The vascularization of fabricated tissues presents a considerable challenge to tissue engineers. Tissues thicker than three cell layers cannot maintain physiological function (gas transfer) without vesicular perfusion. Even when tissues are implanted into the body, blood vessels can fail to form, resulting in implant tissue death.
When native tissues suffer from lack of oxygen they release Hypoxia Induced Factors (HIFs) which spark the production of Vascular Endothelial Growth Factor (VEGF). VEGF in turn begins a biochemical cascade which results in vessel formation from the walls of existing vessels, satisfying the starved tissue’s need for nutrients and waste disposal.
To facilitate this process for implanted tissues, researchers at Wake Forest University have recently developed an injectable collagen-based gel which contains the chemical messenger VEGF in minute concentrations. The gel releases 100 ng of VEGF to an isolated area of injection over the course of 12 days, promoting vessel development at a designated implant site. Vessel development increases the chance of implant survival, and researchers hope to extend the period of VEGF release to ensure vascularization.
The molecular structure of gelatin makes this extended release possible. Gels, composed of a molecular matrix (in this case collagen), trap water within its structure. In addition to water, the matrix can be loaded with a solution containing chemicals such as VEGF, and depending on matrix porosity, the rate of release (of the chemicals/solution contained within) can be controlled.
The gel has shown promising results in small animal trials, with findings published in the Journal of the American College of Surgeons. To learn about other scientist’s attempts at tissue vascularization, read more here.
