Development and characterization of a decellularized lung ECM-based bioink for bioprinting and fabricating a lung model

The construction of three-dimensional (3D) in vitro lung tissue models mimicking the physiological structure of the native lung poses a huge challenge in tissue engineering. While advances in bioprinting technology has made fabrication of 3D lung models feasible, the bioinks and printed constructs often fall short in achieving desired mechanical and biological properties. Toward this, we aimed to develop a novel bioink and use it to print and characterize in vitro 3D lung models with living cells. We generated porcine lung extracellular matrix (LdECM) which was then strategically combined with other hydrogels – alginate, carboxymethylcellulose (CMC), and collagen, to synthesize novel bioinks. The printability, mechanical and biological properties of the synthesized bioinks was characterized. We also characterized the rheological properties and identified the bioink composition – 3 % w/v alginate, 0.5 % w/v CMC, 0.5 mg/mL collagen Type 1 and 1 % v/v porcine LdECM was appropriate for bioprinting. To fabricate 3D lung models, we strategically designed and printed constructs featuring spatially organized patterns of MRC-5 human lung fibroblasts and A549-ACE2 human lung epithelial cells along with a cup-shaped structure to confine epithelial cells. Our results demonstrated that the bioinks with viscosities between 60 and 90 Pa.s were appropriate, which resulted in high printing resolution of cell-laden constructs and excellent cell viability. The bioprinted lung constructs also exhibited an elastic modulus of 2–4 kPa comparable to the stiffness of native lung tissues. Our findings establish a foundation for developing lung-specific 3D bioprinted models to address the growing global prevalence of respiratory diseases and for advancing preclinical therapeutic testing.