Tissue Specific Extracellular Matrix Extract Promotes Salivary Gland Organoid Formation with Human Salivary Progenitors

Hypofunction of the salivary glands (SGs) has several detrimental effects. Several approaches can be used to restore the function of damaged SGs, such as tissue engineering based on stem cells and biomaterials. Among these, three dimensional (3D) culture without biomaterials (termed organoids) can recapitulate the characteristics of the native organ in vivo. However, despite the substantial progress made, most organoids which are formed from stem cells or cell aggregates still lack a specific tissue niche. We hypothesized that tissue specific ECM proteins are required for formation and maintenance of functional organoids. Thus, we evaluate the effect of human tissue specific ECM extracts on the formation of functional SG organoids containing human SG epithelial and mesenchymal cells. We prepared human salivary gland ECM (hSG-ECM) with a growth factor-enriched supplement and the prepared hSG-ECM was introdeced in a uniform high-throughput 3D platform. First, we determined the optimum culture conditions; organoids comprising 5,000 cells at a mesenchymal: epithelial cell ratio of 1:9 exhibited a low frequency of apoptosis, high proliferation capacity, and a structure resembling that of SGs. Introduction of hSG-ECM extract with proper concentration resulted in maintenance of the stem cell niche and promotion of stem cell differentiation. Moreover, treatment of the organoids with decellularized supplements increased their sensitivity to neurotransmitters. In conclusion, we developed functional human SG organoids using salivary progenitors and ECM extract. The SG organoids have potential for SG tissue repair, drug development, and disease modeling.