Towards in vitro vascularisation of collagen-GAG scaffolds

Collagen-glycosaminoglycan scaffolds that have been used clinically for skin regeneration have also shown significant promise for other applications in tissue engineering. However, regeneration of thicker tissues with the aid of implanted biomaterials is likely to depend on, or be accelerated by, the ability to establish rapid vascularisation of the implant. The present study aims to establish a nascent vascular network in vitro within a CG scaffold as a first step towards that goal. Mesenchymal stem cells (MSCs) were chosen as primary vasculogenic candidate cells and a culture medium that promoted maximal network formation on Matrigel by these cells was selected. MSCs seeded in the CG scaffold formed networks of cord-like structures after one to two weeks in the presence of the vasculogenic medium; similar structures were formed by aortic endothelial cells (ECs) cultured for comparison. Gene expression analysis suggested that the MSCs began to adopt an endothelial phenotype, with RNA for PECAM and VCAM rising while that for alpha-smooth muscle actin fell. However there was no increase in Tie-2 and vWF expression. Addition of smooth muscle cells (SMCs) as a potential perivascular stabilising component did not have a noticeable effect on MSC-derived networks, although it enhanced EC-derived structures.