The project has focused on understanding how different factors, including patterned fluid flows and patterns of growth factors, influence vascular organization. Microfluidic platforms have been developed to investigate the combinatory effect of varying fluid flow profiles and growth factor gradients on vascular organization. To further understand what drives vascular organization, computational models were developed to predict organization based on multiple signals such as fluid flows and growth factors. These models were further refined and validated using data arising from cell culture experiments and from the observation of vascular organization in developing chicken egg models. These computational models enable a direct link between a desired vascular organization, and the tissue construct geometry and processing conditions that are needed to acquire this organization.
VascArbor has developed a novel technology based on aptamers to spatiotemporally pattern growth factors within a hydrogel tissue environment. Aptamers are small, single-stranded pieces of RNA that form unique 3D conformations based on their sequence. This enables selective binding to target biomolecules such as growth factors (GF) with high affinity and specificity. Complementary sequences (CS) having higher affinity towards the aptamers than the target GF can be added, resulting in demanded GF release upon aptamer-CS binding. This results in a temporal control over growth factor availability. As the hydrogels are compatible with photopatterning and 3D printing technology, spatial control over growth factor availability is also achieved. Based on this technology, an ERC Proof of Concept grant has been granted.
Additionally, two novel embedded bioprinting approaches have been developed. One is based on the printing of highly packed granular media. This technology is highly interesting to create patterned embedding baths. Multiple formulations of granular embedding baths have been investigated in terms of vascular network formation. Based on this technology, a patent has been filed and an ERC Proof of Concept grant has been granted. The other approach uses a viscous liquid as embedding bath. This approach allows for the concentration of cells within a 3D print, meaning that dilute cell suspensions can be printed which are then concentrated into a dense tissue. This has enabled the formation of macroscale beating cardiac tissue constructs.
Additionally, several perfusion bioreactor systems have been developed to accommodate tissue constructs of different sizes and shapes. These perfusion systems allow for control over fluid flow profiles within engineered tissue constructs in order to guide vascular organization and development. Combined, the project has resulted in new tools to tune the cellular environment within engineered tissue constructs, which is valuable for tissue engineering research in general. Additionally, by better understanding the signals that guide vascular organization within engineered tissues, combined with new technology to pattern these signals, the project has enabled a better control over vascular organization. Although full control to engineer a network organized as a vascular tree has not been achieved, important tools towards this goal have been developed.
