Table 2 Issues to be addressed
Area
Focus for future research
Bioprinter technology
Compatible with physiologically relevant materials and cells
Increased resolution and speed
Scale up for commercial applications
Combining bioprinter technologies to overcome technical challenges
Biomaterials
Complex combinations or gradients to achieve desired functional, mechanical and supportive properties
Modified or designed to facilitate bioprinter deposition, while also exhibiting desired postprinting properties
Use of decellularized tissue-specific ECM scaffolds to study ECM compositions, and/or as printable material
Cell sources
Well-characterized and reproducible source of cells required
Combinations of cell phenotypes with specific functions
Greater understanding required of the heterogeneous cell types present in the tissues
Direct control over cell proliferation and differentiation with small molecules or other factors
Vascularization
Well-developed vascular tree required for large tissues
May have to be engineered in the bioprinted construct
Capillaries and microvessels required for tissue perfusion
Suitable mechanical properties for physiological pressures and for surgical connection
Innervation
Innervation is required for normal tissue function
May be inducible after transplantation using pharmacologic or growth factor signaling
Simulation before transplantation could be achieved using bioreactors
Maturation
Time required for assembly and maturation
Bioreactors may be used to maintain tissues in vitro
Provide maturation factors as well as physiological stressors
Potential for preimplantation testing of constructs