A major challenge during the engineering of voluminous bone tissues is to maintain cell viability in the central regions of the construct. In vitro prevascularization of bone substitutes relying on endothelial cell bioprinting has the potential to resolve this issue and to replicate the native bone microvasculature. Laser-assisted bioprinting (LAB) commonly uses biological layers of hydrogel, called ‘biopapers’, to support patterns of printed cells and constitute the basic units of the construct. The self-assembly approach of tissue engineering allows the production of biomimetic cell-derived bone extracellular matrix including living cells. We hypothesized that self-assembled osseous sheets can serve as living biopapers to support the LAB of human endothelial cells and thus guide tubule-like structure formation. Human umbilical vein endothelial cells were bioprinted on the surface of the biopapers following a predefined pattern of lines. The osseous biopapers showed relevant matrix mineralization and pro-angiogenic hallmarks. Our results revealed that formation of tubule-like structures was favored when the cellular orientation within the biopaper was parallel to the printed lines. Altogether, we validated that human osseous cell sheets can be used as biopapers for LAB, allowing the production of human prevascularized cell-based osseous constructs that can be relevant for autologous bone repair applications.

Cardiovascular diseases are the leading cause of mortality in the world and encompass several important pathologies, including atherosclerosis. In the cases of severe vessel occlusion, surgical intervention using bypass grafts may be required. Synthetic vascular grafts provide poor patency for small-diameter applications (< 6 mm) but are widely used for hemodialysis access and, with success, larger vessel repairs. In very small vessels, such as coronary arteries, synthetics outcomes are unacceptable, leading to the exclusive use of autologous (native) vessels despite their limited availability and, sometimes, quality. Consequently, there is a clear clinical need for a small-diameter vascular graft that can provide outcomes similar to native vessels. Many tissue-engineering approaches have been developed to offer native-like tissues with the appropriate mechanical and biological properties in order to overcome the limitations of synthetic and autologous grafts. This review overviews current scaffold-based and scaffold-free approaches developed to biofabricate tissue-engineered vascular grafts (TEVGs) with an introduction to the biological textile approaches. Indeed, these assembly methods show a reduced production time compared to processes that require long bioreactor-based maturation steps. Another advantage of the textile-inspired approaches is that they can provide better directional and regional control of the TEVG mechanical properties.

We have created entirely biological tissue-engineered vascular grafts (TEVGs) using sheets of cell-assembled extracellular matrix (CAM) produced by human fibroblasts in vitro. A large animal TEVG would allow long-term pre-clinical studies in a clinically relevant setting (graft size and allogeneic setting). Therefore, canine, porcine, ovine, and human skin fibroblasts were compared for their ability to form CAM sheets. Serum sourcing greatly influenced CAM production in a species-dependent manner. Ovine cells produced the most homogenous and strongest animal CAM sheets but remained ≈3-fold weaker than human sheets despite variations of serum, ascorbate, insulin, or growth factor supplementations. Key differences in cell growth dynamics, tissue development, and tissue architecture and composition were observed between human and ovine. This study demonstrates critical species-to-species differences in fibroblast behavior and how they pose a challenge when attempting to substitute animal cells for human cells during the development of tissue-engineered constructs that require long-term cultures.

Several tissue engineering approaches are based on the ability of mesenchymal cells to endogenously synthesize an extracellular matrix (ECM)in vitro, which can be seen as a form of biomaterial.