Cardiovascular diseases, including coronary artery diseases, are a major cause of mortality worldwide. Consequently, there is a pressing need to develop small-diameter vascular vessels for bypass surgery and other vascular reconstructive procedures. Tissue engineering offers the prospect of being able to meet the medical demand, as it allows the development of small and structurally complex blood vessels substitutes1. Accordingly, the final aim of this work is to develop small diameter vascular substitutes based on layering multiple cell types (i.e. endothelial, smooth muscle and fibroblastic cells)2. For that, we used the electrospun nanofibrous meshes, which restrict cell migration, although allowing intercellular interlamellar cross-talk provided by the mesh’s pores, enabling biochemical communication3.
To mimic the structural organization of a blood vessel, co-culture systems were established, namely human endothelial-smooth muscle cells and fibroblastic-smooth muscle cells. Additionally, these co-cultures were assembled to develop a tri-culture system with endothelial-smooth muscle-fibroblast cells.
Biological results indicate that in both co-culture conditions was possible to observe an increase in cell viability from 1 to 3 days, followed by a slight decrease on day 7. Conversely, cell proliferation increased in the endothelial-smooth muscle cells co-culture, while the fibroblasts-smooth muscle cells co-culture showed a slight decrease over time. Furthermore, both co-cultures showed constant levels of protein synthesis over time. From the SEM micrographs of both co-culture systems was possible to observe that the endothelial, smooth muscle and fibroblastic cells remained morphologically stable, even in the presence of another cellular type.
Concerning the tri-culture system, cell viability presents a similar trend to the co-cultures, while the proliferation pattern only resembles the fibroblasts-smooth muscle cells co-culture. Interestingly, the tri-culture system presents values of protein synthesis much higher than the co-cultures, demonstrating the potential inter-cellular communication mediated by soluble proteins. Quantification of secreted growth factors, namely platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), present in conditioned media showed increasing levels of VEGF and bFGF compared to mono-cultures. By its side, PDGF levels remained practically unaltered among conditions.
These experimental results demonstrated an improved intercellular cross-talk between endothelial, smooth muscle and fibroblastic cells, reinforcing the potential of tissue engineering in the development of blood vessel substitutes.
The Portuguese Foundation for Science and Technology for the project VESCells PTDC/BBB-BMD/5468/2014 (POCI-01-0145-FEDER-016909) and the IF grant of A.M. (IF/00376/2014).