Three-in-one customized bioink for islet organoid: GelMA/ECM/PRP orchestrate pro-angiogenic and immunoregulatory function

Islet organoids open up new strategies for diabetes treatment and pancreatic tissue engineering. Digital light processing (DLP) bioprinting has been extensively applied to the construction of organoids due to its ability to provide precisely patterned scaffolds with fast printing time while specific tailored bioink is indispensable for islet organoid. Customized bioinks that meet different needs were created and frequently applied based on gelatin methacryloyl (GelMA) mixed with other ingredients. Decellularized extracellular matrix (ECM) retains many organic specific structural and functional components and is widespread utilized to reconstruct the native niche like environment. However, considerable cytokines and growth factors were inevitably lost during the decellularized process, while platelet rich plasma (PRP) contains a string of growth factors which often exerted pro-angiogenic role. Therefore, a customized specific bioink for constructing islet organoid based on GelMA, pancreatic ECM and PRP was prepared in our research. In vitro, tube formation assay, CD31 immunofluorescence and relative mRNA expression of vascular genes indicated that the bioink with distinctively promote angio-genesis potential. Macrophages polarization was also conducted, which exhibited superior expression of CD206 (M2 marker) and inferior expression of iNOS (M1 marker). 3D printed organoids maintain the activity of mouse islet beta-cells (MIN6) with enhanced glucose sensitivity. In vivo, the results of CD31, CD206 and iNOS immuno-fluorescence were consistent with that in vitro. In summary, we prepared and characterized specific custom-made bioink with orchestrating immune-regulation response indicated by abundant M2-polarized macro-phages, attenuated inflammation, and promoted angiogenesis, which provides an underlying bioink for the fabrication of 3D printed islet organoid.