants

artificial organ, implant, device - as a bridge to tissue transplant, not a natural solution, material or design independent

Artificial organ

heart, lung, trachea

implant

hip, knee, intraocular, cochlear

device

hearing aid, prosthetic

transplantation

most extreme form of reconstructive surgery transferring tissue and organs from donor into patient

constraints of transplantation

access, chronic rejection and destruction by immune system, dislodgement/migration/fracture/infection

scaffold

matrix used to guide development of tissue - highly porous 3D substrate

tissue engineering process

cells taken from patient expanded in culture, transferred to scaffold, cells proliferate and generate essential elements making up living tissue - with human body, must be near capillary network to obtain oxygen/nutrients, so scaffold must be supplied this to maintain life using its highly porous open structure

3 key elements to tissue engineering

relevant selection of cells, biomaterial scaffold for 3D culture, and presence of appropriate signals such as biophysical cues and chemical mediators that coordinate to ultimately recreate tissues

extracellular matrix (ECM)

composed of glycosaminoglycans (GAGs), proteoglycans, fibrous proteins (collagen, elastin, etc)

ECM functions