Figure 4.

Chorioallantoic membrane assay is a suitable model for investigating angiogenesis in tissue-engineered grafts. Extensive, rapid vascular ingrowth is seen in both PCL and cell-laden hydrogel structure after the 9-day assay period. Ex ovo CAM assay experiments enabled direct comparison of heparinized PCL scaffolds with untreated controls and validated the beneficial properties of heparinization for enhanced vascular ingrowth ((a–c) arrow indicates eye of chicken embryo). In ovo CAM assay experiments were used for investigation of 3D-bioprinted INS-1-laden droplets ((d–l) arrow indicates xenotransplant). Vascular structures (arrows) penetrated into the scaffold (g–l). (g) Anti-insulin immunohistochemical staining of CAM assay explant. (h) H&E staining of CAM assay explant. (i–l) Anti-insulin (brown) and anti-CD31 (red) immunohistochemical double-staining of CAM assay explant. Rapid vascularization maintained viability and function of pseudoislets. Peri- and intra-insular (asterisks) vessels were detected (g–l). Scale bar (a and d) 10 mm, (b, c, e, and f) 2 mm, (j) 100 µm, (g, h, k, and l) 50 µm, (i) 20 µm.