Abstract
Purpose :
Hydrogels made from extracellular matrix (ECM) provide excellent 3D scaffolds enabling quick and ethically sound research of therapeutic treatments. However, ECM hydrogels derived from the lacrimal gland (LG) are not suitable for bioprinting due to unbeneficial biomechanical properties. To combine the benefits of bioprinting and ECM hydrogels in a 3D LG in vitro model, we generated a viable bioink derived from decellularized porcine LG enhanced with the biologically inert alginate.
Methods :
The bioink (LGink) is composed of 5 mg/ml porcine LG ECM solution and 2% (w/v) alginate. 2% alginate was used as control. Structures were printed via freeform reversible embedding of suspended hydrogels. In oscillatory rheometry, flow curves of LGink and 2% alginate solutions were obtained (n=3) and storage and loss moduli of printed structures calculated (n=3). Young’s moduli of printed structures as well as native LG were calculated in unconfined compression test (n=6). As homogenous distribution of cells in the bioink is crucial for precise spatial deposition in complex bioprinting approaches, cell sedimentation in LGink, 2% alginate solution and medium was assessed after 90 min. Viability assays of porcine LG epithelial cells were performed on cell laden printed specimens of LGink and 2% alginate (n=3) at 3 and 7 days post printing.
Results :
Young’s Modulus of printed LGink structures (E=3.12±1.5 kPa) was not significantly different from 2% alginate hydrogels (E=4.38±2.0 kPa) or porcine LG tissue (E=5.32±1.2 kPa, p=0.22). LGink showed ideal shear thinning properties, with similar viscosity to 2% alginate and water at high shear rates. Shear strain crossover, indicating structural failure of LGink structures, was at 35.7% strain compared to 22.5% for 2% alginate. Further, LGink sustained a homogenous distribution of cells compared to 2% alginate where cell density is reduced to 37%. In medium, no cells remained suspended. At last, lacrimal epithelial cells printed in LGink showed a 1.75 to 1.89 fold higher cell viability post printing compared to 2% alginate.
Conclusions :
The addition of alginate to LG hydrogel enables ion based crosslinking leading to more robust structures. Shear thinning properties are introduced and cell sedimentation is prevented while maintaining superior cell viability. Concluding, LGink represents an approach to transfer the benefits of ECM hydrogels to 3D bioprinting.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.