PMC

Controlled growth factor release from a biomaterial scaffold. A time-dependant release of multiple growth factors is necessary to facilitate the regeneration of a complex organ. Here the delivery of an angiogenic growth factor (circle) is followed by the delayed release of a tissue specific growth factor (triangle). The spatial control of growth factor concentration can also be incorporated into the biomaterial to allow for guided cell migration and tissue regeneration.

Patient-specific tissue engineering. The recent discovery of iPS technology has offered the potential of patient-specific cell therapy. A small skin biopsy could be obtained from a patient in need of an organ or tissue replacement, from which dermal fibroblasts would be isolated and expanded in vitro. These fibroblasts can then be reprogrammed into iPS cells whose pluripotency could be exploited to differentiate the iPS cells into any patient-specific cell type (i.e., neurons, hepatocytes, etc.). The patient-specific cells can then be incorporated into a biomaterial scaffold and implanted back to the patient at the damaged tissue site.

Organ-level tissue engineering paradigm. The basic strategy used by scientists to bioengineer tissues has changed little from the very beginnings of the field of tissue engineering. A biomaterial is utilized as a structural and mechanical scaffold into which a specific cell population is incorporated. Growth factors and other bioactive molecules can be added to the construct. After a period of maturation either in vivo or in a bioreactor, the anticipated end product is a tissue-engineered organ that serves as a functional replacement for damaged or missing tissue.

Biomaterial strategies for organ-level tissue engineering. Several emerging technologies in biomaterial scaffolds offer the promise of scaling up the size and complexity of tissue engineered constructs. “Organ printing” (A) is the use of inkjet printing techniques, which allows precise control over placement of cells and polymers deposited within a “bioink” and has been used to form tubular vascular structures. Recent advances in decellularization protocols using detergent perfusion have demonstrated promising results in the complete removal of cells from large visceral organs (B). These decellularized matrices maintain their structure and mechanical properties without containing immunogenic donor cells. The use of autologous explanted microcirculatory beds (EMBs) allows tissue engineers to circumvent the challenges of creating vasculature de novo (C). EMBs can be harvested, implanted within a hydrogel scaffold, manipulated ex vivo including cell perfusion and reimplanted at the site of tissue damage.