SPOCK2 controls the proliferation and function of immature pancreatic β-cells through MMP2.

Human pluripotent stem cell-derived β-cells (SC-β-cells) represent an alternative cell source for transplantation in diabetic patients. While mitogens could in theory be employed to expand β-cells, adult β-cells very rarely replicate. Conversely, newly formed β-cells, including SC-β-cells, display higher proliferative capacity and distinct transcriptional and functional profiles. Through bidirectional expression modulation and single-cell RNA-seq, we identified SPOCK2, an ECM protein, as inhibitor of immature β-cell proliferation. Human β-cells lacking SPOCK2 demonstrated elevated MMP2 expression and activity, leading to β-integrin-FAK-c-JUN pathway activation. Treatment with MMP2 protein resulted in pronounced short- and long-term SC-β-cell expansion, significantly, increasing glucose-stimulated insulin secretion in vitro and in vivo. This suggests that SPOCK2 mediates fetal β-cell proliferation and maturation. Together, we identified molecular mechanism that specifically regulates SC-β-cell proliferation and function, highlighting a unique signaling milieu of SC-β-cells with promising potential for robust derivation of fully functional cells for transplantation.