Evaluation of the Angiogenic Effect of Elastin Incorporation on Silk Fibroin 3D Printed Scaffolds

INTRODUCTION: A novel enzymatically crosslinkable silk fibroin (SF) bioink has been developed for printing high-resolution reproducible 3D structures [1]. The potentiality/versatility of SF bioinks to be combined with different biomolecules for better mimicking native tissues has been recently investigated by introducing elastin for replicating the outer intervertebral disc [2]. In this work, the effect of elastin on the angiogenic response of SF bioprinted scaffolds was explored by using the chick chorioallantoic membrane (CAM) assay [3]. METHODS: The 16 wt% silk fibroin (SF) and silk fibroin/elastin (S/E) (ratio of 90:10, respectively) bioprinted scaffolds were cut into 4 mm diameter cylindrical discs and implanted on CAM at day 10 of embryonic development. Filter paper (FP) and gelatin sponge (GSp) discs were used as positive and negative controls, respectively. At day 14, the excised sections were prepared for histology after acquisition of in ovo and ex ovo stereomicrophotographs. The angiogenic response was characterized by quantification of blood vessels convergence, H&E staining and immunohistochemistry for SNAlectin. RESULTS & DISCUSSION: The analysis of blood vessels convergence suggests that both SF and S/E scaffolds stimulated an angiogenic response as supported by the significantly higher number of blood vessels converging to the implanted scaffolds, when compared to GSp. A small increase on the number of blood vessels converging towards the S/E scaffolds was noticed, which may result from the incorporation of elastin on SF bioink. The histological characterization has shown endothelial cells infiltration and a massive CAM tissue infiltration/ingrowth through the porous structure of both SF and S/E scaffolds.