Purpose

Within biofabrication, the recreation of spatially distributed vasculature is paramount, as vascular capillary ingrowth into avascular tissues can lead to tissue matrix alterations, and subsequent pathology. Multi-material 3D bioprinting is a potentially tool to recreate complex anisotropic tissue features, although to date, building complex constructs with stable vascularized and non-vascularized regions remains a challenge.

Methods and Materials

We developed a pro- and anti-angiogenic bioink by the supplementation of type I collagen (col-1) microfibers (MFs), and decellularized cartilage-derived (CdECM) MFs respectively, to an endothelial cell (EC)-laden fibrin-based bioink. By extrusion-based bioprinting, the bioinks were deposited into an anatomical meniscus shaped construct with a biomimetic outer vascularized zone containing ECs and mesenchymal stromal cells (MSCs), and an inner fibrocartilagenous zone with meniscus progenitor cells (MPCs), cultured for 14 days. To co-facilitate both microvessel formation and MPC-derived matrix formation, we tested different compositions of chondrogenic and endothelial cell culture medium formulations.

Results

The supplementation of CdECM MFs to the EC-laden fibrin-based bioinks lead to a reduction of the total microvessel length of 29%, as compared to supplementation of pro-angiogenic col-1 MFs (Figure 1). After 3D bioprinting of the zonal meniscus construct, the vascular network was confined in the outer zone (Figure 2). The co-culture of ECs and MPCs was succesful by switching from endothelial cell culture medium (EGM-2) to 10 or 25% v/v chondrogenic differentiation medium in EGM-2 medium at day 7, resulting in both EC-derived vascular networks and MPC type I collagen deposition.

Figure 1

Figure 2

Conclusion

Here, we present two bioinks that facilitate and inhibit vascular formation, by supplementation of col-1 or CdECM MFs, which were bioprinted in a biomimetic meniscus construct. This provides new strategies for grafts development of partially avascular tissues, and applications including in vitro models of vascular-to-avascular tissue interfaces, cancer progression, and for testing anti-angiogenic therapies.